An experimental and modelling study of dual fuel aqueous ammonia and diesel combustion in a single cylinder compression ignition engine

Abstract The ability of ammonia to act as a hydrogen carrier, without the drawbacks of hydrogen gas-storage costs and low stability-renders it a potential solution to the decarbonisation of transport. This study combines both modelling and experimental techniques to determine the effect of varying the degree of aspiration of ammonium hydroxide (NH4OH) solution, at different engine loads, in the combustion of a compression ignition engine. Ignition delay was extended as ammonia injection increased, causing an increase in peak in-cylinder temperature, but generally lower combustion quality-increasing incomplete combustion products, while decreasing particle size. The higher peak in-cylinder temperatures generally correlated with higher nitrous oxide (NOx) emissions in the exhaust, though a fuel-bound nitrogen effect was apparent. Chemical kinetic modelling at equivalent conditions found increasing levels of unburnt ammonia with greater aspiration. Moreover, the ignitability of NH4OH was found to improve in simulations substituting diesel with hydrogen peroxide direct injection.