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

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. (C) 2021 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Automated summary

Ammonia has the potential to be a solution for decarbonising transport due to its ability to act as a hydrogen carrier. Increasing the aspiration of ammonium hydroxide solution was found to prolong ignition delay, raise peak in-cylinder temperature, decrease combustion quality, and reduce particle size.