Rotor Cavity Flow and Heat Transfer With Inlet Swirl and Radial Outflow of Cooling Air

To improve the reliability of turbine disc life prediction, experimental verification is required of analytical tools that calculate the flow field and heat transfer coefficients in turbine-stator cavities. As a first step, a full-scale model of the forward cavity of a typical aircraft gas turbine was employed using a high-molecular-weight gas (Refrigerant-12) at ambient pressure and temperature conditions to match the dimensionless parameters at engine conditions. The cavity temperature and selected cavity velocity profiles were measured using electrical heat addition with liquid crystal surface temperature measurement to obtain local disc heat transfer coefficients. A part of the cooling gas flow was added through a rotating inner seal with the remainder added at high angular swirl in the direction of rotation at a larger radius. Rotational Reynolds numbers were varied up to 9×10⁶ with the radial Reynolds number variation up to 9000. A first-order comparison is given of the velocity distribution and disc heat transfer coefficients calculated by a CFD code and the measured values. The disc heat transfer coefficients can be dominated by the inlet swirl flow or by the rotor speed, depending on whether the coolant flow is greater or smaller than that generated by the rotor alone acting as a free disc.