| 摘要 |
PURPOSE:To improve the performance of a fan, by enabling to set a characteristic parameter within a particular range, and disposing an air-capacity controlling means consisting of a movable stator blade at the portion of a diffuser having a length satisfying the characteristic parameter. CONSTITUTION:In case that the value of a characteristic parameter X obtained from a specific formula lines within the range of -0.6--0.4, the total-pressure efficiency of a fan is maximum and the level of noises produced by the fan is minimum. Here, providing that the length from a tongue portion 6 to the discharge port of a spiral casing is L, the characteristic parameter X is selected to take a value within the range of -0.6--0.4. At the same time, an air-capacity controlling means 13 consisting of a movable stator blade 14 is disposed at the portion 8 of a diffuser having a length L satisfying the characteristic parameter X. With such an arrangement, the performance of a fan can be improved by turning the stator blade 14 at the diffuser portion 8 as shown by an arrow in the drawing by turning a control shaft 18, and thereby changing the discharge area of the fan, thus controlling the air capacity efficiently. |
