CN114877373B

CN114877373B - Combined nozzle device for preventing backfire

Info

Publication number: CN114877373B
Application number: CN202210400208.7A
Authority: CN
Inventors: 任彤彤; 张善军; 邵志强; 金戈
Original assignee: AECC Shenyang Engine Research Institute
Current assignee: AECC Shenyang Engine Research Institute
Priority date: 2022-04-15
Filing date: 2022-04-15
Publication date: 2023-08-22
Anticipated expiration: 2042-04-15
Also published as: CN114877373A

Abstract

The application relates to a backfire preventing technology of a low-pollution combustion chamber of a gas turbine, in particular to a combined nozzle device for preventing backfire, which is provided with a cyclone, a premixing passage cylinder and a central body; the central body is arranged in the premixing passage cylinder through the cyclone, the outer wall of the central body and the wall surface of the premixing passage cylinder form an annular premixing passage, a gas fuel injection device inserted into the outer wall of the central body is arranged in the front passage, the front end surface of the central body is provided with a ring groove, and the ring groove is communicated with the gas fuel injection device; the rear end face of the central body cavity is provided with a plurality of inclined small holes which are distributed circumferentially, and the inclined small holes gradually incline from front to back in the direction away from the central line, so that the tempering prevention purpose is achieved.

Description

Combined nozzle device for preventing backfire

Technical Field

The application relates to a backfire preventing technology of a low-pollution combustion chamber of a gas turbine, in particular to a combined nozzle device for preventing backfire.

Background

With the emphasis of environmental protection, the world has increasingly stringent requirements for gas turbine combustor emission standards, generally requiring gas turbines to be at 50% and above load range, and combustor emissions can be maintained at lower levels while maintaining higher combustion efficiency. Pollutants emitted from the combustion chamber mainly include nitrogen oxides, carbon monoxide and unburned hydrocarbons, wherein nitrogen oxides NOx are important indicators of pollutant emission, and lean premixed combustion technology is widely adopted for achieving the purpose of low NOx emission.

Lean premixed combustion aims to control the main combustion zone temperature within a narrow temperature range of 1670K-1900K, but only the total fuel/air equivalence ratio is controlled and is not equal to the target of low NOx. Because NOx emissions are highly sensitive to combustion temperatures, it is ensured that there are no localized high fuel concentration zone points in the combustible mixture, i.e., localized fuel/air equivalence ratios very close to average fuel concentration values. Thus, achieving a relatively uniform pre-mixing of fuel and air in a relatively short period of time is one of the technical challenges faced in dry low emission combustion design processes.

The premixing combustion technology mostly adopts a rotational flow mixing technology to realize good mixing of fuel and oxidant, if the structure of the rotational flow field in the premixing channel is not good, tempering is extremely easy to cause, the problem of ablation of the premixing section is caused, and the operation safety of the whole machine is seriously threatened. In order to solve the problem, a great deal of researches and experiments are carried out on the design of the cyclone in engineering, and the stronger the cyclone is, the better the blending uniformity of fuel and air is, but the problems of easy occurrence of air flow adhesion, easy occurrence of backfire ablation and the like are generally considered, so that in order to solve the problem that the low-emission combustion chamber is extremely easy to be backfire in a premixed gas environment, a nozzle device which has good blending performance and can solve the backfire ablation problem is designed to become a key technology of the low-emission combustion chamber.

The application relates to a backfire preventing technology of a low-pollution combustion chamber of a gas turbine, in particular to a combined nozzle device for preventing backfire, which forms reasonable airflow velocity distribution in a premixing channel, namely improves the airflow velocity at the inner hub side, avoids local backflow near the downstream of the inner hub of a cyclone, and solves the backfire ablation problem; meanwhile, a blowing small hole is formed in the end part of the nozzle to lift flame in a backflow area, so that ablation of the nozzle head is further prevented; and meanwhile, the fuel and the air form a relatively uniform mixture after passing through the cyclone device.

