A micro-mixing diffusion combustion chamber head based on spiral structure and fast rotary cutting

Abstract

A micro-mixing diffusion combustion chamber head based on spiral structure and rapid rotary cutting relates to the technical field of hydrogen fuel gas turbine. It comprises a micro-mixing unit, a spiral wall surface cyclone structure, a hydrogen injection hole and a hydrogen injection channel. The micro-mixing unit is internally designed with an air flow channel, which is helically extended along the thickness of the micro-mixing unit by a specific shape section to form an air flow channel with a wall surface cyclone structure. When the air flows along the helical channel of the wall surface cyclone structure, it rotates under the action of the boundary layer to achieve the purpose of pre-rotating air. At the outlet side wall of the helical channel, an injection hole for injecting hydrogen is arranged, which is at an angle with the center of the air flow channel and opposite to the direction of the pre-rotating air, forming a vortex to enhance the diffusion of hydrogen and air and the heat transfer of high-temperature mixed gas, thereby improving the temperature uniformity at the outlet of the combustion chamber.

Description

Technical Field

[0001] The present invention relates to the technical field of hydrogen fuel gas turbines, and in particular to a micro-mixing diffusion combustion chamber head based on a spiral structure and rapid rotary cutting. Background Art

[0002] With the development of scientific research, industry, and aerospace, as well as the increasing demand for environmental protection in the new era, the demand for power systems with high energy density, high power-to-weight ratio, and zero carbon emissions is becoming increasingly apparent. Compared to current traditional fuels, hydrogen has the advantages of lower ignition energy, high calorific value, and zero carbon emissions. At the same time, its mass energy density is significantly higher than that of traditional fuels, making it a fuel with great potential.

[0003] When traditional gas turbines use kerosene as fuel, they usually adopt a swirl premixed combustion method to reduce pollution emissions. Due to the low density, fast combustion speed and high combustion temperature of hydrogen, if this method is used directly to burn hydrogen, it will cause flashback and high NOx emissions.

[0004] Chinese patent application CN202310164173.6 discloses a combustor mild-mixing head, a gas turbine combustor, and a gas turbine. The combustor mild-mixing head comprises a honeycomb unit, a vortex generator, and an injection channel. The honeycomb unit is provided with a plurality of honeycomb holes extending along the thickness of the honeycomb unit to form a flow channel within the unit. Injection holes for injecting hydrogen are provided on the sidewalls of the flow channel. The vortex generators provided in the flow channel within the honeycomb holes increase the disturbance of the air in all directions, generating directional vortices along the flow path, reducing the air flow rate, and allowing hydrogen to be dispersed into the air very quickly across the entire cross-section along the flow path. This reduces NOx emissions from mild-mix combustion, avoids hydrogen flashback, enhances the safety and service life of hydrogen combustion, and reduces carbon emissions and carbon management costs.

[0005] Chinese patent application CN202310164173.6 describes a micro-mixing nozzle that utilizes two main design elements: a bluff body flow and a transverse jet flow, for axial hydrogen mixing. This patent combines these two elements with traditional swirl combustion technology, achieving flame stabilization through the axial vortex generated by the bluff body flow and the axial vortex generated by the wall swirl flow, thereby improving temperature uniformity at the combustion chamber outlet. Summary of the Invention

[0006] The present invention aims to provide a micro-mixing diffusion combustor head based on a spiral structure and rapid rotary shearing, which better addresses the limitations of conventional low-emission combustor technologies in safely and efficiently burning hydrogen. This invention combines two mainstream existing combustor designs: the transverse jet hydrogen micro-mixing combustor and the swirl combustor. This design addresses the former's inability to utilize swirl to improve combustor temperature uniformity and the latter's high NOx emissions, respectively. Furthermore, the use of diffusion combustion reduces the risk of flashback.

