Research On The Influence Of The Flow In The Wear Ring On The Internal And External Characteristics Of Disc Pump

With the development of petrochemical industry,as well as the progress of medical and aerospace industry,the ability of pumping high viscosity,high hardness,large particles,high gas content fluid medium is facing new challenges.The disc pump studied in this paper is a kind of centrifugal pump,but it can overcome the inherent limitations of the centrifugal pump to transport these special fluid medium,so disc pumps have attracted people’s attention in areas where it is difficult to transports special fluid media.The internal flow of the disc pump has a direct impact on its performance,and it also has a direct guiding significance for the analysis of its flow characteristics and mechanism.In the existing research of disc pumps,most of them ignore the influence of the leakage flow in the ring clearance.The leakage flow caused by the gap between the ring and the main flow of the impeller inlet will interact and interfere,which will have a certain impact on the inlet and internal flow conditions of the disc pump,hydraulic performance and the distribution of impeller load.In this paper,through the combination of experimental testing and numerical calculation research route,the leakage flow in the ring gap of disc pump is taken as the research object,the effects of the leakage flow on the inlet of impeller,internal flow and external characteristics were analyzed at different flow rates and different gap.The main research contents and achievements are as follows :(1)The performance test system of the disc pump was built.Through the pressure sensor,torque meter and data acquisition card,the disc pump’s inlet and outlet pressure,flow rate and shaft power and other related parameters were collected,and the disc pump performance curve was calculated using theoretical formulas.Through analysis,it is found that when the flow rate is greater than 78 m3/h,the test head value begins to drop abruptly,which is caused by cavitation in the impeller of the disc pump.(2)In the numerical calculation,the influence of the number of grids on the calculation accuracy of the disc pump is studied.The results show that when the number of grids is 4.16 million,it can meet the calculation requirements.Aiming at the special s tructure of the disc pump impeller,in order to solve the problem of dynamic and static calculation between different fluid domains in the disc pump impeller,the scheme A without bolt in the impeller,the scheme B without rotating the bolt in the impeller and the scheme C with rotating the bolt in the impeller are proposed.By comparing the numerical results of the three schemes with the experimental results,it is found that the minimum error of scheme A is 4%.The maximum error of scheme C is 16%,Therefore,scheme a is chosen as the numerical simulation scheme.The influence of different turbulence models on the internal flow field and external characteristics of the disc pump is discussed.Through quantitative and qualitative analysis,it is found that both SST k-ωand SST k-ωturbulence models are suitable for the numerical calculation of the disc pump.Therefore,SST k-ωturbulence model is selected as the numerical calculation scheme in this paper.(3)The influence of clearance flow on the internal flow field and external characteristics of the disc pump is studied.It is revealed that the energy loss caused by the clearance flow between the ring and the pump cavity is the main reason for the difference of the internal flow field and external characteristics between the full channel model and the non full channel model of the disc pump.The interaction between the leakage flow and the main flow in front of the impeller inlet is analyzed,and the influence of the clearance flow on the vortex evolution in the impeller is expounded.Finally,it is found that the clearance flow reduces the pressure distribution at the volute and outlet of the impeller,and has a certain influence on the strength of the pressure pulsation in the local volute.(4)Carry out numerical calculations in disc pumps different flow conditions,study the main flow characteristics and gap flow in the pump,and evaluate the impact of ring leakage flow on the main flow.It is found that there is a low pressure area in the leafless area near the suction surface,and the range of this area gradually increases with the increase of the flow rate.Affected by the uneven pressure distribution,the fluid flows to the low pressure area.By studying the clearance flow,the pressure and pressure pulsation in the front chamber are revealed.It is found that the pressure and pressure pulsation in the pump chamber decrease with the increase of flow rate.The distribution of turbulent kinetic energy and pressure in the ring is obtained,and it is found that the energy loss caused by the flow in the orifice ring is small under large flow conditions.Different flow rates,the leakage flow interacts with the main flow in front of the impeller inlet,and the generated vortex gradually decreases as the flow rate increases.The effect of the leakage flow in the ring on the velocity distribution in the extension section of the inlet is further compared and analyzed,and it is found that the leakage flow can restrain the backflow of the fluid at the impeller inlet and the generation of eddies to a certain extent.(5)The influence of the ring width on the internal flow field and external characteristics of the disc pump is studied,and it is found that the increase of the ring has little effect on the external characteristics of the disc pump.The reason for the difference of the radial velocity of the fluid in the impeller due to the different pressure on the volute under different clearance of the orifice ring is analyzed.It is found that the backflow area of the flow passage near the tongue region of the impeller decreases with the increase of the clearance of the orifice ring.The distribution of the total pressure in the gaps of different rings was studied,and it was found that the total pressure drop between the inlet and outlet of the rings was less affected by the width of the ring gaps.Finally,the influence of the size of the gap on the vortex in front of the impeller inlet is discussed.It is found that with the increase of the gap,the size of the vortex in front of the impeller inlet and its influence o n the main flow gradually increase.