Effects Of Reynolds Number On The Performance Of Centrifugal Compressor

Micro turbine engine has attracted more and more attentions in the field ofaerospace and energy power in recent years. The performance condition of thecentrifugal compressor with high rotation speed, which is one of the cores of microturbine engine, plays a significant role. When the compressor is working at the lowReynolds number condition with high altitude, due to the low air density andtemperature, the viscous force enhances. So the flow situation in the passage is rapidlyworse and the performance decreases. Therefore, it is necessary to study the structure offlow field at different Reynolds numbers. It can provide a theoretical basis for thedesign of high-performance centrifugal compressor at different Reynolds numbers.A centrifugal compressor was investigated in this paper. Numerical simulationusing the CFX software was proceeded. Firstly, the flow situation of single passage wascalculated. Then characteristic lines in the conditions of different Reynolds numberswere obtained. Secondly, the result of calculation of whole passages was compared withthat of single passage. Detailed analysis of result with whole passages at differentcharacteristic points was performed. Finally, the flow situation of single passage withtransition model was calculated and analyzed.The results show that, with the drop of Reynolds number, the efficiency of thecentrifugal compressor decrease markedly. When the operating height is20kilometers,the efficiency of the compressor declines about9percent in the single passagecalculation,10percent in the whole passages calculation and8percent in the calculationof single passage with transition model respectively. The secondary flow loss andprofile loss increased significantly at low Reynolds number. The position of flowseparation moved ahead. There were reattachment, transition and inverse transition inthe flow passage. The flow situation was more severe near the working condition ofstall and choke. Owing to the effect of the volute, compared with the result ofcompressor in single passage, the stable operation range of compressor in wholepassages obviously reduces and the peak efficiency descends approximately6percent.The fall of efficiency of compressor in single passage with transition model is nonlinear.