Study On Free Surface Vortex Of The Pump Sump And Prevent Measures

The free surface vortex is a common hydraulic phenomenon in front of the intakes of hydraulic structures such as diversion pipeline of hydropower station, spillway, diversion tunnel, large scale pump station,and ship lock. The free surface vortex will evolve into air entrainment vortex when it develops to a certain extent, which may seriously endanger hydraulic structures or hydraulic equipments. The mechanism of the free surface vortex formation and evolution are greatly complex. It is an urgent problem in the practical engineering to research the vortex phenomenon,its evolution law and to reveal its flow mechanism.Firstly the author tests the axial flow pump device. And through the analysis of test data, the result shows that under the condition that the blade put angle is 0 (?), rotating speed is 2400 r/min, the device’s highest efficiency is about 72.4%, the corresponding optimal flow rate is about 33.6L/s, the head is about 2.00m and the power is 0.995kW.In this paper, on the basis of the experimental observation, adopting international advanced V3 V non-contact 3 D body measurement technology to measure the whole flow field of the free surface vortex at different development stage. The evolution law and the changing law in space of the free surface vortex were obtained by analyzing the experimental data. In the evolution of the free surface vortex, circumferential speed distribution in the vortex core characteristic is the center of the vortex core values close to zero. The vortex circumferential velocity increases with the increase of the radius, When the increases to a certain degree and then decreases, there is maximum In the process of this change. Vortex circumferential velocity with radius change law does not change according to the spiral development stage. The circumferential speed along with the change of the radius is a similar rule. Free surface vortex in the different stages of evolution, the maximum circumferential velocity variation in the depth direction is basically similar, with the increase of takes section depth, circumferential velocity basically is to increase first, gradually increased to a certain value decreases, and its maximum speed is not on the surface, but to a certain depth below the surface. Whirlpool maximum circumferential velocity changes with the depth of cross section of law also does not change according to the spiral development stage.With circular cross section of radius increases, namely the same horizontal section ring near the vortex core value is more and more big, the circulation variation also gradually increase, vortex ring value with the change of the radius of law does not change along with the development of the vortex phase; With the increase of the surface profile location, ring value basically is becoming more and more big, and the radius of circular cross section, the greater the increase of the amplitude is, the greater the vortex ring value with sectional depth change rule will not change along with the development of the vortex phase.Through the floating ball is placed into the pool surface, increase into the submerged depth of the water intake and on into the pool and cover the surface of the method can effectively eliminate the free surface vortex.