Research on the coupling mechanism of heat and mass transfer in the impact spray of multiple-jet HAN-based liquid propellant

This study investigates the coupled mechanisms of liquid-film fragmentation, droplet generation, evaporation, diffusion, thermal reactions, and energy release in the spray combustion of hydroxylammonium nitrate (HAN)-based liquid propellants in a small-thrust liquid rocket engine. A multi-coupling aerosol combustion framework combining the volume-of-fluid method with the discrete droplet trajectory method is developed to clarify the transition from impinging atomization to spray combustion. The evolution of the liquid column, film, ligaments, and droplets after jet impingement is resolved, focusing on interface instability, film rupture, droplet formation, size distribution, and gas–liquid interfacial area growth. Results show that atomization proceeds through liquid-film formation, interface destabilization, hole expansion, ligament stretching, and droplet breakup. These processes continuously renew and enlarge the gas–liquid interface, reduce the characteristic liquid-phase scale, and promote droplet heating, evaporation, and species diffusion. The resulting droplet size distribution further governs the spatial non-uniformity of interphase heat and mass transfer. Droplet transport, evaporation, and breakup are further coupled with gas-phase species transport and energy release to reveal the synergistic effects of evaporation, diffusion, interphase transfer, and thermal chemical reactions. The results establish the intrinsic relationship between aerosol quality and the thermal–mass transfer response of the combustion field and identify the dominant mechanism governing the transition from impinging atomization to spray combustion. The findings provide a theoretical basis for injector optimization, combustion enhancement, thermal management, and improved propulsion performance in HAN-based small-thrust liquid rocket engines.