General information about fans. Types of smoke exhausters, their design, characteristics A few words about axial fans

Smoke exhauster for boiler - equipment necessary for efficient work heating system, which is otherwise called “traction fans”. IN engineering networks industrial type, large-sized units of similar action are installed on thermal power plants: blowing and traction, ensuring the stability of the fuel combustion process.

Purpose of the smoke exhauster

The smoke exhauster for a solid fuel boiler is an apparatus for domestic and industrial use. It ensures constant thrust and allows you to control the fuel combustion process. Installation of a smoke exhauster for a furnace is necessary for several reasons:

• thanks to high-quality draft, smoke from the firebox does not penetrate into the boiler room through cracks, as well as when the door is opened;
• the possibility of installing a heating system in conditions of no draft;
• implementation of control over the amount of fuel burned and the intensity of combustion by regulating draft.

There is such a variety of equipment as smoke exhausters, dust collectors and firefighters. The former perform the function of cleaning exiting flue gases. The latter ensure air purification from combustion products during fires and have the function of supplying fresh air(not all models).

There are devices for removing aerosols, small powdery suspensions, and gases. The most powerful units can provide air purification within a few seconds. Such machines are equipped with a filter system that absorbs combustion products and other substances that enter them. Fire smoke exhausters can be small-sized or large-sized (trailed).

Types of smoke exhausters

There are several types of smoke exhausters, each of which has its own marking.

The marking of smoke exhausters consists not only of letter designations, there are also digital ones. The second ones indicate the diameter of the device or fan wheel. There are three possible design options for smoke exhausters:

A smoke exhauster for a fireplace is a small-sized device with a one-way draft, which is placed in the chimney pipe. Where the device is installed, all gaps are filled with heat-resistant sealant. To ensure effective removal of smoke into the atmosphere and a stable flow of air into the fireplace or stove, equipment such as a centrifugal smoke exhauster is recommended.
Popular models of smoke exhausters for boilers:

Device

The smoke exhauster is a structurally simple device. It consists of several nodes, each of which has its own purpose.

The body is made in the form of a “snail”, which provides the required swirl of air entering the unit. Made of heat-resistant steel, covered with thermal insulation.

The guide apparatus of the smoke exhauster is located on the suction pipe, allowing you to regulate the air pressure using rotary mechanism, combining the fan blades. Each blade is curved, which allows the air flow to rotate in the same direction in which the rotor rotates. Using a rotating mechanism, you can block the lumen of the pipe to one degree or another.

Working wheel smoke exhauster - a unit on which the fan blades are located. They are attached to it by welding or rivets. A rarefied atmosphere is created in the central part of the wheel as it rotates. For this reason, incoming air is drawn in here. Small-sized devices such as smoke exhausters for fireplaces work in a similar way.

The wheel docking unit can be located on the motor shaft or intermediate shaft, depending on the design of the unit. If this is dust collection equipment, the device includes special filters with absorbents. All fire-fighting units are equipped in this way. Ash collectors can be included in the design of boiler room equipment. The design of the smoke exhauster determines its purpose.

The impeller may have holes necessary to fix the blades in a given position. Balancing can be done manually or by an electrical actuator. You can distinguish the direction of rotation of the fan blades if you look at the unit from the side of its electric motor. The axial guide apparatus of the smoke exhauster ensures rotation of the blades, regardless of their number and direction of slope, at an angle from 0 to 90°.

A blower fan and a smoke exhauster have a similar design, but differ in purpose. Devices of the first type provide air injection into the boiler furnace. The latter are designed to remove fuel combustion products and release them into the atmosphere outside the boiler room.

Fans and smoke exhausters of boiler installations have the same operating principle; they can be left- or right-handed, with forward and reverse draft. These machines are designed for long-term trouble-free operation in a temperature range from 0 °C to +250 °C. Smoke exhausters are marked as “D” and “DN”, fans - as “VDN”. The latter are produced with the impeller mounted on the electric motor shaft.

Repair of smoke exhausters and fans is carried out by persons who have passed the appropriate certification and instructions on the safety of operating electrical appliances.

Advantages of furnaces with forced-air fans

The design of a modern blower fan for wood-burning and other types of boilers may include ash collectors. This equipment comes in several types:

The latter are the most effective. The operation of cyclones is based on the action of centrifugal forces. The products of fuel combustion are removed by draft action in such a way that they swirl and large particles fall into a special bunker. The design of cyclones may be different, but the principle of operation remains the same.

