| Nozzle is the core component of the system of plant protection machinery,its performance directly affects the reliability and efficiency of the plant protection machinery.In this paper,a new type of mechanical spray nozzle is designed based on electrostatic atomization and effervescent atomization.The experimental investigation of the electrostatic effervescent nozzle mainly includes three aspects: the change rule of critical condition of nozzle;the variation of nozzle flow;the influence of static electricity on the deposition density on the back of the target of the nozzle.In view of the phenomenon of the backflow of air and liquid working fluid,the experimental study on the pressure of the mixing chamber is carried out by using the comprehensive experimental platform of the spray performance of the nozzle.The influence of the working parameters on the pressure of the mixing chamber and the structural parameters on the critical pressure ratio are analyzed.The experimental results show that the higher the hydraulic pressure and air pressure,the greater the pressure in the mixing chamber;The pressure in the mixing chamber is more affected by the change of air pressure.The critical pressure ratio is related to the structure of the spray nozzle.When the area ratio between the total area of the vent and the exit area of the nozzle is relatively small,the critical pressure ratio increases with the increase of the area ratio.When the exit diameter is 1.0mm,when the area ratio is greater than 3.23,the critical pressure ratio varies within the range of 0.85 to 0.92.The smaller the outlet diameter,the greater the critical pressure ratio.The influence of ventilation mode on the critical pressure ratio is not significant.The critical pressure ratio increases with increasing swirl core.The convergence angle of the mixing chamber has little effect on the critical pressure ratio.In order to ensure the safe and reliable operation of the experimental nozzle,the minimum inlet hydraulic pressure should be higher than the product of the inlet gas pressure to the critical pressure ratio.The effects of pressure drop,pressure ratio and air-liquid ratio on the discharge characteristics were investigated.The experimental results show that the liquid flow coefficient is between 0.05 and 0.3.Fitting the experimental data,the empirical formula of the liquid flow coefficient to the gas-liquid ratio and the ratio of the air-liquid ratio to the ratio of liquid to gas pressure is obtained.When the experimental nozzle structure is fixed,the hydraulic pressure drop is inversely proportional to the air-liquid ratio,and also the ratio of liquid to gas pressure and the air-liquid ratio,the air-liquid ratio and the liquid flow coefficient.Liquid discharge coefficient is proportional to the ratio of liquid to gas pressure.At the same time,the smaller the number of air holes and the smaller the diameter,the less the flow.Increasing swirl core reduces gas flow,but has little effect on liquid flow.The convergence angle has little influence on the gas flow and liquid flow,but the stability of spray field is improved when the nozzle is in high air-liquid ratio.Experimental investigations on the deposition show that static electricity and air-liquid ratio has great influence on the deposition density of the nozzle on the back of the target.When the air-liquid ratio is higher,the density of the back surface of the target is reduced gradually with the increase of the air-liquid ratio.When the air-liquid ratio increases to a certain extent,the effect of static electricity on the deposition density of the effervescent nozzle is not significant.Under the same air-liquid ratio,the higher the charge voltage in a specified range,the higher the deposition density.When the charging voltage is increased to-3000 v,continue to increase the charging voltage,static electricity impact on the target back deposition density is very small.When the air-liquid ratio is reduced to 0.032,the deposition coverage of the target back reaches the maximum. |
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