A flame-adjustable two-stage pre-chamber multi-fuel burner

Abstract

The present application relates to the technical field of industrial combustion equipment, and particularly relates to a two-stage precombustion chamber multi-fuel burner with adjustable flame, which comprises a burner body, and a center pipe, at least one fuel passage and at least one combustion air passage are coaxially arranged from inside to outside, and the outlet of each passage is connected to a first-stage precombustion chamber; the inner wall of the first-stage precombustion chamber is tangentially provided with a plurality of first-stage precombustion chamber cyclone inlets, which are used for forming tangential rotational flow on the periphery of the combustion gas flow advancing in the axial direction. By adjusting the momentum ratio of the tangential rotational flow and the axial straight flow, the present application realizes stepless switching between the short and stable combustion shape and the thin and long rigid shape, and adapts to different heating conditions. At the same time, based on the ignition mechanism of different forms of fuel, different flame stabilizing structures are adopted: a petal and tooth composite flame stabilizer is used for solid fuel, a special gas nozzle is used for gaseous fuel, and a fuel stabilizing disc is provided for liquid fuel, thereby solving the problem that a single burner is difficult to consider flame shape adjustment and multi-fuel adaptation.

Description

Technical Field

[0001] This invention relates to the field of industrial combustion equipment technology, specifically to a two-stage pre-combustion chamber multi-fuel burner with adjustable flame. Background Technology

[0002] The operational economy and environmental performance of industrial kilns and boiler heating equipment largely depend on the burner's flame stability, fuel adaptability, and nitrogen oxide control level. In recent years, energy price fluctuations have prompted end-users to demand the ability to flexibly switch between solid, gaseous, and liquid fuels, or even co-fire them, using the same burner. Environmental regulations have imposed stricter limits on NOx emissions, while different heating processes have significantly different requirements for flame morphology. These three combined demands place higher demands on the structural design of multi-fuel burners.

[0003] Regarding the structural design of multi-fuel burners, existing solutions generally adopt a single-stage pre-combustion chamber plus a subsequent combustion chamber arrangement. For example, patent document CN106895408A discloses a multi-fuel low-NOx burner consisting of a combined oil gun, a primary air duct, a secondary air duct, a tertiary air duct, a pre-combustion chamber shell, and a combustion chamber. The inner wall of the pre-combustion chamber has four tertiary air outlets along the tangential direction. The tertiary air is added at the end of the pre-combustion chamber and closely adheres to the inner wall of the combustion chamber, enveloping the flame. The flame shape is determined by the air volume distribution of different air ducts. Another example is the dual-fuel low-NOx burner for oil and gas disclosed in patent document CN109973999A, which uses a single-stage structure with a primary air duct, a secondary air duct, and a flared flame stabilizer. The secondary air inlet is arranged around the flared flame stabilizer. Yet another example is the pre-combustion swirl self-stabilizing combustion device disclosed in patent document CN117869880A, whose pre-combustion chamber consists of a first gradually expanding section, a middle gradually expanding section, and a tail gradually contracting section, also a single-stage pre-combustion chamber structure. The common feature of the above schemes is that although fuel ignition, initial combustion, and subsequent burnout are spatially distinct, the air distribution control of tangential swirl and axial direct current is completed in the same pre-combustion chamber or its adjacent outlet area, lacking independent spatial carriers to support them separately. This results in the flame pattern adjustment being indirectly achieved by changing the air volume of each duct through blade angles or baffle openings, with a limited adjustment range and delayed response. At the same time, tangential momentum and axial momentum are coupled and mixed in the same cavity, and their inverse relationship cannot be precisely decoupled, limiting the adjustable range and adjustment accuracy of the flame pattern.

[0004] Regarding fuel adaptability, existing solutions lack differentiated designs for flame stabilization structures for different fuel forms. Although CN106895408A achieves combustion of pulverized coal, oil, and gas in the same burner, its primary air duct end only has a generalized flame stabilizer (one or a combination of blunt body, multi-layer disc, or perforated plate types), without configuring optimal flame stabilization structures for the distinctly different ignition mechanisms of solid, gaseous, and liquid fuels. Solid fuels (such as pulverized coal) rely on a strong central recirculation zone to entrain high-temperature flue gas to heat the fuel and promote volatile matter release and ignition; gaseous fuels (such as natural gas) mainly rely on the local flow velocity and turbulence at the nozzle outlet to maintain flame root stability; liquid fuels (such as heavy oil) require organizing a high-temperature recirculation zone during the evaporation and ignition stages of atomized oil droplets to enhance oil-gas mixing with root air, compensate for ignition delay, and prevent oil droplets from pyrolyzing and coking under high temperature and oxygen deficiency—the requirements of these three are fundamentally different, and a generalized flame stabilization structure can only be a compromise, making it difficult to simultaneously ensure optimal combustion stability for all three fuels. Furthermore, the function of the oil gun in existing solutions is mostly limited to ignition conditions: the oil gun in CN117869880A is only used to ignite dense-phase pulverized coal and is taken out of operation after ignition; although the micro-oil ignition swirl pulverized coal combustion device disclosed in CN101403497B has primary, secondary, and tertiary combustion chambers, its main oil gun is also only used for micro-oil ignition and is not used as the main burner for liquid fuel in normal operation, which limits the burner's independent operation capability under pure oil conditions. Although CN106895408A discloses a combined oil gun that is used for both ignition and fuel oil as the main fuel, this solution does not have a dedicated fuel oil flame stabilizer for liquid fuels. Fuel atomization and stable combustion still rely on a general-purpose flame stabilizer, and there is still room for improvement in the stable combustion effect under pure oil conditions.

