Evaporating spray characteristics of a diesel-ethanol micro-emulsion

•The emulsion sprays are studied under realistic in-cylinder conditions (50 bar and 900 K).•The emulsion consists of 60% diesel, 20% ethanol and 20% (JME) (40% renewable content).•Liquid penetration, vapour penetration and spray spread angle of the emulsion match with diesel.•This qualifies the emulsion for use in an existing diesel engine without any modifications. In the present study, evaporating spray characteristics of a diesel-ethanol micro-emulsion are reported for the first time under realistic engine-like conditions. A diesel-ethanol emulsion has been prepared by using 60% diesel, 20% anhydrous ethanol and 20% JME as an emulsifier. The evaporating spray characteristics in terms of liquid penetration, vapour penetration, liquid length and spread angle have been measured for the emulsion and compared with those of diesel. A high-pressure chamber with optical access is used in the present study for spray characterization. The chamber is filled with nitrogen which is heated to reach a final experimental condition of 50-bar pressure and 900-K temperature. A custom-made single-hole nozzle with a hole size of 190-µm has been used for the study. Surprisingly, the results have shown that the liquid penetration and the vapour penetration of the emulsion match closely with those of diesel showing no influence of droplet micro-explosion on spray characteristics. It is surmised that the enhanced rate of evaporation is compensated by evaporative cooling of low boiling point fuel and higher boiling point of JME leading to similar liquid length for the emulsion and diesel.