Gas heating of industrial and residential premises is controlled by automatic control. Today's technologies make it possible to conduct accurate regulation the desired temperature, while saving on fuel. This result was achieved due to the use of burners with the power adjustment option, which is ensured by the automation of the gas burner.
A gas burner with automatic control for a boiler is an apparatus that mixes gas with air and burns this resulting composition in a combustion chamber.
How does the automatic temperature control system work?
The simplest system for automatic regulation of the set temperature using a gas burner works as follows: gas is supplied to the burner, which is ignited by the ignition function, and thus constant combustion occurs. In this case, the burner itself operates at its full strength. When a certain temperature of the coolant or air in the room is reached, the automatic equipment of the gas burner extinguishes the fire.
To maintain the set temperature, the burner is constantly switched on and off.
Classification of gas burners by temperature control
With the modern development of technology, new, improved methods of automatic temperature control have been developed:
- Single-stage burners are the simplest devices, the principle of which was described above. These burners operate in the same mode.
- Two-stage burners are devices that can operate in two states (40% and 100% of the total power), switching between themselves automatically.
- Sliding two-stage burners - these also operate in two states (40% and 100%), but the switching itself between modes is smoother, which significantly saves the fuel itself and improves the quality of temperature maintenance.
- Modulated gas burners with automatic controls for the boiler are the most functional devices capable of operating in a wide power range (from 10 to 100%). They can maintain a temperature regime with a deviation of only 20C from the initial value. At the same time, the efficiency of fuel combustion increases, and the temperature loads on the parts of the heater decrease.
The most effective of all is the copper heat exchanger, as it has thin walls and good thermal conductivity. BUT it does not tolerate high temperature voltages, therefore, it has a short period of operation. In combination with the modulating gas burner automation, the service life of the gas burner increases.
Gas burners with the option to change the combustion level are expensive, but their efficiency quickly pays for all the costs:
- the temperature is kept in a small range;
- fuel savings up to 30%;
- the service life of the entire device increases.
So we recommend buying a gas burner with automatic equipment!
The main elements of the auto-control system
Devices included in the burner electrical circuit to start the automatic operation of the device:
- Relay max. and minimal. gas pressure - has a light structure, which affects its long service life. The principle of operation is that the gas pressure affects the membrane, and when it deviates from the set mode, the system is triggered, and the control valve performs the required work. Relay min. gas pressure protects against a decrease in gas pressure to a critical point, and the maximum pressure switch adjusts, preventing an increase in the permissible value.
- Relay for min and max pressure of the heating agent - protects the heating system from excessive decrease and increase in pressure of the heating device. Both options are dangerous and undesirable for the continued operation of the boiler, therefore, when a critical point (lower or upper) is reached, the boiler shuts down, that is, the gas supply stops.
- The combustion controller is a part that integrates the operation of the entire burner into an overall process. The operation of gas burners of heating boilers with automation is divided into several sections, which correspond to the required position of the fuel control valve and air damper. Having received a signal about a low temperature, the controller opens the appropriate mechanisms to increase the combustion force. The controller's operation is based on signals from different sensors (temperature, pressure).
- The thermostat is a signaling device for reaching the limit temperature levels. On its signal, a change in combustion modes is carried out.
- Boiler filling sensor - is required to protect the burner from starting, without the presence of heat carrier in the boiler.
The connection of the sensors largely depends on the manufacturer of the boiler. This data can be seen in the passport of the device, and the features of connecting the sensors are carefully described in additional instructions. In this case, the connection and setting of the automatic system must be controlled by a gas service employee. In his presence, commissioning is also carried out, with the indispensable drawing up of an act on the serviceability of the equipment for safe operation.
Types of auto control systems for gas boilers
There are control systems of different brands and purposes, but they all work according to the same principles. They differ only in the functionality of the system and the dependence on the electrical network.
All varieties can be combined into three main groups of gas burner automation:
- Non-volatile types.
- Volatile wire systems.
- Volatile wireless.
The non-volatile boiler control structure is the most basic automation for a heater. Its principle of operation is based on the physical law of expansion when the material is heated. A similar effect of such a law can be observed on the example of a thermometer - mercury, when heated, expands and rises up a tube fixed on the scale. The reverse process can be seen during cooling.
Now imagine that the same structure stands inside the boiler and measures the temperature of the heated device, only instead of mercury, another material (metal) is used. It expands when heated and affects the mechanical gas shut-off lever. As soon as the burner cools down, the metal is compressed, acting on the lever, and the gas flow is resumed again.
The volatile boiler control system operates from the mains - which creates inconvenience, but at the same time the productivity of the equipment increases. The main part of such systems is the thermostat. Depending on the temperature regime, it sends an electromagnetic pulse to the gas valve. But with the help of a special program, it is possible to program the temperature mode for several days in advance, weeks or even months.
The non-volatile wireless boiler control system functions on the same principle as the wired one. The only difference is that the control module of the wireless version is located in any place convenient for you, while it is not connected with a wire to the device.
Some devices provide for the installation of a GSM module that provides access through mobile gadgets (smartphones, tablets). To find out the latest data on the state of the device, you just need to go to the application on your smartphone and enter the required password.
Through mobile devices, it is possible not only to control gas burners with automatic heating boilers, but also to control them. And in the event of a special situation, the system will automatically send you a notification in the form of an SMS to your number.
Today, modern technologies can provide full automatic control over an autonomous heating system, without creating additional efforts.
