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  • 1.
    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 Engines2013Ingår i: SAE Technical Papers, 2013, Vol. 11Konferensbidrag (Refereegranskat)
    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.

  • 2.
    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).
    A review of turbocompounding as a waste heat recovery system for internal combustion engines2015Ingår i: Renewable & sustainable energy reviews, ISSN 1364-0321, E-ISSN 1879-0690, Vol. 49, s. 813-824Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Internal combustion engines waste a large amount of fuel energy through their exhausts. Various technologies have been developed for waste heat recovery such as turbocompounds, Rankine bottoming cycles, and thermoelectric generators that reduce fuel consumption and CO2 emissions. Turbocompounding is still not widely applied to vehicular use despite the improved fuel economy, lower cost, volume, and complexity higher exhaust gas recirculation driving capability and improved transient response. This paper comprehensively reviews the latest developments and research on turbocompounding to discover important variables and provide insights into the implementation of a high-efficiency turbocompound engine. Attention should be paid to the optimization of turbocompound engines and their configurations because the major drawback of this technology is additional exhaust back-pressure, which leads to higher pumping loss in the engines. Applying different technologies and concepts on turbocompound engines makes the exhaust energy recovery more efficient and provides more freedom in the design and optimization of the engines. Turbine efficiency plays an important role in the recovery of the wasted heat so turbine design is a crucial issue in turbocompounding. In addition, variability in geometry and rotational speed of power turbines allows for more efficient turbocompound engines in different operating conditions. The conclusion drawn from this review is that turbocompounding is a promising technology for reducing fuel consumption in the coming decades in both light- and heavy-duty engines.

  • 3.
    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 Period2014Ingår i: Proceedings from the FISITA 2014 World Automotive Congress, 2014Konferensbidrag (Refereegranskat)
    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.

  • 4.
    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-saving2014Konferensbidrag (Övrigt vetenskapligt)
    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.

  • 5.
    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 Turbocharger2012Ingår i: 2012 SAE International, SAE international , 2012Konferensbidrag (Refereegranskat)
    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.

  • 6.
    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 Period2014Ingår i: SAE International Journal of Engines, ISSN 1946-3936, E-ISSN 1946-3944, Vol. 7, nr 4, s. 1722-1733Artikel i tidskrift (Refereegranskat)
    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.

  • 7.
    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 Conditions2013Ingår i: SAE Technical Papers, 2013Konferensbidrag (Refereegranskat)
    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.

  • 8.
    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 Period2014Konferensbidrag (Refereegranskat)
    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.

  • 9.
    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 Maps2012Ingår i: Proceedings of ASME Turbo Expo 2012, Vol 5, ASME Press, 2012, s. 671-679Konferensbidrag (Refereegranskat)
    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.

  • 10.
    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 turbocharger2014Ingår i: International Journal of Engine Research, ISSN 1468-0874, E-ISSN 2041-3149, Vol. 16, nr 2, s. 137-151Artikel i tidskrift (Refereegranskat)
    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.

  • 11.
    Agrell, Fredrik
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Maskinkonstruktion (Avd.).
    Ångström, Hans-Erik
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Maskinkonstruktion (Avd.).
    Eriksson, Bengt
    Wikander, Jan
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Maskinkonstruktion (Avd.).
    Linderyd, Johan
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Maskinkonstruktion (Avd.).
    Control of HCCI During Engine Transients by aid of Variable Valve Timings Through the use of Model Based Non-Linear Compensation2005Ingår i: SAE transactions, ISSN 0096-736X, Vol. 114, nr 3, s. 296-310Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    One of the main challenges with the Homogeneous Charge Compression Ignition, HCCI, combustion system is to control the Start Of Combustion, SOC, for varying load and external conditions. A method to achieve this on a cycle-by-cycle basis is to vary the valve timing based on a feedback signal from the SOC of previous cycles. The control can be achieved with two basic valve-timing strategies named the Overlap- and the IVC-method. The Overlap-method works by trapping of residuals while the IVC-method affects the effective compression ratio. In an earlier paper it has been shown that if the two methods are incorporated into one controller, SOC can be controlled in a relatively large operating window although the transient performance was not sufficient. The reason is that the simple PI-controller cannot be made fast enough to cope with the transients without magnifying the cycle-to-cycle variations of the combustion into instability. In this work a model based control system that features a non-linear compensation, based on the inverse of the non-linear function from valve timings to ignition delay, is suggested and evaluated. The results show good transient performance. Control performance from engine tests is reported. A combined engine and control simulation system is used for the development of the control strategies. The simulations are accomplished with a commercial cycle simulation code linked with a commercial control simulation code. The simulations are iteratively verified against engine test data. Engine tests are conducted on a single cylinder engine equipped with a hydraulic valve system.

  • 12.
    Agrell, Fredrik
    et al.
    KTH, Tidigare Institutioner                               , Maskinkonstruktion.
    Ångström, Hans-Erik
    KTH, Tidigare Institutioner                               , Maskinkonstruktion.
    Eriksson, Bengt
    Wikander, Jan
    KTH, Tidigare Institutioner                               , Maskinkonstruktion.
    Linderyd, Johan
    Integrated Simulation and Engine Test of Closed Loop HCCI Control by aid of Variable Valve Timings2003Ingår i: SAE transactions, ISSN 0096-736X, Vol. 112, nr 3, s. 1078-1091Artikel i tidskrift (Refereegranskat)
  • 13.
    Agrell, Fredrik
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Maskinkonstruktion (Avd.).
    Ångström, Hans-Erik
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Maskinkonstruktion (Avd.).
    Eriksson, Bengt
    Wikander, Jan
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Maskinkonstruktion (Avd.).
    Linderyd, Johan
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Maskinkonstruktion (Avd.).
    Practical Modeling of HCCI for Combustion Timing Control and Results from Engine Test2005Ingår i: KTH Internal Combustion Engine Report MFM, Vol. 162Artikel, forskningsöversikt (Refereegranskat)
  • 14.
    Agrell, Fredrik
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Maskinkonstruktion (Avd.).
    Ångström, Hans-Erik
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Maskinkonstruktion (Avd.).
    Eriksson, Bengt
    Wikander, Jan
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Maskinkonstruktion (Avd.).
    Linderyd, Johan
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Maskinkonstruktion (Avd.).
    Transient Control of HCCI Combustion by aid of Variable Valve Timing Through the use of a Engine State Corrected CA50-Controller Combined with an In-Cylinder State Estimator Estimating Lambda2005Konferensbidrag (Refereegranskat)
    Abstract [en]

    One of the main challenges with the Homogeneous Charge Compression Ignition, HCCI, combustion system is to control the Start Of Combustion, SOC, for varying load and external conditions. A method to achieve this on a cycle-by-cycle basis is to vary the valve timing based on a feedback signal from the SOC of previous cycles. The control can be achieved with two basic valve-timing strategies named the Overlap- and the IVC-method. The Overlap-method works by trapping of residuals while the IVC-method affects the effective compression ratio

  • 15.
    Agrell, Fredrik
    et al.
    KTH, Tidigare Institutioner, Maskinkonstruktion.
    Ångström, Hans-Erik
    KTH, Tidigare Institutioner, Maskinkonstruktion.
    Eriksson, Bengt
    Wikander, Jan
    KTH, Tidigare Institutioner, Maskinkonstruktion.
    Linderyd, Johan
    Transient Control of HCCI Through Combined Intake and Exhaust Valve Actuation2003Konferensbidrag (Refereegranskat)
    Abstract [en]

    Homogeneous Charge Compression Ignition, HCCI, has the attractive feature of low particulate emission and low Nitrogen Oxides, NOx, emission combined with high efficiency. The principle is a combination of an Otto and a Diesel engine in that a premixed charge is ignited by the compression heat.

