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Blower definition


Author : adminViews : 504 Time : 2018-08-18

The blower is mainly composed of the following six parts: motor, air filter, blower body, air chamber, base (and fuel tank), and drip nozzle. The blower is operated eccentrically by the rotor biased in the cylinder, and the volume change between the blades in the rotor groove sucks, compresses, and discharges the air. In operation, the pressure difference of the blower is used to automatically send the lubrication to the drip nozzle, and drip into the cylinder to reduce friction and noise, and at the same time keep the gas in the cylinder from flowing back. This type of blower is also called a vane blower.


history


Fans, blowpipes, and skins, the earliest appliances used to force blasts are fans and blowpipes. Ancient Egyptian goldsmiths used a blowpipe with a terracotta nozzle, and the Inca sometimes used 8 to 12 copper tubes to simultaneously blow. Later, a blast capsule made of animal skin was invented, and the air duct and the air inlet controlled by the operator were divided at both ends of the capsule. This simple blower is still used in some areas in modern times. An image of a canister-shaped foot blower has been painted in the murals of the Tomb of Egypt's Eighteenth Rekhmir (circa 1450 BC). When entering the wind, the operator picks up the skin with a rope, then presses it down, and the wind is blown into the furnace. Each furnace is equipped with four blowers, and the two are operated in opposite directions.


2 features


1. The blower operates without friction in the machine body and does not require lubrication, so that the discharged gas does not contain oil. It is an ideal pneumatic conveying source for chemical, food and other industries.


2. The blower is a volume operated blower. When used, the flow changes very little as the pressure changes. But the flow varies with the speed. Therefore, the choice of pressure is wide, and the choice of flow can be achieved by selecting the speed.


3. The speed of the blower is relatively high, and the gap between the rotor and the rotor, the rotor and the body is small, so that leakage is small and the volumetric efficiency is high.


4. The structure of the blower determines that its mechanical friction loss is very small. Because only the bearing and gear pair have mechanical contact on the material selection, the rotor, casing and gear ring have sufficient mechanical strength. Safe operation and long service life are a major feature of blower products.


5. The rotor of the blower is checked by static and dynamic balance. The finished product runs smoothly and the vibration is extremely small.


6. The blowers with the above characteristics mainly include: Roots blower, side flow fan, multi-stage centrifugal blower. [1]


 


3 classification


According to wind pressure


According to the pressure of the fan, the fan can be divided into a low pressure fan, a medium pressure fan and a high pressure fan.


The pressure range is as follows:


Low pressure: total fan pressure H ≤1000Pa


Medium pressure: 1000Pa < H ≤ 3000Pa


High pressure (centrifugal fan): 3000Pa < H ≤15000 Pa


Low-pressure and medium-low pressure fans are mostly used in ventilation engineering.


Can be divided into centrifugal fan and axial flow fan water treatment blast aeration;


Stirring and aeration of sewage in hospitals and laboratories;


Vacuum feeding in the printing industry;


Stirring and aeration of electroplating tanks and industrial wastewater;


Supply of plastic welding and blowing air supply;


Burner spray, glass industry and others;


By technology


According to the bearing technology, it can be divided into general mechanical bearing blower, magnetic suspension blower and air suspension bearing blower.


 


4 structure


Rotor: It consists of shaft, impeller, bearing, synchronous gear, coupling, bushing and so on.


Impeller: The involute profile is selected for high volume utilization.


Bearing: 3000 type double row radial spherical roller bearing is used as the positioning end of the proximal coupling end. As the free end, the 32000 type single row radial short cylindrical roller bearing is selected as the free end to accommodate the axial displacement of the rotor during thermal expansion.


Synchronous gear: It consists of a ring gear and a hub for easy adjustment of the impeller clearance.


Body: It consists of a casing and left and right wall panels. The left and right wall panels and the bearing housings and seals installed in the left and right wall panels can be used interchangeably.


Base: The medium and small fans are equipped with a common base, and the large fan is only equipped with a fan base for easy installation and debugging.


Lubrication: The gears are immersed and the bearings are splash-lubricated. Good lubrication, safe and reliable.


Transmission mode: The coupling is mainly connected directly. If the performance specifications are required, the V-belt shifting mode can also be selected. The coupling uses a flexible coupling to mitigate shock and compensate for a small amount of axis deviation. In addition to the electric motor as the drive machine, a large flow fan can also be used as a steam turbine or other drive machine.


 


5 use operation


The operator must be familiar with this procedure before starting the machine and operate the blower in strict accordance with this procedure.


