长引水道高水头电站不同负荷条件甩荷对蜗壳压力的影响研究

为研究采用集中供水布置型式的长引水道高水头电站蜗壳进口端内水压力极值工况及其内在影响机理，在相同上下游水位的前提下，以有压输水系统瞬变流分析的特征线法(MOC)为基础，融合跟踪机组运行轨迹的单纯形寻优法以及系统状态方程，对单台和两台机组在不同负荷时的甩荷工况进行过渡过程数值模拟计算。结果表明：单机、两机以20%额定功率运行甩荷后易发生首相水锤，为蜗壳进口断面内水压力的极值工况。蜗壳进口端内水压力极值出现在导叶小开度运行时甩部分负荷的工况。蜗壳进口断面内水压力初始值和极值大小与机组负荷相关，机组初始出力越少，引水系统中水头损失越小，蜗壳进口端初始压力越高，甩荷后该断面内水压力值越高，且部分负荷运行甩荷后压力衰减速度越慢。机组运行方式对蜗壳进口端内水压力值及峰值出现时间有一定影响。研究成果可为同类型水电站的设计和运行维护工作提供参考。

Load rejection conditions affect pressure in spiral case of hydropower station with long diversion channel under high water head

The hydraulic conditions of hyropower stations with long diversion channels and high water head are complicated, it is necessary to clarify the extreme pressure conditions in the spiral case of the power units under centralized water supply arrangement and the intrinsic influencing mechanism. Assuming the water levels of the upstream and downstream of the hydropower plant are the same, we carried out simulation calculations for the transient process of the load rejection conditions of single and double power units under different loads using the method of characteristics (MOC), Simplex which can track the unit operation trajectory and the system state equation. The results show that the single unit and double units operating at 20% of the rated power are subjected to first-phase water hammer after load rejection, which is the extreme pressure condition in the inlet section of the spiral case. The study also shows that the extreme value of water pressure in the inlet section of the spiral case occurs in the case of partial load rejection when the guide vane operates at small opening. The initial pressure value and the extreme value in the inlet section of the spiral case are related to the unit load, the less the initial output of the unit, the smaller the head loss in the diversion system, the higher the initial pressure of the unit, and the higher the value of the water pressure in the inlet section of the spiral case after load rejection, and the slower the pressure decay after rejecting partial load. The operating mode of the power units has a certain effect on the extreme value of water pressure in the inlet section of the spiral case and its peak time. The research results can provide some reference for the design, operation and maintenance of the same type of hydropower stations.