| The shortage of water resources requires atomization technology to achieve the goals of energy and water conservation.The atomization nozzle currently has key problems such as the need for high-power equipment to pressurize,the small atomization range,and the uneven distribution of droplets.Therefore,it is of great significance to design an atomizing nozzle that can save water resources,reduce costs,and have a high degree of dispersion of droplet size.In this paper,a combination of theoretical analysis and experimental research is used to optimize a new type of atomizing nozzle suitable for the pressure range of 0.15-0.30 MPa.In order to improve the atomization effect of the atomization nozzle in the medium and low pressure range,a atomization characteristic test platform was built.It reveals the flow characteristics of the external flow field of the atomizing nozzle and the law of droplet breaking.The atomization nozzle performance under different working pressures and different structural parameters was systematically studied.Optimizing the nozzle based on orthogonal experiment to get the best parameters.The main research contents and results were as follows:(1)In view of the current research status and atomization mechanism of atomizing nozzles,related research and optimization methods are summarized,and a structural design of atomizing nozzles is proposed.The distribution of atomization performance of nozzles with a diameter of0.3-0.9 mm under four different pressure conditions of 0.15 MPa,0.20 MPa,0.25 MPa and 0.30 MPa were studied.Based on the Gray Correlation Analysis,it is concluded that the droplet size of nozzles with outlet diameters of 0.7 mm and 0.9 mm,nozzle cavity outlet ratio of 2,and outlet contraction angle of 60° have the strongest correlation with working fluid pressure.(2)A test device for the atomization characteristics of medium and low pressure atomization nozzles was built.The nozzle range,atomization cone angle,velocity field,droplet size and liquid breakage are analyzed.The influence of different working fluid pressure conditions and different structure sizes on nozzle atomization characteristics is studied.The results indicate that: Choosing an appropriate number of samples for time averaging can greatly reduce the random volatility of PIV to the atomized flow field test data.Choose a plane 300 mm away from the nozzle outlet as the stable section of the nozzle.On the stable section,the SMD is smaller than the X=400 mm section,and the droplet breakage is more complete.Vm reaches the maximum value near the nozzle outlet,and the maximum Vm shows a linear increase with the pressure.The number of droplets flux N increases with the increase of the pressure of the working fluid.Under the pressure of 0.15 MPa and 0.20 MPa,the atomization angle is greatly affected by the nozzle outlet diameter,the number of large-diameter droplets decreases faster,And the number of small-diameter droplets decreases at a greater rate between 0.25 MPa and 0.30 MPa.The droplet size distribution of the nozzle is the most uniform at a pressure of 0.25 MPa.When the working fluid pressure is 0.30 MPa,the increase of nozzle outlet diameter weakens the positive promotion effect of changing the range of the mainstream area.The axial velocity of the droplet does not fluctuate significantly with the change of the outlet contraction angle.The atomization angle and SMD increase with the increase of the outlet contraction angle.For a nozzle with a 0.9 mm aperture,a larger operating range can be achieved when the length diameter ratio is 1.For nozzles with small apertures,it is necessary to select a suitable length diameter ratio to make the atomized droplets more evenly and effectively distributed in the target area.(3)Orthogonal table was established by orthogonal experiment method,and three factors of nozzle outlet diameter,spray cavity length diameter ratio and outlet contraction angle were selected,and each factor was reasonably divided into four levels to carry out orthogonal optimization experiment.Take the nozzle droplet size,range,atomization angle and the relative size range of the droplet size as the test indicators,and use extreme variance analysis to analyze the test data.The results indicate that: The primary and secondary order of influence on the nozzle droplet size is the spray cavity length hole ratio,the outlet contraction angle,and the nozzle outlet diameter.The primary and secondary order of the influence on the nozzle range is the spray cavity length hole ratio,the nozzle outlet diameter,and the outlet contraction angle.The primary and secondary order of the influence on the nozzle atomization cone angle is the nozzle outlet diameter,the nozzle cavity length hole ratio,and the outlet contraction angle.The primary and secondary order of influence on the relative size range of the nozzle droplet size is the spray cavity long hole ratio,the outlet contraction angle,and the nozzle outlet diameter.The long hole ratio of the nozzle cavity and the outlet shrinkage angle have a highly significant influence on the nozzle droplet size.The nozzle outlet diameter has a significant influence on the nozzle droplet size.The nozzle outlet diameter and the spray cavity long hole ratio have a highly significant influence on the nozzle range.The three factors have little effect on the nozzle atomization cone angle.The long hole ratio of the spray cavity has a significant influence on the relative size range of the nozzle droplets.The optimal structure combination of the nozzle is that the nozzle outlet diameter is 0.9 mm,the spray cavity long hole ratio is 2,and the outlet contraction angle is 75°. |
PDF Full Text Request