EFFECT OF COOLANT JET HOLES ARRANGEMENT ON FILM COOLING PERFORMANCE

The film cooling effectiveness and local heat transfer coefficient for coolant jet holes, arrangement, orientation, and inclination angle have been investigated. The tests were carried out using a single test transient IR thermography technique. Evaluation of the cooling performance is obtained by estimated both film cooling effectiveness and heat flux ratios. Two arrangements of coolant jet holes were tested; one is inline holes and the other is staggered holes. Three blowing ratios of (BR= 0.5, 1.0, and 1.5) were used. In order to predict the flow behavior at the holes region, numerical solutions were introduced. It was found that the interaction and diffusion of the coolant air with hot stream present moderate film temperature beyond the downstream row; this flow is mixed with the coming counter vortex pair from downstream row improved the film cooling effectiveness. Experimentally, staggered arrangement gives better coolant performance than that of inline arrangement. The investigation also showed that using the upstream staggered oriented jet over conventional single jet enhanced the average cooling performance by 20.7%, 28.9%, and 37.8% for BR= 0.5, 1.0, and 1.5, respectively.