An experimental investigation on ignition and combustion of diethyl ether/iso-octane spray

The spray auto-ignition and combustion phenomenon of iso -octane/diethyl ether (DEE) and their blends under different ambient temperatures, pressures and oxygen concentrations have been investigated by using an optical rapid compression machine (RCM) and high-speed imaging. Results show that at low temperature, pressure and DEE blending ratio, the combustion manifests as a premixture, characterized by the emergence of the flame kernel following complete evaporation of the liquid fuel. The ignition delay time is then progressively and nonlinearly reduced with increasing DEE blending ratio, ambient pressure and temperature such that when these quantities are sufficiently high, the fast chemical reaction rate leads to a competing relationship with the physical evaporation/mixing rate of spray. This makes the combustion behavior change from a single-stage mode to a two-stage mode, specifically from premixed to diffusion combustion, and significantly affect the auto-ignition and combustion performance of the spray. The different spray combustion modes are shown in a regime diagram as function of the temperature and DEE blending ratio for better understanding of the effect of DEE addition on spray auto-ignition and combustion behaviors. This work provides new experimental data and understanding on the spray auto-ignition and combustion behaviors of DEE/ iso -octane blends.