Effects Of Sediment Characteristics On Clogging Of Drip Irrigation Emitters

In this paper,we study the tooth labyrinth path as the research object and use the method of short cycle blockage test,analyzing the effect on douche block about the flushing pressure,the flushing time and the flushing interval time;and determine grading changes of douche before and after discharge by using the Mastersizer 2000 laser particle size instrument,then to confirm the sensitive particle size which is easy to block up the douche.At the same time,an Eulerian-Lagrange liquid-solid multiphase turbulence model combined with the kinetic theory of granular flow was used to simulate based on coupled CFD-DEM the water-sand two-phase flow in drip irrigation emitter with labyrinth channel.The main conclusions of this paper are as follows:(1)The flushing pressure and the flushing time had significant influence on the average flow rate of douche,and the effect of the flushing time is greater than that of the flushing pressure.The average flow rate of douche is not increased with the increase of the flushing pressure;the flushing pressure of 0.225 MPa is the most easily to cause the dropper blocking,the flushing pressure of 0.150 MPa is the second,but flushing effect is the best when the flushing pressure is 0.300MPa;The optimal parameter combination of anti-clogging performance about douche is 0.3 MPa of the flushing pressure,5min of the flushing time,3days of the flushing interval time.The result of the Mastersizer 2000 laser particle size instrument,the mean value of D(0.9)was used as the range of the sand particles which is easy to cause the dropper blocking;The results of this experiment showed that the range of the sand particles which is easy to cause the dropper blocking is 33.089~104.713 ?m.(2)Little grains of sand and small density of sand is smaller amplitude at the tooth tip,the movement of them is basically in the mainstream area,fast speed and small change frequency,short distance,less time;they mainly affected by the drag force,and total force less,having good following performance.With the increase of sand diameter and density of sand,amplitude at the tooth tip increases,the speed become slow,but change frequency increases,distance becomes longer and time increase;then they out of the mainstream and get into the vortex area;In addition,the inertia force is more and more obvious,the total force is increased,and the following is poor.The smaller the diameter of sand and the density of sand,the time to reach the micro dynamic equilibrium are shorter;the number in labyrinth path is lesser.(3)There are more sands around center of channel depth than area by sidewall.With decrease of channel depth,volume concentration of sands in channel increases multiply.The less channel depth is,the less water flow speed in “Z” direction to be,but the more sands speed in “Z”direction to be,the more times sands through central plane and impact sidewall.The increasing of impact frequency on sidewall change original movement direction of sands in high frequency,augment collision on sidewall and between sands.This kind of movement of sands decrease kinetic energy,go against passing through labyrinth channel and increase probability of blocking.The method of simulating based on coupled CFD-DEM is applied to analyze movement of sand individuality and group in a great quantity,analyze distribution of sands group,acquires sands movement in labyrinth channel from micro-view and has become an efficient technique in structure design of labyrinth channel.