导叶不同步装置降低蜗壳进口压力的机理研究

Analysis on the mechanism of lowing casing inlet pressure through misaligned guide vanes

利用基于特征线原理的蜗壳进口压力的表达式 ,结合含导叶不同步装置的水泵水轮机的全特性曲线 ,对高水头抽水蓄能电站中 ,低比转速水泵水轮机甩负荷时 ,导叶不同步装置降低蜗壳进口压力的机理进行了理论分析和探讨。导叶不同步装置的及时投入 ,增大了流量特性曲线在“S”特性影响区内的正斜率 ,减小了水轮机甩负荷时每一时间步长内的蜗壳进口压力的上升幅值 ,从而在一定程度上降低了蜗壳进口压力的最大值 ,但并不改变蜗壳进口压力的双峰特性。另外 ,在水轮机甩负荷工况的同时 ,MGV装置的延时投入时间越短 ,预开启导叶的附加开度的增加速率越快 ,蜗壳进口压力的最大值就降低的越多。

Based on the mathematical expression of casing inlet pressure, and the new complete characteristic curves of reversible pump turbine with misaligned guide vanes (MGV), the mechanism of lowing the casing inlet pressure, which is caused by turbine load rejection in the high-nominal head pumped storage plant, is analyzed. If the turbine load is tripped and MGV devices is to work on time, the positive rate of gradient of the flow S-curve in its effected zone becomes bigger, the increment of the casing inlet pressure in each time-step decreases. As a result, the maximum casing inlet pressure is reduced. However, it does not change the character of double peaks of casing inlet pressure within the duration of closure law of the aligned guide vanes. The result also shows that the smaller the delayed time is, the quicker the MGV opens if compared with the aligned guide vanes, the more the maximum casing inlet pressure will be lowed.