Smoke exhausters for domestic solid fuel boilers provide stable supply air into the firebox. Therefore, heating equipment can operate uninterruptedly even under unfavorable conditions for fuel combustion. It could be high humidity lumber or lack of sufficient oxygen to support combustion processes.

To ensure control over the operation of the boiler, a draft regulator is installed. This device may not be included with the unit and will need to be purchased separately. There are three types of boiler thermostat:

The design of any of them includes control and adjustment units, temperature-sensitive elements. The regulator operates by reading the physical characteristics of the sensor (temperature-sensitive element). They ( physical properties) change when heated, which is detected by the control unit and transmits a signal to the unit that is included in the structure, depending on its type:

• electromagnetic relay;
• electronic device;
• mechanical valve.

Smoke exhausters for boilers, equipped with thermostats, are more convenient to use devices. They allow you to automate the process of monitoring fuel combustion in the furnace. A machine without a temperature sensor can always be equipped with one by purchasing and installing additional equipment.

Fan is a device driven by an engine to create a flow of air or other gases. Fans are used in air conditioning, ventilation, heating, pneumatic transport systems; they help organize movement air flow in boilers, radiators of internal combustion engines are cooled, draft is created in vacuum cleaners, cooling and drying systems.

Fans create a relatively low overpressure(vacuum), usually not exceeding 12 kPa. To create higher pressures, blowers and compressors are used instead of fans.

There are two most common types of fans:

a) centrifugal (radial);

b) axial.

There are also diametrical fans, diagonal fans, but by now they are widely used in industrial ventilation systems they didn’t receive it, so we won’t consider them for now.

Centrifugal (or radial) fan has an impeller located in a spiral casing, during the rotation of which the gas entering through the inlet enters the channels between the blades, under the action of the resulting centrifugal force moves into the spiral casing and is directed to the outlet. The direction of gas flow changes by 90 0 .

shoulder blades centrifugal fans can be of three types: radial (straight), curved forward and curved back; accordingly differ and specifications fans and, as a result, their purpose.

Fans with radial blades are often used to move dusty gas-air media.

Fans with backward-curved blades can operate at more high speeds rotation.

Fans with forward-curved blades provide greater (compared to other types) performance and pressure.

It is generally accepted to divide fans according to several indicators:

According to the amount of air created when moving total pressure:

Fans low pressure(up to 1 kPa);

Medium pressure fans (up to 3 kPa);

Fans high pressure(up to 12 kPa).

Depending on the composition of the transported medium and conditions:

Conventional - for air (gases) with temperatures up to 80°C;

Corrosion-resistant - for aggressive environments;

Heat-resistant - for air with a temperature of 80-200 ° C;

Explosion-proof and spark-proof - for explosive environments;

Dust - for dusty air (solid impurities in quantities of more than 100 mg/m³).

At installation location:

Conventional, installed on a special support (frame, foundation, etc.);

Duct, installed directly in the air duct;

Roof mounted, placed on the roof.

This division is very arbitrary. For example, a low-pressure fan VTs 4-75 can create a total pressure of more than 2 kPa, but a VTs 14-46 (medium pressure) does not always reach the same 2 kPa. And on the roof you can install not only roof fans, but also any others, as long as the roof is strong enough. And dust fans work great with clean air.

Here design fans are strictly regulated. According to GOST 5976-90, radial fans(except for channel ones) can be produced in 7 versions.

The most common (in descending order):

- version 1(the impeller is mounted directly on the motor shaft). The advantages are obvious: minimum parts, minimum assembly work, minimum acquisition costs, compactness. There are also disadvantages. The impellers of large fan numbers (8 and above) have a fairly large mass and all this mass affects the bearings of the electric motor. To carry out maintenance on the engine and get to its bearings, you need to completely disassemble (and then reassemble) the fan. This is not always easy to do in the workplace.

- version 5(the impeller is located cantilevered on the propulsion shaft, driven by a V-belt drive). Widely used to drive dust fans, high pressure fans, and large number fans (8 and above). Advantages: electric motor bearings accept less radial load, the ability to ensure engine operation in nominal mode by selecting pulley diameters. Disadvantages: increased dimensions and weight, increased maintenance complexity and price.

