Experimental research on film cooling characteristics of multi-film-hole-rows

The present study experimentally explores the effect of the film-hole-row layout and hole angle on the film cooling characteristics of the multi-rows of micro-film-hole by the transient infrared technique. Reynolds number based on the diameter of the micro film hole and Knudsen number are 7000 and 7 × 10⁻⁵, respectively, and the dimensionless parameters of the experiment are the same as those of the real turbine blade. Two blowing ratios of 0.5 and 1.0 are investigated. Five rows of the film hole in leading edge have a pronouncedly positive effect on the film cooling effectiveness in the upstream region, and obtain an excellent coolant coverage at the blowing ratio of 1.0. The Nusselt number of the whole test surface is significantly decreased by five rows of the film hole in leading edge with the hole angle of 45° at the blowing ratio of 1.0. Increasing the hole angle from 45° to 90° decreases the span-wise averaged film cooling effectiveness of the test surface, and this phenomenon is obvious at the blowing ratio of 1.0, the maximum is about 29 %. There is a high heat transfer region at the beginning of the test surface of the five rows of the film hole in leading edge with the hole angle of 90° structure due to the mainstream-blockage-effect.