A fuel injection unit structure for the head of a gas turbine combustor

Abstract

A fuel injection unit structure for the head of a gas turbine combustor according to the present invention belongs to the technical field of gas turbines, and includes an injection section and a premixing section coaxially connected. The injection section includes an inner mixing swirler, a gas supply pipe, an outer mixing swirler, and an outer swirler coaxially sleeved from inside to outside in sequence. The premixing section includes a straight section, a converging section, and an outlet section coaxially connected in sequence. The air outlets of each swirler are all connected to the inner cavity of the premixing section. A gas collecting ring is provided inside the gas supply pipe, and an air inlet pipe is provided at one end thereof to connect to the gas collecting ring, and inner and outer injection holes are circumferentially provided at the other end. Air enters from the air inlets of each swirler and forms a swirl, and fuel gas enters the gas collecting ring from the air inlet pipe, and then is respectively sprayed into the air flow channels of the corresponding swirler from the inner and outer injection holes, and enters the premixing section along with the air swirl for internal mixing and then flows into the combustion chamber liner from the outlet section. The present invention solves the problems of poor mixing uniformity and easy spontaneous combustion and flashback when the existing injection unit uses hydrogen fuel in the combustor.

Description

Technical Field

[0001] The present invention belongs to the technical field of gas turbines, and particularly relates to a structure of a head injection unit of a gas turbine combustor. Background Art

[0002] Hydrocarbons such as kerosene or natural gas are often used as fuels in gas turbine combustors. In the future, it is necessary for a new generation of gas turbine combustors to use zero-carbon fuels or low-carbon fuels as alternative fuels. Since hydrogen combustion does not produce carbon-containing products, pure hydrogen and hydrogen-diluted combustible gases have great potential to become alternative fuels. Therefore, it is necessary to develop a structure of a head injection unit of a gas turbine combustor suitable for pure hydrogen and hydrogen-diluted combustible gases.

[0003] For a gas turbine combustor, the head injection unit directly affects the flow field and component field characteristics of the combustor, and further affects the combustion performance. The head injection unit is generally divided into two types, one is a direct injection unit and the other is a premixed injection unit. In the direct injection unit, the fuel and air are not premixed in advance and are independently injected into the combustion chamber liner. There is no risk of flashback and autoignition in the direct injection unit. In the premixed injection unit, the fuel is injected inside the unit and premixed with the mainstream air in advance, and is injected into the combustion chamber liner in the form of a mixture. The premixed injection unit effectively utilizes the internal space of the unit, increases the fuel-air mixing uniformity at the outlet of the head unit, is more conducive to improving the combustion efficiency and the quality of the outlet temperature distribution, and reducing the pollutant emission level; the head injection unit proposed by the present invention is a premixed injection unit.

[0004] Most of the premixed injection units are designed for hydrocarbon fuels and are less suitable for combustors using pure hydrogen or hydrogen-diluted combustible gases. For example, a single-swirl head structure of a combustor in the prior art adopts a fuel injection method with holes in the hub and on the outer wall. When this structure uses pure hydrogen or hydrogen-diluted combustible gas as fuel, due to the decrease in fuel density and penetration depth, the fuel gas ejected from the hub and the outer wall will be concentrated in the central and outer wall regions respectively, resulting in poor mixing uniformity at the unit outlet; another example is a double-swirl head structure of a combustor in the prior art, where the main combustion stage injection holes are located in the main combustion stage swirl channel, and this position is far from the unit outlet. When this structure uses pure hydrogen or hydrogen-diluted combustible gas as fuel, due to the widening of the autoignition and flashback boundaries, autoignition and flashback are likely to occur in the long premixed section. Summary of the Invention

[0005] Technical Problems to be Solved

[0006] To avoid the deficiencies of the prior art, the present invention provides a fuel injection unit structure for the head of a gas turbine combustor, which is applicable to pure hydrogen and hydrogen - blended combustible gas as fuels. By adopting a structure with multiple swirlers cooperating with inner injection holes and outer injection holes in a gas - collecting ring, and through the mixing method in a sudden - expansion space, it can not only mix the gas efficiently and uniformly, but also increase the difficulty of auto - ignition of the mixed gas and the difficulty of flashback in the premixing section, effectively avoiding the phenomena of auto - ignition and flashback in the injection unit when using pure hydrogen and hydrogen - blended combustible gas as fuels.

[0007] A fuel injection unit structure for the head of a gas turbine combustor includes an injection section 2 and a premixing section 1 fixedly connected coaxially with the injection section 2.

[0008] The injection section 2 includes an inner mixing swirler 3, a gas supply pipe 4, an outer mixing swirler 5, and an outer swirler 6 coaxially sleeved from the inside out in sequence. One end of the inner mixing swirler 3, the outer mixing swirler 5, and the outer swirler 6 is an air inlet end, and the other end is an air outlet end. The air outlet ends of each swirler are connected to the inner cavity of the premixing section 1. A cavity gas - collecting ring 41 is provided inside the gas supply pipe 4. One end face of the gas supply pipe 4 is provided with an inlet pipe 42 connected to the gas - collecting ring 41, and the other end is circumferentially provided with a plurality of radially arranged inner injection holes 43 and outer injection holes 44. The inner injection holes 43 penetrate the inner wall 45 of the gas - collecting ring 41, and the outer injection holes 44 penetrate the outer wall 46 of the gas - collecting ring 41.

