The system of centrifugal construction is an injection radial mechanism, which has the ability to generate pressure of any range. The purpose of such system of a centrifugal fan is represented by the move of single or multi-atomic gases, which include chemical “aggressive” compounds.

The standard design of a centrifugal fan includes a solid metal frame with a shaft. There is an impeller in the form of a wheel with blades on the shaft. The blades are directed at an angle to the shaft itself and the axis of rotation.

The design is covered by a metal/plastic case, known as a protective housing. That shell prevents dust, moisture and other substances from entering, because they can have a negative effect on the machine operation.

The aspiration system contains a control unit, an air cleaning filter, an electric motor and a centrifugal fan.

The mechanism starts working with a help of an electric motor or an internal combustion engine (typical for industrial fans). A widespread method is the electric motor, which rotates the shaft with an impeller. There are some variants of rotational motion from the engine to the blade:

• elastic coupling;
• belt transmission;
• stepless transmission (hydraulic or inductive sliding coupling).

There are two main channels in the case, namely: input and output. The gas mixture, which enters the first channel is fed into the chamber, where its processing is carried out and then directed to the second channel.

The range of use of these fans is wide:

• ventilation and heating systems in private and multistory houses;
• supply and cleaning of air for untenable buildings;
• filtration systems;
• implementation of technological processes in the various spheres of light and heavy industry;
• fire extinguishing systems and ultra-fast exchange of air in a closed space.

The tried and tested simple design of the centrifugal mechanism has the following advantages:

• ease and availability of equipment maintenance;
• safety of operation of aggregates;
• minimal energy and service losses in case of malfunctioning.

Moreover, centrifugal fans have a distinctive low noise threshold, which allows their use in households. If there is no direct collisions of the working parts of the mechanism in the working chamber, they have exceptionally long service life.

Dynamic features include the following technical parameters for the centrifugal fans performance: the generated pressure and differential pressure, the speed and maximum flow temperature, the speed of the shaft, the sound pressure level of efficiency and engine power.

The principle of the working cycle

Let’s consider the general principle of the centrifugal fan of radial construction. In general, we distinguish two basic structures of the fan: the one with the axial and radial placement of the inlet, where the air flow is drawn. The radial type fan interacts with both ordinary and flow air, that are fed through the air duct.

The axial inlet is typical for pressure generators in common use. The radial location of the flow inlet is characteristic of the main use blowers.

At the first stage of the fan operating cycle, the air flow is transported to the surface of the rotating blades. The impellers split the air into small volumes, which are mixed inside the working chamber. Here the accumulation of air mass occurs, that is the compression of the air mass of small volume.

The design of the case has a round or spiral shape. The round shape of the case is typical for fans which transport a large amount of air over a short period of time. While fans with the spiral form additionally contribute to the compression of air volume and the medium and high pressure generation.

At the second stage the air and the gas pressure are pumped inside the working chamber.

The shape and number of blades has a great importance. They are all tested in aerodynamic tubes to determine the operating conditions.

At the final stage, the compressed air is discharged from the working chamber to the outlet. Then the air passes into the central air duct and goes in the indicated direction.

The process of rarefaction is the opposite. The air is taken from an air pipe or a closed space, where is necessary to create a rarefied area and output into the environment or a limited space.

The specification of the centrifugal fan includes:

• the structure of the blower;
• engine type;
• control unit;
• impeller placement and a supply of rotational motion from engine;
• angle of the ingate and exit branch pipe;
• the material from which the parts of the product are manufactured, its dimensions and weight.

Another one important thing is compliance with international standards: ISO/IES and GOST standards, IP marking, ATEX directives.