In the prior art, the design forms of the nozzle device are various, but most of the nozzle devices are designed independently of the cyclone device and the nozzle, so that the technical integration cannot be well performed; the cyclone device mainly adopts a single-stage cyclone, and performs a great deal of research and design on the modeling of the cyclone blade, such as a curved blade, a spiral blade, an inclined blade and the like, and has complex shape of a large number of blades, large processing difficulty and large adjustment difficulty.

Currently, flashback is a key issue in low emission combustor design, and the commonly employed anti-flashback techniques are to control swirl strength, local flow acceleration, control the initial temperature of the air and fuel mixture, and the degree of pulsation of the equivalence ratio. The swirl strength is controlled mainly by applying certain interference to the rotating main air flow, such as introducing a swirl-free slot circulation flow in the center of the cyclone, which can cause poor mixing uniformity of air and fuel and be unfavorable for low emission performance; the local flow acceleration is mainly realized by gradually reducing the cross-sectional area of the premixing channel so as to form an airflow acceleration effect, and the single implementation effect of the measure is not obvious; the control of the initial temperature and the pulsation level of the equivalence ratio of the air and the fuel mixture requires the matching of the overall parameters of the gas turbine, and should not be a dependent tempering prevention measure in the design stage of the low-emission combustion chamber.

The existing nozzle device for the low-emission combustion chamber has the defects that the swirl device is independently designed, the vane type design and the structural design are complex and various, and the problems of mixing performance, tempering and the like can be solved at the same time by partially combining the nozzle device, but the problems still exist in the aspects of engineering design, engineering implementation, optimization adjustment and the like.

1) The currently commonly adopted cyclone device is a single-stage cyclone blade, when the cyclone number is large and the cyclone is strong, the tangential component speed of the airflow is increased, the deflection angle of the blade is large, and the inner hub side is easy to cause airflow blockage due to the fact that the inner hub side and the outer hub side are fixed, the airflow speed is too low, the phenomenon of local backflow on the inner wall surface side of the central body is easy to occur, and the device is an important risk point for inducing main flow tempering;

2) The centerbody structure in the low emission combustor has the effect of stabilizing the flame, but the flame tends to adhere to the centerbody end face, causing overheating and even ablation.

Disclosure of Invention

In order to solve the above problems, the present application provides a combination nozzle device for preventing flashback, comprising:

a cyclone, a premixing passage cylinder, a central body with a cavity; the central body is arranged in the premixing channel cylinder through the cyclone, the outer wall of the central body and the wall surface of the premixing channel cylinder form an annular premixing channel, and the cyclone divides the premixing channel into a front channel and a rear channel;

the front channel is internally provided with a gas fuel injection device inserted into the outer wall of the central body, the central body is provided with a cavity, the front end of the cavity is open, a ring groove is arranged between the edge of the opening and the edge of the front end face of the central body, and the ring groove is communicated with one end of the gas fuel injection device inserted into the outer wall of the central body; the rear end of the cavity is provided with a plurality of inclined small holes which are distributed circumferentially, and the inclined small holes gradually incline from front to back to a direction far away from the central line.

Preferably, the cyclone is composed of an inner hub, an intermediate hub, an outer hub, and inner blades arranged between the inner hub and the intermediate hub; an outer swirl vane is arranged between the middle hub and the outer hub, the inner hub is connected with the central body, and the outer hub is connected with the premixing channel cylinder.

Preferably, the gaseous fuel injection means consists of a fuel inlet channel and a fuel boom. The gas fuel injection device is provided with fuel injection holes for spraying the fuel in the annular groove on the premixing channel, wherein the injection holes comprise small fuel injection holes close to the axis and large fuel injection holes far away from the axis, the outlet area ratio of the large fuel injection holes to the small fuel injection holes is larger than 1, the gas fuel injection device is used for fuel injection and helping to form initial distribution of the fuel in space, excellent initial field is provided for mixing in the premixing channel, and good mixing uniformity is helped to be obtained at the outlet of the premixing channel.

Preferably, the premix passage cartridge comprises a front premix passage inlet wall and a rear premix passage outlet wall, the premix passage inlet wall and the rear premix passage outlet wall being connected by a swirler.

