Effects of Stator Platform Geometry Features on Blade Row Performance

Real geometry features such as shroud cavities, inter-platform and vane-pack gaps can affect the hub endwall flow through compressor blade rows. Additionally, misalignment of the platform endwalls due to manufacturing tolerances can be important. This paper details an experimental and computational investigation of these effects. To ensure that the measurements were representative a novel experimental technique was developed to generate end-wall skew in the linear cascade. Without the presence of the endwall boundary layer skew the cascade flow did not capture the flow features typically observed in multi-stage compressor operation.

The skew generation method involves injecting flow along the endwall in such a manner as to control both the displacement thickness and tangential momentum thickness of the resulting boundary layer. The study reveals that real geometry features can have a significant impact on the flowfield within a blade passage. For stator shrouds, increasing leakage flow rates increases the stagnation pressure loss coefficient however, increasing the level of whirl pickup of the leakage flow can offset the natural secondary flow and thus reduce the loss. All of the steps and gaps that were found to be present in real compressors were found to increase the losses relative to a smooth endwall. It is also shown that CFD simulations are capable in capturing the trends observed in the experiments.