Scheme of the injection burner. Low pressure injection burners. The disadvantage of the injection burner
Torches are the main working tool for gas welding, soldering, surfacing and heating. There are two main classes:
- injection burners,
- non-injector (Fig. 1).
IN injection burners low-pressure combustible gas (below 1 kPa) is supplied to the mixing chamber by injecting it with a jet of oxygen flowing from the injector. IN fuelless burners combustible gas and oxygen are supplied at approximately the same pressure (50 ... 100 kPa).
Mainly used by hand injection burners universal and specialized purposes. The most common are universal injection-type burners operating on acetylene: low-power burners G2-05 (Fig. 2) and medium-power burners GZ-06. They have a similar design and differ mainly in the number and numbers of completed tips. universal burners operating on acetylene substitute gases include burners GZU-3-02 and GZU-4.
Figure 1. Welding torches:
injection - a; non-injector - b; 1 - mouthpiece; 2 - tip tube; 3 - mixing chamber; 4 injector; 5, 6 - control valves; 7- trunk; 8 - tube; 9, 10 - nipples
Picture 1. Injection burnerG2-05 low power
Unlike universal burners, specialized burners are designed to perform one technological operation (surfacing, soldering, cutting).
Other materials related to the topics "
Burners: injection and non-injection
Gas welding, surfacing, cutting, soldering":
By posting an ad in
The welding torch is the main tool of the gas welder in welding and surfacing. A welding torch is a device used to mix combustible gas with oxygen and produce a welding flame. Each burner has the ability to adjust the power, composition and shape of the welding flame.
injection burner
An injection burner is a burner in which the supply of combustible gas to a mixing
chamber is carried out by sucking it with a jet of oxygen flowing from a large
speed from the injector hole.
This process of sucking gas at a lower pressure with a jet of oxygen supplied at a higher pressure is called injection, and burners of this type are called injection burners.
Rice. 65. Injection burner (18)
1 welding nozzle;
2-mixing tube(tip );
3-mixing nozzle;
4-cap nut; 5-injector area;
6-oxygen valve;
7 - oxygen hose connection, right-hand thread R 1\4;
8-valve for acetylene;
9-hose connection with acetylene, left-hand thread R 3\8
Oxygen from the cylinder under working pressure through the nipple, tube and valve 6 enters the injector nozzle 5. Coming out of the injector nozzle at high speed, oxygen creates a vacuum in the acetylene channel, as a result of which acetylene passes through the nipple 9, the tube and valve 8 is sucked into the mixing chamber 3. In this chamber, oxygen is mixed with combustible gas, forming a combustible mixture. The combustible mixture, leaving through the mouthpiece, is ignited and burned, a welding flame is formed. The gas supply to the burner is regulated by an oxygen valve 6 and an acetylene valve 8 located on the burner body. Replaceable tips are connected to the body of the burner with a union nut.
Heating the torch tip reduces oxygen injection and reduces the vacuum in the injector chamber, which reduces the flow of acetylene to the torch. Since the oxygen supply to the burner remains constant, the acetylene content in the gas mixture decreases and, consequently, the oxidizing effect of the welding flame increases. To restore the normal composition of the welding flame, the welder, as the torch tip heats up, must increase the flow of acetylene into the torch by opening the acetylene valve of the torch.
When the burner mouthpiece is clogged, the pressure of the combustible mixture in the mixing chamber increases, the combustible mixture is enriched with oxygen, which leads to an increase in the oxidizing effect of the welding flame.
Advantage of injection burner:
- the burner works on combustible gas of both medium and low pressure
Disadvantage of the injection burner:
- inconstancy of the composition of the combustible mixture
Non-injector burner
A non-injector burner is a burner in which combustible gas and oxygen are supplied at approximately the same pressure. They do not have an injector, which is replaced by a simple mixing nozzle screwed into the burner head tube.
