Document Type : Article
School of Mechanical Engineering, Department of Energy Conversion, Iran University of Science and Technology (IUST), Narmak, Tehran, 16846-13114, Iran.
In this work, a comprehensive mathematical method is developed to model the flame propagation through organic particles with air as a two-phase mixture, considering random distribution and particles thermal resistance. For this purpose, the structure of flame contains a preheat-vaporization zone, a reaction zone where vaporization and convection rates of particles are negligible and a post flame zone where diffusive terms are negligible in comparison of other terms zone. In order to enhance the combustion efficiency, the exhausted heat from the post flame zone is recirculated back to the preheat zone. Since this stream consists of high temperature gaseous mixture, it can enhance the temperature of the initial two-phase mixture entering the combustion chamber. The obtained results show great compatibility with the experimental findings. Apart from the randomness distribution of particles and heat recirculation phenomena, the effect of thermal resistance on the combustion properties such as flame temperature and burning velocity is studied through non-zero Biot numbers in this model. Additionally, the variation of several parameters including equivalence ratio, particle diameter and Lewis number are studied in this research.