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为了分析瞬态热冲击过程中气膜冷却传热规律,采用实验研究和CFD仿真分析方法,研究了瞬态热冲击工况下的平板缝槽气膜冷却传热特性。实验中,主流燃气以约60℃/s~100℃/s的增温速率来模拟瞬态热冲击工况,CFD仿真中,采用DES方法模拟瞬态混合层剪切涡结构对气膜冷却传热影响。结果表明:(1)实验结果显示,当吹风比处于临界值以下时,瞬态热冲击过程中,气膜绝热有效温比逐渐下降直至稳态值,对流换热系数存在同样的规律。(2)DES模拟结果显示,混合层摆动位置及剪切涡发展到壁面的位置随着吹风比的增大而向下游移动,使得壁面传热特性主要由剪切涡流决定逐渐转变为由冷却气流决定。(3)DES结果显示由于混合层剪切涡的不稳定性使得气膜绝热有效温比存在较大幅度的波动;相比RANS方法,DES方法预测的平均绝热有效温比与实验结果吻合更好。
In order to analyze the rule of film cooling heat transfer during transient thermal shock, the experimental study and CFD simulation analysis method were used to study the film cooling heat transfer characteristics of flat slab under transient thermal shock conditions. In the experiment, the mainstream gas is used to simulate transient thermal shock at a rate of about 60 ℃ / s ~ 100 ℃ / s. In the CFD simulation, the DES method is used to simulate the transient cooling effect Thermal effects. The results show that: (1) The experimental results show that when the blowing ratio is below the critical value, the effective thermal temperature ratio of the gas film decreases gradually until the steady-state value and the convective heat transfer coefficient during transient thermal shock. (2) DES simulation results show that the position of the mixing layer and the position of the shear vortex developing to the wall move downstream as the blow-up ratio increases, so that the heat transfer characteristics of the wall mainly change from shear vortex to cooling air flow Decided. (3) The DES results show that the effective thermal temperature ratio of gas-liquid membrane fluctuates greatly due to the instability of shear vortex in the mixed layer. Compared with the RANS method, the predicted average effective thermal-to-temperature ratio of DES method is in good agreement with the experimental results .