Experimental study on the combustion characteristics of emulsified diesel in a rapid compression and expansion machine

The combustion characteristics of emulsified diesel fuels are investigated in a rapid compression and expansion machine (RCEM). Among the test cases, the 40 water-oil (W/O) fuel injected at 20° before top dead center (BTDC) has shown the best performance with respect to efficiency and NO_x and soot emissions. The pressure trace of the 40 W/O fuel is characterized by a longer ignition delay and a lower rate of pressure rise in premixed combustion. High-speed photographs show reduced flame luminosity and lower flame temperature with increasing W/O ratio. Microexplosions of emulsified fuel droplets, which affect the local shape and brightness of the flame, are identified in magnified flame images.