  • 16.
    Bernemyr, Hanna
    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.
    Characterization of Tailpipe Exhaust Particles using a Rotating Disc Diluter and a Volatility Tandem DMA (v-TDMA)2006Ingår i: SAE 2006 Transactions Journal of Fuels and Lubricants, 2006, Vol. 2006-01-3367Konferensbidrag (Refereegranskat)
    Abstract [en]

    A v-TDMA instrument has been used to study the tailpipe exhaust particles of a heavy-duty Diesel engine equipped with a continuously regenerating trap (CRT) running at two different steady state conditions: high speed / medium load and medium speed / high load. The sample was extracted directly out of the engine and conditioned by use of a rotating disc diluter. This paper deals with measurements where the parallel mode of the v-TDMA instrument was used. A temperature of 350 °C was applied in the heated section of the v-TDMA to study the thermal stability of the particles. Dilution between 86 and 1740 times were applied to see if the amount of dilution affected the particle behavior. The CRT reduces the number concentration of accumulation mode particles by 90%. When using the CRT, high numbers of nucleation mode particles are measured that can be volatilized at 350° in the v-TDMA instrument. For nucleation mode particles, changing the dilution from 86 to 386 times can suppress particle formation by up to 90%. The present work shows that the rotating disc diluter together with the v-TDMA instrument are promising tools for study of exhaust particles sampled directly out of the engine.

  • 17.
    Bernemyr, Hanna
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.).
    Ångström, Hans-Erik
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.).
    Number Measurements and Size Dependent Volatility Study of Diesel Exhaust Particles2007Ingår i: SAE Technical Paper 2007-24-0107, 2007, Vol. 2007-24-0107, s. 10.4271/2007-24-0107-Konferensbidrag (Refereegranskat)
    Abstract [en]

    An in-house developed volatility tandem differential mobility analyzer (v-TDMA) instrument in tandem mode has been used to study the exhaust particles of a heavy-duty Diesel engine equipped with a continuously regenerating trap (CRT) at two steady state conditions: medium speed / 100 % load and high speed idle. By use of the tandem mode of the v-TDMA instrument, particles in a narrow size range are led to the heater and the size dependent volatility can be studied. A rotating disc diluter was used to condition the sample. Temperatures between ambient temperature and 350 °C have been applied to study the volatility of the particles. The current work indicates that particles generated at high load have the same size after heating as before being heated. At high speed idle, small fractions of material can be found as smaller sized particles after heating. The study is an attempt to obtain size dependent information about engine exhaust particles. The main contribution is in the size distributed information about particle volatility. The current work also shed some light on the complexities of size separated particle number measurements.

  • 18.
    Bernemyr, Hanna
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.).
    Ångström, Hans-Erik
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.).
    Number measurements of diesel exhaust particles - Influence of dilution and fuel sulphur content2007Ingår i: SAE Technical Paper 2007-01-0064, 2007, Vol. 2007-01-0064, s. 2007-01-0064-Konferensbidrag (Refereegranskat)
    Abstract [en]

    A volatility tandem differential mobility analyzer (v-TDMA) in parallel mode with the heated section at 350 °C has been used to study the number size distribution of exhaust particles from a heavy-duty Diesel engine equipped with a continuously regenerating trap (CRT). Total number concentrations have also been measured by use of a stand-alone CPC preceded by a heater at 350 °C. The sample was extracted directly from the exhaust pipe and conditioned by use of a rotating disc diluter. Two different dilution factors were applied (86 and 386 times) showing that the higher dilution reduces the number of small particles as particle formation is partly suppressed. Two different Diesel fuel qualities have been used showing that the 400 ppm sulphur fuel generates higher numbers of nucleation mode particles than the 3.5 ppm sulphur fuel. Particles formed with the 400 ppm sulphur fuel are present also after heating the aerosol to 350 °C which is not the case for equally sized particles formed when using the 3.5 ppm sulphur fuel. The different shapes of the particle size distributions for each of the fuels indicate that a minor change in cut-off size of the particle counter for number concentration measurements will correspond to a large difference in number of particles. The current study points out some of the difficulties encountered when trying to state an integrated value for particle emissions.

  • 19.
    Bernemyr, Hanna
    et al.
    KTH, Tidigare Institutioner                               , Maskinkonstruktion.
    Ångström, Hans-Erik
    KTH, Tidigare Institutioner                               , Maskinkonstruktion.
    Ström, Johan
    Stockholms Universitet.
    Hansson, Hans-Christen
    Stockholms Universitet.
    Study of Particulate Emissions from Heavy-Duty Diesel Engines using a Rotating Disc Diluter and a Volatility Tandem DMA (v-TDMA)2004Konferensbidrag (Refereegranskat)
  • 20. Dembinski, H.
    et al.
    Ängström, Hans-Erik
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Förbränningsmotorteknik.
    Swirl and injection pressure impact on after-oxidation in diesel combustion, examined with simultaneous combustion image velocimetry and two colour optical method2013Ingår i: SAE Technical Papers: Volume 2, 2013, S A E Inc , 2013, Vol. 2, s. 2013-01-0913-Konferensbidrag (Refereegranskat)
    Abstract [en]

    After-oxidation in Heavy Duty (HD) diesel combustion is of paramount importance for emissions out from the engine. During diffusion diesel combustion, lots of particulate matter (PM) is created. Most of the PM are combusted during the after-oxidation part of the combustion. Still some of the PM is not, especially during an engine transient at low lambda. To enhance the PM oxidation in the late engine cycle, swirl together with high injection pressure can be implemented to increase in-cylinder turbulence at different stages in the cycle. Historically swirl is known to reduce soot particulates. It has also been shown, that with today's high injection pressures, can be combined with swirl to reduce PM at an, for example, engine transient. The mechanism why the PM engine out is reduced also at high injection pressures is however not so well understood. In this work flow field data during combustion and after-oxidation together with soot and temperature measurements was combined to examine how flow field affects soot formation and oxidation. Swirl number was varied together with injection pressure and the engine tests were done in a HD optical engine. The load was set to 10 bar & 20 bar IMEP at low lambda without EGR, typically transient load points. A high speed colour camera captures picture of the combustion seen through a glass piston-bowl. The flow field was extracted with combustion image velocimetry (CIV) that traces the glowing soot particulates (or the light luminosity difference) by cross correlation between two pictures from the high speed colour camera. From the same pictures the KL factor and flame temperature were simultaneously calculated with the 2-colour method. Both CIV and the 2-colour method are line of sight optical methods that catches flow, soot and temperature from the light observed through the piston. It was found that in the after-oxidation part of the cycle, the flow in the piston bowl deviates strongly from solid body rotation (that can be assumed to be the case before injection). With increased injection pressure this deviation from solid body rotation increased at constant swirl number. When swirl number was increased, the deviation from solid body rotation increased even further. This seems to be an important factor during the after-oxidation part of the combustion by amplifying the turbulence. The flame temperature together with KL factor (a measure of soot density inside the cylinder) was also influenced when the flow field in the cylinder was changed. With increased injection pressure, from 500 bar to 1000 bar, the maximum KL was amplified during combustion with 50%, but the measured tail pipe soot was decreasing from 1.22 FSN to 0.49 FSN. This together with increased solid body deviation for the 1000 bar case, at the after-oxidation part of the combustion, leads to the conclusion: The flow field during the late part of the cycle has strong impact on tail pipe soot emissions. What was created during the diffusion combustion has less impact on the tail pipe soot compared to the flow field effects during after-oxidation.

