Experimental investigation on atomization properties of impaction-pin nozzle using imaging method analysis

•An optical imaging system is built to measure nozzle atomization properties.•Effects of pressure and orifice diameter on droplet size and velocity were obtained.•Empirical correlation models for droplet size and atomization efficiency were built.•Atomization efficiency declines with the rise of pressure drop and orifice diameter. The impaction-pin spray nozzle is widely used in chemical and process industries. To study the atomization characteristics of the impaction-pin nozzle, a high-pressure atomization apparatus was developed and an optical imaging system for the measurement of droplet parameters was proposed. The droplet size and velocity vector were extracted from the shadowgraph images and the influence of liquid pressure drop especially nozzle orifice diameter on atomization was analyzed in detail. Finally, prediction models for Sauter mean diameter were proposed and the atomization efficiency was analyzed. The results indicate that the range of droplet Sauter mean diameter is 8.55–37.5 μm while arithmetic mean velocity is 0.483–1.921 m/s at the pressure drop range of 0.525–4.95 MPa for PJ6. For PJ8, the range of diameter is 20.6–53.9 μm while velocity is 0.746–2.879 m/s at the pressure drop range of 0.43–3.32 MPa. The size and velocity of atomized droplets both follow the law of logarithmic normal distribution. The droplet diameter is negatively and the velocity is positively related to the pressure drop, while both of the diameter and velocity are positively related to the nozzle orifice diameter. The atomization efficiency declines with the rise of pressure drop and orifice diameter. Besides, empirical correlation models related to gas Weber number and liquid Reynolds number for droplet size and the atomization efficiency were also built accurately. The research provides guides for studies on atomization properties of spray nozzles and their applications.