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1. Ventilation fan can be divided into low pressure, medium pressure and high pressure centrifugal fans according to the working pressure.
2. According to the air intake mode, it can be divided into double intake fan and single intake fan.
3. According to the shape of the blade, it is divided into a forward-inclined centrifugal fan and a backward-inclined centrifugal fan.
Second, the difference between the induced draft fan
1. The total pressure of the low-pressure fan is P≤1000Pa, the total pressure of the high-pressure fan is P>8000-30000Pa, and the medium-pressure fan is between the two.
2. The single air inlet fan has only one air inlet, and the transmission is convenient and flexible.
3. The double air inlet fan has two air inlets, and the air enters from both sides of the impeller. It adopts a double support structure and has high operation stability.
4. The forward tilting fan has low cost and low speed, but the blade strength is low, so it cannot run at high speed.
5. The backward tilting fan has high efficiency, low noise and large air volume, but has higher requirements on bearings.
3. Selection methods and principles
1. Choose a fan with high efficiency, small size and large adjustment range.
2. To reduce noise, the fan speed must be reduced and a larger fan should be selected. For the selection of large fans, under normal circumstances, large fans need to be installed in small air volume areas to enhance the air circulation speed. In this way, the pressure difference between the inlet and outlet of the fan is relatively large, resulting in vibration and noise.
3. For the selection of small fans, the main reason is that the air circulation is not very slow, and the small fans need to be installed where the fans play a promoting role. In this case, the fan impeller rotates very fast, which generates a large centrifugal force and makes noise.
