Flame stabilization and emission of small Swiss-roll combustors as heaters

The characteristics of small Swiss-roll combustors were investigated experimentally in detail. Three types of Swiss-roll combustors of different designs and two cases of heat transfer conditions were studied. The effects of design parameters on the performance of these combustors were examined. Each combustor consisted of a combustion region at the center (called the combustion room) and double spiral-shaped channels, the widths of which were smaller than the minimum quenching distance of a propane premixed flame at a normal state. Flames could be stabilized successfully for a wide range of equivalence ratios and mean velocities by using the recirculated heat from the burned gas, and blow-off was not observed. Temperature distributions of the combustors, variation of gas temperature, and the concentrations of the exhaust gas from the combustors were also investigated. Mean temperatures of the combustors were found to be governed by both the radiant heat loss from the combustors and the total chemical energy liberated by the combustors. Efficiencies of the combustors as heaters were evaluated. As a combustor became smaller, its thermal efficiency as a heater increased and its NO_x emission decreased, while the emission of CO increased. By adding a catalytic reactor at the exhaust port, it was found that the emission of CO could be eliminated. This study provides new experimental results for a small Swiss-roll combustor, which represents an essential step toward the development of a microcombustor.