- version 3(the impeller is located cantilevered on the promopor shaft, clutch transmission). It is mainly used to drive fans operating in specific conditions (high temperatures, aggressive environments, etc.). Advantages: radial loads are not transferred to the engine, it is possible to protect the promo-pore bearings from the influence of the moved environment (temperature, humidity, aggressiveness). The disadvantages are approximately the same as in version 5, although there are fewer components (no tensioning device, belts, simpler fencing).

The same GOST 5976-90 and GOST 22270-76 establish direction of rotation And volute housing rotation angle fan

By definition, fans can be right rotation(the wheel rotates clockwise when viewed from the suction side) and left rotation(the wheel rotates counterclockwise when viewed from the suction side).

It would seem that everything is clear and clearly defined. But no! There is a type of fan for which both the direction of rotation and the angle of rotation are determined completely differently. These are draft machines (smoke exhausters and blower fans), operating primarily in boiler rooms. For them, the direction of rotation is determined from the drive side, and the rotation angle is 0 0 - the exhaust is directed towards the bottom. Why this is so and who needed it is the question.

A few words about axial fans.

Axial fan has an impeller located in a cylindrical body, consisting of a hub with blades attached to it. When the wheel rotates, air (gas) moves along the axis of rotation.

Axial fans can have various designs impeller and casing (housing), and also differ in the shape and number of blades. In some cases (for example, in ordinary room fan) the casing is missing. The cross-section of the blades can be profiled (volumetric), but in most cases the blades are flat or curved plates. Manufacture blades made of plastic, aluminum or steel.

Axial fans are simpler in design than centrifugal fans, have higher efficiency, are highly efficient, but do not provide high pressures.

By purpose Axial fans are divided into general purpose and special purpose fans.

General purpose fans are designed to move clean or low-dust air, the temperature of which should not exceed 40 0 ​​C. This temperature limitation is caused by the fact that the electric motor is usually located in the flow of transported gas, and the temperature limit environment for electric motors it is precisely 35-40 0 C. The choice of general-purpose axial fans is small - the most widely used fans are types B 06-300 and B 2.3-130, as well as their later modifications.

TO special axial fans include fans used to move explosive and aggressive gas-air media, mine fans and tunnel ventilation fans, ceiling fans, poultry fans, cooling tower fans, fans built into process equipment, etc.

HOW TO ORDER A FAN?

Ideally In this case, when ordering, you must indicate the type of fan, its number, which electric motor it will be equipped with, the direction of rotation and the angle of rotation of the housing. And if everything is more or less clear with the last two questions, then the rest need to be sorted out a little.

Firstly (as the simplest thing),fan number . The number determines the diameter of the impeller in decimeters. That is, for the VTs 4-75-3.15 fan the diameter of the impeller is 315 mm, and for the DN-11.2 smoke exhauster it is 1120 mm.

Fan type. If you need a fan to replace a faulty one or you are building a system similar to the existing one, rewrite the sign on the old fan. If it is not there, measure the impeller ( outside diameter, number of blades, diameter and length of the mounting hole in the hub). You can also specify inner dimensions suction and discharge pipes. Usually this is enough to determine the type of fan.

In the case of designing (installing) a new exhaust, supply or process ventilation system, it is necessary to know the performance and total pressure that the fan must provide. Performance- this is the volume of air removed (injected) from a ventilated room or workplace. It is usually expressed in m 3 /hour. Total pressure in general, it should compensate for the resistance to air passage in air ducts and network equipment (valves, dampers, air heaters, filters, silencers, etc.). The unit of measurement for total pressure is Pa.

In the reference literature and on almost all websites (including ours) of enterprises involved in fans, their aerodynamic characteristics.

Aerodynamic characteristics are a set of straight and curved lines. The axes are simple: horizontal axis - fan capacity in m 3 /hour, vertical - total pressure in Pa. We find the required operating point (performance-pressure) on the thick curve (which is the characteristic of the fan), then we determine the power of the electric motor, its speed and (rather for ourselves) the efficiency of the fan. The electric motor parameters (power and rotation speed) are indicated on the nearest thin curves located above the fan characteristic. Fan efficiency - inclined straight lines.

