回転管状火炎における水素添加による希薄燃焼の改善 : 燃焼ガス温度および燃焼ガス組成(熱工学,内燃機関,動力など)
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An Improvement of Lean Combustion Characteristics with Hydrogen Addition in a Rotating Tubular Flame : Burned Gas Temperature and Burned Gas Composition
Burned Gas Temperature
Burned Gas Composition
Rotating Tubular Flame
A rotating tubular flame has received considerable attention in combustion research because it experiences flame curvature and flame stretch simultaneously. It is also interesting to note that the rotating tubular flame is very stable, and hence, addition of small amount of hydrogen enables lean combustion of heavy hydrocarbon fuels with this flame. In our previous report, it has been found that hydrogen addition of 3% by volume enables lean combustion up to the effective equivalence ratio of 0.1 for methane, and up to the ratio of 0.2 for propane flame. In this experiment, probing of the burned gas temperature and the burned gas composition were made. The results show that in the cases when hydrogen is added by 1, 2, and 3% by volume to methane/air mixture, and by 3% by volume to propane/air mixture, the burned gas temperature exceeds the temperature obtained by chemical equilibrium calculation (CEC) in some low fuel concentration ranges. In these ranges, the oxygen concentration in the burned gas becomes lower than that of CEC, while the water concentration exceeds that of CEC. These facts substantiate the validity of the previously postulated mechanism for extension of lean combustion that due to the effects of flame curvature and flame stretch, hydrogen preferentially diffuses across stream tube from the upstream, unburned gas side into the reaction zone, resulting in an increase of gas temperature and also of water concentration; then lean combustion is achieved.