| 摘要 |
PURPOSE:To reduce a load of a forced draft fan by a method wherein an amount of requisite air is calculated in response to the number of burners for each of stages, a distribution damper for the state having the maximum amount of requisite air is fully opened and a degree of opening of a distribution damper for the remaining stages is controlled to be equal to a required amount of air for each of the stages. CONSTITUTION:A high-selector 17 selected the maximum value of a set value SV in a damper degree adjusting meter for each of the stages to be as S0. A comparator 18 may compare S0 with a set value of a self-stage and if SV=S0, a comparison output COM is transmitted. A changing-over means 19 selects an output MH' of a variation rate limiter 21 when a comparison output COM is given so as to limit a degree of opening of a distribution damper to its maximum value. A degree of opening of the distribution damper in the stage of maximum air requisite amount becomes maximum, thereby a pressure at an inlet part of each of the distribution dampers is decreased and a degree of opening of the damper for other stage is controlled in its full-opened direction in order to keep a set flow rate. Therefore, a load on the forced draft fan 6 is reduced. |
