An experimental and numerical study on the blade tip conjugate heat transfer performance

In the gas turbine, the blade tip is under extreme heat load and thereby it is necessary to adopt cooling method for the tip region. In this work, a blade tip conjugate heat transfer model was conducted in a linear cascade. The tip overall cooling effectiveness (& phi;) and adiabatic cooling effectiveness (& eta;) were measured by the pressure sensitive paint (PSP) and the Infrared thermography (IR), respectively. Impacts of coolant blowing ratios (M = 1.0 - 2.5), tip gap size (& tau; = 1.98%, 3.97%C, chord length), and film holes locations on the tip & phi; distributions were investigated. Then, the numerical simulations were performed to obtain the tip solid temperature distributions, and to reveal the conjugate heat transfer characteristics. Within the scope of this work, both the tip & phi; distributions and the tip solid temperature distributions indicate that the convection in film holes is a major factor of the tip conjugate heat transfer process. The tip area-averaged & phi; for the CL_H case are increased evidently by 13.1%-38.9% with the increased coolant M, whereas the increase of & eta; is not obvious. The tip gap size has less effect on the tip & phi; distributions than the coolant M, especially at a low M. The higher & phi; and the lower tip solid temperature region are detected near the film holes for any film hole location. The area-averaged & phi; values of the cases with film holes along the chamber line are 10.6% and 3.0% higher than those of the cases with film holes along the pressure-side or suction-side rim, respectively. This work revealed the major factor in the tip conjugate heat transfer process and may serve as a guide for tip cooling design.