[0005] Regarding low-NOx combustion, while existing solutions generally incorporate the concept of staged air combustion, the delivery points of the staged air supply fail to effectively coordinate with the spatial separation of the two-stage pre-combustion chambers. CN106895408A divides the combustion air into primary, secondary, tertiary, and quaternary air, with the quaternary air added tangentially along the inner wall of the pre-combustion chamber and the tertiary air added at the end of the pre-combustion chamber. The delivery points of the staged air supply are still concentrated in the pre-combustion chamber section and its adjacent outlet, failing to utilize the physical separation of the two-stage chambers to separate the fuel-rich, oxygen-deficient combustion zone from the oxygen-rich burnout zone. CN109973999A adopts a staged method of primary air plus secondary air, with the secondary air directly added around the flare stabilizer, similarly completing all air distribution within a single-stage chamber. Although CN117869880A employs a two-stage arrangement of a dense-phase pulverized coal swirl burner and a dilute-phase pulverized coal staged combustion chamber, its staged combustion targets pulverized coal concentration rather than air staged combustion. The fuel gun is only used for ignition, and the pre-combustion chamber is a single-stage structure, failing to create a strictly fuel-rich, oxygen-deficient reducing atmosphere in the first-stage combustion zone. The common shortcomings of the above solutions are: because direct or secondary air is introduced in the pre-combustion chamber section, the atmosphere inside the pre-combustion chamber is not strictly fuel-rich and oxygen-deficient, and fuel-type NOx is not effectively suppressed in the initial stage of combustion; furthermore, the lack of an independent second-stage chamber to provide sufficient residence time and space in the subsequent burnout stage easily leads to problems with increased CO and unburned carbon. How to precisely coordinate the spatial separation and air distribution sequence of the two-stage pre-combustion chambers to strictly create a fuel-rich, oxygen-deficient reducing atmosphere in the first stage and achieve oxygen-rich burnout in the second stage is a problem that current technology has not yet adequately solved.

[0006] Regarding the coordinated combustion stabilization of multiple swirls, existing solutions lack clear design considerations regarding the swirl direction relationship of each swirl. CN106895408A includes a primary air swirl unit, a secondary air swirl unit, and a tangential secondary air outlet on the inner wall of the pre-combustion chamber, but does not explicitly specify the consistency requirement for the swirl direction of each swirl component; CN117869880A includes secondary air swirl blades, but similarly does not address the coordination of swirl direction with other swirl components. When the swirl directions are inconsistent, shear and momentum cancellation occur between adjacent swirls, weakening the entrainment strength of the central recirculation zone and reducing ignition stability. However, when the swirl directions of the pulverized coal supply air swirl, the combustion air swirl, the tangential air intake of the pre-combustion chamber, and the fuel oil flame stabilization disc swirl are consistent, a superimposed enhancement effect can be produced, significantly strengthening the central recirculation zone. Existing technologies have not recognized and utilized this swirl direction consistency principle to improve the combustion stabilization performance of multi-fuel burners.

[0007] In summary, existing multi-fuel swirl burners have shortcomings in terms of flame pattern adjustment, fuel adaptability, low-NOx combustion, and swirl-assisted stable combustion. Summary of the Invention

[0008] The purpose of this invention is to provide a two-stage pre-combustion chamber multi-fuel burner with adjustable flame to solve the aforementioned problems. By adjusting the momentum ratio of tangential swirling air to axial direct air, it achieves stepless switching between a short, stable flame shape and a long, rigid flame shape, adapting to different heating conditions. Simultaneously, based on the ignition mechanisms of different fuel forms, a differentiated flame stabilization structure is adopted: solid fuels use a petal-shaped and toothed composite flame stabilizer, gaseous fuels use a dedicated gas nozzle, and liquid fuels are equipped with an oil stabilization disc. This solves the problem that a single burner cannot simultaneously achieve flame shape adjustment and multi-fuel adaptation, as detailed below.

[0009] To achieve the above objectives, the present invention provides the following technical solution: This invention provides a flame-adjustable two-stage pre-combustion chamber multi-fuel burner, comprising: The burner body has a central tube, at least one fuel passage and at least one combustion air passage arranged coaxially from the inside to the outside, and the outlet of each passage is connected to the first-stage pre-combustion chamber. The first-stage pre-combustion chamber has several tangentially arranged cyclone inlets on its inner wall, which are used to form tangential swirls around the combustion airflow that is advancing along the axis. The secondary pre-combustion chamber is connected to the rear end of the primary pre-combustion chamber; The DC air orifice is arranged axially against the wall at the inlet end of the secondary pre-combustion chamber to introduce axial DC air into the secondary pre-combustion chamber; By adjusting the ratio of axial airflow and velocity in the DC air duct to tangential airflow and velocity in the cyclone inlet of the primary pre-combustion chamber, the flame can be made short and thick at low DC airflow to enhance stable combustion, and then become long and slender with rigidity at high DC airflow.

