Equipment features (design principles)

Determine the required air volume and pressure based on the needs of the exhaust system, and then add some margin to determine the fan specifications.

Then select the appropriate motor (explosion-proof & energy efficiency, etc...), material (casing & impeller, etc...), transmission method (coupling & belt & motor shaft direct connection) and required fan accessories (rubber shock absorber) Pad etc...)

The classification of its design structure is roughly as follows：

• According to the impeller type → Aerobo, Aerofoil, Turbo, Radial, Paddle, Multi-blade, Axial
• According to the direction of air flow → centrifugal type, axial flow type
• According to the blade angle → 45° for backward type, 90° for radial type, 135° for forward type
• Depending on the load current
• According to the main side plate of the blade → standard impeller (closed), semi-open impeller (semi-open), paddle impeller (full-open)

Use and structure

Fans are used in a wide range of industries, including pollution control, petrochemical, cement, chemical, mining, steel, transportation, electronics and other industries, and can even be found in office buildings or ordinary homes. A fan is a type of air machinery. Its purpose is to overcome the friction resistance caused by gas flow in pipelines and equipment and deliver the required air volume or gas to a designated location.

The structure of the fan can be divided into cast type and steel plate welded type according to the production method. When the required static pressure is higher, a multi-stage fan can be selected; according to the transmission method, it can be divided into belt drive, coupling direct drive, and horizontal motor shaft. Direct drive, vertical motor shaft direct drive. According to the suction inlet mode, it can be divided into single-suction type and double-suction type: Generally, fans are mostly single-suction type. When the demand for air volume is large, in order to obtain a better specific speed or save space, double-suction fans are usually used.

Comparison between cast and steel plate fans

• Casting type fan

The inlet cone and impeller are machined, so the gap is small, and the backflow of gas compressed by the impeller is minimal.

The impeller outlet is connected by an annular air duct, which will not cause rapid diffusion of pressure loss and reduce gas leakage.

The internal flow field of the casting fan can be designed according to fluid mechanics to avoid the generation of separation and vortex, which are the main causes of low efficiency.

• Steel plate fan

The inlet cone and impeller are not machined and have a large gap. The gas compressed by the impeller will flow back to the inlet. It is like installing a return pipe or a hole between the outlet and inlet of the fan, causing the fan to perform in vain. The higher the static pressure, the more leakage and the lower the efficiency.

The casing is welded, and there is no annular air duct connection at the impeller outlet. The gas compressed by the impeller quickly diffuses into the wide casing, causing pressure loss of the gas and making it easier for the gas to flow back to the inlet.

In order to reduce the cost, simplify and make it easy to manufacture, the flow field of the steel plate type fan is difficult to be designed according to the ideal fluid mechanics. It is easy to cause peeling and vortex during the compression process, so the efficiency is low and the noise is high.