[0007] The present invention provides a micro-mixing diffusion combustion chamber head based on a spiral structure and rapid peeling, comprising:

[0008] A micro-mixing unit contains an air flow channel, which is composed of four circular holes arranged in a circumferential array and spirally extending along the thickness of the micro-mixing unit to form a flow channel; in the flow channel, the air flows from upstream to downstream; and four hydrogen injection holes are provided on the inner wall of each flow channel, and the hydrogen injection holes are symmetrical about the central axis of the channel;

[0009] A hydrogen injection channel is connected to the hydrogen injection hole and is used to supply hydrogen to the hydrogen injection hole. The hydrogen is injected into the air flow channel at a certain angle and mixed with the incoming air. The end of the air flow channel is slightly expanded to reduce the axial velocity of the mixed air.

[0010] The spiral wall swirl structure of the air flow channel drives the mainstream air to rotate clockwise. Near the hydrogen injection hole, when the air acts as the main jet and flows through the injection channel, the hydrogen injection hole ejects hydrogen in the opposite direction of the air rotation to form a circumferential vortex. The existence of the circumferential vortex can better mix the hydrogen and air. At the same time, after the mixture is ignited, the circumferential vortex has the function of exchanging heat and improving the uniformity of the outlet temperature.

[0011] A combustion chamber mild-mix head contains a plurality of mild-mix units, and the distance L between the mild-mix units ranges from 19 to 21 mm.

[0012] The air flow channel is formed by four spiral channels that are arranged and fused in an interlaced manner; the cross-section of the four spiral channels is a circle with a diameter of 3.1 mm, which is called a circular cross-section; the circular cross-section is arranged in a circular array relative to the center point of the air flow channel, and the center of the circle is offset by 1.55 mm compared to the above-mentioned center point, and the shape of the intersection of the four circular cross-sections is the shape of the air flow channel cross-section; the air flow channel cross-section extends along the thickness direction of the air flow channel to form a clockwise spiral channel, which is the spiral channel formed by the above-mentioned four interlaced arrangements and fusion; the lead S of the spiral channel is 10 to 20 mm.

[0013] In the micro-mixing head of the combustion chamber provided by the present invention, the end surface of the air flow passage outlet is referred to as the mixed gas outlet. The distance between the hydrogen injection hole and the mixed gas outlet is referred to as the mixing distance D, which is 1 to 2 mm. The diameter Dj of the hydrogen injection hole is 0.4 to 0.5 mm.

[0014] According to the mild mixing head of the combustion chamber provided by the present invention, the acute angle formed by the injection channel and its diameter becomes the hydrogen injection deflection angle α, the range of α is: 0-15°, and the angle direction is counterclockwise.

[0015] The boundary layer of the air flow channel of the combustion chamber mild mixing head provided by the present invention drives the mainstream air to rotate clockwise. Near the injection channel, when the air flows through the injection channel as the main jet, hydrogen is ejected from the injection channel in the opposite direction of the air rotation. The hydrogen jet injected along the counterclockwise inclination and the mainstream air rotating clockwise will form four circumferential vortices, referred to as circumferential vortices.

[0016] Continuing to flow along the axial direction, the mixture of hydrogen and air forms an axial vortex under the action of the wall between the micro-mixing units, which is referred to as the axial vortex. That is, the wall of the micro-mixing unit is used as a blunt body to generate blunt body turbulence.

[0017] Compared with the existing technology, the outstanding advantages and technical effects of the present invention are: the circumferential vortex generated by the interaction between the boundary layer swirl of the air flow channel and the hydrogen jet is divided into three stages, as follows:

[0018] (1) Independent circumferential vortex stage: At the origin of the air mixture, the circumferential vortex is small in size and appears between the micro-mixing units. As the circumferential position increases, the circumferential vortex gradually moves away from the air flow channel and moves between the micro-mixing units. Under the influence of the counterclockwise flow of the mainstream air, the circumferential vortex gradually approaches until it meets and merges. Its position is not axisymmetric, and the airflow in the middle will gradually dissipate due to its opposite flow direction.