[0010] Under normal operating conditions, fuel and combustion air enter the primary pre-combustion chamber through various channels and are ignited. The tangentially arranged cyclone nozzles on the inner wall of the primary pre-combustion chamber form a tangential vortex around the combustion airflow, enhancing combustion stability in the central recirculation zone. Combustion products then enter the secondary pre-combustion chamber, where direct current air is added axially along the inner wall of the inlet end, enveloping the flame and influencing its length and rigidity. When enhanced combustion stability is required, the axial velocity of the direct current air is reduced, and the momentum of the tangential vortex dominates relative to the axial momentum, resulting in a short and thick flame. When a long and rigid flame is required, the axial velocity of the direct current air is increased, and the high axial momentum overcomes the centrifugal force of the tangential vortex, resulting in a long and rigid flame, with the tangential vortex degenerating into an outer mixing air curtain.

[0011] The operating steps are as follows: Fuel and combustion air are connected to the corresponding fuel channel and combustion air channel respectively. The outlet of each channel sends fuel and combustion air into the primary pre-combustion chamber. The fuel in the primary pre-combustion chamber is ignited by an ignition device. The tangentially arranged cyclone nozzles on the inner wall of the primary pre-combustion chamber form a tangential vortex around the combustion airflow, which entrains high-temperature flue gas to form a central recirculation zone and enhances ignition stability. Combustion products enter the secondary pre-combustion chamber from the primary pre-combustion chamber. Direct air is added axially along the inner wall of the inlet end of the secondary pre-combustion chamber through the direct air channel, mixes with the combustion products and continues to burn. Adjust the ratio of axial airflow and velocity in the DC air duct to tangential airflow and velocity in the cyclone inlet of the primary pre-combustion chamber according to the operating conditions: When enhanced combustion stability is required, reduce the axial airflow velocity of the DC air duct to 20m / s-30m / s, the tangential swirl dominates the flame shape, the flame is short and thick, and the axial length is twice the inner diameter of the secondary pre-combustion chamber; when a slender and rigid flame is required, increase the axial airflow velocity of the DC air duct to 140m / s-200m / s, the axial DC air dominates the flame shape, the flame becomes slender and rigid, the axial length can be stretched by 4-5 times, and the tangential swirl degenerates into an outer mixing air curtain.

[0012] Preferably, the central tube is equipped with a fuel gun assembly, which is used for both ignition and injection combustion of liquid fuel as the main fuel. This configuration allows the fuel gun assembly to perform both ignition and liquid fuel combustion functions, enabling the burner to operate independently without relying on other channels under pure oil conditions, thus expanding its fuel adaptability.

[0013] Preferably, the at least one fuel passage includes a coal-air passage and a gas passage, and the at least one combustion air passage includes a swirl air passage. The coal-air passage is used to deliver solid fuel, and its outlet end is equipped with a flame stabilizing structure that is a combination of a petal flame stabilizer and a toothed flame stabilizer. The gas passage is used to deliver gaseous fuel, and its outlet end is equipped with a gas nozzle as the flame stabilizing structure. The fuel gun assembly is used to inject liquid fuel, and its outlet end is equipped with a fuel oil flame stabilizing disc as the flame stabilizing structure. The flame stabilizing structures for the three types of fuels are different. This configuration allows for the configuration of optimal flame stabilizing structures for the distinct ignition and combustion stabilization mechanisms of solid, gaseous, and liquid fuels, solving the problem of poor combustion stabilization effect of a general-purpose flame stabilizing structure for specific fuels. The oil gun assembly can inject one or more mixtures of light oil, heavy oil, and residual oil liquid fuels; the coal air passage can be filled with one or more solid fuels such as pulverized coal, petroleum coke powder, biomass powder, and coal slime powder in any proportion; the gas passage can be filled with one or more mixtures of natural gas and coal gas gas fuels; the solid fuels, gaseous fuels, and liquid fuels can be burned individually or in any combination, achieving full fuel adaptability without replacing any parts.

[0014] Preferably, the coal air duct is equipped with coal air swirl blades, and the swirl air duct is equipped with swirl air blades; the swirl blades, swirl air blades, cyclone inlets in the primary pre-combustion chamber, and fuel oil flame stabilizer are all aligned in the same direction, causing the various swirls to superimpose and enhance each other in the primary pre-combustion chamber. With this configuration, the swirls are aligned in direction and superimpose and enhance each other rather than cancel each other out in the primary pre-combustion chamber, resulting in a stronger entrainment effect in the central recirculation zone and a significant improvement in ignition stability.

[0015] Preferably, the primary pre-combustion chamber is enclosed by an outer cylinder of the primary pre-combustion chamber, and the secondary pre-combustion chamber is enclosed by an outer cylinder of the secondary pre-combustion chamber. There is a radius difference between the outer cylinders of the primary and secondary pre-combustion chambers, the value of which is 0.15-0.20 times the inner diameter of the secondary pre-combustion chamber. This configuration, with the radius difference between the two pre-combustion chambers complementing the tangential swirl of the primary pre-combustion chamber, allows the central recirculation zone to be independently distributed at low DC wind speeds and to develop continuously at high DC wind speeds, further optimizing the flame morphology adjustment effect.

[0016] Preferably, the DC air duct orifice is a circular tube with an aspect ratio greater than 3. A DC air orifice is provided on the inner wall of the cylinder at the inlet end of the secondary pre-combustion chamber. The axially introduced DC air can envelop the flame and affect its length and rigidity. It also includes a DC air regulating ring, which can be moved axially to change the inner diameter of the DC air orifice, thereby adjusting the DC air velocity. This configuration ensures the axiality and uniformity of the outflow by using a large aspect ratio circular tube in the DC air duct. The DC air regulating ring changes the outlet cross-sectional area by axial movement, achieving continuous adjustment of the DC air velocity, making operation simple and reliable.

