The difference and characteristics between the forward tilt centrifugal fan and the backward tilt centrifugal fan

Forward tilt centrifugal fan  

Production: made of high-quality steel plate 

Advantage:

With low cost and low speed, thinner shafts and smaller bearings can be selected, and the operating range is wide. 

Disadvantages:

The shape of the performance curve may be parallel to the resistance curve of the pipe network, and the reduction of the system static pressure may lead to motor overload. In addition, the structural strength of the blade is low, and it cannot operate at a higher speed

Backward inclined centrifugal fan

Production: casting 

Advantage:

High efficiency and no overload on power curve. Its power curve usually reaches the peak value in the middle of the common range, so it will not be overloaded generally. The structural strength of blades and impellers is relatively high, which can be used in higher hydrostatic systems. Low noise, large air volume, wide high efficiency area 

Disadvantages:

Due to the high running speed of the impeller, a thicker shaft and larger bearing are required, and the requirements for balance are high. In addition, the fluctuation of static pressure is easy to cause changes in working conditions 

(1) Since the absolute velocity C of the air flow transmitted from the forward inclined blade is larger than that from the backward inclined blade, the loss of the kinetic energy of the air flow converted into pressure energy in the spiral chamber of the casing is also large, so the proportion of the static head used to overcome the system resistance is very small. The absolute velocity C transmitted from the backward inclined blade to the air flow is small, so the loss of air flow during energy conversion is small, so the static head used to overcome the system resistance accounts for a large proportion.

(2) The channel in the fan with backward inclined blades is generally gradually expanded, and the expansion is more moderate than that of the forward inclined blades. In addition, the curvature of the backward inclined blades is smaller than that of the forward inclined blades, so the hydraulic loss of air flow in the backward inclined blade channel is smaller than that of the forward inclined blades.

Electric energy consumption (shaft power of fan)

N=(rQH)/102η 

N - Fan shaft power 

Q - Fan air volume   

H-ventilator head   

η— Fan efficiency                              

R - Volume weight of air 

It can be seen from the above formula that the fan efficiency directly affects the fan shaft power. The backward inclined blade fan has high efficiency, small shaft power required by the fan, and less power consumption. However, the efficiency of the forward inclined blade fan is low, the shaft power required by the fan is large, and more electric energy is consumed. 

noise   

Since the absolute velocity C of the air flow from the forward inclined blade is larger than that from the backward inclined blade, the loss of the air flow during energy conversion is also large, and the speed of the air flow colliding with the casing is also large. In addition, the curvature of the channel of the backward inclined blade is gentle, and the air flow is relatively smooth. Therefore, the noise of the fan with forward inclined blades is greater than that of the fan with backward inclined blades.

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