  • 21.
    Dembinski, Henrik
    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.
    An Experimental Study of the Influence of Variable In-Cylinder Flow, Caused by Active Valve Train, on Combustion and Emissions in a Diesel Engine at Low Lambda Operation2011Konferensbidrag (Refereegranskat)
    Abstract [en]

    Spray and mixture formation in a compression ignition engine is of paramount importance for diesel combustion. In engine transient operation, when the load increases rapidly, the combustion system needs to handle low lambda (λ) operation while avoiding high particle emissions. Single cylinder tests were performed to evaluate the effect of differences in cylinder flow on combustion and emissions at typical low λ transient operation. The tests were performed on a heavy duty single cylinder test engine with Lotus Active Valve Train (AVT) controlling the inlet airflow. The required swirl number (SN) and tumble were controlled by applying different inlet valve profiles and opening either both inlet valves or only one or the other. The operating point of interest was extracted from engine transient conditions before the boost pressure was increased and investigated further at steady state conditions. The AVT enabled the resulting SN to be controlled at bottom dead centre (BDC) from ~0.3 to 6.8 and tumble from ~0.5 to 4. The fuel injection pressure was varied from 500 bar up to 2000 bar, with increments of 500 bar, for each SN and tumble setting. No exhaust gas recirculation was used in following tests. GT-POWER was used to calculate SN, tumble, and turbulent intensity with the different valve settings. The input data for the GT-POWER flow calculations were measured in a steady-state flow rig with honeycomb torque measurement.

    The main conclusion of this study was that the air flow structure in the cylinder, characterized by SN, tumble, and turbulent intensity, has a significant effect on the resulting engine combustion and emissions for the investigated range of fuel injection pressures. By increasing SN above 3, while maintaining tumble at low levels, the engine could be run with richer air/fuel mixtures without further increasing smoke emissions at injection pressures 1000 bar and above. Also, NO

    xemissions decreased at λ below 1.3; ignition delay time decreased at higher tumble and turbulent levels; and higher levels of swirl resulted in more rapid combustion, decreasing smoke emissions at injection pressures over 1000 bar. Smoke emissions increase at higher engine speeds (above 1200 rpm) and high SN (above 6). The results of this study demonstrate that the mixing process controlled by in-cylinder flow (swirl and tumble) has a dominant effect on combustion.

  • 22.
    Dembinski, Henrik
    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.
    Optical study of swirl during combustion in a CI engine with different injection pressures and swirl ratios compared with calculations2012Konferensbidrag (Refereegranskat)
    Abstract [en]

    Spray and mixture formation in a compression-ignition engine is of paramount importance in the diesel combustion process. In an ngine transient, when the load increases rapidly, the combustion system needs to handle low operation without producing high NO x emissions and large amounts of particulate matter. By changing the in-cylinder flow, the emissions and engine efficiency are affected.

    Optical engine studies were therefore performed on a heavy-duty engine geometry at different fuel injection pressures and inlet airflow characteristics. By applying different inlet port designs and valve seat masking, swirl and tumble were varied. In the engine tests, swirl number was varied from 2.3 to 6.3 and the injection pressure from 500 to 2500 bar. To measure the in-cylinder flow around TDC, particle image velocimetry software was used to evaluate combustion pictures. The pictures were taken in an optical engine using a digital high-speed camera. Clouds of glowing soot particles were captured by the camera and traced with particle image velocimetry software. The velocity-vector field from the pictures was thereby extracted and a mean swirl number was calculated. The swirl number was then compared with 1D simulation program GT-POWER and CFD based correlations. The GT-POWER simulations and CFD based correlation calculations were initiated from steady-state flow bench data on tested cylinder heads.

    The main conclusions from this study were that the mean swirl numbers, evaluated with the PIV software from combustion pictures around TDC, agreed with CFD based correlations and the low swirl numbers also correlated with the 1D-simulation program. Most of the induced swirl motion survives the compression and combustion, while the induced tumble does not survive to the late combustion phase. The tumble however, disturbs the swirl motion and offsets the swirl centre. This offset survives the compression and combustion. The diesel sprays that are injected symmetrically in the combustion chamber are thereby exposed to the swirl asymmetrically. This study also shows that the angular velocity at different piston bowl radii deviates from solid body rotation. The angular velocity is higher closer to the centre and decreases to be at the lowest value at the outer piston bowl edge. When the injection pressure is increased, the deviation from solid body rotation increases due to spray effects.

  • 23.
    Dembinski, Henrik
    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.
    Swirl and Injection Pressure Effect on Post-Oxidation Flow Pattern Evaluated with Combustion Image Velocimetry, CIV, and CFD Simulation2013Konferensbidrag (Refereegranskat)
    Abstract [en]

    In-cylinder flow pattern has been examined experimentally in a heavy duty optical diesel engine and simulated with CFD code during the combustion and the post-oxidation phase. Mean swirling velocity field and its evolution were extracted from optical tests with combustion image velocimetry (CIV). It is known that the post-oxidation period has great impact on the soot emissions. Lately it has been shown in swirling combustion systems with high injection pressures, that the remaining swirling vortex in the post-oxidation phase deviates strongly from solid body rotation. Solid body rotation can only be assumed to be the case before fuel injection. In the studied cases the tangential velocity is higher in the centre of the piston bowl compared to the outer region of the bowl. The used CIV method is closely related to the PIV technique, but makes it possible to extract flow pattern during combustion at full load in an optical diesel engine. Injection pressure was varied from 200 up to 2500 bar at 1000 rpm without EGR. Swirl was varied between 1.2 and 6.4 at BDC. The CFD simulation was a sector simulation on the same in-cylinder geometry and boundary conditions as in the optical engine.

    The main findings show that with increased injection pressure, together with swirl, the angular velocity increases in the centre of the piston bowl meanwhile the angular velocity decreases slightly in the outer region. The total angular momentum decreases slightly when injection starts and the total rotational kinetic energy increases significantly. The redistribution of the angular velocity is caused by the driving force from the injection. When the swirling bulk flow acts on the injected spray/flame, its orbit is slightly directed to the leeward side of the swirl. When the flame is directed back to the cylinder centre, by the bowl, it has thereby an offset from where it is injected. This offset together with the high flow velocity from the flame increases the angular velocity in the central region of the combustion chamber. The angular velocity in the outer part of the bowl decreases slightly when angular momentum is moved into the centre of the bowl were the velocity increases. This deviation in angular velocity has been observed in both the CFD results and in the CIV results were it survives into the post-oxidation phase with slow dissipation during the expansion stroke. The dissipation is a source for late cycle turbulence generation that affects the soot oxidation.

