Hydraulic Characteristics Of Two-way Vertical Axial Flow Pump Device With Siphon Discharge

In the riverside or lakeside area,the water level change of the over channel is more complicated,and the one-way pumping station is not enough to effectively meet the water diversion and drainage needs,and the two-way flow channel pumping system is a pump system that satisfies the water diversion and drainage needs and minimizes the use of land resources.Considering that the axial flow pump is equipped with a two-way flow channel,the device has a single current interruption mode,and the gate is responsible for the problem of excessive flow interruption,and the siphon discharge passage can be broken by the vacuum breaking valve.The umbrella-shaped two-way vertical pump unit came into being.The umbrella-shaped two-way vertical axial flow pump device is a novel two-way pump device form that combines the advantages of the two-way flow passage and the siphon vacuum break valve.The problem of single-way flow interruption mode is solved,the working gate is reduced,and the rapid gate interruption is changed to siphon current interruption.The siphon flow channel has reliable flow interruption,simple operation and convenient maintenance.In this paper,the hydraulic characteristics of the two-way vertical axial flow pump device using siphon effluent are analyzed by numerical simulation,and the influence of the structure of the annular siphon outlet chamber and the bottom elevation of the outlet passage on the hydraulic characteristics of the pump device is compared.The unsteady calculation of the transient process of siphon effluent was carried out.The process of siphon formation was analyzed,and the siphon formation process time under three different working conditions was compared.The CFX software was used to calculate the constant prototype numerical value.The pumping device of the circular siphon outlet chamber with two different structures was compared and analyzed.It was found that the recirculation zone of the siphon outlet chamber of the curve expansion tube was smaller,the front flow rate was higher,and the hydraulic power was higher.The loss is about 0.18m smaller than the siphon outlet chamber of the straight cone expansion tube type.The highest efficiency under the design condition of the curve expansion tube siphon outlet chamber is 4.12 percentage points higher than that of the straight cone expansion tube siphon outlet chamber,and the difference is obvious.The constant calculation of the constant pressure values of three pumping devices with different bottom lift heights shows that the bottom lift of the water flow channel has little effect on the flow state of the water flow channel,but the flow velocity of the cross section is increased.Analyze the data under design conditions,large flow and small flow conditions,and the hydraulic loss will increase when the bottom height is raised,and the minimum when it is not lifted.The efficiency of the three devices is very small,and it can be considered that the lift height at the bottom of the water flow channel has little effect on the hydraulic characteristics.Considering the performance and maintenance space,the optimal solution was selected to analyze the hydraulic characteristics under multi-blade angle.When the blade angle is 0°,the highest efficiency is 72.13%under the condition of Q=7.25m3/s.The highest efficiency is also over 71%at the other three blade angles.At all angles,the flow velocity distribution uniformity of the impeller inlet section is greater than 90%,and the influent flow state is good.The transient scheme calculation is performed for the hydraulic transition process of the two-way vertical axial flow pump device with siphon discharge.The hydraulic transient process formed by siphon can be divided into three stages:water flow driving gas,mixed exhaust gas,and siphon formation.The whole process is completed in about 100s.The duration of the water flow compression phase is 2.5 s,and the mixing and exhausting phase is as long as 87.5 s.The pressure at the top of the hump rises and then falls with time,eventually forming a large negative pressure.The ehange in the pressure at the top of the hump i5 rapidly inereased at the initial moment and reaches a maximum at the end of the water flow compression phase.The pressure at the top of the hump begins to gradually decrease in the stage of mixing and exhausting.The pressure in the range of 24?2 5s is already negative.At this time,it is still in the middle of the stage of mixing and exhausting.At this time,the water level in the ring siphon outlet has risen to a certain level.At the height,the main area where the remaining air is present is the top of the hump.During the follow?up process,the pressure at the top of the hump continued to decrease,and the pressure was-0.9 kPa at 60 s,after which it became stable and siphon formed.When the water level is lowered by 0.5m,that is,when the head is reduced by 0.5m,the speed of siphon formation is faster,the speed of pressure change is faster,and the pressure value of the siphon top is reduced by 5kpa.The numerical simulation results show that the predicted maximum efficiency of the two-way vertical axial flow pump device is above 72%,and the performance is excellent;the siphon formation process of the pump device is short,and the pressure at the top of the hump is stable,which can meet the operation requirements of the pump device.