The dynamics of the liquid-gas interface in two-fluid coaxial atomization in a high-pressure environment*

We study the dynamics of the liquid-gas interface in the near field of a two-fluid atomizer. Specifically, we analyze how the ambient pressure influences the liquid destabilization and break-up process, as well as the early stages of spray formation and dispersion. The gas density increase associated with high environmental pressure, in the range of 1 - 5 atmospheres, changes the dynamics by which the high momentum coaxial gas jet destabilizes the liquid inner jet. We present new experimental results for a coaxial liquid-air atomizer operating in a high-pressure environment, with gas-to-liquid momentum ratio in the range of M = 5 - 50, and swirl ratio of SR = 0 - 1, in agreement with previously published results for atomization under atmospheric pressure conditions. High-speed shadowgraphy images are used to quantify the spatially and temporally varying liquid-gas interface field. Liquid core length, spreading angle, and other spray metrics are presented, and the influence of gas density/pressure identified from the comparison with atomization at atmospheric conditions. Results show a reduction of the spreading angle with the increase in gas density/pressure at injection.