  • 24.
    Dembinski, Henrik
    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.
    The effects of injection pressure on swirl and flow pattern in diesel combustionIngår i: International Journal of Engine Research, ISSN 1468-0874, E-ISSN 2041-3149Artikel i tidskrift (Övrigt vetenskapligt)
  • 25.
    Dembinski, Henrik
    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.
    Razzaq, H.
    In-Cylinder Flow Pattern Evaluated with Combustion Image Velocimetry, CIV, and CFD Calculations during Combustion and Post-Oxidation in a HD Diesel Engine2013Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    In-cylinder flow pattern was evaluated during diesel combustion and post-oxidation in a heavy duty optical engine and compared with CFD calculations. In this work the recently developed optical method combustion image velocimetry (CIV) is evaluated. It was used for extracting the flow pattern during combustion and post-oxidation by tracing the glowing soot clouds in the cylinder. The results were compared with CFD sector simulation on the same heavy duty engine geometry. Load was 10 bar IMEP and injection pressure was varied in two steps together with two different swirl levels. The same variations were done in both the optical engine and in the CFD simulations.

    The main results in this work show that the CIV method and the CFD results catch the same flow pattern trends during combustion and post-oxidation. Evaluation of the CIV technique has been done on large scale swirl vortices and compared with the CFD results at different distances from the piston bowl surface. The flow field according to CIV is shown to resemble the flow quite near the optical piston bowl surface during the diffusion combustion period in the CFD results. During the after-oxidation period, the observed CIV data coincide with mean velocity data from CFD, calculated on the total depth from cylinder head to piston surface. Both methods indicate that the in-cylinder flow is strongly deviating from solid body rotation during the diffusion flame and after-oxidation period. This deviation is not so significant before injection. During the after-oxidation period, the deviation from solid body rotation increases with injection pressure.

  • 26.
    Elmqvist, Christel
    et al.
    KTH, Tidigare Institutioner                               , Maskinkonstruktion.
    Lindström, Fredrik
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.).
    Ångström, Hans-Erik
    KTH, Tidigare Institutioner                               , Maskinkonstruktion.
    Grandin, Börje
    Kalghatgi, Gautam
    Optimizing engine concepts by using a simple model for knock prediction2003Ingår i: SAE Paper 2003-01-3123, SAE , 2003Konferensbidrag (Refereegranskat)
    Abstract [en]

    The objective of this paper is to present a simulation model for controlling combustion phasing in order to avoid knock in turbocharged SI engines. An empirically based knock model was integrated in a one-dimensional simulation tool. The empirical knock model was optimized and validated against engine tests for a variety of speeds and λ . This model can be used to optimize control strategies as well as design of new engine concepts.

  • 27.
    Ericsson, Gustav
    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.
    Westin, Fredrik
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.).
    Optimizing the Transient of an SI-Engine Equipped with Variable Cam Timing and Variable Turbine2010Ingår i: SAE International Journal of Engines, ISSN 1946-3936, Vol. 3, nr 1, s. 903-915Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    As the engines of today decrease in displacement with unchanged power output, focus of today's research is on transient response. The trend of today is to use a turbocharger with high boost level. For SI-engines a regular WG turbocharger has been used, but in the future, when the boost level increases together with higher demand on the transient response, a Variable Nozzle Turbine (VNT) will be used together with Variable Valve Timing (VVT). As the degree of freedom increases, the control strategies during a transient load step will be more difficult to develop. A 1D simulation experiment has been conducted in GT Power where the transient simulation was "frozen" at certain time steps. The data from these time steps was put in a stationary simulation and the excessive energy was then bled off to obtain the same conditions for the engine in the stationary simulation as if the engine where in the middle of the transient. This method allows a faster and easier way to obtain a good control strategy for the VNT turbine and the VVT during a transient load step. The method can be used to find VNT/VVT settings strategies for the transient control with a good and robust result.

  • 28.
    Gundmalm, Stefan
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Förbränningsmotorteknik.
    Cronhjort, Andreas
    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.
    Divided Exhaust Period: Effects of Changing the Relation between Intake, Blow-Down and Scavenging Valve Area2013Ingår i: SAE World Congress 2013, 2013Konferensbidrag (Refereegranskat)
    Abstract [en]

    In a previous paper we showed the effects of applying the Divided Exhaust Period (DEP) concept on two heavy-duty diesel engines, with and without Exhaust Gas Recirculation (EGR). Main findings were improved fuel consumption due to increased pumping work, improved boost control and reduced residual gas content. However, some limitations to the concept were discovered.  In the case of high rates of short route EGR, it was apparent that deducting the EGR flow from the turbine manifold impaired optimal valve timing strategies. Furthermore, for both of the studied engines it was clear that the size and ratio of blow-down to scavenging valve area is of paramount importance for engine fuel efficiency.

    In this paper, the DEP concept has been studied together with a long route EGR system. As expected it gave more freedom to valve timing strategies when driving pressure for EGR is no longer controlled with the valve timing, as in the short route case. However, when evaluating different combinations of intake, blow-down and scavenging valve area, the optimal relation proves to be strongly dependent on the current EGR system and EGR rates. Hence, for different engine setups the trade-off between total intake and total exhaust area needs to be re-evaluated for optimal engine fuel efficiency. This paper also presents general trends in how different valve timing strategies and EGR rates affect both pumping work and boost pressure.

  • 29.
    Gundmalm, Stefan
    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).
    Cronhjort, Andreas
    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).
    Divided Exhaust Period: Effects of Changing the Relation between Intake, Blow-Down and Scavenging Valve Area2013Ingår i: SAE International Journal of Engines, ISSN 1946-3936, Vol. 6, nr 2, s. 739-750Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In a previous paper we showed the effects of applying the Divided Exhaust Period (DEP) concept on two heavy-duty diesel engines, with and without Exhaust Gas Recirculation (EGR). Main findings were improved fuel consumption due to increased pumping work, improved boost control and reduced residual gas content. However, some limitations to the concept were discovered. In the case of high rates of short route EGR, it was apparent that deducting the EGR flow from the turbine manifold impaired optimal valve timing strategies. Furthermore, for both of the studied engines it was clear that the size and ratio of blow-down to scavenging valve area is of paramount importance for engine fuel efficiency. In this paper, the DEP concept has been studied together with a long route EGR system. As expected it gave more freedom to valve timing strategies when driving pressure for EGR is no longer controlled with the valve timing, as in the short route case. However, when evaluating different combinations of intake, blow-down and scavenging valve area, the optimal relation proves to be strongly dependent on the current EGR system and EGR rates. Hence, for different engine setups the trade-off between total intake and total exhaust area needs to be re-evaluated for optimal engine fuel efficiency. This paper also presents general trends in how different valve timing strategies and EGR rates affect both pumping work and boost pressure.

  • 30.
    Gundmalm, Stefan
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Förbränningsmotorteknik.
    Cronhjort, Andreas
    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.
    Divided Exhaust Period on Heavy-Duty Diesel Engines2012Konferensbidrag (Refereegranskat)
    Abstract [en]

    Divided Exhaust Period (DEP) has previously been studied on SI engines while results fromHD diesels are scarcer. In this paper the DEP concept has been numerically simulated on two HD dieselengines; one without EGR and one with high rates of short route EGR. The aim is to reduce fuelconsumption, residual gas content and to improve boost control, while current EGR rates are maintained.

