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Acoustic Characterization of Turbochargers and Pipe Terminations
KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL. (CCGEx)
2012 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

In search for quieter engines there is a need for a better understanding of the acoustic properties of engine intake and exhaust system components. Besides mufflers which have the purpose of reducing pressure pulses originating from the internal combustion (IC) engine, there are many components in a modern car exhaust and intake system, e.g., air-filters, coolers, catalytic converters, particulate filters - all having an effect on the pressure pulses or sound field in the system. In this work the focus is on the turbocharged IC-engine where both, sound scattering (reflection and transmission) and sound generation from automotive turbochargers are studied. In addition, sound reflection from an open ended pipe, such as the tailpipe of an IC-engine exhaust is investigated.

            Accurate and efficient methods to fully characterize turbochargers by measuring the acoustic two-port have been developed.  Compared to earlier work, a number of modifications are suggested for improving the quality of the results. A study on three different automotive turbochargers is also presented, including data for sound scattering for both the compressor and turbine. The results for the transmission of sound, which is of interest for the ability of a turbocharger to reduce noise coming from the engine, is plotted for all tested cases against a dimensionless frequency scale (Helmholtz-number). This makes it possible to generalize the result in order to draw conclusions about the behavior for any turbocharger. 

            The sound generation was also studied and three different methods to estimate the sound power are suggested. The methods were used to investigate sound generation at different operating points and identify source mechanisms for a turbocharger compressor.

            An accurate method for measuring the reflection of plane acoustic waves from a pipe termination in a duct with hot gas flow has been developed and tested. Representing the acoustical conditions at an exhaust tail-pipe, the data obtained is important for effective modeling of exhaust systems. The experimental results of the reflection coefficient were compared with Munt`s theory on flow duct openings. The measurements were carried out for air jet velocities up to Mach 0.4 and for flow temperatures up to 100°C in order to study temperature effects on the reflection properties. It was concluded, that the experimental results agree well with the Munt theory.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2012. , vi, 24 p.
Trita-AVE, ISSN 1651-7660 ; 2012:07
Keyword [en]
acoustical two-port, turbocharger, transmission loss, sound generation, compressor, turbine, IC-engine, inlet system, exhaust system, flow duct, duct termination, reflection coefficient
National Category
Vehicle Engineering
URN: urn:nbn:se:kth:diva-92648OAI: diva2:514184
2012-04-13, Seminar room Mechanics, KTH, Brinellvägen 32, Stockholm, 10:00 (English)
TrenOp, Transport Research Environment with Novel Perspectives
Available from: 2012-04-10 Created: 2012-04-05 Last updated: 2013-04-11Bibliographically approved
List of papers
1. Sound transmission in automotive turbochargers
Open this publication in new window or tab >>Sound transmission in automotive turbochargers
2011 (English)In: Noise and Vibration Conference and Exhibition (SAE NVH 2011)Grand Rapids, Michigan, USA, May 2011, 2011Conference paper (Refereed)
National Category
Vehicle Engineering
urn:nbn:se:kth:diva-93041 (URN)
Available from: 2012-04-10 Created: 2012-04-10 Last updated: 2012-04-10Bibliographically approved
2. Investigations of automotive turbo-charger acoustics
Open this publication in new window or tab >>Investigations of automotive turbo-charger acoustics
2011 (English)In: SAE International Journal of Engines, Vol. 4, no 2, 2531-2542 p.Article in journal (Refereed) Published
Abstract [en]

In this paper an overview of recent experimental studies performed at KTH on the sound transmission and sound generation in turbochargers is presented. The compressor and turbine of the turbochargers are treated as acoustic active 2-ports and characterized using the unique experimental test facility established at KTH. The 2-port model is limited to the plane wave range so for higher frequencies the propagating acoustic power is estimated using an average based on pressure cross-spectra. A number of automotive turbochargers have been studied for a variety of operating conditions systematically selected from the compressor and turbine charts. The paper discusses the experimental procedures including special techniques implemented to improve the quality of the data. Results from a number of experiments on various modern automotive turbochargers including a unit with variable turbine geometry (VTG) are presented.

National Category
Engineering and Technology Vehicle Engineering
urn:nbn:se:kth:diva-81615 (URN)10.4271/2011-24-0221 (DOI)2-s2.0-84859373671 (ScopusID)
KTH-CCGEx. QC 20120410Available from: 2012-02-10 Created: 2012-02-10 Last updated: 2012-04-10Bibliographically approved
3. Investigation of sound reflection from a hot and subsonic flow duct termination
Open this publication in new window or tab >>Investigation of sound reflection from a hot and subsonic flow duct termination
2012 (English)In: Journal of Sound and Vibration, ISSN 0022-460X, E-ISSN 1095-8568Article in journal (Other academic) Submitted
plane wave reflection, duct termination, hot jet, exhaust system
National Category
Vehicle Engineering
urn:nbn:se:kth:diva-93042 (URN)
SQ 2012Available from: 2012-04-10 Created: 2012-04-10 Last updated: 2012-04-10Bibliographically approved

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