Gas Dynamic Features of Self Ignition of Non Diluted Fuel/Air Mixtures at High Pressure

Abstract

Abstract The self ignition of several non diluted fuel/air mixtures at high pressure is studied. Hydrogen, iso-octane and n-heptane have been used as fuels. Experiments have been performed using the shock tube technique. Various observation methods, such as recording of pressure and of light band emission and shadow cinematography have been applied. The type of self ignition as well as the ignition delay times can be determined using these techniques. The self ignition of all fuels takes place in many different modes. At high temperatures ignition at the end wall is achieved. All three fuels under investigation show mild and strong ignition as described by Oppenheim (1985). Mild ignition - characterized by establishing a deflagrative combustion mode at seperate independent reaction centers - also occurs at low temperatures, when the ignition process is within some limits-randomly distributed in time and space (hot spot ignition). Hydrogen shows this hot spot ignition with and without transition to detonat...