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.

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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.

Abstract. The focus of this study is to investigate the main factors determining the development of swirling flow dynamics and to correlate the development of the non-premixed swirling flame characteristics at biomass thermo-chemical conversion with the evolution of the confined swirling flow velocity fields in a pilot device which combines a biomass gasifier and a combustor. This study includes complex experimental study and numerical modelling of the development of velocity fields for confined non-reacting swirling flows and flame, as well as the development of swirling flame velocity fields and combustion characteristics at biomass thermochemical conversion under effects of various inlet conditions, such as the inlet nozzle diameter at the bottom of the combustor, primary and swirling air supply rates in the device. The results show that the development of the swirling flow velocity field first of all is closely related to the inlet nozzle diameter, which for the fixed primary and secondary air supply rates strongly affects the upstream and downstream swirling airflow formation and swirl intensity, which are highly responsible for the mixing of combustible volatiles with the axial air flow, for the ignition and combustion of volatiles. The results also show that the development of the swirling flow velocity field depends on the air supply rate which affects the development of the combustion dynamics and composition of emission through the variation of the downstream flow structure and the air excess ratio in the flame reaction zone.Keywords: swirling flows, biomass pellets, combustion dynamics, mathematical model. IntroductionThe application of swirling flows for the design of combustion systems is important due to the swirl-induced formation of a toroidal recirculation zone, which results in enhanced mixing of a fuel with the air, in stabilization of combustion dynamics and in greater combustion efficiency. The comprehensive research of the confined swirling flows includes an experimental study and a numerical analysis of the development of the downstream flow structure and combustion dynamics by varying the flow geometry, boundary conditions and swirl intensity [1][2][3][4][5]. These studies have shown that relatively small variations of the inlet conditions and configuration of the swirl combustor can result in unpredictable variations of the flow patterns and main flame characteristics. Moreover, the complex research of the swirling non-reacting flow and flame dynamics in a cylindrical channel has revealed that the development of swirling flow patterns and flame structure correlate with the formation of downstream and upstream swirling air flows which are responsible for biomass gasification, mixing of the axial flow of volatiles with the air, ignition and combustion of volatiles and for the formation of main combustion characteristics [6]. Further research has shown that the formation of the downstream and upstream swirling flow patterns and swirling flame structure is highly sensitive to the variations ...

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Abstract.A series of experimental studies and mathematical simulations of the electric field influence on the thermal decomposition of mixtures of wheat straw with wood and peat pellets and on the development of volatile combustion downstream the swirling flame flow was carried out. The main aim of these studies is to provide more efficient use of straw for cleaner and more efficient energy production by improving the gasification/combustion characteristics of the mixture and the composition of emission. The electric field influence on the combustion dynamics was studied experimentally using a pilot device, which combines a biomass gasifier and a combustor. An electric field was applied to the flame base using an axially inserted electrode. The electric field effect on the main gasification/combustion characteristics of a biomass mixture was estimated through complex measurements of the field-induced variations of the flow velocity, flame temperature, composition and heat output by varying the positive bias voltage of the axially inserted electrode. The mathematical model of the combustion process considers the electric field influence on the combustion characteristics using the approach of single chemical reaction. Simulations were performed for the opposite field configuration, when the negative bias voltage was applied to the axially inserted electrode by varying its length.