Types of fans: classification, purpose and principle of their operation

A fan is the basis of any artificial ventilation system. The device is widely used in everyday life and is indispensable in many areas of human life. When planning a purchase of ventilation equipment, you need to understand the specifics of its device and action.

The article presented for familiarization describes in detail the types of fans, their design features, operating principles and the purpose of each unit. We will tell you about the priority areas for choosing the right model. Here you will learn how to select a device depending on operating conditions.

Fan classification by main parameters

Fans - mechanical devices designed to move, supply or exhaust air and gas masses. Air circulation occurs due to the pressure difference between the inlet and outlet channel of the ventilation unit.

Fans are used everywhere. Indispensable appliances in the arrangement supply and exhaust ventilation complex buildings, blowing working elements in air conditioners and heating devices.

Fans are designed to work with gases, the compression ratio of which does not exceed 1.15. In this case, the difference in the pressure indicators at the inlet / outlet is limited to 15 kPa - at a higher rate, a compressor is used

The general classification of ventilation units is based on various parameters.

Among the main criteria for gradation are:

• design and operation of the device;
• purpose and conditions of operation of the fan;
• installation method;
• methods for connecting the device to an electric motor;
• technical features: IP degree of protection, generated pressure, power consumption, speed, efficiency and acoustic pressure level.

Five types of fans are distinguished by the type of design: axial, centrifugal, diagonal, diametrical and bladeless.

Diagonal and diametrical units are considered a variety of two main groups of ventilation units: axial and centrifugal. New bladeless products are fundamentally different from their counterparts

Based on operating conditions, the following types of gas blowing machines are divided:

• general use devices;
• special purpose fans.

The first group includes units designed for work with air and inactive gas flows, the temperature of which does not exceed + 50 ° С. The second group includes special equipment: heat-resistant, explosion-proof, dustproof, corrosion-resistant and smoke-removing.

According to the installation method, they distinguish:

• standard - installation is carried out on a support;
• roof - installation on the roof of the building;
• ducted - placed inside the ventilation duct;
• multizone - models designed to connect to multiple air channels.

Electric motors are used as the drive of the ventilation unit.

There are several ways to couple the engine with the impeller:

• direct connection;
• V-belt drive
• stepless coupling.

After determining the appropriate type of fan, a model with optimal technical characteristics is selected.

The service area, installation location, permissible noise level, room humidity, the need to protect the device from foreign objects are taken into account

The principle of operation of different types of devices

The main criterion for choosing a fan is its device and principle of operation. Design features and technical nuances determine the efficiency of the device, the noise level, the efficiency of the work and the possibility of its use in certain conditions.

Axial Assembly - Classic Fan

Axial (axial) fan is widely used in household ventilation systems of private houses, in bathroom hoods, in complex exhaust versions, as an element of cooling for various equipment and electronics, as well as in wind tunnels and turbofan engines in the field of aviation.

The design of the models is characterized by ease of execution and small dimensions. The main elements: a cylindrical body, a wheel with blades and a drive. The inner diameter of the cylinder must ensure unobstructed rotation of the impeller. The interval between the blades and the body is limited to 1.5% of the length of the rotating blade.

In order to reduce hydraulic losses and improve aerodynamic characteristics, the design is supplemented by a collector, a diffuser and a fairing on both sides of the impeller

Principle of action: rotating blades capture air and push it along the axis of the impeller. The movement of air flows in the radial direction is almost absent.The performance of the equipment is regulated by the rotation of the blades.

Distinctive features of axial models:

• do not require a large area for installation;
• economical energy consumption;
• low noise level;
• simplicity of operation and repair;
• low cost.

The advantages of working and using axial fans have made them widely popular in everyday life. Housing models for cooling electrical appliances and portable axial units with a grill are widely used.

To enhance air exchange, axial fans with a wall panel are installed in wall openings and other supporting structures. Devices are able to function in two modes: air suction and air injection

Centrifugal Model - Strength and High Power

Centrifugal (radial) fans are highly efficient - the units are able to generate high pressures and operate in harsh conditions. The design of the equipment includes the following elements.

Body. The diffuser housing is made of sheet metal riveted or welded. The hollow body has a spiral shape of a cochlea; the design provides for suction and discharge pipes. To give rigidity, the casing is reinforced with ribbing or transverse stripes.

