| The inlet conduit is the transition section between the front of the pump station and the impeller chamber of the pump.The main function of the inlet is to speed up the water flow and to turn better and provide a good inlet condition for the inlet of the impeller chamber.The inlet conduit can be divided into the inlet conduit of the elbow pipe and the inlet conduit of the flare tube,the advantage of the inflow channel of the horn pipe is that the height of the channel is low,so the digging depth is smaller and the construction is convenient.The inlet conduit of the trumpet pipe requires a suitable high suspension height,a certain rear wall space and sufficient width so that the flow of water flows evenly into the.horn of the horn.If the design of the inlet conduit of the flare tube is improper,the flow and vortex will be produced,which leads to the asymmetry of the inlet of the impeller and the flow in the impeller,which causes the increase of the pump pressure pulsation,the intensification of the vibration and the deterioration of the working state of the pump,thus reducing the efficiency of the pump,the cavitation performance and safety of the pump.Therefore,in-depth study of the hydraulic design of the inlet pipe of the flare tube of the pump station is of great significance for theoretical research and engineering practice.In this paper,the influence of the main shape and size of the inlet conduit of the horn(including the height of flare tube,the bottom clearance and the back wall distance)on the performance of the pump device is studied by the combination of numerical simulation and experiment.The influence of the width of the inlet conduit on the side wall vortex and the formation of the side wall vortex are studied.Flow mechanism.First,the single factor method is used to simulate the full channel pump device including the water pump,including the water pump in the box shaped inlet conduit with different shapes and sizes.At the same time,the ratio of the axial velocity uniformity,the hydraulic loss of the inlet conduit and the efficiency of the pump device is introduced,and the comparison results are analyzed,and then the side wall is emphatically analyzed.The fine flow structure of the core region of the vortex and the development law of the tangential velocity near the vortex core.Finally,the flow field of the side wall vortex is observed by the V3V 3D body flow field measurement technique,and the results from the experimental results are compared with the numerical simulation results.The results of V3V test are in good agreement with that of CFX.The results of numerical calculation show that:(1)The height of flare tube has an important influence on the flow pattern and hydraulic performance of the inlet conduit.With the increase in the height of the flare tube,the velocity distribution of the typical section of the box inlet conduit and the pressure distribution of the horn of the flare tube tend to be uneven first and then tend to be disorganized.The velocity uniformity of the exit section and pump assembly efficiency are both increased first and then reduced,and the hydraulic loss decreases first and then increases.When Ht=AD0,the velocity distribution is the most homogeneous,the velocity uniformity is the largest,the hydraulic loss is the smallest,and the pump efficiency is the highest.Therefore,the height of flare tube is 0.3D0 to 0.6D0,and the optimal value is Ht=0.4D0.(2)The bottom clearance has a significant effect on the flow and hydraulic performance of the inlet conduit.When C<0.4ZD0,the flow pattern and hydraulic performance of the inlet conduit are poorer.When C=0.4A0?0.8D0,the flow pattern and hydraulic performance of the inlet conduit are better.When the flare tube is suspended high C=0.8D0,the flow pattern is the best,and the velocity uniformity of the inlet section is the highest,and the hydraulic loss is the smallest,and pump assembly efficiency is the highest.Therefore,the high value of flare tube is 0.AD0 to 0.8D0,and the optimal value is C=0.8D0.(3)The back wall distance has a great influence on the flow pattern and hydraulic performance of the inlet conduit.When T=0.8D0?1.0D0,the flow pattern and hydraulic performance of the inlet conduit are poorer.When T=1.0O0?1.6D0,the flow pattern and hydraulic performance of the inlet conduit are better.When the back wall is away from T=1.2D0,the flow pattern is the best,and the velocity uniformity of the inlet section is the highest,and the hydraulic loss is the smallest,and pump assembly efficiency is the highest.Therefore,the value of the posterior wall distance is 1.0D0 to 1.4D0,and the optimal value is T=1.2D0.(4)The width has a decisive influence on the whirl of the side wall of the inlet conduit.With the decrease of the width B of the channel,the diameter and range of the side wall vortex tube and the vorticity value of the vortex core region of the side wall of the typical cross section are increasing.The range of the value of B is from 2.8D0 to 3D0.The results of V3V test show that:The motion range of the side wall vortex is from one side of the inlet conduit to the flare tube along with the flow of water,and forms an obvious vortex tube with the interior of the horn and other vortices and dissipates in the interior of the impeller chamber.The distribution of the velocity distribution of the flow tangential flow in the vortex core region of the side wall is that the core region of the vortex core extends to the surrounding area and expands rapidly.The tangential velocity of the core region of the vortex core(R=0mm)is about 0,the velocity gradient reaches the maximum of about R=3?5mm,and the rotating flow in the vortex core region of the side wall is in accordance with the forced vorticity characteristics,and the V3V test is obtained.The results are in good agreement with the calculated results of CFX. |
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