[0019] (2) Merging Circumferential Vortex Stage: As the axial direction deepens, the independent circumferential vortices gradually merge to form a merged circumferential vortex, which rotates counterclockwise, the same as the mainstream air. The airflow exchanges energy through the vortex, and as the axial distance increases, the shape of the circumferential vortex gradually changes. In this process, the temperature of the airflow gradually becomes uniform.

[0020] (3) As the axial distance increases, the vortex characteristics gradually dissipate, and then the gas from the center of the micro-mixing unit directly points to the adjacent micro-mixing unit to exchange matter and energy.

[0021] The present invention enhances the diffusion of hydrogen and air and the heat transfer of high-temperature mixed gas, thereby improving the temperature uniformity at the combustion chamber outlet and increasing the mixing degree of air and hydrogen. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a structural diagram of the mild-mix head of the combustion chamber of the present invention;

[0023] Figure 2 Schematic diagram of the cross-sectional structure of the mild-mix head of the combustion chamber of the present invention;

[0024] Figure 3 This is a diagram showing the mixing principle of the mild mixing head of the combustion chamber of the present invention;

[0025] Figure 4 is a cross-sectional view of a mild-mix head of a combustion chamber of the present invention;

[0026] Figure 5 This is a diagram showing the circumferential vortex variation of the mild mixing head of the combustion chamber of the present invention.

[0027] The marks in the figure are:

[0028] 1. Micro-mixing unit; 2. Air flow channel; 3. Hydrogen injection channel; 4. Hydrogen injection hole; 5. Circular cross section of spiral channel; 6. Axial vortex; 7. Circumferential vortex; 8. Independent circumferential vortex; 9. Combined circumferential vortex. DETAILED DESCRIPTION

[0029] In order to make the objectives, technical solutions and advantages of the present invention more clear, the technical solutions of the present invention will be further described in detail below with reference to the accompanying drawings in the present invention.

[0030] Using a traditional swirl premixed combustion chamber to burn hydrogen is prone to flashback and high NOx emissions. Furthermore, due to the low density of hydrogen, the ability of a simple transverse jet to mix hydrogen is very limited. The present invention utilizes micro-mixed diffusion combustion to produce a small flame, thus avoiding this problem.

[0031] Compared to Chinese patent application CN202310164173.6, the present invention uses a spiral-structured wall swirl air flow channel and an angled jet hydrogen injection channel. These two structures will cause the air and hydrogen mixture to generate a circumferential vortex, which will gradually expand, merge, and dissipate along the axis. In this process, the heat exchange effect brought by the circumferential vortex will make the combustion chamber outlet temperature field more uniform.

[0032] like Figures 1 to 5As shown, this embodiment of a micro-mixing diffusion combustion chamber head based on a spiral structure and rapid rotary cutting includes: a micro-mixing unit 1, an air flow channel 2, and a hydrogen injection channel 3. The air flow channel 2 is located within the micro-mixing unit 1. The micro-mixing unit 1 also includes a hydrogen injection channel 3, which is connected to a hydrogen injection hole 4. Hydrogen flows from the injection channel 3 to the hydrogen injection hole 4, from which it is ejected outward and mixes with the mainstream air. At the end of the air flow channel, the area is slightly expanded to reduce the mixing speed.

[0033] A combustion chamber's micro-mixing head contains multiple micro-mixing cells, with a spacing L between them ranging from 19 to 21 mm. As shown in Table 1, when L is approximately 20 mm, the flame reaches a maximum temperature of 2721 K. This temperature decreases as the spacing increases. A stable flame cannot be produced at L of 16 mm. As L increases, the temperature uniformity at the outlet deteriorates.

