| 摘要 |
PURPOSE:To prevent rapid downward expansion of the lower limit curve of unevenness of an air ratio at a low combustion range, by a method wherein throttle parts are positioned on a fuel gas path and an air path for combustion, and either a gas amount control valve or a feed means for the air for combustion, which are located on the upstream side thereof, is controlled. CONSTITUTION:Resistance of a gas throttle part 1 and resistance of an air throttle part 2 are determined so that the value of a pressure drop (Pg-Pm), produced by the gas throttle part 1 and the air throttle part 2, and the value of Pa-Pm establish a formula of Pg=Pa when value of an air ratio (m) is the value of B at a maximum rating time. If control is made so that Pg becomes equal to Pa, the air ratio (m) is controlled so that it becomes approximately constant at a range except a low combustion range. In a condition that a varying throttle 2C is left to be maximum, the air amount during lowest combustion is qMIN of F1, but varying control commencing with F3 enables control of an air amount to q'MIN at PMIN which is equal to that at a point of F1, and by determining operating ranges F3 and F2 of the varying throttle 2c on a basis of the excellent combustion range of a burner and error of a pressure sensor 7, the uneven range of the lower and upper limits of the air ratio (m) can be controlled so that it can enter an excellent combustion range even at a low combustion area. |
