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Acoustic In-duct Characterization of Fluid Machines with Applications to Medium Speed IC-engines
KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL. VTT Technical Research Centre of Finland Ltd. (Flow acoustics)
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The unwanted sound, noise, can lead to health problems, e.g. hearing loss and stress-related problems. A pre-knowledge of noise generation by machines is of great importance due to the ever-shorter product development cycles and stricter noise legislation. The noise from a machine radiates to the environment indirectly via the foundation structure and directly via the surrounding fluid. A fluid machine converts the energy from the fluid into mechanical energy or vice versa. Examples of the fluid machines are internal combustion engines (IC-engines), pumps, compressors, and fans. Predicting and controlling noise from a fluid machine requires a model of the noise sources themselves, i.e. acoustic source data. In the duct systems connected to the fluid machines, the acoustic source interacts strongly with the system boundaries, and the source characteristics must be described using in-duct methods.

Above a certain frequency, i.e. first non-plane wave mode cut-on frequency, the sound pressure varies over the duct cross-section and non-plane waves are introduced. For a number of applications, the plane wave range dominates and the non-plane waves can be neglected. But for machines connected to large ducts, the non-plane wave range is also important. In the plane wave range, one-dimensional process simulation software can be used to predict, e.g. for IC-engines, the acoustic in-duct source characteristics. The high frequency phenomena with non-plane waves are so complicated, however, that it is practically impossible to simulate them accurately. Thus, in order to develop methods to estimate the sound produced, experimental studies are also essential.

This thesis investigates the acoustic in-duct source characterization of fluid machines with applications to exhaust noise from medium speed IC-engines.  This corresponds to large engines used for power plants or on ships, for which the non-plane wave range also becomes important. The plane wave source characterization methods are extended into the higher frequency range with non-plane waves. In addition, methods to determine non-plane wave range damping for typical elements in exhaust systems, e.g. after-treatment devices, are discussed.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2015. , xi, 63 p.
Series
TRITA-AVE, ISSN 1651-7660 ; 2015:86
Keyword [en]
in-duct, acoustic source, source characterization, IC-engine
National Category
Fluid Mechanics and Acoustics
Identifiers
URN: urn:nbn:se:kth:diva-177341ISBN: 978-91-7595-765-4 (print)OAI: oai:DiVA.org:kth-177341DiVA: diva2:872313
Public defence
2015-12-10, sal F3, Lindstedtsvägen 26, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20151119

Available from: 2015-11-19 Created: 2015-11-18 Last updated: 2015-12-14Bibliographically approved
List of papers
1. Acoustic Source Characterization for Prediction of Medium Speed Diesel Engine Exhaust Noise
Open this publication in new window or tab >>Acoustic Source Characterization for Prediction of Medium Speed Diesel Engine Exhaust Noise
2014 (English)In: Journal of Vibration and Acoustics-Transactions of the ASME, ISSN 1048-9002, E-ISSN 1528-8927, Vol. 136, no 2, 021008- p.Article in journal (Refereed) Published
Abstract [en]

To achieve reliable results when simulating the acoustics of the internal combustion engine (IC-engine) exhaust system and its components, the source characteristics of the engine must be known. In the low frequency range only plane waves propagate and then one-port source data can be determined using, for example, the acoustic multiload method. For the medium speed IC-engines used in power plants and ships, the exhaust duct noise often needs to be analyzed up to 10 kHz, i.e., far beyond the plane wave range, and it is then more appropriate to use acoustic power to characterize the source. This power should ideally be measured under reflection-free conditions in the exhaust duct. The results from an earlier study showed that a suitable way to characterize the source for any frequency is to determine the in-duct sound power by extending the plane wave formulation with frequency band power weighting factors. The aim of this study is to apply this high frequency range method in situ to a real test engine. Another aim is to define, theoretically, how to combine the source data in the low frequency plane wave range with those in the high frequency nonplane wave range using a source sound power formulation.

