Features of fans
1. Application of fan products
Fan is a kind of machinery which is mainly used to pump, transport and improve fluid energy. It is mainly used in ventilation of mine, underground engineering and underground power plant; ventilation and induced draft of boiler; high temperature corrosive gas emission of chemical plant; ventilation of workshop air conditioning and atomic protection equipment. Fan is widely used, in short, it is mainly used to assist full combustion, ventilation, transportation, almost involving all areas of the national economy.
2. Types of fans
According to its structure and mechanism, fans can be divided into three types
(1) Centrifugal: the principle is to use the rotating impeller to produce centrifugal force or lift to transport fluid and increase its pressure. According to the way of obtaining energy, it can be divided into centrifugal fan and axial fan. This type of fan has small mechanical structure, light weight, high efficiency, large and uniform flow, and can be connected with high-speed prime mover. The disadvantage is that when the flow changes, the pressure and efficiency also change.
The centrifugal fan can be divided into three types according to its wind pressure
·Centrifugal fan, the wind pressure is lower than or equal to 17400n / m2, the gas is not compressed, mainly used for tunnel and mine ventilation, boiler air supply, induced draft, air conditioning ventilation, etc.
·Centrifugal blower with air pressure of 14700-34300n / m2 is mainly used for conveying air, sintering flue gas, gas, sulfur dioxide and some chemical gases or mixed gases.
·Centrifugal compressor, with wind pressure above 34300n / m2, is mainly used for conveying nitrogen, carbon dioxide, tar gas, catalytic gas and other chemical gases. It is used for ethylene synthesis, urea synthesis, alkali production and oil refining in chemical plants and refineries.
(2) Axial flow type: the principle also relies on the rotation of the impeller, and the blade generates lift to transport the fluid, converting the mechanical energy into fluid energy. As the fluid into and out of the impeller are axial, it is called axial fan. Axial flow fan belongs to high specific speed, which is characterized by large flow and low wind pressure. The air pressure of axial flow fan is generally between 450N / m2 and 4500n / m2. It is mainly used for ventilation of mine, tunnel and ship warehouse; ventilation and cooling of textile factory and industrial workplace; chemical gas discharge; ventilation and induced draft of boiler in thermal power plant; ventilation and cooling of cooling tower in thermal power station, metallurgy and chemical industry. At present, according to the wind pressure, the axial-flow fan in our country is divided into axial-flow compressor and axial-flow fan.
(3) Rotary type: it is a kind of machinery that uses a pair or several special shape revolving bodies (gear screw, scraper or other shape rotors) to rotate in the shell to complete the gas transmission or increase its pressure. This type of mechanical structure is simple, compact, safe and reliable, and can be connected with high-speed prime mover. Rotary fan mainly includes roots blower and blade blower. Its characteristic is that the exhaust volume does not change with the resistance, and it is especially suitable for the process flow requiring stable flow rate. Generally, it is used in the range of 0.12kgf / square centimeter for small converter, casting workshop, blast furnace, refinery blow, textile mill spray, pneumatic conveying, transportation, gas tar industry and chemical industry. Roots blower can also be used to increase the main body pressure.
3. Main technical parameters of fan
(1) Flow: the volume flow or mass flow delivered by the fan in unit time.
(2) Wind pressure: the increased energy of fluid in the fan, that is, the increased value of energy obtained when the unit mass flow (unit volume flow) passes through the fan.
(3) Speed: the speed of the fan per minute.
(4) Power or efficiency: the ratio of the energy (effective power) obtained by the fluid passing through the fan in unit time to the power transmitted by the prime mover to the fan.
