An optical investigation into the reactive fuel spray of high-pressure DME and Ethanol

Reducing harmful emissions and increasing thermal efficiency in internal combustion engines have been the foremost goals of modern engine research. Compression ignition (CI) engines offer advantages in terms of high-efficiency operation as the overall in-cylinder mixture is lean. High-pressure direct injection fueling systems, commonly employed in CI engines, allow for the precise control of the combustion through injection timing and heat release modulation with same-cycle multi-pulse injection. Diesel fuel has dominated the liquid energy sources for CI engines owing to its high reactivity and lubricity properties. The highly heterogeneous mixture criterion and the dependence on auto-ignition of CI engines allow for a wide range of fuels to be applicable for engine operation. Notably, ethers possess chemical properties similar to diesel such as high reactivity, albeit with improved volatility characteristics. In this research, the mixture formation and burning behaviour of the high-pressure fuel spray have been optically examined under engine-like background conditions using a constant volume combustion chamber and high-speed camera. Specifically, dimethyl ether (DME) and ethanol were injected into a high-pressure and high-temperature reactive background media. Both fuels have matching chemical compositions (C2H6O), yet vastly different combustion characteristics. Diesel fuel was tested at matching conditions as a reference. A pneumatic pump was used for high pressure DME fueling in order to match the injection pressure to that of diesel systems. The coloured images were analyzed and quantified to characterize the behaviour of the reactive fuel spray.