| Y-type screen filter was widely used in agricultural micro-irrigation system,and its good filtration performance was the premise to ensure the normal operation of micro-irrigation system.The long-term and high-speed development of modern agriculture was inseparable from the improvement of screen filter performance.Therefore,this paper explored a structure optimization scheme to improve the overall performance of the filter.At present,the structure optimization of the screen filter mainly has two directions: the filter element and the filter structure.The optimization of the filter element is difficult to compare the numerical simulation with the experimental results and the experimental model is difficult to make.In contrast,the shell structure optimization has the advantages of strong maneuverability and convenient experiment,so this paper gives priority to the structural design of the mesh filter shell.In order to improve the hydraulic performance and anti-clogging performance of Y-type screen filter,four typical structural parameters of Y-type screen filter are selected and set up at three levels,namely,the angle between outlet and cylinder(35°,45°,55°),inlet reduction ratio(18/26,20/26,22/26),guide vane height(10mm,15 mm,20mm)and guide vane center angle(30°,60°,90°).The orthogonal test scheme is set up,and the sensitivity of various factors to head loss,area proportion of medium-speed flow area,relative standard deviation of particle distribution and interception rate are explored by the combination of CFD-DEM coupling and physical test.The dominant factors and the optimal combination scheme are found out by the comprehensive analysis method,and verified by experiments,which provides an objective basis for further optimization of the structure of the net filter.It is found that:(1)The head loss of the original model of the screen filter under different flow rates is simulated by the software FLUENT,and the formula is fitted according to the flow-pressure drop curve.The reliability of the simulation results is verified by experiments,and it is proved that the simulation results are accurate,so the numerical simulation method can be used to analyze the filter performance and optimize the structural parameters.(2)The head loss of the screen filter is mainly composed of three parts: the head loss of the inlet and outlet section,the bend head loss of the filter and the head loss of the filter(osmotic pressure drop and flow pressure drop).The orthogonal test schemes all follow the law of flowpressure drop curve,and the head loss of the filter increases not only with the increase of inlet velocity,but also with the increase of angle.According to the net surface flow cloud map,the maximum flow area is at the middle end of the exit side of the filter surface,and the minimum velocity region is at the upper and lower ends of the entrance side.For the area proportion of medium speed flow area,the primary and secondary order of influencing factors are included angle,center angle of guide vane,height of guide vane and inlet reduction ratio.The angle has the greatest influence on the area proportion of the medium speed flow area,and the angle is negatively related to the area proportion of the medium speed flow area.(3)The passing point of small particles in the filter is mainly concentrated in the cylindrical area where the upper and lower ends of the filter surface and the entrance side and the exit side meet.According to the four factors,the relative standard deviation of the distribution of index particles from large to small is the entrance reduction ratio,the included angle,the center angle of the guide vane and the height of the guide vane,respectively.The entrance reduction ratio is the dominant factor and is positively correlated with the uniformity of particle distribution.The significant order of the influence of the four factors on the interception rate of the index is the entrance reduction ratio,the center angle of the guide vane,the height of the guide vane and the included angle.With the increase of the secondary factor,the center angle of the guide vane,the interception rate first decreases and then increases.If the interception rate is increased by changing the center angle,it is set in the range of 0°～ 30°and above 90°.In terms of anticlogging performance,the effect of entrance reduction ratio is the most significant.According to the cloud map of network flow and passing point distribution,it is found that the area with low particle pass rate corresponds to the region with high and low speed flow,and the area with concentrated particle flow corresponds to the area with medium speed flow.With the increase of entrance reduction ratio,the uniformity of particle distribution is better,and the interception rate increases positively.(4)This subject adopts multi-objectives,and the optimal combination of factors is obtained by comprehensive scoring method combined with hydraulic performance and plugging performance analysis: angle 35°,inlet reduction ratio 22/26,guide vane height 10 mm,guide vane center angle 90°.Among them,the included angle has the most significant influence on the comprehensive index,so the included angle is a key parameter in the performance optimization design of the screen filter.After optimization,the head loss and relative standard deviation decreased by 36.6% and 43.26% respectively,and the area proportion of interception rate and medium speed flow area increased by 3.93% and 15.77%,respectively,indicating the feasibility and practical application value of the optimization scheme. |