[0009] The premixing section 1 includes a straight section 11, a converging section 12, and an outlet section 13 connected coaxially in sequence. The straight section 11 and the outlet section 13 are annular. The diameter of the outlet section 13 is smaller than that of the straight section 11. One end of the straight section 11 is fixedly connected to the outer swirler 6 of the injection section 2, and the other end is connected to the outlet section 13 through the converging section 12.

[0010] Air enters from the air inlet ends of the inner mixing swirler 3, the outer mixing swirler 5, and the outer swirler 6, and forms an air swirl through the respective swirler vanes. The fuel gas enters the gas - collecting ring 41 from the inlet pipe 42, and then is respectively sprayed into the air flow channels of the inner mixing swirler 3 and the outer mixing swirler 5 from the inner injection holes 43 and the outer injection holes 44, mixes with the air swirl in the premixing section 1, and then flows into the combustion chamber liner from the outlet section 13.

[0011] A further technical solution of the present invention is that the rotation directions of the inner mixing swirler 3 and the outer mixing swirler 5 are opposite, and the rotation directions of the outer mixing swirler 5 and the outer swirler 6 are opposite; the swirl number of the outer mixing swirler 5 is greater than that of the inner mixing swirler 3 and greater than that of the outer swirler 6.

[0012] A further technical solution of the present invention is that the number of the inner injection holes 43 is the same as or an integer multiple of the number of the blades of the inner mixing cyclone 3, and the same number of inner injection holes 43 are arranged in the blade air channels of each inner mixing cyclone 3; the number of the outer injection holes 44 is the same as or an integer multiple of the number of the blades of the outer mixing cyclone, and the same number of outer injection holes 44 are arranged in the blade air channels of each outer mixing cyclone 5.

[0013] A further technical solution of the present invention is that the ratio of the aperture of the outer injection hole 44 to that of the inner injection hole 43 is greater than the ratio of the swirl numbers of the outer mixing cyclone 5 and the inner mixing cyclone 3 and less than the square ratio of the swirl numbers of the outer mixing cyclone 5 and the inner mixing cyclone 3; the axes of the inner injection hole 43 and the outer injection hole 44 are both located in the same radial plane of the air supply pipe 4, and the distance from the air supply pipe 4 to the end face close to the premixing section 1 is 1 / 12 to 1 / 6 of the axial length of the air supply pipe 4.

[0014] A further technical solution of the present invention is that the number of the blades of the inner mixing cyclone 3 is 12 and the blade angle is 40°; the end faces of the inner mixing cyclone blades 31, the inner hub 32 of the inner mixing cyclone and the outer hub 33 of the inner mixing cyclone are flush at the air inlet 7 end of the inner mixing cyclone 3, the axial lengths of the inner mixing cyclone blades 31 and the outer hub 33 of the inner mixing cyclone are the same, and the axial length of the inner hub 32 of the inner mixing cyclone is greater than the axial length of the outer hub 33 of the inner mixing cyclone.

[0015] A further technical solution of the present invention is that the air collecting ring 41 of the air supply pipe 4 is a cavity formed among an integral front baffle 47, a rear baffle 48, an inner wall 45 of the air collecting ring and an outer wall 46 of the air collecting ring; the air inlet pipe 42 is inserted into the front baffle 47 to be connected to the air collecting ring 41, and the air inlet pipe 42 is hermetically connected to the front baffle 47; the inner wall 45 of the air collecting ring is provided with a first assembly inner wall 451 which is matched with the outer hub 33 of the inner mixing cyclone; the outer wall 46 of the air collecting ring is provided with an assembly outer wall 461 which is matched with the inner hub 52 of the outer mixing cyclone.

[0016] A further technical solution of the present invention is that the number of the blades of the outer mixing cyclone 5 is 12 and the blade angle is 45°; the end faces of the outer mixing cyclone blades 51, the inner hub 52 of the outer mixing cyclone and the outer hub 53 of the outer mixing cyclone are flush at the air inlet 8 end of the outer mixing cyclone 5.

[0017] A further technical solution of the present invention is that the number of blades of the outer cyclone 6 is 12, and the blade angle is 40°; the outer cyclone blades 61, the inner hub 62 of the outer cyclone, and the outer hub 63 of the outer cyclone are flush with the end face of the air outlet end of the outer cyclone 6, and the axial lengths of the inner hub 62 and the outer hub 63 of the outer cyclone are the same; the inner wall of the inner hub 62 of the outer cyclone is provided with a second assembly inner wall 621 that matches the outer hub 53 of the outer mixing cyclone.

[0018] A further technical solution of the present invention is that the outer cyclone blades 61 adopt a light-transmitting design, and the light transmittance is greater than 2.

[0019] A further technical solution of the present invention is that a plurality of cooling holes 14 are evenly distributed in the circumferential direction of the converging section 12 and the outlet section 13, and the axis of the cooling hole 14 is parallel to the axis of the premixing section 1.

[0020] Beneficial effects

[0021] The beneficial effects of the present invention are as follows: For the structure of the fuel injection unit at the head of a gas turbine combustion chamber of the present invention, the inner mixing cyclone is embedded and installed in the gas supply pipe, the gas supply pipe is embedded and installed in the outer mixing cyclone, and the outer mixing cyclone is embedded and installed in the outer cyclone. The fuel gas enters the gas collection ring of the gas supply pipe from the inlet pipe. By means of the inner injection holes and the outer injection holes opened on the inner and outer walls of the gas collection ring, the fuel is forced to cross-flow and inject in the opposite direction, and the injection point is located at the tail end of the injection section. The swirling air fully developed by the inner mixing cyclone and the outer mixing cyclone carries the fuel gas into the premixing section.

