WITHDRAWN: Mathematical modeling of homogeneous combustion processes in small spaces

Abstract

While flame propagation at the micro-scale is feasible, the interplay of kinetics and transport in flame stability and combustion characteristics is poorly understood. The inability of conducting spatially resolved measurements, inherent to the micro-scale, underscores the need for detailed mathematical modeling. This study relates to the mathematical modeling of homogeneous combustion processes in small spaces. Computational fluid dynamics simulations are conducted to gain insights into burner performance such as temperatures, reaction rates, and flames. The factors affecting combustion characteristics are determined for the cavity-stabilized burner. A dimensionless number analysis is performed to better understand the heat transfer characteristics of the burner. Particular focus is placed on determining essential factors that affect the performance of the cavity-stabilized burner. The results indicate that the near-entrance heat loss and radical quenching at the wall are key issues in controlling flame propagation in microchannels. In very small spaces, radial gradients and temperature discontinuity at the wall are negligible but become significant as the length scale is increased. Large transverse and axial gradients are observed even at these small scales under certain conditions. It is necessary to overcome both thermal quenching and chemical quenching of the flame. Thermal quenching is the loss of energy generated by combustion through heat transfer out of the combustion region. Chemical quenching is a barrier to combustion at millimetric dimensions. Chemical quenching occurs when the reactive species is removed by reaction with the material forming the wall surfaces. The wall thermal conductivity and inlet velocity are vital in determining the flame stability of the burner. Further improvement in flame stability can be achieved by using anisotropic walls. Fast flows can cause blowout and slow flows can cause extinction. There exists an optimum inlet velocity for greatest flame stability.