Smoked foil on deflagration-to-detonation transition

Single-shot experiments for propane/oxygen mixtures under atmospheric conditions were conducted to investigate the effect of the thickness and the axial location of an aluminum sheet on the deflagration-to-detonation transition (DDT). The smooth tube was constructed from 6061-T6 aluminum, with a length of 1143 mm and an inner tube diameter of 101.6 mm. The ignition system consisted of a transformer and an electric spark at the closed end. The duration and energy of the electrical discharge were estimated to be 2 ms and 0.47 J, respectively. The proportions of propane and oxygen were determined using the method of partial pressures with an equivalence ratio ranging from 0.6 to 1.0. Single-shot experiments were performed with initial reactant conditions at ambient temperature and atmospheric pressure. The study shows that caution must be exercised in using smoked foil results for developing pulse detonation engine (PDEs). The smoked foil should be placed well downstream of the end of transition. In particular, the crucial issue of DDT for practical sizing of a PDE should be carefully assessed. Detonation cell size is commonly used to guide in sizing the diameter of a PDE.