Semi-confined layered kerosene/air two-phase detonations bounded by nitrogen gas

Abstract

A two-dimensional numerical study is conducted on the semi-confined cellular detonations propagating through a layer of two-phase kerosene/air reactant bounded by an inert gas. By fixing a global equivalence ratio, a series of cases are simulated to investigate the effects of the background vapor/liquid droplet equivalence ratios (φg and φd) and droplet diameters. The results show that the propagation and failure of the layered detonation are strongly affected by the equivalence ratios and droplet diameters. When φg is 0.8, layered detonations can propagate at a droplet size of 5, 10, and 20 µm, while it fails when the droplet size is increased to 40 µm. When φg is less than 0.8, the self-sustained layered detonation can only be obtained with a small droplet size of 5 µm and a high φg above 0.5. The detonated fuel fraction and droplet contribution efficiency are found to be sensitive to the droplet diameter. It is found that the transverse detonation is a manifestation of the self-sustained ability of detonation waves. The loss of triple points leads to the appearance of transverse detonation whereas the transverse detonation can generate new triple points and stabilize the detonation front. The transverse detonation can significantly enhance the mass transfer and heat release even though it occurs behind the sonic line, which promotes the detonation re-initiation. Besides, it is found that h/λ=2.90 (h is reactant layer height and λ is cell width) is the critical value for the successful propagation of layered detonations in this study, which agrees well with the existing experiments. In addition, reflection efficiency is introduced and is effective in predicting the strength of the weak confinement.