考虑精铸变形的涡轮叶片气膜冷却效率灵敏度计算方法研究

Calculation Method of Turbine Blade Cooling Efficiency Sensitivity Considering Deformation of Investment Casting

精铸加工使得涡轮叶片几何结构与设计之间产生随机性偏差,这一偏差对叶片气膜冷却效率造成不确定性影响。涡轮叶片外形偏差的不确定性是几何层面的小扰动问题。本文通过精铸模拟建立了涡轮叶片精铸变形模型。基于PIV与数值模拟建立了适用于流热耦合计算的Realizable k-epsilon湍流模型,建立了考虑叶片变形的气膜冷却效率灵敏度计算方法,计算了涡轮叶片的气膜冷却效率随吹风比变化的灵敏度。结果表明:涡轮叶片精铸产生的变形越大,对原有气膜冷却效率的损失越大。叶片整体平均形变0.25 mm使得整体气膜冷却效率损失约5%,局部形变如叶尖叶片后缘处的0.70 mm可使叶尖平均气膜冷却效率损失约8%。由灵敏度分析确定的精铸后气膜冷却效率相对误差较明显,达到了1.62%。

The precision casting process results in a random deviation between the turbine blade geometry and the design,which has an uncertain effect on the blade air cooling efficiency.The uncertainty of turbine blade contour deviation is a minor disturbance problem in geometry.A model for deformation in the investment casting of the turbine blade is established by using the investment casting simulation.According to PIV and the numerical simulation,a realizable k-epsilon turbulence model for fluid-heat coupling calculation was established.A sensitivity calculation method of cooling efficiency considering blade deformation was established,and the sensitivity variation of the turbine blade air-cooling efficiency with the blow ratio was calculated.The results show that the greater the deformation of turbine blades is,the greater the loss of the original cooling efficiency.The overall average blade deformation of 0.25 mm makes the overall air-cooling efficiency loss of about 5%,and the local deformation such as 0.70 mm at the rear edge of the blade make the average air-cooling efficiency to be a loss of about 8%.