Flame propagation through dust clouds of carbon, coal, aluminium and magnesium in an environment of zero gravity

Abstract

The mechanism and the rate of flame propagation through dust clouds of carbon, coal, aluminium and magnesium have been investigated. Any errors due to the upward buoyant motion of burnt gases and the downward settling velocity of dust particles were eliminated by conducting these experiments in a zero-gravity environment. A technique of flat-flame propagation was developed to measure the burning velocity accurately. The results show that the burning velocity is influenced by particle size, fuel transfer number, dust concentration, volatile matter (for coal), oxygen enrichment and heat loss by radiation from the burning fuel particles. A simple model to elucidate the structure and the mechanism of flame propagation is developed. Then expressions to predict the flame thickness and the burning velocity are derived. Attention is drawn to the similarity that exists between the mechanisms of flame propagation through dust clouds and through fuel mists. The importance of radiation heat loss is emphasized. It is shown that for a dust cloud of particle size 10 μ m of graphite or aluminium in oxygen, radiation loss from particles can reduce the burning velocity by as much as 40% or 25% respectively.

Discrete-continual model of flame propagation in a gas suspension of metal particles. II. Allowance for the pre-flame oxidation reaction

“…for d p,0 = 50 µm and ρ 2,0 = 0.42 kg/m 3 , the computations yield l f /d p,0 = 30.6, which is in line with the theoretical estimate l f /d p,0 ≈ 35 obtained in [3].…”

“…for the pre-flame oxidation reaction offers a satisfactory description of the experimental data of [3,4]. Note, the values of u f in these papers have certain differences.…”

“…1. Effect of the mean density of the disperse phase on the combustion-wave velocity in a mixture of air and magnesium particles: the points refer to the data of [3]; the dashed and solid curves refer to the computations without allowance and with allowance for the ignition reaction, respectively; dp,0 = 15 (1) and 70 µm (2).…”

Direct combustion of recyclable metal fuels for zero-carbon heat and power

“…7. Laminar burning velocities of suspensions of methane, aluminum [113], iron [129], and magnesium [130] fuels in ''air" with variable oxygen concentrations. Methane laminar burning velocities calculated using the Cantera software package [131] and the GRI-Mech 3.0 chemical-kinetics mechanism [132].…”

Visualization of Dust Explosion Under Microgravity Conditions

“…The following phenomena also play an important role in dust combusDownloaded by [Institute of Mechanics] at 01:04 13 November 2013 tion: dust concentration, uniformity of the dust suspension, dust sedimentation in a gravity field and the ignition energy and type of the ignition system. Dust-air mixtures can be produced by means of turbulent mixing [Pu et al, 1998], fluidized bed techniques [Proust and Veyssiere, 1988], dust feed assembly [Ballal, 1983], acoustic field [Berlad, 1981], or electrical field [Peraldi et al, 1993]. All these methods have visible effects on the combustion process.…”