The basic knowledge of the fan: the classification of the fan, the composition of the fan, the shaft power and the installation power, the centrifugal fan noise
I. Classification of fans:
1. Classification according to air flow direction:
Centrifugal fan: the air flow axial into the impeller through the rotation of the impeller along the radial flow.
Axial fan: the airflow enters the impeller axially and approximately flows along the cylindrical surface axially.
Mixed (oblique) flow fan: meridional acceleration, air flow direction between centrifugal and axial flow, approximately along the cone flow.
2. Classification according to leaf form:
A) Forward tilt (single suction, double suction, suitable for pressure below 1000Pa)
B) Backward tilt (divided into single piece, wing cut type, and single suction, double suction, suitable for pressure of more than 1000Pa)
C) Axial flow (iron fan blade, spiral slurry type)
D) Oblique flow and mixed flow
3, according to the type of pressure classification: low pressure, medium pressure, high pressure
4. According to the transmission form:
2, transmission mode: A, direct (inner rotor, outer rotor, motor direct, coupling)
B, belt type (common, continuous bearing, water-cooled, oil-cooled)
Fans can be divided into:
Boiler, cooling, anti-explosion, anti-corrosion, shipbuilding, textile, tunnel, dust, general industrial ventilation, air conditioning fans, etc.
Two, the classification of centrifugal fans:
Centrifugal fans have high pressure centrifugal fans and low pressure centrifugal fans, according to the different blade types of forward, radial and backward tilt several.
Three, fan composition:
Axial fan is mainly composed of wind shell, impeller and motor. Centrifugal fan is mainly composed of volute, impeller, air inlet (guide), motor, transmission group, corner frame. Accessories shock absorber, belt pulley, belt, export flange, belt cover, etc.
Among them: the material of shaft is 45# steel.
Corner frame of iron or galvanized plate production;
Bearings: oil-bearing ball bearings (UKP series) are used for small load fans, bearing with seat (frame) or double-row roller bearings are used for large power fans.
Impeller and volute: generally made of galvanized plate or hot tie plate, in special cases (transportation of corrosive gas) made of stainless steel, glass fiber reinforced plastics or PVC.
Fan base: made of channel steel or Angle iron.
Belt pulley, belt, motor for external purchase.
The zinc content of galvanized sheet used is above Z22. After making hot tie plate, it needs to be derusting and spraying treatment.
Galvanized sheet production features: beautiful appearance, not easy to rust, after production without other post-treatment, no electric welding and other operations, high efficiency, high cost. In the damp room, the surface can be sprayed with epoxy resin paint for protection treatment.
Hot tie plate features: low cost, after spraying appearance is also more beautiful, but after welding and other operations, such as not processed, in the weld and other places easy to rust and disconnect, the service life is shorter than galvanized plate.
Four, shaft power and installation power:
The power curve in each figure represents the actual power consumption of the fan, namely 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, as well as the change of resistance that may occur in the system to cause the increase of the actual power consumption of the fan. These losses are generally limited to 15% ~ 20%. Therefore, to determine the installation 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, the motor with surplus should be selected to avoid motor overload and burning in use.
Motor selection of double fan: find out the fan shaft power PW, multiply by 2.15 *1.2 safety factor, then select the motor specifications of the market. 1 HP = 0.746 KW.
Five, centrifugal fan noise:
Sound level (noise) is measured in the direction of A sound level meter at A 45 degree Angle from the tuyere, the unit is dB(A).
Sound pressure Level (LpS) conversion success rate (LwS), just add 7dB to LpS. The noise increases with the increase of impeller speed, and experience shows that for similar fans, the increase of noise is usually accompanied by the increase of speed and the decrease of efficiency. That is to say, try to use those large diameter impeller but slow speed, smooth operation of the fan, so that the working point of the fan falls in the high efficiency area.
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