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Modified multi-load method for nonlinear source characterisation
KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL.
KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL.ORCID iD: 0000-0002-8474-8563
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.

Place, publisher, year, edition, pages
2007. Vol. 299, no 4-5, 1094-1113 p.
Keyword [en]
high-intensity sound, one-port sources, fluid machines, duct
National Category
Fluid Mechanics and Acoustics
URN: urn:nbn:se:kth:diva-16201DOI: 10.1016/j.jsv.2006.08.013ISI: 000242769100024ScopusID: 2-s2.0-33750624594OAI: diva2:334243

QC 20100525

Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2014-11-17Bibliographically approved
In thesis
1. Studies of flow duct acoustics with applications to turbocharged engines
Open this publication in new window or tab >>Studies of flow duct acoustics with applications to turbocharged engines
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.
Trita-AVE, ISSN 1651-7660 ; 2009:29
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
urn:nbn:se:kth:diva-10590 (URN)
Public defence
2009-06-05, Sal D3, Lindstedtsvägen 5, KTH, Stockholm, 13:30 (English)
QC 20100809Available from: 2009-06-01 Created: 2009-05-29 Last updated: 2010-08-09Bibliographically approved

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