Endre søk
Begrens søket
1234567 1 - 50 of 1457
RefereraExporteraLink til resultatlisten
Permanent link
Referera
Referensformat
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Annet format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annet språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf
Treff pr side
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sortering
  • Standard (Relevans)
  • Forfatter A-Ø
  • Forfatter Ø-A
  • Tittel A-Ø
  • Tittel Ø-A
  • Type publikasjon A-Ø
  • Type publikasjon Ø-A
  • Eldste først
  • Nyeste først
  • Skapad (Eldste først)
  • Skapad (Nyeste først)
  • Senast uppdaterad (Eldste først)
  • Senast uppdaterad (Nyeste først)
  • Standard (Relevans)
  • Forfatter A-Ø
  • Forfatter Ø-A
  • Tittel A-Ø
  • Tittel Ø-A
  • Type publikasjon A-Ø
  • Type publikasjon Ø-A
  • Eldste først
  • Nyeste først
  • Skapad (Eldste først)
  • Skapad (Nyeste først)
  • Senast uppdaterad (Eldste først)
  • Senast uppdaterad (Nyeste først)
Merk
Maxantalet träffar du kan exportera från sökgränssnittet är 250. Vid större uttag använd dig av utsökningar.
  • 1.
    Abadir Guirgis, Georg
    Linköpings Universitet.
    Ecodriving på SJ: förarperspektiv på tekniska hjälpmedel för beslutsfattande och utbildning i Ecodriving2013Rapport (Annet vitenskapelig)
    Abstract [sv]

    Trots att samtliga resor med SJs tåg i Sverige är märkta med Bra Miljöval skärps kraven på minskade utsläpp och energianvändning efter hand, varför SJ ständigt måste utveckla sin miljöprofil. På SJ har man därför arbetat fram en utbildning i energieffektiv körning (Ecodriving) samt låtit vissa av sina förare använda ett tekniskt hjälpmedel som stödjer detta, för att påvisa möjligheten till energibesparingar. Denna rapport tar upp två studier vilka är SJs försöksverksamhet inklusive en kritisk granskning av denna samt en kompletterande studie i form av observationer av utbildning i Ecodriving och intervjuer med förare. Resultaten av SJs försöksverksamhet är värdefulla och talar för att energibesparingar är genomförbara. Samtidigt så finns det en hel del osäkerhet i de energimätningsdata som samlats in varför det är svårt att dra några definitiva slutsatser. Resultatet av intervjuerna med förarna talar för att det finns en hel del oklarheter kring vilka risker och konsekvenser ett framtida införande av det tekniska hjälpmedlet för Ecodriving faktiskt innebär. Sammantaget finns anledning att genomföra fortsatta studier av hur man på bästa sätt kan införa energieffektiv körning av spårtrafik i sin helhet.

  • 2.
    Abbasi, Saeed
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Maskinelement.
    Non-exhaust Nano particle emission in Rail traffic2010Konferansepaper (Fagfellevurdert)
  • 3.
    Abbasi, Saeed
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Maskinelement.
    Jansson, Anders
    Sellgren, Ulf
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Maskinelement.
    Olofsson, Ulf
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Maskinelement.
    Particle emissions from rail traffic: a literature review2013Inngår i: Critical reviews in environmental science and technology, ISSN 1064-3389, E-ISSN 1547-6537, Vol. 43, nr 23, 2211-2244 s.Artikkel, forskningsoversikt (Fagfellevurdert)
    Abstract [en]

    Particle emissions are a drawback of rail transport. This work is a comprehensive presentation of recent research into particle emissions from rail vehicles. Both exhaust and non-exhaust particle emissions are considered when examining particle characteristics such as  PM10, and PM2.5 concentration levels, size, morphology, composition, as well as adverse health effects, current legislation, and available and proposed solutions for reducing such emissions. High concentration levels in enclosed rail traffic environments are reported and some toxic effects of the particles. We find that only a few limited studies have examined the adverse health effects of non-exhaust particle emissions and that no relevant legislation exists. Thus further research in this area is warranted.

  • 4.
    Abbasi, Saeed
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Maskinelement.
    Olofsson, Ulf
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Maskinelement.
    Sellgren, Ulf
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Maskinelement.
    Lack of applicable criteria in non-exhaust emission legislation: AWPER index a practical solution2011Konferansepaper (Fagfellevurdert)
  • 5.
    Abbasi, Saeed
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Maskinelement.
    Olofsson, Ulf
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Maskinelement.
    Sellgren, Ulf
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Maskinelement.
    Olander, Lars
    Larsson, christina
    A field investigation of the size, morphology and chemical composition of airborne particles in rail transport2010Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The health effects of inhalable airborne particles are well documented. In the European Union the European Council mandates that the level of airborne particles with a diameter smaller than 10 µm (PM10) must not exceed an annual average of 40 µg/m3. Examples of possible sources from rail transport are mechanical brakes, wheel rail contact, current collectors, ballast, sleepers and masonry structures. In this regard, a series of field tests have been conducted on a regular Swedish track using a regional train instrumented with: particle measurement devices, temperature sensors in brake pads and sensors to measure the magnitude of train speed and a GPS.

    Two sampling points for airborne particles were designated in the train under frame. One of the sampling points was near a pad to rotor disc brake contact and a second global sampling point was chosen under the frame, but not near a mechanical brake or the wheel-rail contact. The first one was highly influenced by brake pad wear debris and the other one was influenced by all of the brake pads, wheel and rail wear debris as well as re-suspension. In each sampling points, three tubes were linked to three particle measurement devices. Two sets of Ptrak, Dustrak and Grimm devices were used. The Ptrak 8525 was an optical particle measurement device which could measure particle diameter in the size interval of 20 nm up to 1 micrometer. The Dustrak was used to measure particle mass concentration. The Grimm 1.109 was an aerosol spectrometer which counted number of particles from 0.25 micrometer to 32 micrometer in 31 intervals. These two Grimm devices were equipped with Millipore filters in the devices outlets to capture particles for further studies on morphology and matter of particles.

    The total number and size distribution of the particles for these two sampling points were registered and evaluated in different situations such as activating and deactivating electrical brake or train curve negotiating.

    During braking, three peaks of 250 nm, 350 nm and 600 nm in diameter, with the 350 nm peak dominating were identified in the fine particle region. In the coarse particle region, a peak of around 3-6 µm in diameter was discovered. The brake pad temperature effects on particle size distribution were also investigated and the results showed that the peak around 250 nm increased. Furthermore, the activation of electrical braking significantly reduced the number of airborne particles.

    A SEM was used to capture the images from collected particles on filters. Furthermore, an ICP-Ms method was used to investigate the elemental contents of the particulates on the filter.  In this case the main contribution belonged to Fe, Si, Al, Ca, Cu, Zn. The higher amount of some elements weights such as calcium, silicon, sodium and aluminum in the global sampling point filters revealed that ballast and concrete sleepers were the main sources for these particles although some of them originated from rail, wheel, brake disc and brake pad as well.

  • 6.
    Abou-Senna, Hatem
    et al.
    University of Central Florida, Orlando.
    Radwan, Essam
    University of Central Florida, Orlando.
    Mohamed, Ayman
    University of Central Florida, Orlando.
    A methodology to quantify pedestrian crash rates against statewide averages for roadways and intersections2016Konferansepaper (Fagfellevurdert)
    Abstract [en]

    To date there are no clear or uniform standards for a method to measure pedestrian crash rates and compare it against a statewide average. In this paper, a novel methodology to measure pedestrian crash rates along roadways and intersections were quantified. The main objective is to identify critical pedestrian crash locations that are operating above its corresponding statewide average.  It was crucial to address the pedestrian-vehicular conflict as the State of Florida currently tops the list in the “Dangerous by Design” report as having the highest four pedestrian incident locations in the Country. The main challenge was to identify a practical and correct exposure measure. In most cases, the exposure measure is either unavailable or can be obtained at a greater cost. The methods and procedures explained in this paper are considered detailed, practical and provide a broad depiction of the main factors that directly contribute to pedestrian crashes. The main parameters used in calculating pedestrian crash rates along roadways included functional classification, number of lanes, area type, AADT and the total length of the roadway category. Conversely, main parameters for computing pedestrian crash rates for intersections included daily pedestrian volumes, distance crossed and the AADT in addition to the number of pedestrian crashes either along the studied roadways or intersections. The pilot studies conducted for the roadways and intersections revealed several critical safety locations within District 5 when compared to the developed statewide average rates which required further investigation to identify main causes and emphasize mitigation improvements.

  • 7.
    Adolph, Thorsten
    et al.
    Federal Highway Research Institute.
    Eggers, Andre
    Federal Highway Research Institute.
    Thomson, Robert William
    Statens väg- och transportforskningsinstitut, Trafik och trafikant,TRAF, Trafiksäkerhet, samhälle och trafikant, TST.
    Mizuno, Koji
    Nagoya University.
    Comparison of the dummy response in two different restraint system crash tests2014Inngår i: 2014 IRCOBI Conference Proceedings - International Research Council on the Biomechanics of Injury, 2014, 545-561 s.Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In the European Project FIMCAR, a proposal for a frontal impact test configuration was developed which included an additional full width deformable barrier (FWDB) test. Motivation for the deformable element was partly to measure structural forces as well as to produce a severe crash pulse different from that in the offset test. The objective of this study was to analyse the safety performance of vehicles:

    • in the full width rigid barrier test (FWRB) and
    • in the full width deformable barrier test (FWDB)

    In total, 12 vehicles were crashed in both configurations. Comparison of these tests to real world accident data was used to identify the crash barrier most representative of real world crashes. For all vehicles, the airbag visible times were later in the FWDB configuration. This was attributed to the attenuation of the initial acceleration peak, observed in FWRB tests, by the addition of the deformable element. These findings were in alignment with airbag triggering times seen in real world crash data. Also, the dummy loadings were slightly worse in FWDB compared to FWRB tests, which is possibly linked to the airbag firing and a more realistic loading of the vehicle crash structures in the FWDB configuration. Evaluations of the lower extremities have shown a general increasing of the tibia index with the crash pulse severity.

