Local heat and mass transfer in a rotor-stator system with hub inflow: Thermal boundary layer and superposition effect

Improving the cooling performance of a gas turbine rotor-stator system can have a significant impact on the efficiency of a gas turbine engine. In this study, we investigated the local heat and mass transfer (HMT) of a rotor -stator system with hub inflow considering the thermal boundary layer and superposition effect. A rotor-stator system test facility capable of analyzing HMT characteristics was constructed. Measurements of local HMT co-efficients were carried out using the naphthalene sublimation method. First, the development of local HMT was investigated using discontinuous boundary condition experiments. Quantitative evaluation of the high HMT in the windward area revealed the thermal entrance regions. Then, to assess individual and combined effects, the local HMT characteristics were analyzed under three conditions: hub inflow-only, rotating-only, and a combi-nation of hub inflow and rotating flows. Hub inflow dominated in regions below local rotational Reynolds number (Rer) of 1.25 x 105, and the enhancement region appeared above Rer of 2.0 x 105. Our study described for the first time the boundaries of HMT in a rotor-stator system based on the dominant influence of superposed flow. We expect our results to aid the development of cooling designs for rotor-stator systems in gas turbine engines.