From above, the "snail" is closed with an additional box or sheathed with noise-absorbing panels. This is necessary to reduce noise during operation of the ventilation unit.

Working wheel. The rotor blade consists of two discs, blades and a hub.

The design of the wheel determines the conditions for using the fan:

• diskless - transportation of streams with solid components;
• single-disk - the movement of air with a low content of solid fractions;
• double-disk - circulation of pure air masses in a different pressure range;
• three-disk - providing two-way suction.

The wheel is attached to the shaft by means of hubs. Blades are fixed to the discs and hubs.

Shoulder blades. The performance and efficiency of the unit as a whole largely depend on the shape of the blades:

• aerodynamic wing - provides noiselessness, a good performance indicator, the instrument's resistance to high temperatures;
• curved back - prevent the accumulation of dust inside the fan, suitable for operation in an environment with high depression;
• curved forward - fans with “front” fins are designed to work with a large volume of air and high pressure, are resistant to erosion;
• radial - installations of compact sizes with medium efficiency, rotor guides are treated with a protective composition against erosion.

In wheels with "rear" blades, the difference between the static and total pressure indicators is not large, therefore their efficiency level is high. Efficiency reaches 80%.

Forward, the bent blades create a high air velocity at the outlet. The unit retains 60% efficiency. Plus “front” blades - getting the right parameters with smaller fan dimensions

In centrifugal plants, air enters in the axial direction, is pushed out in the radial direction. Air masses under the action of centrifugal forces move in a cylindrical body.

The whole process can be divided into several stages:

1. When the wheel rotates, the air between the space of the blades rushes to the edge of the rotor.
2. As a result, a low pressure zone forms in the center of the wheel. This leads to the absorption of air masses from the outside.
3. In the center of the chamber, the air flows change direction from axial to radial, entering the compartments between the blades.
4. Due to the rapid rotation of the air mass rush to the inner wall of the housing.
5. Kinetic energy is partially converted into compression energy and the air velocity decreases - a volume air flow is collected inside the “cochlea” and excess pressure is generated.
6. The gaseous mass rushes to the outlet pipe, enters the pipeline, and then into the working area.

Centrifugal units are used in supply and exhaust systems of large premises, garages, shopping centers and buildings, where continuous powerful ventilation is required.

Radial plants are used in hazardous industries to quickly remove contaminated air. For example, in wood or metal workshops, in workshops for extracting smoke and harmful fumes

Diagonal - combination of axial and radial fan

The diagonal model is a synthesis of two types of fans: axial and centrifugal. The impeller of the device has a special shape - the structure of the impeller resembles a drum device in a radial fan. Impeller blades are parallel to the axis of rotation.

Combined fans have a cylindrical body and look more like axial models. However, the principle of operation is different due to the design features of the impeller. The air first moves along the axis, and then changes its direction by 45 °.

Due to centrifugal injection, the air flow rate increases, which means that the efficiency of the ventilation unit also increases. The efficiency level of diagonal models reaches 80%

The main advantage of a mixed-type fan is to achieve a compromise between noise characteristics, performance and dimensions of the device.

Most often, centrifugal axial units are used as duct fans in small and medium ventilation systems with long ducts. They are used as exhaust systems and inlets in pressure systems of the supply type.

Tangential installation - uniform air flow

The tangential (diametrically) fan consists of an elongated body equipped with a diffuser and a nozzle, and a drum-type impeller with inclined blades. Twice the movement of air perpendicular to the axis of rotation of the cylinder.

The casing of the diametrical model resembles the case of a radial fan. The difference is that in the tangential unit, the duct is located along the side panel

Distinctive features of diametric devices:

• high aerodynamic performance;
• ability to supply uniform flow;
• the ability to expand the fan, choosing the direction of the air flow;
• silent operation;
• high rate of efficiency - up to 60-70%.

Scope: creation of air curtains, fancoils and use in split systems.

Fanless fan - innovative technology

Household fanless fans appeared on the domestic market of ventilation systems not so long ago. Their principle of operation is fundamentally different from the above modifications.

The action of the innovative device is based on the desire of the medium to equalize the balance between the pressures outside and inside the device, as well as on the technology of the “air multiplier”

Components of the device:

• a round or oval frame designed to draw in and release air masses;
• base for fixing the frame;
• mini-turbine mounted in the fan base;
• motor.

