ANALYTICAL STUDY ON THE PERFORMANCE OF CENTRIFUGAL COMPRESSOR CONSIDERING RUNNING TIP CLEARANCE

In this study, a series of aero-thermo-mechanical analyses were carried out to predict the running tip clearance and the effects of impeller deformation on the performance using two different centrifugal compressors (blade type A and B). In operation, impeller deformation due to the combination of centrifugal force, aerodynamic pressure and thermal load results in non-uniform tip clearance profile. The predicted running tip clearance leads to further findings of its impact on compressor performance. The prediction employs one-way fluid-structure interaction (FSI) method using CFX 14.5 and ANSYS. The results show that the maximum displacement occurs at the leading edge tip of the impeller blade but maximum stress takes place at the blade root of the impeller for these particular designs. The analysis also confirms the centrifugal force has dominant effect on impeller deformation at its operating condition. The predicted running tip clearance shows non-uniform profile over the entire flow passage. In particular, a significant reduction of the tip clearance height has occurred at the leading edge and the trailing edge of the impeller. Due to the reduction of the tip clearance, the tip leakage flow has decreased by 19.4% and 16.2% in the blade type A and B, respectively. Also, the polytropic efficiency of the blade type A and B at operating condition has increased by 0.72% and 1.81%, respectively. These findings confirm that the prediction of running tip clearance and its impact on compressor performance is important area for further investigation.