Preferably, the inclined small holes comprise an inner ring hole and an outer ring hole which are circumferentially distributed, and the two inclined small holes with different inclined angles form a cooling air film and lift flame to prevent the nozzle head from being ablated.

Preferably, the included angle between the inner ring hole and the central line is 20-30 degrees, and the included angle between the outer ring hole and the central line is increased by 5-10 degrees in the radial direction compared with the included angle between the inner ring hole and the central line.

Preferably, the inner rotating blades and the outer rotating blades on the cyclone are both axial rotational flows, the difference of rotational flow numbers of the inner rotating blades and the outer rotating blades is not more than 0.2, the blades of the inner rotating blades and the outer rotating blades are distributed in a staggered manner, and the mixture of air and fuel is caused to generate rotational flows through the inner rotating blades and the outer rotating blades on the cyclone, so that the optimal air flow speed distribution for preventing backfire is obtained. The middle hub divides the cyclone into an inner stage and an outer stage, so that the inner hub diameter/the outer hub diameter of the inner-outer stage cyclone blades is not smaller than 0.5, and when the cyclone strength is large, even if the deflection angle of the blades is large, enough airflow flowing space is still reserved at the position close to the inner hub, so that the airflow speed of the inner hub side is improved, the occurrence of low-speed area even partial backflow is avoided, and the purpose of tempering prevention is achieved.

Preferably, the distance between the front end surface of the premixing passage cylinder and the gas fuel injection device is not less than 5mm.

Preferably, the outlet wall of the premixing passage gradually converges from front to back, and the included angle between the bus of the outlet wall of the premixing passage and the axis of the central body is 0-20 degrees, which is helpful for accelerating air and fuel flow and reducing backfire risk. .

Preferably, the gas fuel injection means has a plurality of gas fuel injection means uniformly distributed along the circumference of the central body.

The advantages of the application include: the application relates to a combined nozzle device capable of preventing backfire and nozzle ablation and realizing air/fuel premixing, wherein the fuel and the air realize the change of downstream speed distribution through a cyclone, obtain the air flow speed distribution favorable for backfire prevention, and effectively solve the problem of local backflow at the downstream of the cyclone; the fuel injection device and the cyclone are combined, so that optimal mixing uniformity can be obtained, and low emission performance is realized; and the inclined small holes of the nozzle head effectively prevent the nozzle head from being ablated. The combined nozzle device is relatively simple in structure, low in technical risk and meets engineering requirements. The device can realize the following steps:

1. injecting fuel into the premixing passage through two rows of spray holes with different apertures on the fuel spray rod, and forming uniform initial distribution in space;

2. the mixture of air and fuel is caused to generate rotational flow through the inner and outer different rotational flow blades on the cyclone, so that the optimal air flow velocity distribution for preventing backfire is obtained;

3. by the accelerated blending of the swirlers, the mixture of air and fuel is thoroughly blended within the premix passage and optimum blend uniformity is achieved at the premix passage outlet.

Drawings

FIG. 1 is a schematic view of a combined nozzle apparatus for preventing flashback in accordance with a preferred embodiment of the application;

FIG. 2 is a schematic illustration of a fuel boom according to a preferred embodiment of the present application;

FIG. 3 is a schematic view of a cyclone of a preferred embodiment of the present application;

FIG. 4 is a schematic diagram of a center body of a preferred embodiment of the present application;

FIG. 5 is a perspective view of a combined nozzle device for preventing flashback in accordance with a preferred embodiment of the application;

fig. 6 shows a conventional single stage cyclone.

Detailed Description

In order to make the objects, technical solutions and advantages of the present application become more apparent, the technical solutions in the embodiments of the present application will be described in more detail with reference to the accompanying drawings in the embodiments of the present application. In the drawings, the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The described embodiments are some, but not all, embodiments of the application. The embodiments described below by referring to the drawings are exemplary and intended to illustrate the present application and should not be construed as limiting the application. All other embodiments, based on the embodiments of the application, which are apparent to those of ordinary skill in the art without inventive faculty, are intended to be within the scope of the application. Embodiments of the present application will be described in detail below with reference to the accompanying drawings.