    The central idea of the DEP concept is to let the initial high energy blow-down pulse feed theturbocharger, but bypass the turbine during the latter part of the exhaust stroke when back pressuredominates the pumping work. The exhaust flow from the cylinder is divided between two exhaust manifoldsof which one is connected to the turbine, and one bypasses the turbine. The flow split betweenthe manifolds is controlled with a variable valve train system.

    Results show a reduction of pumping losses for both engine configurations. In the non-EGRcase, the DEP concept offers the possibility to control the mass flow and pressure ratio over the turbine.This allows the turbocharger to operate in a high efficiency mode for a wide range of engine loadpoints. For the EGR case, there is less freedom in control of turbine mass flow, since the blow-downphase is used for both turbine work and EGR flow. Therefore the fuel consumption benefit is reduced.

    The conclusion of this paper is that the simulations of the DEP concept show improvements toengine performance and efficiency. In the case of high EGR rates it is shown that the EGR flow shouldnot be deducted from the blow-down phase.

  • 31.
    Kalghatgi, Gautam T.
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.).
    Risberg, Per
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.).
    Ångström, Hans-Erik
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.).
    Partially pre-mixed auto-ignition of gasoline to attain low smoke and low NOx at high load in a compression ignition engine and comparison with a diesel fuel2007Ingår i: SAE technical paper series, ISSN 0148-7191Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A Swedish MK1 diesel fuel and a European gasoline of ∼95 RON have been compared in a single cylinder CI engine operating at 1200 RPM with an intake pressure of 2 bar abs., intake temperature of 40°C and 25% stoichiometric EGR at different fuelling rates and using different injection strategies. For the same operating conditions, gasoline always gives much lower smoke compared to the diesel fuel because of its higher ignition delay; this usually allows the heat release to be separate in time from the injection event. NOx can be controlled by EGR. With dual injection, for diesel fuel, there can be significant heat release during the compression stroke because of the pilot injection earlier in the compression stroke. For a fixed total fuelling rate, compared to single injection, this reduces fuel efficiency and increases the lowest achievable level of smoke. With gasoline, pilot injection helps reduce the maximum heat release rate for a given IMEP and enables heat release to occur later with low cyclic variation compared to single injection. This enables higher mean IMEP to be reached with lower smoke, NOx and maximum heat release rate compared to single injection. One of the operating points reached with gasoline with double injection had mean IMEP of 15.95 bar (stdev. 0.112 bar), AVL smoke opacity of 0.33% (FSN < 0.07), ISNOx of 0.58 g/kWh, ISFC of 179 g/kWh, ISHC of 2.9 g/kWh, ISCO of 6.8 g/kWh and peak pressure of ∼ 120 bar. At the same operating conditions, to get such low level of smoke with Swedish MK1 diesel fuel, IMEP has to be below 6.5 bar. There is scope for further improvements by increasing intake pressure and the EGR level and through optimisation of the injection and mixture preparation strategy e.g. more injection pulses and injector design e.g. more holes.

  • 32. Königsson, F.
    et al.
    Risberg, Per
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Förbränningsmotorteknik.
    Ångström, Hans-Erik
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.).
    Nozzle Coking in CNG-Diesel Dual Fuel Engines2014Ingår i: SAE technical paper series, ISSN 0148-7191, Vol. October, artikel-id 2014-01-2700Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Nozzle coking in diesel engines has received a lot of attention in recent years. High temperature in the nozzle tip is one of the key factors known to accelerate this process. In premixed CNG-diesel dual fuel, DDF, engines a large portion of the diesel fuel through the injector is removed compared to regular diesel operation. This can result in very high nozzle temperatures. Nozzle hole coking can therefore be expected to pose a significant challenge for DDF operation. In this paper an experimental study of nozzle coking has been performed on a DDF single cylinder engine. The objective was to investigate how the rate of injector nozzle hole coking during DDF operation compares to diesel operation. In addition to the nozzle tip temperature, the impact of other parameters on coking rate was also of interest. Start of injection, , diesel substitution ratio and common rail pressure were varied in two levels starting from a common baseline case, resulting in a total of 10 operating cases. These cases were run for three and a half hours in steady-state, using standard injectors and zinc contaminated diesel to accelerate the coking process. The zinc was added in form of zinc neodecanoate, similar to the practice in the standardized tests used to study nozzle coking in diesel engines. After the tests the injectors were disassembled and the steady state flow through the injector nozzles was measured to isolate the effect of nozzle hole coking. The results show significant coking from only a few hours of testing. The most challenging case was the combination of high nozzle tip temperature from DDF operation with low injection pressure. The flow loss from operation in DDF mode was far more severe compared to diesel operation. Elemental analysis of the deposits shows similar composition resulting from diesel and DDF operation. In the DDF deposits higher concentrations of elements from the engine oil were found in addition to higher carbon content. It is concluded that injector nozzle coking is a challenge which requires appropriate attention when developing DDF engines.

  • 33.
    Königsson, Fredrik
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Förbränningsmotorteknik.
    Dembinski, Henrik
    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.
    The Influence of In-Cylinder Flows on Emissions and Heat Transfer from Methane-Diesel Dual Fuel Combustion2013Ingår i: SAE International Journal of Engines, ISSN 1946-3936, Vol. 6, nr 4Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In order for premixed methane diesel dual fuel engines to meet current and future legislation, the emissions of unburned hydrocarbons must be reduced while high efficiency and high methane utilization is maintained. This paper presents an experimental investigation into the effects of in cylinder air motion, swirl and tumble, on the emissions, heat transfer and combustion characteristics of dual fuel combustion at different air excess ratios. Measurements have been carried out on a single cylinder engine equipped with a fully variable valve train, Lotus AVT. By applying different valve lift profiles for the intake valves, the swirl was varied between 0.5 and 6.5 at BDC and the tumble between 0.5 and 4 at BDC. A commercial 1D engine simulation tool was used to calculate swirl number and tumble for the different valve profiles. Input data for the simulation software was generated using a steady-state flow rig with honeycomb torque measurements. To measure heat transfer, thermocouples were fitted in the cylinder head and heat exchangers on the coolant circuit and the engine oil. The study shows that swirl has a strong effect on the heat transfer; increasing the swirl from 0.5 to 6.5 increases the heat transfer to the coolant by 50%. With regards to emissions; swirl has the effect of increasing oxidation of hydrocarbons returning from crevices. For this reason a 20% reduction of hydrocarbon emissions can be achieved by increasing the swirl from 0.4 to 3. At high λ of 1.9, combustion is very sensitive to mixing between the gas and the air. The mixing is affected by the turbulence generated over the intake valves. A difference in engine out HC emissions by a factor of two can be achieved by varying the valve lift curve and hence varying the turbulence generated during the intake event. The timing of the gas injection can also improve mixing and achieve similar results. Compared to SI, dual fuel combustion is relatively insensitive to tumble.

