Flow and heat transfer in a rotating channel with impingement cooling and film extraction

Abstract

Impingement cooling is applied on the turbine blade leading edge which suffers the highest heat transfer and needs priority protection. The current work focuses on the rotational effects in an impingement cooling channel with film extraction, in which heat transfer is obtained with experiment whereas the flow field is predicted by numerical simulation. The dimensionless spacing of jet-to-jet (s/Dj) and jet-to-target surface (l/Dj) are both 3. The jet Reynolds number and the channel orientation (the angle between jet direction and rotating orientation) are 5,000 and 135°, respectively. The jet rotation number changes from 0 to 0.24, and the maximum jet buoyancy number reaches 0.57. The results show that the heat transfer on the suction side is better than that on the pressure side where the recirculation region generates. The heat transfer deteriorates from high to low radius due to the non-uniform mass flow rate distribution. Once the channel rotates, the non-uniformity of mass flow rate increases because the vortex occurs in the supply channel, resulting in the heat transfer increase by 140% in the low radius region on the pressure side. On the pressure side in the impingement channel, the rotation-induced secondary flow breaks the recirculation region, promoting the heat transfer. On the suction side, however, the secondary flow and rotation-driven jet deflection decrease the heat transfer. Besides, the jet buoyancy number is inappropriate to describe the combined influences of jet rotation number and wall-to-fluid temperature ratio at high jet buoyancy number in current experimental conditions.