Heating gas boilers have a complex structure. Their design includes combustion chambers, gas burners for boilers, they are equipped with automation. The double-circuit equipment also includes boilers that heat water for household needs. Regardless of the brand and model of a gas boiler, the most important part is the burner. The efficiency of the entire heating system of the house, as well as the saving of fuel resources, largely depends on it.
Classification of gas burners
In a device called a gas burner, there is a process of mixing the supplied gas and the intake or forced air, followed by the combustion of the combustible composition in the combustion chamber. It can operate in the conditions of main supply gas, as well as from a cylinder or a special tank. The process itself depends on the characteristics of the burner and the possibility of adjusting it to certain conditions.
Depending on the method of air intake, gas burners are divided into two types:
- atmospheric - an air-gas mixture is obtained by naturally sucking air from the surrounding space and mixing it with the supplied gas;
- supercharged, using a fan in operation, forcibly blowing air;
- combined.
In the first case, it is said about boilers with open combustion chambers, and in the second - with closed ones. Also, gas burners for heating boilers have a different type of power control:
- one-stage - the simplest and most affordable;
- two-stage - with two automatically switching modes of operation;
- smooth two-stage - with soft flame control between two stages;
- modulated - the most effective and reliable, with accurate and fast regulation depending on the change in the temperature regime of the coolant. Differs in high cost.
What to look for when choosing
When buying, one should take into account the operating conditions of the heating equipment, the peculiarities of its operation and the possibility of maintenance. The dimensions of the gas burner must be in accordance with the dimensions of the boiler furnace, otherwise, instead of reliability and durability, it will be possible to get a burnt combustion chamber.
Each of the burners has its own characteristics, thanks to which one or another model is chosen for each specific case.
A certain value when choosing a gas burner is:
- manufacturer;
- specifications;
- model;
- price;
- hardware compatibility.
Atmospheric burners
This design is a perforated tube with a profile section, into which gas is supplied. A reduced pressure is created in the tube, due to which air is sucked into it directly from the room where the boiler is located. As a result, a combustible substance is formed that supports the combustion process after lighting the wick with the help of a piezo or electric element. Such burners have another name - injection.
Atmospheric burners are quite often called gas burners, designed for heating boilers equipped with open combustion chambers.
The considered option of gas burners is perfect for small houses, up to 100 sq. meters. Atmospheric gas burners for a boiler are usually cheaper than pressurized counterparts. But the cost of modern automatic models is high.
Advantages
Atmospheric burners are widely used by owners of private houses. Their positive characteristics include:
- noiselessness;
- compactness;
- independence of most models from power supply;
- reliability due to constructive simplicity;
- low operating costs;
- affordable price.
disadvantages
We can say the following about weaknesses:
- low power;
- low efficiency (no more than 90%);
- sensitivity to frequent changes in the pressure of the supplied gas (the need to install additional automation, in particular, a control relay that responds to pressure changes);
- maintaining a high level of cleanliness of the room where the boiler is located, in order to avoid clogging of the burner with dust.
Pressure surges can lead to burnout of the gas burner nozzle with a reduced gas supply, or to burn out the heat exchanger with an excessive flame height.
Pressurized burners
For operation with boilers equipped with a closed combustion chamber, pressurized, or blown, burners are intended. Air is forced here by fans. In this case, there is an additional possibility of flexible regulation of the flow rate of the gas-air mixture, in connection with which, there is a real achievement of high efficiency indicators.
Pressurized burners have a more complex design. It is noteworthy that air is supplied to this device in parts, but it mixes with gas almost instantly. Gas boilers, in turn, also have their own differences from those that work in tandem with atmospheric burners.
Schematically, the boiler is represented by barrels of different diameters and depths inserted into each other in such a way that their bottom is at the top. A coolant circulates between the walls, which is heated by the burner torch from several sides at once - from above and on the sides. This design ensures high performance of the equipment.
A significant difference between blowing burners and atmospheric burners is that the former are not considered an integral part of the boilers, but additional equipment that is purchased separately.
Modern pressurized burners are necessarily equipped with automatic controls that ensure uninterrupted and reliable operation of heating equipment. Outwardly, they look like a block, inside which is the burner itself with a built-in electric fan.
The considered devices are divided into:
- vortex, equipped with round outlets. Provide powerful air flow and stable combustion;
- direct-flow, feeding the combustible mixture through the outlet openings having different shapes (circle, slot, rectangle).
Advantages
It should be fairly noted that pressurized gas burners:
- safe - the combustion process takes place in an isolated space;
- highly productive and highly efficient, due to their design features, the efficiency is about 95%;
- insensitive to pressure drops - a decrease in the indicator is compensated by the presence of a fan;
- environmentally friendly;
- have the ability to replace with other types of burners.
disadvantages
It is not easy to find equipment that is devoid of flaws. They are also present in blowing burners:
- the presence of noise during operation dictates the need to install the boiler in a separate room;
- dependence on electricity requires the presence of a UPS in the system;
- volumetric dimensions make it impossible to install heating equipment in small rooms;
- the high cost of the device prevents its use by all categories of consumers.
Combined burners
They are produced for combined heating boilers capable of operating both on gas and on liquid fuel (fuel oil, diesel fuel). Such devices do not require replacement in the event of a transition from one combustible mixture to another. But the switching process itself is quite complicated and requires the presence of a professional.
The burners in question are fully automated, which minimizes the human factor. They have functions for controlling the flame power, combustion mode and other equally useful processes.
Combi burners have not gained popularity among homeowners due to their complex design and high price, combined with low efficiency.
Proper care is the key to long-term operation
In the process of operation, the gas burner needs to be cleaned from soot in a timely manner. It appears during operation and, if it accumulates in large quantities, can lead to sudden ignition. A planned inspection of the equipment and regular maintenance of the heater and gas burner will help to avoid troubles.