[0017] Preferably, when the axial wind speed of the DC airflow switches from 20m / s-30m / s to 140m / s-200m / s, the radial expansion range of the rotating jet generated by the tangential air intake in the primary pre-combustion chamber shrinks from nearly the inner diameter of the secondary pre-combustion chamber to 50%-60% of its inner diameter; correspondingly, the axial length of the flame at the burner outlet can be extended by 4-5 times. This configuration, through a clear correspondence between wind speed parameters and flame morphology, provides a quantitative basis for flame adjustment during actual operation.

[0018] Preferably, the outlet end of the coal air duct is equipped with a petal-shaped flame stabilizer. This structure can shorten the axial length of the central recirculation zone in the primary pre-combustion chamber to 0.3-0.6 times the inner diameter of the primary pre-combustion chamber, thus allowing the axial length of the primary pre-combustion chamber to be 0.4-0.6 times its inner diameter. This configuration effectively shortens the axial length of the central recirculation zone, making the primary pre-combustion chamber structure more compact and saving space. When burning anthracite or lean coal, the expansion cone half-angle of the petal-shaped flame stabilizer is 40°-55°; when burning bituminous coal, the expansion cone half-angle is 10°-25°. The expansion cone half-angle is defined as the angle between the generatrix of the expansion cone and the axis of the expansion cone. This configuration allows for adjustment of the expansion cone half-angle according to the ignition characteristics of different coal types. A larger expansion cone half-angle is used for difficult-to-burn coals to enhance recirculation and stabilize combustion, while a smaller expansion cone half-angle is used for easily flammable coals to prevent excessive flame dispersion, ensuring good combustion stabilization for all coal types.

[0019] Preferably, the direct-flow air duct has no air supply opening in the primary pre-combustion chamber and only intervenes axially in the secondary pre-combustion chamber, creating a fuel-rich, oxygen-deficient reducing atmosphere in the primary pre-combustion chamber. The ratio of the total combustion air entering the primary pre-combustion chamber to the air required for fuel combustion is ≤0.75. The fuel undergoes its first fuel-rich combustion in the primary pre-combustion chamber, and unburned fuel is mixed with the axially intervened direct-flow air in the secondary pre-combustion chamber for a second oxygen-rich combustion until complete combustion. With this configuration, through staged combustion, the fuel undergoes thermal decomposition and releases volatiles and partial combustion in the fuel-rich, oxygen-deficient reducing atmosphere of the primary pre-combustion chamber, and nitrogen compounds are reduced in the reducing atmosphere, effectively suppressing the formation of fuel-type NOx. The remaining unburned fuel is mixed with the direct-flow air in the secondary pre-combustion chamber for complete combustion, minimizing the formation of thermal NOx and resulting in a significant low-NOx combustion effect. Furthermore, the ratio of the total combustion air entering the primary pre-combustion chamber to the air required for pulverized coal combustion is 0.4-0.75; the air supplied by the axially introduced direct-flow air at the inlet of the secondary pre-combustion chamber ensures an overall air excess coefficient of 1.2-1.35, and the axial length of the secondary pre-combustion chamber is 0.5-0.6 times its inner diameter. This configuration ensures complete fuel combustion while maintaining a low-NOx effect. The compact length-to-diameter design of the secondary pre-combustion chamber further saves overall layout space.

[0020] The beneficial effects are: 1. This invention forms a tangential swirling flow by tangentially arranging cyclone nozzles on the inner wall of the primary pre-combustion chamber, and combines this with the direct current air added axially against the wall at the inlet end of the secondary pre-combustion chamber. By adjusting the air volume and air velocity ratio of the two, the flame can be steplessly switched from a short, coarse, stable burning shape to a long, slender, rigid shape. This changes the traditional method of relying on blade angles or baffles to mechanically adjust the flame, resulting in a wider adjustment range, faster response, and the ability to adapt to the flame shape requirements of different heating conditions.

[0021] 2. This invention provides differentiated flame stabilization structures for solid, gaseous, and liquid fuels: solid fuels use a combination of petal-shaped and toothed flame stabilizers, gaseous fuels use gas nozzles, and liquid fuels use fuel oil flame stabilizing discs. The three flame stabilization structures are different from each other, adapting to the drastically different ignition and combustion stabilization mechanisms of different fuel forms, solving the problem of poor combustion stabilization effect of generalized flame stabilization structures for specific fuels, and demonstrating strong adaptability to all fuels.

[0022] 3. The swirling blades of the coal-air swirl, the swirling air blades, the swirling air inlet of the primary pre-combustion chamber and the flame stabilizing disc of the fuel oil are all swirling in the same direction, so that each swirling stream is superimposed and enhanced in the primary pre-combustion chamber, the entrainment effect in the central recirculation zone is stronger, the ignition stability is greatly improved, and the problem of mutual weakening when the directions of each swirling stream are inconsistent is avoided.

