A study of hydrogen azide detonation with heat transfer at the wall

The detonation of gaseous HN 3 was studied in tubes of 1, 2, 5 and 10 mm i.d. in 1–25 Torr pressure range. Detonation velocities were measured by different techniques and wall heat fluxes were deduced from the temperature recordings given by thin-film platinum resistance gauges. The propagation and stability of the wave were studied down to the critical conditions of detonation quenching. For the lowest pressures and smallest diameters, the detonation velocity D ф is about 30% lower than D ∞, the wave velocity independant of wall effect. D ∞ is some percents higher than D CJ , the Chapman-Jouguet velocity. The velocity deficit D ∞ − D ф is discussed in relation to the classical Fay's theory. The features of the temperature-time curves are analyzed in the whole range of pressure and diameter and especially near detonation limits. The heat transfer rates behind the detonation wave are computed from wall temperature recordings and compared to theoretical predictions provided by Mirels' theory. For the largest diameter and the highest pressures, experimental and theoretical values are in good agreement if a laminar regime in the boundary layer is assumed. In the narrowest tubes, near limit pressures, the temperature gradients behind the detonation wave are too large to use the ZND model and the Mirels' theory.