Detonation Characteristics of Dimethyl Ether, Methanol and Ethanol Air Mixtures

Abstract

The detonation characteristics of dimethyl ether-air, methanol-air and ethanol-air mixtures, initially at atmospheric pressure and a temperature range of 298K to 373K, were investigated in this study. Experiments were performed in a heated detonation tube, 6.1m long with an inner- diameter of 10cm. Transition to detonation was achieved for fuel-air mixtures by spark ignition and subsequent flame acceleration using orifice plate obstacles in the first half of the tube, and via a gas driver with a short orifice plate obstacle section. Cell width measurements where obtained using the soot foil technique for fuel-air mixtures inside the detonation limits. The measurements show that dimethyl ether-air, methanol-air and ethanol-air mixtures are less “sensitive” to detonation than propane-air and ethane-air mixtures, but more sensitive than methane-air mixtures, within the tested temperature range. Soot foil records also indicated the presence of substantial cellular substructure for all three fuel-air mixtures. One-dimensional detonation reaction zone length calculations were performed and fit with the measured cell width using a simple linear correlation, which resulted in an accurate representation of the data. The correlation proportionality constants for dimethyl ether-air, methanol-air and ethanol-air were obtained for the dominant cellular structure as well as the substructure. The values obtained for the substructure are comparable to values reported in the literature for typical hydrocarbons.