The Aerodynamic Interaction of Seal Leakage and Mainstream Flows in a Compressor Cascade With Non-Axisymmetric Endwall

Abstract

Abstract In response to the escalating efficiency demands of the forthcoming generation of aircraft engines, the pursuit of higher bypass ratios and pressure ratios has led to an ongoing reduction in the size of the core engine. However, this scale-down of the core engine size is met with inherent challenges, as certain critical geometric characteristics, such as seal and tip clearances, cannot be proportionally reduced. This results in an increased proportion of leakage losses within the overall compressor losses. Additionally, the reduction in blade height and an increase in load lead to a significant rise in end-wall losses. Consequently, the control of flow near the end-wall region has become a major focus in the development of axial flow compressors. As a passive approach of flow control, nonaxisymmetric end-wall contouring has exhibited its efficacy in reducing losses within axial compressors and turbines. It operates by changing the pressure distribution near the end-wall to influence corner separation, consequently reducing end-wall losses. Typically, non-axisymmetric contouring is designed solely under the consideration of the compressor blade. In the actual axial compressor geometric, the presence of seal clearance leads to leakage flow interacting with the mainstream. The distinctive flow pattern produced by the seal leakage flow at the end-wall may diminish the efficiency gains that nonaxisymmetric end-wall contouring could otherwise achieve. Therefore, the objective of this study is to investigate the interaction mechanisms between seal leakage flow and the mainstream flow in a profiled end-wall compressor cascade with seal cavity. The non-axisymmetric end-wall contour employed in this study is derived through numerical optimization at a Mach number of 0.6 for a compressor cascade without seal cavity. Numerical results have been validated against experimental data, demonstrating the effectiveness of this end-wall contour in reducing end-wall losses for the cascade under both design and off-design conditions. The comparative analysis of the flow characteristics between the datum and end-wall contoured cascades with and without seal cavity is conducted. Particular emphasis is placed on investigating the alterations in flow structures induced by seal leakage flow on the end-wall contoured blades and the reciprocal influence of the end-wall contouring on the seal leakage flow. This research will provide valuable insights for the future design of shrouded compressors employing non-axisymmetric end-wall contouring.