[0022] In this structural design, the swirl number of the outer mixing cyclone is greater than that of the inner mixing cyclone and the outer cyclone, and the swirl intensity of the outer mixing cyclone is higher than that of the inner mixing cyclone and the outer cyclone. Therefore, the fuel gas ejected from the outer injection holes will diffuse around with the swirling air formed by the outer mixing cyclone. The swirling air formed by the outer mixing cyclone will squeeze the swirling air formed by the inner mixing cyclone, causing the fuel gas it carries to diffuse inward. Compared with the inner injection holes, the diffusion range of the fuel gas ejected from the outer injection holes is wider. Therefore, the effective flow area of the corresponding outer injection holes is greater than that of the inner injection holes, and the mass flow rate of the fuel gas distributed in the outer injection holes is also greater than that of the fuel gas distributed in the inner injection holes. The double-channel high-speed swirling air carries the fuel and quickly diffuses in the premixing section. The fuel is mixed in two regions in the same space. The swirling motion and the interaction between different swirling airflows dominate the diffusion of the fuel. The premixing performance of the injection unit with this design structure is not sensitive to the properties of the fuel. When pure hydrogen or hydrogen-doped gas is used as the fuel, due to the low density and good followability of hydrogen, it will quickly diffuse with the high-speed swirling air, making the outlet mixture more uniform.

[0023] The present invention adopts the method of sudden-expansion space mixing. Instead of mixing fuel and air in a narrow swirl channel, the fuel gas is brought into the cavity of the premixing section by the swirling air for full mixing. The axial distances between the opening positions of the inner injection holes and the outer injection holes and the rear end face of the injection section are 1 / 12 to 1 / 6 of the axial length of the injection section. The contact time between the premixed gas and the wall surface is short, and the convective heat transfer amount is small. Therefore, the temperature of the premixed gas is lower. The decrease in the temperature of the premixed gas increases the difficulty of spontaneous ignition of the premixed gas. Through sudden-expansion space mixing, the air-fuel ratio in the whole space is increased, and the spontaneous ignition time of the premixed gas is delayed, thereby effectively reducing the spontaneous ignition risk of hydrogen or hydrogen-doped combustible gas.

[0024] The present invention installs an outer swirler outside the outer mixing swirler. Due to the action of centrifugal force, a part of the air passing through the outer swirler will flow along the inner wall of the premixing section towards the downstream outlet section, which can cool down the wall surface; at the same time, since the outer swirler adopts a light-transmitting design and has a part of non-swirling high-speed air flow, the axial velocity of the premixed gas on the wall surface is increased. In addition, a converging section is provided in the premixing section to further increase the overall axial velocity of the premixed gas. Through the setting of the outer swirler, the inner wall of the premixing section is cooled by the rotating air flow, and the rotating air flow contains non-swirling air, which increases the average velocity in the boundary layer of the inner wall surface of the premixing section, and can effectively prevent flashback in the boundary layer of the wall surface; the design of the converging section increases the air flow velocity at the outlet of the whole premixing section, increases the difficulty of flashback, and effectively avoids flashback in the premixing section.

[0025] The present invention is provided with cooling holes in the converging section and the outlet section of the premixing section. After the premixed gas is accelerated through the converging section in the premixing section, a part of it flows out of the premixing section through the cooling holes to cool down the outlet end of the premixed gas of the injection unit.

[0026] The present invention solves the problem that the existing premixed injection unit is not suitable for using pure hydrogen or hydrogen-doped gas as fuel. The structure of the injection unit at the head of the gas turbine combustion chamber provided by the present invention has uniform premixed gas, effectively reduces the spontaneous ignition risk of the premixed gas, and can effectively avoid flashback. Description of the Drawings

[0027] Figure 1 is an exploded view of the structure of the head injection unit according to an embodiment of the present invention;

[0028] Figure 2 is a schematic diagram of the structure of the inner mixing swirler according to an embodiment of the present invention;

[0029] Figure 3 is a schematic diagram of the structure of the air supply pipe according to an embodiment of the present invention;

[0030] Figure 4 is a schematic diagram of the structure of the outer mixing swirler according to an embodiment of the present invention;

[0031] Figure 5 is a schematic diagram of the structure of the outer swirler according to an embodiment of the present invention;

[0032] Figure 6 Schematic diagram of the premixing section of the embodiment of the present invention;

[0033] Figure 7 Front view of the overall structure of the head injection unit of the embodiment of the present invention;

[0034] Figure 8 is Figure 7 A - A sectional view of;

[0035] Figure 9 Partial sectional view of the overall structure of the head injection unit of the embodiment of the present invention.

