When many customers buy centrifugal fans, they will know that there are many types of centrifugal fans. Among them, forward tilting and backward tilting are often heard, but they do not know the specific difference between forward tilting and backward tilting.
1. The meaning of the forward and backward tilt of the centrifugal fan
The forward tilt and backward tilt of the centrifugal fan mainly refer to the difference in the outlet angle of the impeller blades. When the outlet angle of the blade is less than 90°, it is a backward tilt centrifugal fan, and when the blade outlet angle is greater than 90°, it is a forward tilt centrifugal fan. Fan, as shown below:
1. Advantages and disadvantages of forward inclined centrifugal fans
Advantages: Low cost, low speed, can choose thinner shaft and smaller bearing, and 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 motor to overload. In addition, the structural strength of the blade is low, and it cannot run at a higher rotational speed.
2. Advantages and disadvantages of backward inclined centrifugal fans
Advantages:High efficiency and no overload on power curve. Its power curve usually reaches the upper limit in the middle of the usual range, so that it is generally not overloaded. Blades and impellers have high structural strength and can be used in high static pressure systems. Low noise, large air volume, and wide high-efficiency area.
Disadvantages: Due to the high running speed of the impeller, a thicker shaft and a larger bearing are required and the requirements for balance are high. In addition, the fluctuation of static pressure can easily cause changes in working conditions.
Second, the difference between the forward and backward tilt of the centrifugal fan
1. Backward leaning is more efficient than forward leaning
When the size and speed of the fan are the same, the larger the outlet angle, the higher the pressure generated. Therefore, the advantage of the forward-inclined centrifugal fan compared with the backward-inclined centrifugal fan is that the full head is larger. However, the dynamic pressure head of the forward-tilting fan accounts for a larger proportion of the total pressure head, and the airflow velocity is high, and the loss when converted into static pressure is also greater, so the efficiency is not as high as that of the backward-tilting blower. The shape of the performance curve and the resistance curve may be parallel, the blade structure is low in strength, and the speed is low. When the static pressure of the system is reduced, it is likely to cause the motor to overload. That is to say, if you want to achieve the same air volume and pressure, the rotation speed of the backward-inclined centrifugal fan is higher than that of the forward-inclined centrifugal fan. Since the efficiency of the forward-inclined fan is lower than that of the backward-inclined fan, the relative power required by the centrifugal fan is required. Just a little bigger, the motor power should be configured larger.
2. The energy consumption of backward leaning is less than that of forward leaning
Generally, the shaft power of a centrifugal fan is inversely proportional to its efficiency, and the smaller the shaft power, the less energy consumption. Since the efficiency of the backward-inclined centrifugal fan is higher than that of the forward-inclined centrifugal fan, its shaft power is also smaller, and the energy consumption is naturally lower. Correspondingly, the power of the forward-inclined centrifugal fan is low, and the shaft power is large, so the energy consumption is more.
3. The noise of backward leaning is smaller than that of forward leaning
Because the speed of the forward-inclined centrifugal fan to the airflow is higher than that of the backward-inclined centrifugal fan, the loss of the airflow during energy conversion is also larger, and the collision speed of the airflow with the casing is also larger. In addition, the backward-inclined centrifugal fan blade groove The curvature of the road is relatively gentle, and the airflow is relatively smooth, so the noise of the backward-inclined centrifugal fan is lower than that of the forward-inclined centrifugal fan.
4. The forward leaning body is smaller than the backward leaning body
Usually in the design and selection of the fan, the product of the flow coefficient and the pressure coefficient of the centrifugal fan will be used to measure the size of the centrifugal fan body. The coefficient product of the forward-inclined centrifugal fan is larger than that of the backward-inclined centrifugal fan. The body will be smaller than the backward tilt centrifugal fan.
3. The performance curve of the centrifugal fan forward and backward
1. Performance of forward-inclined centrifugal fan
| Performance/Workspace | Left side of the A curve | Right side of B curve |
| Efficiency | Decrease as air volume decreases | Decrease as air volume decreases |
| Air volume | unstable, fluctuating | stable with little fluctuation |
| Static pressure | Decrease as air volume decreases | Decrease as air volume decreases |
| Starting Power | As the air volume decreases | With the rapid increase in air volume |
| Noise | Decrease as air volume decreases | increase with air volume |
| Fan phenomenon | generate turbulence | Motor overload |
2. Performance of backward inclined centrifugal fan
| Performance/Workspace | Left side of the A curve | Right side of B curve |
| Efficiency | Decrease as air volume decreases | Decrease as air volume decreases |
| Air volume | unstable, fluctuating | stable with little fluctuation |
| Static pressure | As the air volume slowly decreases | Decrease as air volume decreases |
| Starting Power | Decrease as air volume decreases | Decrease as air volume decreases |
| Noise | increase with air volume | increase with air volume |
| Fan phenomenon | generate turbulence | Efficiency drops |
