Numerical And Experimental Analyses of Flow Distortion Reduction by Blade Cascades

Abstract Modern propulsion systems use serpentine engine inlet ducts to reduce thermal and radar signatures, while also enhancing aerodynamic and engine performance. However, these ducts can introduce adverse flow effects, such as flow separation and vortex formation, potentially degrading engine efficiency. This study combines computational and experimental methods to develop and validate a vane assembly designed to reduce the strength of a twin vortex flow at the aerodynamic interface plane (AIP) of such ducts. A numerical analysis was conducted using a Cartesian grid-based flow solver with adjoint sensitivity analysis to optimize vane geometries, aiming to minimize cross-flow velocities at the AIP through a steepest descent algorithm. A low-speed benchtop experiment was employed to validate additively manufactured vane geometries. Stereoscopic particle image velocimetry (PIV) was employed to measure three-component velocity fields downstream of the vanes, providing insights into in-plane velocity profiles, axial velocity contours, and swirl angles. Both numerical and experimental results indicated a reduction in swirl angles from 15 degrees to below 3 degrees. Swirl descriptors supported the effectiveness of the distortion remover, showing a 62% decrease in swirl intensity (SI). An analysis of the normal components of Reynolds stress tensor further demonstrated the effectiveness of the device in mitigating flow distortions. This integrated study offers practical insights into the passive control of flow distortions in propulsion systems, presenting potential applications for enhancing aerospace performance.