[0036] Explanation of reference numerals: 1. Premixing section, 11. Straight section, 12. Converging section, 13. Outlet section, 14. Cooling holes, 2. Injection section, 3. Inner mixing swirler, 31. Inner mixing swirler vanes, 32. Inner hub of the inner mixing swirler, 33. Outer hub of the inner mixing swirler, 4. Gas supply pipe, 41. Gas collecting ring, 42. Inlet pipe, 43. Inner injection holes, 44. Outer injection holes, 45. Inner wall of the gas collecting ring, 451. First assembly inner wall, 46. Outer wall of the gas collecting ring, 461. Assembly outer wall, 47. Front baffle, 48. Rear baffle, 5. Outer mixing swirler, 51. Outer mixing swirler vanes, 52. Inner hub of the outer mixing swirler, 53. Outer hub of the outer mixing swirler, 6. Outer swirler, 61. Outer swirler vanes, 62. Inner hub of the outer swirler, 621. Second assembly inner wall, 63. Outer hub of the outer swirler, 7. Air inlet of the inner mixing swirler, 8. Air inlet of the outer mixing swirler, 9. Air inlet of the outer swirler. Detailed implementation manners

[0037] The embodiments described below with reference to the accompanying drawings are exemplary and are intended to explain the present invention, and should not be construed as limiting the present invention.

[0038] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as limiting the present invention.

[0039] Referring to Figure 1 , the structure of the head injection unit of a gas turbine combustor according to the present invention includes an injection section 2 and a premixing section 1 fixedly connected coaxially with the injection section 2.

[0040] Refer to Figure 1 and Figure 9 , the injection section 2 includes an inner mixing cyclone 3, an air supply pipe 4, an outer mixing cyclone 5, and an outer cyclone 6 that are coaxially sleeved in sequence.

[0041] Refer to Figure 1 and Figure 2 , the inner mixing cyclone 3 includes inner mixing cyclone blades 31, an inner hub 32 of the inner mixing cyclone, and an outer hub 33 of the inner mixing cyclone. The inner mixing cyclone 3 is an integrally formed structure. The inner mixing cyclone blades 31 are located between the inner hub 32 of the inner mixing cyclone and the outer hub 33 of the inner mixing cyclone, so that one end of the inner mixing cyclone 3 forms a plurality of air inlets 7 of the inner mixing cyclone. The end where the air inlets 7 are located is the air inlet end of the inner mixing cyclone 3, and the other end is the air outlet end. The inner mixing cyclone 3 is an integral structure. The number of blades of the inner mixing cyclone 3 is 12, and its swirling angle is 40°; the inner mixing cyclone blades 31, the inner hub 32 of the inner mixing cyclone, and the outer hub 33 of the inner mixing cyclone are flush with each other on the end face of the air inlet end of the inner mixing cyclone 3. The axial lengths of the inner mixing cyclone blades 31 and the outer hub 33 of the inner mixing cyclone are equal, and the axial length of the inner hub 32 of the inner mixing cyclone is greater than the axial length of the outer hub 33 of the inner mixing cyclone.

[0042] Refer to Figure 3 and Figures 7 - 9 , the air supply pipe 4 is a ring-shaped columnar structure, and a cavity air collecting ring 41 is provided inside it. The air collecting ring 41 is a cavity formed between the front baffle 47, the rear baffle 48, the inner wall 45 of the air collecting ring, and the outer wall 46 of the air collecting ring of the air supply pipe 4; the front baffle 47, the rear baffle 48, the inner wall 45 of the air collecting ring, and the outer wall 46 of the air collecting ring are an integral structure. The front baffle 47 of the air supply pipe 4 is provided with mounting holes for mounting the intake pipe 42. The intake pipe 42 is inserted into the mounting holes of the front baffle 47 to connect to the air collecting ring 41 and is hermetically connected to the front baffle 47. According to the use requirements, the required number and aperture size of the intake pipes 42 are installed on the front baffle 47. A plurality of inner injection holes 43 and outer injection holes 44 arranged radially along the air supply pipe 4 are provided circumferentially at one end of the air supply pipe 4 close to the rear baffle 48. The inner injection holes 43 penetrate the inner wall 45 of the air collecting ring, and the outer injection holes 44 penetrate the outer wall 46 of the air collecting ring, so that the air collecting ring 41 communicates with the outside air. Specifically, the axes of the inner injection holes 43 and the outer injection holes 44 are both located in the same radial plane of the air supply pipe 4. The distance from this radial plane to the outer end face of the rear baffle 48 is 1 / 12 to 1 / 6 of the distance from the outer end face of the front baffle 47 to the outer end face of the rear baffle 48 of the air supply pipe 4; specifically in this embodiment, the axes of the inner injection holes 43 and the outer injection holes 44 are both at a distance from the outer end face of the rear baffle 48 that is 1 / 7 of the axial length of the injection section 2, and the distance from the outer end face of the front baffle 47 to the outer end face of the rear baffle 48 of the air supply pipe 4 is the same as the axial length of the injection section 2. Refer to Figure 8, on the inner wall 45 of the air collecting ring of the air supply pipe 4, there is a first assembly inner wall 451 that cooperates with the outer hub 33 of the inner mixing cyclone. The axial length of the first assembly inner wall 451 is the same as the axial length of the outer hub 33 of the inner mixing cyclone. During installation, the outer hub 33 of the inner mixing cyclone is embedded in the first assembly inner wall 451, and their end faces are flush. On the outer wall 46 of the air collecting ring of the air supply pipe 4, there is an assembly outer wall 461 that cooperates with the inner hub 52 of the outer mixing cyclone for installing the outer mixing cyclone 5.

