Adjustable flue gas internal circulation rotational flow enhanced mixing low-nitrogen burner

Abstract

The invention discloses an adjustable flue gas internal circulation rotational flow enhanced mixing low-nitrogen burner which comprises a gas pipe, an air pipe, a flue gas pipe and a swirler. The air pipe sleeves the outer side of the gas pipe; the flue gas pipe is axially arranged on the rear side of the air outlet of the air pipe; a swirler is arranged between the gas pipe and the flue gas pipe; the swirler comprises a swirler hub and a plurality of swirler blades evenly distributed in the circumferential direction. The swirler blades are rotatably connected to the swirler hub through the blade rotating shafts, so that the installation angles of the swirler blades can be adjusted, the swirler blades are fixed through the locking parts after being adjusted, and air guide fillets are arranged on the edges of the bottoms of the swirler blades. Different mixing requirements are actively met through macroscopic angle adjustment, the fluid efficiency at each angle is improved through microcosmic flow guide optimization, double-effect cooperation is achieved, the mixing uniformity and stability of flue gas and combustion-supporting air are remarkably improved, and therefore more efficient and more thorough low-nitrogen combustion is achieved within the wide load range, and the combustion efficiency is improved. The emission of nitrogen oxides is effectively reduced.

Description

Technical Field

[0001] This invention relates to the field of gas combustion equipment technology, and specifically to a low-NOx burner for flue gas internal circulation that actively enhances the mixing effect by optimizing the structure of the cyclone itself. Background Technology

[0002] Flue gas recirculation swirl combustion technology reduces the oxygen concentration of the combustion air and lowers the peak combustion temperature by entraining the flue gas after combustion. It is one of the core pathways to achieve low nitrogen emissions, and its mixing efficiency and swirl field stability directly determine the combustion performance and pollutant control effect. As a core component, the swirl generator plays a crucial role in constructing the swirl field and promoting thorough mixing of flue gas, air, and fuel gas. Its structural design has a decisive impact on the overall performance of the burner.

[0003] Existing flue gas internal circulation swirl burners mostly use fixed-angle blade structures, resulting in a fixed swirl intensity after assembly. This makes them unsuitable for the complex operating conditions of industrial production, such as fuel type switching (e.g., natural gas, liquefied petroleum gas, manufactured gas) and load fluctuations (30%-110% of rated load). At low loads, the fixed strong swirl can easily lead to flame flare-off; at high loads, insufficient swirl intensity causes uneven mixing, resulting in localized oxygen-rich, high-temperature zones, and NO₂ production. x Emissions are difficult to consistently meet standards. At the same time, the existing blades mostly have right-angled edges, which easily generate local vortices and flow separation when the airflow passes through them. This not only increases flow resistance and causes energy loss, but also disrupts the uniformity of the swirling flow field and weakens the mixing enhancement effect, failing to meet the dual requirements of high efficiency and low nitrogen.

[0004] Chinese invention patent CN113531530A discloses a flue gas internal circulation burner. This burner uses an air guide tube to form a Venturi tube structure, enhancing the internal flue gas circulation effect and promoting the mixing of fuel gas, combustion air, and flue gas, eliminating the need for an external flue gas circulation pipe. However, in actual combustion, the fuel gas easily comes into contact with unevenly mixed combustion air, affecting the low-NOx combustion effect. In existing technologies, there is no structure to enhance the mixing of flue gas and combustion air, which easily leads to uneven mixing and an insignificant low-NOx combustion effect.

[0005] Chinese invention patent CN115076685A discloses a flue gas internal circulation swirl low-NOx burner. By installing a swirl converter between the flue gas pipe and the combustion air pipe, it enhances the mixing uniformity of the entrained flue gas and combustion air, reducing oxygen concentration and preventing the mixing of combustion air with locally high oxygen concentrations, thus better promoting NOx reduction. However, the swirl converter used to promote flue gas-air mixing is a fixed welded structure with non-variable blade angles. This means the burner can only achieve optimal mixing near its design operating conditions. When the load and fuel characteristics change, the mixing effect decreases, affecting the stability of low-NOx emissions. Furthermore, the traditional right-angled blade edges easily cause airflow separation and additional drag, which is detrimental to efficient mixing.