Rice. 66. Non-injector burner (18)
For the formation of a normal welding flame, the combustible mixture must flow out of the torch mouthpiece channel at a certain speed. This speed must be equal to the burning speed. If the flow rate is greater than the burning rate, then the flame breaks away from the mouthpiece and goes out. When the outflow rate of the gas mixture is less than the burning rate, the combustible mixture ignites inside the tip.
The disadvantage of a non-injector burner:
- burners are less versatile, as they only work on medium pressure fuel
Gas welding is welding using molten metal. In this process, the edges of the metal parts of the parts are heated to the melting temperature by the flame of a gas burner.
The high temperature at which metal melts occurs is formed from the ignition of a gas-oxygen mixture. To fill the voids that occur when the edges of the metal are aligned, a molten filler wire is used.
Torches for gas welding.
A torch is used to produce the welding flame needed to work with metals. With its help, you can control the power, the volume of the flame within the established limits. Despite all the outward simplicity of the product, the torch is a complex and significant element in welding.
Figure 1 shows a gas burner flame with temperature readings.
According to their design, gas welding torches are divided into:
- injection;
- non-injector.
According to the fuel used:
- acetylene;
- for other gases and liquid fuels.
In order of use, they can be:
- manual,
- machine.
Injector and non-injector torches for gas welding.
The design presence of a jet pump in the burner is determined by the level of pressure at which fuel is supplied to it. If it is high, then additional injection is not required, the fuel is supplied under its own. At low pressure, more gas is needed, so a forced supply using an injector is used. To create a welding flame, you need to get a good mixture of oxygen and fuel in the mixing chamber of the burner.
A burner without an injector has a simpler device. Fuel and oxygen are supplied to the mixer simultaneously using a supply system consisting of hoses, the required number of taps (valves), nipples. A homogeneous mixture is formed in the mixer.
A homogeneous mixture flows through the tip tube to the mouthpiece, ignites and creates a flame for welding. In order for the combustion process to meet the necessary requirements, the pressure with which the mixture is supplied from the mouthpiece must be within strictly defined limits. If the speed is higher than the set one, the flame, breaking away from the cut of the burner, will go out. If lower, then the mixture, getting inside the burner, will explode in it. The flow rate of the combustible mixture (acetylene-oxygen) varies from 70 to 160 m/s, it depends on the type of mouthpiece, channel size, percentage composition of the mixture.
High pressure burners can use hydrogen or methane. It is easy to use and device. But, in comparison with low-pressure injection burners, they are used much less frequently.
Low pressure burner operation.
Oxygen under high pressure (about 4 atmospheres) enters the burner through a supply system consisting of a nipple and a control valve. Passes through the injector at high speed. Under the action of an oxygen jet, a pressure below atmospheric pressure is created in the jet pump chamber and combustible gas is sucked in. It enters through the nipple and valve into the injector chamber, and then into the mixing chamber, combines with oxygen, and enters the mouthpiece through the channel at a speed within strict limits.
The oxygen consumption does not change, it is not affected by external factors, in contrast to the consumption of the gas used. An increase in the temperature of the mouthpiece and the tip of the burner, a change in pressure, an increase in resistance increase the consumption of acetylene.
Other types of burners.
In some industries, gas welding torches that run on liquid fuels such as gasoline or kerosene have found use. The principle is based on the spraying of a kerosene-oxygen mixture and the evaporation of small-drop fuel from heating from the mouthpiece.
Burners currently in use must comply with the following safety requirements for trouble-free operation:
- the welding flame must be of a certain shape;
- adjusting the flame within the required limits;
- resistance to external influences and safety of operation;
- ease of use.
In such burners, the formation of a gas-air mixture occurs by sucking primary air into the burner due to the energy of the gas jet. This phenomenon is called injection. Depending on the volume of injected primary air, the burners are of partial and full mixing.
IN partial burners(incomplete) confusion only part of the air necessary for combustion is injected, and the rest of the air enters the combustion zone from the surrounding space. These burners are also called atmospheric or torch. They are most common and are used for gas stoves, water heaters, sectional boilers, small heaters.