All aerodynamic characteristics of fans are given for standard conditions.

The following are considered standard conditions (GOST 10616-90):

Air temperature - 293 K (20 0 C);

Atmospheric pressure - 101.34 kPa;

Air density - 1.2 kg/m 3 ;

Relative air humidity - 50%.

Therefore, if operating conditions for fans differ from standard ones (almost always), this must be taken into account.

It should be said that calculate the networks and take into account all pressure losses with high accuracy It’s almost impossible, so it’s better to choose fans with a pressure margin of 10-20%.

Fans are an integral part of ventilation, air conditioning and heating systems. They are used both in industrial premises, and in residential buildings to ensure better air circulation or exhaust.

Example of a fan used in industrial premises

This device is a device consisting of a propeller and an electric motor that sets them in motion. Based on the type of installation, they are divided into indoor and roof-mounted. How to determine which direction the blades rotate? How to change the direction of rotation? How to determine the frequency of revolutions produced? This is exactly what we will talk about next.

Determining the direction of rotation

Determining the direction of movement of the impeller is very simple. Often the direction of rotation is marked with an arrow. The arrow indicates the direction in which the impeller rotates. If for some reason there is no indication of the direction of movement, then determining the correct side will not be difficult without it.

An example of a snail directional indicator

To determine the direction of the blades, it is necessary to look at the structure from the side of the hole through which air is sucked. If the impeller rotates clockwise and the snail-type housing is twisted clockwise, the movement is to the right. If the blades rotate counterclockwise, the side is left.

How to determine the fan speed?

The RPM shows its installation performance. In order to calculate the frequency of movement of the impeller, a device called a tachometer is used. For a more accurate determination, it is recommended to use tachometers with accuracy class 0.5 or 1.

Tachometers differ in location of installation and are divided into:

• stationary;
• remote;
• manual.

Tachometers also differ in their operating principle. They are mechanical, magnetic, magnetic induction and electronic.

Modern electronic tachometer in action

Let's look at the example shown in the picture. Using a laser beam directed at the wheel, the rotation speed (rpm) is measured. All data is displayed on a small display.

How to change the direction of rotation of the propeller?

Sometimes situations arise when you need to change the direction of rotation of the blades. For such purposes, reversible fans are used. Their main difference is that the reversible fan is designed for possible changes directions, but the usual one does not.

Reversible model

Reversible models have become widespread at mining enterprises. They serve both to supply air and to exhaust it.

Reversible axle models used in mines

Changing the direction of movement of axial models is carried out in two main ways:

• Without changing the direction of rotation.
• With a change in direction of rotation.

When using the second method without changing the position of the blades, the system does not work at full capacity. The wheel works backwards forward, which reduces efficiency. In order to get 100% performance during reverse, it is necessary to change the position of the blades.

In order to change the direction of rotation of the propeller, it is necessary to disassemble the engine and change the phases:

• On a single-phase motor, we have 4 wires at the output. 2 wires at the beginning of the winding and 2 at the end. To reverse, you need to transfer the phase and zero from the beginning of the winding to the end.
• In case of three-phase motor at the output we have 6 wires. 3 at the beginning of the winding and 3 at its end. For reverse in three-phase network we need to swap any two wires at the input.
• To reverse a three-phase electric motor connected to a single-phase network through a starting capacitor, it is necessary to swap the cable going to the input of the capacitor with the cable that is not connected to it.

In order to change the direction of travel of the exhaust hood propeller ( kitchen hood) there are two working methods:

1. If the hood design is equipped with asynchronous electric motor, the change is made by reversing the wires (the method is described above).
2. If there is a phase-shifting capacitor, the change is made by rearranging it. For correct execution this method It is recommended that you seek the services of an experienced electrician.

Exhaust hood

Summarize. The direction of wheel travel is determined either by an arrow drawn on the body or impeller, or by looking at it from the side.

A device called a tachometer is used to measure the speed of the blades. They come in both old mechanical ones and modern ones that read information using a laser beam.

To change the direction of rotation of the blades, we simply need to change the necessary contacts on the electric motor. If, after changing the direction side, it is not possible to change the position of the blades, then the efficiency and its performance will drop by about 30% of the norm (depending on the type).

All these procedures can be performed without special effort and with your own hands.