[0006] Therefore, there is an urgent need for a hydrocyclone structure that is simple in structure, requires no complex external control, but has adaptability to operating conditions and higher mixing efficiency. Summary of the Invention

[0007] The purpose of this invention is to provide an adjustable flue gas internal circulation swirl enhanced mixing low-NOx burner, whose swirl vanes have adjustable angle and combined with edge guide optimization, to achieve a significant improvement in mixing effect and a fundamental improvement in operating condition adaptability through structural innovation of a single component.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] An adjustable flue gas internal circulation swirl-enhanced mixing low-NOx burner includes a gas pipe, an air pipe, a flue gas pipe, a blunt body, and a swirler. The air pipe is sleeved on the outside of the gas pipe. The flue gas pipe is axially arranged behind the air outlet of the air pipe. A swirler is provided between the gas pipe and the flue gas pipe. The swirler includes a swirler hub and multiple swirler blades evenly distributed circumferentially along the swirler hub. The swirler blades are rotatably connected to the swirler hub via blade shafts, allowing their installation angle to be adjusted and fixed by locking components after adjustment. The bottom edge of the swirler blades is provided with a guide radius.

[0010] Furthermore, the cyclone separator is disposed inside the flue gas pipe and fixed to the outside of the gas pipe.

[0011] Furthermore, the radius of the air guide rounded corner is 0.5mm~2mm.

[0012] Furthermore, the angle of the hydrocyclone blades is adjustable from 5° to 60°.

[0013] Furthermore, the air pipe is a tapered nozzle structure, and the base circle unfolding angle of the outer contour of the tapered section is 45°~90°.

[0014] Furthermore, the flue pipe is fixedly connected to the air pipe by a plurality of ribs evenly distributed along the circumference.

[0015] Furthermore, the flue pipe is coaxially arranged with the air pipe and the gas pipe.

[0016] Furthermore, a blunt body is provided at the outlet of the gas pipe.

[0017] Furthermore, the blunt body is threadedly connected to the gas pipe, and a narrow slit is formed between them for the gas to flow out.

[0018] A method for adjusting and using the aforementioned adjustable flue gas internal circulation swirl enhanced mixing low-NOx burner involves manually rotating each swirler blade to a predetermined angle during burner installation or maintenance, based on the boiler's main operating load. Then, tools are used to tighten the locking components of each blade, fixing all swirler blades at that angle. During operation, high-speed air entrains the flue gas into the flue gas pipe. The mixed airflow flows through the swirler blades with optimized and fixed angles. The guide radius at the blade edges ensures smooth airflow, achieving efficient and uniform mixing, ultimately mixing with the fuel gas to achieve low-NOx combustion.

[0019] Compared with the prior art, the beneficial effects of this invention are mainly reflected in the dual structural innovation of the hydrocyclone itself: 1. Built-in adaptability to different operating conditions: The adjustable blade angle design makes the hydrocyclone itself an "intelligent" component that can adapt to different operating conditions. Users or installers can pre-adjust and fix the blades to the optimal angle according to the boiler's common load range, so that the burner is always in the optimal mixing state under the target operating conditions. This fundamentally solves the problem of poor adaptability of fixed hydrocyclones and requires no external power or complex control.

[0020] 2. Fundamental Improvement in Fluid Efficiency: The rounded corner structure of the air guide is a fundamental optimization of the blade geometry. By changing the curvature of the edges, it guides the airflow through a smooth transition, effectively reducing flow separation and vortex generation. This improvement results in lower fluid resistance, higher energy transfer efficiency, and more uniform and gentler mixing at any set angle, which is conducive to the formation of a stable diffuse flame.

[0021] 3. Synergistic Enhancement Effect: "Adjustable angle" allows for macroscopic matching of mixing intensity requirements, while "guide radius" microscopically optimizes flow characteristics at each selected angle. These two elements are integrated into the cyclone separator blades, creating a structural synergistic effect that results in a mixing performance improvement far exceeding that of solutions that optimize only a single factor.

