Effects of ammonia on combustion, emissions, and performance of the ammonia/diesel dual-fuel compression ignition engine

Ammonia is currently receiving more interest as a carbon-free alternative fuel for internal combustion engines (ICE). A promising energy carrier, easy to store and transport, being liquid, and non-carbon-based emissions which make ammonia a green fuel to decarbonize ICE and to reduce greenhouse gas (GHG) emissions. This paper aims to illustrate the impacts of replacing diesel fuel with ammonia in an ammonia/diesel dual fuel engine. Hence, the effects of various ammonia diesel ratios on emissions and engine performance were experimentally investigated. In addition, a developed 1D model is used to analyze the combustion characteristics of ammonia and diesel. Results show 84.2% of input energy can be provided by ammonia meanwhile indicated thermal efficiency (ITE) is increased by increasing the diesel substitution. Moreover, increasing the ammonia energy share (AES) changed the combustion mode from diffusion combustion in pure diesel operation to premixed combustion in dual fuel mode. Therefore, combustion duration and combustion phasing decreased by 6.8CAD and 32CAD, respectively. Although ammonia significantly reduced CO₂, CO, and particulate matter (PM) emissions, it also increased NO_X emissions and unburned ammonia (14800 ppm). Furthermore, diesel must be replaced with more than 35.9% ammonia to decrease GHG emissions, since ammonia combustion produces N₂O (90 ppm) that offsets the reduction of CO₂.