竖井弯道段对进出水口水力特性影响研究

Research on influence of shaft bend section on inlet/outlet hydraulic characteristics

竖井进出水口弯道段(简称竖井弯道段)是控制出流是否均匀的关键体型,若设计不当,易出现偏流等问题。为比较竖井弯道段不同形式(肘型弯道段和S型弯道段)影响竖井进出水口水力特性的异同性,该文建立了大型竖井进出水口试验装置,并利用声学多普勒流速仪量测了出口拦污栅断面流速。研究结果表明:对于出流工况,竖井弯道段对出流均匀性起关键作用,肘型弯道段和S型弯道段均能获得理想的孔口流量分配;竖井弯道段形式的改变不能消除出口拦污栅断面底部负向流速,两种形式弯道段的出口拦污栅断面底部负向流速区高度基本相同;两种弯道段的水头损失相当,均占竖井进出水口水头损失的40%左右。对于进流工况,竖井弯道段对进口拦污栅断面流速分布和孔口流量分配无影响,两种弯道段的水头损失相当,均占竖井进出水口水头损失的60%左右。从水力学角度看,两种形式的弯道段对竖井进出水口水力特性的影响效果基本相同,但S型弯道段形状的细微变化对出流各孔口流量均匀性影响较大,极易导致出流不均匀,需要引起高度重视。

The bend section of the shaft inlet/outlet is the key shape to control whether the outflow is uniform. If it is not properly designed, it is prone to problems such as drift. In order to compare the similarities and differences of the two shaft bend sections(elbow bend section and S bend section) affecting the hydraulic characteristics `of the shaft inlet/outlet, in this paper, a large-scale inlet/outlet test device is established, and the velocity of the outlet trash rack section is measured by using the acoustic Doppler velocimetry. The research results show that the shaft bend section plays a key role in the outflow uniformity for the outflow condition. Both the elbow bend section and the S bend section can improve the flow distribution of each orifice;The change of the form of the shaft bend section cannot eliminate the reverse flow velocity at the bottom of the outlet trash rack section. The height of the reverse flow velocity zone at the bottom of the outlet trash rack section of the two forms of bend section is basically the same. The head loss is quite similar, accounting for about 40% of the head loss of the inlet/outlet. For the inflow condition, the bend section of the shaft has no effect on the velocity distribution of the trash rack section and the flow distribution of the orifice. The head losses of the two bend sections are equivalent, accounting for about 60% of the head loss of the inlet/outlet. From the perspective of hydraulics, the effect of the two forms of bend sections on the hydraulic characteristics of the shaft inlet/outlet is basically the same, but the subtle change in the shape of the S-shaped bend section has a great impact on the uniformity of the flow at each orifice of the outlet, which is very likely to lead to uneven outflow. It needs to be paid great attention to. The research results provide a reference for the design and construction of the shaft inlet/outlet of pumped storage power station.