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Cooling tower fan ventilation equipment

Cooling tower fan ventilation equipment

作者:admin    来源:未知    发布时间:2020-11-26 20:50    浏览量:
Cooling tower fan ventilation equipment

      In a natural draft cooling tower, the air volume required for water cooling is supplied by the surrounding air. The air volume in the air cylinder cooling tower is completed by the suction force generated by the tall ventilator. In the mechanical ventilation cooling tower, it is supplied by a fan. The fan used in the cooling tower is mainly an axial fan. Its characteristics are: large air volume, ventilation pressure around 20mm H2O, change the air volume and wind pressure by adjusting the blade angle, resistance to water mist and atmospheric corrosion, long-term continuous operation outdoors without failure, low noise, low energy consumption, positive and negative To rotate.
 
 
      Fans should be selected with sufficient air volume, low noise, light weight, high strength, safety and reliability, corrosion resistance, easy installation and maintenance, and products that meet the standards. The diameter of the air duct is 1% to 2% larger than the diameter of the blades of the axial flow fan (large fan takes the smaller value, and small fan takes the larger value). In a small fan, the minimum distance between the blade tip and the barrel wall is 8mm. If the distance is too large, local eddy currents will be caused and the fan efficiency will be reduced.
 
 
Blower fan
 
 
     When the cooling water is highly corrosive, in order to avoid corrosion of the fan (the blade is made of aluminum alloy, steel), the blast cooling method is adopted.
 
     In order not to make the cooling tower body too high, the diameter of the blower fan is generally less than 4m, and the distance between the fan and the tower body is usually not less than 2m to prevent the influence of water droplets in the cooling tower on the fan.

     At present, the use of axial flow fans for blast cooling is rare. The reasons are: first, the fan efficiency and cooling effect are lower than those of the suction type; second, the FRP axial flow fans have gradually Instead of a fan made of aluminum alloy and steel, the fan has the characteristics of light weight, low energy consumption, and acid and alkali corrosion resistance. Therefore, when encountering more corrosive cooling water, an exhaust type FRP axial flow fan can be used.
 
 
Suction fan
 
 
       The suction cooling tower fan is installed in the upper part of the cooling tower, and the fan blades are installed horizontally. The fan of the small tower is directly driven by the electric motor, and the electric motor is installed on the upper part of the fan in the center of the air duct. The moisture-proof performance is relatively high, and the motor shell must have strict moisture-proof measures. The electrical junction box should be sealed and waterproof, the power cord should be connected to the motor with a sleeve, and the motor shaft extension should also be waterproof, as shown in Figure 3-46. The small fan initially adopted has high wind pressure, large kinetic energy loss, and relatively high noise. Later, a wide blade fan is used, which has a large air volume, and the wind pressure is suitable for the common range, and the noise is reduced. The fan blades are thin-plate blades made of aluminum alloy or FRP. The blade is fixed to the wheel shell cross by riveting. The cross can be made of aluminum, glass fiber reinforced plastic and steel. The impeller assembly should be statically balanced.
 
 
      The reduction device of medium-sized tower fan is divided into gear reduction and belt reduction. The motor is basically still in the air duct, and the motor and the deceleration device should be protected from moisture. The gear reducer must have lubricating oil holes; the belt reducer must have belt tightening and belt protection measures.
 
      The motors of large tower fans are mostly installed outside the air duct or in the special motor room. The drive shaft and gear reduction device are connected with the fan wheel shell blades, and there is a matching lubricating oil system. The vertical reducer combines the reducer with the motor. The facilities are installed in the center of the bottom of the tower, and the fan blades installed in the upper air duct are driven by the long axis to reduce the load of the tower.

1. Fan blades
 
     The blade shape of the cooling tower fan has two types: thin plate shape and airfoil shape. The advantages of the thin plate type are simple manufacture and high strength. Large-scale wind turbines use airfoil blades. Fan blades of any material require high strength, smooth surface, uniform transition of each section, no cracks, gaps, burrs and other defects.
 
The number of blades of a cooling tower axial fan is usually 4-12.
 
     Thin-plate blades are usually made of aluminum alloy plate, glass steel plate, steel plate, etc. Airfoil blades are usually made of aluminum alloy skinned steel structure or FRP, and smaller airfoil blades are made of cast aluminum alloy or engineering plastics as the blade material.
 
2. Commonly used fans
 
The exhaust fans used in cooling towers in my country mainly include the following series:
 
(1) LF and L-type cooling tower fans LF and L-type fans have large air volume and are used as supporting fans for large and medium-sized cooling towers. The diameter of the fan blades is 2.4-9.14m. The series of fan blades are molded from high-strength epoxy glass fiber reinforced plastic. The appearance is designed as an airfoil, and the wheel shell adopts a double-plate structure. The diameter of this series of fans is widely used in the range of 4.7~9.14m.
 
(2) JXLF series cooling tower fan JXLF series fan blades are made of aluminum alloy pouring, and the blade shape is airfoil shape. It has the advantages of large air volume, high efficiency, low noise, high strength, long service life, balanced operation, and low vibration. It is suitable for continuous operation of various cooling towers under different conditions and various environments.
 
This series of fans can be equipped with FZ series vertical reducers. The vertical reducer is composed of a fan base, a drive shaft, a coupling, a reducer, and a motor. The blades are installed in the upper air cylinder of the cooling tower, and the reducer and motor are installed in the center of the bottom of the tower, and the fan blades are driven through the long axis. Suitable for large and medium glass fiber reinforced plastic cooling towers or reinforced concrete cooling towers.

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