Potential of ammonia energy fraction and diesel pilot-injection strategy on improving combustion and emission performance in an ammonia-diesel dual fuel engine

Abstract

Ammonia (NH3) acting as a hydrogen carrier and carbon-free fuel has gotten more attention to reduce the carbon emissions from transportation. Ammonia-diesel dual-fuel combustion mode is one of the potential ways to achieve lower carbon emissions in compression ignition engines. However, NH3 and nitrous oxide (N2O) emissions were problems to reduce greenhouse gas emissions in this combustion mode. In this study, a diesel pilot-injection strategy where the pilot-injection energy ratio (PER) varied from 0 to 100% was used in an attempt to improve combustion and emission performance. In addition, ammonia energy ratios (AER) of 40%, 50%, 60%, and 70% were applied to this strategy to verify the feasibility of the pilot injection of diesel. Results showed the pilot-injection strategy could reduce NH3 emission from about 8000 ppm to 1000 ppm, and the reduction effect became more significant as the PER increased, while N2O emission also decreased at higher PER. Furthermore, the pilot-injection strategy could keep a high indicated thermal efficiency of about 45%. The engine achieved stable combustion at the wide AER region with low carbon dioxide (CO2) emission. However, higher nitrogen oxides (NOx), carbon monoxide (CO), and hydrocarbon emissions were disadvantages in the pilot-injection strategy.