The difference and characteristics of forward tilt centrifugal fan and backward tilt centrifugal fan

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Common Problem

Author：

Xuheng Electronics

Source：

Xuheng Electronics

Release time： 2021-09-15

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Forward tilt centrifugal fan:
 
Production: Made with high-quality steel plate
Advantages: low cost, low speed, thinner shaft and smaller bearing can be selected, and it has a wider operating range. Disadvantages: The shape of the performance curve may be parallel to the resistance curve of the pipe network, and the reduction of the static pressure of the system may cause the overload of the motor. In addition,
The structure of the blade is low in strength and cannot be operated at a high speed
 
Backward centrifugal fan:
Production: Casting
Advantages: high efficiency and no overload of power curve. Its power curve usually reaches the maximum value in the middle of the common range, so it is generally
Will not be overloaded. The structural strength of the blade and impeller is higher, which can be used in a higher static pressure system. Low noise, large air volume and wide high efficiency area
 
The difference and characteristics of forward tilt centrifugal fan and backward tilt centrifugal fan
 
Disadvantages: Due to the high speed of the impeller, a thicker shaft and a larger bearing are required and the balance requirements are higher. In addition, the fluctuation of static pressure is likely to cause changes in working conditions.
 
(1) Because the absolute speed C of the forward-leaving blades to the airflow is greater than that of the backward-leaving blades, the kinetic energy of the airflow is in the spiral chamber of the casing
The loss into pressure energy is also large, so the proportion of the static head used to overcome the resistance of the system is small. However, the absolute speed C of the backward-leaving blades to the airflow is small, so the loss of the airflow during energy conversion is small, so the static head used to overcome the resistance of the system accounts for a large proportion
(2) The channel in the backward-leaf blade fan is generally gradually expanded, and it is more gentle than that of the forward-leaf blade. In addition, the curvature of the backward-leaf blade is smaller than that of the forward-tilt blade, so the airflow is backward The hydraulic loss in the blade channel is smaller than that of the forward inclined blade.
 
Power consumption
Fan shaft power representation: N = (rQH) / 102η
N—Ventilator shaft power
Q—Ventilator air volume
H—Ventilator head
η—Ventilator efficiency
r—density of air
 
As can be seen from the above formula, the level of fan efficiency directly affects the size of the fan shaft power. The efficiency of the backward blade fan is high, the shaft power required by the fan is small, and the electrical energy consumed is small. However, the efficiency of the forward-leaf blade fan is low, the shaft power required by the fan is large, and the electrical energy consumed is large.
 
3. Noise
Since the absolute velocity C of the forward-leaving blades to the airflow is greater than that of the backward-leaning blades, the loss of the airflow during energy conversion is also greater, and the speed of the collision between the airflow and the casing is also greater. The air flow is gentle and smooth. Therefore, the noise of the forward-leaf fan is larger than that of the backward-leaf fan.

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