Working Process of a Centrifugal Blower
Intake Stage: When the impeller begins to rotate, a negative pressure zone is formed at the center of the impeller due to centrifugal force. External gas is drawn into the impeller center through the inlet.
Acceleration Stage: After entering the impeller, the gas moves radially under the action of the blades. The blades exert a force on the gas, gradually increasing its velocity and thus gaining kinetic energy.
Pressure Stage: The high-speed flowing gas leaves the impeller and enters the centrifugal blower casing. The casing converts the velocity energy of the high-speed airflow into pressure energy, significantly increasing the gas pressure.
Discharge Stage: The pressurized gas is discharged from the outlet of the casing and enters the system or environment requiring air supply.
II. Structural Features of a Centrifugal Blower
The centrifugal blower fan mainly consists of a casing, rotor assembly, sealing device, bearing support, lubrication system, and other components. Based on the bearing support type, the centrifugal blower fan structure can be manufactured as a cantilever type or a double-support type.
1. Centrifugal Blower Fan Casing: The casing of a centrifugal blower is made of cast iron or welded from steel plates. Industrial centrifugal blower casings can be horizontally split or volute-shaped depending on the impeller design. For low-pressure industrial centrifugal blowers, the casing is mostly horizontally split. For single-stage blowers, it is mostly volute-shaped. The function of the volute is to collect the gas pressurized by the impeller and then guide it into the flow channel. Centrifugal multi-stage blower casings contain components such as a return chamber, baffles, and diffusers. Gas enters the return chamber through the diffuser and is then introduced into the next stage impeller, continuously delivering gas into the pipeline.
2. Centrifugal Blower Fan Rotor Assembly: The main component of a centrifugal blower is the rotor, which consists of an impeller, main shaft, bushing, exhaust chamber, balance disc, seals, coupling, etc.
① Industrial centrifugal fan impeller: The industrial centrifugal fan impeller is made of a disc, hub, and blades riveted, welded, or integrally cast. The main function of an industrial centrifugal fan is to increase the pressure and airflow velocity of gas after it passes through the impeller.
② Industrial centrifugal fan main shaft: The main shaft houses the rotating parts of the fan. Its function is to transmit torque to rotate the impeller. Generally, the shaft of a centrifugal fan extends outside the casing.
③ Industrial centrifugal fan coupling: The industrial centrifugal fan coupling connects the drive motor and the fan shaft, transmitting the torque of the drive motor and also serving a safety connection function.
3. Centrifugal blower fan seals: The interstage seals of centrifugal blowers used in chemical plants are mostly labyrinth seals. Labyrinth seal structures are the most commonly used, including pulley seals and comb seals. Shaft end seals are mostly O-rings and expansion rings. The inserts for Labbeling seals and Hangzhou gear seals should generally be made of thin, soft metal sheets, such as aluminum alloys and stainless steel sheets. Non-metallic materials commonly use plastic sheets.
4. Centrifugal blower fan inlet regulating blades: The inlet blade regulating control device is used to regulate the airflow from the blades. Its structure consists of movable blades at the fan inlet, installed radially. Changing the blade angle changes the impeller speed. The inlet blade regulating control device is made of welded steel plates, and all blades are designed to rotate 90° around the blade shaft to adjust the airflow rate from the fan. The blade direction can be closed or open to adapt to the fan's rotation direction, providing effective pre-swirl to the impeller inlet components.
5. Centrifugal blower fan bearings: Industrial blower fan bearings are components that support the rotor, ensuring smooth rotor rotation, and also regulating the radial and axial forces generated by the rotating rotor. For low-pressure, low-speed fans, sliding bearings are mostly used; for medium-pressure and high-speed fans, rolling bearings are mostly used.
6. Centrifugal blower fan lubrication system: The lubrication system of centrifugal blowers generally adopts constant oil level self-flowing lubrication. There are many forms of industrial blower fan, including oil cups, oil guns, etc., but for large high-speed blowers, there is a separate lubrication system with oil pump, oil tank, filter, cooler, etc.
