Circumferentially Smeared Computed Effects of Rim Seal Clearance on Wheelspace Thermal Distributions

An advanced finite volume computer code, recently bench-marked against rotor—stator cavity measurements (Ko and Rhode, 1992), was used to obtain an enhanced partial understanding of hot gas ingress heating of a generic turbine wheelspace cavity. This problem is extremely complicated, with a three-dimensional, probably circumferentially periodic ingress/egress flow through the rim seal due to mainstream pressure asymmetries resulting from the presence of blades, etc. The present study does not assume that the complete problem can be modeled as steady and two-dimensional axisymmetric. Rather, the objective of this study is to obtain a partial understanding of the complete problem from investigating the circumferentially smeared, steady, two-dimensional axisymmetric sub-problem. It was found that, contrary to the case of the nominal rim seal axial clearance, for a clearance of one-fourth of the nominal value, the temperature of the “hot spot” on the rotor is sharply reduced with increasing purge-coolant flow because the rim seal gap recirculation zone does not form. Also, it was found that smaller rim seal axial clearances give less rotational drag as well as less heat transport from the mainstream into the wheelspace.