| Submersible sewage pumps are widely used in urban sewage treatment,agricultural irrigation and industrial water supply and drainage industries,and are suitable for special media containing particles,fibers and other impurities.In the actual operation process,due to the existence of solid phase,the hydraulic performance and reliability of submersible sewage pumps when transporting two-phase media are reduced.It is very important to improve the performance of submersible sewage pump by studying the difference of single-phase clean water and solid-liquid two-phase flow mechanism.In this paper,WQ2520-6126-400 submersible sewage pump is taken as the research object.Based on theoretical analysis,numerical simulation and experimental method,the internal flow characteristics of submerged water pumps carrying different media are studied.The research contents and conclusions are as follows.Firstly,the geometric parameters of the main flow passage components of the submersible sewage pump are obtained through the preliminary hydraulic design.Then,the two-dimensional design drawing is drawn by CAXA,and the three-dimensional modeling,mesh generation and independence verification are carried out.Finally,the numerical simulation is carried out.Based on the specific area theory,the original scheme(specific area is 1.123)is improved and designed to obtain three schemes,the specific areas are 1.313,1.253 and 1.206 respectively.Through the study of pressure and velocity nephogram under different working conditions,it is found that the hydraulic performance of submersible sewage pump with specific area of 1.253 is better than other schemes,the efficiency is increased by 3.92%and the head is increased by4.53%;the blade work capacity is enhanced,the radial force is reduced by 155.7n and the axial force is reduced by 144.9n,and the operation reliability is improved.Secondly,the unsteady calculation of 0.6Q_d,0.8Q_d,1.0Q_d,1.2Q_d and 1.4Q_d under five different working conditions is carried out by comparing the model with the original model,and the pressure cloud diagram and pressure fluctuation diagram are drawn for comparative analysis.The results show that:under the off design condition,the pressure distribution of the impeller is relatively disordered,which indicates that the flow in the pump is complex and the loss is large,which is not conducive to the operation of the pump;the pressure pulsation of the improved scheme is generally lower than that of the original scheme,and the pressure pulsation under different conditions at the same monitoring point is greatly affected by the flow rate,and the low-frequency pulsation is the main pulsation frequency.Finally,a solid liquid two phase flow with different particle size and volume ratio was calculated using the DPM model in flowing water.The solid phase is spherical particles,and the force of flow field is analyzed.The numerical simulation process is closer to the actual flow state.Compared with the single-phase clean water condition,the hydraulic performance of the submersible sewage pump is slightly improved when the particles with smaller size and smaller volume fraction are transported in the pump;When the particle size ds=0.05mm,the head increases by 3.64%and the efficiency increases by 0.74%.When the volume fraction Cv=0.5%,the head increases by 2.45%and the efficiency increases by 0.77%.With the increase of particle size and volume fraction,the performance of the submersible sewage pump decreases.The particle concentration on the blade surface showed a negative correlation with the particle size and showed a positive correlation with the particle volume fraction.;the low pressure range of submersible sewage pump expands with the increase of particle size and volume fraction;the velocity of two-phase fluid in the pump is negatively correlated with the inertia force of solid particles.The pressure fluctuation of solid-liquid two-phase has the same trend as that of single-phase clean water,but the peak value is larger than that of single-phase clean water,and the pressure fluctuation curve is more uneven with the increase of particle size and volume fraction,which provides a theoretical basis for the vibration and noise reduction and performance improvement of submersible sewage pump when working in two-phase medium.In this paper,the hydraulic design,three-dimensional modeling,mesh generation,numerical simulation and external characteristics of submersible sewage pump are studied,and the hydraulic performance of submerged water pump under working conditions different from different specific regions was studied;the influence of single-phase clean water medium and solid-liquid two-phase medium on the hydraulic performance and reliability of submersible sewage pump is analyzed.The results show that the comprehensive hydraulic performance of the submersible sewage pump with1.0Q_d and 1.253 specific area is the best;the existence of solid medium reduces the comprehensive hydraulic performance of the submersible sewage pump,and the particle size is smaller than that of the single-phase clean water condition.When ds=0.5mm and Cv=5%,the efficiency and head of the pump decrease by 4.166%and11.398%,respectively.According to the research results of this paper,it is expected to provide a theoretical basis for the follow-up study of irregular particle solid-liquid two-phase flow in submersible sewage pump. |
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