For self-cleaning, we recommend that you read the instructions supplied with the package. But a more prudent solution would be to contact specialists who have experience in this area. In this case, the work will be much faster and better quality, with the least amount of dirt.
Gas-burner is a device for mixing oxygen with gaseous fuel in order to supply the mixture to the outlet and burn it to form a stable flame. In a gas burner, gaseous fuel supplied under pressure is mixed in a mixing device with air (air oxygen) and the resulting mixture is ignited at the outlet of the mixing device to form a stable constant flame.
Gas burners offer a wide range of benefits. The construction of a gas burner is very simple. Its start-up takes a split second and such a burner works almost flawlessly. Gas burners are used for heating boilers or industrial applications.
Today there are two main types of gas burners, their separation is carried out depending on the method used for the formation of a combustible mixture (consisting of fuel and air). Distinguish between atmospheric (injection) and supercharged (ventilation) devices. In most cases, the first type is part of the boiler and is included in its cost, while the second type is most often purchased separately. Forced gas burners as a combustion tool are more efficient, since they are supplied with air by a special fan (built into the burner).
Gas burners are intended for:
- supply of gas and air to the combustion front;
- mixture formation;
- stabilization of the ignition front;
- ensuring the required intensity of combustion.
Types of gas burners:
Diffusion burner - burner in which fuel and air
are mixed by burning.
Injection burner - pre-mixed gas burner with air, in which one of the media necessary for combustion is sucked into the combustion chamber of another medium (synonym - ejection burner)
Hollow premix burner - a burner in which the gas is mixed with a full volume of air in front of the outlets.
Non-hollow premix burner– a burner in which the gas is not completely mixed with the air in front of the outlets. Atmospheric gas burner– Injection gas burner with partial premixing of gas with air, using secondary air from the environment surrounding the flame.
Special burner– a burner, the principle of operation and design of which determines the type of heating unit or features of the technological process.
Recuperative burner– burner equipped with a recuperator for heating gas or air
Regenerative burner- a burner equipped with a re-generator for heating gas or air.
Automatic burner– a burner equipped with automatic devices: remote ignition, flame control, fuel and air pressure control, shut-off valves and controls, regulation and signaling.
urine burner– gas burner, in which the energy of the escaping gas jets is used to drive the built-in fan, which blows air into the burner.
Ignition burner– auxiliary burner used to ignite the main burner.
The most applicable today are the classification of burners by the method of air supply, which are divided into:
- blow-free - air enters the furnace due to rarefaction in it;
- injection - air is sucked in due to the energy of the gas stream;
- blast - air is supplied to the burner or furnace by means of a fan.
Gas burners are used at various gas pressures: low - up to 5000 Pa, average - from 5000 Pa to 0.3 MPa, and high - more than 0.3 MPa. Most often they use burners operating at medium and low gas pressure.
The thermal power of a gas burner is of great importance, which can be maximum, minimum and nominal.
During long-term operation of the burner, where a greater amount of gas is consumed without breaking off the flame, the maximum thermal power is achieved.
The minimum heat output occurs with stable operation of the burner and the lowest gas consumption without flame breakthrough.
When the burner is operating at a nominal, providing maximum efficiency with the greatest completeness of combustion, the gas flow rate is achieved by the nominal thermal power.
It is allowed to exceed the maximum thermal power over the nominal by no more than 20%. If the rated thermal power of the burner according to the passport is 10,000 kJ / h, the maximum should be 12,000 kJ / h.
Another important feature of gas burners is the range of heat output regulation.
Today, a large number of burners of various designs are used. A burner is selected according to certain requirements, which include: stability with changes in thermal power, reliability in operation, compactness, ease of maintenance, ensuring the completeness of gas combustion.
The main parameters and characteristics of the used gas burner devices are determined by the requirements:
- thermal power, calculated as the product of the hourly gas consumption, m 3 / h, by its lowest calorific value, J / m 3, and is the main characteristic of the burner;
- parameters of the combustion gas (net calorific value, density, Wobbe number);
- rated thermal power, equal to the maximum power attainable during long-term operation of the burner with a minimum "excess air factor a and provided that the chemical underburning does not exceed the values set for this type of burner;
- nominal gas and air pressure corresponding to the nominal thermal power of the burner at atmospheric pressure in the combustion chamber;
- nominal relative torch length equal to the distance along the torch axis from the outlet section (nozzle) of the burner at nominal thermal power to the point where the carbon dioxide content at α = 1 is equal to 95% of its maximum value;
- coefficient of limiting regulation of thermal power, equal to the ratio of the maximum thermal power to the minimum;
- coefficient of operating regulation of the burner in terms of thermal power, equal to the ratio of the rated thermal power to the minimum;
- pressure (vacuum) in the combustion chamber at the rated power of the burner;
- heat engineering (luminosity, degree of blackness) and aerodynamic characteristics of the torch;
- specific metal and material consumption and specific energy consumption, referred to the rated thermal power;
- the sound pressure level generated by the operating burner at the rated heat output.
Burner requirements
Based on the operating experience and analysis of the design of burners, it is possible to formulate the basic requirements for their design.
The design of the burner should be as simple as possible: without moving parts, without devices that change the cross-section for the passage of gas and air, and without complex-shaped parts located near the burner nose. Complex devices do not justify themselves during operation and quickly fail under the influence of high temperatures in the working space of the furnace.
The sections for the outlet of gas, air and gas-air mixture should be worked out during the creation of the burner. During operation, all these sections must be unchanged.
