High-speed Schlieren Investigations Of Characterisitics For Flow Field And Temperature Field In Film-cooling

As an important cooling mean, film-cooling has been widely used in high temperature parts at modern gas turbine combustors and turbine blades, The increase of film-cooling efficiency plays an important role in maintaining the high temperature parts performance and improving the machine service life. It is great help to improve film-cooling efficiency that investigating internal structure and functional mechanism for film-cooling flow field. In this paper, flat film-cooling test bed was established relying on the existing wind tunnel system in Zhejiang Sci-tech University, and combining with improved schlieren system and image acquisition system, the visual research was realized for flat film-cooling flow field. Under blowing ratios of 0.5, 1.0, 1.5, 2.0 and jet degrees of 30°, 45°, 60°, respectively, following aspects were studied: jet penetration of the mainstream, area covered by jet in expansion region, structure of vortex formed by interaction between jet and mainstream. Combined with numerical simulation method, the variations of vortices, temperature, and density in flow field were analyzed. Then the results were compared with the experimental results, The following main conclusions can be drawn:1. The penetrations of Jet to mainstream are different under various operating conditions. When jet degree is the same, the penetration is reinforced with the increase of blowing ratio. When blowing ratio is the same, the penetration is reinforced with the increase of jet degree. Both of them have monotonous change trend.2. The varying patterns of area covered by jet in expansion region are distinctive in different conditions. When the jet degree is 30°, with the blowing ratios increasing, the jet flow covered area increases as well, but compared with blowing ratio is 1.5, the jet flow lateral coverage no longer changes under blowing ratio of 2.0; When the jet degree is 60°, the jet flow covered area in 2.0 blowing ratio is smaller than that in 1.5 blowing ratio.3. Under the same blowing ratio, the scales of shear vortex and wake vortex increase with the increase of jet degrees significantly. Similarly, under the same jet degree, the scales of shear vortex and wake vortex increase with the increase of jet blowing ratios. But the jet degree has greater influence for shear vortex and wake vortex.