泵站用轴流泵鱼友好型设计及鱼类存活率预测

Design and fish survival rate prediction of fish-friendly axial-flow pump for pumping stations

传统泵站使用中存在大量鱼类死亡现象.为了提高鱼类流经泵站流道后的存活率,采用与试验值吻合度较高的叶片撞击模型,预测了原型泵不同工况下的鱼类死亡率:理论上设计流量点鱼类死亡率高达68%.基于叶片撞击数学模型,提出了提高鱼类存活率的鱼友好型设计方法,分析了各鱼友好型设计对提高鱼类存活率的效果,其中叶片数和转速是影响撞击概率的主要因素,而叶片数是导致扬程变化灵敏度较低的因素;前缘弯掠大幅降低了垂直前缘的撞击速度分量,是影响撞击死亡率的主要因素,加厚型线头部是影响撞击死亡率的次要因素,但两者会加剧径向流动,降低叶片效率及汽蚀性能.经鱼友好型设计后,鱼类死亡率整体控制在30%以下,设计工况点下的鱼类死亡率由68%降低至13%,效果显著.该研究可为鱼友好型泵及泵站的开发应用提供参考.

A large number of fish suffer from injury and mortality when passing through a traditionally designed pumping station. In order to improve the survival rate when fish passing through the flow channels in a pumping station, fish mortality rates are predicted under various operational conditions in a conventional axial-flow pump by using a blade strike model which is with a better accuracy against experimental data. It is shown that the fish mortality rate at the design point is up to 68% theoretically in that pump. Based on this model, a fish-friendly hydraulic design approaeh is proposed for an axial- flow pump to have better fish survival rate, and effects of a few design parameters on the rate are analyzed. It is turned out that number of blades and rotational speed are two major factors influencing blade strike probability. Because the pump head is almost twiee sensitive to the rotational speed than to the number of blades, the impeller is kept having two blades to reduce the blade strike probability for fish. The chord length of blade is increased to cope with the head drop caused by reduced number of blades. To limit the axial length of pump, the increased proportion of chord length is a little bit small. The forward swept and extended leading edge can reduce strike velocity, i.e. the velocity component perpendicular to the leading edge, significantly, thus the leading edge is the primary factor affecting strike mortality rate, while the thickened leading edge is the secondary factor for the rate. However, these two factors can induce a stronger radial velocity component, causing a low hydraulic efficiency and poor cavitation performance. The fish mortality rate is all below 30% at any operating points, and the rate has been declined to 13% from initially 68% at the design point as fish passing through the fish-friendly pump, thus fish survival is remarkable. This study can provide a reference for development of fish-friendly axial-flow pump and its application in pumping stations.