Study on marine engine combustion and emissions characteristics under multi-parameter coupling of ammonia-diesel stratified injection mode

Abstract

In this study, the ammonia-diesel stratified injection (ADSI) is explored on a marine low-speed engine., The effect of three injection timings(ITS = −3°CA ATDC, −1°CA ATDC, and 1°CA ATDC) coupling with three diesel energy fractions (DEFS = 1%,5%, and 10%) on combustion and emission characteristics of the engine under full load is investigated. The results show that advancing IT has an obvious effect on increasing peak cylinder pressure while enhancing DEF can increase the heat release rate under ADSI mode, and the ignition delay time is less than original diesel engine. The ADSI has higher indicated thermal efficiency than original diesel engine except for IT of 1°CA ATDC coupling DEF of 1%, and its combustion efficiency can be significantly improved. Furthermore, the NOx increases with advancing IT and increasing DEF while the unburned ammonia is the opposite. The NOx emissions are all lower than original diesel engine under different IT coupling DEF. Advancing IT is an effective measure to reduce unburned ammonia. The greenhouse gas (GHG) can be greatly reduced. A priority strategy of the IT coupling DEF is proposed through comprehensive comparison under the ADSI mode, which can meet the Tier III regulations. This strategy reduces indicated specific fuel consumption and GHG around by 4% and 94% compared with the diesel engine respectively, and the combustion efficiency reaches more than 99%. The unburned ammonia is limited to less than 150 ppm.