Flame Acceleration in Channels with Obstacles in the Deflagration-to-Detonation Transition

TL;DR

This paper investigates a new, stronger mechanism of flame acceleration in obstructed channels, showing it progresses faster in cylindrical geometries and can lead to deflagration-to-detonation transition, with implications for safety and combustion control.

Contribution

It provides a detailed theory and numerical modeling of a novel flame acceleration mechanism that is independent of Reynolds number and differs from classical explanations.

Findings

Flame acceleration is faster in cylindrical geometry than in planar.

Acceleration rate decreases with increasing initial Mach number.

Transition from deflagration to detonation is demonstrated in obstructed channels.

Abstract

It was demonstrated recently in Bychkov et al., Phys. Rev. Lett. 101 (2008) 164501, that the physical mechanism of flame acceleration in channels with obstacles is qualitatively different from the classical Shelkin mechanism. The new mechanism is much stronger, and is independent of the Reynolds number. The present study provides details of the theory and numerical modeling of the flame acceleration. It is shown theoretically and computationally that flame acceleration progresses noticeably faster in the axisymmetric cylindrical geometry as compared to the planar one, and that the acceleration rate reduces with increasing initial Mach number and thereby the gas compressibility. Furthermore, the velocity of the accelerating flame saturates to a constant value that is supersonic with respect to the wall. The saturation state can be correlated to the Chapman-Jouguet deflagration as well as the fast flames observed in experiments. The possibility of transition from deflagration to detonation in the obstructed channels is demonstrated.