Keyword
Duct, System
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-143972 (URN)10.1115/1.4026138 (DOI)000332223800008 ()2-s2.0-84903739891 (Scopus ID)
Note

QC 20140407

Available from: 2014-04-07 Created: 2014-04-04 Last updated: 2017-12-05Bibliographically approved
2. Procedure to estimate the in-duct sound power in the high frequency range with non-plane waves
Open this publication in new window or tab >>Procedure to estimate the in-duct sound power in the high frequency range with non-plane waves
2012 (English)In: ASME 2012 Noise Control and Acoustics Division Conference at InterNoise 2012, ASME Press, 2012, 181-191 p.Conference paper, Published paper (Refereed)
Abstract [en]

The acoustic characterization of fluid machines, e.g., internal combustion engines, compressors, or fans is of great importance when designing the connected duct systems and its silencers. For machines connected to large ducts where also the non-plane wave range is important, for instance large diesels and gas turbines, a suitable way to characterize the source is to determine the sound power under reflection free conditions. For the low frequency plane wave range in-duct sound power can be measured with the widely used two microphone method. The goal of this study is to investigate how, starting from the two-microphone approach, a suitable wall mounted microphone configuration can be defined and used to estimate the propagating in-duct sound power also beyond the plane wave range. For this purpose an acoustic source test-rig was built and numerical simulations were also conducted. The in-duct sound power from monopole, dipole, and quadrupole source types was determined using twelve wall mounted microphones and cross-spectra averaging methods. The in-duct results were compared against sound power measured using the reverberation room method (ISO 3741). Based on the simulations and the experimental results the best microphone positions and weighting factors were determined.

Place, publisher, year, edition, pages
ASME Press, 2012
Keyword
Acoustic characterization, Acoustic sources, Averaging method, Frequency ranges, Microphone positions, Reverberation rooms, Two-microphone methods, Weighting factors
National Category
Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:kth:diva-144786 (URN)10.1115/NCAD2012-0531 (DOI)000323912200019 ()2-s2.0-84884857493 (Scopus ID)978-079184532-5 (ISBN)
Conference
ASME 2012 Noise Control and Acoustics Division Conference at InterNoise 2012, NCAD 2012; New York City, NY; United States; 19 August 2012 through 22 August 2012
Note

QC 20140519

Available from: 2014-05-19 Created: 2014-04-29 Last updated: 2015-11-19Bibliographically approved
3. Acoustic Simulation of Medium Speed IC-Engine Exhaust Gas After Treatment Devices with Substrate
Open this publication in new window or tab >>Acoustic Simulation of Medium Speed IC-Engine Exhaust Gas After Treatment Devices with Substrate
2014 (English)Other (Refereed)
Abstract [en]

The after treatment devices (ATD) used in internal combustion engine (IC-engine) exhaust systems are mainly designed with emphasis on emission control, i.e. chemical efficiency, while paying less attention to the acoustic performance. In automotive applications, the duct diameters are so small that studying the acoustic wave propagation only in the plane wave frequency range is usually sufficient. In the case of medium speed IC-engines, used for example in power plants and ships, the three dimensional acoustic phenomena must also be taken into account. The main elements of the medium speed IC-engine ATD are the selective catalytic reducer (SCR) and oxidation catalyst (OC), which are based on a large amount of coated channels, i.e. the substrates. The number and type of the substrates depends not only on the regional environment legislations but also on the engine type. In this study the acoustic attenuation of a medium speed IC-engine ATD is simulated and the results are compared with measurements. The focus is in the low and mid frequency range. That is, the three dimensional waves inside the ATD are taken into account whereas only the plane waves are assumed to propagate at the inlet and outlet ports. The paper also discusses how to extend the classical one dimensional two-port solution into the higher frequencies. Using the computationally effective two-port solution in a wider frequency range is of great importance, e.g., when searching the acoustically optimal substrate configuration.

Place, publisher, year, pages
SAE International, 2014
Series
SAE Technical Paper
National Category
Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:kth:diva-177337 (URN)10.4271/2014-01-2057 (DOI)
Note

QC 20151214

Available from: 2015-11-18 Created: 2015-11-18 Last updated: 2015-12-14Bibliographically approved
4. Determination of in-duct sound power beyond the plane wave range using wall-mounted microphones
Open this publication in new window or tab >>Determination of in-duct sound power beyond the plane wave range using wall-mounted microphones
2015 (English)In: Applied Acoustics, ISSN 0003-682X, E-ISSN 1872-910X, Vol. 99, 24-30 p.Article in journal (Refereed) Published
Abstract [en]

When studying the acoustic wave propagation in a duct, the frequency range can be divided into the low frequency plane wave range and the high frequency range with non-plane waves. In the low frequency range, the wave propagation is one-dimensional and the governing equations are rather simple. The larger the duct, the lower the frequency limit of the non-plane waves. Therefore, also taking into account the three-dimensional acoustic wave propagation is important, especially when considering the duct systems used in large machines. In practice often a harsh environment and immobile structures restrict the use of standardized noise measuring methods. For instance to characterize the exhaust noise of medium speed internal combustion engines (IC-engines) in situ, the in-duct sound pressures are measured using wall-mounted microphones. Then the low frequency range source sound power can be estimated by wave decomposition ("two-microphone method"). Often a three-microphone array is used to cover a sufficiently large frequency range. One way to formulate the sound pressure and sound power relationship in the high frequency range is to weight the sound pressures at the duct wall in one-third octave bands. The aim of this study is to extend the classical plane wave formulation by determining these weighting factors, so that a three-microphone array also can be used beyond the plane wave range. The results from numerical approach are compared to experimental data.