[0023] 4. The present invention adopts a two-stage pre-combustion chamber structure. There is a radius difference between the outer cylinder of the first-stage pre-combustion chamber and the outer cylinder of the second-stage pre-combustion chamber. This radius difference is combined with the tangential swirl of the first-stage pre-combustion chamber, so that the central recirculation zone is independently distributed under low DC wind speed and develops through the flow under high DC wind speed, which optimizes the flame shape adjustment effect. At the same time, the two-stage pre-combustion chamber structure makes the combustion organization more reasonable.

[0024] 5. The DC air duct of the present invention has no air supply opening in the primary pre-combustion chamber and only intervenes axially in the secondary pre-combustion chamber, so that a fuel-rich and oxygen-deficient reducing atmosphere is formed in the primary pre-combustion chamber. The fuel is pyrolyzed and partially burned in the reducing atmosphere, and nitrogen-containing compounds are reduced, inhibiting the formation of fuel-type NOx. Unburned fuel is mixed with DC air in the secondary pre-combustion chamber and burned completely, avoiding the formation of thermal NOx, and the low-NOx combustion effect is better.

[0025] 6. The oil gun assembly of the present invention is used for both ignition and injection combustion with liquid fuel as the main fuel. When liquid fuel is not used, it can also serve as a central air duct. It has multiple uses, expands fuel adaptability, and improves duct utilization. Under pure oil conditions, it can operate independently without relying on other ducts. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 This is a front view internal cross-sectional structural diagram of the present invention; Figure 2 This is a right-side structural diagram of the present invention; Figure 3 This is a three-dimensional structural schematic diagram of the DC air regulating ring of the present invention; Figure 4 This is a three-dimensional structural schematic diagram of the petal flame stabilizer of the present invention; Figure 5 This is a three-dimensional structural schematic diagram of the toothed flame stabilizer of the present invention.

[0028] Figure 6 This is a three-dimensional structural schematic diagram of the fuel flame stabilizer disc of the present invention.

[0029] The annotations in the attached figures are explained as follows: 1. Oil gun assembly; 2. Central tube; 3. Coal-air swirl vane; 4. Coal-air outer cylinder; 5. Swirl vane; 6. Swirl outer cylinder; 7. Gas outer cylinder; 8. Gas inner cone; 9. Gas outer cone; 10. Direct current air regulating ring; 11. Primary pre-combustion chamber outer cylinder; 12. Direct current air orifice; 13. Secondary pre-combustion chamber outer cylinder; 14. Gas nozzle; 15. Swirl air diffuser cone; 16. Toothed flame stabilizer; 17. Petal flame stabilizer; 18. Fuel oil flame stabilizer disc; 19. Primary pre-combustion chamber cyclone inlet; 20. Secondary pre-combustion chamber; 21. Primary pre-combustion chamber; 22. Direct current air passage; 23. Gas passage; 24. Swirl air passage; 25. Coal-air passage; 26. Central air passage. Detailed Implementation

[0030] The technical solutions of the embodiments of this application will be clearly described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application are within the scope of protection of this application.

[0031] It should be noted that all directional and positional terms used in this invention, such as "up," "down," "left," "right," "front," "back," "vertical," "horizontal," "inner," "outer," "top," "lower," "lateral," "longitudinal," and "center," are used only to explain the relative positional relationships and connections between components in a specific state (as shown in the accompanying drawings). They are merely for the convenience of describing the invention and do not require the invention to be constructed and operated in a specific orientation; therefore, they should not be construed as limitations on the invention. Furthermore, the use of "first" and "second" in this invention is for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated.

[0032] In the description of this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0033] In the description of this specification, the references to "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples" refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0034] See Figures 1-6 As shown, the present invention provides a flame-adjustable two-stage pre-combustion chamber multi-fuel burner, comprising: The burner body has a central tube 2, at least one fuel passage, and at least one combustion air passage arranged coaxially from the inside to the outside. The outlet of each passage is connected to the primary pre-combustion chamber 21. A fuel gun assembly 1 is installed inside the central tube 2. The fuel gun assembly 1 can be used for ignition or for injection combustion with liquid fuel as the main fuel. When liquid fuel is not used, the space between the fuel gun assembly 1 and the central tube 2 forms a central air passage 26, through which central air can be introduced to assist combustion.

[0035] As an optional implementation, the at least one fuel passage includes a coal air passage 25 and a gas passage 23, and the at least one combustion air passage includes a swirl air passage 24. The coaxially arranged structure from the inside out is as follows: oil gun assembly 1, central pipe 2, coal air outer cylinder 4 of coal air passage 25, swirl air outer cylinder 6 of swirl air passage 24, gas inner cone 8 and gas outer cone 9 and gas outer cylinder 7 of gas passage 23, and direct current air passage 22. Coal air passage 25 is equipped with coal air swirl blades 3, swirl air passage 24 is equipped with swirl air blades 5, and direct current air passage 22 is equipped with a direct current air regulating ring 10. The outlets of each passage are located on the same plane and connected to the inlet end of the primary pre-combustion chamber 21.