[0034] Table 1 Effect of micro-hybrid unit spacing L on temperature characteristics

[0035]

[0036] like Figure 4 As shown, the air flow channel is formed by four interlaced spiral channels. The cross-sections of the four spiral channels are circles with the same diameter of 3.1mm, referred to as circular sections. The spiral channel circular sections 5 are arranged in a circular array relative to the center point of the air flow channel, with the centers of the circles offset by 1.55mm from the aforementioned center point. The intersection of the four circular sections forms the shape of the air flow channel cross-section. The air flow channel cross-section extends along the thickness of the air flow channel, forming a clockwise spiral channel. The lead S of the spiral channel is 10 to 20mm. As air flows from upstream to downstream, it rotates clockwise under the influence of the air boundary layer.

[0037] Table 2 Influence of helical lead S on temperature characteristics

[0038]

[0039] The helical lead S has little effect on the maximum total temperature at the outlet, but a significant impact on the average total temperature at the outlet. When S is 12 mm, the outlet temperature uniformity is lowest. When S is greater than 12 mm, the outlet uniformity gradually improves as S increases. When S is 10 mm, the outlet temperature uniformity of the combustion chamber actually increases.

[0040] When the mainstream air approaches the hydrogen injection hole, it mixes with the hydrogen injected from the injection hole. The hydrogen is then ejected along the injection channel at a certain angle, in a counterclockwise direction opposite to the air's rotation. The counterclockwise ejected hydrogen interacts with the clockwise mainstream air, forming four circumferential vortices7. These circumferential vortices can gradually expand and merge along the axis, creating heat exchange between the micro-mixing units, thereby improving the uniformity of the combustion chamber outlet temperature.

[0041] like Figure 3 The gas leaving the mixture outlet will use the wall of the micro-mixing head as a stepped blunt body, and form an axial vortex 6 under the action of the blunt body turbulence. The main function of the axial vortex 6 is to stabilize the flame.

[0042] Table 3 Effect of mixing distance D on temperature characteristics

[0043]

[0044] like Figure 3 As shown, the mixing distance D ranges from 1 to 2 mm. As D increases, the maximum flame temperature at the outlet remains largely unaffected, while the average outlet temperature shows a downward trend. This means that outlet temperature uniformity deteriorates with increasing D, but levels off when D is greater than or equal to 1.5 mm. A larger D indicates a closer distance between the hydrogen injection hole and the mixed gas outlet. While D of 0.5 mm offers favorable parameters, considerations arise regarding the layout of the hydrogen pipeline and the high-temperature resistance of the material.

[0045] like Figure 3 As shown in Table 4, the diameter of the hydrogen injection hole ranges from 0.4 to 0.5 mm. As can be seen from Table 4, when Dj is less than 0.45 mm, the maximum flame temperature cannot reach 2721 K, and when Dj is equal to 0.55 mm, tempering occurs, that is, a high-temperature point is generated near the hydrogen injection hole. As Dj increases, the temperature uniformity at the pressure outlet increases. That is, the U value decreases. When Dj is greater than 0.45, the U value shows an insignificant downward trend, which is specifically manifested in that the maximum total temperature at the outlet shows a slight decrease, while the average total temperature at the outlet shows a slight upward trend.

[0046] Table 4 Effect of hydrogen injection hole diameter Dj on temperature characteristics

[0047]

[0048] like Figure 3As shown in Table 5, the acute angle α formed by the injection channel and the diameter at the location of the injection channel ranges from 0° to 15°. As shown in Table 5, a negative value indicates that the hydrogen injection angle has the same orientation as the helical rotation, meaning that the hydrogen injection contributes to the overall gas swirl. A positive value indicates that the hydrogen injection angle has the opposite orientation to the helical rotation, meaning that the hydrogen injection is detrimental to the overall gas swirl but contributes to the formation of a circumferential vortex. The effect of the hydrogen injection deflection angle α on the maximum flame temperature Tmax is shown in Table 5. As α increases to 15°, the maximum flame temperature begins to decline.

[0049] Table 5 Effect of acute angle α on temperature characteristics

[0050]

[0051] like Figure 5 Figure 1 shows the development of the circumferential vortex, which gradually evolves from independent circumferential vortices 8 to merged circumferential vortices 9 after exiting the mild mixing unit. During this process, the mixed gas transfers heat to the surrounding area under the action of the circumferential vortex, improving the uniformity of the outlet temperature.

