CFD Modeling Effects on Unsteady Multistage Simulation for a Transonic Axial Compressor

Unsteady three-dimensional multistage calculations are performed for a highly loaded, high-speed axial compressor to investigate the impact of real geometry modeling and different numerical approaches on the accuracy of the performance prediction. First, two features of the real geometries are separately compared with the calculation which consists of a pure flow path model except that rotor tip clearances are considered. One treats leakage generated by part gaps between variable stator vanes and the annulus lines. Another incorporates seal cavities to model leakage underneath the shrouded stators. Then, the influence of different numerical approach with different turbulence models is also investigated. Discussion on the impact of the CFD modeling on the performance prediction focuses on the prediction accuracies of stage operating points and spanwise mixing. It is suggested that a realistic simulation of turbulent-type flow unsteadiness in a multistage machine is important for an accurate prediction of spanwise mixing phenomena.