Integrated numerical prediction of atomization process of liquid hydrogen jet Original Research Article

The 3-D structure of the liquid atomization behavior of an image jet flow through a pinhole nozzle is numerically investigated and visualized by a new type of integrated simulation technique. The present computational fluid dynamics (CFD) analysis focuses on the thermodynamic effect on the consecutive breakup of a cryogenic liquid column, the formation of a liquid film, and the generation of droplets in the outlet section of the pinhole nozzle. Utilizing the governing equations for a high-speed turbulent cryogenic jet flow through a pinhole nozzle based on the thermal nonequilibrium LES-VOF model in conjunction with the CSF model, an integrated parallel computation is performed to clarify the detailed atomization process of a high-speed image jet flow through a pinhole nozzle and to acquire data, which is difficult to confirm by experiment, such as atomization length, liquid core shape, droplet-size distribution, spray angle, droplet velocity profiles, and thermal field surrounding the atomizing jet flow. According to the present computation, the cryogenic atomization rate and the image droplets–gas two-phase flow characteristics are found to be controlled by the turbulence perturbation upstream of the pinhole nozzle, hydrodynamic instabilities at the gas–liquid interface and shear stress between the liquid core and the periphery of the image jet. Furthermore, calculation of the effect of cryogenic atomization on the jet thermal field shows that such atomization extensively enhances the thermal diffusion surrounding the image jet flow.