Research On Impinging Low-speed Centrifugal Atomization Mechanism And Atomizer Parameter Optimization

Controlled droplet application(CDA)technology is one of fast developing low-volume spray technologies in developed countries at present.Centrifugal atomization technology is a world-acknowledged advanced droplet controlled technology,which has the advantages of good uniformity of droplet and narrow droplet spectrum.The technology can control the droplet size by the change of rotation rate of centrifugal atomizer to meet the requirements of different spray targets and weather conditions to droplets,the application can not only achieve the purpose of effective prevention and control of agricultural pests,but also effectively reduce the environment pollution due to the chemical spraying.This paper studied the impinging low-speed centrifugal atomization mechanism and atomizer parameter optimization,explored the main influencing factors and effect of the droplet size,and optimized the structure of the centrifugal atomizer in order to provide a new pesticide application technology and equipment with advanced technical level,safety and high reliability for facility agriculture in China,which adapt to the requirements of crop pest prevention and control in greenhouse.Based on the method of theoretical analysis and experimental study,this paper tracked the formation of droplets and the spatial dispersion of droplets after leaving the atomizer by high-speed photographic analysis system,and the centrifugal atomization mechanism is proved.Based on laser particle size analyzer,this paper studied variation of droplet diameter under the interaction of different structural parameters and working parameters of the atomizer and established mathematical model of droplet size distribution.Based on the theory of “Biological Optimum Diameter Size”,this paper obtained the optimum combination of structural parameters and working parameters.The main research contents and results are as follows:(1)By impinging low-speed centrifugal atomizer atomization mechanism of theoretical research,explored the liquid atomization method and centrifugal atomization droplets broken form,analyzed the factors affecting droplets size of centrifugal atomization.(2)Through the design of dynamic system,liquid supply system,air-assisted system,control system and other components,centrifugal atomization test platform was built and the precise control of centrifugal atomizer working parameters was achieved,so as to provide a test platform for further research on the influence of different structural parameters and working parameters on the droplet spectrum.(3)Studied on the atomization mechanism of the atomizer by the high-speed photographic analysis system,and explored the process and quality of the second atomization caused by the impinging between the droplets produced by centrifugal atomization turnplate and the atomizing teeth.Test results show that when the rotation rate was 600 rpm,the liquid fill atomization turnplate surface,have liquid without full atomization by atomization turnplate.When the rotation rate was 900 rpm,1200 rpm,the atomization quality is still unsatisfactory,existing a large number of large size droplets.When rotation rate was 1500 rpm,the droplets were evenly sprayed;As the rotation rate(4)further increased,quantity of the even mist droplets increased.(5)Carried out experimental study on the influence of droplet spectrum by the centrifugal atomizer with structural parameters and working parameters.Single factor analysis was performed to analyze the main factors which include the structural parameters of the atomizer(tooth shape,tooth number,tooth distribution)and working parameters(rotation rate)that affect the droplet spectrum.So as to explore the effect of various factors on droplet spectrum and determine the significant impact of various factors on droplet spectrum.(6)Based on quadratic regression orthogonal experiment,the secondary response regression was analyzed by Design-Expert8.5 software,set up the quadratic regression model of the droplet volume median diameter and droplet spectrum span.Obtained the optimized design fit formula.And obtained the best combination of the centrifugal atomizer structure parameters and the rotation rate of atomization turnplate based on the theory of "BODS".(7)Measured the droplet spectrum under three kinds of optimal combination of atomizer structure parameters and working parameters by the laser particle size analysis.Compared the droplet spectrum actual measured values with prediction values from the atomization model,the relative error of the droplet volume median diameter and droplet spectrum span are 8.0% and 8.1%,2% and 9%,1.6% and 7% respectively.The actual measured value coincide with the model prediction value basically,so as to verify the accuracy of the model.