  • 34.
    Königsson, Fredrik
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Förbränningsmotorteknik.
    Kuyper, Johannes
    Stalhammar, Per
    Ångström, Hans Erik
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Förbränningsmotorteknik.
    The Influence of Crevices on Hydrocarbon Emissions from a Diesel-Methane Dual Fuel Engine2013Ingår i: SAE International Journal of Engines, ISSN 1946-3936, Vol. 6, nr 2, s. 751-765Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Emissions of unburned methane are the Achilles heel of premixed gas engines whether they are spark ignited or diesel pilot ignited. If the engine is operated lean, lower temperatures prevail in the combustion chamber and several of the mechanisms behind the hydrocarbon emissions are aggravated. This paper presents an experimental investigation of the contribution from combustion chamber crevices and quenching to the total hydrocarbon emissions from a diesel-methane dual fuel engine at different operating conditions and air excess ratios. It is shown that the sensitivity to a change in topland crevice volume is greater at lean conditions than at stoichiometry. More than 70% of hydrocarbon emissions at air excess ratios relevant to operation of lean burn engines can be attributed to crevices.

  • 35.
    Königsson, Fredrik
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Förbränningsmotorteknik.
    Risberg, Per
    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.
    Nozzle Coking in CNG-Diesel Dual Fuel Engines: 2014-01-27002014Konferensbidrag (Refereegranskat)
    Abstract [en]

    Nozzle coking in diesel engines has received a lot of attention in recent years. High temperature in the nozzle tip is one of the key factors known to accelerate this process. In premixed CNG-diesel dual fuel, DDF, engines a large portion of the diesel fuel through the injector is removed compared to regular diesel operation. This can result in very high nozzle temperatures. Nozzle hole coking can therefore be expected to pose a significant challenge for DDF operation.In this paper an experimental study of nozzle coking has been performed on a DDF single cylinder engine. The objective was to investigate how the rate of injector nozzle hole coking during DDF operation compares to diesel operation. In addition to the nozzle tip temperature, the impact of other parameters on coking rate was also of interest.Start of injection, λ, diesel substitution ratio and common rail pressure were varied in two levels starting from a common baseline case, resulting in a total of 10 operating cases. These cases were run for three and a half hours in steady-state, using standard injectors and zinc contaminated diesel to accelerate the coking process. The zinc was added in form of zinc neodecanoate, similar to the practice in the standardized tests used to study nozzle coking in diesel engines.After the tests the injectors were disassembled and the steady state flow through the injector nozzles was measured to isolate the effect of nozzle hole coking. The results show significant coking from only a few hours of testing. The most challenging case was the combination of high nozzle tip temperature from DDF operation with low injection pressure. The flow loss from operation in DDF mode was far more severe compared to diesel operation. Elemental analysis of the deposits shows similar composition resulting from diesel and DDF operation. In the DDF deposits higher concentrations of elements from the engine oil were found in addition to higher carbon content. It is concluded that injector nozzle coking is a challenge which requires appropriate attention when developing DDF engines.

  • 36.
    Königsson, Fredrik
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Förbränningsmotorteknik.
    Stålhammar, Per
    Ångström, Hans-Erik
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Förbränningsmotorteknik.
    Characterization and Potential of Dual FuelCombustion in a Modern Diesel Engine2011Ingår i: SAE Technical Paper 2011-01-2223, SAE International , 2011Konferensbidrag (Refereegranskat)
    Abstract [en]

    Diesel Dual Fuel, DDF, is a concept which promises the possibility to utilize CNG/biogas in a compression ignition engine maintaining a high compression ratio, made possible by the high knock resistance of methane, and the resulting benefits in thermal efficiency associated with Diesel combustion.

    A series of tests has been carried out on a single cylinder lab engine, equipped with a modern common rail injection system supplying the diesel fuel and two gas injectors, placed in the intake runners. One feature of port injected Dual Fuel is that full diesel functionality is maintained, which is of great importance when bringing the dual fuel technology to market. The objective of the study was to characterize and investigate the potential for dual fuel combustion utilizing all degrees of freedom available in a modern diesel engine.

    Increased diesel pilot proved efficient at reducing NOx emissions at low λ. Advanced combustion phasing has the potential to extend the lean limit for operation. Stoichiometric operation using high levels of EGR is identified as a promising field in conjunction with raised inlet temperature.

  • 37.
    Königsson, Fredrik
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Förbränningsmotorteknik.
    Stålhammar, Per
    AVL Sweden.
    Ångström, Hans-Erik
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Förbränningsmotorteknik.
    Combustion Modes in a Diesel-CNG Dual Fuel Engine2011Ingår i: SAE Technical Paper 2011-01-1962, 2011, Society of Automotive Engineers of Japan, Inc , 2011, s. 2387-2398Konferensbidrag (Refereegranskat)
    Abstract [en]

    Diesel Dual Fuel, DDF, is a concept where a combination of methane and diesel is used in a compression ignited engine, maintaining the high compression ratio of a diesel engine with the resulting benefits in thermal efficiency.

    One benefit of having two fuels on board the vehicle is the additional degree of freedom provided by the ratio between the fuels. This additional degree of freedom enables control of combustion phasing for combustion modes such as Homogenous Charge Compression Ignition, HCCI, and Partly Premixed Compression Ignition, PPCI. These unconventional combustion modes have great potential to limit emissions at light load while maintaining the low pumping losses of the base diesel engine.

    A series of tests has been carried out on a single cylinder lab engine, equipped with a modern common rail injection system supplying the diesel fuel and two gas injectors, placed in the intake runners. Four load points are investigated and three different types of combustion are evaluated.

    The study confirmed the desirable emission characteristics of HCCI and PPCI combustion and demonstrated the potential to control the combustion phasing by utilizing all degrees of freedom provided by a common rail injection system and two fuels.

  • 38.
    Königsson, Fredrik
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Förbränningsmotorteknik.
    Stålhammar, Per
    Ångström, Hans-Erik
    Controlling the Injector Tip Temperature in a DieselDual Fuel Engine2012Konferensbidrag (Refereegranskat)
    Abstract [en]

    Diesel Dual Fuel, DDF, is a concept where a combination of methane and diesel is used in a compression ignited engine, maintaining the high compression ratio of a diesel engine with the resulting benefits in thermal efficiency. Attention has recently been drawn to the fact that the tip of the diesel injector may reach intolerable temperatures. The high injector tip temperatures in the DDF engine are caused by the reduction in diesel flow through the injector. For dual fuel operation, as opposed to diesel, high load does not necessarily imply a high flow of diesel through the injector nozzle.

    This research investigated the factors causing high injector tip temperatures in a DDF engine and the underlying mechanisms which transfer heat to and from the injector tip. Parameter sweeps of each influential parameter were carried out and evaluated. In addition to this, a simple and useful model was constructed based on the heat balance of the injector tip.

    Decreasing the thermal resistance between the injector tip and the cooling water by inserting a copper sleeve around the injector tip has the potential to greatly reduce the injector tip temperature and effectively remove it as a limiting factor.

