Design And Experiment Of Laval Supersonic Atomizing Nozzle

With the continuous development of agricultural technology in the world,the application of agricultural engineering technology in China is more and more extensive.At present,in the field of agricultural engineering,ultrasonic atomizing nozzles are mainly fluid type and piezoelectric transducer type.Compared with piezoelectric transducer nozzle,the structure of the hydrodynamic nozzle is simpler,the use conditions are more extensive,the droplets are smaller,and the atomization amount is much larger than that of the piezoelectric transducer nozzle.One of the most important types of hydrodynamic nozzles is supersonic atomizer.Therefore,on the basis of previous research on supersonic atomization,this paper designs a supersonic atomization nozzle.Firstly,the structure of Laval tube is designed based on the empirical formula.Then,the important parameters are selected and simulated by CAE software.The results show that the biggest influence factor is the size of the contraction angle of Laval tube,and the second is the size of the expansion angle.Then,the influence of throat diameter on Laval tube is studied,and the simulation results show that too small throat diameter is not conducive to the supersonic atomization of Laval tube.Then the other structures are simulated.First of all,the influence of different diameter of inlet pipe on atomization.By adjusting different inlet pressure and different inlet speed,observe the gas-liquid distribution,velocity nephogram and pressure nephogram in Laval pipe,and draw a conclusion: different inlet pipe diameter will affect the speed,pressure and gas-liquid distribution in Laval pipe.Then the influence of the thickness of the water film on the atomization is considered.Through the simulation of different thickness of water film,the gas-liquid distribution diagram,pressure and velocity nephogram are obtained,and then the above influencing factors are integrated to carry out the virtual orthogonal experiment design,and the biggest influencing factor for atomization is throat diameter.Design two kinds of different nozzle outlet ways,and carry on the simulation analysis to it,draw the conclusion: the outlet setting in the cavity tail is more in line with our expected design.Through further simulation analysis,it is found that when the outlet is set at the tail andthe outlet diameter is 4.5mm,the air flow velocity is the largest.After simulation,two kinds of nozzles were manufactured and tested.The test content is the size of atomized particles under different pressures.The results show that with the increase of pressure,the uniformity of droplet size of the two kinds of nozzles is getting better.The minimum particle size of the two kinds of nozzles is 25.18 ? m,but the uniformity of the nozzle with the outlet set at the tail is better.In order to better apply the sprinkler to the field of agricultural engineering,pipeline spray test was carried out.Through the comparison of humidifier atomization unit,pressure type atomizer and fluid type supersonic atomizer,it is concluded that the performance of supersonic atomizer is better.Finally,the orthogonal test of the pipeline spray is carried out on the sprinkler head set at the tail of the outlet to study which factor will have the greatest impact on the pipeline spray when the sprinkler remains unchanged.The experimental conclusion is that the factors that affect the maximum amount of fog sprays are pipe diameter and pipe length,and the diameter of the nozzle will also affect the spray volume,and the minimum distance is the distance between the holes.After indoor tests,in order to make the nozzle designed by us achieve lower cost and higher cost performance in production,material optimization,reliability analysis and structural topology optimization are carried out on the nozzle.Through material optimization,polyethylene was finally selected as the injection molding material among four different injection molding materials.In the structural topology optimization,the Laval tube valve core module and outlet module of the nozzle are optimized by Ansys software,unnecessary materials are reduced,and the nozzle volume is reduced.