Direct experimental impulse measurements for detonations and deflagrations

Direct impulse measurements were carried out by using a ballistic pendulum arrangement for detonations and deflagrations in a tube closed at one end. Three tubes of different lengths and inner diameters were tested with stoichiometric propane- and ethylene-oxygen-nitrogen mixtures. Results were obtained as a function of initial pressure and percent diluent. The experimental results were compared to predictions from an analytical model and generally agreed to within 15% (Wintenberger, E., Austin, J., Cooper, M., Jackson, S., and Shepherd, J. E., "Analytical Model for the Impulse of a Single-Cycle Pulse Detonation Engine, AIAA Paper 2001-3811, July 2001). The effect of internal obstacles on the transition from dellagration to detonation was studied. Three different extensions were tested to investigate the effect of exit conditions on the ballistic impulse for stoichiometric ethylene-oxygen-nitrogen mixtures as a function of initial pressure and percent diluent.