Based on a medium speed marine diesel engine

an experimental study was carried out to investigate the influence of two stage injection on the engine performance and combustion characteristics. The test results show that

for a large marine diesel engine

the partially premixed compress ignition(PPCI) can be realized by two stage injection at part load. And the key factors affecting PPCI are pilot injection timing

pilot injection quantity and two stage injection pressure. By an experimental study on two stage injection conducted on the single cylinder engine of the medium speed marine diesel engine

a refined strategy of two stage injection for the PPCI combustion of the large marine engine was determined. When the break mean effective pressure(BMEP) is required to be 0.3MPa

the injection pressure of the two stage injection should be 105MPa

the pilot injection timing 20 degrees in crank angle before top dead center

and the pilot injection quantity 20% of the total. When BMEP is required to be 0.6MPa

the injection pressure of the two stage injection should be 120MPa

the pilot injection timing 35 degrees in crank angle before top dead center

and the pilot injection quantity 28% of the total. The profit from the PPCI combustion is that the break specific fuel consumption can be reduced by 3.1%～6.2%

the soot emissions can be reduced by 51%～62%

and the rate of pressure raise can be reduced by 58%～70%.