The characteristics of a liquid jet pump Liquid jet pump is a non-rotating parts of the fluid machinery, which is through the jet entrainment effect and turbulent diffusion of the role of the working fluid to pass the energy to the slits suction liquid. Because of its simple structure, compact, good sealing performance of the pump body, hydraulic transmission Gong Li, can achieve long-distance control, and therefore suitable for high temperature, high pressure, high vacuum, deep water, strong radiation and strong corrosion conditions. At present, jet pump technology has been widely used in many fields at home and abroad, and its application in plate filter is a typical successful example. 2 liquid jet pump structural parameters jet pump structural parameters include area ratio m, throat l2, throat length l4, roar pipe inlet angle α1 and diffusion angle α2 five factors. Where m = F2 / F1 = (d2 / d1) 2 is expressed by describing the performance of the liquid jet pump and the following three parameters: flow ratio q = Qb / Qa head ratio h = [(HcZc + Vc2 / 2g) Efficiency value η = qh / (1-h) 1.2 The structural parameters of the jet pump on its performance According to a large number of domestic and foreign scholars, when the range of values ​​is: m = 2-9, l2 = 1-6d0, l4 = 4-9d2, α1 = 150-1200, α2 = 0-140, v0 It can be seen that the influence of each structural parameter on its performance is as follows: (1) The area ratio is the main parameter that affects the jet pump, and m = 3-4 is the high efficiency zone. (2) throat distance l2 = 1.0d0, the jet pump has a high efficiency point. (3) The diffusion angle has a great influence on the performance of the jet pump. When 40 <α2 <100 is the high efficiency area of ​​the jet pump. (4) The inlet angle of the throat has less effect on its performance. (5) The length of the throat has a great influence on the efficiency of the jet pump. Because the experimental result is different with the selected range of the boundary conditions, the influence of the various factors on the performance of the jet pump varies. 3 test jet pump vacuum generated by the system jet pump test device consists of filters, hydraulic pumps, motors, pressure control valves, globe valves, flow meters, jet pumps and vacuum gauges and other components. See test principle diagram 3. 4 Test results and conclusions (1) According to the above-mentioned various structural parameters of the jet pump performance, we have adopted the value of the high efficiency range, taking the area ratio m = 3, the throat distance l2 = 1.0d0, diffusion angle α2 = Throat into the α1 = 120, the length of the hose l4 = 6d2 (2) jet pump nozzle diameter was l0 = 4mm, d0 = 6m, the test results shown in Figure 4. According to the test results, under the premise of adopting the structural parameters, the negative pressure of the jet pump we developed can reach -0.06MPa, and the vacuum value increases as the difference of the inlet and outlet pressures increases. 5 jet pump in the plate filter on the application of our principle, it will be used in the following filtration system. In practical applications, we apply this jet pump to the plate filter to obtain a good sealing effect, so that the whole filtering device has no leakage phenomenon. Therefore, the use of jet pump features cleverly applied to a variety of demanding, leak-free system, the negative pressure sealing effect is very obvious.