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Studies of flow duct acoustics with applications to turbocharged engines
KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL. (MWL (The Marcus Wallenberg Lab))
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

A number of experimental and theoretical studies, performed in the field of technical flow duct acoustics are presented in this thesis. The acoustical methods treated are implemented on turbocharged IC-engines and engine gas exchange system components.

A new method based on the well-known two-load technique has been developed. The method was applied to characterise the source data of various piston-engines with non-linear behaviour including a 6 cylinder turbo-charged truck diesel engine. The source characterisation results were compared to the results obtained using the linear two-load technique. It was demonstrated that the new non-linear multi-load technique gives improved results when the source is slightly non-linear.

The use of active one-port models has been tested to characterize an air terminal device (ATD) as a source of flow generated noise. In order to predict the noise generation at different operating points of the device a scaling law was derived and verified. In the experimentally derived scaling law a flow speed dependence of 3 was found for the narrow band spectra, corresponding to a dipole-like behavior of the source in the plane wave range. The proposed technique was validated successfully and the results indicated a good prediction of in-duct sound generation by the air terminal device.

Sound reflection from hot flow duct openings has been investigated experimentally. The reflection coefficient was measured for flow temperatures up to 500 ºC and jet velocities up to 108m/s. The results have been compared with famous Munt’s theory. It was concluded that at low Mach number and Helmholz number cases the results agree well with the Munt’s model. This was the first experimental validation of the theory for hot flow conditions.

Experimental procedures to determine the sound transmission through automotive turbo-charger compressors were developed and described in detail. An overview of a unique turbocharger testing facility established at KTH CICERO in Stockholm is given. The facility can be used to measure acoustic two-port data for turbo-compressors. Results from measurements on a passenger car turbo-compressor are presented and the influence of operating conditions on the sound transmission is discussed. Current wave action models developed in CMT for computation of the gas exchange processes in I.C. engines have been implemented to determine the acoustic wave transmission through the turbo- compressor. The models are validated with the experimental data and the results are presented for different operating conditions of a Volvo passenger car turbo-compressor.

Place, publisher, year, edition, pages
Stockholm: KTH , 2009. , 142 p.
Series
Trita-AVE, ISSN 1651-7660 ; 2009:29
Keyword [en]
IC-engine, turbocharger, duct termination, flow duct, exhaust system, inlet system, acoustic source, one-port, two-port, source model, transmission loss, two-port matrix, reflection coefficient, source strength, multi-load method
National Category
Fluid Mechanics and Acoustics
Identifiers
URN: urn:nbn:se:kth:diva-10590OAI: oai:DiVA.org:kth-10590DiVA: diva2:220198
Public defence
2009-06-05, Sal D3, Lindstedtsvägen 5, KTH, Stockholm, 13:30 (English)
Opponent
Supervisors
Note
QC 20100809Available from: 2009-06-01 Created: 2009-05-29 Last updated: 2010-08-09Bibliographically approved
List of papers
1. Modified multi-load method for nonlinear source characterisation
Open this publication in new window or tab >>Modified multi-load method for nonlinear source characterisation
2007 (English)In: Journal of Sound and Vibration, ISSN 0022-460X, E-ISSN 1095-8568, Vol. 299, no 4-5, 1094-1113 p.Article in journal (Refereed) Published
Abstract [en]

Linear frequency domain prediction codes are useful for calculation of low-frequency sound transmission in duct and pipe systems. To calculate insertion loss of mufflers or the level of radiated sound information about the acoustic source is needed. The source model used in the low-frequency plane wave range is the linear time invariant one-port model. The acoustic source data is usually obtained from experimental tests where multi-load methods and especially the two-load method are most commonly used. The exhaust pulsations of for example an IC-engine are of high level, and the engine is not a perfectly linear and time invariant source. It is therefore of interest to develop source models and experimental techniques that try to take this nonlinearity into account. In this paper a modified version of the two-load method to improve the characterisation of nonlinear acoustic one-port sources has been developed and tested. Simulation results as well as experimental data from various source configurations for a modified compressor and experimental data from 6-cylinder turbocharged truck diesel engine were used to validate the method. The influence of parameters controlling the linearity of the system was investigated. The time-variance of the source model was varied and the accuracy of source characterisation results using the two-load method and the modified two-load method was evaluated.

