Effect of Ammonia Addition on Combustion and Emission Characteristics of Diesel Engine Under Various Operating Conditions

Ammonia is a carbon-free alternative fuel and a hydrogen carrier. Ammonia diesel dual fuel (ADDF) combustion mode is one of the promising ways to reduce carbon emissions in CI engines. However, present researches are mainly based on combustion and emissions for naturally aspirated diesel engine under specific operating condition. This paper aims to illustrate the impacts of replacing diesel with ammonia in a turbocharged diesel engine under various operating conditions. Hence, the effects of various ammonia substitution rate (ASR) on combustion and emission characteristics are numerically investigate by using GT-Power software for nine groups of different operating conditions with low, medium and high speeds and loads. Results show maximum 70% of input energy can be provided by ammonia for nine groups of different operating conditions, and the brake mean effective pressure (BMEP) and the indicated thermal efficiency (ITE) increases with the increase of ASR. Secondly, increasing ASR decreases the peak cylinder pressure (PCP) under different operating conditions, but increases the maximum pressure rise rate (MPRR) at certain operating conditions. Among them, under medium-speed and high-load conditions, the MPRR reaches the highest value, about 0.587 MPa/(°CA), but does not exceed 0.6 MPa/(°CA). Thirdly, increasing ASR changes the combustion mode from diffusion combustion in pure diesel operation to premixed combustion in dual fuel mode. Finally, adding ammonia reduces the NOx, CO and HC emissions, and the decrease is 15.2%–43.2%, 76.2%–82.3%, 70%–79.6%, respectively.