Computed Effects of Rim Seal Clearance and Cavity Width on Thermal Distributions

Abstract

Axisymmetric solutions of the Reynolds averaged Navier-Stokes equations were obtained for the complete momentum/thermal interaction at the interface between the turbine hot mainstream and rim seal flow regions. Specifically, the 2-D, axisymmetric, fully elliptic form of the equations was solved in order to obtain detailed insight concerning the effect of the rim seal clearance and cavity width on the disk temperature, gap recirculation zone GRZ and rotational drag. The mainstream and purge flow rates, pressures and temperatures were selected to match those of a typical commercial engine. The details of seven generic geometries, consisting of different seal clearance gaps and different cavity widths, for each of several cooling flow rates are analyzed. Of particular interest is the result that halving the engine nominal axial clearance of the generic rim seal is not sufficient for preventing the appearance of the GRZ. However, reducing this clearance to 25% of the nominal value does prevent its formation, and in that case the coolant flow continues outward along the disk surface through the rim seal region. In addition, the first-order characteristics of: (a) the heat transport in the rim seal region and (b) the disk temperature rise due to thermal transport via the rim seal (gap) recirculation zone and via disk frictional heating were illuminated. Further, it is concluded that smaller seal clearances are desirable for reducing rotational drag as well as purge flow rates.