| Gas turbines are important power machinery equipment for the development of technology and military industry in China.Improving the inlet temperature is a significant method to solve the problem of efficiency of gas turbines.Due to the limitation of the production of high temperature resistant materials,modern gas turbine engines can only withstand the high temperature from 1800 K to 2000 K.As a result,the effective cooling technology has become an urgent requirement for industrial promotion.Film cooling technology is a common cooling technology in the blade cooling system of gas turbine.Film cooling technology can help to improve the inlet temperature of gas turbine,which contribute to efficiency enhancement and adequate thermal protection effect for industrial equipment.In recent years,the changeable design of upstream configuration has attracted attention of many researchers all over the world.However,the effect of upstream bulge configuration on film cooling effectiveness has not been fully discussed by researchers.For the purpose of solving this research gap,the structure of upstream bulge is investigated by numerical simulation and the influence of different bulge structure and blowing ratios on film cooling effectiveness is analyzed in this study.In this paper,a simplified channel was utilized to investigate the properties of film cooling.By the method of numerical simulation of the cooling effectiveness of the downstream film hole,the influence of the upstream configuration on the film cooling effectiveness was analyzed.The software ANSYS FLUENT 16.2 was used to study the function of different bulge configurations with heights(0.1d,0.3d,0.5d),width(0.1d,0.3d,0.5d)and bulge position(1d,3d,5d)The distance from the bulge front to the center of the film hole)with the blowing ratio of 0.5 and 1.0.The results show that the film cooling effectiveness will be more uniformed with the present of upstream bulge structure.Moreover,the lateral film cooling effectiveness will be improved as well.Compared with other cases,the optimum effectiveness of film cooling is obtained both in lateral and streamwise with the bulge height of 0.3d.The optimal lateral film cooling effectiveness is gained with the bulge configuration width of 0.1d when the blowing ratio is relatively low.With the increase of the bulge configuration width,the lateral film cooling effectiveness decreased.When the blowing ratio is relatively high,the bulge configuration with width of 0.3d has the best film cooling effectiveness in the direction of streamwise.With the increase of the distance from the right end of the bulge to the center of the film,the film cooling effectiveness along the centerline of wall increased first and then decreased.The optimal film cooling effect is obtained when the distance from the right end of the bulge to the center of the film hole is 3d.In order to investigate the influence of bulge configuration on film cooling effectiveness furtherly,the function of different bulge configuration shapes(rectangular,arc and polyline type)on film cooling effectiveness were also discussed in this paper.The film cooling effectiveness on the downstream wall and the middle section were analyzed.Meanwhile,the film cooling effectiveness on the centerline of the film hole and the cross section were quantitatively analyzed.In addition,the model of unconnected rectangular bulge configuration was deeply analyzed and the downstream temperature distribution and cooling effectiveness of upstream unconnected bulge configuration with 1d,1.6d and 45 degrees were also studied respectively by taking the effects of different blowing ratios(M=0.5/1.0)into consideration.For the case with relatively low blowing ratio,the results show that the film cooling effectiveness of the downstream wall center line with polyline bulge configuration increases significantly in a certain range,and the film cooling effectiveness increases significantly along the both sides of the centerline.The cooling film is spread more evenly on the wall and it is obtained a better lateral cooling effectiveness of the wall with the connected configuration bulge.For the case with unconnected configuration bulge,the cooling effectiveness of the downstream central area of the film hole decreased and the lateral film cooling effectiveness of the wall are significantly enhanced. |
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