  • 39.
    Lindström, Fredrik
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.).
    Ångström, Hans-Erik
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.).
    Kalgathgi, Gautam
    Elmqvist Möller, Christel
    An empirical SI combustion model using laminar burning velocity correlations2005Ingår i: SAE transactions, ISSN 0096-736X, Vol. 114, nr 4, s. 833-846Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Predictive simulation models are needed in order to exploit the full benefits of 1-D engine simulation. Simulation model alterations such as cam phasing affect the gas composition and gas state in the cylinders and have an effect on the combustion. Modelling of these effects is particularly important when the engine is knock limited. A knock model, able to phase the combustion towards the knock limit, was previously developed by the authors. A major challenge in such knock models is to predict the pressure and temperature evolution in the end-gas accurately through an adequate combustion model. The Wiebe function is often used to model the combustion in Sl engine simulations, owing to its ease of use and computational efficiency. The Wiebe function simply imposes a curve shape for the fuel burn rate and the parameters are easily determined from calculated heat release. Detailed models of turbulent combustion also exist which require more knowledge or assumptions about combustion chamber turbulence. The combustion model proposed in this paper uses existing correlations of laminar burning velocity to predict the parameters of the Wiebe function relative to a base operating condition. The model aims at predicting combustion at high load operation. Experimental and simulation data from a gasoline fuelled 4-cylinder turbo charged port injected spark ignition engine are used to correlate the Wiebe function parameters dependence on laminar burning velocity.

  • 40.
    Lindström, Mikael
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Förbränningsmotorteknik.
    Westlund, Anders
    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.
    A study of combustion and emission formation characteristics during production engine transients using optical diagnostics2011Ingår i: Proceedings of the Institution of mechanical engineers. Part D, journal of automobile engineering, ISSN 0954-4070, E-ISSN 2041-2991, Vol. 225, nr D9, s. 1290-1303Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In order to identify some of the special combustion and emission formation phenomena that occur in a turbocharged heavy-duty diesel engine during transient operation, the transient strategy of a production engine has been characterized at four different engine speeds. From each transient some points have been selected for further investigation by recreating these load points as steady-state points in a single-cylinder engine. This allows the emissions to be measured with a high degree of accuracy. An endoscope which makes it possible to evaluate flame temperatures was used in both engines. An empirically derived method of calculating nitric oxide (NO) formation from a combination of measured flame temperature, calculated gas temperature, and heat release rate has been developed and applied. This provides an increased understanding of combustion and emission formation phenomena during transient operation. An optical engine was also used to provide a full combustion chamber view for some of the operating points, and a specially developed software was used to calculate temperature distributions based on high-speed camera colour information. The NO formation formula was applied on these images, which resulted in spatially resolved NO formation distributions.

  • 41.
    Lindström, Mikael
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Maskinkonstruktion (Avd.).
    Ångström, Hans- Erik
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Maskinkonstruktion (Avd.).
    A Study of Hole Properties in Diesel Fuel Injection Nozzles and its Influence on Smoke Emissions2008Ingår i: Proceedings Conference on Thermo- and Fluid Dynamic Processes in Diesel Engines, 2008Konferensbidrag (Refereegranskat)
  • 42.
    Lindström, Mikael
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Maskinkonstruktion (Avd.).
    Ångström, Hans- Erik
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Maskinkonstruktion (Avd.).
    Development of a Fuel Spray Impulse Measurement Device and Correlation with Time Resolved Mass Flow2009Ingår i:  SAE Technical Paper 2009-01-1880, SAE International , 2009Konferensbidrag (Refereegranskat)
    Abstract [en]

    The fuel injection process plays an important role in the combustion and emission formation processes of the DI diesel engine. One important fuel spray characteristic is the spray impulse. The most commonly used method to measure fuel spray impulse is the impingement method where the fuel spray impinges perpendicularly on the surface of a force transducer. This work deals with the theoretical background of such measurements as well as with developing and testing some different impulse measurement setups. The measured impulse is compared to measurements of the instantaneous mass flow and theoretical flow calculations. When measuring the impulse by impingement on the transducer membrane a fuel temperature related measurement error was encountered. This problem was solved by gluing a strike plate to the transducer membrane. The plate shielded the membrane from direct contact with the fuel. Initially plates made out of aluminum were used, they were however found to be sensitive to erosion. After a number of injections a small pit was formed and this led to an overestimation of the impulse as the fuel more effectively was reflected back towards the direction where it came from. It is crucial for the accuracy of the method that the spent fuel exits the plate perpendicularly, if some of the fuel bounces back towards the direction where it comes from the spray impulse is overestimated. With a flat strike plate it is difficult to be sure that all the spent fuel exits the plate perpendicularly. Therefore a plate with a rotationally symmetrical curvature which allows a gradual and thus more controlled direction change was manufactured and evaluated. When the injection rate of an injector is characterized using a conventional rate tube a number of problems are caused by pressure fluctuations in the fuel volume inside the rate tube. The measurements are disturbed by superimposed fluctuations which are especially problematic when small post injections are to be evaluated. The post injection rate can be disturbed by fluctuations introduced by the main injection, such fluctuations does not occur with impulse measurements. The new impulse measurement device produces measurements with high precision in both rate shape and absolute value. Because of this it is well suited for injection rate evaluation and when a high precision value of fuel spray impulse is required, for instance when calculating nozzle flow loss factors. Flow calculations based on the instantaneous mass flow and the fuel spray impulse are made.

  • 43.
    Lindström, Mikael
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Maskinkonstruktion (Avd.).
    Ångström, Hans-Erik
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.).
    A study of in-cylinder fuel spray formation and its influence on exhaust emissions using an optical diesel engine2010Ingår i: SAE Technical Papers, 2010, nr 01-1498Konferensbidrag (Refereegranskat)
    Abstract [en]

    Increasingly stringent emission legislation as well as increased demand on fuel efficiency calls for further research and development in the diesel engine field. Spray formation, evaporation and ignition delay are important factors that influence the combustion and emission formation processes in a diesel engine. Increased understanding of the mixture formation process is valuable in the development of low emission, high efficiency diesel engines. In this paper spray formation and ignition under real engine conditions have been studied in an optical engine capable of running close to full load for a real HD diesel engine. Powerful external lights were used to provide the required light intensity for high speed camera images in the combustion chamber prior to ignition. A specially developed software was used for spray edge detection and tracking. The software provides crank angle resolved spray penetration data. The images also provide data of ignition delay, ignition location and premixed flame propagation. The evaluation was made for an array of engine operation points with variations in fuel rail pressure, injection timing, boost pressure and charge air temperature. The influence of using pilot injections has also been investigated. This set of experiments makes it possible to analyze the impact of the various engine parameters on the spray formation and ignition processes. Some of the results are compared with the exhaust emission measurements in order to provide an insight into how the emission formation process is influenced by the spray formation and ignition processes.