[0036] The outer wall of the central pipe 2, the inner wall of the coal air outer cylinder 4, the coal air swirl blades 3, the outer wall of the petal flame stabilizer 17, the inner wall of the swirl air diffuser 15, and the toothed flame stabilizer 16 constitute the coal air passage 25, through which solid fuel enters and, after being ignited, forms a stable flame between the petal flame stabilizer 17 and the toothed flame stabilizer 16; the outer wall of the coal air outer cylinder 4, the inner wall of the swirl air outer cylinder 6, the swirl air blades 5, the inner wall of the gas inner cone 8, and the swirl air diffuser 15 constitute the swirl air passage 24, through which clean air passes. After entering the channel, the gas becomes a rotating and expanding airflow, which enters the primary pre-combustion chamber 21 to aid combustion. The outer wall of the swirl air outer cylinder 6, the inner wall of the gas outer cylinder 7, the outer wall of the gas inner cone 8, the inner wall of the gas outer cone 9, and the gas nozzle 14 constitute the gas channel 23, through which the gaseous fuel enters and forms a stable flame at the end of the gas nozzle 14 after being ignited. The outer wall of the gas outer cylinder 7, the outer wall of the gas outer cone 9, the outer wall of the primary pre-combustion chamber 11, the direct current air regulating ring 10, and the direct current air round hole 12 constitute the direct current air channel 22.

[0037] The primary pre-combustion chamber 21 is enclosed by the outer cylinder 11 of the primary pre-combustion chamber, and its inner wall is tangentially arranged with a number of primary pre-combustion chamber cyclone inlets 19, which are used to form tangential swirls around the combustion airflow that moves along the axial direction. In this embodiment, there are two primary pre-combustion chamber cyclone inlets 19, which are symmetrically arranged along the circumferential direction of the inner wall of the primary pre-combustion chamber 21.

[0038] The inlet end of the primary pre-combustion chamber 21 is equipped with a flame stabilizing assembly structure: a swirling air diffuser cone 15, a toothed flame stabilizer 16, a petal-shaped flame stabilizer 17, and a fuel oil flame stabilizing disc 18. Specifically: the coal air passage 25 is used to introduce solid fuel, and its outlet end is equipped with a combination of the petal-shaped flame stabilizer 17 and the toothed flame stabilizer 16; the gas passage 23 is used to introduce gaseous fuel, and its outlet end is equipped with a gas nozzle 14 (a multi-hole flame stabilizer); the oil gun assembly 1 is used to inject liquid fuel, and its outlet end is equipped with a fuel oil flame stabilizing disc 18. The flame stabilizing structures for the three fuels are different, adapting to the distinct ignition and combustion stabilization mechanisms of solid, gaseous, and liquid fuels.

[0039] The coal swirl blade 3 generates a coal powder swirl, the swirl air blade 5 generates a swirl air, and the swirl inlet 19 of the primary pre-combustion chamber generates a primary pre-combustion chamber swirl, which is consistent with the swirl direction of the fuel oil flame stabilizer 18. This causes the swirls to superimpose and enhance each other in the primary pre-combustion chamber 21, resulting in a strong entrainment effect in the central recirculation zone and a significant improvement in ignition stability.

[0040] The secondary pre-combustion chamber 20, enclosed by the outer cylinder 13 of the secondary pre-combustion chamber, is connected to the rear end of the primary pre-combustion chamber 21. There is a radius difference between the outer cylinder 11 of the primary pre-combustion chamber and the outer cylinder 13 of the secondary pre-combustion chamber, the value of which is 0.15-0.20 times the inner diameter of the secondary pre-combustion chamber 20. In this embodiment, the radius difference is 115 mm, the inner diameter of the secondary pre-combustion chamber is 620 mm, and the ratio is 0.185. The radius difference between the two pre-combustion chambers, in conjunction with the tangential swirl of the primary pre-combustion chamber, allows the central recirculation zone to be independently distributed under low DC wind speeds and to develop continuously under high DC wind speeds.

[0041] A direct-flow air orifice 12 is arranged axially against the wall at the inlet end of the secondary pre-combustion chamber 20 to introduce axial direct-flow air into the secondary pre-combustion chamber 20. The direct-flow air orifice 22 is a circular tube with a length-to-diameter ratio greater than 3. The direct-flow air orifice 12 is formed against the wall of the cylinder at the inlet end of the secondary pre-combustion chamber 20. The axially introduced direct-flow air can envelop the flame and affect its length and rigidity. The direct-flow air regulating ring 10 can change the inner diameter of the direct-flow air orifice 12 by axial movement, thereby regulating the wind speed of the direct-flow air. The direct-flow air channel 22 has no air supply opening at the primary pre-combustion chamber 21, but only intervenes axially at the secondary pre-combustion chamber 20, creating a fuel-rich and oxygen-deficient reducing atmosphere in the primary pre-combustion chamber 21.

[0042] Using the above structure, the operating steps are as follows: Fuel and combustion air are respectively connected to corresponding channels: when burning solid fuels, a mixture of pulverized coal, petroleum coke powder, biomass powder, and coal slime powder solid fuels with primary air is sent in through the coal air channel 25; when burning gaseous fuels, natural gas and coal gas gaseous fuels are sent in through the gas channel 23; when burning liquid fuels, light oil, heavy oil, and residual oil liquid fuels are injected through the oil gun assembly 1; swirling air is sent in through the swirling air channel 24 to aid combustion. The three types of fuels can be burned individually or in any combination, achieving full fuel adaptability without changing any parts.

[0043] The fuel in the primary pre-combustion chamber 21 is ignited using the oil gun assembly 1. The tangentially arranged cyclone inlets 19 on the inner wall of the primary pre-combustion chamber 21 create a tangential vortex around the combustion airflow, entraining high-temperature flue gas to form a central recirculation zone, thus enhancing ignition stability. The coal-air swirl blades 3, swirl fan blades 5, primary pre-combustion chamber cyclone inlets 19, and fuel oil flame stabilizer 18 all rotate in the same direction, and the various swirls superimpose and enhance each other within the primary pre-combustion chamber 21.

