Numerical Evaluation of Losses in Shrouded and Cantilevered Stators of a Multi-Stage Axial Compressor

The loss coefficient based only on the stagnation pressure has traditionally been used in the analysis of axial compressors for the comparison between shrouded and cantilevered stator configurations. In recent years, engineers have been able to perform more detailed Computational Fluid Dynamics simulations, allowing them to resolve the flow field in the leakage paths. The two stator hub designs are, however, affected by the rotating surfaces in a different way: in cantilevered stators, the relative rotation between the stator and the hub imparts energy to the hub flow, whereas in shrouded stators, the rotating inner leakage surface imparts energy to the seal cavity leakage flow. The aim of this work is to analyze the performance of a multi-stage axial compressor featuring a change of stator hub configuration, by employing both the conventional loss coefficient based on the stagnation pressure and the loss coefficient based on the entropy change. It is shown, that in the evaluation of the losses of a multi-stage axial machine, it is essential to consider the different 3D distributions of stagnation temperature resulting from the two stator hub configurations, which are transferred to the downstream rows.