numerical study of the effects of ammonia injection timing on the emissions of an ammonia-hydrogen dual fuel engine

The global emphasis on decarbonization of the energy sector, specifically in the transport segment, has drawn the researchers attention to utilizing alternative fuels with renewable sources. recent studies have shown that ammonia has the potential to substitute fossil fuels and is an outstanding rival for hydrogen. although ammonia has many advantages compared to hydrogen, it suffers from poor autoignition characteristics and needs additional provisions to promote its stable combustion. studies have shown that the simultaneous use of hydrogen with ammonia in internal combustion engines can partially remedy the drawback of autoignition in compression ignition engines. in this study, the effects of ammonia injection timing on the combustion characteristics and emissions of an engine fueled with ammonia and hydrogen are numerically investigated. a turbocharged diesel engine with a compression ratio of 16.5 is considered. in order to promote ammonia combustion, the intake air temperature and pressure were increased in a rational range, and hydrogen was introduced to the intake charge. the governing equations of engine combustion were numerically solved by utilizing a well-established combustion mechanism. the results showed that advancing the ammonia injection can favorably decrease the ignition delay time. however, the nox formation increases. delaying the ammonia injection (less than 355 crank angle degrees) can reduce the peak pressure, temperature, and nox formation. decreasing the ammonia injection duration decreased the ignition delay and increased the peak pressure, temperature, and nox emissions. unlike diesel engines, the split injection strategy did not affect the peak pressure in the dual-fueled ammonia-hydrogen engine due to the existence of hydrogen. the nox emissions were also higher with this injection strategy.