RU2284434C2 - Method of and device for combustion of fuel - Google Patents

Abstract

FIELD: mechanical engineering; combustion of fuels.

SUBSTANCE: invention relates to combustion of fuels, mainly liquid ones, including viscous fuels and contaminated fuels of wide fraction composition in domestic and industrial furnaces. According to proposed method, fuel is mixed with primary air to form enriched fuel mixture and is combusted with obtaining of reducing products of incomplete combustion, and secondary air fed to incomplete combustion products in form of jets inclined to direction of flow which are twisting around their axes forming spiral swirl air strings on which reducing combustion products are afterburned, and crossing air swirls are formed in zone of combustion twisted in opposite sides around their axes, part of twisted swirl strings are divided by air jets non-twisted around their axes, and at combustion of low-volatile fuel mixture is fed to zone of fuel and air mixing in form of crossed jets of fuel gas and air twisted around their axes. Proposed device contains fuel feed unit, primary air-fuel mixer and combustion chamber with slot channels with fitted-in at least two corrugated spacers with inclined corrugations contacting by sides, direction of tilting of corrugations at adjacent spacers is opposite to form crossed channels. Combustion chamber is made in form of set of corrugated spacers with corrugations inclined in opposite directions and butt-jointed with interlapping. Inlet side of part of corrugated spacers is provided with self-contained manifold isolated from air space.

EFFECT: provision of complete combustion, uniform temperature field, reduction of toxicity of combustion products.

6 cl, 11 dwg

Description

The invention relates to heat engineering and is intended for the combustion of mainly liquid, including viscous, contaminated fuels of a wide fractional composition in domestic furnaces and industrial furnaces.

Known methods of burning liquid fuels by spraying them in an oxidizer stream and stabilizing the flame at reverse currents, as well as realizing their combustion chambers containing a fuel nozzle mounted coaxially to the swirl and placed in the combustion chamber with openings for supplying secondary air made in its walls [1] .

This technical solution is widely used in the power system and provides high completeness and efficiency of combustion. Its disadvantage is the non-uniformity of the temperature field caused by large-scale turbulence during stabilization at reverse currents and increased release of toxic substances in the flame due to the uneven composition of the combustible mixture.

The closest is the method of burning fuels, which consists in the fact that the fuel is mixed with primary air, an enriched combustible mixture is formed, it is burned to produce reducing products of incomplete combustion, which are burned into the secondary air jets swirled to opposite sides of the flow axis that are opposite to the flow axis forming swirling flows of combustion products [2]. This method provides a significant intensification of mixture formation. We select it for the prototype of the proposed method.

In terms of the device, the closest technical solution is a device for burning fuel, containing a fuel supply unit connected to a primary air mixer with fuel, which are installed in the combustion chamber with rows of slot channels made therein for supplying secondary air to the combustion zone and corrugations [3].

The disadvantages of this method [2] is the uneven composition of the combustible mixture, which leads to heterogeneity of the temperature field and the release of toxic substances, such as CO, products of chemical underburning, as well as nitrogen oxides during the burning of locally depleted fuel mixtures.

The disadvantages of the known device [3] is the low efficiency of mixing the components of the combustible mixture, the increased metal consumption of the combustion chamber.

The aim of the invention is to increase efficiency and reduce combustion toxicity.

This goal in the proposed method and the device implementing it is ensured by the fact that the fuel is mixed with primary air, an enriched combustible mixture is formed, it is burned to produce incomplete recovery products that are burned into secondary air jets that are inclined to the flow axis and form swirling flows of combustion products, the jets of adjacent swirling streams are additionally twisted around the axis of the jets with the formation of rows of interconnected vortex cords, while the input of each feriynoy pair of oppositely swirling flows of air is carried downstream with respect to the central stream.

In addition, alternating vortex cords formed in the combustion zone are twisted in opposite directions around their axes, part of the twisted vortex cords are separated by spiral jets of air not twisted around their axes, and a gaseous combustible mixture is supplied to the mixing zone of the main fuel and air in the form of a system of crossed twisted around their axes of jets of combustible gas and air.

In the proposed device, this goal is ensured by the fact that when it is executed, including a fuel supply unit connected to a primary air mixer with fuel, which are installed in the combustion chamber with rows of slotted channels for supplying secondary air and corrugations made in it, at least at least two contacting corrugated spacers with inclined corrugations, and the direction of the corrugations of adjacent spacers is opposite and forms crossed channels. In addition, the input side of the corrugated spacers part is provided with autonomous collectors isolated from the air cavity.

