Developments in Combustion Technology

Kyprianidis, Konstantinos; Škvařil, Jan

doi:10.5772/61418

Cited by 10 publications

(19 citation statements)

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“…As the first approximation, t int can be considered the ignition temperature of the combustible mixture. When t int increases, the temperature difference θ int decreases and the required time τ int increases; according to the results of [24], the drying time of the fuel particle can be ignored. The gradual start of the fuel particles into the heat transfer processes in the flame and the additive dependence of the total heat content are defined by the integral of the distribution function of the deviation probability (3), and it is rational to set the integration limits from minus ∞ to the maximum fuel particle size δ max corresponding to the upper limit of integration U…”

Section: Adapting the Model To Flame Characteristicsmentioning

confidence: 99%

“…If we assume that the interaction pattern of a burning fuel particle with the furnace atmosphere [23,24] has a surface model, which corresponds to a plane diffusion layer between a spherical particle and the furnace atmosphere, the burnout rate of the particle can be determined at G c = const according to the equation dδ/dτ = −2M c G c /ρ, where M c = 12 kg/kmol is the molar mass of carbon, ρ ≈ 800 kg/m 3 is the density of coke. The flow of burnable carbon in the flat diffusion layer, the most common model layer in simulation of moving burning particles of coal dust is assumed to be a constant to simplify the calculations, which does not contradict the actual conditions of combustion, because the boiler unit in a certain mode for a long time period supply a fuel-air mixture constant, and the fractional composition is determined by the operation of the mill devices and also with a certain mode of operation the boiler unit remains virtually unchanged.…”

Section: Adapting the Model To Flame Characteristicsmentioning

confidence: 99%

“…To take into account the polydispersity of the medium in the flame continuum, we need to apply the dependence for the single-particle burnout function associated with the local value of the kinetic and diffusive characteristics of the process. As a first approximation, we can neglect the effect of CO burning within the boundary layer, the reducing reactions, and the internal response [23,24]. Then, a one-dimensional model of the combustion process of the first-order oxygen reaction, with oxygen being insufficient, has the dependence for the burnable carbon flux G c : G c = ωC ox , where ω is the kineticity parameter of the fuel burnout process, determined in accordance with Kirchhoff's second electrical rule for a parallel circuit of two conduction bands.…”

Section: Adapting the Model To Flame Characteristicsmentioning

confidence: 99%

“…The oxygen content according to (13) ensures the local burnout of the fuel particle with the initial size δ i with respect to this dependence without taking into account the variability of the variability of the kinetic factor [23,24] dδ…”

Section: Dynamics Of Particle Combustionmentioning

confidence: 99%

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New Theoretical and Methodological Approaches to the Study of Heat Transfer in Coal Dust Combustion

2019

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The existing theories of heat transfer in combustion chambers of boiler units fail to take into account a number of important factors that affect the reliability of results, and the methodological approaches to optimizing combustion processes can be revised in view of the spatial and temporal parameters of flame. Hence, the research aimed to improve the fundamental theoretical and methodological principles of studying heat transfer in coal dust combustion in the combustion chambers of industrial steam generators. The authors proposed to extend the theory of heat transfer with the mathematical description of particle size distribution of coal dust. In addition, the authors used the developed mathematical model of coal dust combustion based on a continuous curve of the particle size distribution in the ensemble. The mathematical model is consistent with the aeromechanical and thermal characteristics of flame. This work introduced a concept of flame continuum as a continuous medium, where the processes of combustion and heat transfer are studied. To achieve the research aim, in this paper, the methods of combustion chamber zoning, the equations of stationary and non-stationary heat conduction, radiation, and convective heat transfer, were used. These methods were tested on a number of high-temperature units.

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Section: Adapting the Model To Flame Characteristicsmentioning

confidence: 99%

Section: Adapting the Model To Flame Characteristicsmentioning

confidence: 99%

Section: Adapting the Model To Flame Characteristicsmentioning

confidence: 99%

Section: Dynamics Of Particle Combustionmentioning

confidence: 99%

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New Theoretical and Methodological Approaches to the Study of Heat Transfer in Coal Dust Combustion

2019

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“…The disadvantage of all these works is the consideration of reagents as separate structural parts of the combustion medium, which leads to particular methods [10]. In the theory of heat transfer, a new unified methodology is needed based on a mathematical model that includes the design features of the boiler, the torch continuum as an indivisible whole, and the continuous function of the fractional residue.…”

Section: Introductionmentioning

confidence: 99%

Analysis of the calculated and experimental dependencies of the combustion of coal dust on the basis of a new methodological base of theoretical studies of heat exchange processes

Toropov¹,

Осинцев²,

Aliukov³

2018

IJHT

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The methodology of theoretical studies of heat exchange processes in boiler units based on the mathematical model of burning coal dust has been developed. For the first time, the continuous curve of the fractional composition of an ensemble of coal particles is presented. The mathematical model is consistent with the aeromechanical and thermal characteristics of the torch, obtained on the basis of calculated and experimental data. The concept of a torch continuum is introduced as a continuous medium in which the processes of combustion and heat exchange are investigated. The methods of dividing the combustion chamber into zones, the equations of stationary and non-stationary heat conduction, radiation and convective heat exchange are used. These methods have been tested on a number of high-temperature installations, including boilers with natural circulation, for example, E-220 at the CHP plant in Bishkek, Kyrgyz Republic in the Central Asian region. In the course of the experiments, coals with different thermal characteristics were burned. In a special computer program obtained a 3D image of burning coal dust. Analysis of the calculated and experimental data showed a discrepancy between them of 4-5%. Analysis of computer simulation data showed a discrepancy with the calculated data of 3-4%, and with experimental 5-6%. Thus, the dependence of the parameters of the heterogeneous flame on the mathematical description of the fractional composition of coal dust is substantiated and the characteristics of the combustion process, previously not taken into account in the theory of heat transfer, are revealed. The task was solved-theoretically confirmed new methodological approaches to the theory of heat transfer in the furnace of the boiler unit.

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1D modeling of SI engine using n-butanol as fuel: Adjust of fuel properties and comparison between measurements and simulation

Trindade

Santos

2018

Energy Conversion and Management

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Developments in Combustion Technology

Cited by 10 publications

References 0 publications

New Theoretical and Methodological Approaches to the Study of Heat Transfer in Coal Dust Combustion

New Theoretical and Methodological Approaches to the Study of Heat Transfer in Coal Dust Combustion

Analysis of the calculated and experimental dependencies of the combustion of coal dust on the basis of a new methodological base of theoretical studies of heat exchange processes

1D modeling of SI engine using n-butanol as fuel: Adjust of fuel properties and comparison between measurements and simulation

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