  • 8.
    Afshari, Davood
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Lättkonstruktioner.
    Mechanical Properties of Resistance Spot Welds in Lightweight Applications2013Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    This licentiate thesis is concerned with residual stresses in aluminum alloy 6061-T6 resistance spot welded joint. Several topics related to mechanical strength of welded structures are treated such as; nugget size and microhardness and microstructures of weld zone and their influence on mechanical strength of welded structure, failure load measurement using tensile-shear test, resistance spot welding simulation, residual stress measurement by X-ray diffraction method and analysis effect of welding parameters on the mechanical strength and the residual stresses.

    To investigate the effect of resistance spot weld parameters on mechanical strength of welded structures, various welding parameters e.g. welding current, welding time and electrode force are selected to produce welded joints with different quality. According to the failure mode, the empirical equation was used to prediction of failure load base on nugget size and hardness of failure line. Microstructure study has been carried out to investigate microstructural changes in the welded joints. Microhardness tests are done to find hardness profiles due to microstructural changes and determine the minimum hardness.

    In addition, an electro-thermal-structural coupled finite element model and X-ray diffraction residual stress measurement have been utilized to analyze residual stresses distribution in weld zone. The electrical and thermal contact conductance, as mandatory factors are applied in contact area between electrode-workpiece and workpiece-workpiece to resolve the complexity of the finite element model. The physical and mechanical properties of the material are defined as thermal-dependent in order to improve the accuracy of the model. Furthermore, the electrodes are removed after holding cycle using the birth and death elements method. Moreover, the effect of welding parameters on maximum residual stress is investigated and a regression model is proposed to predict maximum tensile residual stresses in terms of welding parameters.

    The results obtained from the finite element analysis have been used to build up two back-propagation artificial neural network models for the residual stresses and the nugget size prediction. The results revealed that the neural network models created in this study can accurately predict the nugget size and the residual stresses produced in resistance spot weld. Using a combination of these two developed models, the nugget size and the residual stresses can be predicted in terms of spot weld parameters with high speed and accuracy.

  • 9.
    Afshari, Davood
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg. Iran University of Science and Technology, Iran.
    Sedighi, M.
    Karimi, M. R.
    Barsoum, Zuheir
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg.
    Prediction of residual stresses in resistance spot weld2016Inngår i: Aircraft Engineering and Aerospace Technology, ISSN 1748-8842, Vol. 88, nr 4, 492-497 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Purpose - The purpose of this paper is to predict residual stresses in resistance spot weld of 2 mm thick aluminum 6061-T6 sheets. The joint use of finite element analysis and artificial neural networks can eliminate the high costs of residual stresses measuring tests and significantly shorten the time it takes to arrive at a solution. Design/methodology/approach - Finite element method and artificial neural network have been used to predict the residual stresses. Different spot welding parameters such as the welding current, the welding time and the electrode force have been used for the simulation purposes in a thermal-electrical-structural coupled finite element model. To validate the numerical results, a series of experiments have been performed, and residual stresses have been measured. The results obtained from the finite element analysis have been used to build up a back-propagation artificial neural network model for residual stresses prediction. Findings - The results revealed that the neural network model created in this study can accurately predict residual stresses produced in resistance spot weld. Using a combination of these two developed models, the residual stresses can be predicted in terms of spot weld parameters with high speed and accuracy. Practical implications - The paper includes implication for aircraft and automobile industries to predict residual stresses. Residual stresses can lower the strength and fatigue life of the spot-welded joints and determine the performance quality of the structure. Originality/value - This paper presents an approach to reduce the high costs and long times of residual stresses measuring tests.

  • 10.
    Afshari, Davood
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Lättkonstruktioner.
    Sedighi, Mohammd
    Iran Univ Sci & Technol, Tehran, Iran.
    Barsoum, Zuhier
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Lättkonstruktioner.
    Peng, Ru Lin
    Linkoping Tech Univ, Linkoping, Sweden .
    An approach in prediction of failure in resistance spot welded aluminum 6061-T6 under quasi-static tensile test2012Inngår i: Proceedings of the Institution of mechanical engineers. Part B, journal of engineering manufacture, ISSN 0954-4054, Vol. 226, nr B6, 1026-1032 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The aim of this article is to predict the failure load in resistance spot welded aluminum 6061-T6 sheets with 2mm thickness under quasi-static tensile test. Various welding parameters, e. g. welding current, welding time and electrode force are selected to produce welded joints with different quality. The results show that for all the samples in this study only interfacial failure mode was observed in tensile-shear test and no pull-out mode was observed. According to the failure mode, an empirical equation was used for the prediction of failure load based on nugget size and hardness of failure line. Microstructure study has been carried out to investigate microstructural changes in the welded joints. For determination of the minimum hardness, microhardness tests have been carried out to find hardness profiles. The minimum hardness value was observed for a thin layer around the nugget with large and coarse grains. The results show that by using the presented empirical equation, the failure can be predicted with a good agreement only by measuring nugget size.

  • 11.
    Afshari, Davood
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Lättkonstruktioner.
    Sedighi, Mohammd
    Iran Univ Sci & Technol, Tehran, Iran.
    Karimi, M. R.
    Barsoum, Zuhier
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Lättkonstruktioner.
    On Residual Stresses in Resistance Spot-Welded Aluminum Alloy 6061-T6: Experimental and Numerical Analysis2013Inngår i: Journal of materials engineering and performance (Print), ISSN 1059-9495, E-ISSN 1544-1024, Vol. 22, nr 12, 3612-3619 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this study, an electro-thermal-structural-coupled finite element (FE) model and x-ray diffraction residual stress measurements have been utilized to analyze distribution of residual stresses in an aluminum alloy 6061-T6 resistance spot-welded joint with 2-mm-thickness sheet. Increasing the aluminum sheet thickness to more than 1 mm leads to creating difficulty in spot-welding process and increases the complexity of the FE model. The electrical and thermal contact conductances, as mandatory factors are applied in contact areas of electrode-workpiece and workpiece-workpiece to resolve the complexity of the FE model. The physical and mechanical properties of the material are defined as thermal dependent to improve the accuracy of the model. Furthermore, the electrodes are removed after the holding cycle using the birth-and-death elements method. The results have a good agreement with experimental data obtained from x-ray diffraction residual stress measurements. However, the highest internal tensile residual stress occurs in the center of the nugget zone and decreases toward nugget edge; surface residual stress increases toward the edge of the welding zone and afterward, the area decreases slightly.

  • 12.
    Afshari, Davood
    et al.
    School of Mechanical Engineering, Iran University of Science and Technology, Tehran, Iran .
    Sedighi, Mohammd
    Iran Univ Sci & Technol, Tehran, Iran.
    Karimi, M. R.
    Barsoum, Zuhier
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Lättkonstruktioner.
    Prediction of the nugget size in resistance spot welding with a combination of a finite-element analysis and an artificial neural network2014Inngår i: Materiali in tehnologije, ISSN 1580-2949, Vol. 48, nr 1, 33-38 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The goal of this investigation is to predict the nugget size for a resistance spot weld of thick aluminum 6061-T6 sheets 2 mm. The quality and strength of spot welds determine the integrity of the structure, which depends thoroughly on the nugget size. In this study, the finite-element method and artificial neural network were used to predict the nugget size. Different spot welding parameters such as the welding current and the welding time were selected to be used for a coupled, thermal-electrical-structural finite-element model. In order to validate the numerical results a series of experiments were carried out and the nugget sizes were measured. The results obtained with the finite-element analysis were used to build up a back-propagation, artificial-neural-network model for the nugget-size prediction. The results revealed that a combination of these two developed models can accurately and rapidly predict the nugget size for a resistance spot weld.

  • 13.
    Agea, Andrés
    et al.
    Högskolan i Skövde, Institutionen för teknik och samhälle.
    Millán, Iván
    Högskolan i Skövde, Institutionen för teknik och samhälle.
    Range Extender for the Renault Fluence Z.E.: Choice of the engine and design of the structural support.2012Independent thesis Basic level (degree of Bachelor), 15 poäng / 22,5 hpOppgave
    Abstract [en]

    Electric cars have appeared as an alternative to the big pollution caused by internal combustion engine cars. However, electric cars as the Renault Fluence Z.E. are not very sold in the market because of their small range of autonomy. To make this car an attractive option, it is necessary to add a range extender that extends its autonomy. This range extender is based in the addition of a small internal combustion engine to be attached only when the electric autonomy cannot fulfill the trip. A range extender is chosen by means of a comparison between different electric engines sold in the market. By means of a classification tree, the different places of the car where to mount it are compared and the most appropriate is chosen. By using Solidworks, a structure to support the engine and attach it to the car is designed. The result is a Range Extender device to mount in the hitch hook of the Renault Fluence Z.E. that provides an autonomy of around 665 km. This supposes a good solution for the owner of the Renault Fluence Z.E. who needs to cover trips of more than 180 km, the electric autonomy of this car.

  • 14.
    Aghaali, Habib
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Förbränningsmotorteknik.
    Exhaust Heat Utilisation and Losses in Internal Combustion Engines with Focus on the Gas Exchange System2014Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Exhaust gas energy recovery should be considered in improving fuel economy of internal combustion engines. A large portion of fuel energy is wasted through the exhaust of internal combustion engines. Turbocharger and turbocompound can, however, recover part of this wasted heat. The energy recovery depends on the efficiency and mass flow of the turbine(s) as well as the exhaust gas state and properties such as pressure, temperature and specific heat capacity. The exhaust gas pressure is the principal parameter which is required for the turbine energy recovery, but higher exhaust back-pressures on the engines create higher pumping losses. This is in addition to the heat losses in the turbochargers what makes any measurement and simulation of the engines more complex.

    This thesis consists of two major parts. First of all, the importance of heat losses in turbochargers has been shown theoretically and experimentally with the aim of including heat transfer of the turbochargers in engine simulations. Secondly, different concepts have been examined to extract exhaust heat energy including turbocompounding and divided exhaust period (DEP) with the aim of improved exhaust heat utilisation and reduced pumping losses.

