With the inlet temperature of gas turbine continuously increases, film cooling is commonly used to protect the blades. However, the kidney vortex generated by the mixing between mainstream and film injection is negative to the film attachment, which deteriorates the film cooling characteristics. To solve the problem, a kind of contracted double-jet hole is introduced to form an anti-kidney vortex to balance the adverse effect of the kidney vortex. By studying the flow mechanism of the contracted double jet hole in a flat plate model under different geometric parameters, the foundation for the application of contracted double jet hole on blades is established. Different injection angles including the inclination angle and compound angle were considered to improve the film cooling effectiveness and aerodynamic loss in a flat plate. The Reynolds Average Navier-Stokes (RANS) method of the SST - turbulence model is chosen to solve the above arrangement. The results show that a merging process happens before the anti-kidney vortex is formed and three vortices remain, causing an asymmetric distribution of film coolant. Changes of injection angle affect the flow field mainly through Vortex 3. As for different inclination angles at different blowing ratios, a best inclination angle at 30° when blowing ratio equals to 1.5. The laterally averaged cooling effectiveness reaches 0.36. After changing the compound angle, the cooling effectiveness can be improved. Film Cooling Uniformity Coefficient (CUC) is introduced to evaluate whether the distribution of coolant is symmetric. Other than the factors mentioned above, rate of entropy creation per unit volume is affected by the distance between the two legs of the anti-kidney vortex. Analysis of the entropy increase per unit in combination with a Q-criterion analysis reveals the interaction mechanism of coolant and mainstream. The region of entropy increase caused by viscous work per unit volume over 500 W/(m·K) reveals the entropy increase cause by mainstream and coolant is mainly because of the velocity difference between mainstream and coolant and the rate of the entropy increase caused by temperature per unit volume indicates that the mainstream will be enrolled into the anti-kidney vortex pair. The analysis of the entropy increase per unit also reveals the loss mechanism of Vortex 3 on anti-kidney vortex pair.

中文翻译：

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喷射角度对平板收缩双喷孔气膜冷却特性及损失机理的影响

随着燃气轮机进口温度不断升高，通常采用气膜冷却来保护叶片。然而，主流和薄膜喷射之间的混合产生的肾形涡流对薄膜附着不利，这恶化了薄膜冷却特性。针对这一问题，引入了一种收缩式双喷孔，形成反肾涡流，以平衡肾涡流的不利影响。通过研究不同几何参数下平板模型中收缩双喷孔的流动机理，为收缩双喷孔在叶片上的应用奠定了基础。考虑不同的喷射角度，包括倾斜角和复合角，以提高平板的气膜冷却效率和气动损失。选择SST-湍流模型的雷诺平均纳维-斯托克斯(RANS)方法来求解上述布置。结果表明，在反肾涡形成之前发生了合并过程，并留下了三个涡，导致了液膜冷却剂的不对称分布。喷射角度的变化主要通过Vortex 3影响流场。对于不同吹风比下的不同倾角，当吹风比为1.5时，最佳倾角为30°。横向平均冷却效率达到0.36。改变复合角后，可以提高冷却效果。引入薄膜冷却均匀系数（CUC）来评估冷却剂分布是否对称。除上述因素外，单位体积的熵产生率还受到反肾涡两腿之间距离的影响。对单位熵增的分析结合 Q 准则分析揭示了冷却剂和主流的相互作用机制。单位体积粘性功引起的熵增超过500 W/(m·K)的区域揭示了主流和冷却剂引起的熵增主要是由于主流和冷却剂之间的速度差以及由主流和冷却剂引起的熵增速率。单位体积温度表明主流将被纳入反肾涡流对。对单位熵增的分析也揭示了Vortex 3对反肾涡旋对的损耗机制。