Effects of ingestion on the flow and heat transfer in a rotor-stator system

Ingestion (or ingress) of hot mainstream gas into the wheel-spaces between the rotor and stator discs in the high pressure stages of gas turbines is one of the most important internal cooling problems for engine designers. A rim seal at the periphery of the wheel-space and a radial outflow of sealing air are used to reduce or prevent this
damaging ingestion. The sealing air is also used for rotor disc cooling. In this paper, a simplified axisymmetric computational fluid dynamics (CFD) model of a gas turbine rotor-stator wheel-space is used to predict the effects of ingress on the flow and heat transfer. The steady flow computations are carried out using the CFD code ANSYS/CFX and the shear stress transport (SST) turbulence model. The rotational Reynolds number, inlet flow rates and thermal boundary settings are selected to represent the operating conditions of an ingress experimental rig, and comparisons are made between computations and measurements of heat transfer in the wheel-space. The computed heat transfer from the steady model (in terms of values of local Nusselt number on
the rotor) is in broad agreement with measurements obtained using thermochromic liquid crystal in a transient experiment. Alternative wall-surface thermal boundary conditions are investigated in order to study the sensitivity of computed Nusselt numbers to these modelling assumptions.