    In the study of heat transfer in turbochargers, the turbocharged engine simulation was improved by including heat transfer of the turbocharger in the simulation. Next, the heat transfer modelling of the turbochargers was improved by introducing a new method for convection heat transfer calculation with the support of on-engine turbocharger measurements under different heat transfer conditions. Then, two different turbocharger performance maps were assessed concerning the heat transfer conditions in the engine simulation. Finally, the temperatures of turbocharger’s surfaces were predicted according to the measurements under different heat transfer conditions and their effects are studied on the turbocharger performance. The present study shows that the heat transfer in the turbochargers is very crucial to take into account in the engine simulations, especially in transient operations.

    In the study of exhaust heat utilisation, important parameters concerning turbine and gas exchange system that can influence the waste heat recovery were discussed. In addition to exhaust back-pressure, turbine speed and turbine efficiency, the role of the air-fuel equivalence ratio was demonstrated in details, because lower air-fuel equivalence ratio in a Diesel engine can provide higher exhaust gas temperature. The results of this study indicate that turbocompound engine efficiency is relatively insensitive to the air-fuel equivalence ratio.

    To decrease the influence of the increased exhaust back-pressure of a turbocompound engine, a new architecture was developed by combining the turbocompound engine with DEP. The aim of this study was to utilise the earlier phase (blowdown) of the exhaust stroke in the turbine(s) and let the later phase (scavenging) of the exhaust stroke bypass the turbine(s). To decouple the blowdown phase from the scavenging phase, the exhaust flow was divided between two different exhaust manifolds with different valve timing.

    According to this study, this combination improves the fuel consumption in low engine speeds and deteriorates it at high engine speeds. This is mainly due to long duration of choked flow in the exhaust valves because this approach is using only one of the two exhaust valves on each cylinder at a time.

    Therefore, the effects of enlarged effective flow areas of the exhaust valves were studied. Two methods were used to enlarge the effective flow area i.e. increasing the diameters of the blowdown and scavenging valves by 4 mm; and modifying the valve lift curves of the exhaust valves to fast opening and closing. Both methods improved BSFC in the same order even though they were different in nature. Fast opening and closing of the exhaust valves required shorter blowdown duration and longer scavenging duration. The modified lift curves provided less pumping losses, less available energy into the turbine and larger amplitude of the pulsating flow through the turbine.

    In order for defining a set of important parameters that should be examined in experimental studies, a sensitivity analysis was performed on the turbocompound DEP engine in terms of break specific fuel consumption to different parameters concerning the gas exchange such as blowdown valve timing, scavenging valve timing, blowdown valve size, scavenging valve size, discharge coefficients of blowdown and scavenging ports, turbine efficiency, turbine size and power transmission efficiency.

    Finally, to overcome the restriction in the effective flow areas of the exhaust valves, DEP was implemented externally on the exhaust manifold instead of engine exhaust valves, which is called externally DEP (ExDEP). This innovative engine architecture, which benefits from supercharging, turbocharging and turbocompounding, has a great fuel-saving potential in almost all load points up to 4%.

  • 15.
    Aghaali, Habib
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.).
    On-Engine Turbocharger Performance Considering Heat Transfer2012Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Heat transfer plays an important role in affecting an on-engine turbocharger performance. However, it is normally not taken into account for turbocharged engine simulations.

    Generally, an engine simulation based on one-dimensional gas dynamics uses turbocharger performance maps which are measured without quantifying and qualifying the heat transfer, regardless of the fact that they are measured on the hot-flow or cold-flow gas-stand. Since heat transfer situations vary for on-engine turbochargers, the maps have to be shifted and corrected in the 1-D engine simulation, which mass and efficiency multipliers usually do for both the turbine and the compressor. The multipliers change the maps and are often different for every load point. Particularly, the efficiency multiplier is different for every heat transfer situation on the turbocharger. The heat transfer leads to a deviation from turbocharger performance maps, and increased complexity of the turbocharged engine simulation. Turbochargers operate under different heat transfer situations while they are installed on the engines.

    The main objectives of this thesis are:

    • heat transfer modeling of a turbocharger to quantify and qualify heat transfer mechanisms,
    • improving turbocharged engine simulation by including heat transfer in the turbocharger,
    • assessing the use of two different turbocharger performance maps concerning the heat transfer situation (cold-measured and hot-measured turbocharger performance maps) in the simulation of a measured turbocharged engine,
    • prediction of turbocharger walls’ temperatures and their effects on the turbocharger performance on different heat transfer situations.

    Experimental investigation has been performed on a water-oil-cooled turbocharger, which was installed on a 2-liter GDI engine for different load points of the engine and different heat transfer situations on the turbocharger by using insulators, an extra cooling fan, radiation shields and water-cooling settings. In addition, several thermocouples have been used on accessible surfaces of the turbocharger to calculate external heat transfers.

    Based on the heat transfer analysis of the turbocharger, the internal heat transfer from the bearing housing to the compressor significantly affects the compressor. However, the internal heat transfer from the turbine to the bearing housing and the external heat transfer of the turbine housing mainly influence the turbine. The external heat transfers of the compressor housing and the bearing housing, and the frictional power do not play an important role in the heat transfer analysis of the turbocharger.

    The effect of the extra cooling fan on the energy balance of the turbocharger is significant. However, the effect of the water is more significant on the external heat transfer of the bearing housing and the internal heat transfer from the bearing housing to the compressor. It seems the radiation shield between the turbine and the compressor has no significant effect on the energy balance of the turbocharger.

    The present study shows that the heat transfer in the turbocharger is very crucial to take into account in the engine simulations. This improves simulation predictability in terms of getting the compressor efficiency multiplier equal to one and turbine efficiency multiplier closer to one, and achieving turbine outlet temperature close to the measurement. Moreover, the compressor outlet temperature becomes equal to the measurement without correcting the map.

    The heat transfer situation during the measurement of the turbocharger performance influences the amount of simulated heat flow to the compressor. The heat transfer situation may be defined by the turbine inlet temperature, oil heat flux and water heat flux. However, the heat transfer situation on the turbine makes a difference on the required turbine efficiency multiplier, rather than the amount of turbine heat flow. It seems the turbine heat flow is a stronger function of available energy into the turbine. Of great interest is the fact that different heat situations on the turbocharger do not considerably influence the pressure ratio of the compressor. The turbine and compressor efficiencies are the most important parameters that are affected by that.

    The component temperatures of the turbocharger influence the working fluid temperatures. Additionally, the turbocharger wall temperatures are predictable from the experiment. This prediction enables increased precision in engine simulations for future works in transient operations.

  • 16.
    Aghaali, Habib
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Förbränningsmotorteknik.
    Ångstrom, Hans-Erik
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Förbränningsmotorteknik.
    Demonstration of Air-Fuel Ratio Role in One-Stage Turbocompound Diesel Engines2013Inngår i: SAE Technical Papers, 2013, Vol. 11Konferansepaper (Fagfellevurdert)
    Abstract [en]

    A large portion of fuel energy is wasted through the exhaust of internal combustion engines. Turbocompound can, however, recover part of this wasted heat. The energy recovery depends on the turbine efficiency and mass flow as well as the exhaust gas state and properties such as pressure, temperature and specific heat capacity.

    The main parameter influencing the turbocompound energy recovery is the exhaust gas pressure which leads to higher pumping loss of the engine and consequently lower engine crankshaft power. Each air-fuel equivalence ratio (λ) gives different engine power, exhaust gas temperature and pressure. Decreasing λ toward 1 in a Diesel engine results in higher exhaust gas temperatures of the engine.  λ can be varied by changing the intake air pressure or the amount of injected fuel which changes the available energy into the turbine. Thus, there is a compromise between gross engine power, created pumping power, recovered turbocompound power and consumed compressor power.

    In this study, the effects of different λ values and exhaust back-pressure have been investigated on the efficiency of a heavy-duty Diesel engine equipped with a single-stage electric turbocompounding. A one-dimensional gas dynamics model of a turbocharged engine was utilized that was validated against measurements at different load points. Two configurations of turbocompound engine were made. In one configuration an electric turbocharger was used and the amount of fuel was varied with constant intake air pressure. In another configuration the turbocharger turbine and compressor were disconnected to be able to control the turbine speed and the compressor speed independently; then the compressor pressure ratio was varied with constant engine fuelling and the exhaust back-pressure was optimized for each compressor pressure ratio.

    At each constant turbine efficiency there is a linear relation between the optimum exhaust back-pressure and ideally expanded cylinder pressure until bottom dead center with closed exhaust valves. There is an optimum λ for the turbocharged engine with regard to the fuel consumption. In the turbocompound engine, this will be moved to a richer λ that gives the best total specific fuel consumption; however, the results of this study indicates that turbocompound engine efficiency is relatively insensitive to the air-fuel ratio.

  • 17.
    Aghaali, Habib
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Förbränningsmotorteknik.
    Ångström, Hans-Erik
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Förbränningsmotorteknik.
    Effects of Effective Flow Areas of Exhaust Valves on a Turbocompound Diesel Engine Combined With Divided Exhaust Period2014Inngår i: Proceedings from the FISITA 2014 World Automotive Congress, 2014Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Research and /or Engineering Questions/Objective: Exhaust gas energy recovery in internal combustion engines is one of the key challenges in the future developments. The objective of this study is to reveal the fuel-saving potential of a turbocompound Diesel engine combined with divided exhaust period (DEP). The exhaust flow is provided for two different manifolds via separate valves, blowdown and scavenging, at different timings. The main challenge in this combination is choked flow through the exhaust valves due to the restricted effective flow areas. Therefore, the effects of enlarged effective flow areas of the exhaust valves are studied.

    Methodology: A commercial 1D gas dynamics code, GT-POWER, was used to simulate a turbocharged Diesel engine which was validated against measurements. Then the turbocharged engine model was modified to a turbocompound engine with DEP. Using statistical analysis in the simulation (design of experiment), the performance of this engine was studied at different sizes, lift curves and timings of the exhaust valves and turbine swallowing capacity.

