With the adoption of the IMO Greenhouse Gas Emission Reduction Strategy Revision,
the international shipping industry is facing huge pressure to reduce greenhouse
gas emissions, and the conversion of ship power from traditional fossil fuels to
low-carbon and zero-carbon fuels is the fundamental solution, and ammonia fuel,
as a zero-carbon fuel, is an important direction for the development of ship
power in the future. Based on a marine low-speed diesel engine with a bore of
520 mm, computational fluid dynamics (CFD) numerical simulation was carried out
to study the effects of different diesel energy fractions, ammonia injection
pressure, ammonia injection timing and ammonia diesel injection interval on the
combustion and emission characteristics of the engine under the dual-fuel
combustion mode of high-pressure dual direct injection. The calculation results
show that under the condition of the current engine, 5% of diesel energy can
reduce carbon emissions by 92.8% under the premise of successful ignition.
Increasing the injection pressure of ammonia fuel results in more effective
work, greater turbulent kinetic energy, better mixing effect of ammonia fuel and
diesel flame, and reduces unburned ammonia and greenhouse gas emissions, but
there is a trade-off between high NOx or high N2O emissions. Diesel
ammonia 2CA injection in advance can take into account various emission data
well, and is the most suitable injection interval.