The device of the atmospheric injection burner is shown in fig. 2.6. The main parts of the injection burner are the primary air regulator 7, the gas nozzle, or the nozzle 1, mixer and collector 6.
Rice. 2.6. Injection atmospheric gas burners: A - low pressure; b- for a pig-iron copper; I- nozzle, 2- injector;
3- confuser; 4- diffuser; 5- holes; 6- collector; 7- primary air regulator
Primary air regulator is a rotating disk or washer and serves to regulate the amount of primary air entering the burner.
gas nozzle, or nozzle, serves to impart a speed to the gas jet, which ensures the injection of the necessary air.
Mixer burner consists of three parts - injector 2, confuser 3 and diffuser 4. Injector serves to suck air and create a vacuum. confuser serves to equalize the jet of the gas-air mixture. IN diffuser there is a final mixing of the gas-air mixture and an increase in its pressure due to a decrease in speed. From the diffuser, the gas-air mixture enters manifold 6, which distributes the gas-air mixture through the holes. The shape of the collector and the location of the holes depend on the type of burners and their purpose.
Important characteristics of incompletely mixed injection burners are the injection coefficient - the ratio of the volumes of injected air and the air required for complete combustion of the gas, and the injection ratio - the ratio of the volume of primary air to the gas flow rate of the burner.
The advantage of injection burners is the property of their self-regulation - maintaining a constant proportion between the volumes of gas supplied to the burner and injected air.
However, the limits of stability of injection burners are limited by the possibilities of separation and flashback of the flame. This means that it is possible to increase or decrease the gas pressure in the burner only within certain limits.
Full mixing burners they inject all the air necessary for burning the gas, which is ensured by the use of high pressure gas. The most common designs of fully mixed gas burners operate in the pressure range from 5 kPa to 0.5 MPa.
Burner type IGK(injection burner designed by Kazantsev) consists of a primary air regulator, a nozzle, a confuser, a mixer, a nozzle and a plate stabilizer.
Primary air regulator The burner simultaneously performs the functions of a noise suppressor, which is created due to the increased speeds of the gas-air mixture.
Plate Stabilizer ensures stable operation of the burner without separation and flashover of the flame into the burner in a wide range of loads. The stabilizer consists of steel plates with a thickness of 0.5 mm and a distance between them of 1.5 mm. The stabilizer plates are pulled together by steel rods, which, on the path of the gas-air mixture, create a zone of reverse currents of hot combustion products and continuously ignite the gas-air mixture. Such a stabilizer device eliminates flame separation.
In other designs of burners, flame separation is prevented by providing the burners with ceramic tunnels or a device in the furnace of slides made of refractory materials that are heated to high temperatures (above the ignition temperature of the gas), ensuring continuous ignition of the gas-air mixture.
Burners in which the formation of a gas-air mixture occurs due to the energy of a gas jet are called injection. The main element of an injection burner is an injector that draws air from the surrounding space into the burners.
Depending on the amount of injected air, the burners can be with incomplete air injection and with complete pre-mixing of gas with air.
Burners with partial 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 (Fig. 3, a).
The main parts of injection burners are the primary air regulator, nozzle, mixer and manifold (see fig. 3).
Rice. 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
Primary air regulator 7 is a rotating disk 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 such a speed that provides the suction of the necessary air. The burner mixer consists of three parts: injector, confuser and diffuser. Injector 2 creates vacuum and air suction. The narrowest part of the mixer is the confuser 3, which equalizes the jet of the gas-air mixture. In the diffuser 4, the final mixing of the gas-air mixture and an increase in its pressure due to a decrease in speed take place.
From the diffuser, the gas-air mixture enters the collector 5, which distributes it through the holes 6. The shape of the collector and the location of the holes depend on the type of burners and their purpose.
The distribution manifold of the burners of DHW cylinders has the shape of a circle; for burners of instantaneous water heaters, the collector consists of parallel tubes; for units with an elongated firebox, an elongated collector; burners for a cast-iron boiler (Fig. 3, b) have a collector in the form of a rectangle with a large number of small holes.
