Abstract. This paper deals with a simplified model taking into account the interplay of compressible, laminar, axisymmetric flow and the electrodynamical effects due to Lorentz force's action on the combustion process in a cylindrical pipe. The combustion process with Arrhenius kinetics is modelled by a single step exothermic chemical reaction of fuel and oxidant. We analyze non-stationary PDEs with 6 unknown functions: the 3 components of velocity, density, concentration of fuel and temperature. For pressure the ideal gas law is used. For the inviscid flow approximation ADI method is used. Some numerical results are presented.
Abstract. The recent research is focused on experimental study and mathematical modelling of the development of combustion dynamics at thermo-chemical conversion of biomass mixtures (straw pellets with crashed coal) with the aim to better understand the effect of electric field on the formation of the main gasification/ combustion characteristics when co-combusting straw with crashed coal. The experimental study and numerical modelling of the electric field effects on the combustion dynamics, when co-combusting straw pellets with coal, were carried out to ensure wider use of straw as a fuel for energy production providing the electrodynamic process control. The mathematical model considers the electric field influence on the combustion characteristics using the approximation of 2D axially symmetric compressible swirling flow and chemical reactions with account of the development of A→B↔C kinetics (A -reactant, B -intermediate product, C -final product) downstream the cylindrical combustor.Keywords: biomass pellets, electric field, chemical reactions, mathematical model. IntroductionThe electric field effect on diffusion and premixed flames attract attention as a tool, which allows to control the flame shape, structure and the main flame characteristics, such as the flow velocity, flame temperature, composition, equivalence ratio and products composition [1][2][3][4][5][6]. There are different mechanisms of the electric field effect on the main flame characteristics. First, at high current density, the electric field effect on the flame can be related to the flame heating, with an additional heat input into the flame (plasma support of combustion). Next, the electric body forceinduces an ion drift motion in the field direction.Inelastic collisions between the flame ions and the neutral flame species can then cause the ion wind effect promoting the interrelated processes of field-enhanced heat and mass transfer in the field direction. This can cause variations of the thermal decomposition of solid fuels and the combustion of volatiles. In addition, the electric field-induced inelastic collisions between the electrons and the flame species can cause variations of the rate of reactions. Finally, the flame dynamics can be controlled using the Lorentz force, when the electric field-induced current in the flame reaction zone creates a field-induced magnetic field with axial and radial components of the electromagnetic force, which influence the evolution of flow dynamics and flow vorticity [7]. Thus, multiple factors can influence the development of combustion dynamics, when the electric field is applied to the flame. In order to obtain predictable and controllable field effect on the main flame characteristics, one can vary such parameters as the electric field polarity, bias voltage and current density between the electrodes.More precise and systematic studies of the electric field effect on the combustion dynamics for different types of flames (diffusion, swirling, etc.) and fuels (gaseous, solid and their mixtures)...
Experimental studies and mathematical modelling of the effects of magnetic field on combustion dynamics at thermo-chemical conversion of biomass are carried out with the aim of providing control of the processes developing in the reaction zone of swirling flame. The joint research of the magnetic field effect on the combustion dynamics includes the estimation of this effect on the formation of the swirling flame dynamics, flame temperature and composition, providing analysis of the magnetic field effects on the flame characteristics. The results of experiments have shown that the magnetic field exerts the influence on the flow velocity components by enhancing a swirl motion in the flame reaction zone with swirl-enhanced mixing of the axial flow of volatiles with cold air swirl, by cooling the flame reaction zone and by limiting the thermo-chemical conversion of volatiles. Mathematical modelling of magnetic field effect on the formation of the flame dynamics confirms that the electromagnetic force, which is induced by the electric current surrounding the flame, leads to field-enhanced increase of flow vorticity by enhancing mixing of the reactants. The magnetic field effect on the flame temperature and rate of reactions leads to conclusion that field-enhanced increase of the flow vorticity results in flame cooling by limiting the chemical conversion of the reactants.
The recent research is focused on the experimental study and mathematical modelling of the development of combustion dynamics at thermo-chemical conversion of biomass mixtures (straw with wood pellets) with the aim to better understand the effect of straw co-combustion with wood pellets on the formation of the main gasification/ combustion characteristics. The results of experimental study have shown that thermal interaction between the components at co-combustion of straw with wood pellets at average mass load of straw in the mixture up to 20-30 % promotes faster thermal decomposition of the mixtures and accelerates the flaming combustion of volatiles. The mathematical model considers development of two second order exothermic irreversible chemical reactions at chemical conversion of combustible volatiles (H 2 , CO) to assess their influence on the development of the combustion dynamics downstream the reacting swirling flame flow. The results of mathematical modelling have shown that, in accordance with the data of the experimental study, the maximal values of the flame temperature, axial flow velocity and the mass fractions of the main products (CO 2 , H 2 O) at the thermo-chemical conversion of the biomass pellets and their mixtures were obtained at 20-30 % of the mass load of straw in the mixture, which is recommended as optimal composition of the mixture.
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