Experimental Study on Ammonia-Methanol Combustion and Emission Characteristics in a Spark Ignition Engine

Ammonia and methanol are both future fuels with carbon-neutral potential. Ammonia has a high octane number, a slow flame speed, and a narrow ignition limit, while methanol has a fast flame speed with complementary combustion characteristics but is more likely to lead to pre-ignition and knock. In this paper, the combustion and emission characteristics of ammonia-methanol solution in a high compression ratio spark ignition engine are investigated. The experimental results show that the peak in-cylinder pressure and peak heat release rate of the engine when using ammonia-methanol solution are lower and the combustion phase is retarded compared with using methanol at the same spark timing conditions. Using ammonia-methanol solution in the engine resulted in a more ideal combustion phase than that of gasoline, leading to an increase in indicated thermal efficiency of more than 0.6% and a wider range of efficient operating conditions. The use of ammonia-methanol solution increases unburned NH₃ emissions and THC emissions, resulting in lower thermal efficiency compared with the use of methanol. Using ammonia-methanol solution reduces CO₂ emissions and increases NO_x and N₂O emissions, eventually resulting in similar greenhouse gases (GHG) emissions to the use of methanol, both of which are 10% lower than the use of gasoline.