چكيده به لاتين
Due to the structure of non-premixed combustion, in which fuel and oxidizer are separately injected into the combustion system, safety and controllability can be noticeably enhanced. In this thesis, different comprehensive analytical models are proposed to investigate the combustion behavior of several micron-sized organic and inorganic fuels in non-premixed mode and counter-flow configuration under adiabatic and non-adiabatic conditions. Furthermore, trajectory of particles and effect of an oscillatory heat source on the structure of the non-premixed flames are presented. It should be noted that an asymptotic method is employed to analyze the non-premixed flames. In this study, lycopodium particles (organic fuel), coal particles (fossil fuel), and iron particles (metal fuel) are considered as the fuels. For lycopodium non-premixed combustion, preheating, drying, vaporization, reaction (homogeneous reaction) and oxidizer zones are studied. For coal non-premixed combustion, preheating, drying, pyrolysis, reaction (both homogeneous and heterogeneous reactions) and oxidizer zones are presented. It is worth mentioning that char, gas and ash are produced during the pyrolysis process. For metal combustion, preheating, reaction, melting and vaporization processes are analyzed. In order to mathematically study the combustion systems, mass, energy and momentum balance equations in steady and unsteady forms are obtained in each of the considered zones and solved by Matlab and Mathematica software using proper boundary and initial conditions. To make the models more reliable, influences of particle porosity, gravity force, buoyancy force, drag force, thermophoretic force and thermal-diffusive oscillations caused by an external oscillatory heat source on the structure of the non-premixed flames are included. In order to examine the performance of the system under non-adiabatic conditions, radiative and convective heat losses are involved. To preserve the continuity in the system, reasonable matching conditions are derived. Eventually, temperature and mass distributions of fuels, products and oxidizer are obtained in each of the zones. In addition, the influences of fuel and oxidizer Lewis numbers, particle size, particle porosity and equivalence ratio on the temperature and mass distributions, critical flow strain rate, flame temperature and flame front position are discussed. For validation purposes, results of the current analytical investigation are meticulously validated by the numerical and experimental results of former relevant studies on lycopodium, titanium and iron particles under the same conditions. Based on the comparisons, there are proper compatibilities between the results of the present study on counter-flow non-premixed combustion of micron-sized particles and those of prior results.
