Experimental research on single-cycle detonation in tubes with an inner diameter of 6 millimeters

To investigate the characteristics of micro-detonation waves, experiments were carried out in tubes with an inner diameter of 6mm using ethylene and oxygen as fuel and oxidizer. It shows that the gaseous mixture could successfully develop steady detonation wave. The detonation strength and flame propagation mode were greatly affected by the equivalence ratio. The distance of deflagration-to-detonation transition (DDT) was obtained at different equivalence ratios. The shortest distance occurs at equivalence ratio 1.4, and detonation becomes unsteady when equivalence ratio is greater than 2.2. The process of flame propagation was captured by high speed camera at the equivalence ratio of 0.8, 1.4 and 2.2, respectively. Several kinds of flame shape were observed and the factors that influence the flame shape formation were analyzed. Detonation velocity and pressure were measured at three equivalence ratios. Results show that detonation pressure and velocity reach the maximum value at the equivalence ratio of 2.2 and the minimum value at 0.8, which is in good agreement with C-J detonation.