Experiment Study And Numerical Simulation On Typical Torpedo Screen Filter

Torpedo screen filter is a kind of sand removing novel equipment(the shape of its core component is similar to that of weapon torpedo).It mainly consists of torpedo component,filter shell,screen and automatic flushing controller.On the base of physical model experiment,numerical simulation,field test and theoretical analysis,this paper carry out study on the characteristics of the torpedo screen filter,and then illuminate the influences of the different flow rates and outlet positions to the head loss and filtering time of the filter under circumstances of clean and muddy water,therefore,put forward its key technical parameters of operation;Illustrate the flow field of clean water after inserting the torpedo inside the filter,meanwhile,discuss the influences of different outlet positions,flow rates and screen meshes to the characteristics of the filter.DPM Multiphase flow model was applied to analyze the distribution and motion of particles inside the filter.The results would supply with technical guarantee and theoretical support for the further application of the torpedo screen filter.(1)The head loss of torpedo screen filter increases with increase of flow rate while the water source is clean water,the head loss of 80 mesh torpedo screen filter is larger than that of 120 mesh,this is because the torpedo creating high velocity along the screen,thus the mesh diameter and inner surface roughness of the screen play key roles in influence to the head loss of torpedo screen filter.(2)Under circumstances of sediment content of inlet flow rate is constant,When the flow rate is in the range of 240 m3/h~360 m3/h,the test results show that the head loss increase with increase of flow rate while the outlet is at the position of 0.52 m and 0.72 m respectively.The variation rule of head loss with the filtering time presents as following three stages: ○1 developing with the same value of initial head loss,○2 gradually reducing,○3gradually increasing and rapid increase.When the flow rate is in the range of 240 m3/h~300 m3/h,filtering time is prolonged with the increase of flow rate;however,filtering time reduces with the increase of flow rate in the range of 300 m3/h~360 m3/h.80 and 120 mesh filters have the longest filtering time while the flow rate is Q=300m3/h.when the filter outlet is set at the position of 0.92 m,the head loss also increases with the increasing of flow rate,and the filtering time shortens with the increase of flow rate.According to the testing results,0.52 m is the best outlet for the 80 and 120 mesh torpedo screen filter.(3)When the outlet is at the position of 0.52 m,the experiment is carried out on the variation rule of the head loss and filtering time with the different sediment contents for 80 mesh and 120 mesh filter respectively,by using constant flow rate 300m3/h and different sediment content(80mesh: 0.1214g/L 、 0.1420g/L 、 0.18003g/L 、 0.2755g/L 、 0.3581g/L and0.3935g/L;120mesh: 0.0874g/L 、 0.1211g/L 、 0.1311g/L 、 0.1512g/L 、 0.1658g/L and 0.1934g/L).The testing results show that the filtering time of both of filters reduces with the increase of sediment content,and the occurring time of head loss curve inflexion also shortens with the increase of sediment content.The inflexion of head loss curve will occur while the head loss reaches to the 4.0m,and that the head loss increasing gradient of 80 mesh larger than that of 120 mesh,meanwhile,the filtering time of 80 mesh is also larger than that of120 mesh.(4)According to the theoretical calculation and physical model test results,the optimum drainage differential pressure is 0.04 Mp,and the optimum drainage time is 40s~50s for both of the 80 mesh and 120 mesh torpedo screen filters.(5)According to the numerical simulation analysis,the torpedo component and the boundary conditions of the inlet and outlet notably affect the distribution rule of flow field of the filter,especially for the torpedo component;thus the flow characteristic of water inside of the filter is changed a certain extent.The present work points out that the flow velocity distributions inside and outside of the filter screen along the X-axes are divided into three stages: ○1 a rapid increase,○2 a rapid decrease,and ○3 a gradual decrease.The pressure difference of inside and outside of screen near to the inlet is larger than that of other place;however,the pressure differences along the X-axis grow increasingly smaller,and the maximum and minimum pressure differences between the two are about 23 kPa and 0.5 kPa respectively.(6)DPM Multiphase flow model was applied to analyze the distribution and motion of particles inside of the filter,the numerical simulation results indicate that sewage flows into the torpedo from the small hole of 20 mm in diameter at the end of torpedo,and flows out from the small hole of 10 mm in diameter at the head of torpedo,thus,there is a water flow circulation between inside and outside of the torpedo.Most of the sand particles precipitate inside the torpedo,as result,it prolongs the filtering time.(7)When the water resources of irrigation is surface water,the organic content is more than 10mg/L,and the particle size is larger than 10μm,the torpedo screen filter much more develop its filtering efficiency while it is combined use with sand filter.(8)When the water resource of irrigation is groundwater,the sand separate efficiency of the hydrocyclone reaches to 92% ~98%,the torpedo screen filter is combined use with hydrocyclone,the filtering time of the torpedo screen filter is much more prolonged.(9)Under circumstances of surface water and sewage from city and industry are water resources of micro irrigation,and the organic content is less than 10mg/L,especially,there is sediment pond and other filtering facility in front of the micro irrigation system,the single use of torpedo screen filter completely satisfy with the water quality demand of micro irrigation.This paper makes a systematic and further research on torpedo screen filter.The results would provide theoretical basis for optimizing structure parameters and choosing the optimum operation parameters in the process of practical application and future further research.