1. Check the oil level of the fuel tank, which should be between the oil level and the lower limit.


2. Notify the substation to supply power to the unit.


3, check the control cabinet on the machine, there should be no alarm display, if there is an alarm, find out the reason to eliminate


4. Select the "Manual" status. (Touch the "Manual" button with your finger).


5. Check if the pressure relief valve is in the open position (the pressure relief valve is open and the green light is on). Check that the diffuser should be placed at the minimum opening (the diffuser has a minimum green light).


6. After the above check, confirm that the fan can be started, press the start button, and the blower enters the starting procedure: 1 The auxiliary oil pump is pre-lubricated for one minute (the auxiliary oil pump is running green light). 2 The blower can start running (the blower is running green).


3 The pressure relief valve is slowly closed (the pressure relief valve is turned on and the green light is off, and after two minutes, the pressure relief valve is closed and the green light is on).


4 The auxiliary oil pump stops running (the auxiliary oil pump is running green and the red light is off). At this point, the blower is successfully started and can be put into formal operation.


5 If the blower fails to start as scheduled after pressing the start button, the oil pressure is too low and the red light is on after one minute, and the whole starting process stops. It must be ascertained that the cause is resolved and the alarm is restarted.


1. After the fan is started, the diffuser opening degree can be slowly adjusted according to the production needs, and the diffuser “open” button and “close” button are used to control the necessary air volume.


2. When the fan is running, the fan must be monitored frequently, pay attention to the fan current, oil temperature, oil pressure, air pressure, sound, fan, temperature, vibration and so on. Record on time, if there is any abnormality, it is necessary to promptly identify the cause for exclusion, and report to the production department, if necessary, take emergency parking measures (use with caution).


Due to production or maintenance, maintenance needs, when a certain fan is stopped.


1. Reduce the diffuser opening to the minimum (the diffuser minimum indicator green light is on).


2. Touch the fan "stop" button with your finger and the shutdown program starts:


 


6 uses


The blower is mainly composed of the following six parts: motor, air filter, blower body, air chamber, base (and fuel tank), and drip nozzle. The blower is operated eccentrically by the rotor biased in the cylinder, and the volume change between the blades in the rotor groove sucks, compresses, and discharges the air. In operation, the pressure difference of the blower is used to automatically send the lubrication to the drip nozzle, and drip into the cylinder to reduce friction and noise, and at the same time keep the gas in the cylinder from flowing back. This type of blower is also called a vane blower. The blower delivers medium to clean air, clean gas, sulfur dioxide and other inert gases. It can also produce other flammable, explosive, corrosive, toxic and special gases on demand.


 


7 energy-saving transformation


Fan energy saving transformation


Today's motors and wind turbines in all types of machinery and electrical equipment in China account for about 60% of the country's total installed capacity of electrical machinery, and electricity consumption accounts for about one-third of the country's total power generation. It is particularly worth mentioning that most wind turbines have large horse-drawn carriages during use. In addition, due to changes in production and processes, it is necessary to constantly adjust the flow, pressure, temperature, etc. of the gas; many units still use The backward adjustment of the wind plate or valve opening degree to adjust the gas flow, pressure, temperature and so on. This is actually a way to increase the resistance by artificially, and to meet the requirements of gas flow regulation in process and working conditions at the expense of energy and money. This backward adjustment method not only wastes precious energy, but also has poor adjustment accuracy. It is difficult to meet the requirements of modern industrial production and service, and the negative effects are very serious.


In recent years, with the rapid development of power electronics technology, computer technology and automatic control technology, electric drive technology is facing a historical revolution, that is, AC speed regulation instead of DC speed regulation and computer digital control technology have replaced analog control technology. trend. Motor AC frequency conversion speed regulation technology is a major means of saving electricity and improving process flow to improve product quality, improve environment and promote technological progress.


 


8 working principle


How centrifugal blowers work


Centrifugal blowers work similarly to centrifugal fans, except that the air compression process is usually carried out by several working impellers (or several stages) under centrifugal force. The blower has a rotor that rotates at a high speed. The blades on the rotor drive the high-speed movement of the air. The centrifugal force causes the air to flow in the involute-shaped casing along the involute to the fan outlet, and the high-speed airflow has a certain wind pressure. The new air is replenished by the center of the casing.


