| 摘要 |
<p>PURPOSE:To reduce the nitrogen oxide emission while the noise is suppressed by providing between a discharged-gas passageway and a fan a connection pipe whose end is positioned at the fan opens inside the casing of the fan. CONSTITUTION:Air and fuel supplied undergo combustion by the use of a burner 11 inside a combustion chamber 13; water is heated in a heat exchanger 14, passed through a hot-water-outlet pipe 19, and supplied. With revolution of a fan 10, a negative pressure develops in the space near the air inlet 23 of the fan so that discharged gas in a discharged-gas hood 15 flows through a connection pipe 21 into the fan 10, is mixed evenly with fresh air for combustion inside the casing 22 and fed back to the burner 11. Inactive gas and steam contained in large quantities in the discharged gas slacken the combustion and lowers the temperature of the flames so that the generation of nitrogen oxides is suppressed. By controlling the tubular diameter of the connecting pipe 21 and the excess air ratio appropriately the generation of nitrogen oxides can be considerably reduced and simultaneously the noise can be withheld from increasing.</p> |
