Thermophoresis effect on volatile particle concentration in micro-organic dust flame

In this paper, a mathematical model is proposed for the study of the structure of an upward-propagating flame that contains uniformly distributed volatile fuel particles in an oxidizing gas mixture. In order to obtain an appropriate model, the flameʹs front zone (the unburned zone) is divided into two zones: preheat and vaporization. In this research, physical phenomena such as thermophoretic effect, vaporization process and particle radius changes have been studied in the two mentioned zones. The vaporization process across the flame front leads to particle radius reduction, which can affect the particlesʹ hydrodynamic behavior. As the thermophoretic force progressively increases by approaching the flame, it reaches a critical magnitude that just balances the gravity and buoyancy forces of the particles. At this point, the particle cloud remains stationary where the particles accumulate, and as a result, the volume fraction of particles reaches its maximum value. Particle size can strongly affect the hydrodynamic behavior of dust, and it can be stated that the increase of the radius of particles could lead to the reduction of the distance between the stagnation point (where the particle volume fraction is maximum) and the flame. The theoretical results show reasonable correlation with the experimental data.