Ultra-high-speed filming of atomizing jets

In the atomization regime, a liquid jet breaks up into droplets of diameter much smaller than the nozzle exit diameter, within the nozzle or immediately upon entering the chamber gas. The mechanism of atomization is currently unknown. The initial emergence and breakup details of liquid jets at the onset of injection were recorded, apparently for the first time, by an ultra-high-speed framing camera (up to 106 frames/sec). Liquid pressure and viscosity, gas pressure and density, and the nozzle internal geometry were varied. The nozzle exit diameter, the liquid surface tension and density, and the gas and liquid temperatures were not varied significantly. Intact length, spray angle, penetration rate, and quasi-steadiness of the breaking jet are discussed. It is concluded that within the tested range, liquid cavitation or aerodynamic surface wave growth, augmented by liquid cavitation and/or boundary layer velocity profile relaxation phenomena, could explain the observed experimental trends adequately.