A Method Of Image And Its Application In Spray Droplet Size Measurement

During the air-mist spray process,the droplet characteristics have a significant influence on the cooling effect.When the droplet size is small and the number is large,the water atomization effect will be better.The droplet can not only improve the heat transfer efficiency,but also facilitate the uniform temperature of the ingot.Studying the particle size and distribution of droplets in the air-mist flow field is of great significance for the study of the air-mist flow field.In order to realize the detection of the droplet size of the air-mist flow field,this research presents a method to identify the droplet size of the air-mist spray jet by improving the optical imaging method.The average particle size and particle size distribution of the air-mist spray jet under different working conditions were measured by this method.Conduct the following research :(1)Built the air-mist jet generation platform and the optical imaging system and obtain a picture that satisfies the processing requirements by using the method of oblique photography.(2)A digital image processing system including geometric correction,binarization and smoothing de-noising was developed based on MATLAB and we validate the accuracy of the Geometric Correction.(3)Using the above method,the experimental measurement of the droplet size under different working conditions of the air-mist droplets jet was carried out.(4)It was validated the accuracy of this method by using monodisperse droplet generator with particle sizes of 50 and 100 microns and we define error analysis.(5)The experiment used hollow glass beads and bubbles in water in order to explore the applicability of this method in different detection objects.The conclusions are drawn as follows:(1)By detecting the flow field of the air-mist droplets jet,the image of particles with clear,moderate concentration and less overlap canbe obtained by high-speed camera.The particles can be restored to the undistorted state through geometric correction,and the particle size can be identified.The main distribution range of the particle diameter is below 100 microns.The number of droplets is the highest near the center axis just below the nozzle.At the edge of the flow field,the number of particles is small,and the particle size was even.(2)It is proved that the error of this method for particle size measurement is less than 2%.(3)For particles with a density close to the medium but different refractive indices such as bubbles in the water,this method can effectively measure the particle size.