Heat-transfer coefficients of a turbine blade-tip and near-tip regions

The detailed distribution of heat-transfer coefficients on A gas turbine blade tip was measured using a hue-detection-based, transient liquid crystals technique. The heat-transfer coefficients on the shroud and near-tip regions of the pressure and suction sides of a blade were also measured. Tests were performed on a five-bladed linear cascade with a blowdown facility. The Reynolds number based on the cascade exit velocity and axial chord length of a blade was 1.1 x 10(6), and the overall pressure ratio was 1.2. The heat-transfer measurements were made at the three different tip gap clearances of 1.0, 1.5, and 2.5% of blade span. Results showed that, in general, the heat-transfer coefficients on the tip surface were higher than these on the shroud and on the near-tip region of the blade pressure and suction sides. Results also showed that as the tip gap clearance increased the heat-transfer coefficients increased on the tip surface, but the shroud and the blade suction side increased and then decreased. However, the heat-transfer coefficients on the blade pressure side remained almost unchanged as the tip gap clearance increased.