    Results: In the paper the effects of the effective flow areas of the exhaust valves are presented on the break specific fuel consumption, pumping mean effective pressure and the turbine energy recovery by increasing the valve size and modifying valve lift curve to fast opening and closing. This has been done in a low engine speed and full load. The main finding is that the flow characteristics of the exhaust valves in the turbocompound DEP engine are very important for gaining the full efficiency benefit of the DEP concept.  The turbocompound DEP engine with modified valve lift shape of the exhaust valves could improve the overall brake specific fuel consumption by 3.44% in which 0.64% of the improvement is due to the valve lift curve. Modified valve lift curves contribute mainly in decreasing the period of choked flow through the exhaust valves.

    Limitations of this study: The simulations were not validated against measurements; however, the mechanical and geometrical limitations were tried to keep realistic when manipulating the valve flow area events.

    What does the paper offer that is new in the field in comparison to other works of the author: In addition to the novelty of the engine architecture that combines turbocompound with DEP, the statistical analysis and comparison presented in this paper is new especially with demonstrating the importance of crank angle coupled flow characteristics of the valves.

    Conclusion: To achieve full fuel-saving potential of turbocompound DEP engines, the flow characteristics of the exhaust valves must be considered. The effective flow areas of the exhaust valves play important roles in the choked flow through the valves, the pumping work and the brake specific fuel consumption of the engine.

  • 18.
    Aghaali, Habib
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Förbränningsmotorteknik.
    Ångström, Hans-Erik
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Förbränningsmotorteknik.
    Externally divided exhaust period on a turbocompound engine for fuel-saving2014Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    To improve exhaust heat utilization of a turbocharged engine, divided exhaust period (DEP) and turbocompound are integrated. The DEP concept decreases pumping loss created by the turbocompound. In the DEP concept the exhaust flow is divided between two different exhaust manifolds, blowdown and scavenging. One of the two exhaust valves on each engine cylinder is opened to the blowdown manifold at the first phase of exhaust stroke and the other valve is opened to the scavenging manifold at the later phase of exhaust stroke. This leads to lower exhaust back pressure and pumping loss. The combination of turbocompound engine with DEP has been examined previously and the result showed that this combination reduces the fuel consumption in low engine speeds and deteriorates it in high engine speeds. The main restriction of this combination was the low effective flow areas of the exhaust valves at high engine speeds.

    To overcome this restriction and increase the effective flow areas of the exhaust valves, DEP is employed externally on the exhaust manifold instead of engine exhaust valves. In externally DEP (ExDEP), both exhaust valves will be opened and closed similar to the corresponding turbocharged engine and the exhaust flow is divided by flow splits on the exhaust manifold. Two valves on the outlet ports of each flow split are added. One of them is a non-return valve (check valve) and the other one is synchronized with the cam shaft.

    In this study, the fuel-saving potential of ExDEP is analysed on the turbocompound engine at different engine speeds and loads and compared with the corresponding turbocharged engine, turbocompound engine and turbocompound DEP engine equipped. The results show that ExDEP has a great fuel-saving potential in almost all load points.

    ExDEP concept, itself, is a novel concept that there is no available literature about it. Moreover, combination of this new gas exchange system with turbocompound engines is an innovative extension of combined turbocompound DEP engines.

  • 19.
    Aghaali, Habib
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Förbränningsmotorteknik.
    Ångström, Hans-Erik
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Förbränningsmotorteknik.
    Improving Turbocharged Engine Simulation by Including Heat Transfer in the Turbocharger2012Inngår i: 2012 SAE International, SAE international , 2012Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Engine simulation based on one-dimensional gas dynamics is well suited for integration of all aspects arising in engine and power-train developments. Commonly used turbocharger performance maps in engine simulation are measured in non-pulsating flow and without taking into account the heat transfer. Since on-engine turbochargers are exposed to pulsating flow and varying heat transfer situations, the maps in the engine simulation, i.e. GT-POWER, have to be shifted and corrected which are usually done by mass and efficiency multipliers for both turbine and compressor. The multipliers change the maps and are often different for every load point. Particularly, the efficiency multiplier is different for every heat transfer situation on the turbocharger. The aim of this paper is to include the heat transfer of the turbocharger in the engine simulation and consequently to reduce the use of efficiency multiplier for both the turbine and compressor. A set of experiment has been designed and performed on a water-oil-cooled turbocharger, which was installed on a 2 liter GDI engine with variable valve timing, for different load points of the engine and different conditions of heat transfer in the turbocharger. The experiments were the base to simulate heat transfer on the turbocharger, by adding a heat sink before the turbine and a heat source after the compressor. The efficiency multiplier of the turbine cannot compensate for all heat transfer in the turbine, so it is needed to put out heat from the turbine in addition to the using of efficiency multiplier. Results of this study show that including heat transfer of turbocharger in engine simulation enables to decrease the use of turbine efficiency multiplier and eliminate the use of compressor efficiency multiplier to correctly calculate the measured gas temperatures after turbine and compressor.

  • 20.
    Aghaali, Habib
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Förbränningsmotorteknik.
    Ångström, Hans-Erik
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Förbränningsmotorteknik.
    Performance Sensitivity to Exhaust Valves and Turbine Parameters on a Turbocompound Engine with Divided Exhaust Period2014Inngår i: SAE International Journal of Engines, ISSN 1946-3936, E-ISSN 1946-3944, Vol. 7, nr 4, 1722-1733 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Turbocompound can utilize part of the exhaust energy on internal combustion engines; however, it increases exhaust back pressure, and pumping loss.  To avoid such drawbacks, divided exhaust period (DEP) technology is combined with the turbocompound engine. In the DEP concept the exhaust flow is divided between two different exhaust manifolds, blowdown and scavenging, with different valve timings. This leads to lower exhaust back pressure and improves engine performance.

    Combining turbocompound engine with DEP has been theoretically investigated previously and shown that this reduces the fuel consumption and there is a compromise between the turbine energy recovery and the pumping work in the engine optimization. However, the sensitivity of the engine performance has not been investigated for all relevant parameters. The main aim of this study is to analyze the sensitivity of this engine architecture in terms of break specific fuel consumption to different parameters concerning the gas exchange such as blowdown valve timing, scavenging valve timing, blowdown valve size, scavenging valve size, discharge coefficients of blowdown and scavenging ports, turbine efficiency, turbine size and power transmission efficiency. This study presents the sensitivity analysis of the turbocompound DEP engine to these parameters and defines a set of important parameters that should be examined in experimental studies.

  • 21.
    Aghaali, Habib
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Förbränningsmotorteknik.
    Ångström, Hans-Erik
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Förbränningsmotorteknik.
    Temperature Estimation of Turbocharger Working Fluids and Walls under Different Engine Loads and Heat Transfer Conditions2013Inngår i: SAE Technical Papers, 2013Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Turbocharger performance maps, which are used in engine simulations, are usually measured on a gas-stand where the temperatures distributions on the turbocharger walls are entirely different from that under real engine operation. This should be taken into account in the simulation of a turbocharged engine. Dissimilar wall temperatures of turbochargers give different air temperature after the compressor and different exhaust gas temperature after the turbine at a same load point. The efficiencies are consequently affected. This can lead to deviations between the simulated and measured outlet temperatures of the turbocharger turbine and compressor. This deviation is larger during a transient load step because the temperatures of turbocharger walls change slowly due to the thermal inertia. Therefore, it is important to predict the temperatures of turbocharger walls and the outlet temperatures of the turbocharger working fluids in a turbocharged engine simulation.

    In the work described in this paper, a water-oil-cooled turbocharger was extensively instrumented with several thermocouples on reachable walls. The turbocharger was installed on a 2-liter gasoline engine that was run under different loads and different heat transfer conditions on the turbocharger by using insulators, an extra cooling fan, radiation shields and water-cooling settings. The turbine inlet temperature varied between 550 and 850 °C at different engine loads.

    The results of this study show that the temperatures of turbocharger walls are predictable from the experiment. They are dependent on the load point and the heat transfer condition of the turbocharger. The heat transfer condition of an on-engine turbocharger could be defined by the turbine inlet temperature, ambient temperature, oil heat flux, water heat flux and the velocity of the air around the turbocharger. Thus, defining the heat transfer condition and rotational speed of the turbocharger provides temperatures predictions of the turbocharger walls and the working fluids. This prediction enables increased precision in engine simulation for future work in transient operation.

  • 22.
    Aghaali, Habib
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Förbränningsmotorteknik. KTH, Skolan för industriell teknik och management (ITM), Centra, Competence Center for Gas Exchange (CCGEx).
    Ångström, Hans-Erik
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Förbränningsmotorteknik. KTH, Skolan för industriell teknik och management (ITM), Centra, Competence Center for Gas Exchange (CCGEx).
    The Exhaust Energy Utilization of a Turbocompound Engine Combined with Divided Exhaust Period2014Konferansepaper (Fagfellevurdert)
    Abstract [en]

    To decrease the influence of the increased exhaust pressure of a turbocompound engine, a new architecture is developed by combining the turbocompound engine with divided exhaust period (DEP). The aim of this study is to utilize the earlier stage (blowdown) of the exhaust stroke in the turbine(s) and let the later stage (scavenging) of the exhaust stroke bypass the turbine(s). To decouple the blowdown phase from the scavenging phase, the exhaust flow is divided between two different exhaust manifolds with different valve timing. A variable valve train system is assumed to enable optimization at different load points. The fuel-saving potential of this architecture have been theoretically investigated by examining different parameters such as turbine flow capacity, blowdown valve timing and scavenging valve timing. Many combinations of these parameters are considered in the optimization of the engine for different engine loads and speeds.

