پيمان مقصودي كلاردشتي

Intermittency production, geographical dependence and storage capability associated with renewable energies and environmental pollution and global warming through the limited sources of fossil fuels lead to investigate the metals as alternative energy sources. In this thesis, by considering magnesium as energy carrier, its combustion behavior is examined. By proposing a comprehensive multi-step model, the combustion of single magnesium particle in O2-He, O2-Ar and O2-N2 is scrutinized. In this model, the heterogeneous and homogeneous combustions are examined by considering four distinct stages of combustion of solid magnesium, melting of solid magnesium simultaneously with combustion of liquid magnesium, combustion of droplet and gas phase. Then, dynamic behavior of a falling porous magnesium particle over combustion process is eva‎luated with the aid of numerical solution and optimization of multi-layer perceptron neural network. Afterwards, the premixed combustion of magnesium dust cloud is studied by presenting a multi-zone asymptotic flame structure and three different models. The considered flame structure consists of four zones including preheat, post-melting, post-vaporization and post-flame and three asymptotic fronts of melting, vaporization and flame. The three models are classified according to the presence or absence of effects of thermal and dynamic equilibrium, combustor heat loss, inter-regional radiation, variable properties, thermophoresis and Brownie. Finally, with the help of the proposed models, the trajectory of magnesium and magnesium oxide particles is determined and the flame oscillations are eva‎luated by applying external perturbation to the velocity field. For oxygen mass fractions greater than 0.35, the burning time and lean flammability limit (LFL) of He-O2 are greater than those of Ar-O2. The increase in the ambient temperature from 300 to 800 K declines the LFL from 0.16 to 0.03; at 900 K, the flame gets stable and has no extinction. By changing the inert gas of the medium from nitrogen to helium, the amplitude of temperature and mass fraction fluctuations reduce by 13.3 and 16.75 times, respectively.

منيزيم , ابر ذرات , احتراق پيش آميخته , رديابي , نوسان , حد رقيق اشتعال

magnesium , Dust Cloud , premixed combustion , trajectory , oscillation , Lean Flammability Limit

Peiman Maghsoodi

Dr. Bidabadi