In Fig.1 shows a schematic longitudinal section of an example of the proposed device when performing its annular combustion chamber and using a porous wick in its power system as a fuel supply unit, in Fig.2, 3 - places M and H on an enlarged scale, in Fig.4 - section along BB-1 of figure 1, figure 5 is a section along BB-1 of figure 1, figure 6 is a section along A-A of figure 1, figure 7 is a section along G-D of figure 6 , a diagram of the flow of air and the formation of vortex cords, Fig. 8 is a longitudinal section of a fragment of a combustion chamber when its wall is made of overlapped ingly spacers and installation of collector 9 - fragment of the combustion chamber wall corrugated ceramic spacers, Figure 10 - view along arrow D 7, 11 - an embodiment of the proposed device with bubbling mixer.

The method of burning fuels consists in the fact that the fuel is mixed with primary air, an enriched combustible mixture is formed, and it is burned to produce reducing products of incomplete combustion. Next, rows of secondary air jets oppositely inclined to the flow axis are introduced into the flow of reducing combustion products, which form oppositely swirling flows of the combustible mixture of secondary air with reducing combustion products. Adjacent air jets, twisted in opposite directions relative to the axis of the flow, additionally twist around the axes of the jets themselves and thus form rows of interconnected vortex cords, the peripheral row downstream with respect to the central ones. The twist of each of the vortex cords can be carried out in the same direction as the neighboring ones, but to increase the range and reduce their dissipation in the combustion zone, the neighboring vortex cords are twisted in opposite directions, whereby they form the so-called paired whirlwinds. Also, to increase the range of vortex cords, adjacent vortex cords are separated by jets of secondary air not twisted around their axes. Moreover, the level of turbulence in the mixture formation zone increases by 50-70%, which intensifies heat and mass transfer in the mixture formation zone and leads to an increase in the rate of afterburning of products of incomplete combustion in secondary air. To intensify the combustion of low-volatile fuels, a combustible mixture is supplied to the mixing zone of the main fuel with air in the form of a system of crossed jets of combustible gas, such as methane, and air forming a stand-by combustion torch, twisted around their axes.

The embodiment of the device of FIG. 1 comprises a fuel supply unit 1 in the form of an annular body 2 provided with a manifold 3 connected to the housing with openings 4, and a pipe 5 with a dispenser 6. A porous wick 7 is tightly installed in the housing 2, and a manifold 8 connected pipe 9 with a source of compressed gas or air. A combustion chamber 10 is attached to the housing 2 in the form of a set of metal rings 11 and 12 with holes 13 connected to one another, for example, by spot welding using corrugated spacers 14 and 15 adjacent to each other with oblique corrugations 16 and 17, the angle of which in corrugated spacers adjacent to one another, it is made opposite (for example, with right-handed and left-handed corrugations). The upper ring 11 is hermetically connected to the casing 18 having a pipe 19 for supplying air to it under a slight overpressure. A refractory divider 21 may be attached to the central part 20 of the combustion chamber 10. The dispenser may be of any known type, for example float, and should be equipped with means for regulating the fuel level in the housing 2, for example, mounted relative to it with the possibility of vertical movement.

The lower rings 11 and 12 with holes 13 form, together with the wick 7, a primary air mixer 22 with fuel. Spacers 14 and 15 with right 16 and left 17 corrugations when they are joined by the side surfaces form crossed channels 23 and 24, and with walls 11 and 12 inclined, swirling "right" and "left" channels 25 and 26 (Figs. 1, 2, four). Three or more alternating corrugated spacers 14 and 15 and “right” and “left” corrugations can be installed in the joints of rings 11 and 12 with each other (Figs. 1, 3, 5).

The proposed implementation of the device provides not only the annular shape of the combustion chamber 1. It can also be made flat-shaped, round or other shape, depending on the desired shape of the heated surface (Fig.8-11). The walls 10 and 20 of the combustion chamber can also be of various configurations, depending on the type of fuel burned, heat intensity, and the required temperature of the combustion products. So the elements 11 and 12 of the chamber 10 can be cylindrical, conical (Figs. 5, 7), different tiers have a different inclination to the axis and different permeability and the area of the passage section, the inner cavity 27 of the chamber 10 can have a prechamber when burning low-grade fuels (Fig. eleven).

