Propagation Of Combustion Front Research Articles

Modes of burning in filtration combustion

We describe and analyze a model of filtration combustion, in which a gas is forced at high pressure into a porous solid matrix so that after ignition and under favourable conditions a combustion wave can propagate through the medium. We consider the case of counter flow, where the gas is forced into the reaction zone through the unreacted part of the porous solid. Relations are derived for the steady state propagation of a planar combustion wave or front in the limit of high-activation energy, from which the propagation speed, reaction temperature, and reacted mass fraction of the solid product can be found in terms of the mass flux of the injected gas, the gas pressure and mass flux on exit from the front, and other physico-chemical parameters describing the system. Two distinct modes of combustion are discussed, corresponding to the reaction being driven to completion by exhaustion of either the gaseous or the solid component, these being referred to as the gas-deficient and solid-deficient modes of burning respectively. For both homogeneous and heterogeneous forms of the reaction rate we find that there is a critical inlet mass flux for the incoming gas below which steady state solutions no longer exist and that there are parameter values for which multiple steady states occur.

Two‐dimensional numerical study of cross‐flow filtration combustion

AbstractTransition metal nitrides can be synthesized in the combustion regime using a self‐propagating, high‐temperature synthesis by the process of filtration combustion. A detailed two‐dimensional numerical study for the filtration combustion process in the cross‐flow configuration is presented. The process is modeled by a two‐dimensional pseudohomogenous model. The model equations, which are very stiff and exhibit varying time and length scales, are solved using finite differences on a two‐dimensional orthogonal adaptive mesh. The effects of pressure, bed height and bed porosity on combustion front propagation and final conversion are studied. A series of full simulations for the titanium‐nitrogen system shows good agreement between theoretical predictions and experimental observations.

Influence of thermophysical characteristics of an inert obstacle and heat losses on combustion wave propagation

The influence of the thermophysical characteristics of an inert interlayer substance and its thickness and the influence of heat elimination to the environment on combustion wave propagation through an inert obstacle were investigated. An infinite specimen of substance capable of exothermal chemical reaction, into which an inert substance interlayer had been inserted, was considered. A stationary combustion front was propagated toward the interlayer. The process of nonstationary combustion front propagation through the inert obstacle under the assumption of averaging the temperature over the thickness and of dependence of the reaction rate on the temperature according to the Arrhenius law was modeled by a system of differential equations.

Detection property of a curved flame front

As has been established in numerous experiments, the break lines along which the flame cells about each other do not remain at their points of formation (as was proposed in previous studies), but can move along the combustion surface (9). In the present study this effect of longitudinal displacement of the break lines with possible subsequent merger of several lines into one was the object of detailed investigation using numerical experiment. It was established that as a result of interaction of break lines the lines are redistributed in accordance with the wavelength of a sinusoid simulating the hydrodynamic flow. This property of singling out (detecting) the long wave modulating harmonic is a direct consequence of the effect of normal combustion front propagation.

Propagation and Extinction of Combustion Fronts in Crushed Oil Shale

The effects of oil shale particle size and Fischer assay on the extinction air flux, the air flux at which the combustion front cannot operate, were studied using a small laboratory-scale retort. It was found that for runs with air consisting of 21 percent oxygen by volume, the extinction air flux is strongly dependent on the particle size and Fischer assay. The smaller oil shale particle sizes led to higher observed extinction air flux, while the leaner shale resulted in lower observed extinction air flux.

Principles of the spin mode of combustion front propagation

A mathematical model of the spin mode of combustion propagation on a cylindrical surface is developed. The model is a system of two-dimensional nonlinear partial differential equations, which are solved numerically by an implicit conservative two-dimensional difference scheme and a cross-drive method. Parametric effects in the spin combustion process are examined, and theoretical results are compared with experimental data.

Chemical Aspects of In-Situ Combustion - Heat of Combustion and Kinetics

Abstract General remarks on the oxidation reactions of hydrocarbons involved in in-situ combustion are followed by estimates of heat releases. A formula is derived for computing the heat of combustion in the high-temperature zone. Reaction kinetics in porous media applied to the in-situ combustion porous media applied to the in-situ combustion process is discussed. It is observed that there is process is discussed. It is observed that there is some similarity between the kinetics of reverse and partially quenched combustion processes. The influence of additives on crude oil oxidation in porous media is illustrated by effluent gas analysis experiments. Some information concerning the values of the kinetic parameters of the reaction controlling the velocity of a reverse combustion front is derived from the interpretation of laboratory experiments, using a numerical model. Introduction A great deal of laboratory and field work has been done on thermal recovery methods. The importance and limitations of these techniques have been extensively studied. However, some of the chemical and physical problems involved that needed to be elucidated were studied as part of a research program carried out by the Institut Francais du Petrole. Specific problems are created by in-situ combustion since both the possibility of combustion-front propagation and the air requirement are controlled by the extent of the exothermic oxidation reactions. Actually, the propagation velocity of a forward combustion front depends on the fuel formation and combustion, which are controlled by the kinetics of these processes; furthermore, the peak temperature is related to the heat released by oxidation and combustion reactions. Therefore, a quantitative estimation of the parameters related to the chemical aspects of the parameters related to the chemical aspects of the process is a necessary step in studying combustion process is a necessary step in studying combustion through a porous medium. General and theoretical considerations on heats of reaction and kinetics are presented and illustrated by experimental data and numerical interpretation of the results.