[0052] The micro-mixing head of the combustion chamber provided by the present invention can form different micro-mixing diffusion combustion chamber heads according to the number of air flow channels in the micro-mixing unit 1, the arrangement spacing, the shape of the air flow channel 2, the angle of the hydrogen injection channel 3 relative to the air flow channel, the cross-sectional shape along the injection direction of its length, and the number and shape of the hydrogen injection holes. The appropriate combination of parameters can improve the mixing degree of air and hydrogen.

[0053] The above embodiments are only preferred embodiments of the present invention and should not be considered to limit the scope of the present invention. All equivalent changes and improvements made within the scope of the present invention should still fall within the scope of the present invention.

Claims

1. A micro-mixing diffusion combustion chamber head based on a spiral structure and rapid peeling, characterized by include: A micro-mixing unit contains a single air flow channel, which is composed of four circular holes arranged in a circumferential array and extending spirally along the thickness of the micro-mixing unit to form a flow channel; air flows from upstream to downstream in the flow channel; Four hydrogen injection holes are provided on the inner wall of each flow channel, and the hydrogen injection holes are symmetrical about the central axis of the channel; A hydrogen injection channel is connected to the hydrogen injection hole and is used to supply hydrogen to the hydrogen injection hole. The hydrogen is injected into the air flow channel at a certain angle and mixed with the incoming air. The end of the air flow channel is slightly expanded to reduce the axial velocity of the mixed gas; The spiral wall swirl structure of the air flow channel drives the mainstream air to rotate clockwise. Near the hydrogen injection hole, when the air acts as the main jet and flows through the hydrogen injection channel, the hydrogen injection hole ejects hydrogen in the opposite direction of the air rotation, forming a circumferential vortex. The presence of circumferential vortices enables better mixing of hydrogen and air. At the same time, after the mixture is ignited, the circumferential vortices have the function of exchanging heat and improving the uniformity of the outlet temperature. A combustion chamber mild-mix head contains a plurality of mild-mix units, and the distance L between the mild-mix units ranges from 19 to 21 mm.

2. A micro-mixing diffusion combustion chamber head based on a spiral structure and rapid peeling as claimed in claim 1, characterized in that: The air flow channel is formed by four spiral channels that are staggered and fused with each other; the cross-section of the four spiral channels is a circle with a diameter of 3.1 mm, which is called a circular cross-section; the circular cross-section is arranged in a circular array compared to the center point of the air flow channel, and the center of the circle is offset by 1.55 mm compared to the above center point, and the shape of the intersection of the four circular cross-sections is the shape of the air flow channel cross-section.

3. The micro-mixing diffusion combustion chamber head based on a spiral structure and rapid peeling as claimed in claim 1, characterized in that: The cross section of the air flow channel extends along the thickness direction of the air flow channel to form a spiral channel with a clockwise rotation direction, that is, four spiral channels are arranged and merged with each other; the lead S of the spiral channel is 10 to 20 mm.

4. A micro-mixing diffusion combustion chamber head based on a spiral structure and rapid peeling as claimed in claim 1, characterized in that: The end face of the outlet end of the air flow channel is called the mixed gas outlet, and the length from the air inlet to the mixed gas outlet is 15 mm; the distance between the position of the hydrogen injection hole and the mixed gas outlet is called the mixing distance D, which is 1 to 2 mm; the aperture Dj of the hydrogen injection hole is 0.4 to 0.5 mm.

5. The micro-mixing diffusion combustion chamber head based on a spiral structure and rapid peeling as claimed in claim 1, characterized in that: The acute angle formed by the hydrogen injection channel and the diameter at the position where it is located is the hydrogen injection deflection angle α, the range of α is: 0 to 15 degrees, and the angle forming direction is counterclockwise.

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