狭小空间内气膜孔流量系数的数值模拟
Numerical studies about the discharge coefficient of film cooling hole at narrow space
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摘要: 针对多层层板冷却、双层壁冷却等冷却技术,利用数值模拟分析了这些冷却结构形成的狭小冷却通道中,气膜孔附近的流动特性,重点研究了气膜孔流量系数Cd随吹风比M(0.5～2.0)、气膜孔雷诺数Re(5000～10000)以及冷却通道高度H和气膜孔直径D之比H/D(0.33～1.0)等参数的变化规律.数值计算中湍流模型为Realizable k-ε模型,近壁处采用非平衡壁面函数,利用SIMPLE算法和二阶迎风格式进行离散求解.计算结果表明:气膜孔流量系数随吹风比的增大而增大,在吹风比M小于1时,影响尤为明显.研究中同时发现在相同吹风比的条件下,Cd随着气膜孔雷诺数的增大而减小,但变化的幅度不大;在相同的气膜孔雷诺数下,Cd随着H/D的减小而降低,特别是当H/D小于0.75时,随着流体在进入气膜孔前逐步受到限制,Cd随着H/D的减小而快速降低.Abstract: Numerical simulations about the discharge coefficient Cd of film cooling at narrow space were carried out in this paper,and the characteristics of the flow around film hole in small cooling channel were also investigated.Blowing rate M(0.5～2.0),film cooling hole Reynolds number Re(5000～10000) and the ration of film cooling height to the film cooling diameter H/D(0.33～1.0) were changed to study the average discharge coefficient of a row of film holes.A finite volume method together with SIMPLE algorithm,second order upwind discrete format,was used to solve the three dimensional incompressible Navier-Stokes equations.The Realizable k-ε turbulence model was applied and non-equilibrium wall function was used for near wall treatment.The results show that the discharge coefficient Cd increases with the blowing rate M,especially when the M＜1;under the same blowing rate conditions,the discharge coefficient decreases with the Re rising faintly.In the same Re cases,the Cd becomes smaller when the H/D decreases.And the numerical results indicate that the decrease of Cd is very notable especially when H/D＜0.75.
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Key words:
- film cooling /
- discharge coefficient /
- narrow space /
- numerical simulation
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