The combination of emulsified diesel and low temperature combustion (LTC) technology\nhas great potential in reducing engine emissions. A visualization study on the spray and combustion\ncharacteristics of water emulsified diesel was conducted experimentally in a constant volume\nchamber under conventional and LTC conditions. The effects of ambient temperature on the\nevaporation, ignition and combustion characteristics of water emulsified diesel were studied under\ncold, evaporating and combustion conditions. Experimental results showed that the ambient\ntemperature had little effect on the spray structures, in terms of the liquid core length, the spray\nshape and the spray area. However, higher ambient temperature slightly reduced the Sauter Mean\nDiameter (SMD) of the spray droplets. The auto-ignition delay time increased significantly with\nthe decrease of the ambient temperature. The ignition process always occurred at the entrainment\nregion near the front periphery of the liquid core. This entrainment region was evolved from the early\ninjected fuel droplets which were heated and mixed by the continuous entrainment until the local\ntemperature and equivalence ratio reached the ignition condition. The maximum value of integrated\nnatural flame luminosity (INFL) reduced by 60% when the ambient temperature dropped from 1000\nto 800 K, indicating a significant decrease of the soot emissions could be achieved by LTC combustion\nmode than the conventional diesel engines.
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