Chinese name
centrifugal blower
Foreign name
centrifugal blower
principle
The gas is accelerated by the impeller rotating at high speed.
function
Treat gas as an incompressible fluid.
structure
Comprises a shell, a spindle and an impeller.
quick
navigate by water/air
Development history
development prospect
operating characteristic
Fault maintenance
Matters needing attention
other
principle of operation
Centrifugal fan is based on the principle that kinetic energy is converted into potential energy, which uses high-speed rotating impeller to accelerate gas, then decelerate and change the flow direction, so that kinetic energy is converted into potential energy (pressure). In a single-stage centrifugal fan, gas enters the impeller from the axial direction, becomes radial when flowing through the impeller, and then enters the diffuser. In the diffuser, the gas changes the flow direction, and the increase of the cross-sectional area of the pipeline slows down the gas flow, thus converting kinetic energy into pressure energy. The pressure increase mainly occurs in the impeller, followed by the diffusion process. In the multistage centrifugal fan, the reflux device is used to make the airflow enter the next stage impeller to generate higher pressure [1].
function
The working principle of centrifugal fan is basically the same as that of turbo compressor, because the gas flow rate is low and the pressure change is small. Generally, it is not necessary to consider the change of gas specific volume, that is, treat gas as an incompressible fluid.
centrifugal blower
Centrifugal fans can be made into right-handed and left-handed ones. From the side of the motor: the impeller rotates clockwise, which is called a forward fan; The impeller rotates counterclockwise, which is called left-handed fan.
structure
Centrifugal fan consists of casing, spindle, impeller, bearing transmission mechanism and motor.
Chassis: made of steel plate, solid and reliable, divided into integral type and semi-open type, easy to maintain.
Impeller: It consists of blades, a curved front disc and a flat back disc.
Rotor: Static balance and dynamic balance should be done to ensure smooth rotation and good performance.
Transmission part: it consists of spindle, bearing box, rolling bearing and pulley (or coupling).
Development history
1862, the British Gibel invented the centrifugal fan. Its impeller and casing are concentric circles, the casing is made of brick, and the wooden impeller adopts backward straight blades, with an efficiency of only about 40%, which is mainly used for mine ventilation.
1880, people designed the spiral case of mine exhaust and air supply, and the centrifugal fan with backward curved blades. The structure has been relatively perfect.
1892 France developed a cross-flow fan; 1898, the Irish designed a sirocco centrifugal fan with forward blades, which was widely used in various countries. /kloc-in the 9th century, axial fans have been used in mine ventilation and blast in metallurgical industry, but their pressure is only 100 ~ 300 Pa, and their efficiency is only 15 ~ 25%. It didn't develop rapidly until the 1940s.
1935, in Germany, axial flow constant pressure fan was used for the first time to ventilate and extract air from boilers; 1948, Denmark made an axial fan with adjustable blades in operation; Rotating axial flow fan, meridian acceleration axial flow fan, diagonal flow fan, cross flow fan; In 2002, China's explosion-proof centrifugal fan was widely used in chemical industry, petroleum, machinery and other fields, and Changlindong explosion-proof centrifugal fan was also successfully developed. Centrifugal fan is an auxiliary production equipment commonly used in stone processing enterprises, which is mainly used for ventilation and dust removal equipment, such as cyclone dust collector and bag dust collector in stone cutting and grinding process. In order to ensure the cleanliness of the production environment and protect the physical and mental health of producers, it is necessary to use centrifugal fans to dust the production site. Fan is a kind of equipment with high energy consumption, which consumes a large proportion of power resources in stone processing. With the increasing shortage of energy and the popularization and application of high-yield and high-efficiency working faces in China, energy saving and consumption reduction have become a common concern of stone production enterprises, and many stone production enterprises regard reducing the electrical consumption of wind turbines as an important task at present. To reduce the power consumption of the fan, in addition to improving the efficiency of the fan itself, the most important thing is to choose the adjustment mode of the fan reasonably, because the load of stone production changes with the demand of the process, and most of them
centrifugal blower
The fan needs to adjust the flow frequently according to the load of the host. At present, the energy-saving adjustment mode of fans in stone processing enterprises is relatively old, and throttling adjustment is generally adopted. When throttle regulation is adopted, the flow of the fan is mainly regulated by regulating valve or throttle baffle. Fan throttling is large, even throttling is more than 50% at low load. Because of throttling loss and deviation from high efficiency area, energy waste is very serious. If the speed of the fan is adjusted, it can not only offset the throttling loss, but also ensure that the fan always runs in the high efficiency area, so it can greatly save electricity. It can be said that adjusting the fan speed to run the fan is an effective energy-saving way, which embodies the new trend of current building materials industry production.
