| Aero gas turbine engine thermal efficiency and power output increase along with the increase of inlet gas temperature.The leading edge area of the blade is directly impacted by the high temperature gas,which is the most serious heat load region.Not only the leading-edge film cooling of the blade,but also the aerodynamic performance of the cascade is affected by this phenomenon.The design of the leading edge film cooling structure has effectively become a key and difficult question to researchers.At present,there are many related report about the leading edge of cylindrical blade while the study of the leading edge of elliptical blade is little.The leading edge of elliptical blade can improve aerodynamic performance of turbine cascade.Based on this,the film cooling efficiency and heat transfer characteristics of single row,two rows and three rows of cylindrical holes were studied by numerical simulation at the blowing ratios of 1.0 to 2.0 respectively.The results show that the spanwise averaged film cooling effectiveness will decrease with the increase of the blowing ratio and increase after the decrease in the direction of the mainstream.The spanwise averaged film cooling efficiency decreased by 76% with the blowing ratio increases from 1 to 2.The cooling efficiency decreased 19% when the film cooling effectiveness of center line downstream of hole exit decreases with the increase of blowing ratio.When the blowing ratio increases,compound angle injection produces the large spanwise coverage,resulting in the weak decrease of spanwsie averaged film cooling effectiveness.When the blowing ratio is low,the distance between the gas film hole and the stagnation line is far away,the better the air cooling is in the spanwise diffusion,the higher the film cooling efficiency is,and the film cooling efficiency increased by 75%.When the blowing distance is higher,the farther the distance between the holes and the stagnation line is,the spanwise diffusion of film cooling improved,the film cooling efficiency increased 96%.The film cooling efficiency increased from 45% higher to 60% with increasing the amount of the row,and the bigger the blowing ratio is,the more obvious the effect is.The spanwise average convection heat transfer enhancement coefficient decreases along the mainstream direction,the first half fell by 12%,and the second half fell by 3%.The trend of the enhancement coefficient of convection heat transfer in the downstream of the center of the hole is basically the same as that of the spread average convective heat transfer enhancement coefficient.In the same position downstream of the gas film hole,the increase of the average convection heat transfer enhancement coefficient decreases with the increase of the blowing ratio,with lower 4%.The farther the gas film hole distance lag line is,the higher the enhancement coefficient of convection heat transfer is,increased by 4.5%,when the phenomenon of high blowing ratio is more obvious,increased from 4.5% to 7.5%.The convective heat transfer enhancement coefficient is the highest at the double row hole,whichis 6.1% higher than the single row hole and the three row hole. |
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