Film cooling characteristics and loss mechanism of combined construct with expansive main hole and contractive secondary holes
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摘要:
采用数值模拟的方法,在主流马赫数为0.6条件下,对比分析了三圆柱形组合孔、变截面圆柱形组合孔、新月形组合孔在不同吹风比(0.5~2.0)的气膜冷却特性与气动损失机理。提出了“主孔扩张、两侧副孔收缩”的新月形组合孔结构,中间的扩张主孔抑制了主流穿透,两侧的收缩副孔有利于冷气沿流向发展,主副孔压力梯度不同诱导了反肾形涡形成,从而改变了孔外的掺混结构,促进了冷气的横向发展,减少了掺混总压损失。结果表明:吹风比为1.5、2.0时,与三圆柱形组合孔相比,新月形组合孔的气膜冷却效率分别提高了17.8%、29.7%,气膜冷却带来的掺混总压损失减少了51%、43%。
Abstract:Film cooling characteristics and aerodynamic loss mechanism were numerically simulated under a mainstream Mach number of 0.6. Three-cylindrical combination holes, variable cross-section cylin-drical combination holes and crescent combination holes were compared at the blowing ratio varying from 0.5 to 2.0. In a crescent combination holes with expansive main hole and contractive secondary holes, main-stream penetration was prevented in the mid-expansion hole. As for the side-contraction holes, the anti-kidney vortex was promoted due to acceleration. The mixing structure was changed due to different pre-ssure gradients of holes. When the blowing ratio was 1.5 and 2.0, compared with three-cylindrical combi-nation holes, the film cooling effectiveness increased by 17.8% and 29.7%, respectively, and the mixing pressure loss due to film cooling declined by 51% and 43%, respectively, in crescent combination holes.
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Key words:
- film cooling /
- turbine blade /
- loss mechanism /
- shaped combination holes /
- flow in holes
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表 1 气膜孔出口参数
Table 1. Exit parameters of film cooling hole configuration
气膜孔形状 出口截面积/mm2 主孔 副孔 三圆柱形组合孔(3CY) 14.14 14.14 变截面圆柱形组合孔(NSIS) 25.13 6.28 新月形组合孔(CRESCENT) 35.45 10.04 表 2 边界条件设置
Table 2. Boundary conditions
边界条件 设计值 冷气进口温度Tc/K 300 主流进口马赫数 0.6 主流出口静压pout/Pa 101325 冷气与主流温比Tc/Tm 0.55 冷气与主流密度比ρc/ρm 1.8 吹风比M 0.5~2.0 -
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