Experimental Investigation On Mode And Characteristics Of Electrostatic Atomization For Double Capillaries

Electrostatic atomization is a kind of atomization method which can break liquid into small droplets by applying an external high voltage electrostatic field.It can improve the intensity of atomization by reducing surface tension of liquid and increasing additional pressure difference between internal and external surfaces.In recent years,it has been gradually applied in micro-scale liquid fuel combustion,industrial spraying,film material preparation and other fields.So far,the research on electrostatic atomization of single capillary has been relatively comprehensive,but the research of electrostatic atomization of double capillaries is few.The atomization mode and characteristics of electrostatic atomization for double capillaries will be studied by visual experimental method.The work is as follows:(1)The experiment system of double capillaries electrostatic atomization was designed and built independently.Errors caused by experimental bench and equipment were tested and adjusted.Deionized water and anhydrous ethanol were selected as the experimental media.(2)The high speed camera was used to shoot the double capillaries outlet,and the media contrast experiment was done.According to the changes of morphology,The atomization modes of deionized water and anhydrous ethanol were divided.The atomization modes of anhydrous ethanol can be divided into drop,spindle,pulsating jet,stable cone jet,multi-jet and other atomization modes.The change of droplet separation frequency under different media and flow rate was studied.It was found that the separation frequency increased slowly in the droplet or oblique droplet mode,the spindle mode began to show a sudden jump,and when the stable cone jet mode reached the maximum separation frequency,it began to decrease gradually after losing the stable state.(3)Through the flow comparison experiment,the division diagram of the modes of double capillaries electrostatic spray of the change with voltage under different flows is given.Experiments show that with the increase of the flow rate,both the Initial voltage value and the voltage span value of stable cone jet mode gradually increase except the type of0.5ml/min flow rate.At the same time,this experiment uses the dimensionless electrostatic Bond number and the dimensionless flow to analyze the relative relationship between the voltage and the flow in the atomization.(4)PDIA technology was used to test atomized droplet size under different voltage,flow rate and height.The results show that the distribution of atomized particle size of double capillaries was approximately M-type,and the more stable the atomized state was,the smaller the fluctuation of atomized particle size would be.Compared with single-capillary electrostatic atomization,the particle size decreased by nearly 35%and the atomization range increased by nearly 40%.(5)PIV technology was used to test the axial velocity and radial velocity of atomized droplets at different voltages,flow rates and heights.The results show that the radial velocity distribution of the liquid drops was linear under various conditions,and the more stable the atomization state was,the stronger the linear relationship was.The distance between the liquid drops and capillary outlet has almost no effect on the radial velocity.The regularities of distribution of axial velocity is similar to the particle size.(6)MATLAB was used to calculate the potential distribution of the electric field.When the angle between the capillary and vertical direction is constant,the potential decreases as the distance increases.When the distance is constant,the potential decreases as the included angle increases.In the experiment,the maximum resultant potential appears at the exit directly below the capillary with an angle of about 4?10~4 V.(7)Based on the calculation of the field strength of the electric field in the experiment,the composite field strength at different heights showed a symmetrical distribution relationship that high center and low around.In the electric field,the radial field strength is distributed in a symmetrical V-shape.As the distance gets closer to the central position,the radial field strength gradually decays,and the attenuation speed decreases with the increase of the height.The distribution law of the axial field intensity is similar to that of the combined field intensity.The attenuation of the axial field intensity in the axial direction is 2 to 3 times that in the radial field intensity.