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In this paper the coupled lattice Boltzmann model is developed for simulation of multi-step combustion mechanism of a methane jet diffusion flame. The lattice Boltzmann scheme employs the double-distribution-function model, one distribution function for solving flow field and another for temperature and species concentration fields. The density and temperature fields are coupled through low Mach number flow field. The solution parameters such as species properties and rate of chemical reactions adjust in every time step according to temperature and concentration of species variations. Using combustion mechanisms instead of one step fast chemistry reaction and considering effect of temperature and species concentration on solution parameters are the main advantages of the developed model. For validation of the model, a four-step reduced mechanism with six species is used for simulation of combustion in a methane jet diffusion flame configuration. Agreement between the present results and experimental data confirms that this scheme is also an efficient numerical method for more detailed combustion simulations.

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The particles and atoms of carbon significantly affect radiation heat transfer and combustion behavior of flames. Number of carbon particles within the flame is increased by utilizing fuel with higher C/H mass ratio or adding carbon particles into lighter liquid fuel. In this study, the effect of adding various concentrations of multi-walled carbon nanotubes with hydroxyl functional group into hydrocarbon liquid fuel has been measured on temperature distribution and thermal radiation of the flame. Furthermore, the measured results compared with results of combustion behavior of liquid fuels with higher C/H value. The thermopile sensor and the lux meter were utilized to measure the flame thermal radiation (visible and infrared spectrum) and luminosity (visible wavelengths). Thermography technic and IR image were applied to determine the distribution of temperature and soot within the flame. The results showed that adding nanoparticles into liquid fuel increased the rate of chemical reaction kinetics, temperature and thermal radiation and decreased flame length. In addition, a rise in value of C/H of the liquid fuel increased temperature, flame length and thermal radiation and reduced the rate of chemical reaction kinetics. By adding 0.01% mass fraction of nanoparticles into the base fuel with C/H=5.46, thermal radiation increased by 3.4% as same as liquid fuel with C/H=5.52. The increase of nanoparticle concentrations increased the rate of chemical reaction kinetics, maximum temperature, thermal radiation and luminosity. In addition, the position of maximum temperature moved closer to the burner.