[0022] 4. Simple and reliable structure: All innovations are integrated into the hydrocyclone body, without adding any external moving parts or control systems. The structure is simple, the adjustment method is direct and reliable, the manufacturing cost increases minimally, but the performance gains are significant, and it is easy to upgrade existing products. Attached Figure Description

[0023] Figure 1 This is an isometric schematic diagram of the overall structure of an embodiment of the present invention; Figure 2 This is a schematic diagram of the structure of an embodiment of the present invention; Figure 3 This is a schematic diagram of another structural viewpoint of an embodiment of the present invention; Figure 4 This is a schematic diagram of the air pipe outlet and the flue gas entrainment area according to an embodiment of the present invention; Figure 5 This is a schematic diagram of the structure of the gas pipe and the bluff body in an embodiment of the present invention; Figure 6 This is a schematic diagram of the air pipe structure in an embodiment of the present invention; Figure 7 This is a front view schematic diagram of an embodiment of the present invention; Figure 8 This is a side view schematic diagram of an embodiment of the present invention; Figure 9 This is a schematic diagram of the core improved component of the present invention—a cyclone separator with adjustable angle and rounded air guide corners. It focuses on showing the rotatable connection between the blades and the hub, as well as the details of the rounded air guide corners at the blade edges.

[0024] In the diagram: 1-Gas pipe, 11-Gas pipe windward side, 2-Air pipe, 21-Air pipe inlet, 22-Air pipe tapering section, 23-Air pipe outlet, 3-Fluorite pipe, 31-Rib, 32-Fluorite inlet, 4-Blunt body, 5-Swirl converter, 51-Swirl converter blade, 52-Swirl converter hub, 53-Blade shaft, 54-Locking component, 55-Guide rounded corner. Detailed Implementation

[0025] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0026] like Figures 1 to 8 As shown in the figure, an adjustable flue gas internal circulation swirl enhanced mixing low-NOx burner provided by the present invention includes a gas pipe 1, an air pipe 2, a flue gas pipe 3, a blunt body 4, and a swirl generator 5.

[0027] Air pipe 2 is coaxially sleeved on the outside of gas pipe 1; flue gas pipe 3 is axially arranged behind the air outlet of air pipe 2 and is coaxially arranged with air pipe 2 and gas pipe 1; cyclone separator 5 is arranged inside flue gas pipe 3 and fixed on the outside of gas pipe 1; a blunt body 4 is provided at the outlet of gas pipe 1.

[0028] The core of this invention lies in the structure of the cyclone separator 5. For example... Figure 9 As shown, the hydrocyclone 5 in this embodiment consists of a hydrocyclone hub 52 and multiple (e.g., 3) hydrocyclone blades 51. The multiple hydrocyclone blades (51) are evenly distributed circumferentially along the hydrocyclone hub 52, and each hydrocyclone blade 51 has a blade shaft 53 at its root. The hydrocyclone hub 52 has corresponding bearing holes or bushings. The hydrocyclone blades 51 are inserted into the corresponding holes of the hydrocyclone hub 52 via the blade shafts 53, achieving a rotatable connection. A locking component 54 (using a set screw tightening structure) is provided; when the hydrocyclone blade 51 rotates to the desired angle (e.g., 30°), tightening the locking component 54 secures it firmly.

[0029] At the windward leading edge (the edge that the airflow first contacts) of each cyclone blade 51, a smooth guide radius 55 is formed by machining, with a radius of 1 mm (which can be selected in the range of 0.5-2 mm).

[0030] Preferably, the radius of the air guide radius 55 is 0.5mm~2mm.

[0031] Preferably, the angle of the hydrocyclone blade 51 is adjustable in the range of 5° to 60°.

[0032] Preferably, the air pipe 2 is a tapered nozzle structure, and the base circle unfolding angle of the outer contour of its tapered section 22 is 45°~90°.

[0033] Preferably, the flue pipe 3 is fixedly connected to the air pipe 2 by a plurality of ribs 31 evenly distributed along the circumference.

