| 摘要 |
PURPOSE:To contrive to make the turn-down ratio of a burner larger, by providing a controlling device which controls to operate an air flow rate changing means when a fan reaches its maximum number of revolution, as well as to control the number of revolution of a fan to reach another maximum value. CONSTITUTION:At the time of maximum input, combustion takes place nearly at the yellow limit, with a damper 10 open, and a fan being operated at its maximum number of revolutions. The number of revolution is gradually decreased in accordance with the decrease of input, and at the lower limit, combustion takes place nearly at the limit of a lift. When the input is lowered further, the number of revolution is increased to the upper limit, with the damper 10 closed, and a combustion is started again from the yellow limit. The number of revolution is decreased in accordance with the input, and the combustion rate is lowered down to the limit of a lift. When the input is to be lowered further, a valve 8 to control the number of burner pipes 9 is closed to decrease the number from 7 pipes to 3, and the 3 pipes perform the same operation as that of 7 pipes. In such a manner the variable range of the number of revolution can be effectively used, and the turn-down ratio per burner can be made wide. |
