Chemiluminescence Imaging of Biofuel Isomers Ethanol and Dimethyl Ether Sprays in a Pressurized Environment

Reducing emissions and increasing thermal efficiency in internal combustion engines have been the foremost goals of combustion research. The fuel spray development and subsequent chemical reaction processes heavily influence the combustion completeness concerning the surrounding environment and explicitly determine its suitable application as a fuel for combustion. Recently, strong efforts to mitigate the complete dependency on diesel fuel for heavy-duty internal combustion engines using alternative fuels made available by renewable feedstocks. The biofuel C2H6O isomers of dimethyl ether (DME) and ethanol are of interest for their simplistic chemical composition, ease of production, and opposite chemical applications wherein the autoignition temperature of ethanol is comparatively high. Nonetheless, the high fuel-borne oxygen can limit net soot formation and therefore is attractive as an alternative fuel to direct injection engines. In this work, high-pressure fuel sprays of ethanol and dimethyl ether reactions are empirically recorded using a pre-burn technique inside a constant volume chamber. The high-speed images were analyzed and processed for quantitative comparisons including the total effective coverage, light intensity, and chemiluminescence distribution of the sprays. The opposite reactivity characteristics among isomers were apparent as the natural chemiluminescence visibility became limited at a background temperature lower than 1546 K. The enhanced volatility of DME presented little challenge in high-intensity luminosity even under lower background temperatures. Furthermore, blue flame reactions were apparent with DME sprays in an increased oxygen content (15%) environment and extended mixing periods. The suitability of high-pressure ethanol spray reactions is constrained to elevated supply pressures and thermal environments to overcome mixing and ignition limitations.