The amount of gas and air supplied to the burner should be measured with throttle devices on the supply lines.
The cross-sections for the passage of gas and air in the burner and the configuration of the internal cavities should be selected in such a way that the resistance on the path of gas and air movement inside the burner would be minimal.
The gas and air pressure should mainly provide the required speeds in the outlet sections of the burner. It is desirable that the air supply to the burner be regulated. Unorganized air supply as a result of vacuum in the working space or by partial injection of air with gas may only be allowed in special cases.
Burner designs.
The main elements of a gas burner: a mixer and a burner nozzle with a stabilizing device. Depending on the purpose and operating conditions of the gas burner, its elements have a different design.
V diffusion burners gas, gas and air are supplied to the combustion chamber. The mixing of gas and air takes place in the combustion chamber. Most diffusion gas burners are mounted on the walls of a furnace or furnace. In boilers, the so-called. gas hearth burners, which are located inside the furnace, in its lower part. A gas hearth burner consists of one or more gas distribution pipes in which holes are drilled. The pipe with holes is installed on the grate or hearth of the furnace in a slotted channel lined with refractory bricks. The required amount of air enters through the refractory slotted channel. With such a device, the combustion of gas streams emerging from the holes in the pipe begins in the refractory channel and ends in the furnace volume. Bottom burners have low resistance to the passage of gas, so they can work without forced blast.
Gas diffusion burners are characterized by a more uniform temperature along the length of the flame.
However, these gas burners require an increased excess air ratio (in comparison with injection ones), and also create lower thermal stresses in the furnace volume and worse conditions for gas afterburning in the tail part of the flame, which can lead to incomplete gas combustion.
Diffusion burners gas are used in industrial furnaces and boilers, where a uniform temperature is required along the length of the torch. In some processes, gas diffusion burners are indispensable. For example, in glass, open-hearth and other furnaces, when the combustion air is heated to temperatures exceeding the ignition temperature of combustible gas with air. Gas diffusion burners are also successfully used in some hot water boilers.
V injection burners combustion air is sucked in (injected) due to the energy of the gas stream and their mutual mixing takes place inside the burner body. Sometimes in gas injection burners the suction of the required amount of combustible gas, the pressure of which is close to atmospheric, is carried out by the energy of the air stream. In full-mixing burners (all the air necessary for combustion is mixed with the gas), operating on medium-pressure gas, a short flame is formed, and combustion ends in a minimum furnace volume. In partial-mixed gas injection burners, only a part (40 ÷ 60%) of the air required for combustion (the so-called primary air) is supplied, which is mixed with the gas. The rest of the air (the so-called secondary air) enters the flame from the atmosphere due to the injecting action of gas-air jets and rarefaction in the furnaces. Unlike medium pressure gas injection burners, low pressure burners form a homogeneous gas-air mixture with a gas content greater than the upper flammability limit; These gas burners are stable in operation and have a wide range of heat loads.
For stable combustion of the gas-air mixture in injection burners of medium and high pressure gas, stabilizers are used: additional igniting torches around the main flow (burners with an annular stabilizer), ceramic tunnels, inside which combustion of the gas-air mixture takes place, and plate stabilizers that create a vortex in the flow path.
In furnaces of significant dimensions, gas injection burners are collected in blocks of 2 or more burners.
Infrared gas injection burners (so-called flameless burners) are widely used, in which the main amount of heat obtained during combustion is transmitted by radiation, because the gas burns out on the emitting surface in a thin layer, without a visible flame. Ceramic nozzles or metal meshes serve as the emitting surface. These burners are used to heat rooms with a high rate of air exchange (gyms, retail premises, greenhouses, etc.), to dry painted surfaces (fabrics, paper, etc.), to heat frozen soil and bulk materials, in industrial furnaces. For uniform heating of large surfaces (furnaces of oil refineries and other industrial furnaces), the so-called. panel injection radiant burners. In these burners, the gas-air mixture from the mixer enters the common box, and then the mixture is distributed through the tubes to separate tunnels, in which it is burned. Panel burners have small dimensions and a wide control range, and are not sensitive to back pressure in the combustion chamber.
The use of gas turbine burners is increasing, in which air is supplied by an axial fan driven by a gas turbine. These burners were proposed at the beginning of the 20th century (Eikart's turbo burner). Under the action of the reactive force of the outflowing gas, the turbine, shaft and fan are rotated in the direction opposite to the outflow of gas. The burner capacity is regulated by the pressure of the incoming gas. Gas turbine burners can be used in boiler furnaces. High-pressure gas turbine burners with self-supply of air through recuperators and air economizers are promising: gas-fuel oil burners of high efficiency operating on heated and cold air.
Burners have the following requirements:
1. The main types of burners should be manufactured at the factories in series according to technical conditions. If the burners are made according to an individual project, then upon commissioning they must undergo tests to determine the main characteristics;
2. Burners must ensure the passage of a given amount of gas and the completeness of its combustion with a minimum air flow coefficient α, with the exception of burners for special purposes (for example, for furnaces in which a reducing environment is maintained);
3. While ensuring the specified technological mode, the burners must ensure the minimum amount of harmful emissions into the atmosphere;
4. The level of noise generated by the burner should not exceed 85 dB when measured with a sound level meter at a distance of 1 m from the burner and at a height of 1.5 m from the floor;
5. Burners must operate stably without separation and flame breakthrough within the design range of heat output regulation;
6. For burners with preliminary complete mixing of gas with air, the flow rate of the gas-air mixture must exceed the speed of flame propagation;
7. To reduce the consumption of electricity for auxiliary needs when using burners with forced air supply, the resistance of the air path should be minimal;
8. To reduce operating costs, the burner design and stabilizing devices should be sufficiently easy to maintain, convenient for revision and repair;
9. If it is necessary to preserve the reserve fuel, the burners must ensure a quick transfer of the unit from one fuel to another without disrupting the technological regime;
10. Combined gas-oil burners should provide approximately the same quality of combustion of both types of fuel - gas and liquid (fuel oil).