The gas fuel injection device 1, the swirler 2 and the premixing passage a are arranged together to form a combined nozzle device, wherein the gas fuel injection device 1 is arranged in front of the swirler 2 through welding, the premixing passage a consists of a premixing passage inlet wall 3-1, a premixing passage outlet wall 3-2 and an outer wall periphery of a central body 4, the premixing passage inlet wall 3-1 is arranged in front of the swirler 2, and the premixing passage outlet wall 3-2 and the central body 4 are arranged behind the swirler 2. The main flow air enters from A, the fuel enters from B, and the clean air enters from C.

The gas fuel injection device 1 is fixed by welding through a fuel inlet groove 1-1 and a fuel spray rod 1-2, and fuel enters from B. Wherein the fuel boom 1-2 includes two rows of fuel injection holes 1-2a, 1-2b for fuel injection and forming an initial distribution of fuel in space.

The cyclone 2 is formed by an inner hub 2-1, an intermediate hub 2-2, an outer hub 2-3, inner rotary blades 2-4 and outer rotary blades 2-5 which are added into a whole machine. The inner rotor blades 2-4 are positioned between the inner hub 2-1 and the intermediate hub 2-2, the blade root is connected with the inner hub 2-1, and the blade tip is connected with the intermediate hub 2-2. The outer rotary blades 2-5 are positioned on the middle hub 2-2 and the outer hub 2-3, blade roots are connected with the middle hub 2-2, and blade tips are connected with the outer hub 2-3. The inner and outer two-stage swirl vanes are used for assisting air and fuel to mix and form swirl, and the optimal airflow velocity distribution is obtained at the outlet of the premixing passage a.

The premixing passage a is formed by encircling a premixing passage inlet wall 3-1, a premixing passage outlet wall 3-2 and an outer wall of the central body 4, wherein the premixing passage inlet wall 3-1 is used for guiding air and fuel to enter the premixing passage. The premix passage outlet wall 3-2 is in a contracted form for accelerating the air and fuel streams. The central body 4 comprises two circles of inclined small holes 3-3a and 3-3b with different angles, which are used for forming a cooling air film on the end face of the central body 4 and lifting flame so as to prevent the nozzle head from being ablated.

In some alternative embodiments, the fuel rods 1-2 on the gaseous fuel injection 1 are circumferentially uniformly distributed.

In some alternative embodiments, the area ratio of the two rows of fuel injection holes 1-2a, 1-2b in the fuel injection boom 1-2 on the gaseous fuel injection 1 is greater than 1 to ensure that the penetration depth of the outer ring of injection holes is greater than that of the inner ring of injection holes, thereby making the fuel injected from the two rows of injection holes more spatially uniform.

In some alternative embodiments, the inner cyclone blades 2-4 and the outer cyclone blades 2-5 on the cyclone 2 are both axial cyclone, the cyclone numbers of the two-stage cyclone blades are similar, the difference of the cyclone numbers is not more than 0.2, and the phenomenon that airflow separation is formed in a premixing channel due to overlarge airflow tangential speed difference of the inner cyclone blade and the outer cyclone blade, so that airflow streamline is not smooth and tempering prevention is not facilitated is avoided. The thickness and the number of the blades are determined by the rotational flow number, the blades are required to be distributed in a staggered manner, and the staggered distribution of the blades can help mixing air and fuel, so that the mixing is more uniform, and the emission reduction is facilitated.

In some alternative embodiments, the front edge surface of the premixing passage inlet wall 3-1 on the premixing passage a exceeds the fuel spray bar 1-2 by not less than 5mm, so that fuel is prevented from falling out of the premixing passage a, and other non-premixing areas are caused to generate fuel, and the combustion efficiency is reduced, and the non-combustion areas are caused to burn.

In some alternative embodiments, the angle between the premixing passage outlet wall 3-2 and the center line on the premixing passage a is between 0 ° and 20 °, and an excessive angle can cause separation of the air flow at the premixing passage outlet, and the flame is easy to cause resident combustion at the separation, so that ablation is initiated.