[0043] Specifically, the number of the inner injection holes 43 is the same as the number of the blades of the inner mixing cyclone 3 or an integer multiple of the number of the blades of the inner mixing cyclone 3, and the same number of inner injection holes 43 are arranged in the blade air channels of each inner mixing cyclone 3; the number of the outer injection holes 44 is the same as the number of the blades of the outer mixing cyclone 5 or an integer multiple of the number of the blades of the outer mixing cyclone 5, and the same number of outer injection holes 44 are arranged in the blade air channels of each outer mixing cyclone 5. In this embodiment, the number of the inner injection holes 43 on the air supply pipe 4 is the same as the number of the blades of the inner mixing cyclone, both being 12, and the air channels formed by the blades of each inner mixing cyclone 3 correspond one by one to the inner injection holes 43; the number of the outer injection holes 44 on the air supply pipe 4 is the same as the number of the blades of the outer mixing cyclone, both being 12, and the air channels formed by the blades of each outer mixing cyclone 5 correspond one by one to the outer injection holes 44.

[0044] It should be noted that the sum of the cross-sectional hole areas of the air inlet pipe 42 exceeds twice the total cross-sectional hole area of the inner injection holes 43 and the outer injection holes 44 to ensure the air pressure intensity in the air collecting ring 41.

[0045] Refer to Figure 4 、 Figures 7 - 9 , the outer mixing cyclone 5 includes outer mixing cyclone blades 51, an outer hub 52 of the outer mixing cyclone, and an outer hub 53 of the outer mixing cyclone. The outer mixing cyclone 5 is an integrally formed structure. The outer mixing cyclone blades 51 are located between the outer hub 52 of the outer mixing cyclone and the outer hub 53 of the outer mixing cyclone, forming a plurality of outer mixing cyclone air inlets 8 at one end, and the other end is the air outlet end of the outer mixing cyclone. The outer mixing cyclone blades 51, the outer hub 52 of the outer mixing cyclone, and the outer hub 53 of the outer mixing cyclone are flush at the end face of the air inlet end of the outer mixing cyclone, and the axial lengths of the outer hub 52 of the outer mixing cyclone and the outer hub 53 of the outer mixing cyclone are the same. The number of the blades of the outer mixing cyclone 5 is 12, and its swirling angle is 45°. During installation, the outer hub 52 of the outer mixing cyclone is sleeved on the assembly outer wall 461 of the air supply pipe 4, and the end face of the air inlet end of the outer mixing cyclone 5 is flush with the end face of the front baffle 47 of the air supply pipe 4.

[0046] Refer to Figure 5 、 Figures 7 - 9, the outer cyclone 6 includes outer cyclone blades 61, an inner hub 62 of the outer cyclone, and an outer hub 63 of the outer cyclone. The outer cyclone 6 is an integrally formed structure. The outer cyclone blades 61 are located between the inner hub 62 and the outer hub 63 of the outer cyclone, so that one end of the outer cyclone 6 forms a plurality of outer cyclone air inlets 9, and the other end is the air outlet end of the outer cyclone 6. The outer cyclone blades 61, the inner hub 62 of the outer cyclone, and the outer hub 63 of the outer cyclone are flush with each other on the end face of the air outlet end of the outer cyclone 6; the axial lengths of the inner hub 62 and the outer hub 63 of the outer cyclone are the same, and the end faces at both ends are flush. The number of blades of the outer cyclone 6 is 12, and its swirling angle is 40°. The outer cyclone blades 61 are designed with light transmission, and the light transmittance is greater than 2. The inner wall of the inner hub 62 of the outer cyclone is provided with a second fitting inner wall 621 that matches the outer hub 53 of the outer mixing cyclone at the air inlet end. The axial length of the second fitting inner wall 621 is the same as the axial length of the outer hub 53 of the outer mixing cyclone. During installation, the outer mixing cyclone 5 is sleeved on the air supply pipe 4, and its outer hub 53 is embedded in the second fitting inner wall 621 of the outer cyclone 6, and their end faces are flush.

[0047] Refer to Figures 6 - 9 , the premixing section 1 includes a straight section 11, a converging section 12, and an outlet section 13 that are coaxially connected in sequence, and the connecting end faces coincide. The straight section 11 and the outlet section 13 are annular cylindrical structures, and the diameter of the outlet section 13 is smaller than that of the straight section 11. The outer diameter of the straight section 11 is the same as the outer diameter of the outer hub 63 of the outer cyclone, and the inner diameter of the straight section 11 is the same as the inner diameter of the outer hub 63 of the outer cyclone. One end of the straight section 11 is fixedly connected to the outer hub 63 of the outer cyclone, and the other end is convergently and transitionally connected to the outlet section 13 through the converging section 12; specifically, the straight section 11, the converging section 12, and the outlet section 13 of the premixing section 1 are integrally formed structures. A plurality of cooling holes 14 are evenly distributed circumferentially on the converging section 12 and the outlet section 13. Specifically, the converging section 12 is provided with three circles of cooling holes 14, and the number of cooling holes 14 in each circle is set to 24. The outlet section 13 is provided with one circle of cooling holes 14, and the number of cooling holes 14 in the outlet section 13 is 24. The axes of the cooling holes 14 are parallel to the axis of the premixing section 1.

