The function, category, working principle, performance characteristics, etc. of the centrifugal fan
The centrifugal fan is a machine that relies on the input mechanical energy to increase the gas pressure and discharge the gas. It is a driven fluid machine. Centrifugal fans are widely used in ventilation, dust removal and cooling of factories, mines, tunnels, cooling towers, vehicles, ships and buildings; ventilation and induction of boilers and industrial furnaces; cooling and cooling of air conditioning equipment and household appliances Ventilation; drying and selection of grain; wind tunnel wind source and inflation and propulsion of hovercraft, etc.
Function: The working principle of the centrifugal fan is basically the same as that of the turbo compressor, both because the gas flow rate is low and the pressure change is small. Generally, there is no need to consider the change of the gas specific volume, that is, the gas is treated as an incompressible fluid.
Category: Centrifugal fans can be made into two types of right-handed and left-handed. When viewed from the side of the motor, the impeller rotates clockwise, which is called a right-handed fan, and the impeller rotates counterclockwise, called a left-handed fan.
Working principle: Centrifugal fans are based on the principle of converting kinetic energy into potential energy. The high-speed rotating impeller accelerates the gas, then decelerates, changes the flow direction, and converts kinetic energy into potential energy (pressure). In a single-stage centrifugal fan, the gas enters the impeller from the axial direction, changes to the radial direction when passing through the impeller, and then enters the diffuser. In a diffuser, the gas changes direction of flow causing a deceleration, which converts kinetic energy into pressure energy. The increase in pressure occurs mainly in the impeller and secondarily in the diffusion process. In a multi-stage centrifugal fan, a reflux device is used to direct the airflow to the next impeller, creating higher pressure.
Performance characteristics: The centrifugal fan is essentially a variable flow constant pressure device. When the speed is constant, the pressure-flow theoretical curve of the centrifugal fan should be a straight line. Due to internal loss, the actual characteristic curve is curved, and the pressure generated in the centrifugal fan is greatly affected by the change of the inlet temperature or density. For a given amount of inlet air, the highest inlet temperature (lowest air density) is generated. 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 a constant speed, for a given flow, the required power increases with the decrease of the inlet temperature raised.
Troubleshooting: Centrifugal fan transmission part wear is a common equipment problem, including exhaust fan bearing, bearing chamber wear, blower shaft bearing wear, etc. For the above-mentioned faults of centrifugal fans, traditional maintenance methods include surfacing welding, thermal spraying, electric brushing, etc., but there are certain disadvantages: the thermal stress caused by high temperature repair welding cannot be completely eliminated, and it is easy to cause material damage, resulting in bending or breaking of parts; However, the brush plating is limited by the thickness of the coating, so it is easy to peel off, and the above two methods use metal to repair the metal, which cannot change the "hard to hard" matching relationship. Wear again. Contemporary western countries often use polymer composite materials to repair the above problems, and the American Fushilan technology system is more widely used, which has super strong adhesion, excellent compressive strength and other comprehensive properties, and can be disassembled and machine-free. processing. There is no thermal stress of repair welding, and the thickness of the repair is not limited. At the same time, the metal material of the product does not have the concession, which can absorb the impact and vibration of the equipment and avoid the possibility of re-wear. It is used in the domestic application of centrifugal fan fault repair It is also gradually replacing traditional methods.