Research On The Influence Of The GAP Change Of The Front Ring On The Hydraulic Performance Of The Centrifugal Pump

The clearance of the front ring is the radial clearance between the seal ring of the pump body and the front ring of the impeller,which has a great influence on the hydraulic performance of the centrifugal pump.In this paper,a centrifugal pump testbed is built independently,and the movable front ring of impeller with different outer diameter is specially designed and manufactured,which is installed on the impeller to change the size of the radial clearance formed by the front ring of the pump body,so as to achieve the purpose of changing the large and small clearance of the front ring on the same impeller.According to the test and simulation results of the front ring clearance of 0.2mm,0.4mm,0.6mm and 0.8mm,the influence of the front ring clearance on the hydraulic performance of centrifugal pump was studied.The primary coverage of this paper are as follows:1.Self built centrifugal pump test-bed,specially designed and manufactured the required test device.Under the full flow condition,the pump performance curve and cavitation performance curve were obtained under different front port ring clearance.The test results showed that the increase of front port ring clearance would lead to the decrease of lift and efficiency of centrifugal pump,and the pump is easier to cavitation,and its cavitation resistance performance is worse.It is found that the comprehensive performance of this type of centrifugal pump is the best when the clearance of the front ring is in the range of 0.2-0.4mm.2.Specially designed the pressure testing device of the pump cavity,processed the pressure taps at the different radii of the front and rear pump cavity respectively,and designed and installed the pressure stabilizing device system to ensure the accuracy of the test results.The pressure distribution curves of the front and rear pump chambers under normal working conditions and cavitation working conditions were obtained under different front ring gaps.The experimental results show that the change of the front ring gap has a great influence on the liquid pressure distribution in the front pump cavity,but a little influence on the liquid pressure distribution in the rear pump cavity.3.The influence of the clearance of the front ring on the axial force characteristics of the pump was studied.Because the pressure in the balance cavity area has a great influence on the axial force of the pump,a pressure tap is set up on the balance cavity pressure test device to test the pressure in the balance cavity area.The axial force curves of the pump under the normal and cavitation conditions are obtained under different front ring clearances.The test results show that the axial force of the pump increases when the front ring clearance changes,and the axial force of the pump is the minimum when the front ring clearance is less than or equal to the rear ring clearance.In addition,with the decrease of NPSHa,the axial force of the pump increases slowly at first.When the critical cavitation occurs,the axial force is the largest.If the NPSHa continues to decrease,the axial force of the pump decreases significantly after the complete cavitation.4.The numerical simulation of the full flow condition of the model pump was carried out,and the performance curve,cavitation performance curve,pressure distribution curve of the front and rear cavity,axial force characteristic curve,and the velocity distribution of the intersection area between the front ring gap and the impeller inlet were obtained under different front ring gap.The simulation results showed that the smaller the front ring gap,the better the hydraulic performance of the centrifugal pump.Finally,the results of the experiment are compared with the simulation results,and it is found that the experimental results are close to the simulation results.