Influence Of Blockage Of Film Cooling Hole Outlet On Film Cooling Characteristics Of Blade Surface

During the process of thermal barrier coatings on the blade surface,it will cause the coating to deposit at the exit of film cooling hole.There is no doubt that the blockage deposited at the outlet of film cooling hole affects the film cooling characteristics of the blade profile.In order to clarify the mechanism of film cooling hole blockage caused by TBC process on film cooling,film cooling effectiveness and heat transfer coefficient of blade suction surface,pressure surface and leading edge film cooling hole blockage ratio of 0.2-0.8 were studied by experiment and numerical simulation.The blowing ratio ranged from 1.0 to 2.0.The experimental results show that the film cooling effectiveness of the pressure surface and suction surface will gradually decrease at the pressure surface when the blockage ratio increases.B=0.8 will reduce film cooling effectiveness by 0.05-0.14;B=0.5 will reduce film cooling effectiveness by 0.03-0.12,while B=0.2 will have a weak impact on film cooling effectiveness.On the suction surface,B=0.8 decreases film cooling effectiveness by 0.1-0.26;B=0.5 decreases film cooling effectiveness by 0.05-0.14;B=0.2 has little effect on film cooling effectiveness.At the low blowing ratio,the larger the blockage ratio is and the smaller the heat transfer coefficient of the pressure surface is.At the high blowing ratio,the larger the blockage ratio is and the greater the heat transfer coefficient of the pressure surface is.The heat transfer coefficient of suction surface always decreases with the increase of blockage ratio.The numerical simulation results show that when the film cooling holes on the leading edge,pressure surface and suction surface are blocked,the larger the blockage ratio is,the more obvious the decrease of film cooling effectiveness is,and the smaller the coverage area of downstream film cooling is.Film cooling hole blockage has a lifting effect on the outflow of cooling air,and the larger the blocking ratio is,it will even cause the phenomenon of wall separation.When the blowing ratio is larger,the penetration of the cooling gas into the mainstream is enhanced,which leads to the enhancement of the intensity and scale of the kidney vortex caused by the jet.The enhanced kidney vortex pair worsens the flow field downstream of the hole,resulting in poor film cooling effect downstream of the film cooling hole.When the blowing ratio is small and medium,the blockage ratio increases and the heat transfer coefficient of the leading edge also increases.When the blockage ratio is large,the blockage ratio will increase and the heat transfer coefficient of the leading edge will decrease.