[0048] In order to ensure uniform mixing of the gas, the inner mixing cyclone 3 and the outer mixing cyclone 5 have opposite swirling directions, and the outer mixing cyclone 5 and the outer cyclone 6 have opposite swirling directions; and the swirl number of the outer mixing cyclone 5 is greater than the swirl number of the inner mixing cyclone 3 and also greater than the swirl number of the outer cyclone 6, at least exceeding 15%. The ratio of the aperture of the outer injection hole 44 to the aperture of the inner injection hole 43 is greater than the ratio of the swirl numbers of the outer mixing cyclone 5 and the inner mixing cyclone 3, and less than the ratio of the squares of the swirl numbers of the outer mixing cyclone 5 and the inner mixing cyclone 3.

[0049] Working principle:

[0050] Refer to Figure 8, Figure 9 The oncoming air at the head flows into the air inlet ends of the inner mixing swirler 3, the outer mixing swirler 5, and the outer swirler 6. Specifically, it flows into the vane channels of each swirler from the inner mixing swirler air inlet 7, the outer mixing swirler air inlet 8, and the outer swirler air inlet 9 respectively. After flowing through the vane channels of the swirler, the air obtains a circumferential velocity and enters the premixing section 1 in the form of a swirling flow; the fuel gas enters the gas collecting ring 41 of the gas supply pipe 4 from the gas inlet pipe 42, and is injected into the air flow channel between the inner wall 45 of the gas collecting ring and the inner hub 32 of the inner mixing swirler through the inner injection holes 43, and follows the swirling air flowing through the vanes 31 of the inner mixing swirler into the premixing section 1 for mixing; at the same time, it is injected into the air flow channel between the outer wall 46 of the gas collecting ring and the inner hub 62 of the outer swirler through the outer injection holes 44, and follows the swirling air flowing through the vanes 51 of the outer mixing swirler into the premixing section 1 for mixing. After the premixed gas flow is accelerated by the converging section 12 in the premixing section 1, a part of it flows out of the head of the premixing section 1 through the cooling holes 14 of the converging section 12 and the outlet section 13, which is used to cool the head outlet end face of the premixing section 1, and the other part directly flows into the combustion chamber from the central outlet of the outlet section 12.

[0051] Since the swirling intensity of the outer mixing swirler 5 is higher than that of the inner mixing swirler 3 and the outer swirler 6, the fuel gas ejected from the outer injection holes 44 will diffuse around with the swirling air formed by the outer mixing swirler 5. The swirling air formed by the outer mixing swirler 5 will squeeze the swirling air formed by the inner mixing swirler 3, causing the fuel gas carried by it to diffuse inward. The cross-jet zoning mixing and the interaction between different swirling airflows dominate the diffusion of the fuel. The premixing performance of the injection unit of this design is not sensitive to the properties of the fuel. When pure hydrogen or hydrogen-enriched fuel gas is used as the fuel, due to the small density and good followability of hydrogen, it diffuses faster with the high-speed swirling air. Compared with the inner injection holes 43, the diffusion range of the fuel gas ejected from the outer injection holes 44 is wider. The ratio of the aperture of the outer injection holes 44 to the inner injection holes 43 is greater than the ratio of the swirl numbers of the outer mixing swirler 5 and the inner mixing swirler 3, and less than the square of this ratio. Therefore, the effective flow area of the outer injection holes 44 is larger than that of the inner injection holes 43, and the mass flow rate of the fuel gas distributed in the outer injection holes 44 is also greater than that of the fuel gas distributed in the inner injection holes 43. A reasonable fuel distribution ratio helps the fuel to diffuse more uniformly in the premixing section.

[0052] Since the sudden-expansion space mixing method is adopted, the fuel gas and air are not mixed in a narrow swirling channel. The premixed gas equivalent ratio per unit volume is small, and the axial distance between the opening positions of the inner injection holes 43 and the outer injection holes 44 and the rear end face of the injection section is 1 / 7 of the axial length of the injection section 2. The contact time between the premixed gas and the wall is short, and the convective heat transfer amount is small. Therefore, the temperature of the premixed gas is low, which delays the spontaneous ignition time of the premixed gas and effectively avoids the spontaneous ignition of pure hydrogen or hydrogen-enriched fuel gas in the premixing section 1.

[0053] In the present invention, an outer cyclone 6 is installed outside the outer mixing cyclone 5. Due to the action of centrifugal force, a part of the air passing through the outer cyclone 6 will flow along the walls of the straight section 11 and the converging section 12 towards the downstream outlet section 13, achieving the cooling of the walls. Since the outer cyclone adopts a light-transmitting design and has a part of non-rotating high-speed air flow, it can accelerate the axial velocity of the air mixture on the walls and reduce the risk of flashback in the wall boundary layer. In addition, the converging section 12 further increases the overall axial velocity of the air mixture and makes it more difficult for flashback to occur in the core turbulent region.

[0054] In the above embodiment, the specific dimensions of the injection unit structure at the head of the gas turbine combustion chamber are as follows:

[0055] According to the parameters given by the overall engine design, it is determined that the total length of the injection unit structure at the head of the gas turbine combustion chamber in the embodiment of the present invention is 30 mm, and the outer diameter is 42 mm. The axial length of the injection section 2 is 14 mm, the axial length of the premixing section 1 is 16 mm, the outer diameter of the outer cyclone 6 in the injection section 2 is 42 mm, and the outer diameter of the straight section 11 in the premixing section 1 is 42 mm.

