Regimes of gas combustion in a porous body of a cylindrical heat generator

Abstract

A stationary model of filtration combustion of a gas with allowance for conditions at the entrance to the porous body and conditions of heat exchange with the gas phase surrounding the burner and with the heat exchanger is proposed and numerically analyzed. Ranges of parameters where the regime of gas combustion with a narrow reaction zone near the outer surface of the porous body are determined. Mechanical stresses arising in the porous body owing to high temperature gradients and gas pressure in the pores are estimated. The rate of gas combustion and the radiative heat flux from the burner surface are plotted as functions of process-dependent parameters.

Thermal Explosion of a Gas Mixture in a Porous Hollow Cylinder

“…Thus, the values typical for the burner described in [11] are ξ 1 ≈ 0.83 and δ 10 3 , which allows us to conclude that the thermal explosion does not occur under real operating conditions of the porous burner shaped as a hollow cylinder, and the evolution of the disturbance inducing the temperature distribution in the burner with a maximum in the volume is always finalized by the transition to the profile with the maximum close to the outer surface, which is predicted by the model developed in [15]. It is obvious that δ * = δ min = δ * (θ 0 , ξ 1 , Le, Δπ, .…”

“…We assume that chemical transformations in the gas correspond to the global reaction scheme "reagent-reaction product" and that the interphase heat transfer (between the gas in the pores and the porous skeleton) is perfect. Under the process conditions, gas burning proceeds in a certain stationary (quasi-stationary) regime, which can be characterized by the reaction front position and by stationary distributions of temperature and other quantities (see, e.g., [11]). The following question arises: Is such a stationary regime stable?…”

Numerical Study of the Heat Radiation from the Porous Cylindrical Burner with Radiative Heat Exchange

“…The aim of this paper is to develop a model of filtration combustion in cylindrical porous body, which takes into account the radiation transfer both inside of the porous media and the radiation flux from the burner to the ambient surroundings. The geometry of the burner is chosen so that the flame can be stabilized for the large range of the gas flow rates due to cylindrical radial flow [4,5,10]. This geometry allows detailed investigations of effects of radiative heat transfer on the characteristics of the combustion wave stabilized inside the porous burner.…”

Unsteady combustion of gases in an inert porous layer

“…Unsteady filtration flow of a stoichiometric gas mixture through a porous layer obeys Darcy's law and is determined by both on the pressure gradient at the outer boundaries of the layer and the pressure distribution in the layer. In some studies, it is assumed that the gas flow rate is constant [4][5][6], which allows one not to consider the equation of motion of the gas. Initiation of combustion for devices based on the mechanism of filtration gas combustion is carried out at the outlet of the gas flow from the porous layer by pulsed conductive supply of heat or a pilot flame to the outer surface of the porous bed -ignition toward the flow.…”