Low pressure injection burners have a number of positive qualities, due to which they are used in household gas appliances, as well as in gas appliances for catering establishments and other domestic gas consumers. Injection burners are also used in cast iron heating boilers.
The main advantages of low-pressure injection burners are: simple design, stable operation of burners when loads change; reliability and ease of maintenance; noiselessness of work; the possibility of complete combustion of gas and work at low gas pressures; lack of pressurized air supply.
An important characteristic of incompletely mixed injection burners is the injection ratio - the ratio of the volume of injected air to the volume of air required for complete combustion of the gas. So, if complete combustion of 1 m3 of gas requires 10 m3 of air, and the primary air is 4 m3, then the injection ratio is 4: 10 = 0.4.
A characteristic of the burners is also the injection ratio - the ratio of primary air to the gas flow rate of the burner. In this case, when 4 m3 of air is injected per 1 m3 of combusted gas, the injection ratio is 4.
The advantage of injection burners is their self-regulating property, i.e. maintaining a constant proportion between the amount of gas supplied to the burner and the amount of air injected at a constant gas pressure.
The limits of stable operation of injection burners are limited by the possibilities of separation and flashover of the flame. This means that it is possible to increase or decrease the gas pressure in front of the burner only within certain limits.
Burners with complete pre-mixing of gas with air. The injection of all the air necessary for the complete combustion of the gas is provided by the increased pressure of the gas. Complete gas mixing burners operate in the pressure range from 5000 Pa to 0.5 MPa. They are called medium pressure injection burners and are mainly used in heating boilers and for heating industrial furnaces. The thermal power of the burners usually does not exceed 2 MW. The main difficulties in increasing their power are the difficulty of dealing with flashback and the bulkiness of mixers.
These burners produce a low-luminosity flame, which reduces the amount of radiant heat transferred to the heated surfaces. To increase the amount of radiation heat, it is effective to use solids in the furnaces of boilers and furnaces, which perceive heat from combustion products and radiate it to heat-receiving surfaces. These bodies are called secondary emitters. Refractory walls of tunnels, walls of furnaces, as well as special perforated partitions installed in the path of movement of combustion products are used as secondary emitters.
Burners with complete pre-mixing of gas with air are divided into two types: with metal stabilizers and refractory nozzles.
An injection burner designed by Kazantsev (IGK) consists of a primary air regulator, a nozzle, a confuser, a mixer, a nozzle, and a plate stabilizer (Fig. 4).
Rice. 4. IGK injection burner:
1 - stabilizer; 2 - nozzles; 3 - confuser; 4 - nozzle; 5 - primary air regulator
The primary air regulator 5 of the burner simultaneously performs the functions of a noise suppressor, which is created due to the increased speeds of the gas-air mixture. The plate stabilizer and flashback in a wide range 7 ensures stable operation of the burner without separation and flashover of the flame in a wide range of loads. The stabilizer consists of steel plates 0.5 mm thick with a distance between them of 1.5 mm. The stabilizer plates are pulled together by steel rods, which, on the path of the gas-air mixture, create a zone of reverse currents of hot combustion products and continuously ignite the gas-air mixture.
In burners with refractory nozzles, natural gas is burned to form a low-luminosity flame. In this regard, the transfer of heat by radiation from the flame of burning gas is insufficient. In modern designs of gas burners, the efficiency of using gas has increased significantly. The low luminosity of the gas flame is compensated by the radiation of incandescent refractory materials during gas combustion using the flameless combustion method.
The gas-air mixture in these burners is prepared with a slight excess of air and enters the hot refractory channels, where it is intensely heated and burned. The flame does not leave the channel, so this process of gas combustion is called flameless. This name is conditional, since there is a flame in the channels.
