Performance analysis of different influencing factors on film cooling and the internal relations with vortex structures

Film cooling is a cooling technique in which a protective layer is generated by the coolant along the wall to shield the wall surface against high temperature flow. When the fluids of the coolant and high-temperature gas are of different qualities, it is often accompanied by the mass and energy transfer. During the film cooling process, the lower-temperature gas is transported to the surface through the tangential gap on the wall which requires thermal protection. And then the film is formed along the direction of the high-temperature flow, causing the solid wall isolated from the high temperature gas, thereby it can prevent the wall surface from being touched and damaged by hot stream. Since the film cooling sets high standards for hole shape, the structure of injection, the length of the coolant supply tube, the angle of incidence, the blowing ratio, the thickness of the boundary layer, ribs and the Reynolds number, etc., the analysis and optimization of these factors have been particular significance on improving cooling efficiency. This paper introduces the dominant factors which influence film cooling effectiveness, besides, analyzes the methods to achieve the best cooling results. The impact of the vortex structures on enhancing film cooling performance is explored. Moreover, a new train of thought is proposed to improve the cooling efficiency under the joint action of the vortex generator and the synthetic jet.