Abstract:

In order to reveal the influence of small perturbations on the failure and re-initiation of normal detonation and quasi-detonation waves, experimental were carried out on acetylene-oxygen mixtures. Firstly, thin metal plates of different lengths were arranged in the explosion chamber to introduce small-scale perturbations. Then, helical springs with wire diameters of 7 and 9 mm were used to construct rough wall surfaces for generating quasi-detonation. Finally, distributed photoelectric probes were employed to record the arrival times of detonation waves, and a high-speed schlieren system was combined to observe the diffraction and re-initiation processes of detonation waves. The research reveals that introducing minor perturbations significantly reduces the critical initiation pressure threshold. Below this critical initial pressure, re-initiation of the detonation wave is impossible, even with perturbations present. Conversely, above this critical pressure, planar detonation waves within the tube consistently transition to spherical detonation waves in all repeated experiments. The re-initiation site for normal detonation in a smooth tube consistently occurs near the thin plate, whereas the re-initiation location for quasi-detonation in a rough tube exhibits randomness. Quantitative analysis demonstrates distinct critical initiation criteria for the two detonation types: for the successful re-initiation of detonation, the ratio of the critical tube diameter to the detonation cell size must be greater than or equal to 13, while the critical threshold for the successful re-initiation of quasi-detonation is reduced to approximately 8 for the ratio of the critical tube diameter to the cell size.

Key words: acetylene-oxygen mixture, detonation failure, detonation re-initiation, quasi-detonations, critical pressure