The gas-air mixture is heated from the hot walls of the channel. In places of expansion of the channels and near bluff bodies, zones of retention of hot combustion products are created. Such zones are stable sources of constant heating and ignition of the gas-air mixture. On fig. 5 shows a flameless panel burner. The gas entering the nozzle 5 from the gas pipeline 7 injects the required amount of air, regulated by the primary air regulator 6. The resulting gas-air mixture enters the distribution chamber 3 through the injector 4, passes through the nipples 2 and enters the ceramic tunnels 1. In these tunnels, the gas-air mixture is burned. Distribution chamber 3 from ceramic prisms 8 is thermally insulated with a layer of diatomaceous earth, which reduces heat removal from the reaction zone.
Flameless combustion of gas has the following advantages: complete combustion of gas; the possibility of burning gas with small excesses of air; the possibility of achieving high combustion temperatures; combustion of gas with a high thermal stress of the combustion volume; transfer of a significant amount of heat by infrared rays.
Existing designs of flameless burners with refractory nozzles according to the design of their firing part are divided into burners with nozzles having channels of irregular geometric shape; burners with nozzles having channels of the correct geometric shape; burners in which the flame is stabilized on the refractory surfaces of the furnace.
Rice. 5. Flameless panel burner:
1 - tunnel; 2 - nipple; 3 - distribution chamber; 4 - injector; 5 - nozzle; 6 - air regulator; 7 - gas pipeline; 8 - ceramic prisms
The most common burners with nozzles of the correct geometric shape. Refractory nozzles of such burners consist of ceramic tiles measuring 65 x 45 x 12 mm. Flameless burners are also called infrared burners.
All bodies are sources of thermal radiation arising due to the oscillatory motion of atoms. During radiation, the thermal energy of substances is converted into the energy of electromagnetic waves, which propagate from the source at a speed equal to the speed of light. These electromagnetic waves, propagating in the surrounding space, collide with various objects and easily turn into thermal energy. Its value depends on the temperature of the radiating bodies. Each temperature corresponds to a certain range of wavelengths emitted by the body. In this case, the transfer of heat by radiation occurs in the infrared region of the spectrum, and burners operating on this principle are called infrared burners (Fig. 6).
Through nozzle 4 (see Fig. 6, a), the gas enters the burner and injects all the air necessary for complete combustion of the gas. From the burner, the gas-air mixture enters the collection chamber 6 and then goes to the fire holes of the ceramic tile 2. To avoid flashback of the flame, the diameter of the fire holes must be less than the critical value and be 1.5 mm. The gas-air mixture leaving the fire chambers is ignited at a low speed of its escape in order to avoid flame separation. In the future, the escape rate of the gas-air mixture can be increased (fully open the valve), since ceramic tiles heat up to 1000 ° C and give off part of the heat of the gas-air mixture, which leads to an increase in the speed of flame propagation and prevention of its separation.
Rice. 6. Infrared burners:
a - burner diagram: 1 - reflector; 2 - ceramic tiles; 3 - mixer; 4 - nozzle; 5 - body; 6 - collection chamber; b, c and d - burners GII-1, GII-8 and PS-1-38, respectively
Ceramic tiles have about 600 cylindrical fire channels, which is about 40% of the surface of the tiles.
Tiles are connected to each other with a special putty, consisting of a mixture of fireclay powder with cement.
If infrared burners operate on medium pressure gas, then special plates made of porous heat-resistant materials are used. Instead of cylindrical channels, they have narrow curved channels that end in expanding combustion chambers.
When gas is burned in numerous channels of various nozzles, their outer surfaces are heated to a temperature of about 1000 °C. As a result, the surfaces turn orange-red and become sources of infrared rays, which are absorbed by various objects and cause them to heat up.
On fig. 6, b ... d shows the most common types of infrared burners. GII-1 burners have 21 ceramic tiles, a reflector and a junction box. GII burners can be used to heat rooms and various equipment. Burners are also used for heating outdoor areas (sports fields, cafes, summer-type rooms, etc.).
The GK-1-38 burner is successfully used for heating walls and plaster under construction, heating people working in winter conditions. The burner can operate on natural and liquefied gases.
