Basic knowledge of fans

Basic knowledge of fans: classification of fans, composition of fans, shaft power and installed power, noise of centrifugal fans

To purchase a good fan, you need to know its basic knowledge in time. Today, let's learn about the classification of fans, composition of fans, shaft power and installed power, and noise of centrifugal fans with the editor of the centrifugal fan manufacturer!

1. Classification of fans:

1) Classification according to airflow direction:

Centrifugal fan: After the airflow enters the impeller axially, it flows radially through the rotation of the impeller.

Axial flow fan: After the airflow enters the impeller axially, it flows approximately along the axial surface of the cylinder.

Mixed (oblique) flow fan: Meridian acceleration type, the airflow direction is between the centrifugal type and the axial flow type, and it flows approximately along the conical surface.

 

2)Classification by blade type:

a) Forward tilt (single suction, double suction, applicable pressure below 1000Pa)

b) Backward tilt (single blade, wing section, single suction, double suction, applicable pressure above 1000Pa)

c) Axial flow (iron fan blade, propeller)

d) Oblique flow, mixed flow

3)Classification by pressure type: low pressure, medium pressure, high pressure

4)According to the transmission form:

A. Transmission mode: A. Direct type (inner rotor, outer rotor, motor direct, coupling)

B. Belt type (ordinary, seat bearing, water cooling, oil cooling)

Blowers can be divided into the following types according to the place of use and purpose:

Boiler, cooling, explosion-proof, anti-corrosion, ship, textile, tunnel, dust removal, general industrial ventilation, air conditioning fan, etc.

 

2. Classification of centrifugal fans:

Centrifugal fans include medium and high pressure centrifugal fans and medium and low pressure centrifugal fans. According to the different blade types, they are divided into forward-inclined, radial and backward-inclined types.

 

3. Composition of fans:

Axial flow fans are mainly composed of wind casing, impeller and motor; centrifugal fans are mainly composed of volute, impeller, air inlet (deflector), motor, transmission group and angle frame. Accessories include shock absorber, pulley, belt, outlet flange, belt guard, etc.

Among them: the material of the shaft is 45# steel.

The angle iron or galvanized sheet of the angle frame is made;

Bearings: small load fans use oil-containing ball bearings (UKP series), and high power fans use seat bearings (machine base) or double-row roller bearings.

Impeller and volute: generally made of galvanized sheet or hot-rolled sheet, special cases (transporting corrosive gases) are made of stainless steel, fiberglass or PVC.

Fan base: made of channel steel or angle iron.

The pulley, belt and motor are purchased.

The zinc content of the galvanized sheet used is above Z22. After the hot-rolled sheet is made, it needs to be rust-free and spray-painted.

Features of galvanized sheet production: beautiful appearance, not easy to rust, no other post-processing is required after production, no electric welding and other operations, high work efficiency, and high cost. In humid places, the surface can be sprayed with epoxy resin paint for protection.

Features of hot-rolled sheet: low cost, beautiful appearance after spraying, but after electric welding and other operations, if not handled well, it is easy to rust and break in places such as welds, and the service life is shorter than that of galvanized sheet.

 

4. Shaft power and installed power:

The power curve in each figure represents the actual power consumption of the fan, that is, the shaft power, in KW (kilowatt) or HP (horsepower). When matching the motor power, to avoid overheating of the motor, it is necessary to calculate the transmission loss and the possible resistance changes in the system that cause the actual power consumption of the fan to increase. These losses are generally limited to 15% to 20%. Therefore, to determine the installed power of the motor, the actual power consumption of the fan should be multiplied by 1.2 (safety factor). When the calculated value is at the critical point, a motor with a margin should be selected to avoid motor overload and burning during use.

Motor selection for double fan: Find the shaft power PW of the fan, multiply it by 2.15 and then * 1.2 safety factor to select the commercially available motor specifications. 1HP=0.746KW.

V. Centrifugal fan noise:

The sound level (noise) is measured at 1 meter away from the air outlet, at a 45-degree angle to its axis, using an A sound level meter for detection, and the unit is dB (A).

To convert the sound pressure level (LpS) into the power level (LwS), just add 7db to the LpS. Noise increases with the increase of impeller speed. Experience shows that for similar fans, the increase of noise is usually accompanied by an increase in speed and a decrease in efficiency. That is to say, try to use fans with large diameter impellers but slow speed and stable operation, so that the working point of the fan falls in the high efficiency area.

Shandong Hanqi Industrial Co., Ltd. mainly produces, sells and installs axial flow fans, centrifugal fans and tunnel fans. All products are sold directly by the manufacturer with excellent quality assurance. If you have related product needs, please contact us for purchase!