Fans are the foundation of any ventilation system. Such devices are widely used in everyday life, you can not do without them in many areas of human activity. Also, devices are actively used in automotive technology, in computers, in welding machines. In our article we will talk about what types of fans exist, learn about design features, purpose, consider the principle of operation of each type of device. Based on this, you can find out which type is best used in a particular case.
The main features of the fans
Fans are mechanical type devices that are designed to supply, move or suck out gas and air masses. Air circulates due to the fact that there is a pressure difference between the input and output of the installation. Fans are used almost everywhere. They are simply indispensable in the manufacture of supply and exhaust ventilation, in stoves, air conditioners.
Only fans with gases with a compression ratio of not more than 1.15 are used. Moreover, the pressure difference between the input and output is not more than 15 kPa. If you need to increase this figure, you will have to use a compressor. The main criteria for fans can be distinguished:
- The principle of operation and design of the device.
- Mounting method.
- Features of functioning and purpose.
- Variant of an impeller drive from an electric motor.
You can also highlight some technical features, in particular, injection pressure, degree of protection, maximum power consumption, efficiency, rotation speed, degree of acoustic pressure. When installing the fan on the Gazelle, you must follow the safety rules - the engine must be connected to the mains correctly.
Fan designs
There are only five design options. Centrifugal, axial, diametric, diagonal and bladeless designs. Moreover, it should be noted that there are fundamental differences only in bladeless structures. Diametric and diagonal fans are a type of centrifugal and axial fans, respectively. When installing a radiator fan on a car, difficulties may arise - measures to protect devices have not been followed. Let's look at the types of fans.
You can select the following type of machine:
- Devices for general use.
- Special Purpose Devices.
The first group includes fans that are designed to work with active gas and air flows, in which the temperature is not more than 50 degrees. As for the second group, it uses special equipment. In particular, the elements are all heat-resistant, corrosion-resistant, explosion-proof, which allows the device to be used in hazardous conditions.
Mounting options
There are several options for installing fans:
- Standard designs are mounted on poles.
- Roof fans are placed on the roof of buildings.
- Multizone devices are models that are designed to connect to multiple channels at once.
- Duct fans are installed inside the ventilation ducts.
When installing a duct fan, it is important to consider the degree of protection so that large suspended particles do not enter it. For the most part, the ventilation unit is driven by an electric motor. There are several options for connecting the motor and the impeller:
- Stepless coupling.
- Belting.
- Direct connection.
A specific fan model should only be selected after determining the type of device. It is necessary to take into account the area that the device will service, the installation location, the maximum permissible noise level, the need to protect the device from various objects, dust, and room humidity. Separate requirements for devices that are installed in cars. It is advisable to install fans that are recommended by the manufacturer.
Classic axial fans
It is also called an axial fan, it is used in the design of household hoods, as well as in complex systems. Such devices can be found in cooling systems of various electronics, in wind tunnels, in aircraft. The design of the model is simple, its dimensions are minimal. The design is based on a cylindrical housing, an electric drive and a wheel with several blades.
The inner diameter of the cylindrical body must be such that the impeller rotates freely. Between the blades and the body, the interval should be about 1.5% of the length of the blade. In order to reduce hydraulic losses and improve aerodynamic performance, a diffuser, collectors, fairing are added to the design.
The principle of operation of the axial fan
The principle of action is that the blades that rotate capture air, and then push it along the axis of the impeller. Air flows in the radial direction practically do not move. To adjust the fan performance, you need to set the desired angle between the impeller and the blades. Be sure to take all these points into account when installing an axial fan.
Features of axial fans:
- They do not require a large area during installation.
- The device consumes little electrical energy.
- Fans are easy to operate and repair.
- They make little noise.
- The cost is not very high.
All these advantages allowed the axial fan to penetrate into all spheres of life. They are widely used in everyday life, automotive technology. In order to enhance air exchange, a device with wall panels can be installed in wall openings and other supporting structures. Devices can work in one of two modes - forcing or air suction.
Centrifugal fan type
The efficiency of this type of fan is very high. These units can generate very high pressure. And operation can be carried out in very difficult conditions. It is hollow, made in the shape of a snail. It has a discharge and suction nozzles. In order to provide the necessary degree of rigidity, the casing is manufactured with transverse stripes or ribs. As a rule, the casing is reinforced by welding.
Noise-attenuating panels are installed in the "snail". This is necessary in order to reduce noise during operation of the installation. The rotor is made of blades, two discs and a hub. The design of the impeller determines the conditions for its use:
- If it is necessary to transport air flows with solid particles, it is best to use diskless devices.
- If air flows with a low solids content need to be moved, single-disc fans are recommended.
- Double discs are suitable for moving air in different pressure ranges without solids.
- By means of three-disk fans it is possible to provide bilateral absorption.
Features of the location of the blades
The wheel on the rotor is fixed using hubs. Blades are mounted on discs and hubs. The effectiveness of the entire unit, as well as its performance, depends on the shape of the blades:
- If they are bent backwards, this will prevent dust from accumulating inside the unit. Therefore, you can use these devices in conditions where there are a lot of suspended particles in the air.
- If the blades are curved forward, this means that the fans can operate under high pressure and with large volumes of air. They are very resistant to erosion.
- Radial fans have compact dimensions, but average efficiency. The rotor elements in them are processed using protective compounds.
- The aerodynamic wing can provide maximum noiselessness, as well as fairly good performance indicators. Devices are resistant to high temperature.
How does a centrifugal installation work?
Suction on these fans occurs in the longitudinal direction, in radial flows they collide. Air masses move in a cylindrical housing. You can break down the entire process into the following steps:
- The air between the blades during rotation of the impeller tends to the edge of the rotor.
