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Working Principle Of Blower
Jul 03, 2018

Working principle of centrifugal blower


The working principle of a centrifugal blower is similar to that of a centrifugal fan, but the compression process of the air is usually carried out under the action of a few working impellers (or several levels) under the action of centrifugal force. The blower has a high-speed rotating rotor. The blade on the rotor drives the air to move at a high speed. The centrifugal force makes the air inside the involute shell and flows along the involute line to the outlet of the fan. The high speed air flow has a certain wind pressure. The new air is supplemented by the center of the shell.


The working principle of a single stage high speed centrifugal fan is that the original motive is swirled at high speed through a shaft driven impeller, and the flow of air flow from the inlet of the impeller into a high-speed rotating impeller becomes radial flow and is accelerated, then enters the expansion chamber to change the flow direction and decelerates, and this deceleration effect the kinetic energy in the high speed rotating air into the pressure energy. The potential energy) keeps the outlet of the fan stable.


In theory, the pressure flow characteristic curve of centrifugal blower is a straight line, but the actual pressure and flow characteristic curve decreases with the increase of flow, and the power flow curve of the corresponding centrifugal fan increases with the increase of flow. When the fan runs at constant speed, the operating point of the fan will move along the pressure flow characteristic curve. The operating point of the fan is determined not only by its own performance, but also on the characteristics of the system. When the pipe network resistance increases, the performance curve of the pipe will steepen. The basic principle of fan regulation is to get the required working condition by changing the performance curve of the fan itself or the characteristic curve of the external network.


Principle and characteristics of frequency control


With the continuous development of science and technology, AC motor speed regulation technology is widely used. Through a new generation of fully controlled electronic components, using the frequency converter to change the speed mode of the AC motor to control the flow of the fan, it can greatly reduce the energy loss caused by the control flow of the previous mechanical mode. Energy saving principle of frequency conversion regulation:


It is known that when its speed is reduced to half of the original rated speed, the flow, pressure and shaft power of the corresponding working point drop to the original 1/2, 1/4 and 1/8, which is the reason that the frequency conversion regulation can be greatly reduced. According to the characteristic of frequency conversion, the aeration tank always keeps the normal level of 5m in the process of sewage treatment, and requires the blower to adjust the flow in a large range under the condition of constant outlet pressure. When the adjustment depth is large, the air pressure will be too large and can not meet the requirements of the process. When the adjustment depth is small, it can not show the advantage of energy saving, but make the device complex and one-time investment increase. Therefore, when the aeration tank of the project needs to maintain 5m level, the frequency conversion regulation method is obviously inappropriate.


Principle and characteristics of inlet guide vane regulation


The inlet guide leaf adjuster is to install a guide vane with adjustable angle at the suction inlet of the blower. The effect is to make the air flow rotate before entering the impeller and cause the twist speed. The guide vane can rotate around its own axis. The angle of each rotation of the blade means changing the installation angle of a guide vane to change the direction of air flow into the impeller of the fan.


Principle of regulating air volume of inlet guide vane


When the guide blade installation angle is =0, the guide vane has no effect on the inlet airflow, and the air flow will flow into the impeller blade in radial direction. When theta >0 degrees, the inlet guide leaves will make the absolute velocity of the air inlet deflect the angle of theta along the circumferential velocity, and have a certain throttle effect on the velocity of the air flow. This prerotation and throttling will lead to the decrease of the performance curve of the fan, so that the operating conditions change and the flow regulation of the fan will be realized. Energy saving principle of inlet guide vane adjustment.


When the inlet guide blade mounting angle is increased from theta 1=0 to theta 2 or theta 3, the operating point is moved from M1 to M2 or M3; the flow rate is reduced from Q1 to Q2 or Q3; the axis power is reduced from P '1 to P' 2 or P '3. The area represented by the sectional line is the power saved by the inlet guide blade than the throttling adjustment. In this project, the depth of the aeration tank is fixed, and the blower can adjust the flow rate under the constant pressure of the outlet, that is, the H= constant, and the Q= variable, the characteristic curve of the pipe network is approximate to the horizontal line. The blower is adjusted by the inlet guide blade, and the opening and closing of the guide leaf can be changed without the aid of changing the characteristic curve of the pipe network. At the angle, the pressure flow performance curve of the fan is changed, and the change of the flow is realized by moving the working point to the new changing fan characteristic curve.


The centrifugal fan adopts the inlet guide blade adjustment mode, which can obtain high efficiency and wide range of performance during the partial load operation, and the flow rate can be changed within the range of 50%~100% rated flow under constant pressure. The greater the adjustment depth and the more the work of the province. If the flow rate is reduced to 60% of the rated flow, the inlet guide vane method can save more power than the inlet throttling mode by 17%. In addition, its structure is relatively simple, reliable operation, convenient maintenance and management, low initial investment. Therefore, in this project, the inlet guide vane is used to adjust the flow rate of the blower, which is obviously the best way of regulation.

Hangzhou Hidea Power Machinery Co., Ltd.
  Add: 2/F Building 5 No.26, Xinyan Road, Yuhang Economic
       and Technological Development Zone,Yuhang District,
      Hangzhou, Zhejiang, 311100, China
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