Diffusion burners
In diffusion burners, the air necessary for gas combustion is supplied from the surrounding space to the flame front due to diffusion.
Such burners are usually used in household appliances. They can also be used when the gas flow rate is increased, if it is necessary to distribute the flame over a large surface. In all cases, the gas is supplied to the burner without admixture of primary air and is mixed with it outside the burner. Therefore, these burners are sometimes referred to as external mixing burners.
The simplest in design diffusion burners (Fig. 7.1) represent a pipe with drilled holes. The distance between the holes is chosen taking into account the speed of propagation of the flame from one hole to another. These burners have low heat outputs and are used for burning natural and low-calorific gases under small water heaters.
Rice. 7.1. Diffusion burners
Figure 7.2. Bottom diffusion burner:
1 - air regulator; 2 - burner; 3 - viewing window; 4 - centering glass; 5 - horizontal tunnel; 6 - brick layouts; 7 - grate
Diffusion type industrial burners include bottom slot burners (fig. 7.2). Usually they are a pipe with a diameter of up to 50 mm, in which holes up to 4 mm in diameter are drilled in two rows. The channel is a slot in the bottom of the boiler, hence the name of the burners - bottom slot.
From the burner 2, the gas goes into the furnace, where air enters from under the grate 7. Gas streams are directed at an angle to the air flow and evenly distributed over its cross section. The process of mixing gas with air is carried out in a special slot made of refractory bricks. Thanks to such a device, the process of mixing gas with air is enhanced and a stable ignition of the gas-air mixture is ensured.
The grate is laid with refractory bricks and several slots are left in which pipes with drilled holes for gas outlet are placed. Air under the grate is supplied by a fan or as a result of vacuum in the firebox. The refractory walls of the slot are combustion stabilizers, prevent flame separation and, at the same time, increase the heat transfer process in the furnace.
Injection burners.
Injection burners are called burners in which the formation of a gas-air mixture occurs due to the energy of a gas stream. The main element of an injection burner is an injector that sucks air from the surrounding space into the burners.
Depending on the amount of injected air, the burners can be completely premixed with air or with incomplete air injection.
Burners with incomplete air injection. Only part of the air necessary for combustion enters the combustion front, the rest of the air comes from the surrounding space. These burners operate at low gas pressure. They are called low pressure injection burners.
The main parts of the injection burners (fig. 7.3) are the primary air regulator, nozzle, mixer and manifold.
The primary air regulator 7 is a rotating disc or washer and regulates the amount of primary air entering the burner. Nozzle 1 serves to convert the potential energy of gas pressure into kinetic energy, i.e. to give the gas jet a speed that allows the required air to be sucked in. The burner mixer consists of three parts: injector, confuser and diffuser. Injector 2 creates a vacuum and air suction. The narrowest part of the mixer is confuser 3, which levels the flow of the gas-air mixture. In the diffuser 4, the final mixing of the gas-air mixture and an increase in its pressure occur due to a decrease in speed.
From the diffuser, the gas-air mixture enters the manifold 5, which distributes the gas-air mixture through the holes 6. The shape of the manifold and the location of the holes depends on the type of burners and their purpose.
Low-pressure injection burners have a number of positive qualities, due to which they are widely used in household gas appliances, as well as in gas appliances for catering and other household gas consumers. The burners are also used in cast iron heating boilers.
Rice. 7.3. Injection atmospheric gas burners
a- low pressure; b- burner for a cast iron boiler; 1 - nozzle. 2 - injector, 3 - confuser, 4 - diffuser, 5 - collector. 6 - holes, 7 - primary air regulator
The main advantages of low pressure injection burners: simplicity of design, stable operation of burners with changing loads; reliability and ease of maintenance; noiselessness of work; the possibility of complete gas combustion and operation at low gas pressures; lack of air supply under pressure.
An important characteristic of incompletely mixed injection burners is injection ratio- the ratio of the volume of injected air to the volume of air required for complete combustion of the gas. So, if for complete combustion of 1 m 3 of gas 10 m 3 of air is needed, and the primary air is 4 m 3, then the injection ratio is 4: 10 = 0.4.
The characteristic of the burners is also injection rate- the ratio of the primary air to the gas flow rate of the burner. In this case, when 4 m 3 of air is injected into 1 m 3 of the combusted gas, the injection ratio is 4.
The advantage of injection burners: the property of their self-regulation, i.e. maintaining a constant proportion between the amount of gas supplied to the burner and the amount of injected air at a constant gas pressure.
Mixing burners. Forced air burners.
Forced air burners are widely used in various heating devices in municipal and industrial enterprises.
According to the principle of operation, these burners are divided into burners with preliminary mixing of gas (Fig. 7.4) and fuel and burners without preliminary preparation of the gas-air mixture. Burners of both types can operate on natural, coke oven, blast furnace, mixed and other low and medium pressure combustible gases. Working regulation range - 0.1 ÷ 5000 m 3 / h.
