Effects of Impellers and Diffusers' Geometries on Performance and Rotating Stall of Centrifugal Compressor's Last Stage

Vaneless diffuser rotating stall in centrifugal compressor limits its operation range. Some correlations could be found for stall prediction in open literature, but they can't cover the case of last stage configuration, especially for very low blade-outlet-width to impeller-radius ratio impellers typically used in high pressure applications. Stall and performance prediction model based on wavelet neural network (WNN) was established using experimental data in literature. Resulted model was further used to analyze geometries' effects on stability and performance at design point. Results show that:for impellers with variable dimensionless outlet widths, diffusers of different scales exhibit distinct responses. Pinch shapes of diffusers have negligible influences on critical angle and performance. Analysis may guide diffuser design of last stage of centrifugal compressor.