The three dimensional computational fluid dynamics(CFD) model for a diesel/natural gas dual fuel marine two stroke pre chamber engine was established by using a new generation of thermal fluid analysis software(CONVERGE)

and the effect of compression ratio

pilot diesel mass

injection pressure and injection angle on combustion process was studied to improve the thermal efficiency of the engine. Results show that increasing compression ratio can enhance maximum burst pressure in the cylinder

thus effectively improving thermal efficiency. However

due to the limitation of the mechanical strength of the engine

a better effect can be obtained when the compression ratio is 12.5. Properly increasing the amount of pilot diesel and the injection pressure can increase the ignition point of jet flame and promote the enhancement of ignition energy

which is beneficial to improve thermal efficiency. Adjusting the injection angle of pilot diesel to inject it into the CH4-rich area can achieve a better pilot effect and therefore reduce fuel consumption. In short

increasing the compression ratio

combined with delayed pilot injection has a more obvious effect on improving thermal efficiency.