    This architecture produces less negative pumping work for the same engine load point due to lower exhaust back pressure; however, the exhaust mass flow into the turbine(s) is decreased. Therefore, there is a compromise between the turbine energy recovery and the pumping work. According to this study, this combination shows fuel-saving potential in low engine speeds and limitations at high engine speeds. This is mainly due to the choked flow in the exhaust valves because this approach is using only one of the two exhaust valves at a time. To reveal the full potential of this approach, increasing the effective flow area of the valves should be studied.

  • 23.
    Aghaali, Habib
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Förbränningsmotorteknik.
    Ångström, Hans-Erik
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Förbränningsmotorteknik.
    Turbocharged SI-Engine Simulation with Cold and Hot-Measured Turbocharger Performance Maps2012Inngår i: Proceedings of ASME Turbo Expo 2012, Vol 5, ASME Press, 2012, 671-679 s.Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Heat transfer within the turbocharger is an issue in engine simulation based on zero and one-dimensional gas dynamics. Turbocharged engine simulation is often done without taking into account the heat transfer in the turbocharger. In the simulation, using multipliers is the common way of adjusting turbocharger speed and parameters downstream of the compressor and upstream of the turbine. However, they do not represent the physical reality. The multipliers change the maps and need often to be different for different load points. The aim of this paper is to simulate a turbocharged engine and also consider heat transfer in the turbocharger. To be able to consider heat transfer in the turbine and compressor, heat is transferred from the turbine volute and into the compressor scroll. Additionally, the engine simulation was done by using two different turbocharger performance maps of a turbocharger measured under cold and hot conditions. The turbine inlet temperatures were 100 and 600°C, respectively. The turbocharged engine experiment was performed on a water-oil-cooled turbocharger (closed waste-gate), which was installed on a 2-liter gasoline direct-injected engine with variable valve timing, for different load points of the engine. In the work described in this paper, the difference between cold and hot-measured turbocharger performance maps is discussed and the quantified heat transfers from the turbine and to/from the compressor are interpreted and related to the maps.

  • 24.
    Aghaali, Habib
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Förbränningsmotorteknik. KTH, Skolan för industriell teknik och management (ITM), Centra, Competence Center for Gas Exchange (CCGEx).
    Ångström, Hans-Erik
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Förbränningsmotorteknik. KTH, Skolan för industriell teknik och management (ITM), Centra, Competence Center for Gas Exchange (CCGEx).
    Serrano, Jose R
    Universitat Politècnica de València.
    Evaluation of different heat transfer conditions on an automotive turbocharger2014Inngår i: International Journal of Engine Research, ISSN 1468-0874, Vol. 16, nr 2, 137-151 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper presents a combination of theoretical and experimental investigations for determining the main heat fluxes within a turbocharger. These investigations consider several engine speeds and loads as well as different methods of conduction, convection, and radiation heat transfer on the turbocharger. A one-dimensional heat transfer model of the turbocharger has been developed in combination with simulation of a turbocharged engine that includes the heat transfer of the turbocharger. Both the heat transfer model and the simulation were validated against experimental measurements. Various methods were compared for calculating heat transfer from the external surfaces of the turbocharger, and one new method was suggested.

    The effects of different heat transfer conditions were studied on the heat fluxes of the turbocharger using experimental techniques. The different heat transfer conditions on the turbocharger created dissimilar temperature gradients across the turbocharger. The results show that changing the convection heat transfer condition around the turbocharger affects the heat fluxes more noticeably than changing the radiation and conduction heat transfer conditions. Moreover, the internal heat transfers from the turbine to the bearing housing and from the bearing housing to the compressor are significant, but there is an order of magnitude difference between these heat transfer rates.

  • 25.
    Ahlberg, Joakim
    Statens väg- och transportforskningsinstitut, Samhälle, miljö och transporter, SAMT, Transportekonomi, TEK.
    Energimätning på tåg för rundvirkestransporter på sträckan Mora–Borlänge–Gävle2014Rapport (Annet vitenskapelig)
    Abstract [sv]

    I det tredje delprojektet av ELVIS-demonstrationsprojektet för längre och tyngre godståg är syftet att mäta energianvändningen som ett tyngre tågset ger upphov till. Med tyngre avses här en ökad totalvikt genom fler vagnar, både fullastade och olastade, än vad som normalt körs på sträckan. Antagandet är att det med tyngre tåg finns möjlighet att göra (gods)transporter mer energieffektiva. Målsättningen är att framför allt testa hypotesen: · Att energianvändningen per tonkilometer kan reduceras genom att använda tyngre tåg. Rapporten belyser svårigheterna med att använda befintlig data för utvärdering av vad som driver energianvändningen på tåg. Datat i har inte varit kvalitetssäkrad för ändamålen i denna studie, vilket har orsakat en hel del fel och tillförlitligheten på vissa resultat är lägre än de skulle behöva vara. En slutsats från projektet att det skulle behövas en genomgång av databaserna hos Trafikverket om energianvändning ska studeras närmare, i alla fall om Trafikverkets utrustning för energimätning ska användas. Alternativt bör extern utrustning monteras på loken för att på så vis generera mer ändamålsenlig data, det senare var dock omöjligt då lokägaren inte godkände det. En annan slutsats är att körstilen spelar roll, det skiljer upp till 20 procent använd nettoenergi mellan förarna. Givet alla felkällor har ändå en regressionsanalys gjorts för att analysera hur energianvändningen för ett godståg kan bero på bruttovikten på tåget samt antal stopp tåget gör. Resultaten indikerar att det är skillnader på energianvändning för olika bruttovikter på tåget, men då det är oklart hur resultaten ska tolkas så krävs det mera mätningar för att kunna säga något bestämt. Detsamma gäller för hur antalet stopp påverkar användningen av energi, i en mätning fick vi ingen påverkan på energianvändningen av antal stopp medan vi fick det i en annan.

  • 26.
    Ahlström, Christer
    et al.
    Statens väg- och transportforskningsinstitut, Trafik och trafikant,TRAF, Samspel människa, fordon, transportsystem, MFT.
    Andersson, Jan
    Statens väg- och transportforskningsinstitut, Trafik och trafikant,TRAF, Samspel människa, fordon, transportsystem, MFT.
    Anund, Anna
    Statens väg- och transportforskningsinstitut, Trafik och trafikant,TRAF, Samspel människa, fordon, transportsystem, MFT.
    Börjesson, Emma
    Scania.
    Johansson, Hanna
    Scania.
    Johnsson, Johanna
    Scania.
    Detecting sleepiness by Optalert: final report2010Rapport (Annet vitenskapelig)
    Abstract [en]

    Many crashes with heavy vehicle can be attributed to driver sleepiness or driving impairment due to sleepiness, and it is important to find methods to predict those situations and counteract this problem. The Optalert fatigue management system claims to be able to detect sleepiness. The aims of this study are to (a) evaluate if Optalert can detect sleepiness equally well as other sleepiness indicators and (b) if the data patterns obtained by Optalert correlates with these other sleepiness indicators. Twelve sleep deprived truck drivers drove for about 90 minutes in an advanced moving base truck simulator. The experimental setup, including the sleep deprivation, was designed so that the drivers should become increasingly sleepier during the trial and the intention was that they should fall asleep during the experiment.

    Four different indicators of sleepiness or driving impairment due to sleepiness were used to monitor the state of the drivers; the Karolinska Sleepiness Scale (KSS), the variability in lateral position (SDLP), the blink duration and the Optalert system. The results show that all four sleepiness indicators increased with time on task. An analysis of variance revealed that the changes were significant for KSS, blink duration and the Optalert system, and a correlation analysis showed that Optalert correlated significantly with blink duration and SDLP. However, even though these correlations were significant, they were all rather low with a maximum correlation coefficient of 0.24.

    In conclusion, the Optalert system is promising and the sleepiness rating provided by the system works at least equally well as the other three sleepiness indicators. There are some practical limitations to the system; there is no reliable threshold which can be used to determine when a driver is getting too sleepy to drive (this is also the case for other available sleepiness indicators), the driver needs to be attached to the vehicle via the spectacle frames and a wire, and the quality of the eye movement recordings often deteriorated when the driver started driving the truck. Moreover, during the experiment the technical reliability was sometimes low.

  • 27.
    Ahlström, Christer
    et al.
    Statens väg- och transportforskningsinstitut, Trafik och trafikant,TRAF, Samspel människa, fordon, transportsystem, MFT.
    Bolling, Anne
    Statens väg- och transportforskningsinstitut, Trafik och trafikant,TRAF, Fordonsteknik och simulering, FTS.
    Sörensen, Gunilla
    Statens väg- och transportforskningsinstitut, Trafik och trafikant,TRAF, Trafiksäkerhet, samhälle och trafikant, TST.
    Eriksson, Olle
    Statens väg- och transportforskningsinstitut, Infrastruktur, INFRA, Drift och underhåll, DOU.
    Andersson, Anders
    Statens väg- och transportforskningsinstitut, Trafik och trafikant,TRAF, Fordonsteknik och simulering, FTS.
    Validating speed and road surface realism in VTI driving simulator III2012Rapport (Annet vitenskapelig)
    Abstract [sv]

    Nya simulatormodeller för vibrationer, ljud och grafik har utvecklats och implementerats i VTI:S fordonssimulator III. Syftet med denna studie är att validera simulatorn med avseende på hastighet och återgivandet av olika vägyteparametrar. Tjugofyra försökspersoner deltog i studien. De fick köra en och samma rutt i såväl simulator III som på verklig väg. Tre vägavsnitt med olika kvalitet på vägytan, från mycket slät till ganska ojämn, ingick i försöket. Såväl den objektiva förarparametern hastighet som olika subjektiva parametrar avseende förarens uppfattning om vägytans egenskaper (jämnhet, tysthet, komfort) jämfördes. Ett vägavsnitt med skiftande hastighetsgränser var av speciellt intresse. Ingen signifikant skillnad kunde noteras mellan körning i simulator och på verklig väg vare sig avseende hastighet (på avsitt med konstant hastighetsgräns) eller gradering av jämnhet och tysthet. För sträckan med skiftande hastighetsgränser fanns dock en signifikant skillnad mellan hastigheten i bil jämfört med hastigheten i simulator, trots liknande hastighetsprofiler. Såväl accelerationerna som retardationerna var snabbare i simulatorn. Vägkomforten graderades högre i bil än i simulator, men i båda fallen var tendensen den att slätare vägar gav högre värdering av komforten. Dessa resultat indikerar absolut validitet för graderingen av jämnhet och tysthet och för det objektiva måttet hastighet, medan relativ validitet indikerades för såväl hastighet vid skylt för hastighetsändring som för gradering av komfort.

