Propagation of a stable gaseous detonation in a circular arc configuration

The present work revisits the problem of modelling the real gaseous detonation dynamics at the macro-scale by simple steady one-dimensional (1D) models. Experiments of detonations propagating in channels with exponentially expanding cross-sections (exponential horns) were conducted in the H 2 /O 2 /Ar reactive system. Steady detonation waves were obtained at the macroscale, with cellular structures characterized by reactive transverse waves. For all the mixtures studied, the dependence of the mean detonation speed was found to be in excellent agreement with first principles predictions of quasi-1D detonation dynamics with lateral mass divergence predicted from detailed chemical kinetic models. This excellent agreement departs from the earlier experiments of Radulescu and Borzou (2018) in more unstable detonations. The excellent agreement is likely due to the much longer reaction zone lengths of diluted hydrogen oxygen detonations at low pressures, as compared with the characteristic induction zone lengths. While the cellular instability modifies the detonation structures induction zone, the detonation dynamics at the macro-scale are arguably controlled by its hydrodynamic thickness. Near the limit, minor discrepancy is observed, with the experimental detonations typically continuing to propagate to slightly higher lateral strain rates and higher velocity deficits.

Section: Propagation Of 2h 2 /O 2 /2ar Detonations Along the Large Rampmentioning

confidence: 99%

Dynamics of hydrogen–oxygen–argon cellular detonations with a constant mean lateral strain rate

Xiao

Radulescu

2020

“…Promising RDE geometries are the hollow and semi-hollow configurations in which the internal wall of the combustor is fully or partially removed, resulting in larger specific impulse, pressure and rotation frequencies, e.g., [5]. Literature includes experimental, numerical and theoretical studies on detonation propagation inside annular RDEs [6,7,8], curved channels/chambers of constant and varying widths [9,10,11,12,13,14,15,16], wedges and bends [17], and U-bend tubes [18]. Loss-of-coolant accidents in nuclear reactors may result in significant releases of hydrogen and the generation of flammable atmospheres that accumulate between the containment and the curved reactor building [19].…”

Section: Introductionmentioning

confidence: 99%

Dynamics of detonation transmission and propagation in a curved chamber: a numerical and experimental analysis

Melguizo-Gavilanes

Rodriguez

Vidal

et al. 2021

The dynamics of detonation transmission from a straight channel into a curved chamber was investigated numerically and experimentally as a function of initial pressure (10 kPa ≤ p 0 ≤ 26 kPa) in an argon diluted stoichiometric H 2 -O 2 mixture. Numerical simulations considered the two-dimensional reactive Euler equations with detailed chemistry; hi-speed schlieren and OH* chemiluminescense were used for flow visualization. Results show a rotating Mach detonation along the outer wall of the chamber and the highly transient sequence of events (i.e. detonation diffraction, re-initiation attempts and wave reflections) that precedes its formation. An increase in pressure, from 15 kPa to 26 kPa, expectedly resulted in detonations that are less sensitive to diffraction. The decoupling location of the reaction zone and the leading shock along the inner wall determined where transition from regular reflection to a rather complex wave structure occurred along the outer wall. This complex wave structure includes a rotating Mach detonation (stem), an

“…They observed a complex structure composed of an oblique shock and a deflagration and propagating with the CJ velocity. Short et al [23,24,25] studied experimentally and numerically the dynamics of steady detonation propagation in a constant-cross-section, two-dimensional circular arc of high explosive. They observed that the angular speed of the detonation increases monotonically with increasing arc thickness before limiting to a constant.…”

Section: Introductionmentioning

confidence: 99%

An experimental evidence of steadily-rotating overdriven detonation

Rodriguez

Jourdain

Vidal

et al. 2019

This experimental work reports on detonation behaviors in a curved chamber without inner wall after diffraction of a Chapman-Jouguet (CJ) detonation from a straight channel tangent to the chamber outer wall. The upper and lower faces of the chamber receive either soot foils for recording the history of the transmission dynamics, or optical windows for schlieren high-speed visualizations. Tests were carried out with the stoichiometric propane-oxygen mixture at initial temperature 1 T 0 = 288 K and initial pressures ranging between 8 kPa and 15 kPa. The primary observation is the existence of an initial pressure range (8 kPa-12 kPa) for which, after diffraction transients, a Mach detonation can rotate normal to the outer wall with a constant angular velocity such that the normal front velocity at the wall is larger than the CJ value. The height of the Mach front decreases and its tangential velocity increases with increasing initial pressure. This over-driven detonation results from the irregular reflection of the initially-oblique front as the outer wall tilts with respect to the front, similarly to shock propagation in a continuouslyconverging channel. The Mach triple-point moves away from the wall and stabilizes its trajectory parallel to the wall. This Mach front shows detonation cells parallel to the wall with a constant mean width very small compared to that on the initial CJ front. A detonation can thus smoothly propagate in a curved chamber without center body, though the Mach front does not sweep the entire equivalent cross-section of the chamber. These observations are consistent with experimental results for RDE chambers without center body, or with linearly-increasing cross sections, that show improved properties of rotating detonation, compared to chambers with constant cross sections. This supports the interest of further studies on the hollow-chamber configuration of RDEs.