Modelling and Numerical Simulation of the Noise Generated by Automotive Turbocharger Compressor

An effective technology to reduce emission and fuel-consumption is the use of turbochargers. A turbocharger increases the air pressure at the inlet manifold of the engine by using the waste energy from the exhaust gas to drive a turbine wheel that is linked to the compressor through a shaft. Besides the use in combustion engines, fuel cell systems for vehicle applications also need compressed air to achieve high power densities. Thereby, in fuel cell systems the noise emission of turbochargers is no longer masked by the combustion engine. In operation, the main noise sources are generated by the flow in the compressor and the different noise phenomena need to be understood in order to efficiently reduce the emitted noise and increase comfort. A huge potential in order to achieve this goal is a simulation based investigation to study in detail the flow mechanism, the aeroacoustic sources and its sound propagation. However, the actual physical source mechanism as rotational and pulsation noise as well as hiss / whoosh noise is currently not fully understood. Therefore, the main goal of this research is the physical correct modelling and numerical simulation of the aeroacoustics in compressors and the computation of the sound propagation in a whole turbocharger. In detail, the following steps will be performed: (1) instationary, compressible flow computations using LES (Large Eddy Simulation) / DES (Detached Eddy Simulation) turbulence models; (2) analysis of aeroacoustic sources computed; (3) computation of the sound propagation within and outside the turbocharger based on coupled mechanical-acoustic simulations.