[0044] Combustion products enter the secondary pre-combustion chamber 20 from the primary pre-combustion chamber 21. Direct air is introduced axially through the direct air channel 22 along the direct air circular hole 12 on the inner wall of the inlet end of the secondary pre-combustion chamber 20, mixing with the combustion products and continuing combustion. Since the direct air channel 22 has no air supply opening at the primary pre-combustion chamber 21, the ratio of the total amount of combustion air entering the primary pre-combustion chamber 21 to the amount of air required for fuel combustion is ≤0.75. The fuel undergoes its first rich-fuel combustion in the primary pre-combustion chamber 21, where nitrogen compounds are reduced in a reducing atmosphere, effectively suppressing the formation of fuel-type NOx. Unburned fuel mixes with the axially introduced direct air in the secondary pre-combustion chamber 20 for a second oxygen-rich combustion, achieving an overall excess air coefficient of 1.2-1.35, ensuring complete fuel combustion while preventing the formation of thermal NOx.

[0045] Adjusting the axial position of the DC air regulating ring 10 according to the operating conditions changes the inner diameter of the DC air circular hole 12, thereby adjusting the axial air volume and velocity of the DC air, forming different matching ratios with the tangential air volume and velocity of the cyclone inlet 19 of the primary pre-combustion chamber: When enhanced combustion stability is required, the axial velocity of the DC air is reduced to 20m / s-30m / s, the momentum of the tangential swirl is dominant relative to the axial momentum, the tangential swirl envelope diameter is close to the inner diameter of the secondary pre-combustion chamber 20, and the flame unfolds in a short, bowl-shaped pattern attached to the wall, with a length of twice the cylinder diameter, thus enhancing combustion stability; When a slender and rigid flame is required, the axial velocity of the DC air is increased to 140m / s-200m / s, the high axial momentum overcomes the centrifugal force of the tangential swirl, the radial expansion range of the rotating jet shrinks to 50%-60% of the inner diameter of the secondary pre-combustion chamber, the flame remains slender and rigid, the tangential swirl degenerates into an outer air curtain, and the flame length can be extended by 4-5 times. By adjusting the airflow ratio between the direct current air and the swirl air in the primary pre-combustion chamber, the flame can be seamlessly switched from a short and thick shape to a rigid and long flame.

[0046] As an optional implementation, a petal-shaped flame stabilizer 17 is provided at the outlet end of the coal air duct 25. This structure can shorten the axial length of the central recirculation zone in the primary pre-combustion chamber 21 to 0.3-0.6 times the inner diameter of the primary pre-combustion chamber, thereby allowing the axial length of the primary pre-combustion chamber 21 to be 0.4-0.6 times the inner diameter of the primary pre-combustion chamber, resulting in a more compact structure. When burning anthracite or lean, difficult-to-burn coal, the expansion cone half-angle of the petal-shaped flame stabilizer 17 is 40°-55°, with a large expansion cone half-angle enhancing recirculation and stabilizing combustion; when burning bituminous, easily combustible coal, the expansion cone half-angle of the petal-shaped flame stabilizer 17 is 10°-25°, with a small expansion cone half-angle preventing excessive flame dispersion. The expansion cone half-angle is defined as the angle between the generatrix of the expansion cone and the axis of the expansion cone.

[0047] A tangential swirling flow is formed by the cyclone inlets 19 tangentially arranged on the inner wall of the primary pre-combustion chamber 21. This, combined with the direct current airflow axially fed into the inlet of the secondary pre-combustion chamber 20, allows for stepless switching of the flame from a short, coarse, stable combustion shape to a long, rigid shape by adjusting the airflow ratio between the two. This provides a wide adjustment range, rapid response, and adaptability to different heating conditions. The two-stage pre-combustion chamber structure, combined with staged air combustion, results in significant low-NOx performance, strong adaptability to all fuels, and reliable stable combustion, demonstrating promising prospects for industrial applications.

[0048] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A two-stage pre-combustion chamber multi-fuel burner with adjustable flame, characterized in that, include: The burner body has a central tube (2), at least one fuel passage and at least one combustion air passage arranged coaxially from the inside to the outside, and the outlet of each passage is connected to the first-stage pre-combustion chamber (21). The first-stage pre-combustion chamber (21) has several first-stage pre-combustion chamber cyclone inlets (19) arranged tangentially on its inner wall to form tangential swirl around the combustion airflow that moves along the axial direction; The secondary pre-combustion chamber (20) is connected to the rear end of the primary pre-combustion chamber (21); A direct-flow air hole (12) is arranged along the axial wall at the inlet end of the secondary pre-combustion chamber (20) to add wall-mounted axial direct-flow air to the secondary pre-combustion chamber (20); By adjusting the ratio of the axial air volume and velocity of the DC air channel (22) to the tangential air volume and velocity of the cyclone inlet (19) of the first-stage pre-combustion chamber, the flame can be made short and thick at low DC air velocity to enhance stable combustion, and become long and thin with rigidity at high DC air velocity.

2. The flame-adjustable two-stage pre-combustion chamber multi-fuel burner according to claim 1, characterized in that: The central tube (2) is equipped with an oil gun assembly (1), which is used for both ignition and injection combustion with liquid fuel as the main fuel.

