【作者】 刘建红；

【导师】 郭婷婷；

【作者基本信息】 东北电力大学 ， 热能工程， 2007， 硕士

【摘要】 气膜冷却是燃气轮机叶片广泛采用的有效冷却保护技术,准确预估气膜冷却效果对燃气轮机叶片等的设计起着至关重要的作用。本文采用数值计算方法,模拟单圆孔气膜冷却流场的流动和传热特性,分析讨论了Standard k -ε模型、RNG k -ε模型、及Realizable k -ε模型对横向紊动射流的适用性;又通过对比分析渐缩喷孔、圆形气膜孔和扇形气膜孔三种孔形的温度场,总结了不同入射孔形状对温度场的影响,及不同孔形的温度场随吹风比的变化趋势;最后采用大涡模型(LES)模拟圆形气膜孔和扇形孔γ=30o时不同截面上的涡量等值线以及分布特征随时间的变化过程。结果表明:在模拟存在分离和回流流动的横向紊动射流时,RNG k -ε模型的预测值比Standard k -ε模型的预测值更为准确;圆形气膜孔的吹风比越小,射流中心线越靠近壁面,底面的冷却效率越好;在同一条件下,扇形气膜孔近壁面的流场比圆形气膜孔尤其是渐缩喷孔稳定,其底面的冷却效率最高,且冷却效率并不随吹风比的变化而单调变化,而是在吹风比M=0.7时存在最佳值,对于单排孔布局,γ=30o底面的冷却效率最高,且对于多排孔布局,γ=60o最高;对称面的正反旋涡和垂直截面的马蹄形涡的两翼交替周期性地脱落成新的涡,同一截面扇形气膜孔旋涡生成和脱落的时间比圆形气膜孔的短,冷气射流与主气流掺混剧烈,带走的能量较多,所以壁面的冷却效率高。更多还原

【Abstract】 Film cooling is mostly used for protecting the blade erosion for hot gas in gas turbine, it is importent for devising the blade while predict cooling effect precisely. Numerical simulation was performed to investigate the flow and heat transfer characteristics of a round hole of film-cooling, using Standard k -ε、RNG k -εand Realizable k -εturbulence models, and the results were compared and analyzed to decade which one is best to compute the jet-to-crossflow; Through comparing and analyzing the temperature fields of converage hole、round hole and cone holes, characteristics of temperature fields of different holes with different blowing ratios were studayed; And Large Eddy Simulation (LES) was performed to investigate the development process of vortices on different sections of a round hole and a cone-shaped holes withγto be 30o.The results suggested that when simulating the cross flow which exist separate flow and back flow, the RNG k -εturbulence model obtained improved prediction than the Standard k -εmodel’. For the round holes, the smaller blowing ratio was, the more jet trajectories close to the wall was, and the greater cooling effectiveness was. At the same blowing ratios, the flow fields of cone hole was more stability than the round especrally the converage hole’s, the cooling effectiveness of the cone hole was superior to the two holes’s. The cone hole had an optimal jet-to-crossflow blowing ratio, about 0.7 to make the cooling effectiveness highest, for arrangement of single hole, a cone hole withγto be 30o was the optimal jet hole, for arrangement of rows holes, a cone hole withγto be 60o geometries was the optimal. The positive and negative vortices in the centreplane and the two wings of the horseshoe vortices in the vertical profiles were shed off new vortices alternately and periodicly, the time of sheding off of cone hole’s was less than the round hole’s at the someprofile, the acting of jet and crossflow was more acuity in the near wall, so carried off more energy, then enhanced t he film cooling effectiveness.更多还原