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In this study, characteristics of the miniature vortex combustion power system were investigated with methane, propane, n-butane and i-butane / air mixtures. The system output and CO emission were examined under various equivalence ratio conditions. The experimental results for thermal input of 600W showed that the output of methane attained 20.0W (11.89V × 1.69A) for stoichiometric condition, which is evidently higher than other fuels, 18.1W for propane, 18.6W for n-butane and 18.0W with i-butane. Furthermore, the difference of the output power among those fuels became larger with decreasing the equibalance ratio, that is, the output power of propane, n-butane and i-butane drastically decreased in fuel lean condition, Φ < 0.9. As the exhaust gas temperature showed monotonical increase with the decrease in Φ, the exhaust energy was found to be increased with the reduction of Φ. However, it was found that further energy was lost by incomplete combustion in fuel lean conditions of propane, n-butane and i-butane. For those fuels, the flame become unstable and large amount of CO was emitted for Φ < 0.9 while the output of 16.0W was maintained for methane even at Φ = 0.8. According to the flame appearance obtained by quartz combustor, it was clearly observed that the flame luminosity around the flame base was weakened for propane and butane in fuel lean conditions. As such weakening was not observed for methane, it is considered that the Lewis number effects may contribute to the weakening of propane and butane flame base, and thus, drastic decrease of the thermal input in fuel lean conditions of propane and butane. |