The air to the burners is supplied by low and medium pressure centrifugal or axial fans. Fans can be installed on each burner or one fan for a specific group of burners. In this case, as a rule, all the primary air is supplied by fans, while the secondary air practically does not affect the quality of combustion and is determined only by the suction of air into the combustion chamber through leaks in the combustion fittings and hatches.
The advantages of burners with forced air supply are: the possibility of using in combustion chambers with different back pressure, a significant range of regulation of the heat output and the gas-air ratio, relatively small torch sizes, insignificant noise during operation, simple design, the possibility of preheating gas or air and the use of burners large unit capacity.
Low pressure burners are used at a gas flow rate of 50 ÷ 100 m 3 / h, at a flow rate of 100 ÷ 5000 it is advisable to use medium pressure burners.
The air pressure, depending on the design of the burner and the required thermal power, is taken to be 0.5 ÷ 5 kPa.
For better mixing of the fuel-air mixture, gas is supplied to most burners in small jets at different angles to the flow of the primary blast air. In order to intensify the mixture formation, the air flow is given a turbulent motion using specially installed vortex blades, tangential guides, etc.
The most common burners with forced internal mixing air include burners with a gas flow rate of up to 5000 m3 / h and more. They can provide a predetermined quality of preparation of the fuel-air mixture before it is fed into the combustion chamber.
Depending on the design of the burner, the processes of mixing fuel and air can be different: the first is the preparation of the fuel-air mixture directly in the mixing chamber of the burner, when the finished gas-air mixture enters the furnace, the second is when the mixing process begins in the burner and ends in the combustion chamber. In all cases, the speed of the outflow of the gas-air mixture is different 16 ... 60 m / s. Intensification of gas and air mixture formation is achieved by jet gas supply, the use of adjustable blades, tangential air supply, etc. When gas jet supply, burners are used with a central gas supply (from the center of the burner to the periphery) and with a peripheral one.
The maximum air pressure at the burner inlet is 5 kPa. It can work with back pressure and vacuum in the combustion chamber. In these burners, unlike external mixing burners, the flame is less luminous and relatively small in size. Ceramic tunnels are most often used as stabilizers. However, all methods discussed above can be used.
The burner of the GNP type with forced air supply and central gas supply, designed by specialists of the Teploproekt Institute, is intended for use in furnaces with significant thermal stresses. These burners are designed to swirl the air flow using blades. The burner kit includes two nozzles: a type A nozzle used for short-flare gas combustion with 4 ÷ 6 gas outlet holes directed perpendicularly or at an angle of 45 ° to the air flow, and a type B nozzle used to obtain an elongated flame and having one central hole directed parallel to the air flow. In the latter case, the premixing of gas and air is much worse, which leads to an elongation of the flame.
Flare stabilization is ensured by the use of a class A fireclay brick fireproof tunnel. Burners can operate in cold and heated air. The excess air ratio is 1.05. Burners of this type are used in steam boilers, bakery industry.
The GMG two-line gas-oil burner is designed for burning natural gas or low-sulfur liquid fuels such as diesel, household fuel, naval fuel oils F5, F12, etc. Co-firing of gas and liquid fuel is allowed.
The burner gas nozzle has two rows of holes directed at 90 ° to each other. The holes on the side surface of the nozzle allow gas to be supplied to the swirling secondary blast air stream, the holes on the end surface to the swirling primary air stream.
The process of formation of a gas-air mixture in burners with forced air supply begins directly in the burner itself, and ends already in the firebox. During combustion, the gas burns out with a short and non-luminous flame. The air required for gas combustion is forced into the burner by means of a fan. Gas and air are supplied through separate pipes.
This type of burner is also called two-wire or mixing burners. The most commonly used burners operate at low gas and air pressure. Also, some burner designs are used at medium pressure.
Burners are installed in boiler furnaces, heating and drying ovens, etc.
The principle of operation of a forced air burner:
The gas enters the nozzle 1 with a pressure of up to 1200 Pa and leaves it through eight holes with a diameter of 4.5 mm. These holes must be at a 30 ° angle to the burner axis. Special blades, which set the rotational movement of the air flow, are located in the body 2 of the burner. During operation, the gas flows in small streams into the swirling air stream, which aids in good mixing. The burner ends with a ceramic tunnel 4 with an ignition hole 5.
Rice. 7.4. Forced air burner:
1 - nozzle; 2 - case; 3 - front plate; 4 - ceramic tunnel.
Forced air burners have a number of advantages:
-high performance;
- a wide range of performance regulation;
–The ability to work on heated air.
In the existing various designs of burners, the intensification of the formation of the gas-air mixture is achieved in the following ways:
–Division of gas and air flows into small flows in which mixture formation takes place;
–Supply of gas in the form of small streams at an angle to the air flow;
- twisting the air flow with various devices built into the inside of the burners.
Combined burners.
Combined burners are burners operating simultaneously or separately on gas and fuel oil or on gas and coal dust.
They are used in case of interruptions in the gas supply, when it is urgently necessary to find another type of fuel, when the gas fuel does not provide the required temperature regime of the furnace; gas supply for this is made only at a certain time (at night) to equalize the daily irregularities in gas consumption.
The most widespread are oil-gas burners with forced air supply. The burner consists of gas, air and liquid parts. The gas part is a hollow ring with a gas inlet and eight tubes for gas atomization.
The liquid part of the burner consists of an oil head and an inner tube ending in nozzle 1 (Fig. 7.5).
The fuel oil supply to the burner is regulated by a valve. The air part of the burner consists of a body, a swirler 3, an air damper 5, with which the air supply can be regulated. The swirler serves for better mixing of the fuel oil jet with air. Air pressure 2 ÷ 3 kPa, gas pressure up to 50 kPa, and fuel oil pressure up to 0.1 MPa.
