Experimental and modeling study on liquid phase ammonia spray characteristics under high-pressure injection and engine-like ambient conditions

Abstract

Ammonia, a renewable fuel with low-carbon emissions, is a promising alternative fuel for internal combustion engines. This study investigates the evaporation of liquid-ammonia spray using optical experiments and numerical simulation. Based on the experimental results, the computational model was established and validated, in addition to the optimization of the empirical formulas for spray tip penetration and spray angle. The results show that the model can accurately predict the development of liquid-ammonia spray under high-temperature and high-pressure environment conditions. The prediction error of the model for the spray tip penetration does not exceed 8 %. And the liquid phase ammonia spray is not sensitive to the changes in injection pressure with high temperature atmosphere. The temperature distribution along the spray's central axis exhibits three stages: constant, logarithmic growth, and linear growth, affecting vapor-phase mass fraction due to entrainment intensity. The logarithmic growth region serves as an ideal ignition zone for ammonia diffusion combustion. Additionally, increasing ambient temperature reduces the first stage distance and enhances the second stage's change rate. Even with a consistent temperature span (200K), the vapor-phase ratio and average turbulent dissipation show non-linear changes. These insights are crucial for enhancing liquid-ammonia spray mixture quality and controlling its combustion characteristics.