The mechanism of flame propagation in fuel beds of wildland fires is important to understand in order to quantify fire spread rates. Fires spread by radiative and convective heating and often require direct flame contact to achieve ignition. The flame interface in an advancing fire is unsteady and turbulent, making study of intermittent flames in complex fuels difficult. A vertical wall fire, i...

Experimental propane/air Bunsen flame at atmospheric pressure are investigated in the context of DarrieusLandau (DL) instability. Results from asymptotic theory are utilized in order to estimate the non-dimensional critical length scale δc = LD/λc (LD the flame thickness and λc the critical length scale). The non-dimensional flame thickness δ = LD/L is varied either by varying the equivalence r...

Here u = u(x, t) and f(u) is smooth, convex, and satisfies f(0) = f′(0) = 0. The choice f(u) = u/2 has been shown previously to arise in connection with the physical problem of upward flame-front propagation in a vertical channel in a particular parameter regime. In this context, the shape y = y(x, t) of the flame-front interface satisfies u = −yx. For this problem, it is shown that the princip...

This paper treats the problem of tracking contours of flames captured by PLIF imaging using geodesic paths and level sets. Successive images of the combustion process captured in controlled experiments are smoothed by non-linear diffusion filtering then active contour models are used to obtain the curves that most accurately describe the flame boundary. These curves are matched using the concep...

The recently developed Flexible Local Approximation MEthod (FLAME) produces accurate difference schemes by replacing the usual Taylor expansion with Trefftz functions – local solutions of the underlying differential equation. The paper introduces a significant extension of FLAME: a least-squares fit instead of the exact match of the approximate solution at the stencil nodes. As a consequence of...

A nonlinear equation describing curved stationary flames with arbitrary gas expansion θ = ρfuel/ρburnt, subject to the Landau-Darrieus instability, is obtained in a closed form without an assumption of weak nonlinearity. It is proved that in the scope of the asymptotic expansion for θ → 1, the new equation gives the true solution to the problem of stationary flame propagation with the accuracy ...

Recognizing that previous experimental studies on constant-pressure, outwardly propagating, spherical flames with imaging capability were limited to pressures less than about 5 atm, and that pressures within internal combustion engines are substantially higher, a novel experimental apparatus was designed to extend the environmental pressure to 60 atm. Results substantiate previous observations ...

Early and accurate detection and localization of flame is an essential requirement of modern early fire warning systems. Video-based systems can be used for this purpose; however, flame detection remains a challenging issue due to the fact that many natural objects have similar characteristics with fire. In this paper, we present a new algorithm for video based flame detection, which employs va...