Keyword
high-intensity sound, one-port sources, fluid machines, duct
National Category
Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:kth:diva-16201 (URN)10.1016/j.jsv.2006.08.013 (DOI)000242769100024 ()2-s2.0-33750624594 (Scopus ID)
Note

QC 20100525

Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2017-12-12Bibliographically approved
2. Characterization of air terminal device noise using acoustic 1-port source models
Open this publication in new window or tab >>Characterization of air terminal device noise using acoustic 1-port source models
2007 (English)In: Journal of Sound and Vibration, ISSN 0022-460X, E-ISSN 1095-8568, Vol. 300, no 05-mar, 727-743 p.Article in journal (Refereed) Published
Abstract [en]

A measurement method to characterize a standard air terminal device as an acoustic 1-port source has been tested and validated. The low-frequency noise generated by flow separation in the device and radiated to a reverberation room has been measured, together with pressure auto- and cross-spectra inside the connected duct. A 1-port source model with parameters derived from the in-duct data was then created. For the source strength part a scaling law was derived showing dipole dependence for the flow speed exponent. To validate the 1-port model and to prove its ability to predict flow noise generation, measurements were performed on a modified duct system.

Keyword
sound, flow, ducts
National Category
Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:kth:diva-16327 (URN)10.1016/j.jsv.2006.08.035 (DOI)000243561200017 ()2-s2.0-33845886958 (Scopus ID)
Note
QC 20100525Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2017-12-12Bibliographically approved
3. Sound reflection at an open end of a circular duct exhausting hot gas
Open this publication in new window or tab >>Sound reflection at an open end of a circular duct exhausting hot gas
2008 (English)In: Noise Control Engineering Journal, ISSN 0736-2501, E-ISSN 2168-8710, Vol. 56, no 2, 107-114 p.Article in journal (Refereed) Published
Abstract [en]

Sound reflection from hot flow duct openings is a classical problem in acoustics. In practice this is important for effective modelling and prediction off noise radiation from engine exhaust systems, burner pipelines, exhaust nozzles etc. Despite several experimental and theoretical investigations in the field, there is still limited experimental data available to validate the existing theory. In the present study, experimental investigations of plane acoustic wave reflections at duct openings where a hot jet flows into relatively cold surrounding media have been carried out. Heated air with well determined and homogenous chemical consistency along the duct axis was used as a testing media inside the duct during the experiments. The studied jet temperatures exhausting from the pipe ranged from room temperature up to 500 degrees C. The standard two-microphone technique was applied to determine the reflection properties at the duct opening. The experimental results for the reflection coefficient magnitude and phase have been compared with Munt's theory and good correlation was found. This result is a first experimental validation of the theory for hot flow conditions.

Keyword
Acoustic variables control; Acoustic waves; Acoustics; Environmental engineering; Exhaust systems (engine); Photoacoustic effect; Pipelines; Reflection; Standards; Well testing
National Category
Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:kth:diva-19427 (URN)10.3397/1.2898681 (DOI)000256460000002 ()
Note
QC 20100806Available from: 2010-08-06 Created: 2010-08-06 Last updated: 2017-12-12Bibliographically approved
4. Sound Reflection from Subsonic Flow Duct Termination Exhausting Hot Jet
Open this publication in new window or tab >>Sound Reflection from Subsonic Flow Duct Termination Exhausting Hot Jet
2008 (English)In: Proceedings of the 37th International Congress and Exhibition on Noise Control Engineering (INTER-NOISE 2008), Shanghai, China, 26-29 October, 2008., 2008Conference paper, Published paper (Refereed)
National Category
Fluid Mechanics and Acoustics Vehicle Engineering
Identifiers
urn:nbn:se:kth:diva-19428 (URN)
Note
QC 20100806Available from: 2010-08-06 Created: 2010-08-06 Last updated: 2010-08-09Bibliographically approved
5. Experimental Determination of Sound Transmission Through Turbo-Compressors
Open this publication in new window or tab >>Experimental Determination of Sound Transmission Through Turbo-Compressors
2009 (English)In: SAE Technical Paper, no. 2009- 01-2045. May, 2009, 2009Conference paper, Published paper (Refereed)
National Category
Fluid Mechanics and Acoustics Vehicle Engineering
Identifiers
urn:nbn:se:kth:diva-19432 (URN)
Note
QC 20100809Available from: 2010-08-09 Created: 2010-08-09 Last updated: 2010-08-09Bibliographically approved
6. The Passive Acoustic Effect of Turbo- Compressors
Open this publication in new window or tab >>The Passive Acoustic Effect of Turbo- Compressors
(English)Manuscript (preprint) (Other academic)
National Category
Fluid Mechanics and Acoustics Vehicle Engineering
Identifiers
urn:nbn:se:kth:diva-19433 (URN)
Note
QC 20100809Available from: 2010-08-09 Created: 2010-08-09 Last updated: 2010-08-09Bibliographically approved

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