  • 28.
    Ahlström, Christer
    et al.
    Statens väg- och transportforskningsinstitut, Trafik och trafikant,TRAF, Samspel människa, fordon, transportsystem, MFT.
    Dukic, Tania
    Statens väg- och transportforskningsinstitut, Trafik och trafikant,TRAF, Samspel människa, fordon, transportsystem, MFT.
    Ivarsson, Erik
    SmartEye.
    Kircher, Albert
    Statens väg- och transportforskningsinstitut.
    Rydbeck, Bosse
    SmartEye.
    Viström, Matias
    Saab Automobile.
    Performance of a one-camera and a three-camera system2010Rapport (Annet vitenskapelig)
    Abstract [en]

    Driving and operating a vehicle is to a great extent a visual task. In driver behaviour studies it is therefore important to be able to measure where the driver is looking. Today this can be done unobtrusively and remotely in real-time with camera based eye tracking. The most common remote eye tracking systems use multiple cameras in order to give satisfactory results. However, promising results using only one camera has recently emerged on the market. The main objective of this study is to compare eye tracking systems with one and three cameras, respectively, during various measurement conditions.

    A total of 53 participants were enrolled in the study. Data from the two eye trackers were acquired and analysed in terms of availability, accuracy and precision. The results indicate that both availability and accuracy are affected by many different factors. The most important factors are the number of cameras that is used and the angular distance from straight ahead. In the central region (straight ahead) both one-camera and three-camera systems have a high degree of accuracy and availability, but with increasing distance from the central region, the results deteriorate. This effect falls harder upon the one-camera system. Interestingly, there were no significant effects when wearing glasses in either availability or accuracy. There was however an interaction effect between distance and glasses.

    Advantages with a one-camera system are that it is cheaper, easier to operate and easier to install in a vehicle. A multi-camera system will, on the other hand, provide higher availability and accuracy for areas that are far from the road centre. A one-camera system is thus mostly suitable for in-vehicle applications such as systems that warn drivers for sleepiness or distraction while multi-camera solutions are preferable for research purposes.

  • 29.
    Ahlström, Christer
    et al.
    Statens väg- och transportforskningsinstitut, Trafik och trafikant,TRAF, Samspel människa, fordon, transportsystem, MFT.
    Kircher, Katja
    Statens väg- och transportforskningsinstitut, Trafik och trafikant,TRAF, Samspel människa, fordon, transportsystem, MFT.
    Rydström, Annie
    Volvo Car Corperation.
    Nåbo, Arne
    SAAB Automobile.
    Almgren, Susanne
    SAAB Automobile.
    Ricknäs, Daniel
    Scania.
    Effects of visual, cognitive and haptic tasks on driving performance indicators2012Inngår i: Advances in Human Aspects of Road and Rail Transportation / [ed] Neville A . Stanton, San Francisco, USA: CRC Press , 2012, 673-682 s.Konferansepaper (Fagfellevurdert)
  • 30.
    Aishwar, Ravichandran
    KTH, Skolan för teknikvetenskap (SCI).
    Aerodynamics of Bird Flight2014Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [en]

    It is the objective of this thesis project to understand the physics behind the different modes of bird flight and to do numerical two dimensional simulations of pure plunging, pure pitching and combined pitch-plunging motion of an aerofoil. First, the different physical models used to understand the generation of thrust are explained. Then the numerical model used for the simulation is explained briefly. Then the results and analysis of the numerical simulations are presented.

  • 31.
    Ajdén, Per
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik.
    Backlund, Carl
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik.
    Pilotmodeller till flygmekanisk simulator för JAS 39 Gripen2010Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    Abstract

    SAAB has for a long time used user controlled pilot models in ARES. ARES is a simulation tool used in the desktop environment for simulations and calculations of the JAS 39 Gripen fighter and other aircraft. ARES stands for ”Aircraft Rigid body Engineering Simulation”. To work with these pilot models has been both time-consuming and inefficient. In this master thesis, new pilot models are developed, where parameters are automatically generated, this will result in that the user doesn’t have to put a lot of work into adjusting the gains for different manoeuvres. This is called gain scheduling.

    To make this possible, simple models of the aircraft were created at different points in the envelope. These models were then used to calculate optimal controllers using LQ-control and pole placement techniques. These models and controllers were then implemented in Simulink. Simulink was then used to test the controllers before they were implemented in ARES.

    Control in all modes except roll attitude and speed by throttle are based on LQ-control in pitch-, roll- and yaw-angular velocity. And through these angular velocities the other angles are controlled by simple controllers, who is generating a reference in angular velocity. The roll attitude controller is based on direct pole placement based upon desired damping and undamped natural frequency, and the speed controller is based upon a model of throttle positions in trimmed states.

    The new pilot models are usable to control:

    • Roll rate
    • Roll attitude
    • Pitch rate
    • Pitch attitude
    • Angle of attack
    • Load factor
    • Yaw attitude
    • Course angle
    • Climb angle
    • Mach number
    • Climb rate

    These controllers can be combined so that the aircraft can perform desired maneuvers.

  • 32. Alam, M M
    et al.
    Barsoum, Zuheir
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Lättkonstruktioner.
    Jonsen, P
    Kaplan, A F H
    Haggblad, H A
    Influence of defects on fatigue crack propagation in laser hybrid welded eccentric fillet joint2011Inngår i: Engineering Fracture Mechanics, ISSN 0013-7944, E-ISSN 1873-7315, Vol. 78, nr 10, 2246-2258 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Fatigue cracking of laser hybrid welded eccentric fillet joints has been studied for stainless steel. Two-dimensional linear elastic fracture mechanics analysis was carried out for this joint geometry for four point bending load. The numerical simulations explain for the experimental observations why the crack propagates from the lower weld toe and why the crack gradually bends towards the root. Lack of fusion turned out to be uncritical for the initiation of cracks due to its compressive stress conditions. The linear elastic fracture mechanics analysis has demonstrated in good qualitative agreement with fatigue test results that lack of fusion slightly (<10%) reduces the fatigue life by accelerating the crack propagation. For the geometrical conditions studied here improved understanding of the crack propagation was obtained and in turn illustrated. The elaborated design curves turned out to be above the standard recommendations.

  • 33.
    Alberer, Daniel
    et al.
    Johannes Kepler University.
    Hjalmarsson, HåkanKTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.del Re, LuigiJohannes Kepler University.
    Identification for Automotive Systems2012Collection/Antologi (Fagfellevurdert)
  • 34.
    Alberer, Daniel
    et al.
    Johannes Kepler University.
    Hjalmarsson, Håkan
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    del Re, Luigi
    Johannes Kepler University.
    System Identification for Automotive Systems: Opportunities and Challenges2012Inngår i: Identification for Automotive Systems / [ed] Daniel Alberer, Håkan Hjalmarsson, Luigi del Re, Springer London, 2012, 1-10 s.Kapittel i bok, del av antologi (Fagfellevurdert)
    Abstract [en]

    Without control many essential targets of the automotive industry could not be achieved. As control relies directly or indirectly on models and model quality directly influences the control performance, especially in feedforward structures as widely used in the automotive world, good models are needed. Good first principle models would be the first choice, and their determination is frequently difficult or even impossible. Against this background methods and tools developed by the system identification community could be used to obtain fast and reliably models, but a large gap seems to exist: neither these methods are sufficiently well known in the automotive community, nor enough attention is paid by the system identification community to the needs of the automotive industry. This introduction summarizes the state of the art and highlights possible critical issues for a future cooperation as they arose from an ACCM Workshop on Identification for Automotive Systems recently held in Linz, Austria.

  • 35. Albertsson, Pontus
    et al.
    Björnstig, Ulf
    Falkmer, Torbjörn
    Statens väg- och transportforskningsinstitut.
    Turbell, Thomas
    Statens väg- och transportforskningsinstitut.
    Litteraturöversikt Skadehändelser relaterade till busstrafik: Buss-OLA - en trafiksäker bussfärd2003Rapport (Annet vitenskapelig)
    Abstract [en]

    The aim of this literature review was to describe the pattern of injuries and fatalities related to bus traffic. Furthermore, the aim was to identify possible future measurements for improvement of passive safety in buses. Bus crashes were presented in international literature virtually in as many ways as there were articles on the topic. Hence, the authors used the term bus incidents, in order to cover all types of injuries related to bus traffic. In this review only M2 and M3 buses, i.e. buses over 3.5 tonnes were included. In the vast majority of OECD countries, less than 1 % of the vehicle fleet was constituted of buses. Bus passenger's average person kilometres represented 10 % of the total road vehicle person kilometres annually.

    The number of fatalities and injured in bus incidents have been stable recent years in EU. The fatality risk is ten times lower for bus passengers compared with car occupants. Of all traffic fatalities, bus fatalities represented 0.3-0.5 %. The most frequent injury localisations from all types of bus crashes were lower limb (35 %), upper limb (33 %) and head/face (28 %). Rollovers occurred in almost all cases of severe crashes. Projection, total ejection, partial ejection, intrusion and smoke inhalation were the main injury mechanism. Three major injury groups in severe bus crashes were thoracic injuries, massive injuries and pelvic fractures.

    Heavy wind seemed to be capable of affecting the bus dynamics, particularly on highly built buses (e.g. as high as 4.3 meters). Unprotected road users were hit by buses in about 1/3 of all cases in Sweden. Side impact was most common for local buses (38 %). Boarding and alighting were contributing to injuries in about 1/3 of all cases. If the coach has more than one section it seems that the upper section is more exposed to risk for injuries than the lower section.