Rice. 7.5. Combined oil-gas burner:
1 - oil nozzle, 2 - air chamber, 3 - swirler, 4 - gas outlet tubes, 5 - air regulating damper.
The use of dual fuel burners gives a higher effect than the simultaneous use of gas burners and oil burners or gas pulverized coal burners.
Combined burners are necessary for the reliable and uninterrupted operation of gas-using equipment and installations of large industrial enterprises, power plants and other consumers for which an interruption in operation is unacceptable.
Consider the principle of operation of a combined dust and gas burner designed by Mosenergo (Fig.7.6)
When operating on coal dust, a mixture of primary air with coal dust is fed into the furnace through the annular channel 3 of the central pipe, and the secondary air enters the furnace through the scroll 1.
Fuel oil is used as a reserve fuel, in this case a fuel oil nozzle is installed in the central pipe. When converting the burner to gas fuel, the oil nozzle is replaced by an annular channel through which the gas fuel is supplied.
In the central part of the channel, a pipe with a cast-iron tip 2 is installed. Tip 2 has oblique slots through which the gas escapes and intersects with the swirling air flow coming out of the volute 1. In improved burner designs, instead of slots 115 holes with a diameter of 7 mm are provided in the tip. As a result, the gas exit velocity is almost doubled (150 m / s).
Rice. 7.6. Combined gas and dust burner with central gas supply.
1 - a snail for twisting the air flow, 2 - a tip of gas supply pipes,
3 - an annular channel for supplying a mixture of primary air with coal dust.
New burner designs use peripheral gas flow, in which gas jets, which have a higher velocity than air ones, cross a swirling air stream moving at a speed of 30 m / s at a right angle. This interaction of gas and air flows ensures fast and complete mixing, as a result of which the gas-air mixture burns with minimal losses.
7.3. Automation of gas combustion processes.
The properties of gas fuel and modern designs of gas burners create favorable conditions for the automation of gas combustion processes. Automatic regulation of the combustion process increases the reliability and safety of operation of gas-powered units and ensures their operation in accordance with the most optimal mode.
Today, gas-powered plants use partial or complex automation systems.
Integrated gas automation consists of the following main systems:
- automatic control;
- safety automation;
- emergency signaling;
–Technical control.
The regulation and control of the combustion process is determined by the operation of gas appliances and units in a given mode and ensuring the optimal mode of gas combustion. For this, the regulation of the combustion process is intended for the automation of regulation of household, municipal and industrial gas appliances and units. Thus, a constant water temperature in the tank is maintained for storage water heaters, a constant steam pressure for steam boilers.
The gas supply to the burners of gas-using installations is terminated by the safety automatics in the event of:
- extinction of the torch in the furnace;
- lowering the air pressure in front of the burners;
- increasing the steam pressure in the boiler;
- an increase in the temperature of the water in the boiler;
- lowering the vacuum in the furnace.
Deactivation of these installations is accompanied by corresponding sound and light signals. No less important is the control of the gas content of the room in which all gas appliances and units are located. For these purposes, solenoid valves are installed that stop the gas supply in cases of exceeding the maximum permissible concentration in the ambient air of CH 4 and CO 2.
It is possible to achieve the optimal mode in the conditions of the technological process with the help of thermal control devices
The operating conditions of gas-using equipment determine the degree of its automation.
Remote control of gas-using installations is achieved through the use of monitoring and alarm devices.
Burner calculations.
In gas-oil furnaces equipped with modern burners with automatic control of the combustion process, it became possible to burn natural gases and fuel oil with small excess air practically with no or small amount of chemical incompleteness of combustion (less than 0.5%). Therefore, it is recommended to maintain the combustion process of these fuels with the excess air ratio behind the superheater not higher than 1.03 ÷ 1.05.
The principle of operation of a gas boiler is based on heating a circulating liquid passing through a heat exchanger. Heat is generated in the combustion chamber as a result of the operation of the gas burner of the heating device. It is from the high-quality setting, and then the operation of the burner, that the productive power of the boiler and its efficiency depend. Let's consider the main aspects of the selection and adjustment of a gas boiler burner in more detail.
How to choose?
What you need to pay attention to when choosing a burner for a boiler:
- productive capacity
- noise level during operation (applies to supercharged models)
- the type of heating equipment for which the burner is purchased
- type of fuel
- the pros and cons of this device
- foresee possible failures in the operation of the local gas supply line.
Taking these factors into account, it is possible to select the most suitable burner device for the boiler so that it works as efficiently as possible without burdening it with frequent preventive maintenance.
Combustion chamber of heating equipment
Gas boilers differ primarily in the design of the combustion chamber. It is of two types:
- open;
- closed.
Open the chamber is a fairly simple combustion device. It looks like this: a heat exchanger in the form of a coil of thin copper tubes is located above the burner. Thanks to the open design, the air necessary for the combustion reaction is supplied to the ignition site of the gas from the environment.
As a rule, there is enough air from the room (provided that there is good ventilation). But there are wall models with outside air intake, for which a special hole is mounted in the wall. Open combustion chambers require a chimney.
It is most often installed for models of floor-standing gas boilers, and was also used to complete the old-style boiler (while the ignition was made by an ignition burner).
Combustion chamber diagrams
Closed the combustion chamber is distinguished by the design of the heating block. The heat exchanger is located above the burner. The casing of the unit is closed, the combustion air is blown by a fan installed in the chamber. A coolant is passed through the double walls of the chamber, heating it, increasing the efficiency of the boiler. The gas is burnt almost completely, the combustion products are removed by a coaxial pipe under air pressure.
