Ignition and formaldehyde formation in dimethyl ether (DME) reacting spray under various EGR levels

Dimethyl ether (DME) an alternative to diesel in compression-ignition engines has gained interest in combustion research due to its high cetane number for fast ignition and ultra-low emission of particulate matter. Ignition and significant intermediate species including CH2O were experimentally studied in a constant-volume combustion vessel facility that includes a fuel injection system for spray-like behavior of liquid DME. Experiments of varied oxygen concentrations simulating several stages of exhaust-gas recirculation (EGR) were done to evaluate its corresponding effect on the flame structure and emissions from DME combustion and showed that there is a supporting link between CH2O formation and low-temperature combustion prior to diffusion-controlled flame uniquely for DME. The study suggested that the onset of CH2O depletion can be utilized as an ignition indicator