Experimental investigation on spray, evaporation and combustion characteristics of ethanol-diesel, water-emulsified diesel and neat diesel fuels

This paper explored the spray and combustion characteristics of ethanol-diesel (E10), water-emulsified diesel (W10) and neat diesel (D100), especially micro-explosion of E10 and W10. The experiments were conducted in a constant volume combustion chamber under cold (383 K, 0% O-2), evaporating (900 K, 0% O-2) and combustion (900 K, 21% O-2) conditions. Results showed that the spray expansion capacities of E10 and W10 under cold condition were much weaker than that of D100 due to the larger viscosity of emulsified diesels. Under evaporating condition, the spray volume of E10, W10 and D100 increased by 59%, 34% and 21% respectively comparing with cold spray volume. The higher increasing rates of E10 and W10 were mainly due to the microexplosion effects of ethanol and water contents. Under combustion condition, the integrated natural flame luminosity (INFL) demonstrated that the ethanol content could accelerate the oxidation of soot, while the water content could prohibit soot generation. Therefore, both ethanol-and water-emulsified diesels could inhibit the soot emission, causing lower final residual soot emission of E10 and W10 than that of D100 by 21% and 39% respectively. Moreover, the flame lift-off length (LOL) and flame spread velocity showed that the effects of micro-explosion in E10 and W10 are different. The micro-explosion in ethanol occurred earlier, which enhanced the reaction rate in upstream flame and reduced the LOL. However, the micro-explosion in W10 occurred later, which enhanced the combustion rate in downstream flame.