Burner types
According to their constructive, functional differences, burners are divided into:
By appointment:
- for industrial equipment of high power
- for household equipment.
By type of fuel used:
- devices for natural gas;
- devices for liquefied gas;
- universal devices.
Flame control:
- one-stage - capable of working on / off;
- two-stage (as a variant - models with smooth modulation) - work at full power, when the desired temperature is reached, the flame is halved;
- modulating - boilers with a modulating burner are distinguished by smooth regulation of the flame strength.
By the principle of work:
Boiler gas burner device
Atmospheric and fan burners differ in their structure. This is due to a different way of supplying oxygen to the chamber during fuel combustion.
Atmospheric burner device.
Air enters the combustion chamber directly from the room. Nozzles are located inside the channel of the burner device. Gas is fed into the nozzles, mixing with air, which also has access here. At a short distance from the nozzles, there are outlet slots through which the ready-made fuel mixture is supplied. An area of reduced pressure is created between the nozzles and the outlets, which contributes to the constant injection of mixing air.
The ignition burner is constantly running in the combustion chamber to ignite the main unit.
Fan burner device.
The device block consists of:
- engine;
- fan;
- automatic control unit;
- reducer;
- air pressure switch;
- fuel mass mixer.
Air is blown from the outside by a fan and fed into the combustion chamber to form a fuel substance. The air / gas ratio can be adjusted using a damper and a fan.
Burner flame
One of the indicators of correct burner operation is the color of the flame. Gas equipment is characterized by an even bluish flame without admixtures of other colors. The presence of blotches of yellow, red indicates that the burner does not work well, this reduces the efficiency of the heating equipment.
First of all, this concerns injection burners, but sometimes it is also typical for fan burners. The flame may simply not have enough oxygen. Also, dust and other small debris can get along with the air, which will clog the device, reducing the efficiency of the boiler. All this directly affects the flame. If it hums, the burner is working loudly, the fire has changed color - it is necessary to adjust the correct operation of the device.
When do you need to adjust the burner flame?
Atmospheric gas burners for heating equipment fail more often. It is equipped with both wall-mounted and floor-standing boiler models. An injection burner of floor-standing equipment reduces its efficiency for various reasons:
- Burner output is too high. It happens when a high power burner is purchased for small heating equipment. At the same time, there is not enough space for combustion, the flow of air for such a power is weak, which leads to the transition of the flame from blue to yellow, the burning of the combustion chamber, chimney.
- If the chimney is poorly cleaned, the draft of the boiler deteriorates. In this case, the waste products of combustion are poorly removed, the flow of air is small. This worsens combustion, the flame turns yellow.
- A defect in the burner itself does not make it possible to correctly adjust the complete combustion of the fuel.
- Due to pressure drops in the gas supply system, well-regulated equipment can discharge large quantities of unused gas into the chimney. In part, it settles in soot, soot. A large layer of soot reduces traction, increases fuel consumption.
- Start-up of heating equipment after repair.
- The presence of extraneous noise during the operation of the boiler, gas burner.
- Change of fuel type.
Equipment setup
Floor standing gas boilers with atmospheric burners can be adjusted independently. The pressurized systems are regulated by an automatic control unit and do not require additional adjustment.
Scheme of actions when setting up single-stage equipment:
- Install the device on the boiler.
- Connect to gas connection.
- Check for absolute tightness.
- Remove the burner housing.
- Using a pressure gauge, measure the gas pressure at the inlet.
- Connect to electricity. Make sure that the jumpers, phases are connected correctly.
- Place a gas analyzer in the chimney.
- Start the device.
- Use a pressure gauge to read the pressure at the outlet of the burner block. The pressure readings must correspond to the parameters indicated in the data sheet.
- Adjust the air supply with an air damper.
- The readings of the gas analyzer must also comply with all standards for the installation of gas equipment.
The adjustment of the gas equipment must be carried out by specialists. The simplest open-type boilers can be configured independently if you have certain skills, knowledge of the burner block design. The efficiency of the boiler, the level of its efficiency, and fuel consumption depend on the quality of the burner. It is possible to superficially determine that the equipment is malfunctioning by the changed flame of the burner.
Life far from the equator dictates its own laws. As the outdoor temperature drops, the houses inside cool down. In this review, we will consider a solution to the problem by choosing the best gas heaters - from portable (for a tent) to convectors for a home or summer cottage that can replace a gas boiler.
Types of gas heaters
Gas convectors
Such heaters can have a closed and open combustion chamber. Models of a closed type for gas combustion take air from the street and remove the combustion products there through a special pipe laid through the wall. They are well suited for home or summer cottages and can become an alternative to a gas boiler. Models with an open combustion chamber are not very suitable for residential applications or require the use of a vertical chimney.
Catalytic gas heaters
Devices of this type work due to the oxidation of substances on the surface of the catalyst, in which a large amount of heat is released. The process takes place almost silently and without flame. The catalytic combustion method is more reliable, efficient and safer than conventional infrared heaters.
Ceramic gas heaters
By analogy with electric counterparts, such heaters work due to directional thermal radiation and heat not the air, but the surfaces of walls, objects, as well as people present in the room. A gas burner acts only as a heating source. The use of ceramic plates allows complete combustion of the fuel and eliminates harmful emissions.
Heat gas cannons
They have a cylindrical shape and operate on the principle of a fan heater, in which a gas heat generator acts as a heating element. They operate on bottled gas, and the power is usually regulated by a reducer.
