Flame propagation through the header of an in-line flame arrester

Abstract

This paper reports results of testing a pilot model of a flame arrester for flashback and burnout. The results are treated using the unsteady model of filtration gas combustion. It is shown that the process of burnout of the flame arrester consists of three stages with comparable characteristic times: the stage of flame entry into the porous bed, the stage of flame propagation through it, and the stage of flame exit from the porous bed. The mechanisms operating in each of the stages are described, and the determining parameters are established. Ways of improving the flame arrester performance are studied by theoretical analysis of the burnout process.

Burning-through of porous flame arresters with a channel flame-arrester element

“…The system was solved numerically. A detailed description of the system of equations and the method used for their solution are given in [10].…”

“…The calculations were performed for a stoichiometric methane-air mixture. For the gas mixture, the following parameter values were adopted [10]: constant pressure specific heat capacity c p = 10 3 J/(kg · K), thermal conductivity λ = 0.1 W/(m · K), and adiabatic flame temperature T b = 2320 K. The chemical reaction rate was given by W = ηk 0 exp(−E/RT ), where η is the relative concentration of the deficient component of the gas mixture, k 0 = 1 · 10 11 sec −1 , E = 2.26 · 10 5 J/mole, and R is the gas constant. The values of the param- eters of the porous medium were varied.…”

“…It has become clear that burning-through is caused by flame propagation through the flame arrester element in the regime of low-velocity filtration gas combustion (FGC) [6,8,9]. This concept in a one-dimensional approximation has been used [10] to analyze the burningthrough of packed-bed flame arresters. The major result of the analysis was the identification of two stages in the burning-through process: flame entry into the porous element and flame propagation in it, which has been proved by experimental observations [10].…”

“…This concept in a one-dimensional approximation has been used [10] to analyze the burningthrough of packed-bed flame arresters. The major result of the analysis was the identification of two stages in the burning-through process: flame entry into the porous element and flame propagation in it, which has been proved by experimental observations [10]. Accordingly, the total fire-resistance time of a flame arrester is the sum of the times of these two stages.…”

“…Accordingly, the total fire-resistance time of a flame arrester is the sum of the times of these two stages. It has been shown (in calculations and experiments) [10] that, under the most severe conditions, the fire resistance of packed-bed flame arresters is determined by the propagation time. Therefore, everything that reduces the flame propagation velocity in the porous bed promotes an increase in the fire resistance of the flame arrester.…”