Combustion Characteristics and Stability of Methane-Air Mixtures in Catalytic Microreactors

Abstract

Combustion characteristics and stability of premixed methane-air mixtures in catalytic microreactors are studied numerically, using a two-dimensional computational fluid dynamics model with detailed chemistry and multicomponent transport. In order to understand how to design microreactors with enhanced stability and robustness, the reaction and transport of methane-air mixtures are studied, and the role of operating conditions is evaluated. The primary focus is on computational fluid dynamics as a means of understanding energy management at small scales. It is shown that an appropriate choice of the flow velocity is crucial in achieving the self-sustained operation. Large gradients in temperature and species concentration are observed, despite the small scales of the system. The flow velocity plays a dual, competing role in flame stability. Low flow velocities reduce the heat generation, whereas high flow velocities reduce the convective time-scale. There is a narrow regime of flow velocities that allows self-sustained operation. When a low-power system is desired, highly insulating materials should be preferred, whereas a high-power system would favor highly conductive materials. Engineering maps are constructed, and design recommendations are finally made.