Effect of a catalytic segment on flame stability in a micro combustor with controlled wall temperature profile

In the present study, the stability of methane/air flames in a micro cylindrical channel with a prescribed wall temperature profile and a platinum (Pt) segment was investigated numerically. Two dimensional simulation was performed by the commonly used computational fluid dynamics software Fluent 6.3, incorporated with detailed gas combustion chemistry GRI 3.0 and catalytic reaction mechanism of methane/air on platinum. The results demonstrate that all the unstable flames become stationary in the presence of a 3-mm Pt segment located at x = 49-52 mm (total length of 80 mm) on the wall surface, and the response of flame position to inlet velocity exhibits an S-shaped curve. Detailed analysis was conducted to reveal the underlying mechanisms responsible for the existences of two turning points, which showed that the catalytic segment exerts a negative influence on homogeneous combustion at high and medium velocities, whereas it can enhance the homogeneous combustion at low velocities. In summary, the present study revealed the complicated effects of heterogeneous reaction on homogeneous combustion and suggested an effective and economic method to suppress flame instabilities in micro combustors.