An Experimental Study of Spiral Effect on Deflagration to Detonation Transition

The objective of this paper is to experimentally investigate the effects of Shchelkin spiral geometry in the transition from deflagration to detonation on the quality of the produced detonation. Deflagration to detonation transition (DDT) is required in cases where ignition energy release is less than the critical ignition energy required for a direct detonation initiation. A stoichiometric mixture of hydrogen–oxygen has been used in a tube of 25 mm diameter and 700 mm length. Spiral coils have been mounted at the ignition-end of the tube to facilitate DDT. Keeping spiral coil diameter fixed at 22mm, the coil length, pitch and thickness were varied to produce desirable detonation waves. Spiral coil selection was based on several criteria including; the pressure and velocity jump across the wave at the beginning of the tube, and the percentage of successful tests in each batch. The results indicate that the spiral coil pitch has the greatest influence on minimizing the DDT length and obtaining a desirable detonation.