Study On Operation Characteristics Of Two-way Passage Axial Flow Pump Device Under Special Operating Conditions

In areas with complex hydrology and terrain,pump stations are often responsible for drainage and water diversion simultaneously.Two-way passage axial flow pump is widely used in pumping stations all over the world because of its compact structure,easy installation and low cost and so on.Two-way passage axial flow pump is usually operated under the abnormal conditions because of the particularity of its work environment.Therefore,in order to ensure the safe and stable operation of the pump device,it is necessary to study the mechanism of the internal flow fields of the pump device under these special conditions.The main content and innovations of this thesis are as follows:1.A two-way passage axial flow pump is used as the research object.For the first time,the CFX was used to simulate the unsteady flow field in pump device when it is under the negative head condition,forward runaway condition and reverse runaway condition.The SST k-? turbulence model was used to calculate the characteristics of pump device under three special conditions.And then,conduct model test in the four quadrant test bench.The comparison of performance curves simulated with model test data of three special conditions was acquired and analyzed.It shows that calculated result has a good agreement with the experimental results,which indicates that the numerical simulation is reasonable for calculating abnormal conditions and can be used to analysis the internal flow fields.2.In order to study the internal flow fields of special work conditions for the two-way passage axial flow pump,the pressure distribution,velocity distribution and vortex distribution were analyzed in this thesis for the first time.The analysis result shows that the flow fields is relatively stable under the reverse runaway condition.The pressure distribution on suction surface of blade is not rule under negative head condition and forward runaway condition,which shows that flow is disorder here.Flow separation phenomenon appears in the blade leading when pump is under negative head condition and forward runaway condition.However,the same phenomenon appears in the tail of blade,and its area become smaller.Vortex distribution is affectedby impeller vanes under negative head condition when it is affected by guide vanes mainly in reverse runaway condition.Combined with the comparison between numerical value and experimental one,under reverse runaway condition,water flow impact the original working surface of blade,which makes its flow fields stable and the numerical values are very close to the experimental ones.3.Vertical axial flow pump is greatly influenced by axial force.For the first time,the axial force variation of impeller for the two-way passage axial flow pump under large flow and negative lift conditions is studied.It is found that axial force decreases with increasing flow rate and becomes negative when the lift is about-3 meters.4.When pump device is running under the abnormal conditions,the first concern is the operation safety problem of pump device.In order to study the influence of the internal flow fields for the two-way passage axial flow pump device on the structure of the impeller under special conditions,fluid solid coupling analysis was used under negative head,forward runaway and reverse runaway conditions firstly.The study found that the relatively large deformation exits on the leading,middle part and tail of blade's rim when the pump device just enters the negative head condition.However,deformation areas gather on the leading and tail of blade's rim when the head becoming smaller,and the leading of blade's rim is most deformed.There is a larger stress area near the rim of the blade pressure surface,while on the suction surface,the equivalent stress decreases from the blade leading to the circumferential direction.The equivalent stress in general increases with the increase of forward runaway head.Under the reverse runaway condition,the maximum deformation of blade exits on the tail of blade's rim wheel rim,in other areas of the blade,the deformation is small.With the increase of the runaway head,the maximum deformation increases,and the deformation area becomes larger,extending to the middle.At this time,the equivalent stress is mainly concentrated in the tail of the impeller blade,and the equivalent stress of the pressure surface of the blade is greater than that of the blade suction surface.