Keyword
Exhaust noise, IC-engine, In-duct, Non-plane waves, Sound power
National Category
Other Engineering and Technologies
Identifiers
urn:nbn:se:kth:diva-170221 (URN)10.1016/j.apacoust.2015.05.003 (DOI)000358969200003 ()2-s2.0-84930958691 (Scopus ID)
Note

QC 20150630

Available from: 2015-06-30 Created: 2015-06-29 Last updated: 2017-12-04Bibliographically approved
5. Acoustic source data for medium speed IC-engines
Open this publication in new window or tab >>Acoustic source data for medium speed IC-engines
2012 (English)In: Journal of Vibration and Acoustics-Transactions of the ASME, ISSN 1048-9002, E-ISSN 1528-8927, Vol. 134, no 5, 051008- p.Article in journal (Refereed) Published
Abstract [en]

Knowledge of the acoustic source characteristics of internal combustion engines (IC-engines) is of great importance when designing the exhaust duct system and its components to withstand the resulting dynamic loads and to reduce the exhaust noise emission. The goal of the present study is to numerically and experimentally investigate the medium speed IC-engine acoustic source characteristics, not only in the plane wave range but also in the high frequency range. The low frequency acoustic source characteristics were predicted by simulating the acoustic multiload measurements by using a one-dimensional process simulation code. The low frequency in-duct exhaust noise of a medium speed IC-engine can be quite accurately predicted. The high frequency source data is estimated by averaging the measured acoustic pressures with different methods; using the simple cross-spectra averaging method seems promising in this instance.

Keyword
Acoustic noise measurement, Acoustics, Dynamic loads, Internal combustion engines
National Category
Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:kth:diva-105432 (URN)10.1115/1.4006415 (DOI)000312366900008 ()2-s2.0-84867299975 (Scopus ID)
Funder
TrenOp, Transport Research Environment with Novel Perspectives
Note

QC 20121122

Available from: 2012-11-22 Created: 2012-11-21 Last updated: 2017-12-07Bibliographically approved
6. Simulation of the particle oxidation catalyst POC (R) acoustics
Open this publication in new window or tab >>Simulation of the particle oxidation catalyst POC (R) acoustics
2014 (English)In: Noise Control Engineering Journal, ISSN 0736-2501, E-ISSN 2168-8710, Vol. 62, no 5, 368-374 p.Article in journal (Refereed) Published
Abstract [en]

The reduction of the exhaust noise from internal combustion engine (IC-engine) is mainly managed by proper silencer design, while less attention is paid to the acoustic performance of the after treatment devices (ATD). It is known from the earlier studies, that the transmission loss of a typical ATD unit can be quite significant. An ATD unit for diesel engines is classically assembled from several specific parts such as selective catalytic reducers (SCR), diesel oxidation catalysts (DOC) and diesel particulate filters (DPF). One new alternative to the conventional DPF is the particle oxidation catalyst (POC (R)). The POC (R) substrate studied in this paper is of type POC-X, which consists of fine, corrugated metallic wire mesh screens piled askew and rolled into a cylindrical shape. In this paper acoustic two-port simulation models for POC-X are proposed. First model is built up starting from the classical Kirchhoff solution for prediction of the acoustic wave attenuation in narrow channels. According to experimental studies, correction factors to the narrow channel two-port model are proposed. Second model is derived by treating the filter as a lumped acoustic resistance, dependent on the flow resistivity coefficients obtained from the pressure drop measurements.

Keyword
Acoustics, Catalysts, Catalytic oxidation, Diesel engines, Engines, Oxidation, Pressure drop, Acoustic performance, Acoustic resistance, After treatment devices, Cylindrical shapes, Diesel oxidation catalyst, Diesel particulate filters, Oxidation catalysts, Pressure drop measurements
National Category
Other Engineering and Technologies
Identifiers
urn:nbn:se:kth:diva-158456 (URN)10.3397/1/376236 (DOI)000346128200009 ()2-s2.0-84912530026 (Scopus ID)
Note

QC 20150108

Available from: 2015-01-08 Created: 2015-01-08 Last updated: 2017-12-05Bibliographically approved

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  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
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  • Other locale
More languages
Output format
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