The difference between centrifugal fan, axial fan and mixed fan
So what is the centrifugal fan, axial flow fan, mixed flow fan!
1. Centrifugal fan relies on the input mechanical energy to improve the gas pressure and send gas side-by-side. It is a driven fluid machinery. Centrifugal fans are widely used in: ① factories, mines, tunnels, cooling towers, vehicles, ships and buildings of ventilation, dust removal and cooling; (2) Ventilation and ventilation of boilers and industrial furnaces; (3) Cooling and ventilation in air conditioning equipment and household electrical equipment; (4) Drying and selection of grains; (5) Wind tunnel, wind source and hovercraft aeration and propulsion.
2. 2. Axial flow fan is the air flow in the same direction as the axis of the wind blade, such as the electric fan, and the fan outside the air conditioner is the axial flow fan. It is called "axial flow" because the gas flows parallel to the fan axis. Axial fans are usually used in situations where the flow requirement is high and the pressure requirement is low. Axial fans hold the air in place and move it. Features: Small axial fan: low power consumption, fast heat dissipation, low noise, energy saving and environmental protection. Because of its small size, it is widely used. Large axial fan: has the characteristics of simple structure, stable and reliable, small noise, large air volume, wide selection of functions, etc
3. 3. Oblique flow fan/mixed flow fan is a fan between axial flow fan and centrifugal fan. The impeller of the oblique flow fan makes the air move in both centrifugal and axial directions. A combination of axial and centrifugal fan features, although it looks more like a traditional axial fan. Weld the curved plate blade to the conical steel hub. The flow rate is changed by changing the blade Angle in the upstream inlet housing of the impeller. The housing may have an open inlet, but more commonly it has a right-angle bend shape that allows the motor to be placed outside the pipe. The discharge shell expands slowly to slow the flow of air or gas and convert kinetic energy into useful static pressure. Mainly used for mine ventilation and tunnel ventilation. Difference: 1. Centrifugal fan changes the flow direction of the medium in the air duct, while axial fan does not change the flow direction of the medium in the air duct; 2, the former installation is more complex. 3, the former motor and the fan are generally connected through the belt driven rotating wheel, the latter motor is generally in the fan; 4, the former is often installed in the air conditioning unit inlet and outlet, boiler drum, induced draft fan, and so on. The latter is often installed in the air duct, or the front end of the air duct outlet. 5. The former is pressurized after air income, and the latter is driven by positive pressure.
4. Oblique flow (mixed flow) fan: 1, the wind pressure coefficient is higher than the axial flow fan, the flow coefficient is larger than the centrifugal fan. 2. Fill the gap between axial fan and centrifugal fan. 3. Simple and convenient installation. The difference between centrifugal fan and axial fan at startup: the running power of centrifugal fan increases with the increase of air volume, so the valve of centrifugal fan should be completely closed when starting, and then gradually opened, to avoid the fan current is too large and burn down the motor. The running power of axial fan decreases with the increase of air volume, so when the axial fan is started, the damper should be fully opened, and then gradually closed to the required air volume value.
5. The role of axial fan and centrifugal fan in mechanical ventilation: 1. Due to the large difference between air temperature and grain temperature, the first ventilation time should be selected in the daytime, so as to reduce the gap between grain temperature and temperature and reduce the occurrence of dew. After the ventilation as far as possible in the evening, because the ventilation is mainly cooling, the night humidity is relatively high, the temperature is low, which reduces the water loss, and make full use of the low temperature at night, improve the cooling effect. 2. In the early stage of ventilation with centrifugal fan, condensation on doors, Windows and walls may occur, and even slight condensation on the surface grain surface. As long as you stop the fan, open the window, open the axial flow fan, turn over the grain surface when necessary, and remove the hot and humid air in the warehouse from the outside of the warehouse, you can do it. When the axial fan is used for slow ventilation, there will be no condensation phenomenon, only the middle and upper grain temperature will rise slowly, and the grain temperature will decline steadily as the ventilation continues. 3. When the axial fan is used for slow ventilation, because the air volume of the axial fan is small and the grain is a bad conductor of heat, slow ventilation of individual parts is easy to occur in the early stage of ventilation, and the temperature of the whole warehouse grain will gradually balance as the ventilation continues. 4, the advantages of slow ventilation with axial fan: good cooling effect; Low unit energy consumption, in the advocacy of energy saving today is particularly important; Ventilation time is easy to master, not easy to appear condensation; No separate fan, convenient and flexible. Disadvantages: due to small air volume, long ventilation time; The effect of precipitation is not obvious, and it is not suitable to use axial fan for ventilation in high moisture area. 5, the advantages of centrifugal fan: cooling, precipitation effect is obvious, short ventilation time; Disadvantages: high energy consumption per unit; Ventilation timing is not good and condensation is easy to occur.