In particular, the “left” and “right” corrugated spacers 14 and 15, when made conical or flat, can be overlapped and form an air-permeable portion of the wall of the combustion chamber 10. Moreover, they can only be connected to each other and form a homogeneous section (Fig. 11), but can be separated by periodically installed smooth, not corrugated sections 12 (Fig. 8). The input parts of the corrugated spacers 14 and 15 can be equipped with autonomous collectors 28 with a pipe 29 for supplying an additional gaseous working fluid, for example waste combustible gas (Fig. 8, 11). The manifold 28 can be installed at the mixer 22 of fuel and primary air for heating non-volatile fuel and its evaporation. It can also be developed over the surface of the combustion chamber and form an evaporator into which easily evaporated fuel can be supplied.

Corrugated spacers 14 and 15 can be made of fireproof ceramics, for example, in the form of rings (Figs. 9, 10) with spiral channels 24, 25 and 26 molded into them, curled in opposite directions. The inclination angle of the generatrix of these rings 14 and 15 may be different from tier to tier, varying from 90 ° to 0 ° to the axis of the combustion chamber.

The fuel supply unit 1 can be made in any known manner, depending on the type of fuel used, specific flow rate and purpose of the device.

In the case of using relatively light fuels (kerosene, diesel oil, gas oil), an evaporative wick 7 in housing 1 can be used for domestic furnaces; in the case of industrial furnaces, standard centrifugal nozzles for fuel and air flow swirls for primary air can be used. For heavier, but cleaner fuels such as heating oil, you can use a porous wick with an additional supply of atomizing gas (figure 1). For viscous fuels such as fuel oil, it is advisable to use bubbling mixture formation (11). The mixer 22 thus comprises a housing 1 with a perforated collector 8 located near its bottom, connected by a pipe 9 to a source of compressed air.

The proposed device operates as follows.

When burning light fuel such as kerosene (Fig. 1), it is supplied through the dispenser 6 to the manifold 3 and through the hole 4 it fills the housing 2, wetting the porous wick 7. Starting torch, for example a gas manifold 28 (Fig. 8) with corrugated spacers 14 and 15 , warms up the wick 7 and ignites the evaporating fuel, which partially burns in the air jets coming through the openings 13 to the mixer 22, and partially evaporates and enters, together with the products of incomplete combustion, into the cavity 27 of the combustion chamber 10, where secondary air enters from the casing 18 through p the poisons of the holes 13 in the rings 11 and 12 and through the channels 23-26 in the corrugated spacers 14 and 15. In this case, the air in the channels 25 and 26 formed by the corrugations 16 and 17 of the spacers 14 and 15 and the smooth walls of the rings 11 and 12 expire in the form inclined to the axis of the spiral jets. As for the air in the channels 23 and 24, each of the jets moving along the channels 24 is twisted around its axes by air jets moving along the channels 23 (see Fig. 6), and accordingly each stream in the channels 23 will be twisted by jets in the channels 24 (FIGS. 6, 7), and from the output edges of the channels 23 and 24 of the corrugated spacers 14 and 15, families of inclined vortex cords inclined to the camera axis will flow, having the same direction of rotation around their axes and opposite relative to the axis of the combustion chamber (in the case of its execution in the form of a body of BP scheniya - 7).

These vortex cords intensively mix enriched products of incomplete combustion of fuel with secondary air and burn them in it. Various passage sections of the channels and, correspondingly, their shapes make it possible to localize the afterburning in the center of the cavity 27 or, on the contrary, to disperse it throughout its volume. If three or more corrugated spacers 14 and 15 are installed between the rings 25 and 26, smooth jets form, and in the channels 23 and 24 of the inner ring vortex cords form, twisted in one direction around the camera axis and in opposite directions around the axes, forming the so-called paired whirlwinds. Such vortices do not dissipate in space much longer than single ones and are suitable for sufficiently long and powerful burners.

In the case of fuel supply due to its evaporation, air supplied by gravity due to natural draft is sufficient. If a forced fuel supply through the nozzle is used, a forced air supply through the pipe 19 to the casing 18 is necessary and an autonomous air supply to the mixer 22 is possible.

