Experimental study on the performance of a high compression ratio SI engine using alcohol/ammonia fuel

Ammonia, ethanol, and methanol are promising carbon-neutral fuels in the future. Therefore, the use of alcohol fuels to enhance ammonia combustion in engines deserves further study. The performance of a spark ignition engine with high compression ratio at various loads was experimentally investigated to determine the impact of fuel composition. Specifically, ethanol and methanol were chosen as the primary fuels, while gasoline was assigned as the control group. Gaseous ammonia was introduced through the intake port. The results show that ammonia increases indicated thermal efficiency (ITE) in different ways when blended with different fuels, with the gasoline group obtaining higher ITE (2.8 % relative increase) by optimizing combustion phase, and the ethanol and methanol groups directly enhancing ITE (1.2 % and 0.8 % relative increase) with the same combustion phase due to reduced heat transfer loss. Methanol group shows a more ideal combustion duration under low loads and large ammonia blending ratios and achieves higher ITE due to higher oxygen content. Replacing gasoline with ethanol and methanol significantly reduces greenhouse gas (GHG) under similar NOx emissions, and the advantage of blending carbon-containing fuels with ammonia to reduce GHG is more significant under high loads and large ammonia blending ratios.