| 摘要 |
PURPOSE:To enable increasing of the throttle ratio of a combustion amount at low NOx, by a method wherein, in the 2-stage combustion device for indoor open type burner for household use of a stove fan heater and a small water heater, a burner port, such as wire nets, foaming metals, having a small heat capacity, is used in a main burner port, and a burner port load and a primary air ratio are set to a sepecified range. CONSTITUTION:A wire net, being low in heat capacity, is used in a main burner port 6, and a burner port load is set to less than 1kcal/hrmm.<2>. Since the main burner port 6 has a burner port load of less than 1kcal/hrmm.<2>, lift is prevented from occurring even in a primary air ratio of 100% or more to perform excellent combustion. Further, since 2-stage combustion is effected, an effect, being efficient enough to allow combustion of a device even at a primary air ratio range of 50-70%, is produced, combustion can be effected up to the whole primary - the whole secondary. The injection speed of air-fuel mixture is decreased to 1/3-1/6 or less that of a conventional type, and since combustion reaction is quick and a flame is decreased in length, and the height of a combustion chamber 7 can be decreased, resulting in the possibility to form a compact 2-stage combustion device. Further, since heat capacity is low, NOx is maintained at about 10ppm even at a primary air ratio of about 50%, and a lift limit is throttled to 1/3. Finally, in a range where a combustion amount is high, reduction is gradually effected from a primary air ratio of 110%, and this causes reduction of a lift limit from the main burner port 6, and enables a throttle to be throttled to a low combustion range and can be reduced to 1/6.
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