[0056] Specifically: In the injection section 2, the outer diameter and axial length of the inner hub 32 of the inner mixing cyclone are 6 mm and 14 mm respectively, the inner diameter, axial length, and outer diameter of the outer hub 33 of the inner mixing cyclone are 10 mm, 4 mm, and 10.7 mm respectively, the number of blades 31 of the inner mixing cyclone is 12, and the blade angle is 40 degrees.

[0057] There are 2 evenly distributed inlet pipes 42 of the gas supply pipe 4 on the front baffle 47. The inner diameter and outer diameter of the inlet pipe 42 are 1.3 mm and 2.3 mm respectively; the inner diameter and outer diameter of the outer wall 46 of the gas collecting ring are 14.3 mm and 16 mm respectively, and the outer diameter of the assembled outer wall 461 is 15.3 mm; the inner diameter and outer diameter of the inner wall 45 of the gas collecting ring are 10 mm and 11.7 mm respectively, and the inner diameter of the first assembled inner wall 451 is 10.7 mm; the aperture of the inner injection hole 43 is 0.2 mm; the aperture of the outer injection hole 44 is 0.3 mm; the thickness of the front baffle 47 is 0.5 mm; the thickness of the rear baffle 48 is 1 mm; the axial distance from the axes of the inner injection hole 43 and the outer injection hole 44 to the outer end face of the rear baffle 48 is 2 mm, which is equivalent to 1 / 7 of the length 14 mm of the injection section 2. The total aperture area of the inner injection hole 43 and the outer injection hole 44 is 1.23 mm 2 The sum of the inner hole cross-sectional areas of the inlet pipes 42 is 2.65 mm 2 The sum of the inner hole cross-sectional areas of the inlet pipes 42 is 2.15 times the total area of the injection holes.

[0058] The inner hub 52 of the external mixing cyclone has an inner diameter, axial length, and outer diameter of 15.3 mm, 6.5 mm, and 16 mm respectively; the inner hub 53 of the external mixing cyclone has an inner diameter, axial length, and outer diameter of 20 mm, 6.5 mm, and 24 mm respectively; the number of blades 51 of the external mixing cyclone is 12, and the blade angle is 45 degrees.

[0059] The inner hub 62 of the external cyclone has an inner diameter, axial length, and outer diameter of 20 mm, 14 mm, and 28 mm respectively. The inner diameter and length of the second assembly inner wall 621 on the inner hub 62 of the external cyclone are 24 mm and 6.5 mm respectively; the inner hub 63 of the external cyclone has an inner diameter, axial length, and outer diameter of 38 mm, 14 mm, and 42 mm respectively; the number of blades 61 of the external cyclone is 12, and the blade angle is 40 degrees.

[0060] In the premixing section 1: the straight section 11 has an inner diameter, axial length, and outer diameter of 38 mm, 8 mm, and 42 mm respectively; the axial length of the converging section 12 is 7 mm; the outlet section 13 has an inner diameter, axial length, and outer diameter of 24 mm, 1 mm, and 28 mm respectively. The cooling holes 14 are evenly distributed in 3 circles along the axial direction on the converging section 12, with 24 holes in each circle; the cooling holes 14 are evenly distributed in 1 circle along the axial direction on the outlet section 13, and the number is also 24; the diameter of the cooling holes 14 is 0.5 mm.

[0061] The swirl numbers of the internal mixing cyclone 3, the external mixing cyclone 5, and the external cyclone 6 are calculated according to the following formula:

[0062]

[0063] Where Sn is the swirl number, Z is the ratio of the outer diameter of the inner hub of the cyclone to the inner diameter of the outer hub, and θ is the blade angle of the cyclone. It can be calculated that the swirl numbers of the internal mixing cyclone 3, the external mixing cyclone 5, and the external cyclone 6 are 0.69, 0.90, and 0.73 respectively. Among them, the swirl number of the external mixing cyclone 5 is the largest, which is 30.43% higher than the swirl number of the internal mixing cyclone 3.

[0064] The blades 61 of the external cyclone adopt a light-transmitting design. The light transmittance of the cyclone is calculated according to the following formula:

[0065]

[0066] Where σ is the light transmittance, L is the length of the cyclone, D is the outer diameter of the cyclone, n is the number of blades of the cyclone, and θ is the blade angle of the cyclone; the light transmittances of the internal mixing cyclone 3, the external mixing cyclone 5, and the external cyclone 6 are 0.87, 0.96, and 2.48 respectively. Among them, the internal mixing cyclone 3 and the external mixing cyclone 5 are not light-transmitting, and the external cyclone 6 adopts a light-transmitting design with a light transmittance greater than 2.

[0067] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention without departing from the principles and spirit of the present invention.

