Turbulent Structure of Gaseous Detonation

TLDR

The study aims to examine how turbulence affects a Chapman‑Jouguet detonation, defining CJ as the minimum propagation velocity that satisfies conservation relations for turbulent flow at the reaction‑zone rear. Detonations of 2H₂+O₂+2CO were investigated in a shock tube over 0.01–1.4 atm, measuring pressure, interferometric density, and luminosity proportional to [CO][O], and the turbulence implications on CJ propagation were analyzed. Strongly overdriven waves are one‑dimensional and reach equilibrium, while self‑sustaining detonations leave a lower‑pressure, supersonic, turbulent state; incorporating turbulence raises the minimum CJ velocity slightly, and.

Abstract

Self-sustaining and overdriven detonations in 2H2 + O2 + 2CO have been studied in a shock tube at initial pressures from 0.01 to 1.4 atm. Measurements have included pressure, density obtained interferometrically, and luminosity whose intensity is shown to be proportional to [CO][O]. Strongly overdriven waves are one dimensional and are followed by the calculated equilibrium state. Self-sustaining detonations are followed by a state in which the pressure and density are lower than calculated according to the usual C-J hypothesis, and in which the flow is supersonic with respect to the wave front. Furthermore, the flow in and behind the reaction zone invariably appears to be turbulent. In an examination of the implications of this turbulence, a Chapman-Jouguet detonation is considered to be one with the minimum velocity of propagation which will satisfy the conservation relations for turbulent flow at the rear of reaction zone. It is shown that this minimum (C-J) velocity is slightly greater than that calculated assuming turbulence is not present, and that the final state attained following the decay of turbulence can lie either on the ``strong'' or ``weak'' detonation branch of the Hugoniot curve. Intermediate states, including the conventionally calculated C-J state, in general do not represent stable solutions. The self-sustaining detonation, which must correspond to the weak detonation solution, appears as a special case of a C-J detonation.