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Research Papers: Gas Turbines: Turbomachinery

A Robust Industrial Procedure for Measuring Modal Sound Fields in the Development of Radial Compressor Stages

[+] Author and Article Information
Peter Limacher

ABB Turbo Systems AG,
Bruggerstrasse 71a,
Baden 5400, Aargau, Switzerland
e-mail: peter.limacher@ch.abb.com

Carsten Spinder

ABB Turbo Systems AG,
Bruggerstrasse 71 a,
Baden 5400, Aargau, Switzerland
e-mail: carsten.spinder@ch.abb.com

Marius C. Banica

ABB Turbo Systems AG,
Bruggerstrasse 71 a,
Baden 5400, Aargau, Switzerland
e-mail: marius.banica@ch.abb.com

Heinz-Jürgen Feld

ABB Turbo Systems AG,
Bruggerstrasse 71 a,
Baden 5400, Aargau, Switzerland
e-mail: heinz-juergen.feld@ch.abb.com

1Corresponding author.

Contributed by the Turbomachinery Committee of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received September 27, 2016; final manuscript received November 2, 2016; published online February 1, 2017. Editor: David Wisler.

J. Eng. Gas Turbines Power 139(6), 062604 (Feb 01, 2017) (10 pages) Paper No: GTP-16-1471; doi: 10.1115/1.4035287 History: Received September 27, 2016; Revised November 02, 2016

The turbocharger is a significant noise source in large diesel engines, such as those used in container vessels. Its main noise source is the radial compressor, where improvements in silencers and turbocharger insulation have led to a considerable reduction of compressor inlet noise emission over the past few years. As a result, compressor outlet noise is now becoming increasingly significant for large engines. Recently, an in-house compressor testbed was upgraded by adding an acoustic modal measurement system (MSMS) that allows detailed investigation of modal sound fields inside the piping. This forms part of an updated compressor acoustic qualification procedure. This paper is an in-depth treatise of the characteristics of this modal measurement system. The calculation approach for the modal decomposition and a simplified alternative that assumes axial propagation, as well as relevant considerations, such as spatial resolution, averaging, and the use of multiple reference sensors, are addressed. Various measurement parameters, such as repeatability, measurement time, required temperature stability, pressure scaling, flow noise and their impact on measurement uncertainty were investigated. A successful validation of the modal sound measurement system with a well-known modal sound field at the compressor inlet is also presented. Finally, the characteristics of the modal sound fields of the compressor outlet of a typical modern turbocharger are discussed. Modal decompositions at the first two blade passing frequencies (BPFs) are presented for selected operating points (OPs). The response of total sound power levels (PWLs) to compressor speed along the operating line (OL) is examined by means of both the present and the simplified algorithm. A sensitivity analysis shows the impact of volume flow and rotational speed on the modal sound distribution.

Copyright © 2017 by ASME
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References

Banica, M. C. , Limacher, P. , Feld, H.-J. , and Spinder, C. , 2016, “ Numerical Investigation of the Sources and the Modal Content of the Acoustic Field in a Radial Compressor Outflow,” ASME Paper No. GTP-16-1483.
Habing, R. A. , and Feld, H.-J. , 2013, “ On the Modal Sound Field at the Outlet of a Turbocharger Centrifugal Compressor,” 10th European Turbomachinery Fluid Dynamics and Thermodynamics Conference, ETC10, Lapppeenranta, Finland, Apr. 15–19, Paper No. A007.
Tyler, J. , and Sofrin, T. , 1962, “ Axial Flow Compressor Noise Studies,” SAE Technical Paper No. 620532.
Michalke, A. , 1989, “ On the Propagation of Sound Generated in a Pipe of Circular Cross-Section With Uniform Mean Flow,” J. Sound Vib., 134(2), pp. 203–234. [CrossRef]
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Mumcu, A. , Keller, C. , Hurfar, C. M. , and Seume, J. R. , 2016, “ An Acoustic Excitation System for the Generation of Turbomachinery Specific Sound Fields—Part 1: Design and Methodology,” ASME Paper No. GT2016-56020.
Hurfar, C. M. , Keller, C. , Mumcu, A. , and Seume, J. R. , 2016, “ An Acoustic Excitation System for the Generation of Turbomachinery Specific Sound Fields—Part 2: Experimental Verification,” ASME Paper No. GT2016-56969.
ISO, 2003, “ Acoustics—Determination of Sound Power Radiated Into a Duct by Fans and Other Air-Moving Devices—In-Duct Method,” Standard No. ISO 5136:2003-4 (E).
Lighthill, M. J. , 1952, “ On Sound Generated Aerodynamically. I. General Theory,” Proc. R. Soc. A, 211(1107), pp. 564–587. [CrossRef]
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Figures

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Fig. 1

Cross-sectional static pressure distribution at a random instance in time for modes (a) (3,0) and (b) (3,1)

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Fig. 4

Sound pressure level of the outermost radial probe at one circumferential probe rack position

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Fig. 5

Mean coherence, averaged over all probe sensors and all reference sensors

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Fig. 3

Schematic representation of the compressor map that was used for the present investigation. Also shown are the OL, the OPs at which results are presented (dots) and the design point (dot with second highest volume flow).

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Fig. 8

Calculated SPL at second BPF

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Fig. 9

Comparison of sound pressure levels of wall mounted sensors and sensors on the rack

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Fig. 2

Modal sound measurement system

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Fig. 6

Measured sound power levels at second BPF in the measurement plane

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Fig. 7

Modal sound power levels at the second BPF. The bars with black dots represent 95% confidence intervals.

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Fig. 10

Schematic sketch of the compressor inlet geometry

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Fig. 11

PWL response to turbocharger speed for the first BPF at the compressor inlet

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Fig. 12

Modal PWL at first BPF in the compressor inlet, OP with highest total PWL

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Fig. 13

PWL response to turbocharger speed at the compressor outlet. The vertical line indicates the middle speed of sensitivity analysis.

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Fig. 14

Modal PWL at first BPF in the compressor outlet, OP at highest turbocharger speed

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Fig. 15

Modal PWL at second BPF in the compressor outlet, OP at highest turbocharger speed

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Fig. 16

Modal sound power levels at first blade passing frequency. Response of mode distribution to variations in compressor speed and volume flow.

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Fig. 17

Modal sound power levels at second blade passing frequency. Response of mode distribution to variations in compressor speed and volume flow.

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