Centrifugal fans are mechanical machines that rely on the input of mechanical energy to increase the gas pressure and send gas together. It is a driven fluid machine. Centrifugal fans are widely used in factories, mines, tunnels, cooling towers, vehicles, ships and buildings ventilation, dust and cooling; boiler and industrial furnace ventilation and wind; air conditioning equipment and household appliances in the cooling and Ventilation; grain drying and selection; wind tunnel and hovercraft inflatable and propulsion.
Working principle: Centrifugal fan is based on the principle of kinetic energy conversion to potential energy, the use of high-speed rotation of the impeller to accelerate the gas, and then slow down, change the flow, so that kinetic energy into potential energy (pressure). In a single-stage centrifugal fan, the gas enters the impeller from the axial direction, and the gas flows into the radial direction through the impeller and then enters the diffuser. In the diffuser, the gas changes the direction of flow and increases the area of the duct to slow down the airflow, which translates kinetic energy into pressure energy. The increase in pressure mainly occurs in the impeller, followed by the expansion process. In a multistage centrifugal fan, use a refluxor to allow the airflow to enter the next impeller, creating a higher pressure.
Role: Centrifugal fan working principle and turbine compressor is basically the same, are due to low gas flow rate, the pressure change is not, generally do not need to consider the gas specific volume changes, that is, the gas as incompressible fluid treatment.
Centrifugal fans can be made of two types of right and left. From the motor side of the face: the impeller clockwise rotation, known as the right rotating fan; impeller counterclockwise rotation, known as the left rotating fan.
Features: Centrifugal fan is a variable flow constant pressure device. When the speed is constant, the pressure-flow curve of the centrifugal fan should be a straight line, and the actual characteristic curve is curved due to internal losses. The pressure generated in the centrifugal fan is greatly influenced by changes in the inlet temperature or density. For a given intake air volume, the maximum inlet 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 is running at constant speed , The required power increases for a given flow rate as the intake air temperature decreases.
Fault repair: centrifugal fan drive parts wear is often the equipment problems, including the exhaust fan bearing, bearing chamber wear, blower shaft bearing wear and so on. For the centrifugal fan failure, the traditional maintenance methods are surfacing, thermal spraying, brush crossing, but there are some drawbacks: welding heat generated by high temperature can not be completely eliminated, easy to cause material damage, resulting in parts bending or fracture; And brush plating by the coating thickness limit, easy to peel off, and the above two methods are metal repair metal, can not change the "hard to hard" with the relationship, in the combined effect of each force, will still result in plastic drum Wear again. Contemporary Western countries for the above problems and more use of polymer composite materials repair methods, and the application is more of the United States blessing blue technology system, which has a strong adhesion, excellent compressive strength and other comprehensive performance, Processing. Both the effect of welding thermal stress, repair the thickness is not restricted, while the product has the metal material does not have the concession, can absorb the impact of equipment shock, to avoid the possibility of re-wear, in the domestic centrifugal fan repair for the application But also gradually replace the traditional method.
1, the installation of centrifugal fan unit, should be placed directly on the basis of pairs of oblique horn leveling.
2, the scene of the centrifugal fan assembly, the base of the cutting surface should be properly protected, should not have corrosion or operation, the base placed on the basis of the application of pairs of oblique horn leveling.
3, the bearing seat and the base should be tightly engaged, the vertical non-level should not exceed 0.2 / 1000, with the level on the spindle measurement, horizontal horizontal water should not exceed 0.3 / 1000, with the level of the bearing in the level of the surface measuring.
4, the bearing should be measured before the rotor shaft axis and the chassis axis correction, while adjusting the gap between the impeller and the inlet and the spindle and the rear side of the chassis shaft hole between the gap, so that it meets the equipment technology The provisions of the document.
5, the spindle and bearing assembly, the equipment should be the provisions of technical documents to check. Between the bearing cap and the bearing pad should be maintained between 0.03 ~ 0.04 mm interference (measuring the outer diameter of the bearing and bearing the inner diameter).
6, the fan chassis assembly, should be based on the rotor axis as the base to find the location of the chassis and the impeller inlet and chassis inlet between the axial and radial clearance to the equipment technical documents specified range , While checking whether the anchor bolts are tightened. If the clearance value is not specified in the equipment technical documents, the general axial clearance shall be 1/100 of the outer diameter of the impeller. The radial clearance should be evenly distributed. The value should be 1.5 / 1000 ~ 3/1000 Small size). Adjust the value of the gap to achieve a smaller, in order to improve the efficiency of the fan.
7, the fan is correct, the fan shaft and the motor shaft of different degrees of axis: radial positioning should not exceed 0.05 mm, tilt should not exceed 0.2 / 1000.
8, rolling bearing assembly of the centrifugal fan, the two bearing frame on the bearing hole of different shaft degrees, until the rotor installed, to flexible rotation prevail.