Investigation of the Ignition Properties of Flowing Combustible Gas Mixtures

Ignition delay times, ignition temperatures, and spontaneous ignitions were determined for several combustible gas mixtures behind incident and reflected shock waves passed into the static or flowing gases. The conditions leading to spontaneous ignition of flowing hydrogen-oxygen mixtures without the presence of shock waves were also determined. Hydrogen air mixture did not ignite spontaneously under the range of experiments conducted. Although certain observations indicate that the spontaneous ignition can be produced by aerodynamic heating, it must be assumed that other phenomena could also cause these ignitions. The observed high temperatures in the resonating gases should have been sufficient to ignite the hydrogen-air mixtures. While the ignition temperature and ignition delay time of methane-air and ethylene-air mixtures do not depend on the motion of the unburned gas mixture, those of hydrogen-air mixtures were much lower behind incident than behind reflected shock waves. A brief discussion of the mechanism of ignition under the various conditions is included.