Effects of Temperature and Pressure on the Flash Boiling Spray Characteristics of Ammonia

Abstract:

Ammonia is used as a green hydrogen storage fuel with great potential for application， with zero carbon emissions compared to traditional hydrocarbon fuels. Liquid ammonia has a low boiling point of only 239.7 K at 1 atm， which makes it highly susceptible to flash boiling. In this paper， numerical simulations of liquid ammonia fuel were carried out in the Eulerian-Lagrangian framework to investigate the morphology， penetration distance， particle size and ammonia vapor mass fraction of the flash-boiling sprays at different superheat degrees， injection pressures， fuel temperatures and ambient temperatures. The results show that the spray penetration increases with the larger superheat of liquid ammonia， and the collapse of the spray front becomes more pronounced. The higher the spray pressure， the liquid ammonia collapses are enhanced and then weakened， and the particle size is smaller. The spray characteristics of liquid ammonia are almost independent of the ambient temperature， and are less affected by superheat degree at low fuel temperatures， and the opposite is true at high fuel temperatures. The ammonia vapor mass fraction increases with increasing fuel temperature.

Key words:liquid ammonia;spray characteristics;flash boiling;superheat degree