[0034] Preferably, the blunt body 4 is threadedly connected to the gas pipe 1, and a narrow slit is formed between the two for gas to flow out.

[0035] Adjustment and working process of this invention: During burner installation or maintenance, each cyclone blade 51 is manually rotated to a predetermined optimal angle according to the main operating load of the boiler (for example, a larger angle corresponds to high load conditions to enhance mixing, and a smaller angle corresponds to low load conditions to maintain stability). Then, the locking parts 54 of each blade are tightened with tools to fix all cyclone blades 51 at that angle.

[0036] During operation, high-speed air entrains the flue gas into the flue pipe 3, and the mixed airflow flows through the cyclone blades 51 with optimized and fixed angles. The guide radius 55 at the edge of the blades ensures smooth airflow, achieving efficient and uniform mixing, and ultimately mixing with the fuel gas to achieve low-NOx combustion.

[0037] 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 person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and these modifications or substitutions should all be covered 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. An adjustable flue gas internal recirculation cyclone enhanced mixing low-NOx burner, characterized by, The application relates to a gas burner, which comprises a gas pipe, an air pipe, a flue gas pipe, a blunt body and a cyclone; the air pipe is arranged outside the gas pipe; the flue gas pipe is arranged at the rear side of the air pipe outlet in the axial direction; the cyclone is arranged between the gas pipe and the flue gas pipe; the cyclone comprises a cyclone hub and a plurality of cyclone blades which are uniformly distributed around the cyclone hub; the cyclone blades are rotatably connected to the cyclone hub through blade rotating shafts, so that the installation angle of the cyclone blades can be adjusted and fixed after adjustment through locking components; and the edge of the bottom of the cyclone blade is provided with a wind guide round corner.

2. The adjustable flue gas internally recirculating cyclone enhanced mixing low-NOx burner of claim 1, wherein, The cyclone is arranged inside the flue gas pipe and fixed outside the gas pipe.

3. The adjustable flue gas internally recirculating cyclone enhanced mixing low-NOx burner of claim 1, wherein, The radius of the wind guide round corner is 0.5mm-2mm.

4. The adjustable flue gas internally recirculating cyclone enhanced mixing low-NOx burner of claim 1, wherein, The angle of the cyclone blade can be adjusted in the range of 5-60 degrees.

5. The adjustable flue gas internally recirculating, cyclone- enhanced, low-NOx burner of claim 1, wherein, The air pipe is a converging-diverging nozzle structure, and the base circle development angle of the converging section of the air pipe is 45-90 degrees.

6. The adjustable flue gas internally recirculating, cyclone- enhanced, low-NOx combustion burner of claim 1, wherein, The flue gas pipe is fixedly connected with the air pipe through a plurality of ribs which are uniformly distributed in the circumferential direction.

7. The adjustable flue gas internally recirculating, cyclone- enhanced, low-NOx combustion burner of claim 1, wherein, The flue gas pipe, the air pipe and the gas pipe are coaxially arranged.

8. The adjustable flue gas internally recirculating, cyclone- enhanced, low-NOx combustion burner of claim 1, wherein, The outlet of the gas pipe is provided with a blunt body.

9. The adjustable flue gas internally recirculating cyclone enhanced mixing low-NOx burner of claim 8, wherein, The blunt body is threadedly connected with the gas pipe, and a narrow gap for gas outflow is formed between the blunt body and the gas pipe.

10. A method of adjusting and using the adjustable low-NOx combustion burner with inner recirculation of flue gas and enhanced mixing by adjustable cyclone of any of claims 1-9, characterized in that, During the installation or maintenance of the burner, according to the main operation load of the boiler, each cyclone blade is manually rotated to a predetermined angle, and then the locking components of the blades are tightened by using a tool, so that all the cyclone blades are fixed at the angle; during operation, high-speed air is sucked into the flue gas pipe to mix with the flue gas, the mixed gas flows through the cyclone blades which are fixed at the optimized angle, the wind guide round corner of the edge of the blades ensures smooth gas flow, high-efficiency and uniform mixing is realized, and finally low-nitrogen combustion is realized by mixing with the gas.

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