If a heavier but cleaner fuel, such as furnace oil, is used in the evaporative system, the combustion can be intensified by supplying compressed air through the pipe 9 and the manifold 8 to purge the porous wick moistened with fuel 7. When the wick is made, the air in the wick will be anisotropic and tightly installed in the housing 2 spray the wetted fuel into ultra fine droplets that enter the mixer 22 for burning. This tool can also be used to ignite the device, and then turn off the supply of compressed gas in the pipe 9.

With a significant flow rate of the device and the execution of the walls of its combustion chamber 10 in the form of a lap set of spacers 13 and 14 (Fig. 8), the combination of spiral jets and vortex cords crossed in space 27 of chamber 10 and mix the combustible mixture coming from mixer 22. In this case, especially when using low-volatile fuels, it is advisable to supply gaseous fuel through the pipe 29 to the manifold 28, which, similar to the air passing through the adjacent rows of corrugated spacers 13 and 14, also form a conglomerate of crossed vortex cords and spiral jets. Depending on the required range of the gaseous fuel jets, the corrugated rings can be made according to the variants in FIGS. 2 or 3. The torch of the gaseous fuel burner will warm up the fuel supply unit 1 and stabilize combustion. At start-up, gaseous fuel inlet can be used as a starting burner.

When burning long-burning heavy-fraction fuels, it is advisable to use a variant of the device according to Fig. 9, in which the combustion chamber is made of lap-shaped corrugated spacers (flat or ring-shaped) made of refractory ceramic. At the same time, due to the poor thermal conductivity of the ceramics, it is highly heated during operation of the device, and the air flowing through its channels 23 and 24 is additionally heated to a high temperature, which intensifies the burning out of heavy fuel fractions in the crossed spiral cords formed by them.

In the case of using a bubbler mixer 1 (11), viscous fuel fills the bath at the bottom of the housing 2, and the compressed air supplied through the pipe 9 and the perforated manifold 8 enters the fuel layer in the housing 1 in the form of small bubbles and foams the fuel. Fuel-air foam rises to the holes 13 and the corrugated spacers of the mixer 22, collapses there with the formation of small drops and burns in the air stream.

Thus, the method and the device that implements it is applicable for organizing the burning of various types of liquid fuel in furnaces of various capacities, including domestic burners, through the use of stabilization of combustion on a system of crossed vortex cords and alternating swirling air jets. Moreover, the amount of fuel burned out in each volume of the combustion zone, the excess coefficient of the oxidizing agent and the level of turbulence are easily controlled by the corresponding number, range, angle of inclination of the vortex cords to the direction of flow of the combustion products and the ratio of the vortex and vortex air flows in the afterburning zone.

Compared with the prototype, the proposed method and device provide efficient and non-toxic combustion of a wide class of fuels.

List of Information

1. Sorozuk Ya.P. Combustion chambers of stationary gas turbine and steam installations. M., 1978, p. 112.

2. Copyright certificate of the USSR No. 626314, cl. F 23 K 1/00, BI No. 36, 1978 - prototype.

3. England patent No. 1312907, CL F 1 L; 1973 - prototype.

Claims (6)

1. A method of burning fuels, which consists in the fact that the fuel is mixed with primary air, an enriched combustible mixture is formed, it is burned to produce reducing products of combustion, which are burned into the secondary air jets swirled in opposite directions, inclined to the flow axis, forming swirling flows, characterized in that the jets of adjacent swirling flows are additionally twisted around the axis of the jets with the formation of rows of interconnected vortex cords, while the input of each periphery a pair of oppositely swirling air flows into the combustion zone is carried out downstream with respect to the central ones. 2. The method according to claim 1, characterized in that the alternating vortex cords formed in the combustion zone are twisted in opposite directions around their axes. 3. The method according to claim 1 or 2, characterized in that a portion of the swirling vortex cords is separated by inclined jets of air untwisted around their axes. 4. The method according to one of claims 1 to 3, characterized in that a gaseous fuel mixture is supplied to the mixing zone of the main fuel and air in the form of a system of crossed jets of combustible gas and air twisted around their axes. 5. A device for burning fuels, containing a fuel supply unit connected to a primary air mixer with fuel, which are installed in the combustion chamber with rows of slotted channels for supplying secondary air and corrugations made in it, characterized in that at least in the slotted channels are installed , two adjacent corrugated spacers with inclined corrugations, the direction of inclination of the corrugations of adjacent spacers is opposite and forms crossed channels. 6. The device according to claim 5, characterized in that the input side of the part of the pair of corrugated spacers is equipped with autonomous collectors isolated from the air cavity.

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