二段燃焼用空気ノズル形状が及ぼす燃焼性能への影響評価(熱工学,内燃機関,動力など)

概要

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We examined relations between the shape of the staged air nozzle (after air port) and the mixing performance in the furnace for two staged combustion. Four different shapes of ports, 1 hole, 4 holes, 9 holes, Lobe shape, with the same open area of nozzle outlet were used to examine the effect on the NO_x and CO performance. The gas velocity in the furnace and the air ratio were fixed at the values near the operating condition of the actual boilers as much as possible. NO_x and CO performance was correlated with the mixing performance in the downstream side of the after air port. CO decrease when the standard deviation of the local air ratio in the furnace become small. This is because extremely low oxygen concentration region is hard to be formed in the furnace. On the other hand, NO_x increase if the standard deviation of that is small. The overall air ratio was set at 1.15 for the experimental condition. Under this condition, improvement of mixing performance brings an increase of thermal NO_x because of higher gas temperature. We also examined the nozzle design criteria in order to predict its mixing performance beforehand. It was found that the circumference length of the jet flow had a good correlation with the standard deviation of the local air ratio. When a nozzle has a longer circumference length, mixing performance of it becomes better.
2010-01-25