Structure Design And Experimental Research On Low Pressure Atomizing Nozzle

This research was supported by National Key Research and Development Program of Green and High Efficiency Water-saving Irrigation.(No.2016YFC0400202).With the increasing cost of energy and the growing demand to saving water for optimum crop production,atomization technology needs higher standards to achieve the goal of saving energy and water.The main objective of the study was to develop atomize nozzles,such as high atomizing pressure and small atomizing range.Hyd nozzle was selected as the nozzle of atomizing liquid prototype,and an external structure was designed to improve the liquid atomization effect under low pressure(0-0.15 MPa)by centrifugal force.Through theoretical analysis and experimental study,the atomization performance of prototype nozzle and low pressure atomization nozzle were studied.The conical angle nozzle driven by a small external motor was used to provide centrifugal force for the liquid atomization.The atomization performance of Hyd nozzles with aperture of 0.3,0.5,0.8 and 1.0 mm was tested under four different pressure conditions: 0.05,0.08,0.11 and 0.14 MPa.The results show that with an increase of pressure,the flow rate of nozzles with 0.8 and 1.0mm apertures increased significantly at the same pressure compared with 0.3and 0.5mm nozzles.When the pressure changes,the nozzles with different apertures gave large intensity of fog field and the intensity of fog field decreased with an increase of distance from the center of the nozzle.The image of Hyd nozzle was obtained by PIV test system,and the image analysis of atomization angle,velocity field and liquid breakage of Hyd nozzle was carried out by image processing software.When the pressure of 0.3mm nozzles is 0.14 MPa,the linear jet will not form.The linear jet was formed in the axial direction of the nozzle,when the pressures were 0.11 and 0.14 MPa.When the pressure of 0.5mm nozzles is 0.14 MPa,the jet dispersion does not form a linear jet.With the decrease of pressure,a linear jet was formed when the pressure was 0.11 MPa,and dispersed into a large number of small droplets.A conical liquid film jet with annular cross-section is formed when 0.8 mm nozzle has pressure of 0.11 MPa and 1.0 mm nozzle has pressure of 0.08 MPa.As the pressure decreases,the axial velocity,radial velocity and combined velocity reached the maximum point.When the pressure was increased,the gradient of velocity changed.The axial velocity in the center of the atomization region was larger than that on the left and right sides.The combined velocity was mainly affected by the axial velocity and the radial velocity.The design of structure parameters of low pressure atomizing nozzle based on the radial water distribution of single nozzle,the uniformity calculation model was used to calculate and analyze the atomizing water uniformity of low pressure atomizing nozzle.The results show that the radial water distribution shape of each test was similar,and the maximum water atomization point occurred at the end of the atomization range.The water atomization amount on both sides of the maximum water point decreases,and the basic shape presents normal distribution.The maximum atomization range of low pressure atomization nozzle was 1.95 m and as the combination distance increased,the coefficient of uniformity decreased.The comparison of triangle and square combination showed that square combination gave the highest coefficient of uniformity.The factors affecting atomization range were aperture,angle between cone,displacement,pressure and spacing.Similarly,triangle and square combination coefficient of uniformity were affected by aperture,spacing,pressure angle between cone and displacement.