Aeroacoustics characterization methodology applicable to turbocharger compressor

Abstract

Turbochargers have become an important part of modern high efficient engines, and soon will be a standard component. Almost all automotive and industrial diesel engines and most of the high performance SI engines are equipped with turbocharger. Even though past few decades have seen continuous performance improvement, there is still lack of wide range research on acoustical behavior of turbochargers. A turbocharger consists of compressor which is driven by an exhaust turbine. Turbocharger produces high frequency aerodynamic sound due to the high speed rotating blade. The main aerodynamic noise generating mechanisms in turbo-compressors is tonal noise at blade passing frequencies, buzz-saw noise and blade tip clearance noise. The focus will be on tonal noise which occurs due to pressure fluctuation that is related to the rotating speed. The tonal noise is periodic in time where it consists of the blade passing frequency (BPF) and its harmonics. Higher rotating speed will result in a more prominent blade passing noise and its harmonics. The aim of this paper is to offer a methodology on characterizing the tonal noise of turbocharger based on investigation of high speed turbo machinery, which also has similar acoustical behavior. This study will include results from commercial computational fluid dynamics (CFD) code and experimental with the sound pressure level distribution