低水头贯流式水轮机运行特性数值仿真

Numerical simulation on running characteristics of low head pit turbine

通过建立非稳态过程的三维湍流数值模拟方法,设定进口压力呈周期性变化,且在转轮转速处于变化和不变的情况下,对某种新型无调速机构的低水头贯流式水轮机的运行特性进行了数值模拟.数值计算结果表明:在转轮转速随进口压力变化,且进口压力呈振幅为14%的正弦变化时,转速增大和减小的幅度分别为0.76%,0.21%,且其变化趋势滞后进口压力变化1/4周期;而流量的变化在极值处分别增大8%和2.5%;受进口压力变化的影响,转速变化时水轮机效率的下降幅度10.76%大于上升幅度4%.结果同时揭示了在2种情况下,水轮机力矩、流量、功率以及效率随时间的变化规律,并分析了在进口压力变化过程中,机组转轮区子午截面、转轮叶片压力场的瞬变过程,可为电站后期电气控制设备的选型提供参考依据.

Through the establishment of unsteady state process of three-dimensional turbulence numerical simulation,operation characteristics of a new low head pit turbine without governor device were simulated under both the constant and varied runner rotation speed conditions while the inlet pressure was changing periodically. The numerical results show that,with 14% changing of the inlet pressure,the rotation speed change is up to 0. 76% and down to 0. 21% and the rotation speed fluctuation is0. 25 cycle delayed than that of the inlet pressure. In addition,the flow rate change is up to 8% and2. 5% at the peak value,as well as the efficiency change is down to 10. 76% and up to 4%. The variation law of turbine torque,flow rate,power and efficiency with time was revealed,and in the variation process of the runner,the transient performance of runner flow in both conditions was analyzed,which can provide rational basis and suggestions for the electrical control equipment selection of a power station.