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Sound sources of radial compressors – experimental and numerical studies
Lars Enghardt1, Jakob Hurst2, Till Raitor1 and Wolfgang Neise
1German Aerospace Center (DLR), Engine Acoustics2Berlin University of Technology
Outline
• Introduction• Experimental study (on the suction side)• Spectral characteristics of radial compressor noise• Acoustic mode analysis for source mechanism identification• Numerical study on the pressure side• Conclusions
Folie 3
Introduction
Aerodynamic noise of centrifugal compressors used forturbo-charging Diesel engines on board of ships or in power stations has become serious problem for manufacturers
Goals of the experimental study:
Knowledge of dominating aerodynamic sourcemechanisms
Reduction of blade tone noise of radial compressorsthrough design measures
Experimental study of radial compressor noise to assess thespectral characteristics and explore the aeroacousticgeneration mechanisms of the rotational noise
Numerical study of radial compressor noiseon the pressure side
DLR.de • Chart 4
Experimental study
DLR Radial Compressor Test Bed
Folie 6
Experimental set-up
Measurement stations
Impeller SRV2 and Vaned Diffuser
Impeller SRV2D = 156/224 mm, Z = 13/26
Outlet diffuser with profiled vanes ZD = 23
Spectral Sound Characteristics; SRV2; Vaneless Diffuser
Circumferentially averaged sound pressure spectra in immediate inlet duct
nred
80
100
120
140
160
180
0 10 20 30 40 50Frequenz [kHz]
Scha
lldru
ckpe
gel [
dB]
BPF2 BPF
3 BPF4 BPF
Azimuthally Averaged Sound Pressure Spectra
SRV2, vaneless diffuserSRV2, vaned diffuser
nred = 36,000/min, immediate inlet duct
Frequency [kHz]
Soun
d pr
essu
re le
vel
[dB]
Tip clearance noise
Folie 10
nred = 50,000/min; immediate inlet duct
Azimuthal Mode Analysis of Spectral Components
80
100
120
140
160
180
0 10 20 30 40 50Frequenz [kHz]
Scha
lldru
ckpe
gel [
dB]
BPF
2 BPF
3 BPF
4 BPF
SRV2, vaneless diffuser SRV2, vaned diffuser
Soun
d pr
essu
re le
vel [
dB]
Frequency [kHz]
Folie 11
BPF = 10,900 Hz
SRV2, vaneless diffuserOperating point(design point):nred = 50,000/minMred = 2.56 kg/sΠtot = 5.44
Azimuthal Mode Spectra in Immediate Inlet DuctSRV2, Vaneless Diffuser
BPF = 10,900 Hz 2BPF = 21,800 Hz
VsZhm SR ⋅−⋅=&
:(1962) Sofrin&Tyler
Folie 12
130
140
150
160
170
30 35 40 45 50red. Drehzahl [1000/min]
Ges
amts
chal
ldru
ckpe
gel [
dB]
21 3
0,8 0,9 1,0 1,1 1,2abs. Umfangsmachzahl (Laufradeintritt)
unbeschaufelter Diffusorbeschaufelter DiffusorVaneless diffuser Vaned diffuser
Dominated by tip clearance noise
Dominated by blade tones
Dominated by blade tones
and buzz-saw
noise
Overall SPL in Inlet Duct, SRV2
Impeller tip Mach number at intake
nred [1000/min]
Ove
rall
soun
d pr
essu
re le
vel [
dB]
DLR.de • Chart 13
Numerical study
- 14 -
» Numerical Analysis1. Sound generation: 360° CFD-simulation of impeller, vanless diffuser and volute
2. Radial mode analysis (RMA) at volute outlet extraction of sound pressure field
3. Sound propagation: CAA-simulation of discharge pipe
• background flow: RANS-simulation
• inlet boundary condition: Imposed sound pressure field from RMA
2. Transition zone
3. CAA
1. CFD
© 2017 – Acoustic emission into discharge pipes - 30.03.2017
- 15 -
» 360° CFD-simulation
– TRACE: CFD-code developed for turbomachinery by DLR
– Fine grid resolution to avoid numerical dissipation/dispersion: 170 Mio. cells
– HPC-Cluster Aachen/Jülich (JARA): 600 cores - Intel Xeon X5675 (2TB RAM)
Test section
NozzleDamping section
VoluteDiffuser
Impeller
Inlet-nozzle
© 2017 – Acoustic emission into discharge pipes - 30.03.2017
- 16 -
» 360° CFD-simulation– BPF1 pressure fluctuations in Pa
– high noise level at volute outlet
– inhomogeneous field at volute outlet
© 2017 – Acoustic emission into discharge pipes - 30.03.2017
volute outlet
- 17 -
» Radial Mode Analysis (RMA)
» Extraction of acoustic mode field from URANS simulation via RMA at testsection.
© 2017 – Acoustic emission into discharge pipes - 30.03.2017
RMA
Up- and downstream propagating modes 1. BPF.
𝑝𝑝𝜔𝜔′
URANS
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Conclusions
Experimental study 4 radial compressor configurations tested on DLR-test bed:
1) SRV2 with vaneless/vaned diffuser2) SRV4 with vaneless/vaned diffuser (no results presented here)
Dominant noise generation mechanisms identified by way of spectral and mode analyses
Data base established for further evaluation
Numerical study 1 radial compressor configuration numerically modelled Dominant compressor tones (BPF1 & BPF2) on the pressure
side simulated and analysed by means of radial mode decomposition
Ongoing project to develop an accurate in-duct measurmentsystem with low sensor count for industrial needs
Folie 19
Acknowledgements
Financial support of the project by the
German Ministry of Economics and Labourvia the German Federation of Industrial Research Associations, AiF
and the Research Association for Combustion Engines, FVV
is gratefully acknowledged
Furthermore, the numerical study is financially supported by the