Effect of Leakage Flows on the Performance of a Family of Inline Centrifugal Compressors

Abstract

The impact of the hub and shroud leakage flows on the compressor efficiency has been investigated for four compressor stages with flow coefficients of 0.017, 0.0265, 0.063, and 0.118 belonging to a family of centrifugal compressor stages, designed for process compressor applications. A very good agreement was observed between the measured and predicted performance when the detailed geometrical features were included in the calculations. The computational fluid dynamics (CFD) calculations indicated that addition of leakage cavities and leakage flows resulted in about 3% drop in stage polytropic efficiency for the highest flow coefficient stage. The detrimental effect of leakages increased to about 8% for the lowest flow coefficient stage investigated here. The increase in the compressor work input due to the disc windage and the leakage recirculation was estimated from the CFD calculations and compared with values obtained using 1D methods, showing a very good agreement between the two. The impact of parasitic losses on compressor efficiency has been investigated and the contribution of various loss sources to the stage efficiency is discussed.