development prospect
With the advancement of industrialization in China, the industrial sector is vigorously carrying out energy conservation and consumption reduction, industrial upgrading and integration, and industrial basic equipment needs a lot of updating. As an important supporting equipment for industry, centrifugal fans will be more widely used in electric power, cement, petrochemical, coal, mining, environmental protection and other fields. Under the new economic development situation, the centrifugal fan industry will continue to maintain rapid growth in the future. It is estimated that by 2022, the market scale of centrifugal fan industry will reach 96 billion yuan.
operating characteristic
Centrifugal fan is essentially a variable flow and constant pressure device. When the rotating speed is constant, the theoretical pressure-flow curve of centrifugal fan should be a straight line, and the actual characteristic curve is bent due to internal loss. The pressure generated in the centrifugal fan is greatly influenced by the change of inlet temperature or density. For a given intake air volume, the highest intake air temperature (lowest air density) produces the lowest pressure. For a given pressure and flow characteristic curve, there is a power and flow characteristic curve. When the blower runs at a constant speed, the required power increases with the decrease of the inlet temperature for a given flow rate.
Fault maintenance
Wear of transmission parts of centrifugal fan is a common equipment problem, including wear of bearing position of exhaust fan, bearing chamber and bearing position of fan shaft. In view of the above faults of centrifugal fan, traditional maintenance methods include surfacing welding, thermal spraying, brush welding, etc., but all of them have some shortcomings: the thermal stress caused by high temperature of repair welding can not be completely eliminated, which is easy to cause material damage and lead to bending or fracture of components; However, brush plating is limited by the thickness of the coating and is easy to peel off. Moreover, both the above two methods use metals to repair metals, which can not change the coordination relationship of "hard to hard". Under the comprehensive action of various forces, the cots will still be worn again. In order to solve the above problems, most western countries use polymer composite materials for repair, and widely adopt the American Fu Shi Blue technology system, which has superior adhesion, excellent compressive strength and other comprehensive properties and can be disassembled for processing. Does not affect the welding thermal stress, and the repair thickness is not limited. At the same time, the product has flexibility that metal materials do not have, which can absorb the impact vibration of equipment and avoid the possibility of re-wear. In the application of centrifugal fan fault repair in China, it has gradually replaced the traditional method [2].
centrifugal blower
Matters needing attention
Close the program
1. Emergency stop: During the trial operation of the unit, stop immediately in case of any of the following circumstances. The emergency stop operation is to press the stop button of the main motor, and then carry out the aftermath after stopping.
A, centrifugal fan suddenly strong vibration, and has exceeded the trip value.
B there is scraping sound or abnormal rubbing sound inside the machine body.
C, any bearing or seal smoking phenomenon, or a bearing temperature rises sharply to the alarm value.
D, oil pressure is lower than the alarm value and can't return to normal.
E, the fuel tank liquid level is low, and there has been a suction phenomenon.
F, the axial displacement value appears obvious continuous growth, when it reaches the alarm value.
2. Normal shutdown: The normal shutdown of the unit shall be operated according to the following procedures.
A, gradually open the exhaust valve (or outlet bypass valve), at the same time gradually close the exhaust valve.
B, gradually turn down the intake throttle to 20 ~ 25.
C, press the stop button, and pay attention to whether there is any abnormal phenomenon in the process of stopping.
D oil supply can be stopped after the unit stops for 5 ~ 10 minutes, or when the bearing temperature drops below 45℃. For the unit with floating ring seal, the sealing oil pump must supply oil continuously until the temperature of the machine body is lower than 80℃.
After the unit stops, the rotor should be driven with 180 regularly within 2 ~ 4 hours.