起动过程涡轮叶片瞬态温度场的准稳态处理研究

Quasi-Steady Processing of Transient Temperature Behavior of Turbine Blade during Start-up

考虑燃气涡轮发动机起动过程涡轮叶片与高温燃气的对流换热及叶片内部的热传导,通过瞬态流热耦合计算和准稳态处理两种方法对涡轮叶片换热特性进行了研究,分析了叶片热惯性带来的温度滞后效应,探索了一种对发动机起动过程进行准稳态处理的数值模拟方法,实现了对涡轮叶片瞬态温度场的快速求解。采用商业化软件ANSYS CFX 2019 R2对涡轮叶片分别进行流热耦合和非定常数值计算,结合外换热程序“NPUSTAN7Z”求解叶片型线上的换热系数,并对叶片表面网格节点按照“K-近邻算法”进行三维数据插值,得到计算涡轮叶片非稳态导热的第三类边界条件。分析涡轮叶片的瞬态温度场,发现起动过程中金属叶片的热惯性导致其温升慢于来流的温升,其内部存在一定的纵向温度梯度和横向温度梯度,中弦滞后>前缘滞后>尾缘滞后,叶片中下部温度滞后>叶片上部滞后。通过对比瞬态耦合计算与准稳态计算的结果,认为准稳态的方法可以快速准确地求解发动机起动过程涡轮叶片的瞬态温度场。

Considering the convective heat transfer between turbine blades and high temperature gas and the heat conduction inside the blades during the start-up process of gas turbine engine,the transient heat transfer characteristics of turbine blades were studied through two methods,namely,CHT(conjugate heat transfer)simulation and quasi-steady processing,and the temperature hysteresis effect caused by thermal inertia of blades was analyzed,a quasi-steady processing method was explored to simulate the typical operating point of the engine during start-up,and the transient temperature behavior of the turbine blades was solved quickly.The CHT simulation and unsteady numerical calculation of turbine blades were carried out by the commercial code ANSYS CFX 2019 R2.Combined with the external heat transfer program“NPUSTAN7Z”,the heat transfer coefficient on the blades profile was solved,and the three-dimensional data interpolation was conducted for the grid nodes on the blades surface according to the“K-nearest neighbor”algorithm,and the boundary conditions for calculating the transient heat conduction of turbine blades were obtained.By analyzing the transient temperature behavior of the turbine blades,it was found that the temperature rise of the metal blades was slower than that of the incoming flow due to the thermal inertia of the metal blades during the start-up process.There were some longitudinal and transverse temperature gradients in the metal blades.Temperature hysteresis in middle chord>leading edge>trailing edge,temperature hysteresis in middle and lower part of blades>upper part of blades.By comparing the results of the CHT simulation and the quasi-steady processing,it was considered that the quasi-steady processing can quickly predict the transient temperature behavior of turbine blades with fairly good accuracy during the starting process of gas turbine engine.