The difference between single stage and multi stage centrifugal fans

The working principle of centrifugal fans is basically the same as that of turbine compressors, but due to the low gas flow rate and little change in pressure, there is generally no need to consider the change of gas specific volume, that is, the gas is treated as an incompressible fluid. Centrifugal fans are based on the principle of converting kinetic energy into potential energy, using a high-speed rotating impeller to accelerate the gas, then slow down and change the flow direction to convert kinetic energy into potential energy (pressure). In a single-stage centrifugal fan, the gas enters the impeller from the axial direction, changes to a radial direction as it flows through the impeller, and then enters the diffuser.

In a diffuser, the gas changes the direction of flow causing a deceleration, which converts kinetic energy into pressure energy. The increase in pressure occurs mainly in the impeller and to a lesser extent in the expansion process. In a multi-stage centrifugal fan, a reflux is used to bring the air flow to the next impeller, generating higher pressures....

According to the working principle, single-stage and multi-stage centrifugal fans belong to a kind of speed fan, that is, first of all, in the process of rotation of the working wheel, due to the action of the rotating centrifugal force and the diffuser flow in the working wheel, the speed of the gas is increased, and then the speed energy is converted into pressure energy in the diffuser. The difference between the two is that the single-stage centrifugal fan has only one set of impellers, and the compression of air is completed at one time, while the multi-stage centrifugal fan has multiple sets of impellers on one main shaft, and the compression of air is gradually completed between multiple groups of impellers. Because the centrifugal fan relies on increasing the flow speed of the air, that is, the kinetic energy of the air to compress the air to increase the pressure, so to obtain the same pressure, the impeller of the single-stage centrifugal fan must be dozens of times higher than the speed of the multi-stage fan, usually the speed of the multi-stage fan is only a few thousand revolutions, while the speed of the single-stage fan is as high as tens of thousands of revolutions or even as high as hundreds of thousands of revolutions.

Because the supply of pressure largely depends on the increase of speed, and the supply of speed is limited by balance, lubrication and material properties, single-stage centrifugal fans are more used in low-pressure occasions, while multi-stage centrifugal fans are more used in high-pressure conditions. Single-stage centrifugal fan generally relies on the gearbox to obtain extremely high speed, because the speed is particularly high, so the control and maintenance of the fan is particularly important, must be equipped with a separate lubricating oil station at the same time, at the same time, due to the high speed brings many components such as blades and other wear and tear, so the life of the unipolar fan is more than the centrifugal fan is low.

The multi-stage centrifugal fan is formed by a motor driving a centrifugal fan, and the centrifugal fan here is composed of multiple impellers combined in series as the main body, and support bearings are arranged at both ends of the impeller group, and the cooling is carried out by natural cooling. However, if the pressure in the multistage centrifugal fan exceeds 200kPa, it has to rely on the forced lubrication system to maintain a stable working state.

From a structural point of view, the core of the multi-stage centrifugal fan is the impeller group, the angle of the impeller blades is the key to the formation of wind pressure, so it is necessary to use a reasonable angle to locate the blades, and design its width and arc according to the size of the flow requirements. When installing, the slightly wider impeller is usually installed at the air inlet end, and the narrow impeller is installed at the air outlet end, so as to ensure the stability of the air pressure.

In order to ensure the smooth operation of the multi-stage centrifugal fan, it must be kept balanced by the balance plate, which will delay the service life of the fan bearing and obtain good operating conditions for the fan. In addition, the casing, tuyere, sealing system and muffler are also indispensable components of multistage centrifugal fans.

The casing of the multi-stage centrifugal fan adopts the production method of sand turning parts or weldments according to the requirements, and is designed into an integral small section, and then formed by the superposition of multiple sections, so that the casing has high strength. The air inlet and outlet of the multi-stage centrifugal fan are basically made of national standard round flanges, which fully meet the actual application requirements.

The combination seal is used between each stage impeller and the extension end of the shaft of the multi-stage centrifugal fan, which has the outstanding advantages of good sealing, compact structure, and easy and quick replacement. The muffler is the standard configuration of the multi-stage centrifugal fan, which is set at the front end of the inlet, outlet and venting device respectively, which effectively reduces the noise of the inlet and outlet air duct.

Centrifugal fan inverter, only need to choose the general inverter, so that the rated current of the inverter is greater than the rated current of the supporting motor.

Centrifugal fan is a machine that relies on the input mechanical energy to increase the gas pressure and discharge the gas, and it is a driven fluid machine. Centrifugal fans are widely used for ventilation, dust removal and cooling in factories, mines, tunnels, cooling towers, vehicles, ships and buildings; ventilation and induced air for boilers and industrial furnaces; cooling and ventilation in air-conditioning equipment and household appliances; drying and selection of grains; Wind tunnel wind source and hovercraft inflation and propulsion, etc.

Centrifugal fan is based on the principle of converting kinetic energy into potential energy, using a high-speed rotating impeller to accelerate the gas, and then decelerate and change the flow direction to convert kinetic energy into potential energy (pressure). In a single-stage centrifugal fan, the gas enters the impeller axially, changes to radial as it flows through the impeller, and then enters the diffuser. In a diffuser, the gas changes the direction of flow and the pipe cross-sectional area increases to slow down the air flow, and this deceleration converts kinetic energy into pressure energy.

The increase in pressure occurs mainly in the impeller and to a lesser extent in the expansion process. In a multistage centrifugal fan, a reflux is used to bring the air to the next impeller, creating a higher pressure.

We usually choose 3kw inverter. Leave a margin, not necessarily one level larger.

Centrifugal fan equipment supporting inverter, only need to choose the general type (fan pump) inverter, so that the rated current of the inverter is greater than the rated current of the supporting motor, can not only be based on power, because the general inverter power is considered according to the four-level motor, so the current should be compared. Motors below the fourth level can be selected according to the matching motor power.

You can choose the P series inverter (special for fans and pumps) to be one level smaller than the general one, why choose a larger one?

The fan is mainly widely used in various smelting boilers, coal washing plants, mine flotation, sewage treatment, chemical gas production and other occasions that need to leak Zen to convey air, and can also be used to transport other non-corrosive gases, such as blast furnace air supply, sewage treatment aeration blast defeat search wide, coke oven gas, shaft furnace sintering air supply, etc.

The multi-stage centrifugal fan is a multi-stage, single-suction, double-support structure, which is composed of a rotor, a casing, an air inlet, an air outlet, a bearing seat, a sealing group, a loud noise eliminator, a motor, and a control system. The electric motor and blower are mounted on the base, and the coupling is directly driven between the two.