Self-Generated Acceleration of Confined Deflagrative Flame Fronts∗

∗This manuscript was a selected presentation from the Fifteenth ICDERS meeting held at Boulder, Colorado, during the period July 30-August 7, 1995.

Abstract

This paper deals with the investigation of laminar and turbulent flame front behaviour in the later stage of an confined explosion process where stretch effects can be neglected and for which experimental data of burning velocity and knowledge about the effect of flame-induced turbulence in a spherically propagating flame front are still limited.

It could be shown that for laminar explosion experiments there exists a radius range of the propagating flame front in which the influence of stretch due to the overall spherical shape as well as compression of the unburnt gas can be neglected, so that the burning velocity S is mainly influenced by flame-induced acceleration. Also turbulent flame fronts are accelerated, obviously by additional flame-induced turbulence, and in this case the flame front propagation can be based on an effective turbulence intensity (u'/S_{L, p}) _eff resulting from the superposition of fan-generated (u'/S_{L, p}) _meas and flame-generated (u'/S_{L, p}) _ind turbulence intensity. Finally, a linear increase of reduced turbulent burning velocity S_T/S_{L, P} with increasing effective turbulence intensity (u'/S_{L, p}) _eff and with the square root of the turbulent macro lengthscale L_T ^0.5 could be confirmed.

Keywords:

• Flame front instabilities
• flame acceleration
• flame-generated turbulence
• closed vessel gas explosion

Notes

∗This manuscript was a selected presentation from the Fifteenth ICDERS meeting held at Boulder, Colorado, during the period July 30-August 7, 1995.