3D-CFD Simulation of Diesel and Dual Fuel Engine Combustion

A 3D-CFD model with a reduced detailed chemical kinetics of the combustion of diesel and methane fuels is developed while considering turbulence during combustion to simulate the mixture flow, formation and combustion processes within diesel and diesel/methane dual fuel engines having swirl chambers. The combustion characteristics of the pilot injection into a small pre-chamber are also investigated and compared with those within a swirl chamber. Modeling results were validated by a group of corresponding experimental data. The spatial and temporal distributions of the mixture temperature, pressure and velocity under conditions with and without liquid fuel injection and combustion are compared in the swirl and main combustion chambers. The effects of engine speed, injection timing, and the addition of carbon dioxide on the combustion process of dual fuel engines are investigated. It is found that in the absence of any fuel injection and combustion, the swirl center is initially formed at the bottom left of the swirl chamber, and then moved up with continued compression in the top-right direction toward the highest point. The swirling motion within the swirl and main combustion chambers promotes the evaporation of the liquid pilot and the combustion processes of diesel and dual fuel engines. It was observed that an earlier autoignition can be obtained through injecting the pilot fuel into the small prechamber compared to the corresponding swirl chamber operation. It is to be shown that reduced engine emissions and improved thermal efficiency can be achieved by two-stage HCCI combustion.