In view of the necessity to develop high thermal efficiency and zero-carbon engine for marine applications,this study proposes an ammonia/diesel stratified injection A-D-A(ammonia-diesel-ammonia)mode and investigates its combustion process through numerical simulations.The research findings demonstrate that the A-D-A mode is an effective approach to enhance indicated thermal efficiency(ITE),with a minimum allowable energy fraction of around 3％for the pilot diesel injection.By appropriately matching the energy fraction of the pre-injection ammonia injection and the injection interval between the pre-injection and main injection,the ITE can be maintained at a higher level while minimizing the emissions of NOx,NH3,and greenhouse gases(GHG)as much as possible.With a 30％energy fraction for the pre-injection ammonia,coupled with a-4℃A ATDC injection timing for the diesel injection and a 5℃A injection interval between the pre-injection and main injection,high ITE can be achieved while significantly reducing NH3 and N2O emissions.However,the NOx emissions are higher compared to the original diesel engine configuration.
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