Optimization of a miniature tubular combustor filled with a T-shaped porous zone for flame stability enhancement

There exist urgent demands for miniature combustion-based power devices due to their high energy densities. We recently integrated a T-shaped porous zone into a meso-scale combustor with an inner radius (R) of 3 mm. Numerical simulation demonstrated that this new configuration harvested a maximum flame blow-off limit of 1.05 m/s for stoichiometric C₄H₁₀/air mixtures, which is almost twice of the counterpart (0.55 m/s) of original combustor with cylindrical porous media. In the present study, further optimization of this combustor was performed by varying the protruding part radius (r) of the T-shaped porous zone. The findings indicate that as r rises from 0.5 to 2.0 mm, flame blow-off limit keeps increasing to 1.65 m/s, whereas flame cannot be stabilized in the combustor when r = 2.5 mm. Analysis demonstrates that when r = 2.5 mm, flow resistance in the annular space increases drastically and the portion of gaseous mixture that passes through the protruding part increased sharply. Consequently, the low-velocity zone cannot be formed any longer and flame cannot be anchored. Moreover, the heat recirculation efficiency still increases with an increasing r. Therefore, the largest blow-off limit is achieved at r = 2.0 mm.