  • 44.
    Lindström, Mikael
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Maskinkonstruktion (Avd.).
    Ångström, Hans-Erik
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Maskinkonstruktion (Avd.).
    In-Flame Evaluation of Emission Formation in Optical and Metal Engine Using High Speed Camera and Endoscope2010Ingår i: THIESEL 2010, 2010Konferensbidrag (Refereegranskat)
  • 45.
    Reifarth, Simon
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Centra, Competence Center for Gas Exchange (CCGEx).
    Kristensson, E.
    Borggren, J.
    Sakowitz, Alexander
    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), Centra, Competence Center for Gas Exchange (CCGEx).
    Analysis of EGR/Air Mixing by 1-D Simulation, 3-D Simulation and Experiments2014Ingår i: SAE technical paper series, ISSN 0148-7191, Vol. 2014-OctoberArtikel i tidskrift (Refereegranskat)
    Abstract [en]

    The use of EGR for NO<inf>X</inf> reduction is today a standard technology for diesel engines. The mixing of air and EGR is an important issue, especially for high-pressure EGR-systems. An uneven distribution of EGR between the cylinders can lead to higher overall engine emissions when some cylinders produce more soot, others more NO<inf>X</inf> than they would with a perfectly even distribution. It is therefore important to understand the processes that control the mixing between air and EGR. The mixing is influenced by both the geometry of the mixing area and the pulsating nature of the flow. The aim of this work is to point out the high importance of the pulses present in the EGR-flow. By simulation in 1-D and 3-D as well as by a fast measurement method, it is shown that the EGR is transported in the air flow in packets. This implies that the timing between intake valve opening and the positioning of the EGR packets has a high influence of the distribution of EGR between the cylinders. The ability of 1-D and 3-D simulation to predict the behavior is evaluated. It is shown how standard 1-D simulations fail to predict the pulsation effects. Furthermore, it is shown how 1-D models can be modified to give results reasonably close to the 3-D simulation results.

  • 46.
    Reifarth, Simon
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Förbränningsmotorteknik.
    Kristensson, Elias
    Lund University.
    Borggren, Jesper
    Lund University.
    Sakowitz, Alexander
    KTH, Skolan för teknikvetenskap (SCI), Mekanik.
    Ångström, Hans-Erik
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Förbränningsmotorteknik.
    Analysis of EGR/Air Mixing by 1-D Simulation, 3-D Simulation and ExperimentsArtikel i tidskrift (Övrigt vetenskapligt)
    Abstract [en]

    The use of EGR for NOX reduction is today a standard technology for diesel engines. The mixing of air and EGR is an important issue, especially for high-pressure EGR systems. Anuneven distribution of EGR between the cylinders can lead tohigher overall engine emissions when some cylinders producemore soot, others more NOX than they would with a perfectlyeven distribution.It is therefore important to understand the processes thatcontrol the mixing between air and EGR. The mixing isinfluenced by both the geometry of the mixing area and thepulsating nature of the flow.The aim of this work is to point out the high importance of thepulses present in the EGR-flow. By simulation in 1-D and 3-Das well as by a fast measurement method, it is shown that theEGR is transported in the air flow in packets. This implies thatthe timing between intake valve opening and the positioning ofthe EGR packets has a high influence of the distribution ofEGR between the cylinders.The ability of 1-D and 3-D simulation to predict the behavior isevaluated. It is shown how standard 1-D simulations fail topredict the pulsation effects. Furthermore, it is shown how 1-Dmodels can be modified to give results reasonably close to the3-D simulation results.

  • 47.
    Reifarth, Simon
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Centra, Competence Center for Gas Exchange (CCGEx).
    Rajagopal, Vijayaraghunathan
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.).
    Gritzun, Krister
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.).
    Ångström, Hans-Erik
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.).
    Measuring and Simulating EGR-Distribution on a HD-Diesel Engine2014Ingår i: SAE technical paper series, ISSN 0148-7191, Vol. 2014-OctoberArtikel i tidskrift (Refereegranskat)
    Abstract [en]

    The distribution of EGR between the cylinders of an internal combustion engine has been shown to have large impact on the engine emissions. Especially at high EGR, the combustion reacts sensibly to variations in the EGR-rate. A cylinder that receives excessive EGR produces soot emissions while a cylinder with too little EGR has increased NO<inf>X</inf>-formation. It is therefore important to have knowledge about the mixing of air and EGR in an engine. This study compares two different EGR-mixing measurement methods. The first is based on CO<inf>2</inf> measurement with standard probes, placed at 36 different locations in the intake manifold of the engine. The second method uses a laser beam and a detector to gain information about the mixing with a high time-resolution. Additionally, 1-D simulations are used to gain information about the mixing process. To vary the mixing process on the engine, two different air/EGR mixers are used and their mixing performance is evaluated.

  • 48.
    Reifarth, Simon
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Förbränningsmotorteknik.
    Rajagopal, Vijayaraghunathan
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Förbränningsmotorteknik.
    Gritzun, Krister
    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.
    Measuring and simulating EGR-distribution on a HD-diesel engineIngår i: SAE technical paper series, ISSN 0148-7191Artikel i tidskrift (Övrigt vetenskapligt)
    Abstract [en]

    The distribution of EGR between the cylinders of an internalcombustion engine has been shown to have large impact onthe engine emissions. Especially at high EGR, the combustionreacts sensibly to variations in the EGR-rate. A cylinder thatreceives excessive EGR produces soot particles while acylinder with too little EGR has increased NOX-emission. It istherefore important to have knowledge about the mixing in anengine.This study compares two different EGR-mixing measurementmethods. The first is based on CO2 measurement withstandard probes, placed at 36 different locations in the engine.The second method uses a laser beam and a detector to gaininformation about the mixing with a high time-resolution.Additionally, 1-D simulations are used to gain informationabout the mixing process.To vary the mixing process on the engine, two differentair/EGR mixers are used and their mixing performance isevaluated.

  • 49.
    Reifarth, Simon
    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).
    Tillmark, Nils
    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).
    Exergy and energy analysis of high-pressure and low-pressure exhaust gas recirculation system of a diesel engine2015Ingår i: International Journal of Exergy, ISSN 1742-8297, E-ISSN 1742-8300, Vol. 17, nr 3, s. 313-334Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The emission legislation for internal combustion engines is becoming increasingly stringent. Exhaust gas recirculation (EGR) is an important tool for emission control in modern diesel engines. This study compares the most common EGR-systems, high-pressure and low-pressure EGR, and focuses on single components. To analyse the gas exchange system, both energy and exergy analysis methods can be used. In this study, both methods are compared and specific advantages and disadvantages are shown. It is shown that the exergy analysis contains useful information for engine development regarding the efficiency of single components and their influence on the entire systems performance.

  • 50.
    Reifarth, Simon
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Förbränningsmotorteknik.
    Tillmark, Nils
    KTH, Skolan för teknikvetenskap (SCI), Mekanik.
    Ångström, Hans-Erik
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Förbränningsmotorteknik.
    Exergy and Energy Analysis of HP and LP EGR-systemArtikel i tidskrift (Övrigt vetenskapligt)
    Abstract [en]

    The emission legislation throughout the world is getting moreand more stringent. Especially in the US and Europe, dieselengine manufacturers are facing big challenges in order tokeep their engine emissions within the limits. In addition totraditional legislation of harmful emissions, the emission ofCO2, i.e. the fuel consumption, is starting to be subject of newlegislation. Many measures that control the harmful emissionscounteract the reduction of fuel consumption. After treatmentsystems for example increase backpressure, thus lowering theengine efficiency.Exhaust gas recirculation (EGR) is an important tool foremission control in modern diesel engines. The EGR-loopinduces some pumping losses thus decreasing the overallengine efficiency. Many studies have been published that aimat minimizing these losses. The use of a low-pressure EGRloop is one of the most common ways to alternate the system.This study compares a low-pressure (LP) and a high-pressureHP) EGR-system with focus on single components.To analyze the gas exchange system, both energy and exergybalance methods can be used. In this study, both methods arecompared and specific advantages and disadvantages areshown. It is shown that the exergy analysis contains usefulinformation for engine development regarding the efficiencyof single components and their influence on the entire systems performance.

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