Experimental study of co-combustion ratio on fuel consumption and emissions of NG-diesel dual-fuel heavy-duty engine equipped with a common rail injection system

Natural gas-diesel dual-fuel mode has been considered as one of the most promising approaches to apply natural gas in diesel engines with minor engine modification and keeping high thermal efficiency levels. In this paper, the co-combustion characteristics of an NG-diesel dual-fuel engine were studied in order to utilize LNG on electronically controlled common rail diesel engines. The brake specific fuel consumption and exhaust emissions under varied co-combustion ratios are compared and analyzed under speeds of 1200 r/min and 2200 r/min with loads of 25%, 30%, 35%, 40%, 60% and 100%. Experimental results show that, with the increase of co-combustion ratios in dual-fuel mode, the brake specific fuel consumption increases under low loads while decreases under high and full loads; HC emission increases significantly; CO emission increases; NOx emission hardly changes; while smoke emissions decrease greatly.