Experimental Study On The Rotary Atomization Nozzle Based On The Shear Effect

The pneumatic atomization nozzle servesas an effective toolfor liquidatomization.Compared with traditional nozzles,the pneumatic atomization nozzleis simple in structure,operates with low pressure,consumes less energy and yields favorable atomization effect.Therefore,this kind of nozzle has been widely used in applications such asdesulfurization,material preparation,food processing,agricultural spraying and space disinfection.Based on previous studies,the present dissertation proposed a pneumatic atomization nozzle that was based on the shear effect.A fan was used to pressurize gas through multiple air holes into the mixing chamber,where gas and liquid were mixed together.The liquid was inhaled into the mixing chamber due to pressure difference.The geometric parameters of the nozzle that appreciably influencedthe atomization quality were investigated.Through a preliminary experiment,it was indicated that the number of air holes,air-hole diameter,air-hole shape,and the gas flow rate hadremarkable effects on the diameter and velocity of the atomized droplets.Among them,the effects of the air-hole diameter and gas flow rate were more significant.Therefore,three nozzles with air-hole diameters of 8.0 mm,9.0 mm,and 10.0 mm were designed.Pure water was used as the liquid medium.A laser particle size analyzer and a laser Doppler velocimetrywere used separately to measure the diameter and velocity of the atomized droplets.The relationship between droplet diameter and droplet velocity was analyzed.Major conclusions drawn from the study are as follows:(1)At the same gas flow rate,the nozzle with an air-hole diameter of 10.0 mm has the highest atomizeddroplet velocity and the smallest droplet diameter.As the gas flow rate increases,the velocity of the atomized droplets increases and the diameter decreases.As the streamwise distance from the nozzle increases,the diameter of the atomized droplets decreases first and then increases,and the droplet velocity increases first and then decreases.In general,the smallest droplet diameter corresponds to the highest droplet velocity.(2)The size distribution of the atomized droplets exhibits a single-peak pattern.The probability density function increases first and then decreases.The cumulative droplet volume distribution displays a similar tendency,with a sharp rise first and then a gradual elevation.As the gas flow rate increases,the peak value of the probability density function increases,and the number of small atomized droplets increases;the cumulative droplet volume distribution curve shifts slightly towardssmall droplet sizes,and the volume fraction occupied by small atomized droplets increases.(3)At different streamwise distances from the nozzle,radial velocity distributionscorresponding to different air-holediameters are different.For the nozzlewith an air-hole diameter of 10.0 mm,the cross-sectional axial droplet velocity distributionsdo not vary with the gas flow rate.(4)At the same gas flow rate,the cone angle of the spray associated with the air-hole diameter of 9.0 mm is the largest,and the liquid flow rate is the highest.As the gas flow rate increases,the cone angle is reduced and the liquid flow rate is increased.