Optimization of the inlet air line of an automotive turbocharger

Abstract

This paper presents different aspects of air inlet behaviour near the inducer of a radial compressor and shows how the geometry can contribute to its stability and performance. Unfortunately, the space reserved for installation of an automotive turbocharger in a vehicle is constantly being reduced, so it is necessary to study the effects that elbows and abrupt changes in flow directions originate on the compressor performance. The work presented in this paper studies the effect that different 90° elbows have on the compressor with respect to its ideal, straight, no-elbow configuration, in order to obtain the best possible elbow configuration. The methodology followed has been to, initially, study different geometries in computational fluid dynamics code in order to obtain the best possible configuration. Then, several 90° elbows were constructed and characterized on a continuous flow test bench in order to validate the computational fluid dynamics results and to obtain optimum results. The elbows were then installed on a radial compressor and tested on a hot, continuous turbocharger test bench, where the compressor was characterized and maps were obtained with each different elbow. The results were compared with respect to the ideal, no-elbow configuration, which was taken as the base performance. After analysing the results obtained, it is possible to observe that in most of the cases, the elbows have a negative effect on the compression ratio, which tends to be reduced, especially at high rotor velocities and high air mass flow. On the other hand, the effect on the surge limit seems to be positive, as the surge line shifts to lower air mass flows, although the maximum mass flow allowed is reduced. It seems as if the compressor map shifts to the left with a reduction in compression ratio. From theoretical and experimental studies, it has been concluded that flow uniformity index and pressure loss are the most important factors affecting the performance of the compressor.