Large eddy simulation investigation of ammonia spray characteristics under flash and non-flash boiling conditions

Ammonia is an ideal zero-carbon fuel for energy systems, and it can be used directly in a liquid state. However, liquid ammonia is susceptible to flash boiling due to its unique physical and chemical properties, which brings challenges for liquid ammonia spray and combustion simulations. In the present study, high-pressure liquid ammonia injection under flash boiling and non-flash boiling conditions was investigated. Large eddy simulations were conducted in an Eulerian–Lagrangian framework. The aim is to explore in detail the influence of the critical parameters on the characteristics of liquid ammonia spray. Under the flash boiling condition, the effects of ambient pressure were examined. Comparisons of the measured and predicted spray penetration and morphology demonstrate that the present simulations can reproduce liquid ammonia spray characteristics well. Varying ambient pressures causes the ammonia spray to be at different superheat levels, resulting in significant changes in spray features. Under the non-flash boiling condition, the effects of injection pressure and ambient pressure were investigated. The higher injection pressure feature a higher gas velocity and improves the mixing of ammonia and air. The ammonia spray propagates more rapidly and the spray width becomes wider at lower ambient pressure.