ABSTRACT
The energy conservation and emission reduction requirements of internal combustion engines push turbochargers towards high efficiency and high compression ratio. Centrifugal compressors with vaned diffuser have significant efficiency advantages at high pressure ratio. Due to the compactness demand of internal combustion engine, the compressor inlet often has a prominent elbow structure. In this paper, the influence of inlet elbow on the performance of centrifugal compressor with vaned diffuser is studied. Firstly, the influence of elbow on compressor efficiency, pressure ratio and operating range is analyzed. The flow loss distribution differences of several inlet pipe geometries are compared and analyzed based on entropy generation method. The results show that the inlet elbow causes strong circumferential and radial flow distortion at the inlet of the impeller, which can lead to a significant deterioration of the performance of the centrifugal compressor. Furthermore, the influence of the elbow is highly dependent on its location relative to the volute, because the elbow-induce flow distortion is strongly coupled with the volute-induce flow distortion in the impeller and diffuser. Specifically, compared with the straight pipe, the efficiency reduces notably by 1.3% at inlet bending direction of 270 degree clockwise with the volute tongue, but increases by 0.6% at 180 degrees. Moreover, the operational range is also notably influenced by the location of the elbow. This study provides guidance for the layout and optimization of compressor inlet pipe geometry.
