Unsteady Loss Assessment of a Transonic Compressor Stage Midspan Section

Abstract In transonic turbomachinery compressors, the aerodynamic loading is significantly increased, giving rise to complex flow phenomena, including shock boundary layer interactions. These interactions induce substantial unsteadiness and elevate loss levels that RANS models often fail to predict accurately due to inherent modeling limitations. Consequently, more advanced numerical methods, such as wall-resolved large eddy simulations, are required to capture the intricate flow structures and dominant loss mechanisms. This study investigates the unsteady flow loss production in a transonic compressor stage midspan section operating at engine representative Mach and Reynolds numbers using wall-resolved LES. An entropy generation based loss analysis, combined with a flow feature driven domain decomposition, is applied to identify the loss origin. Phase-locked results indicate that the shock and its interaction with the suction side boundary layer dominate loss generation, whilst the downstream convection of rotor wakes creates an unsteady loss behavior in the stator domain. Comparison with time-averaged results highlights clear differences in loss prediction. Major loss is caused by turbulence generation and mean flow viscous dissipation. The findings underscore the critical role of high-fidelity simulations in accurately capturing the complex unsteady flow in transonic turbomachinery and being the data source for advanced post-processing routines.