Further insight into the gas flame acceleration mechanisms in pipes. Part I: Experimental work

Abstract

Some years ago, one of the authors (Proust, 2015) published the conclusions of a rather large experimental work devoted to the gas flame acceleration down a long pipe. It was concluded that the flame propagation could be represented by a constantly accelerating piston. The acceleration parameter seems to be primarily linked to the expansion velocity of the burnt product. Other parameters seemed of secondary importance questioning in particular the respective roles of the turbulence of the flame and of the instabilities. Further experiments were performed using perfectly smooth and rough tubes (figure 1), varying the diameter of the pipe (150 and 250 mm) and the reactivity of the mixtures (methane-air and hydrogen air at various equivalence ratios). The smooth pipe is transparent enabling a direct visualization of the flame during the flame propagation and a refined resolution of the flame trajectory (in the steel pipes standard flame sensors were used). The pressure was measured at various locations but also the flow velocities in the boundary to try and detect any turbulence development. Only homogeneous and quiescent mixtures were studied and the flame was propagated from a closed ignition end toward the other open end. The results of the parametric study are presented in this paper.

Study on characteristics of methane explosion flame and pressure wave propagation to the non‐methane area in a connected chamber

“…The explosion‐induced combustion wave breaks through the membrane, forming a turbulent effect and pressure oscillation in a very short time. As a result, the flame becomes brighter 34,35 . In the subsequent flame propagation in the pipeline, the light signal changes insignificantly, mainly because of insufficient fuel supply during flame combustion and propagation.…”

“…As a result, the flame becomes brighter. 34,35 In the subsequent flame propagation in the pipeline, the light signal changes insignificantly, mainly because of insufficient fuel supply during flame combustion and propagation. Afterward, the flame signal weakens as it propagates in the pipeline.…”

Further insight into the gas flame acceleration mechanisms in pipes. Part II: Numerical work

“…It should be noted that according to the experiment interpretation (Daubech, 2018), turbulence may not play such an important role in the flame propagation history contrary to other phenomena like acoustics. This observation explains why the best numerical agreement is obtained with the laminar flame assumption.…”

“…The paper focuses on some experiments described in the parent paper (Daubech, 2018). In each case, the pipe is straight, 24-m long, open at one end and closed at the other.…”

“…Recent works (Daubech, 2018) enabled to measure pressure signals and flame speed histories for a set deflagrations occurring in long straight pipes with an open end for varying diameters and materials. These tests highlight the influence of :…”