尾水管压力脉动的模拟与现场实测

Pressure oscillations in a hydraulic turbine draft tube

通过求解包括导叶、转轮、尾水管3大过流部件在内的水轮机流道内的三维不稳定Reynolds平均Navier-Stokes方程,获得了不同开度部分负荷下的尾水管压力脉动特征和涡带特征.计算采用了RNG k-ε模型.对所计算的水轮机,在尾水管进人门中心对压力脉动进行了现场实测.计算与实测的比较表明,在开度为65%～80%的范围内,计算所得涡带压力脉动低频频率与实测值吻合良好; 在80%左右开度下,幅值预测也很准确,但65%左右开度下,幅值偏差略大; 结合尾水管内涡带运动特征,对计算方法进行了评价: 由于所采用的k-ε系列模型为统计模型,计算的压力脉动未能反映实测中出现的高频成分.

The flow in a hydraulic turbine including the guide vane, the turbine and the draft tube was analyzed by solving the three-dimensional, unsteady Reynolds-averaged Navier-Stokes （RANS） equations with the RNG k-ε turbulence model to investigate the pressure fluctuations due to the vortex rope at partial loads. The numerical results compared well with unsteady experimental data. The analysis predicted the low frequencies due to the vortex precession that occurs at 65%- 80% of the optimum opening; The amplitudes at 80% opening were predicted accurately but were less accurate at 65% opening, perhaps because the high frequency turbulence can be not accurately predicted by the k-ε model since it is an ensemble averaged model.