The working principle of the single-stage high-speed centrifugal fan is that the prime mover drives the impeller to rotate at a high speed through the shaft. The airflow enters the high-speed rotating impeller and becomes radial flow, which is accelerated, then enters the diffusing chamber and changes the flow direction to decelerate. This deceleration converts the kinetic energy of the high-speed rotating airflow into pressure energy (potential energy), which maintains a stable pressure at the fan outlet.


Theoretically, the pressure-flow characteristic curve of the centrifugal blower is a straight line, but due to the frictional resistance loss inside the fan, the actual pressure and flow characteristic curve gradually decreases with the increase of the flow rate, and the power of the corresponding centrifugal fan - The flow curve rises as the flow rate increases. When the fan is running at a constant speed, the operating point of the fan will move along the pressure-flow characteristic curve. The operating point of the fan is not only dependent on its own performance, but also depends on the characteristics of the system. When the pipe network resistance increases, the pipeline performance curve will become steeper. The basic principle of fan adjustment is to obtain the required working condition by changing the performance curve of the fan itself or the external pipe network characteristic curve.


Frequency control principle and characteristics


        With the continuous development of technology, AC motor speed control technology is widely used. Through the new generation of fully-controlled electronic components, the inverter can change the speed of the AC motor to control the fan flow, which can greatly reduce the energy loss caused by the mechanical regulation of the flow. Energy-saving principle of frequency conversion adjustment:


        It can be seen that when the rotation speed is reduced to half of the original rated speed, the flow rate, pressure and shaft power of the corresponding operating point are reduced to 1/2, 1/4, and 1/8 of the original. The reason for saving electricity. According to the characteristics of frequency conversion regulation, for the sewage treatment process, the aeration tank always maintains a normal liquid level of 5m, and the blower is required to perform a wide range of flow adjustment under the condition of constant outlet pressure. When the adjustment depth is large, The wind pressure is too large to meet the process requirements. When the adjustment depth is small, the advantage of energy saving is not displayed, but the device is complicated and the one-time investment is increased. Therefore, under the condition that the aeration tank of this project needs to maintain a liquid level of 5m, it is obviously inappropriate to adopt the frequency conversion adjustment method.


Imported guide vane adjustment principle and characteristics


        The inlet guide vane adjusting device is provided with a set of guide vanes-introducing guide vanes with adjustable angles near the suction inlet of the blower, and the function is to rotate the airflow before entering the impeller, resulting in a twisting speed. The vane can be rotated about its own axis. Each angle of rotation of the vane means that a vane mounting angle is changed, so that the direction of the airflow entering the fan impeller changes accordingly.


Imported guide vane to adjust air volume principle


        When the vane mounting angle θ = 0°, the vanes have substantially no effect on the inlet gas flow, and the gas flow will flow radially into the impeller blades. When θ>0°, the inlet guide vanes will deflect the absolute velocity of the airflow inlet in the circumferential speed direction by an angle θ, and at the same time have a certain throttling effect on the velocity of the airflow inlet. This pre-rotation and throttling will result in fan performance. The curve is lowered, so that the operating point changes, and the fan flow adjustment is realized. Energy-saving principle of inlet guide vane adjustment.


        When the inlet guide vane installation angle is increased from θ1=0° to θ2 or θ3, the operating condition point is moved from M1 to M2 or M3; the flow rate is reduced from Q1 to Q2 or Q3; the shaft power is reduced from P'1 to P '2 or P'3. The area indicated by the hatching is the power saved by the inlet guide vanes compared to the throttling adjustment. In this project, the depth of the aeration tank is fixed, and the blower performs flow adjustment under the condition that the outlet pressure is kept constant, that is, H=constant, when Q=variable, the characteristic curve of the pipe network approximates a horizontal straight line, and the blower adopts the inlet guide. The leaf adjustment, without changing the pipe network characteristic curve, can change the pressure-flow performance curve of the fan by changing the opening and closing angle of the vane, and the flow rate change is by moving the operating point to the new changed fan characteristic. The method on the curve is implemented.


        The centrifugal fan adopts the inlet guide vane adjustment mode, which can obtain high efficiency and wide performance range during partial load operation. Under the condition of keeping the outlet pressure constant, the working flow can be changed within the range of 50% to 100% of rated flow. The greater the adjustment depth, the more labor. If the flow rate is reduced to 60% of the rated flow, the inlet vane mode saves up to 17% more power than the inlet throttling method. In addition, its structure is relatively simple, reliable operation, convenient maintenance and management, and low initial investment. Therefore, the blower in this project uses the inlet guide vanes to regulate the flow, which is obviously the best adjustment method.


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