辐射换热对平板气膜冷却性能影响

Effects of Radiation Heat Transfer on Film Cooling Performance of Flat Plate

关键词:  流热耦合  辐射换热  隔热屏  气膜冷却  离散坐标法

Key words:  Conjugate heat transfer  Radiation heat transfer  Heat shield  Film cooling  Discrete ordinates method

摘要:

为了分析辐射换热对平板气膜冷却性能的影响，分别对不考虑辐射换热(耦合计算)与考虑辐射换热两种条件下的平板隔热屏进行了三维流热耦合数值模拟研究，并与绝热壁(不考虑隔热屏固壁导热)的计算结果进行了对比。辐射换热采用离散坐标法。得到了3种不同主/次流总温比([Rt])条件下气膜冷却效果、流场、单位面积冷流体热负荷以及流量系数的对比结果与变化规律。结果表明:气膜冷却效果沿流向逐渐降低，且随总温比的增加而降低；在展向上气膜冷却效果呈现中间高两边低的分布规律，最大与最小相对值在绝热壁条件下达到最大，为94.5%，辐射换热次之，为13.5%，不考虑辐射换热时最小，为9.8%。与不考虑辐射换热结果相比，辐射换热对气膜冷却效果的影响在流动方向逐渐变大，气膜孔附近展向温度梯度增大，冷流体热负荷增加了92.8%，二者计算的流量系数相差不大，为1.1%，与绝热壁计算结果相比，流量系数减小了13.1%。随着总温比增加流量系数减小，最大值与最小值相差不大，为1.1%。

Abstract:

In order to investigate the effects of heat conduction，convection and radiation heat transfer on film cooling performance of flat plate under three different total temperature ratio([Rt])of the primary fluid to the secondary fluid conditions，discrete ordinates radiation model and three-dimensional numerical simulation of fluid-heat coupling were conducted under two conditions of coupling calculation(without considering the effect of radiation heat transfer)and radiation heat transfer calculation(considering the effect of radiation heat transfer)，and contrastive studies were carried out with the results of the adiabatic condition. Change laws of film cooling effect，flow field，coolant heat load per unit area and discharge coefficient have been obtained. The results show that the film cooling effect decreases in the streamwise direction and decreases with the increase of Rt. The value of film cooling effect in the film covered area is larger than the value of both sides at the same spanwise location. The maximum value(94.5%)of film cooling effect gradient in the spanwise direction happens under the adiabatic condition and the result of radiation heat transfer and conjugate calculation is 13.5% and 9.8% respectively. Compared with the results of conjugate condition，the influence of radiation heat transfer on the film cooling effect become larger in the streamwise direction，the spanwise temperature gradient increases near the film cooling hole and the coolant heat load increases by 92.8%，but the difference of discharge coefficient is slightly，of 1.1%，between the two cases. The discharge coefficient considering the effect of radiation heat transfer is lower 13.1% than the value of adiabatic condition and has a small decline，of 1.1%，with the increase of total temperature ratio.