Study On Liquid Flow Characteristics In The Front Pump Chamber Of Centrifugal Pump

Fluid machinery is a kind of general machinery for energy conversion,and now it is widely used in various fields of national economic construction.Centrifugal pump is a large,wide range of fluid machinery used to transport liquids.At present,in the research and numerical simulation of centrifugal pumps,the impeller wear-rings and pump chambers are often neglected,so the performance prediction of centrifugal pumps will produce some errors.Generally,the clearance of pump chamber is smaller,the spatial scale of the flow is much smaller than the internal flow of the impeller,but the internal flow structure is very complex.In the past 30 years,with the development of computer technology and computational fluid dynamics method,the CFD technology has been more and more widely used in the performance prediction and internal flow research of centrifugal pumps.For current computing resources,the numerical simulation has become possible considering the effect of clearance,if the numerical simulation method is used to study the whole flow including the clearance of pump chamber,the simulation results will be closer to the actual situation,it has a very important significance for improving the design of centrifugal pump.In this paper,for a single stage centrifugal pump,numerical simulation is performed to study on the whole flow field of centrifugal pump based on RANS equations and RNG k-?turbulent model.The whole flow field includes front and back pump chambers,impeller wear-ring,impeller passage,volute casing,inlet section and outlet section.The numerical result is verified by the experimental data,and they are in good agreement.On the basis that the numerical simulation result is consistent with the experimental data on the performance of centrifugal pump,under different flow rates,the variation law of circumferential velocity and radial velocity of the front pump chamber liquid is obtained axially at a given radius with the circumferential angle 0°,90°,180°,270° and at a given circumferential angle with the radius 155mm,175mm,195mm,215mm.And the flow characteristics of the liquid in the pump chamber are studied by means of pressure,velocity and vorticity.Furthermore,the effect of the front pump chamber clearance on the pump performance is studied.Under different clearances of front pump chamber,the variation law of circumferential velocity and radial velocity of the front pump chamber liquid is obtained axially at a given radius with the circumferential angle 0°,90°,180°,270° and at a given circumferential angle with the radius 55mm,175mm,195mm,215mm.Finally,the unsteady conditions are investigated.Under different clearances of front pump chamber,the variation law of circumferential velocity and radial velocity of the front pump chamber liquid is obtained axially at a given radius with the circumferential angle 0°,90°,180°,270° and at a given circumferential angle with the radius 55mm,175mm,195mm,215mm.The study shows that the numerical simulation results of the head and efficiency of the centrifugal pump are in good agreement with the experimental data by the numerical simulation method in this paper.The results show that the flow field distribution is obviously non axisymmetric in front pump chamber.The distribution of circumferential velocity and that of radial velocity are similar along axial direction in front pump chamber,but the distribution law is different along circumferential direction and radial direction.The study found that the rotating angular velocity of the fluid is smaller near the pump casing,and the radial pressure difference overcomes centrifugal force to make fluid enter the front pump chamber through the volute chamber,the fluid enters the impeller inlet through the impeller wear-ring,so the leakage is produced.Because of the influence of leakage,the impact loss is larger at the impeller inlet.With the increase of the clearance of the front pump chamber,the leakage velocity of the liquid in the front pump chamber is decreased,the energy loss in the front pump chamber is also reduced,which makes the head increased accordingly.In the unsteady conditions,the circumferential velocity of the liquid in the core zone of the front pump chamber is obtained axially at a given circumferential angle 180° along different radii.It remains unchanged at the same radius,but is varied along the radial direction,and is gradually decreased from inside to outside.In addition,the researches of this paper provide some suggestions for the complex flow phenomena in the pump chamber,which will have an instructive significance for the design of the centrifugal pump chamber.