源项冷却模型的建模以及在平板和涡轮的应用

Modeling of Source Cooling Model and Applications in a Plate and a Turbine

关键词:  源项冷却模型  变比热  气膜冷却平板  可行性  高压涡轮

Key words:  Source cooling model  Variable specific heat  Film cooling plate  Feasibility  High-pressure turbine

摘要:

为了解决由于划分冷气腔和尺寸过小的多排气膜冷却孔导致网格量过大的问题，本文基于NUAA-Turbo平台，在气膜冷却孔出口处建立适用于变比热条件下的源项冷却模型来代替冷却气体从孔内流出，并且在孔内建立换热模型，用于模拟孔内的对流冷却。对气膜冷却平板算例气动研究发现：在吹风比为1.0时，计算值与试验值相吻合。而对吹风比为1.5的孔下游近壁处计算时，发现流向速度计算值与试验值存在11.1%的误差，但小于商用软件44.4%的误差，尽管发现优化后的源项冷却模型不能很好反映下游近壁处法向速度分布，但计算精度在商用软件源项冷却模型基础上有25%的提高。为了证明该方法的可行性，对气冷高压涡轮MT1导叶的等熵马赫数以及平均努塞尔数等相关实验数据与计算数据作了对比，研究发现：在吸力面和压力面计算值与试验吻合较好，而在无冷却气膜覆盖的叶片尾缘和叶片前缘等局部位置计算值与试验值存在误差。研究表明：优化后的源项冷却模型能够较为准确地模拟冷却射流的宏观特征，该方法对工程上气冷涡轮的设计有一定的应用潜力。

Abstract:

In order to solve the problem of excessive mesh caused by partitioning the cooling chamber and multi-film cooling holes with too small size, based on the NUAA-Turbo platform, a source cooling model suitable for variable specific heat conditions is established at the outlet of the film cooling hole instead of the cooling gas flowing out of the hole, and establishing a heat transfer model inside the hole simulates convective cooling in a hole. A pneumatic study of the film cooling plate example found that when the blowing ratio is 1.0, the calculated value agrees with the experimental value. When calculating the near wall with a blow ratio of 1.5, the error between the calculated value of the flow velocity and the test value is 11.1%, but less than the error of 44.4% of the commercial software. Although the normal velocity prediction of the optimized source cooling model is not very good, but the calculation accuracy is 25% improvement based on the commercial software source cooling model. In order to prove the feasibility of this method, the experimental data of isentropic Mach number and average Nusselt number of air-cooled high-pressure turbine MT1 are compared with the calculated data. It is found that the calculated values on suction and pressure surfaces are in good agreement with the experimental data. However, there are errors between the calculated and experimental values at the local positions such as the trailing edge and leading edge of the blade without cooling film coverage. The research shows that the optimized source cooling model can accurately simulate the macroscopic characteristics of the cooling jet. This method has certain application potential for the design of the gas-cooled turbine in engineering.