Experimental study of sister hole film cooling performance in a rotating flat plate model

Film cooling performance of a sister hole was investigated in a flat plate model by applying Thermochromic Liquid Crystal (TLC) technique under the stationary and rotating conditions. The flat plate model is installed in the test section. The sister hole include one main hole and two additional side holes with the smaller diameter in the spanwise direction. The diameter of the main hole is 4 mm and the injection angle is 30°. The density ratio of coolant to mainstream is 1.05. The Reynolds number (Re_D) based on the velocity of mainstream and the diameter of the main hole are 2300, 3400 and 4500. Four rotational speeds of 200, 400, 600 and 800 rpm are conducted on both pressure side (trailing wall) and suction side (leading wall) with the blowing ratio varying from 0.14 to 3.5. The effects of blowing ratio, Reynolds number (Re_D) and rotation number are mainly analyzed according to film coverage and film cooling effectiveness. The results show that the film performance firstly increases then decreases with the rising of blowing ratio, the optimal blowing ratio is about M=0.5. The film cooling performance is improved with higher Reynolds number (Re_D). Under the rotation condition, the film trajectory has an obvious centrifugal deflection which can be enhanced by higher rotation number on the pressure side, and the film deflection moves a little centripetally on the suction side. The film cooling effectiveness on the suction side increases with the rising of rotation number and it is higher than that on the pressure side.