The innovative fan works according to this principle:

1. After turning on the motor, the turbine is driven.
2. Rotating, the turbine draws air through perforations in the base body.
3. Under the influence of turbulence, air accelerates 15 times and exits through exit slots located around the perimeter of the frame.

Air flows around the surface of the ring, and rush in the right direction.

Due to the aerodynamic properties of the ventilation device, air is drawn into the air flow from the side and behind the annular frame

Compared to traditional models fanless blades have several advantages:

• smooth adjustment of airflow intensity;
• convenience and absolute safety of use;
• change in air direction by adjusting the position of the ring;
• work efficiency - electric power consumption is 20% less in comparison with axial models.

The main disadvantages of the device: high cost and high noise level.

Depending on operating conditions

When choosing a fan, it is important to consider the conditions for its use. For use in an aggressive environment, highly specialized installations have been developed.

Units for use in normal conditions

General purpose fans are made of carbon steel.

Devices are permissible for installation subject to the mandatory operating conditions:

• dust content in the air for radial units - not more than 0.01 g / m3, for axial devices - up to 0.01 g / m3;
• medium temperature - up to + 50 ° С;
• lack of chemically aggressive, explosive components, fibers and sticky particles in the air.

The gas-vapor medium should not provoke accelerated corrosion processes; the allowable rate of metal destruction is 0.1 mm per year. If the operating temperature rises above the limit value, the operation of the engine, which is usually located in the flow of transported air masses, deteriorates.

There are steel heat-resistant general-purpose fans. The maximum temperature of the transported composition is up to + 200 ° С. Domestic products are marked with the letters "Ж" and "Ж2"

General purpose models used in systems air heating and ventilation of public, residential and industrial buildings, as well as for other sanitary purposes.

Special Purpose Ventilation Units

Special-purpose fans are usually divided into five groups:

• dust;
• heat resistant;
• explosion proof;
• corrosion resistant;
• smoke removing.

Dust aggregates are used to clean air masses from dust and particles of dirt: wood and metal sawdust, welding slag, grain waste. The air flow passing through the nozzles changes its direction from axial to radial. Due to centrifugal force, the air flow rate also changes.

Dust devices are made of brass, carbon or stainless steel. The maximum temperature of the working medium is + 80 ° C. There are mixed types of models: dust, explosion-proof and heat-resistant

Low power radial dust fans are installed on vehicles transporting grain trains. High pressure devices are used in large production halls.

Heat-resistant units are designed to move air whose temperature exceeds + 80 ° C.

Due to harsh operating conditions, fans must have special characteristics:

• thermal insulation of the electric motor and its removal beyond the air flow;
• high level of engine protection - IP44 and higher;
• manufacturing of structural elements from heat-resistant materials (heat-resistant polyamide, aluminum alloy, stainless or carbon steel);
• wide range of operating temperatures.

Heat-resistant fans are used in the arrangement bathtub ventilation systems and saunas, removal of high-temperature exhaust air from a fireplace or stove, removal of combustion products from production sites.

Heat resisting units can have axial or radial execution. Most often, high-temperature fans are used in ventilation ducts, but there are modifications that are mounted without ducts

Explosion-proof ventilation equipment is designed for the removal of explosive gas mixtures. This category includes compositions in which, upon ignition of the smallest particle, the entire remaining volume of gas ignites.

Explosion protection requirements for electrical equipment are regulated by ATEX EC directives.Depending on the degree of explosion hazard of the zones, ventilation units can be protected:

• quartz or oil filling of the shells of the conductive parts;
• compound sealing - polymer material;
• flameproof coatings.

Stainless steel, aluminum alloys and groups of dissimilar materials are stainless steel, brass, bronze, and electrically conductive plastic.

Dissimilar materials are combined in such a way that a spark could not occur upon impact or friction

Corrosion-resistant fans are designed to transport aggressive non-explosive air-gas mixtures with a low dust content, as well as the absence of fibrous and sticky components.

Materials for the manufacture of parts of the device: titanium alloys, polypropylene, vinyl plastic. Alternatively, the working elements are sprayed with an anti-corrosion coating - corrosion-resistant steel grade 08X13 or titanium alloy.

