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[Fan types and features] Blower fan

Blower fan features

Last time we introduced Centrifugal Fan. Next we will explain about blower fans.

Blower fan structure

A blower fan is structurally similar to Centrifugal Fan. Like Centrifugal Fan, it rotates an impeller to draw in air from an opening at the front and expel it from the side. The big difference is that the impeller is covered by an ammonite-shaped case, which has an exhaust port in one location. As the impeller rotates, the air coming out radially flows along the inside of the case and is expelled from the exhaust port.

▲Figure 1: Blower structure
▲Figure 1: Blower fan structure

Blower fan characteristics

Figure 2: Example of ventilation resistance and air volume - static pressure characteristics
Figure 2: Example of ventilation resistance and air volume - static pressure characteristics

Blower fans provide higher static pressure than axial fans of equivalent size or Centrifugal Fan by allowing air to flow along the inside of the case. On the other hand, they tend to produce less airflow. Also, the impeller has many smaller blades than Centrifugal Fan, which is also shaped to obtain higher static pressure.
The blower P-Q performance is similar to Centrifugal Fan as shown in Figure 2, with no swirl stall region, and the shape of P-Q performance is similar to that of . Power consumption does not increase or decrease with airflow as in axial fans and Centrifugal Fan, but tends to decrease as airflow decreases and static pressure increases. Therefore, the blower generally consumes the most power at maximum airflow. Sound pressure levels tend to be quietest in the middle of the P-Q performance range.

Figure 2: Example of ventilation resistance and air volume - static pressure characteristics
Figure 2: Example of ventilation resistance and air volume - static pressure characteristics

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How to use a blower fan smartly

Since the blower has no swivel stall area in P-Q performance, there are no restrictions on the position of the operating point with the ventilation resistance, and the recommended range of use is wide. The sound pressure level is quietest around the center of P-Q performance, so it is important to operate in this area to reduce the noise level of the equipment.
Blowers are characterized by their ability to obtain high static pressure among fans. Therefore, they are suitable for use in equipment with dense components and high ventilation resistance. Also, since air is discharged from a single point, it is suitable for localized cooling by direct application of airflow.

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Supervised by: SANYO DENKI CO., LTD. Cooling System Design Department

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