Abbreviation designation

D 3.5 dv.3*1500 Lv.90 sh.1 deciphered as follows:

- D– a smoke exhauster (a device whose design is an industrial fan, the manufacture of which uses thicker metal; its purpose is to operate at high temperatures);
- 3,5 – 3.5 DM or 350 millimeters – the size of the impeller, which traditionally affects the size of the entire unit;
- dv. – electric motor;
- 3 – 3 kilowatts, this is exactly the power of the electric motor;
- 1500 – 1500 revolutions (meaning the revolutions of the electric motor shaft);
- Lv.– left (meaning the reversal of the cochlea);
- 90 – 90 degrees, rotation of the snail;
- сх.1– scheme number 1 (design scheme in which the impeller is located on the same shaft as the engine).

Direction of rotation and angle of rotation of the body (volute) of smoke exhausters, diagram No. 1, view from the electric motor side

Scheme of reversal of housings of type D draft machines of RIGHT rotation.

Scheme of reversal of housings of type D draft machines of LEFT rotation.

The main elements of smoke exhausters, as well as centrifugal fans, are:

1. The volute is a stationary spiral-shaped casing made of metal, in which vortex flows are created.

2. Impeller. The second name of this element is “squirrel wheel”. The rotating part of this element consists of two disks: a central one (in the middle there is a bushing designed for a rotating shaft), an open one (air intake blades that are curved at a certain angle are attached to it).

3. Electric motor. It is the main drive for the installation. Smoke exhausters, depending on the recommended operating conditions, are equipped with different types motors: asynchronous; two-speed asynchronous, allowing to work together with a guide vane, characterized by economical regulation; single-speed asynchronous type DAZO. In addition, engines may have different degrees of explosion hazard and different climatic conditions.

4. Frame – metal, load-bearing frame, which may be modified or absent - it all depends on the specific execution scheme. There are 6 schemes in total: schemes No. 5, 3 and 1 can be executed on a single pedestal with a vibration base or on a single pedestal without vibration generation. However, these ventilation units can also be installed in a non-standard way - depending on the location and project.

Again, depending on the design, the machines can be equipped with a “bearing shaft” (Fig. 3), “V-belt drive” (Fig. 5). If the customer wishes and the size is suitable, it can be equipped with a guide vane NA.

2. Purpose of smoke exhausters

An important installation in almost all areas of the boiler industry are smoke exhausters. The latter occupy the main, main place in the operation of the central heating system.

Equipment of this type is installed on large and small stationary water heating and steam boilers. They are suitable for almost all types of boiler rooms. Can also be used to move in other technological installations dust-smoke-air mixtures.

DN-type draft machines are designed to move smoke, dust, gas and air mixtures that are not explosive with a dust content of no more than 2 grams per m3. To put it in simpler, understandable words, such a device is powerful fan, designed to remove combustion products (smoke, steam, fumes) from combustion chambers with temperature range from minus 30 to plus 200 degrees or up to plus 400 degrees (if we're talking about about a new, optimized, improved design). For more information about the latter, please call +7 4995023405.

3. Features of smoke exhauster D

DN-type draft machines are manufactured in two types - right and left rotation, as indicated by the corresponding abbreviations in their abbreviations (R. and L.). In order to determine the direction of rotation, you need to look at the wheel from the engine side: left rotation will occur counterclockwise, the right - clockwise. The rotation angle of the cochlea ranges from 0 to 270 degrees, with the rotation interval every 15 degrees. Interfering volute stiffening ribs are modified, if necessary. mechanically- are pruned.

Maintenance and inspection of the impellers should be carried out through small special hatches provided in the volute wall. In addition, all volute housings have special buttons designed to drain condensate.

Movez smoke exhausters (created according to scheme 5 or 3) are equipped with bearings big size(from the impeller side), which increases the degree of reliability and durability of the entire product. For such fans, the bearing units are made dismountable - this is important for maintainability. In addition, starting from the 9th standard size (that is, DN 9, etc. up to DN 22), it is possible to equip it with a cooling coil (optional; necessary to prevent possible overheating).

A guide vane is used to regulate operating modes. The latter, by changing the aerodynamic characteristics, increases efficiency and reduces energy losses of the installation.

In order to prevent the entry of large particles that can damage the working parts of the device, suction pockets are used - they retain all solid fractions.