Aerodynamic investigation of a three-stage transonic axial compressor

In high-loaded multistage axial compressors, shock waves are introduced into rotor designs to increase pressure ratio per stage, and shock structures should be organized differently to exploit inflow with varied Mach numbers. In this paper, aerodynamic performances under shock effects are investigated numerically in a three-stage axial compressor, and the compressor is tested to verify the numerical results. Compared with previous studies in transonic rotors, this paper focuses on the transonic flow in a multistage condition, and the analysis at design speed is achieved by combining through-flow and Computational Fluid Dynamics (CFD) calculations. Grid sensitivities and turbulence models in numerical methods are discussed, allowing accurate numerical predictions of the compressor with less than 1% errors in mass flow rate and efficiency. Flow problems are then identified based on comprehensive analysis of the meridional and three-dimensional flow fields. It is shown that most through-flow and CFD results agree well with each other and the test data, while a few problems still exist in flow details concerning about shock/boundary-layer interactions and off-design conditions. Two types of shock-induced separations on suction surfaces of transonic rotors are discovered at design speed, which leads to excessive loss correlated to different sources based on the strength comparison between passage shock and subsonic diffusion. Another problem is located in the stator of the third stage (S3), where the hub endwall flow presents evident failure tendency at near-choke and near-stall points of design speed. The analysis above lays solid fundamental for optimization design in future studies.