3. The flame-adjustable two-stage pre-combustion chamber multi-fuel burner according to claim 2, characterized in that: The at least one fuel passage includes a coal air passage (25) and a gas passage (23), and the at least one combustion air passage includes a swirl air passage (24). The coal air passage (25) is used to feed solid fuel, and the flame stabilizing structure at its outlet end is a combination of a petal flame stabilizer (17) and a toothed flame stabilizer (16); the gas passage (23) is used to feed gaseous fuel, and the flame stabilizing structure at its outlet end is a gas nozzle (14); the oil gun assembly (1) is used to inject liquid fuel, and the flame stabilizing structure at its outlet end is a fuel oil flame stabilizing disc (18). The oil gun assembly (1) can spray one or more mixtures of light oil, heavy oil, and residual oil liquid fuels; the coal air passage (25) can be filled with one or more solid fuels such as pulverized coal, petroleum coke powder, biomass powder, and coal slime powder in any proportion; the gas passage (23) can be filled with one or more mixtures of natural gas and coal gas gas fuels; the solid fuels, gaseous fuels, and liquid fuels can be burned individually or in any combination.

4. The flame-adjustable two-stage pre-combustion chamber multi-fuel burner according to claim 3, characterized in that: The coal air passage (25) is provided with a coal air swirl blade (3), and the swirl air passage (24) is provided with a swirl air blade (5). The swirl blade (3), the swirl air blade (5), the swirl inlet (19) of the first-stage pre-combustion chamber and the fuel oil flame stabilizer (18) are all in the same direction, so that each swirl is superimposed and enhanced in the first-stage pre-combustion chamber (21).

5. The flame-adjustable two-stage pre-combustion chamber multi-fuel burner according to claim 1, characterized in that: The primary pre-combustion chamber (21) is surrounded by the outer cylinder (11) of the primary pre-combustion chamber, and the secondary pre-combustion chamber (20) is surrounded by the outer cylinder (13) of the secondary pre-combustion chamber. There is a radius difference between the outer cylinder (11) of the primary pre-combustion chamber and the outer cylinder (13) of the secondary pre-combustion chamber, and the value of the radius difference is 0.15-0.20 times the inner diameter of the secondary pre-combustion chamber (20).

6. The flame-adjustable two-stage pre-combustion chamber multi-fuel burner according to claim 1, characterized in that: The DC air hole (12) is a round tube with a length-to-diameter ratio greater than 3. The DC air hole (12) is provided on the inner wall of the cylinder at the inlet end of the secondary pre-combustion chamber (20). The DC air added along the axial direction can wrap around the flame and affect the length and rigidity of the flame. It also includes a DC air regulating ring (10), which can change the inner diameter of the DC air circular hole (12) by axial movement, thereby regulating the wind speed of the DC air.

7. The flame-adjustable two-stage pre-combustion chamber multi-fuel burner according to claim 1, characterized in that: When the axial wind speed of the DC air is switched from 20m / s-30m / s to 140m / s-200m / s, the radial expansion range of the rotating jet generated by the tangential air intake in the primary pre-combustion chamber (21) shrinks from close to the inner diameter of the secondary pre-combustion chamber (20) to 50%-60% of its inner diameter; correspondingly, the axial length of the flame at the burner outlet can be lengthened by 4-5 times.

8. The flame-adjustable two-stage pre-combustion chamber multi-fuel burner according to claim 3, characterized in that: The outlet end of the coal air duct (25) is provided with a petal flame stabilizer (17). This structure can shorten the axial length of the central recirculation zone in the primary pre-combustion chamber (21) to 0.3-0.6 times the inner diameter of the primary pre-combustion chamber, so that the axial length of the primary pre-combustion chamber (21) can be taken as 0.4-0.6 times the inner diameter of the primary pre-combustion chamber. When burning anthracite or lean coal, the expansion cone half-angle of the petal flame stabilizer (17) is 40°-55°; when burning bituminous coal, the expansion cone half-angle of the petal flame stabilizer (17) is 10°-25°; the expansion cone half-angle is defined as the angle between the expansion cone generatrix and the expansion cone axis.

9. The flame-adjustable two-stage pre-combustion chamber multi-fuel burner according to claim 1, characterized in that: The direct current air duct (22) has no air supply opening at the primary pre-combustion chamber (21) and only intervenes axially at the entrance of the secondary pre-combustion chamber (20), so that a fuel-rich and oxygen-deficient reducing atmosphere is formed in the primary pre-combustion chamber (21); the ratio of the total amount of combustion air entering the primary pre-combustion chamber (21) to the amount of air required for fuel combustion is ≤0.75; the fuel undergoes the first fuel-rich combustion in the primary pre-combustion chamber (21), and the unburned fuel is mixed with the axially intervened direct current air in the secondary pre-combustion chamber (20) for the second oxygen-rich combustion until it is burned out.

10. The flame-adjustable two-stage pre-combustion chamber multi-fuel burner according to claim 9, characterized in that: The ratio of the total amount of combustion air entering the primary pre-combustion chamber (21) to the amount of air required for pulverized coal combustion is 0.4-0.75; the air provided by the axially introduced direct current air at the entrance of the secondary pre-combustion chamber (20) makes the overall air excess coefficient reach 1.2-1.35, and the axial length of the secondary pre-combustion chamber (20) is 0.5-0.6 times the inner diameter of the secondary pre-combustion chamber.

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