Effects of Unsteady Wake on Heat Transfer of Endwall Surface in Linear Cascade

The present study aimed to investigate the effect of an unsteady wake on the heat transfer for the endwall surface of a linear of cascade turbine blade. A naphthalene sublimation method was implemented to obtain the detailed heat/mass transfer distributions on the endwall surface. Tests were conducted on a five-passage linear cascade in a low-speed wind tunnel. The effects of unsteady wakes were simulated in the facility by a wake generator consisting of circular rods that were traversed across the inlet flow. The test conditions were fixed at a Reynolds number of 70,000 based on the inlet velocity and chord length. The flow coefficients were varied from 1.3 to 4.2 and the range of Strouhal number was 0.1-0.3. The results showed that the heat transfer distributions differed between steady and unsteady cases. The overall heat transfer for the unsteady cases was higher, and the heat transfer was enhanced with increasing the Strouhal number due to the resulting thin boundary layer and high turbulence intensity. Therefore, a cooling system for the endwall of a rotor should focus on reducing the high temperatures on the endwall surface induced by the unsteady wakes.