Acoustic characterization of automotive turbocompressors

Abstract

The performance of different experimental techniques proposed in the literature for acoustic characterization was assessed through the study of the noise generated by the compressor of an automotive turbocharger under different working conditions in an engine test cell. The most critical restrictions of in-duct intensimetry methods regarding frequency limitations are presented and experimentally demonstrated. The results provided by those methods were correlated against a reference intensity probe. A beamforming method based on three-sensor-phased arrays appears to be the most reliable approach in the plane wave range, presenting higher accuracy than the more common two-microphone method and simple pressure level measurements. Also, preliminary results from a novel radiated noise quantification technique based on acoustic particle velocity are presented and discussed. The results indicate that further research on this topic is required.

Acoustic signature of flow instabilities in radial compressors

“…In [38] it is mentioned that broadband noise occurs in the range 1 < RO < 2 for a similar size compressor as the one used in the present study. Whereas [9] relates this to "tip clearance" noise due to leakage between the shroud and the blade tips.…”

Effect of the inlet geometry on performance, surge margin and noise emission of an automotive turbocharger compressor

“…Mass flow rate and compressor inlet pressure were recorded at a frequency of 1 kHz instead, since they were used to detect surge appearance (see Section 2.2). Additionally, a directional intensity probe was installed facing the inlet mouth, surrounded by acoustic insulation mats in order to avoid reflections from the walls or other components[29]. This probe measures the sound intensity level (SIL) up to 5 kHz in order to characterize the compressor intake orifice noise.…”

Impact of simple surge-enhancing inlet geometries on the acoustic behavior of a turbocompressor

“…These geometries were installed in a turbocharger test rig situated inside an anechoic chamber [17], which provided an adequate acoustic environment, free of the wall reflections that are common in standard turbocharger test rigs and engine cells. While in these cases it is necessary to resort to induct techniques to characterize the acoustic emission of the turbocharger [8], the anechoic environment allows external acquisitions. Thus, orifice noise measurements were carried out along with radiated noise recordings with the objective of characterizing the far-field acoustic emission as well.…”

“…Since the shaft speed of the turbocharger group is much higher than that of the engine, high pitched sounds can be produced [8], upsetting the usual psychoacoustic 'masking' of higher frequency mechanical noise by the lower frequency combustion-generated noise [9] and thus creating in the customer the perception that a mechanical malfunction may be happening, or that the engine 'quality' is lower.…”