Methodology for experimental validation of a CFD model for predicting noise generation in centrifugal compressors

Abstract

Centrifugal compressors working in the surge side of the map generate a broadband noise in the range of 1 to 3 kHz, named as whoosh noise. This noise is perceived at strongly downsized engines operating at particular conditions (full load, tip-in and tip-out maneuvers). A 3-dimensional CFD model of a centrifugal compressor is built to analyze fluid phenomena related to whoosh noise. A detached eddy simulation is performed with the compressor operating at the peak pressure point of 160 krpm. A steady flow rig mounted on an anechoic chamber is used to obtain experimental measurements as a means of validation for the numerical model. In-duct pressure signals are obtained in addition to standard averaged global variables. The numerical simulation provides global variables showing excellent agreement with experimental measurements. Pressure spectra comparison is performed to assess noise prediction capability of numerical model. The influence of the type and position of the virtual pressure probes is evaluated. Pressure decomposition is required by the simulations to obtain meaningful spectra. Different techniques for obtaining pressure components are analyzed. At the simulated conditions, a broadband noise in 1-3 kHz frequency band is detected in the experimental measurements. This whoosh noise is also captured by the numerical model.

Numerical and experimental analysis of automotive turbocharger compressor aeroacoustics at different operating conditions

“…A full description of the experimental apparatus used to obtain the acoustical measurements was presented by Broatch et al [17].…”

“…1. Broatch et al [17] proved that NRBCs are not mandatory to predict the compressor acoustic signature provided that a pressure decomposition algorithm is used (further information is provided in Section 3.3). 3 operating conditions at 1.4, 1.8 and 2.5 times surge mass flow at a constant compressor speed close to 160 krpm were simulated.…”

“…The methodology developed by Broatch et al [17] is used in order to obtain the compressor acoustic signature for the considered operating conditions. Pressure spectral densities (PSD) are estimated by means of Welch's overlapped segmented average [28].…”

Acoustic characterization of automotive turbocompressors

“…This wave decomposition method has been used to validate three-dimensional (3D) computational fluid dynamics (CFD) models of the compressor fluid domain 27 and also to characterize the acoustic properties of compressors in order to implement onedimensional (1D) models of engines for predicting the gas dynamic response of the intake system. 28 However, the restrictions of intensity-based methods must be carefully considered, especially the influence of higher order modes and the aliasing frequency limit introduced by the spatial sampling imposed by the sensor spacing.…”

“…It should be noted that if characterization through in-duct techniques of this particular whoosh noise is intended, special attention should be placed on the outlet pipe, as this phenomenon is often found exclusively downstream of the turbocharger. 27 …”