    Safety belts can improve the passive safety in buses. The 2-point belt prevents passenger ejection but in frontal crashes the jack knife effect could cause head and thoracic injuries. However, the 3- point belt provides the best restraint in rollovers and frontal crashes, as it keeps the passenger remained seated.

  • 36. Albertsson, Pontus
    et al.
    Linder, Astrid
    Statens väg- och transportforskningsinstitut, Trafik och trafikant,TRAF, Trafiksäkerhet, samhälle och trafikant, TST.
    Evaluation of extrication techniques. - Is there any other quality measurement then time?2007Konferansepaper (Fagfellevurdert)
  • 37. Albinsson, A.
    et al.
    Bruzelius, F.
    Jacobson, B.
    Gustafsson, T.
    Jonasson, Mats
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg. Volvo Cars, Sweden.
    Identification of tyre characteristics using active force excitation2016Inngår i: The Dynamics of Vehicles on Roads and Tracks - Proceedings of the 24th Symposium of the International Association for Vehicle System Dynamics, IAVSD 2015, CRC Press, 2016, 501-510 s.Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Knowledge of the maximum tyre-road friction coefficient can improve active safety systems by defining actuator boundaries and adaptable intervention thresholds. Estimation of the coefficient of friction based on tyre response measurements requires large level of force excitation. Under normal driving conditions, manoeuvres with large tyre utilizations are rare. This study investigates a method where wheel torques with opposite signs are applied to the front and rear axle simultaneously. This procedure allows for an intervention with large tyre excitations without disturbing the motion of the vehicle. The intervention is evaluated in simulations and experiments. Further, a method is proposed which does not require measurement of the vehicle longitudinal velocity. The results show that it is possible to estimate the current friction coefficient with the proposed method, although the assumption made in the proposed method makes the friction estimate sensitive to measurement noise on the wheel speed signal.

  • 38.
    Albinsson, Anton
    et al.
    Chalmers Tekniska Högskola.
    Bruzelius, Fredrik
    Statens väg- och transportforskningsinstitut, Trafik och trafikant,TRAF, Fordonsteknik och simulering, FTS. Chalmers Tekniska Högskola.
    Jacobson, Bengt
    Chalmers Tekniska Högskola.
    Jonasson, Mats
    Volvo Cars Cooperation.
    Tire Force Estimation Based on the Recursive Least Square Method Utilizing Wheel Torque Measurement2014Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This study investigates a new tire force estimator based on the recursive least square (RLS) method. Tire force estimation with known driving wheel torque is studied and compared to the case with torque estimation from the internal combustion engine. This is motivated by a future scenario with electric propulsion, which reasonably gives improved wheel torque estimations. Sensitivity to vehicle parameters and challenges with individual lateral tire force estimation are also investigated. The results, experimental and simulation data, show good performance and potential for tire force estimation using the RLS method.

  • 39. Albinsson, Anton
    et al.
    Bruzelius, Fredrik
    Pettersson, Pierre
    Jonasson, Mats
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg. Volvo Car Corporation, Sweden.
    Jacobson, Bengt
    Estimation of the inertial parameters of vehicles with electric propulsion2016Inngår i: Proceedings of the Institution of mechanical engineers. Part D, journal of automobile engineering, ISSN 0954-4070, E-ISSN 2041-2991, Vol. 230, nr 9, 1155-1172 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    More accurate information about the basic vehicle parameters can improve the dynamic control functions of a vehicle. Methods for online estimation of the mass, the rolling resistance, the aerodynamic drag coefficient, the yaw inertia and the longitudinal position of the centre of gravity of an electric hybrid vehicle is therefore proposed. The estimators use the standard vehicle sensor set and the estimate of the electric motor torque. No additional sensors are hence required and no assumptions are made regarding the tyre or the vehicle characteristics. Consequently, all information about the vehicle is available to the estimator. The estimators are evaluated using both simulations and experiments. Estimations of the mass, the rolling resistance and the aerodynamic drag coefficient are based on a recursive least-squares method with multiple forgetting factors. The mass estimate converged to within 3% of the measured vehicle mass for the test cases with sufficient excitation that were evaluated. Two methods to estimate the longitudinal position of the centre of gravity and the yaw inertia are also proposed. The first method is based on the equations of motion and was found to be sensitive to the measurement and parameter errors. The second method is based on the estimated mass and seat-belt indicators. This estimator is more robust and reduces the estimation error in comparison with that obtained by assuming static parameters. The results show that the proposed method improves the estimations of the inertial parameters. Hence, it enables online non-linear tyre force estimators and tyre-model-based tyre-road friction estimators to be used in production vehicles.

  • 40.
    Aldman, Bertil
    et al.
    Statens väg- och transportforskningsinstitut.
    Turbell, Thomas
    Statens väg- och transportforskningsinstitut.
    Huvudstöd1971Rapport (Annet vitenskapelig)
  • 41.
    Aldulaimi, Mustafa
    Concordia University, Montreal.
    Road lighting and safety: a pilot study of Arthabaska region2016Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We investigate the specification of roadway lighting for safety to understand the elements needed in statistical analysis of road collisions during night time. Several goals were targeted. First, which type of response is best, or whether both responses should be used. Second, which indicator of lighting should we favor? Third, which other factors should be included in the analysis and fourth, how effective is lighting in reducing nigh-time collision. The case study comprised illuminance and luminance measurements collected for the Arthabaska region in Quebec, along with available operational and geometric variables expected to explain roadway collisions. A zero-inflated negative-binomial model was used to analyze the impact of predictors on collision frequency and severity using classical maximum likelihood validated by a Full Bayesian regression. It was found that collision severity is best, resulting in more factors being significant in the expected sense of contribution. Luminance was the best indicator for road lighting. A correlation matrix aided in the identification of linearly dependencies between factors and the response or other factors. The last goal was investigated by comparing daytime with night-time collision analysis. The night time analysis included luminance and glare. The results were very close between day and night, with luminance proving to be an effective countermeasure for night collisions. A three-time difference on the coefficient for traffic volume was found. The use of a dummy variable related to standard levels of illumination is presented and will be key in future research for the estimation of effective levels of lighting.

  • 42.
    Alegret, Guillem
    et al.
    MAN Diesel & Turbo, Copenhagen, Denmark.
    Llamas, Xavier
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska fakulteten.
    Vejlgaard-Laursen, Morten
    MAN Diesel & Turbo, Copenhagen, Denmark.
    Eriksson, Lars
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska fakulteten.
    Modeling of a Large Marine Two-Stroke Diesel Engine with Cylinder Bypass Valve and EGR System2015Inngår i: 10th IFAC Conference on Manoeuvring and Control of Marine Craft MCMC 2015: Copenhagen, 24–26 August 2015 / [ed] Roberto Galeazzi and Mogens Blanke, IFAC Papers Online, 2015, Vol. 48, 273-278 s.Konferansepaper (Fagfellevurdert)
    Abstract [en]

    A nonlinear mean value engine model (MVEM) of a two-stroke turbocharged marine diesel engine is developed, parameterized and validated against measurement data. The goal is to have a computationally fast and accurate engine model that captures the main dynamics and can be used in the development of control systems for the newly introduced EGR system. The tuning procedure used is explained, and the result is a six-state MVEM with seven control inputs that capture the main system dynamics.

  • 43.
    Allam, Sabry
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, MWL Marcus Wallenberg Laboratoriet.
    Åbom, Mats
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, MWL Marcus Wallenberg Laboratoriet.
    Aeroacoustic investigation of diaphragm orifices in ducts2007Inngår i: Turkish Acoustical Society - 36th International Congress and Exhibition on Noise Control Engineering, INTER-NOISE 2007 ISTANBUL, 2007, 292-301 s.Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Diaphragm orifices are used in duct systems to control or measure the flow rate. Such components generate complex flows and aeroacoustic phenomena, e.g., dissipation via forced vortex shedding, sound generation from eddy structures (broadband noise) and non-linear whistling. In this paper the acoustic properties (passive and active) of single and double diaphragm orifices are investigated experimentally for small Mach-numbers and low frequencies (plane waves). Using microphone arrays and wave decomposition the induct sound fields are resolved and used as input to determine the active acoustic 2-port. The work represents one of the first efforts to apply 2-port methods to characterize flow generated noise in-ducts. The motivation of this work is to obtain better understanding for noise from flow singularities in ducts, e.g., in HVAC systems on vehicles, develop and improve prediction methods and produce data for validation of CFD and other models. First the single orifice case is investigated and the 2-port data is obtained. The active (source) strength part represents a dipole type of source for which a scaling law is derived. For the passive part (the scattering matrix) a simple quasi-stationary model is tested and works well up to a few hundred Hz. Secondly the double orifice configuration is investigated and again the 2-port data is measured. To investigate the presence of orifice interaction and non-linear aeroacoustic effects, such as whistling, the double orifice data is reduced to two identical single orifices. The equivalent source data for this reduced case is then compared with the single orifice scaling law. It is found that if the separation is larger than 10 orifice diameters then orifice interaction can be neglected. Non-linear effects and tendencies for whistling were found for separations less than 3-4 duct diameters.

  • 44. Allen, T.
    et al.
    Battley, M.
    Casari, P.
    Kerling, B.
    Stenius, Ivan
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Marina system.
    Westlund, Joacim
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Marina system.
    Structural responses of high performance sailing yachts to slamming loads2011Inngår i: 11th International Conference on Fast Sea Transportation, FAST 2011 - Proceedings, 2011, 585-592 s.Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Experimental measurements of transient strains, local accelerations and pressure were undertaken on the IMOCA Open 60' class sailing yacht Paprec-Virbac III, and on a replica hull panel section tested in a laboratory slam testing facility. The approximately 1m x 0.7m panel for laboratory testing was manufactured on a mould taken from the plug used for the vessel construction, ensuring that the panel had identical curved geometry to the vessel. The laboratory panel included two stringers as on the same region of the vessel. An instrumentation layout including arrays of resistance strain gauges, accelerometers and a transient pressure transducer was used. Linear displacement transducers were used to measure panel deformations during the laboratory tests. The laboratory testing was undertaken at a range of constant impact velocities from 0.5 to 3m/s using a Servohydraulic Slam Testing System. Sea-trials were undertaken in the Hauraki Gulf, Auckland New Zealand. There was good qualitative agreement between the field and laboratory measurements in regard to timing and relative magnitudes of strains at different positions on the structure. Results demonstrate that the hull structure undergoes very complex transient deformations during the slamming events.

