Experimental study on the combustion characteristics and emissions of biodiesel fueled compression ignition engines with premixed dimethoxymethane

In the present study, the combustion characteristics and emissions of biodiesel fueled direct injection engines with premixed dimethoxymethane (DMM) by port injection were investigated on a single-cylinder diesel engine. The experimental results show that, for a fixed equivalence ratio of biodiesel, the ignition timing and the center point of heat release advance, while the end point of heat release delays with the introduction of premixed DMM. For a constant equivalence ratio of premixed DMM, the ignition timing delays and the end point of heat release advances with the decrease of biodiesel quantity. Furthermore, the maximum gas pressure, the mean gas temperature, and the maximum pressure rise rate increase smoothly with the increase of premixed ratio. Meanwhile, when the premixed ratio reaches to a certain value, the maximum gas pressure and pressure rising rate increase remarkably. Regarding to the regulated emissions, CO and HC emissions are much higher than that of neat biodiesel fuel and increase up to the largest levels at a certain premixed ratio. After that, both the CO and HC emissions begin to decrease substantially. Smoke opacity decreases up to 35-55% at different equivalence ratios with the premixed DMM. At last, it is very interesting to find that the NOx emission decreases about 35% under overall operating conditions with up to 20% premixed DMM.