| 摘要 |
PROBLEM TO BE SOLVED: To make a flame rod not detect a flame in a stage that oxygen is in deficiency without increasing a supply amount of secondary air, in a combustion device which comprises, at its upper end, a plurality of rich-lean burners 3 in a combustion box each having: a lean flame hole 31 for injecting a lean air-fuel mixture which is leaner in fuel concentration than a logic air-fuel ratio, and longitudinal in the fore-and-aft direction; blind air spaces 32 which are located at both sides of the lean flame hole in cross direction, and from which an air-fuel mixture is not injected; and rich flame holes 33 which are located outside in cross direction of the blind spaces, and inject rich air-fuel mixtures which are richer in fuel concentration than the lean air-fuel mixture, and also comprising the flame rod 7 opposed to the upper part of a prescribed rich-lean burner.SOLUTION: The prescribed rich-lean burner 3 opposed with the flame rod 7 has a width-narrowed part 32a which is narrowed in lateral width more than other portions of the blind spaces 32 in a portion of the blind space 32 which is positioned immediately below the flame rod 7. |
