Experimental Study On Velocity Field Of Nozzle Atomization Using PIV

Nozzles are widely used in industrial fields,agricultural production and daily life.The experimental study on the atomization process of nozzle is helpful to quantitatively analyze the spatial distribution of the characteristic parameters of the spray flow field.It provides theoretical guarantee for optimizing the structure of the gas-liquid two-phase flow field.In this paper,we study various parameters of spray flow field with visual nozzle atomization experimental platform.The PIV particle image velocimetry is used to measure the nozzle atomization flow field under different spray pressures and different orifice diameters.The influence of nozzle structure parameters and spray parameters on the spray flow field is analyzed.Taking into account the characteristics of PIV experimental data,we use time-average method and space-average method to deal with the spray velocity field.Taking the spray flow field of 0.3mm orifice nozzle under the pressure of 0.50 MPa as an example,the instantaneous velocity field of the flow is treated by the time-average method.And then we use the spaceaverage method to spatial average the flow field axially and radially,examining the distribution of speed field.Based on the distribution of velocity along the radial direction,a new method is proposed to determine the nozzle atomization angle.The boundaries and atomization angles of the mainstream in every flow fields are calculated.In this paper,the influences of the different nozzle aperture on characteristics of spray flow field are studied.Through the analysis of the spray velocity field of 3 different aperture nozzles with same model,following conclusions are obtained: Under the determined spray pressure,increasing of the nozzle aperture has a significant effect on the increase of spatial average velocity in mainstream area of the flow field.As the nozzle aperture increases from0.3mm to 0.7mm,the mainstream area of flow field will increase,leading to an increase in atomization angle of 53.8%.In addition,five pressure conditions were set to study the influence of spray pressure changes on the characteristics of the spray flow field.By analyzing the flow field under different pressure,we get a conclusion: The closer to the nozzle in axial direction,it is more obvious the change of the spray pressure to the average space velocity.At the same time,the increase of spray pressure can significantly enlarge themainstream area of the flow field of small-aperture nozzle.As spray pressure increases from0.40 MPa to 0.45 MPa,the atomization angle increases by 24.4%.For large-aperture nozzles,the effect of increasing the spray pressure on the mainstream area of the flow field is relatively weak,and the influence on the atomization angle is also weak.