Detonation induction distances were obtained experimentally for hydrogen-oxygen mixtures having fuel concentrations of 45, 66.67 and 75 per cent hydrogen at initial pressures of 1 and 5 atmospheres in a detonation tube with variable internal geometry. When three stainless steel rods of different diameters were located concentrically in the initiation region of the tube, the induction distances decreased as the diameter of the rods was increased. With a divergent, stepped-wall insert placed in the initiation, section of the tube, the induction distances were reduced greatly compared to those obtained in a straight cylin¬drical tube at 1 atmosphere initial pressure. When the tube had a right-angle section located 66 cm from the ignitor, a detona¬tion wave formed immediately past the corner for all fuel con¬centrations at 1 and 5 atmospheres initial pressure except for the stoichiometric mixture at 5 atmospheres pressure for which a detonation wave formed in less than half the distance from the ignitor to the corner.
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