This paper presents a review of research on turbine rim sealing with emphasis
placed on the underlying flow physics and modelling capability. Rim seal flows play a
crucial role in controlling engine disc temperatures but represent a loss from the main
engine power cycle and are associated with spoiling losses in the turbine. Elementary
models that rely on empirical validation and are currently used in design do not
account for some of the known flow mechanisms, and prediction of sealing
performance with computational fluid dynamics (CFD) has proved challenging. CFD
and experimental studies have indicated important unsteady flow effects that explain
some of the differences identified in comparing predicted and measure sealing
effectiveness. This review reveals some consistency of investigations across a range
of configurations, with inertial waves in the rotating flow apparently interacting with
other flow mechanisms which include vane, blade and seal flow interactions, disc
pumping and cavity flows, shear layer and other instabilities, and turbulent mixing.
A systematic study of sealing performance for a chute style turbine rim seal using URANS methods is reported. This extends previous studies from a configuration without external flow in the main annulus to cases with a circumferentially uniform axial flow and vane generated swirling annulus flow (but without rotor blades). The study includes variation of the mean seal-to-rotor velocity ratio, main annulus-to-rotor velocity ratio, and seal clearance. The effects on the unsteady flow structures and the degree of main annulus flow ingestion into the rim seal cavity are examined. Sealing effectiveness is quantified by modeling a passive scalar, and the timescales for the convergence of this solution are considered. It has been found that intrinsic flow unsteadiness occurs in most cases, with the presence of vanes and external flow modifying, the associated flow structures and frequencies. Some sensitivities to the annulus flow conditions are identified. The circumferential pressure asymmetry generated by the vanes has a clear influence on the flow structure but does not lead to higher ingestion rates than the other conditions studied.