Scope of "anti-rusting" fans:

• ferrous metallurgy;
• mineral fertilizer production lines;
• carbon production;
• air supply to boilers with boiling composition;
• organization of the circulation of water vapor with impurities of phenol, alkali and hydrogen sulfide;
• lines of coke plants.

Smoke exhaust fans are powerful refractory installations that are built into the building's ventilation system and work by blowing smoke from the room. Units are subject to high technical requirements.

In case of fire, the fan must operate non-stop for 2 hours at a temperature of blown air up to + 400 ° С. When the temperature rises to + 600 ° C - up to 1 hour

Scope - smoke ventilation systems for buildings for various purposes. "Smoke exhausters" are installed on the roof of the room using the mounting flange and are connected to smoke exhaust ducts.

Depending on the design of the fan, two- or four-sided smoke can be emitted in the horizontal or vertical direction. The possibility of functioning of the units in the mode of general ventilation at home is provided.

Types of fans by installation method

As indicated above, according to the installation method, ventilation devices are divided into 4 groups: standard, roof, duct and multi-zone.

Conventional fans usually come with a support frame or holder. Their installation does not cause any difficulties.

Roof units are installed on the roof of the building and act as the final link in the ventilation system of the building. Such fans are exposed to negative external factors (rain, snow, gusts of wind), therefore they are made of especially durable materials. Almost all models are equipped with a protective cone to prevent clogging of the case.

Roof ventilation devices operate on an axial or centrifugal principle. The first option is often used for normal environments, and the second for dusty and aggressive

When choosing a roof fan, take into account the specifics of the premises to be equipped. For example, a model with a low noise level is selected for a kindergarten, hospital or school. For the production hall, equipment power is a priority.

Ducted ventilation units are located in the ventilation ducts and extract and supply air through the duct system. The design of duct fans is usually of a diagonal or radial type, less often an axial one.

The choice of the device is carried out with reference to the shape of the duct. Units for round, square and rectangular shafts are produced.

Rectangular or square duct fans are made of metal, round - of plastic. The metal casing is durable and durable, while the plastic casing is less noisy

Multizone ventilation units are equipped with a housing that allows you to connect several suction ducts that come from different zones. Such fans are indispensable in rooms where it is necessary to equip the hood in different rooms, and there is only one exhaust duct.

Multichannel units allow you to optimize the complex of air ducts, reduce capital costs and the complexity of the work to equip the ventilation system at home

An added benefit is simplified operation. It is necessary to service one, but not several fans.

Varieties of household ventilation models

Domestic fans are further classified by location.

Window. The device is mounted in a window or wall near the window, there is no air duct. Such equipment is mainly used in public institutions: cafes, hairdressers, etc. Self-tapping into installed PVC windows is problematic.

Window fans are made with a round and square profile. Some models are equipped with a check valve to prevent dust from entering the housing.

Kitchenware. Remove fumes and various odors that occur during cooking. The fan is mounted directly in the exhaust hood. Based on the design, there are flat, domed and built-in hoods. Kitchen fans must be heat resistant and have an external protective mesh.

Equipment for the bathroom. To increase exhaust efficiency toilet and bathroom ventilation overhead wall and ceiling fans are used. Compact units are economical and easy to install.

The inner part of the housing is placed in the ventilation duct, and the outer protrudes and closes with a ventilation grill. In the bathroom, it is advisable to use a fan with a water sensor

Regardless of the type of fan selected, particular attention should be paid to the labeling of the device, namely the degree of protection IP. The IP standard characterizes the security of equipment in a non-aggressive environment.

The first digit has a value in the range 0-6 and indicates the level of protection against the penetration of foreign objects, dust and contact with hands

The level of protection against moisture entering the enclosure is indicated by the second digit of the marking.

High probability of penetration of water into devices with a value of "0". They are permissible for installation only in "dry" rooms. The highest degree of protection "8" guarantees the safety of the fan when completely immersed in water

Conclusions and useful video on the topic

Video # 1. The principle of operation and competitive advantages of a bladeless fan:

Video # 2. The device of the centrifugal fan VTsUN:

Video # 3. Round fan duct design:

Model design and technical and operational characteristics of the fans allow you to choose the best equipment for both domestic and industrial use. The design of ventilation units is constantly being improved, adapting to the needs of customers.

Have questions in the process of getting acquainted with the article? Want to tell us about the nuances that are useful in choosing equipment? Please write comments in the block below.