  • 45.
    Alm, Torbjörn
    et al.
    HiQ.
    Isaksson, Calle
    HiQ.
    Raisins: towards general usability and drivability for ViP platform resources2014Rapport (Annet vitenskapelig)
    Abstract [en]

    The original purpose of the Raisins project was to make an inventory of the gathered software resources of ViP as they appear at the ViPForge, analyse their usability for reuse and propose a technical roadmap. In addition to this an investigation of industrial needs was planned to grip prioritization and complementation demands from the industrial partners. During the start-up process the idea of a more visionary approach for the ViP simulation software came up as an alternative path to take. The Raisins project was divided into four separate activities; inventory and evaluation of existing resources at ViPForge, review of the report from the early ViP project “Industrial Needs”, workshops with each of the industrial partners, and finally an activity at HiQ to sketch an alternative software approach.

  • 46.
    Amantini, Aladino (ed)
    et al.
    Kite.
    Hjälmdahl, Magnus
    Statens väg- och transportforskningsinstitut, Trafik och trafikant,TRAF, Samspel människa, fordon, transportsystem, MFT.
    Lai, Frank
    ITS, University of Leeds.
    Enjalbert, Simon
    UNIVAL.
    Shinar, David
    BGU.
    Hasewinkel, Håkan
    Chalmers.
    Kircher, Albert
    Chalmers.
    Lützhöft, Margareta
    Chalmers.
    Kecklund, Lena
    MTOP.
    Initial plan of dissemination and use of results2009Rapport (Annet vitenskapelig)
    Abstract [en]

    This document contains the initial plan for using and disseminating knowledge and foreground developed within the ITERATE Project.

    The Deliverable contains five main Chapters and an Appendix.

    The first Chapter describes the purpose of the document, its structure, and introduces the other sections. Chapter 2 and 3 define the dissemination strategy of the ITERATE project and provide a classification of dissemination activities. For each type of dissemination action, the corresponding implementation approach is proposed. Then, for each type of dissemination activity, the actions already performed and those planned are described in some details. The dissemination materials already produced by the project and their usage are briefly described. Materials and products already completed, as well as planned, are described, even though a dedicated Deliverable is foreseen in the future that will contain copies of the actual products provided for dissemination purposes. The Exploitation plan is discussed in the last Chapter of the Deliverable. The two different natures and typology of partners , i.e., academic and industrial/consultancy, are considered. In particular, for each partner, a market and competition analysis is performed and the objectives and guidelines for subsequent exploitation of the results is preliminarily discussed. Finally, the appendix contains, for completeness, the Dissemination and Exploitation Questionnaire utilised to collect information among partners.

  • 47.
    Amundin, Eskil
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Marina system.
    Modeling of fatigue in RORO ships2012Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    The largest modern Pure Car and Truck Carriers (PCTC’s) are typically 230 meters long and have 13 cargo decks. In order to facilitate rapid loading and unloading these ships have been subject to a development of reducing any obstructing structures in the cargo hold, meaning that the transversal shear preventing structures, i.e. the racking bulkheads, has been taken to a minimum. Previous studies have concluded that some points on the racking bulkheads, as a result of the stripped down design, are subject to high stresses resulting from wave induced accelerations of the ship.

    In this M.Sc. Thesis the fatigue life of a corner of a transverse bulkhead opening in a 230 meter long PCTC with a capacity of 7200 cars is calculated with different methods.

    •Fatigue life is calculated from recorded ship motion data with the notch stress method in conjunction with rain flow counting and the cumulative damage principal.

    • Fatigue life is calculated according to (DNV CN. 30.7, 2010), based on a Lloyd’s Register FE model load case.

    • Actual findings on the ship are compared to the calculated results. Due to the lack of inspection data this comparison is not very extensive and only more briefly discussed.

    It is concluded that the fatigue life of the examined point, calculated from recorded motion data is 9.6 years and the fatigue life according to DNV is 8.0 years. It is also found that the fatigue damage is cumulated in almost discrete portions and thus the calculated fatigue life can be inaccurate when a short period of time is evaluated as is done in this thesis.

    A modification to the racking bulkhead with respect to fatigue life is also analyzed and it is concluded that the fatigue life in the examined point could be extended significantly by some simple modifications to the geometry.

  • 48.
    Andersen, Camilla Sloth
    et al.
    Aalborg University, Denmark.
    Reinau, Kristian Hegner
    Aalborg University, Denmark.
    Agerholm, Niels
    Aalborg University, Denmark.
    The relationship between road characteristics and speed collected from floating car data2016Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Speed is of great importance to the safety level of a road. Speed choice is strongly influenced by the road environment and the drivers’ assessment of safe speed level at a specific location. This paper presents an analysis of the relationships between speed and road characteristics and speed and driver characteristics. The analysis is based on big data on speed and driver characteristics combined with data on road characteristics on 49 secondary rural two-lane roads in Denmark. Data is modelled using multivariate linear regression. The results show a primarily influence from road and shoulder width, the extent of road markings and the section lengths on speed. Secondly, they also show the presence of woodland and intersections influencing speed as do gender, age of vehicle and time of day.

  • 49.
    Andersson, Anders
    Linköpings universitet, Institutionen för datavetenskap. Linköpings universitet, Tekniska fakulteten. Swedish National Road and Transport Research Institute (VTI), Linköping, Sweden.
    Extensions for Distributed Moving Base Driving Simulators2017Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Modern vehicles are complex systems. Different design stages for such a complex system include evaluation using models and submodels, hardware-in-the-loop systems and complete vehicles. Once a vehicle is delivered to the market evaluation continues by the public. One kind of tool that can be used during many stages of a vehicle lifecycle is driving simulators.

    The use of driving simulators with a human driver is commonly focused on driver behavior. In a high fidelity moving base driving simulator it is possible to provide realistic and repetitive driving situations using distinctive features such as: physical modelling of driven vehicle, a moving base, a physical cabin interface and an audio and visual representation of the driving environment. A desired but difficult goal to achieve using a moving base driving simulator is to have behavioral validity. In other words, \A driver in a moving base driving simulator should have the same driving behavior as he or she would have during the same driving task in a real vehicle.".

    In this thesis the focus is on high fidelity moving base driving simulators. The main target is to improve the behavior validity or to maintain behavior validity while adding complexity to the simulator. One main assumption in this thesis is that systems closer to the final product provide better accuracy and are perceived better if properly integrated. Thus, the approach in this thesis is to try to ease incorporation of such systems using combinations of the methods hardware-in-the-loop and distributed simulation. Hardware-in-the-loop is a method where hardware is interfaced into a software controlled environment/simulation. Distributed simulation is a method where parts of a simulation at physically different locations are connected together. For some simulator laboratories distributed simulation is the only feasible option since some hardware cannot be moved in an easy way.

    Results presented in this thesis show that a complete vehicle or hardware-in-the-loop test laboratory can successfully be connected to a moving base driving simulator. Further, it is demonstrated that using a framework for distributed simulation eases communication and integration due to standardized interfaces. One identified potential problem is complexity in interface wrappers when integrating hardware-in-the-loop in a distributed simulation framework. From this aspect, it is important to consider the model design and the intersections between software and hardware models. Another important issue discussed is the increased delay in overhead time when using a framework for distributed simulation.

  • 50.
    Andersson, Anders
    et al.
    Statens väg- och transportforskningsinstitut, Trafik och trafikant,TRAF, Körsimulering och visualisering, SIM.
    Andersson Hultgren, Jonas
    Statens väg- och transportforskningsinstitut, Trafik och trafikant,TRAF, Körsimulering och visualisering, SIM.
    Leandertz, Rickard
    HiQ.
    Johansson, Martin
    Pitch Technologies.
    Betnér, Steve
    Pitch Technologies.
    Jakobson, Ola
    Volvo Car Corporation.
    Rolff, Fredrik
    Volvo Car Corporation.
    SimArch 2: Implementation and demonstration of the SimArch architecture2017Rapport (Annet vitenskapelig)
    Abstract [en]

    Complexity in modern vehicles consists of an increasingly large multitude of components that operate together. While functional verification of individual components is important, it is also important to test systems of interacting components within a driving environment, both from a functional perspective and from a driver perspective. One proven way for testing is vehicle simulators and in this work the main goals have been to increase flexibility and scalability by introducing a distributed driving simulator platform. 

    A distributed simulation architecture was designed and implemented, based on user needs defined in a previous project, which divides a driving simulator environment into four major entities with well-defined interfaces. These entities are Session Control, Environment Simulator, Driving Simulator and Vehicle simulator. High Level Architecture (HLA) Evolved, an IEEE standard, was chosen as the standard for communication. HLA Evolved is based on a publish-subscribe architecture, and is commonly used for distributed simulations. The entities and the communication topology are described in detail in the report.

    The evaluation of the distributed simulation architecture focused on flexibility and scalability, and on timing performance. Results show that the implemented distributed simulation architecture compared to the non-modified architecture increased flexibility and scalability, as several distributed setups were tested successfully. However, it also has an inherent communication latency due to packaging and sending of data between entities, which was estimated to be one millisecond. This is an effect which needs to be considered for a distributed simulation. Especially if the communication between the Driving Simulator and the Vehicle Simulator is sensitive to such delays. During evaluations of the distributed simulation architecture, the Driving Simulator and the Vehicle Simulator were always located at one site in a low latency configuration.

1234567 1 - 50 of 1457
RefereraExporteraLink til resultatlisten
Permanent link
Referera
Referensformat
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Annet format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annet språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf