Endwall heat transfer and film cooling measurements in a turbine cascade with injection upstream of leading edge

Detailed heat transfer measurements were conducted on the endwall surface of a large-scale low speed turbine cascade with single and double row injection on the endwall upstream of leading edge. Local film cooling effectiveness and heat transfer coefficient with coolant injection were determined at blowing ratio 1, 2 and 3. In conjuction with the previous measurement flow field, the behaviours of endwall film cooling and heat transfer were studied. The results show that endwall film cooling effectiveness is influenced to a great extent by the secondary flow and the coverage of the coolant on the endwall is mainly determined by blowing ratio. An uncovered triangle shaped are a with low effectiveness close to pressure side could be observed at low blowing ratio injection. The averaged effectiveness increases significantly when injecting at medium and high blowing ratio, and quite uniform coverage of coolant on the endwall could be achieved. The averaged effectiveness could be doubled in case of double row injection. It was also observed that coolant injection made the overall averaged heat transfer rate increase remarkably with blowing ratio and then made the thermal loads on the endwall decrease effectively. Large increments of heat transfer rate could be happened at cascade entrance and exit and in the area near suction surface.