Analysis of flame acceleration in open or vented obstructed pipes

Abstract

While flame propagation through obstacles is often associated with turbulence and/or shocks, Bychkov et al. [Physical Review Letters 101 (2008) Starting with an inviscid approximation, we subsequently incorporate hydraulic resistance (viscous forces) into the analysis for the sake of comparing its role to that of a jet-flow driving acceleration. It is shown that hydraulic resistance is actually not required to drive flame acceleration. In contrast, this is a supplementary effect, which moderates acceleration. On the other hand, viscous forces are nevertheless an important effect because they are responsible for the initial delay occurring before the flame acceleration onset, which was observed in the experiments and simulations. Accounting for this effect provides good agreement between the experiments, modelling and the present theory.

Propagation and Morphology of Premixed Flames in Obstructed Channels under Atmospheric and Supercritical Conditions

“…In addition, a unique trend is noticed for the -impact on . propagation, the oscillations agree with the modelling [35,36], experiments [34], and theory [36] of flames in channels with both ends open or vented in terms that all of the studies [35][36][37] identified steady flame propagation prior to fast acceleration. The regime of the quasi-steady propagation is also influenced by the blockage ratio α and the thermal expansion ratio Θ.…”

“…Bychkov et al [36], developed an analytical formulation for flame propagated in obstructed channels with both ends opened. The theorical formulation for inviscid flows is presented below.…”

“…Likewise, the thermal expansion Θ plays a similar role, lower gas expansion, means reduced propulsion forces and as a result, reduced propagation of the flame front. The nature of the exponential acceleration was explored by comparing the simulation results with the theory developed by Bychkov for channels [36] with closely packed obstacles and both ends open. The plots of this comparison show that the theory predicts the later stage of the exponential acceleration quite better than it predicts the early phase.…”

“…Additionally, the flame classification diagram needs to be improved using more data sets, to clearly classify the accelerating and non-accelerating regimes in obstructed channels with both ends opened. Also, the Bychkov theory for premixed flames in open channels [36] needs to be updated to incorporate the effect of gas compressibility. -APENG/(VM**2+UPENG*BPENG*VM-BPENG**2) ZF = P(K)*VM/(UG*T(K)) AMPPA = XCH4*YR*XCH4*YR*APPCH4 + XCH4*YR*XO2*YR*(1.0 -F12)* .…”

Effect of Non-Equidiffusivity on Premixed Flame Propagation in Obstructed Channels

“…It was suggested that the interaction of the expanded gas with the obstructed walls of the channel obstacle creates a turbulent feedback, which promotes the flame speed rapidly [11]. A similar result has been recently identified in the analytical study of FA in a vented obstructed channel by Bychkov et al [12]. The acceleration characteristics in channels with both ends open were found to be considerably weaker as compared to that in semi-open channels.…”