Numerical modeling of non-premixed combustion of micron-sized Ti particles in counter-flow arrangement: The effects of heat losses

Abstract

In this study, a numerical model was introduced for simulation of preparation of TiO2 by non-premixed combustion of Ti particles in counter-flow arrangement. Preheating, reaction, melting, and vaporization processes were modeled using the asymptotic concept. To reach a viable model, convective and radiative heat losses were included in the model derivation. The conservation equations for mass and energy were presented in each zone with the heat loss terms. Boundary and jump conditions were employed to solve the governing equations to preserve continuity throughout the system. The numerical modeling was first validated against literature data, where good agreement was achieved. Then, the focus of results and discussion were given to the influence of heat loss terms on the spatial distributions of temperature and species mass fractions. It was clearly shown in that heat losses can significantly shorten the distances between the stagnation plane and flame fronts. This is the also the case for melting and vaporization fronts. However, the heat losses can obviously suppress thermophoretic force. Finally, the effects of initial fuel temperature on positions of flame, melting, and vaporization fronts, where almost linear dependences were found that higher initial fuel temperature results in closer fronts to the stagnation plane.