Fan

AIR BLOWER

Fans are mechanical machines that rely on input mechanical energy to increase gas pressure and discharge gas. It is a driven fluid machine.

Fans are the abbreviation of our country for gas compression and gas conveying machinery. Commonly referred to as fans include fans, blowers, compressors, and roots blowers, centrifugal fans, rotary fans, and water ring fans, but piston compression is not included. Equal-displacement blowers and compressors. Gas compression and gas delivery machines are machines that convert rotating machinery into gas pressure and kinetic energy and deliver the gas.

Fans are mainly composed of blades, shutters, windowing mechanisms, motors, pulleys, air intake hoods, internal frames, housings, and safety nets. When the machine is turned on, the fan is driven by the motor to rotate, and the window opening mechanism opens the shutter to exhaust the air. The shutter closes automatically when it is stopped.

Fan application area

Fans are widely used for ventilation, dust extraction and cooling in factories, mines, tunnels, cooling towers, vehicles, ships and buildings; ventilation and induced draft in boilers and industrial furnaces; cooling and ventilation in air conditioning and household appliances Drying and delivery of cereals; wind tunnel wind sources and hovercrafts inflated and propelled.

The working principle of the fan is basically the same as that of the turbo compressor, but due to the low gas flow rate, the pressure does not change much, and generally it is not necessary to consider the change in the specific volume of the gas, that is, treat the gas as an incompressible fluid.

Fan History

The fan has a long history. For many years in China, China had created a simple wooden grain windmill. Its principle of operation is basically the same as that of modern centrifugal fans. In 1862, the British Guibel invented a centrifugal fan. Its impeller and casing were of concentric type. The casing was made of brick. The wooden impeller used backward straight blades. The efficiency was only about 40%. It was mainly used for ventilation in mines. In 1880, people designed a volute casing for the ventilation of mine shafts and a centrifugal fan with backward curved blades. The structure has been perfected.

In 1892, France developed a cross-flow fan; in 1898, the Irish designed a Siro-type centrifugal fan with forward blades, which was widely used by various countries; in the 19th century, axial fans were used in blasting in the mine ventilation and metallurgical industries. However, the pressure is only 100 to 300 Pa and the efficiency is only 15 to 25%. It did not develop until the 1940s.

In 1935, Germany first used axial-flow isobaric fans to ventilate and induce wind; in 1948, Denmark made axial-flow fans with movable blades in operation; rotary-axial fans, meridian-accelerated axial-flow fans, diagonal-flow fans, and Cross-flow fans have also been developed.

Fan classification

1. Fans can be divided into several categories according to the material used, such as iron shell fan (general fan), glass steel fan, plastic fan, aluminum fan, stainless steel fan, etc. 2. Fan classification can be divided into centrifugal type, axial flow type, oblique flow type (mixed flow type) and cross flow type according to the direction of gas flow.

3. Fans are divided into axial flow fans, centrifugal fans, and diagonal flow (mixed flow) fans, depending on the direction of flow after the airflow enters the impeller.

4. The fans are divided into press-in type local fans (hereinafter referred to as press-in type fans) and explosion-proof motors are placed outside the flow channels or in the flow channels, and the explosion-proof motor is placed in an explosion-proof sealed chamber with a drawn-out local fan (hereinafter referred to as a draw-out fan). ).

5. Fans can also be divided into single-stage, double-stage, or multi-stage pressurized fans in a pressurized manner. For example, 4-72 is a single-stage pressurization, and a Roots blower is a multi-stage pressurizing fan 6. Fans can be divided into: axial fans, mixed-flow fans, Roots blowers, roof fans, and air-conditioning fans.

7. Fan pressure can be divided into low pressure fan, medium pressure fan, high pressure fan.

Fan performance parameters

The performance parameters of the fan are flow, pressure, power, efficiency and speed. In addition, the size of noise and vibration is also a major fan design indicator. The flow rate is also called air volume, expressed in terms of the volume of gas flowing through the fan per unit time; the pressure is also referred to as wind pressure, which refers to the increase in the pressure of the gas in the fan, which is divided into static pressure, dynamic pressure and full pressure; the power is the fan The input power, shaft power. The ratio of the effective fan power to the shaft power is called efficiency. The total pressure efficiency of the fan can reach 90%.

Fan energy-saving renovation

At present, among the various types of machinery and electrical equipment in various industries in China, the motors that are matched with the wind turbines account for about 60% of the total installed capacity of electrical machinery in the country, and consume about one-third of the total electricity generated in the country. It is worth mentioning that the majority of wind turbines have the phenomenon of large horses and small carts in use, coupled with changes in production, processes, etc., need to constantly adjust the gas flow, pressure, temperature, etc.; at present, many units still The use of lagging air dampers or valve opening to adjust the gas flow, pressure, temperature, etc. This is actually a way of artificially increasing resistance, and at the expense of wasting electricity and money to meet the requirements of process and operating conditions for gas flow regulation. This backward adjustment method not only wastes valuable energy, but also has poor regulation accuracy, and it is difficult to meet the requirements of modern industrial production and services. The negative effects are very serious.