Claims

1. A structure of a fuel injection unit at the head of a gas turbine combustor, characterized in that: it includes an injection section (2) and a premixing section (1) fixedly connected coaxially with the injection section (2); the injection section (2) includes an inner mixing swirler (3), a gas supply pipe (4), an outer mixing swirler (5) and an outer swirler (6) coaxially sleeved from inside to outside in sequence; one ends of the inner mixing swirler (3), the outer mixing swirler (5) and the outer swirler (6) are all air inlet ends, and the other ends are all air outlet ends. The air outlet ends of each swirler are all communicated with the inner cavity of the premixing section (1); a cavity air collecting ring (41) is arranged inside the gas supply pipe (4). One end face of the gas supply pipe (4) is provided with an air inlet pipe (42) communicated with the air collecting ring (41), and the other end is circumferentially provided with a plurality of radially arranged inner injection holes (43) and outer injection holes (44). The inner injection holes (43) penetrate through the inner wall (45) of the air collecting ring (41), and the outer injection holes (44) penetrate through the outer wall (46) of the air collecting ring (41); the premixing section (1) includes a straight section (11), a converging section (12) and an outlet section (13) connected coaxially in sequence. The straight section (11) and the outlet section (13) are annular. The diameter of the outlet section (13) is smaller than that of the straight section (11). One end of the straight section (11) is fixedly connected with the outer swirler (6) of the injection section (2), and the other end is connected to the outlet section (13) through the converging section (12) for transition connection; the rotation directions of the inner mixing swirler (3) and the outer mixing swirler (5) are opposite, and the rotation directions of the outer mixing swirler (5) and the outer swirler (6) are opposite; the swirl number of the outer mixing swirler (5) is greater than that of the inner mixing swirler (3) and greater than that of the outer swirler (6); the aperture ratio of the outer injection holes (44) to the inner injection holes (43) is greater than the ratio of the swirl numbers of the outer mixing swirler (5) to the inner mixing swirler (3), and less than the square ratio of the swirl numbers of the outer mixing swirler (5) to the inner mixing swirler (3); the axes of the inner injection holes (43) and the outer injection holes (44) are both located in the same radial plane of the gas supply pipe (4), and the distance from the end face of the gas supply pipe (4) close to the premixing section (1) is 1 / 12 to 1 / 6 of the axial length of the gas supply pipe (4); the outer swirler blades adopt a light-transmitting design, and the light transmittance is greater than 2; a plurality of cooling holes (14) are evenly distributed circumferentially on both the converging section (12) and the outlet section (13), and the axes of the cooling holes (14) are parallel to the axis of the premixing section (1); Air enters from the air inlet ends of the inner mixing swirler (3), the outer mixing swirler (5) and the outer swirler (6), and forms an air swirl through the respective swirler blades; fuel gas enters the air collecting ring (41) from the air inlet pipe (42), and then is respectively sprayed into the air flow channels of the inner mixing swirler (3) and the outer mixing swirler (5) from the inner injection holes (43) and the outer injection holes (44), is mixed with the air swirl and enters the premixing section (1) for mixing, and then flows into the combustion chamber liner from the outlet section (13).

2. The structure of the fuel injection unit at the head of the gas turbine combustor according to claim 1, characterized in that: The number of the inner injection holes (43) is the same as the number of the blades of the inner mixing swirler (3) or an integral multiple of the number of the blades of the inner mixing swirler (3), and the same number of inner injection holes (43) are arranged in the blade air channels of each inner mixing swirler (3); the number of the outer injection holes (44) is the same as the number of the blades of the outer mixing swirler (5) or an integral multiple of the number of the blades of the outer mixing swirler (5), and the same number of outer injection holes (44) are arranged in the blade air channels of each outer mixing swirler (5).

3. The structure of the injection unit at the head of the gas turbine combustor according to claim 1, characterized in that: The number of the blades of the inner mixing swirler (3) is 12, and the blade angle is 40°; the end faces of the inner mixing swirler blades (31), the inner hub (32) of the inner mixing swirler, and the outer hub (33) of the inner mixing swirler are flush at the air inlet (7) end of the inner mixing swirler (3), the axial lengths of the inner mixing swirler blades (31) and the outer hub (33) of the inner mixing swirler are the same, and the axial length of the inner hub (32) of the inner mixing swirler is greater than the axial length of the outer hub (33) of the inner mixing swirler.

4. The structure of the injection unit at the head of the gas turbine combustor according to claim 1, characterized in that: The gas collecting ring (41) of the gas supply pipe (4) is a cavity formed among a front baffle (47), a rear baffle (48), an inner wall (45) of the gas collecting ring, and an outer wall (46) of the gas collecting ring which are of an integral structure; the inlet pipe (42) is inserted into the front baffle (47) to be connected to the gas collecting ring (41), and the inlet pipe (42) is hermetically connected to the front baffle (47); the inner wall (45) of the gas collecting ring is provided with a first assembling inner wall (451) which is matched with the outer hub (33) of the inner mixing swirler; the outer wall (46) of the gas collecting ring is provided with an assembling outer wall (461) which is matched with the inner hub (52) of the outer mixing swirler.

5. The structure of the injection unit at the head of the gas turbine combustor according to claim 1, characterized in that: The number of the blades of the outer mixing swirler (5) is 12, and the blade angle is 45°; the end faces of the outer mixing swirler blades (51), the inner hub (52) of the outer mixing swirler, and the outer hub (53) of the outer mixing swirler are flush at the air inlet (8) end of the outer mixing swirler (5).

6. The structure of the injection unit at the head of the gas turbine combustor according to claim 1, characterized in that: The number of the blades of the outer swirler (6) is 12, and the blade angle is 40°; the end faces of the outer swirler blades (61), the inner hub (62) of the outer swirler, and the outer hub (63) of the outer swirler are flush at the air outlet end of the outer swirler (6), and the axial lengths of the inner hub (62) and the outer hub (63) of the outer swirler are the same; the inner wall of the inner hub (62) of the outer swirler is provided with a second assembling inner wall (621) which is matched with the outer hub (53) of the outer mixing swirler.

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