Abstract: Dimethyl carbonate(DMC) is one of the best additives for diesel engines due to its features such as highly oxygen content, lower boiling point. The compatibility of the DMC in the diesel fuel and engine power, fuel consumption and emission characteristics for different DMC fraction in blend fuel was investigated. Experimental results show that when the proportion of DMC in the blend is 0 % ? 20 % that smoke emission decreases, thermal efficiency increases with increasing in DMC proportion in diesel fuel without modifications on fuel injection and combustion system of the engine; when the pro?portion of DMC in the blend fuel is 10% ?20%，smoke emission is reduced by 40 % ?50%，thermal efficiency increases by I % ?3 %，engine power output is reduced by 4 % ?8 %，and the emission vari?ation of NOx, HC, CO, CO2 is very small. The investigative results show that the optimum DMC fraction in diesel fuel is 15% ; with 0% ?15% DMC fraction in blend fuel, the blend fuel is stable for a long time; the above results have direct significance on rational applied oxygenate blend fuel of diesel engine.

Key words: engineering thermophysics , blend fuel , dimethyl carbonate , solubility , optimum fraction