Effect of CO2 in-cylinder injection on combustion and emission characteristics of diesel quasi-HCCI

Effect of CO2 in-cylinder injection on combustion and emission characteristics of diesel Quasi-Homogeneous Charge Compression Ignition (HCCI) combustion was studied by using a gas injection system. The Quasi-HCCI combustion mode was realized by two-pulse diesel injection. Experimental results reveal that, NOx emission can be effectively reduced by adjusting CO2 injection timing and quantity. With advance of CO2 injection timing, combustion phase delays and NOx decreases. As CO2 cyclic injection quantity increases with the same injection timing (-150CA ATDC), peak mean gas temperature decreases, combustion phase is postponed while maximum pressure rise rate and indicated thermal efficiency remain nearly the same; due to prolonged ignition delay, peak heat release rate is slightly increased than that of baseline case; NOx reduces, HC and CO increases while smoke remains nearly unchanged.