Initiation and sustaining mechanisms of stabilized Oblique Detonation Waves around projectiles

Abstract

Colloquium that describes the research topic:DETONATIONS, EXPLOSIONS and SUPERSONIC COMBUSTION including pulse-detonation and scramjet engines. Total length of paper and method of determination:6186 words (Method 1) 6. List word equivalent lengths for main text, nomenclature, references, each figure with caption, and each AbstractDirect initiations and stabilizations of three-dimensional conical detonation waves were attained by launching spheres with 1.06 to 1.31 times the C-J velocities into detonable mixtures. We conducted high time-resolution Schlieren visualizations of the whole processes over unsteady initiations to stable propagations of the stabilized Oblique Detonation Waves (ODWs) using a high-speed camera. The detonable mixtures were stoichiometric oxygen mixtures with acetylene, ethylene or hydrogen. They were diluted with argon in a 50% volumetric fraction, and a 75% diluted mixture was also tested for the acetylene/oxygen. The direct initiation of detonation by the projectile and the DDT process like the Re-initiation appeared in the initiation process of stabilized ODW. This process eventually led to the stabilized ODW supported by the projectile velocity and the ringed shape detonation wave originating in the Re-initiation. We modeled the spatial evolution of stabilized ODW after the Re-initiation based on its C-J velocity and angle. The model qualitatively reproduced the measured development rate of stabilized ODW. We also discussed about the detonation stability for the curvature effect arising from the three-dimensional nature of stabilized ODW around the projectile. The curvature effect attenuated the detonation wave below its C-J velocity at the vicinity of projectile. The propagation limits of curvature effect will be responsible for the criticality to attain the stabilized ODWs. By accessing the detailed distributions of propagation velocities and curvature radiuses, the critical curvature radiuses normalized by the cell sizes experimentally revealed to be 8 to 10 or 15 to 18 for mixtures diluted with each 50% argon or 75% argon / krypton.(258 words)

Numerical study of wedge-induced oblique detonations in unsteady flow

“…ODWs induced by a conical shock or spherical projectiles are simulated to study the initiation structures and formation mechanisms (Ju, Masuya & Sasoh 1998; Maeda, Kasahara & Matsuo 2012; Maeda et al. 2013). Another setting of inflow inhomogeneity, considering the effects of non-ideal mixing, was simulated recently, illustrating several distorted reactive fronts (Iwata, Nakaya & Tsue 2016, 2017; Fang et al.…”

“…The finite wedge or double wedge, which introduces an expansion wave in the initiation region or detonation product, is found to change the interaction of supersonic inflow and oblique shock-induced heat release (Qin & Zhang 2018;Fang, Hu & Teng 2018). ODWs induced by a conical shock or spherical projectiles are simulated to study the initiation structures and formation mechanisms (Ju, Masuya & Sasoh 1998;Maeda, Kasahara & Matsuo 2012;Maeda et al 2013). Another setting of inflow inhomogeneity, considering the effects of non-ideal mixing, was simulated recently, illustrating several distorted reactive fronts (Iwata, Nakaya & Tsue 2016Fang et al 2017).…”

Initiation structure of oblique detonation waves behind conical shocks

“…However, the experimental studies on oblique detonations are typically performed by projectiles in the tube filled with premixed combustible mixtures, due to the limitation of the shock tunnel. 29 Recent experimental studies of detonation initiation by spherical projectiles included those by Kaneshige and Shepherd, 30 Higgins and Bruckner, 31 Kasahara et al, 32 and Maeda et al 33,34 These studies aimed at identifying the conditions under which a supersonic blunt projectile will initiate a detonation, as well as describing the formation structure and mapping different detonation initiation regimes. Numerical and theoretical investigations have also been performed by Ju et al 35 to determine the detonation initiation boundary based on the kinetic and energy limit concepts.…”

Estimation of the energy of detonation initiation in a hydrogen-oxygen mixture by a high-velocity projectile

“…For example, in work [14] the detonation limits of stoichiometric mixtures of H 2 /O 2 /Ar and H 2 /O 2 were experimentally studied. The initiation and stabilization of three-dimensional oblique detonation waves by spheres with velocities higher than the Chapman−Jouguet velocity in stoichiometric mixtures of oxygen with acetylene, ethylene or hydrogen diluted with argon were experimentally studied in [15]. Special attention should be paid to the works devoted to the numerical study of the detonation structure.…”