- In the center of the wheel, a zone forms in which the pressure is lower than around. This provokes air intake from the outside.
- In the center of the chamber, the air flow changes direction, it moves not in the axial, but in the radial direction. At the same time, it enters the zones between the blades. Due to the fact that the impeller rotates quickly, air rushes to the inner wall of the device.
- In this case, the kinetic energy goes into compression, the air speed decreases. In the cochlea, volumetric air flow is collected, and overpressure appears.
- The air tends to the outlet pipe, then goes to the pipeline and the working area.
Such units are used in supply and exhaust systems for garages, large rooms, shopping centers. In other words, where it is necessary to carry out continuous powerful ventilation. Radial fans are used exclusively in hazardous industries to remove contaminated air as quickly as possible.
Diagonal fans
These are designs that have taken all the best from a centrifugal and axial fan. They have a special shape. The impeller is similar in design to a drum that is used in a radial design. The blades on the impeller are located strictly parallel to the axis of rotation. Such devices are enclosed in a cylindrical housing, they look more like axial ones, but the principle of operation is different due to the fact that the impeller has design features.
Air begins to move along the axis, after which it changes direction by about 45 degrees. Due to the fact that centrifugal injection occurs, the flow rate increases. This means that installation efficiency is improving. The efficiency of diagonal fans is about 80%. Among the advantages of such designs can be distinguished that they have small dimensions, low noise, high performance.
Such devices are used in medium and small ventilation systems, in which a large length of ducts. Regardless of the length of the ducts, the cost of installing the fan will be the same - remove the old 100-200 rubles, put and connect a new one - 1000-1500 rubles. It depends on the particular company. Replacing the fan on cars will cost 500-1000 rubles, depending on the brand. If necessary, a fan sensor is installed - for cars, this will require draining the liquid, so the cost of work increases.
Tangential settings
They are also called diametrical. They are made of a long body on which the nozzle and diffuser are installed. The design also has an impeller in the form of a drum with inclined blades. During operation, the air mass moves twice at an angle of 90 degrees to the axis of rotation.
The casing of this type of fan is about the same as that of radial fans. That's just the duct is along the side panel. The following device features can be distinguished:
- The flow is as uniform as possible.
- High dynamic performance.
- You can expand the device to select the flow direction.
- Coefficient of performance from 60 to 70%.
- It works almost silently.
All these features allowed the use of fans in split systems, air conditioners, to create air curtains.
Fanless fan
Household fans of this type appeared on the market not so long ago. The work differs significantly from those devices that were discussed above in the article. The device works due to the fact that the medium seeks to equalize the balance between the pressure inside and out. You do not need to install an additional fan.
The design of the device consists of the following elements:
- A round or oval frame that is designed to eject and draw in air.
- A miniature turbine located at the base of the fan.
- Elements for fixing the frame.
- Electric motor
The operation of the fan is as follows:
- As soon as the electric motor turns on, the turbine begins to move.
- Through perforation in the casing, the turbine draws in air.
- Due to turbulence, air is accelerated by about 15 times. It exits through slots that are located around the perimeter of the frame.
- Air flows bend the entire surface of the ring, after which they tend to move in the necessary direction. Due to the aerodynamic properties of the devices, air is drawn into this stream from the side of the annular frame.
Vaneless fans have the following advantages:
- The most smooth adjustment of speed of an air stream.
- The device is convenient and safe.
- When adjusting the position of the ring, you can change the air direction.
- Compared with axial, the flapless power consumption is about 20% less.
But there are also disadvantages. These include a very high noise level and cost. When installing this type of supply fan, you will have to spend a large amount.
Household fans
Fans that are used in everyday life can be classified by the place in which they are installed. There are window devices that are mounted in window leaves or in the wall near the window. In such devices there is no duct. Typically, this type of equipment is used in hairdressing salons, cafes, and other public places.
It is worth noting that it is quite problematic to embed such devices into metal-plastic windows on their own. Window-type fans can be either square or round. On some models you can find check valves that prevent dust from entering the room.
Kitchen fans allow you to remove any odors and fumes that occur during cooking. The fan is installed in an exhaust hood. There are built-in hoods, flat and domed. The requirement for kitchen fans is one - they must be heat resistant. They should also have an external protective net.
By installing fans in the bathroom and toilet, you can get rid of odors and high humidity. In order to increase the efficiency of exhaust ventilation in the bathroom and toilet, false ceiling or wall fans are used. The devices are compact, economical enough, and most importantly - very easy to install. The inner part is placed in the ventilation duct, the outer one is closed with a decorative grille. But it is worth noting that in bathrooms it is best to use fans with a hydraulic sensor.
Car fans
The article shows the installation diagrams of fans for various purposes - supply, automotive. And the difference is only in the connection method. On machines, cooling fans start automatically. In total, cars have two fans:
- On an engine cooling radiator.
- In the heating system.
The first fan runs automatically, turns on exclusively when the temperature rises in the engine cooling system. In order to monitor the temperature, a special sensor is installed in the radiator.
On more modern cars, the fan is controlled by an electronic unit that controls the operation of the entire engine. When installing fans on the Niva, one important rule must be observed - correctly connect it to the on-board network, otherwise windings may fail.
As for the fan in the heater, it is driven by a switch on the dashboard. On vehicles with air conditioning or climate control, the fan blows two radiators. One is connected to the cooling system and allows you to warm the air. The second - to the air conditioner and cools the air in the cabin. When installing a cooling fan, the main thing is not to confuse the sides so that the air moves in the right direction. Fasteners are made using a bolted connection.