Near-hub loss mechanisms in multistage compressors: Assessment and modeling of shrouded-stator leakage

Leakage flow through shrouded-stator cavities introduces additional aerodynamic losses and near-hub flow distortions, which may propagate through downstream blade rows and deteriorate compressor performance. To enable computationally efficient prediction of these leakage-induced effects, this study develops a reduced-order leakage prediction framework that avoids the explicit construction and meshing of internal cavity geometries. The proposed coupling framework accounts for the thermodynamic and aerodynamic characteristics of the leakage flow by incorporating corrections for the total-pressure loss and windage heating within the seal cavity. The resulting leakage state is then transferred to the mainstream computational domain through physically consistent hub-wall mapping, thereby enabling effective coupling with the three-dimensional mainstream flow solver. The model is first validated against representative seal configurations and a high-load compressor cascade, and is further applied to realistic single-stage and 3.5-stage compressor. The results demonstrate that the proposed model accurately reproduces the clearance-dependent leakage characteristics, near-hub total pressure deficit, and flow angle distortion, while maintaining good agreement with the overall compressor performance trends. For the investigated compressor configurations, the predicted overall performance parameters exhibit differences of less than 1% compared with those obtained using fully resolved three-dimensional simulations, while the computational mesh size is reduced by approximately 30%. Furthermore, the model effectively captures the generation of leakage-induced near-hub flow disturbances, their spatial diffusion, and their interstage propagation through successive blade rows. These results demonstrate that the proposed framework provides a physically consistent and computationally efficient approach for predicting leakage-induced losses in multistage compressors equipped with shrouded stator cavities.