Aero-thermal optimization of the rim seal cavity to enhance rotor platform thermal protection

Abstract

Abstract The flow field in the rotor-stator rim cavity is controlled by both the instantaneous distortion caused by rotor and stator airfoils. Naturally one would then assume that the design of optimal rim seal geometries would require full unsteady turbine stage simulations, that would then require an experimental assessment. This manuscript presents a reduced-order approach, neglecting the obvious unsteady interaction effects, to optimize the cavity geometry with a two-dimensional axisymmetric approach, making it possible to explore a wide range of geometries followed by an experimental assessment in a linear cascade. Two parameterization strategies are presented, coupled with a genetic optimizer to maximize thermal protection to the rotor rear platform while minimizing the cooling massflow required. This reduced-order optimization scheme was then assessed at different levels of sophistication to assess the effect of rotation, the vanes, and the rotor geometry with a series of increasing levels of fidelity to the real turbine conditions. Finally, this paper demonstrated the sensitivity of the optimal geometries to variations in the axial gap and purge coolant total pressure.