基于SAS的SST和ZLES高级湍流模型对灯泡式水轮机的流动数值模拟和效率预测  

Efficiency Prediction for a Low Head Bulb Turbine with SAS SST and Zonal LES Turbulence Models

作　　者：D Jogt(斯洛文尼亚) D Jolt etc.

出　　处：《国外大电机》2018年第2期44-51,64,共9页

摘　　要：为了建立一个精确可靠地模拟低水头水轮机的内部流态数值模拟模型，在一个三桨叶灯泡式水轮机上进行了数值模拟和测量结果的比较。对转轮桨叶的最大桨叶角度、最优桨叶角度和最小桨叶角度三个角度的两个试验水头进行了数值分析。稳态模拟时，在最小的桨叶角度，效率预测是相当准确的，但是在最优和最大桨叶角度，因为低估了主轴扭矩的影响，且尾水管中模拟结果不正确，不能准确的预测效率。用SST（湍流剪应力传播模型）进行瞬态模拟的结果也不尽如意，但将SAS的SST和LES（大涡模拟）模型结合后对效率预测的准确性有着显著提高。从流体的涡流结构，涡流粘度值和尾水管中的水头能量损失等结果可以看出，SAS和区域LES这些湍流模型之间有很强的相互依赖性。而且，使用有界中心差分格式代替高分辨率差分格式的效果是显而易见的。为了测试网格密度对效率预测的影响，采用四种不同网格密度进行模拟。基本网格和加密网格结果的差异很小，但在粗网格上获得的结果并不令人满意。A comparison between results of numerical simulations and measurements for a 3-blade bulb turbine is presented in order to determine an appropriate numerical setup for accurate and reliable simulations of flow in low head turbines. Numerical analysis was done for three angles of runner blades at two values of head. For the smallest blade angle the efficiency was quite accurately predicted, but for the optimal and maximal blade angles steady state analysis entirely failed to predict the efficiency due to underestimated torque on the shaft and incorrect results in the draft tube. Transient simulation with SST did not give satisfactory results, but with SAS and zonal LES models the prediction of efficiency was significantly improved. From the results obtained by SAS and zonal LES the interdependence between turbulence models, vortex structures in the flow, values of eddy viscosity and flow energy losses in the draft tube can be seen. Also the effect of using the bounded central differential scheme instead of the high resolution scheme was evident. To test the effect of grid density, simulations were performed on four grids. While a difference between results obtained on the basic grid and on the fine grid was small, the results obtained on the coarse grids were not satisfactory.

关 键 词：流动数值模拟 灯泡式水轮机 预测效率 湍流模型 SST SAS 低水头水轮机 中心差分格式 

分 类 号：O357.5[理学—流体力学]