Gas ingress prediction method for high rotational mach number rim seals

Abstract

The rim seal is a key component in an aero-engine turbine used to prevent gas ingress, and its performance has a significant impact on turbine efficiency and turbine-disc lifespan. Based on high - speed compressible fluid theory, this paper derives the radial momentum equation for fluid under isentropic, inviscid, compressible conditions. It proves theoretically that increasing the cooling air's circumferential and radial velocities helps resist gas ingress. Furthermore, a high - speed compressible rim seal estimation model was developed, converting the complex gas ingress problem into a cooling air supply pressure issue. Validated by high rotational Mach number rim seal experiments, when the total pressure margin coefficient exceeds zero, the sealing efficiency remains above 0.99. Thus, the model can accurately determine whether gas ingress occurs in the rim seal structure. Moreover, further research was conducted on the critical parameters of the estimation model, specifically the supply total pressure coefficient and the total pressure loss coefficient. It was found that a higher mainstream Mach number requires a higher cooling air supply pressure coefficient. An empirical relationship was developed based on experimental data, linking the variation of the cooling air supply total pressure coefficient to the mainstream Mach number. The maximum deviation between this correlation and the experimentally measured coefficient is less than 8.9%. Moreover, the cooling air total pressure loss coefficient increases with higher mainstream and rotational Mach numbers but decreases with a higher cooling air Mach number.