粗糙度对不同尺度的双层壁结构冲击换热特性影响

Effects of Roughness on Impacting Heat Transfer in Different Scale Double-Wall

关键词:  双层壁  尺度  粗糙度  数值模拟  冲击

Key words:  Double-wall  Scale  Roughness  Numerical simulation  Impingement

摘要:

为了探讨精密铸造涡轮叶片内部表面粗糙度对冲击换热特性的影响，数值模拟研究了粗糙度分别为0μm，10μm，20μm，30μm，冲击雷诺数为1×104～5×104，大、小两种尺度的双层壁结构靶面换热系数。采用瞬态液晶技术测量了大尺度模型粗糙度为0μm时靶面换热系数。结果表明，大尺度光滑靶面换热系数数值模拟结果和实验数据吻合较好。两种尺度的光滑壁面换热系数经无量纲处理后基本相同。粗糙度增加使小尺度靶面换热系数增大，冲击雷诺数越大，粗糙度对换热系数影响越明显，冲击雷诺数从1×104增加到5×104，相比于光滑靶面，粗糙度为30μm时平均换热系数提高了6%～48%。粗糙度对大尺度靶面换热系数影响非常小。

Abstract:

To investigate the effects of internal roughness in precision casting turbine blade on impacting heat transfer characteristics，heat transfer coefficient of different scale double-wall were simulated at internal roughness of 0μm，10μm，20μm and 30μm and at Reynolds number range from 1×104 to 5×104. Heat transfer coefficients on target plate of large-scale at roughness of 0μm were measured by transient liquid crystal technology. The results show that the numerical results of heat transfer coefficients on target plate of large scale agree well with the experimental data. Heat transfer coefficients of smooth plate for two different scales are substantially the same after dimensionless processing. Heat transfer coefficients on target plate for small scale increase as the surface roughness increases. This influence of roughness becomes more obvious as Reynolds number increases，as Reynolds number varies from 1×104 to 5×104，the area-averaged heat transfer coefficients on target plate with the roughness of 30μm for small scale are higher 6%～48% than the result of the smooth target plate. The influence of roughness on heat transfer coefficients for the large scale is weak.