Numerical Simulation And Experimental Study On Internal Flow Of Semi-Open Submersible Cutting Pump

The semi-open submersible cutting pump studied in this paper is mainly used for sewage discharge in cities.Because of its good cutting performance and strong passing capacity,it occupies a place in urban production and life.At present,sewage pumps on the market are mostly suitable for large flow and high lift,and focus on the anti-clogging and passing ability of the pump itself.Based on centrifugal pumps,this paper studies the semi-open submersible cutting pump with small flow and medium and high lift.It adopts the cutting device of impeller and rotating blade coaxial,rotating blade and fixed knife,upper and lower plate with self-cutting edge,and adopts semi-open impeller.Not only has strong cutting ability,but also has excellent anti-clogging ability.Based on theoretical analysis,on the one hand,the internal flow characteristics and pressure fluctuation characteristics of the pump were analyzed,and verified by experiments.On the other hand,the flow characteristics of two-phase flow in the pump were explored,and the wear was analyzed and predicted.The main contents of this paper are as follows:(1)Three-dimensional modeling software UG9.0 was used to model the flow passage components,and ICEM CFD was used to divide the computational domain into structured grids,and the correlation of grids was analyzed.On the premise of ensuring the computational accuracy,a set of grids with less computational time and cost were screened out.Finally,CFX14.5 was used to simulate the whole flow field of the semi-open submersible cutting pump,and the simulation results were compared with the experimental results.The results of external characteristics showed that the simulation was in good agreement with the experimental results,and had high reliability and accuracy.(2)For the selection of the relative angle between the rotating blade and the impeller and the number of blades,which have great influence on the performance of the semi-open submersible cutting pump,three or four schemes were designed,and the optimal scheme was selected by comparing and analyzing the external characteristics(head and efficiency),the internal flow field(pressure distribution,velocity distribution and vorticity distribution)and the force(axial force and radial force).For the thickness of rotating blade with smaller pump performance,the external characteristics were directly compared.(3)Based on the steady calculation results,the rotating blade,lower plate,impeller,volute and upper plate of the semi-open submersible cutting pump were selected as the research objects.Under different working conditions(different flow conditions,different solid density conditions,different solid particle diameter conditions and different solid volume fraction conditions),the external characteristics,pressure distribution,velocity distribution,solid phase distribution and particle trajectory were studied.The internal flow field and solid-liquid two-phase flow characteristics of the pump were investigated,and the wear of the flow passage parts of the semi-open submersible cutting pump was predicted.The results showed that the properties of particles have a significant impact on the performance of the pump,and the wear area mainly concentrated in the head and tail of the blade.(4)Monitoring points were selected at the inlet of rotating blade,the clearance between rotating blade and fixed knife,the groove of lower plate,the groove of upper plate,the different section of volute,the tongue,the outlet of impeller and the flow passage of impeller.The unsteady numerical simulation of semi-open submersible cutting pump was carried out,and the method of time-domain diagram and frequency-domain diagram was used for overall analysis,and the dynamic-static interference comparison was emphatically analyzed.For serious lower plate,upper plate,rotating blade and fixed knife gap,the first section,tongue separation.At the same time,the radial and axial forces of impeller were analyzed by using intuitive time-domain diagram,polar coordinate diagram and vector diagram.The results showed that the pressure fluctuation decreases from near the rotating parts to far away,and the lower plate is affected by both impeller and rotating blade,and the wave amplitude is the largest.The axial and radial forces vary periodically.