测试布局对涡轮效率的影响研究

Effects of Rake Measurements on Turbine Efficiency

关键词:  高压涡轮  性能试验  近壁边界层模型  测试布局  等熵效率

Key words:  High pressure turbine  Performance experiment  Boundary layer model near the end wall  Rake measurements  Isentropic efficiency

摘要:

在涡轮稳态性能试验中，由于探针几何堵塞限制，进/出口测量截面上过少的测点以及近端壁流场信息缺失影响涡轮等熵效率的评估精度。本文基于涡轮出口截面近壁边界层与平板湍流边界层速度分布相似的假设，首先发展了涡轮近壁边界层总温、总压计算模型，然后利用PW E³单级高压涡轮的数值计算结果，分析发现此近壁边界层模型能大幅改进涡轮测试效率的精度，轮毂近壁测点位于5%~10%叶高、机匣近壁测点位于90%~95%叶高时，近壁边界层模型修正的涡轮效率精度最高。测试截面位于涡轮出口3倍转子叶根轴向弦长下游时，在不同的涡轮工况下，涡轮的修正效率与CFD全流场计算效率的误差小于0.3%。利用此模型，进一步分析了探针周向、径向测点数对涡轮效率的影响，获得了高精度测试效率所需的最少周向测点数为5，最佳径向点数可取7~10。获得的试验数据后处理方法以及测试探针布局准则，能用于指导工程上涡轮性能试验方案设计以及试验数据后处理。

Abstract:

It is believed that the blockage caused by the geometry of probes, insufficient probes at the measured surface of inlet/exit and the missing of flow information in end wall roughly affect the accuracy of isentropic efficiency in the steady performance experiment of turbine. The calculation model of total temperature and total pressure near the end wall is proposed in this work, which is based on the assumption that the distribution of velocity of boundary layer near the end wall at the turbine exit is similar to flat plate turbulent boundary layer’s. According to the numerical analysis of the single-state high-pressure turbine (PW E³), it is found that the accuracy of isentropic efficiency in the turbine experiment increases greatly due to the application of the calculation model. And the turbine efficiency accuracy is highest when the probe near the hub is in the range of 5% to 10% blade height and the probe near the tip is in the range of 90% to 95% blade height. When the measured surface is located downstream of the triple axial chord length of rotor root at the turbine exit, the errors between corrected isentropic efficiency and numerical results are below 0.3% in different conditions. The model mentioned above is used to further study the effects of circumferential and radial probe number on the turbine efficiency. The results show that the least circumferential probes can be 5 and optimal number of radial probes can be 7 to 10 to meet the requirement of the efficiency accuracy in the experiment. It can be concluded that the obtained post-processing method of experiment data and the criteria of rake measurements can be used in the experimental design of turbine performance and post-processing of experiment data in engineering application.