基于数值模拟的气膜孔冷却效率经验公式的修正

An Improved Empirical Formula for Film Hole Cooling Efficiency Based on Numerical Simulation

气膜冷却在燃气轮机叶片冷却中具有明显优势和较强应用前景。已有的经验公式通常忽略气膜孔长径比(气膜孔长度/气膜孔直径)的大小对冷却效率的影响,但长径比与气膜倾角相关,会很大程度影响射流的流动形式,从而对冷却效率的分布影响较大。本文旨在通过数值实验构建一个能够较为准确地预测展向平均气膜冷却效率的经验公式,为初期叶片冷却结构的快速设计提供依据。本文首先通过数值模拟的方法分析了孔间距、气膜倾角和吹风比的大小对展向平均气膜冷却效率的影响,将上述参数总结归纳到所构建的经验公式中,使用Matlab对数据进行非线性拟合,最后与已有经验公式进行对比。结果表明,本文构建的经验公式在拟合效果方面要好于已有的经验公式且决定系数均大于0.9,具有较好的拟合优度。

Film cooling is a prospective cooling technique for maintaining and improving turbine working life with obvious advantages. The existing empirical formulas usually ignores the effect of the ratio of film hole length to the diameter L/D on the cooling effectiveness, but L/D is related to the surface inclination angle of film hole and the size of surface inclination angle of film hole greatly affects the flow pattern of the jet, and thus has a relatively large impact on the distribution of the cooling efficiency. The aim of this article is to construct an empirical formula through numerical experiments which can accurately predict the laterally averaged film cooling efficiency in the early stage of designing blade cooling structure. Therefore, the effects of film hole spacing, surface in-clination angle and blow ratio on the laterally averaged film cooling effectiveness were first inves-tigated by numerical simulations. The nonlinear fitting of the data was performed by using Matlab and were subsequently summarized as an empirical formula which is related to the above param-eters. Compared with the existing empirical formulas, the improved empirical formula can give a better prediction for cooling efficiency, whose coefficient of determination is greater than 0.9.