Experimental investigations of the effects of the injection angle and blowing ratio on the leading-edge film cooling of a rotating twisted turbine blade.

Highlights • The leading edge film cooling of a rotating twist turbine blade is studied with TLC. • The injection angle and M can affect the leading edge film cooling effectiveness. • A new photo testing technology in rotating state is introduced in this paper. Abstract Experimental investigations were performed to study the effects of the injection angle of cylindrical holes and the blowing ratio on the leading-edge-region film cooling of a twisted turbine blade under rotating conditions. The experiments were carried out at a test facility with a 1-stage turbine using the thermochromic liquid crystal (TLC) technique. All experiments were performed at a rotating speed of 574 rpm with an average blowing ratio ranging from 0.5 to 2.0. The Reynolds number was fixed at 6.3378 × 104 based on the mainstream velocity of the turbine outlet and the rotor blade chord length. CO 2 was used as the coolant to achieve a coolant-to-mainstream density ratio of 1.56. The film-hole injection angles tested were 30°, 45° and 60°. The results show that both the injection angle and the blowing ratio have significant impacts on film cooling effectiveness. For α = 30° and α = 45°, the radial average film cooling effectiveness increases as the blowing ratio increases in all regions. For α = 60°, this effectiveness first increases and then decreases as the blowing ratio increases, with the case of M = 1.5 yielding the best average cooling performance. At each blowing ratio, the α = 30° case always yields the highest streamwise average film cooling effectiveness in the region of −4.3 < X/D < 2. For 2.75 < X/D < 3.75, the effectiveness first increases and then decreases as the injection angle increases. For α = 30° and α = 45°, the area average film cooling effectiveness monotonously increases as the blowing ratio increases. For α = 60°, this effectiveness first increases and then decreases as the blowing ratio increases from 0.5 to 2.0, with the best blowing ratio M = 1.5. Under the same blowing ratio, the α = 30° case always yields the highest area average film cooling effectiveness in the leading edge region. [ABSTRACT FROM AUTHOR]