In some alternative embodiments, the number of the inclined small holes 3-3a and 3-3b on the central body 4 on the premixing channel a is 8-12, the included angle between the inner ring hole 3-3b and the central line is 20-30 degrees, the included angle between the outer ring hole 3-3a and the central line is 5-10 degrees larger than the included angle between the inner ring hole 3-3b and the central line, the included angle between the inner ring hole is smaller, so that the flame can be better blown off the end face of the central body 4, the included angle between the outer ring hole is slightly larger, firstly, the inner ring hole bears most of the function of blowing off the flame, secondly, the included angle is larger, the forming of a cooling air film on the end face is facilitated, and the nozzle is further protected from being ablated by high-temperature fuel gas.

The foregoing is merely illustrative of the present application, and the present application is not limited thereto, and any changes or substitutions easily contemplated by those skilled in the art within the scope of the present application should be included in the present application. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.

Claims

1. A combination nozzle device for tempering prevention, comprising:

a cyclone (2), a premix passage cylinder (3), a central body (4) having a cavity (c); the central body (4) is arranged in the premixing passage cylinder (3) through the cyclone (2), the outer wall of the central body (4) and the wall surface of the premixing passage cylinder (3) form an annular premixing passage (a), and the cyclone (2) divides the premixing passage (a) into a front passage and a rear passage;

the method is characterized in that: the front channel is internally provided with a gas fuel injection device (1) inserted into the outer wall of the central body (4), the central body (4) is provided with a cavity (c), the front end of the cavity (c) is open, a ring groove (b) is arranged between the edge of the opening and the edge of the front end face of the central body (4), and the ring groove (b) is communicated with one end of the gas fuel injection device (1) inserted into the outer wall of the central body (4); the rear end of the cavity (c) is provided with a plurality of inclined small holes which are distributed circumferentially, and the inclined small holes gradually incline from front to back to the direction far away from the central line;

the gas fuel injection device (1) is provided with fuel spray holes for spraying the fuel in the annular groove (b) on the premixing channel (a), wherein the spray holes comprise small fuel spray holes (1-2 a) close to the axis and large fuel spray holes (1-2 b) far away from the axis, and the outlet area ratio of the large fuel spray holes (1-2 b) to the small fuel spray holes (1-2 a) is larger than 1.

2. A combined nozzle device for preventing flashback according to claim 1, characterized in that the swirler (2) is formed by an inner hub (2-1), an intermediate hub (2-2), an outer hub (2-3), an inner hub (2-1) and an intermediate hub (2-2) with inner rotating vanes (2-4) therebetween; an outer swirl vane (2-5) is arranged between the middle hub (2-2) and the outer hub (2-3), the inner hub (2-1) is connected with the central body (4), and the outer hub (2-3) is connected with the premixing channel barrel (3).

3. A combined nozzle device for preventing flashback as claimed in claim 1, characterized in that the premix channel barrel (3) comprises a front end premix channel inlet wall (3-1) and a rear end premix channel outlet wall (3-2), the premix channel inlet wall (3-1) and the rear end premix channel outlet wall (3-2) being connected by means of a swirler (2).

4. A combined nozzle device for preventing backfire according to claim 1, wherein said inclined apertures comprise inner ring holes (3-3 b) and outer ring holes (3-3 a) distributed circumferentially.

5. A combined nozzle device for preventing backfire according to claim 4, wherein the angle between the inner ring hole (3-3 b) and the center line is 20 ° to 30 °, and the angle between the outer ring hole (3-3 a) and the center line is increased by 5 ° to 10 ° radially compared to the angle between the inner ring hole (3-3 b) and the center line.

6. The combined nozzle device for preventing backfire according to claim 2, wherein the inner rotating blades (2-4) and the outer rotating blades (2-5) on the cyclone (2) are both axially rotating, the difference of the rotational flow numbers of the inner rotating blades (2-4) and the outer rotating blades (2-5) is not more than 0.2, and the blades of the inner rotating blades (2-4) and the outer rotating blades (2-5) are staggered.

7. A combined nozzle device for preventing flashback as claimed in claim 1, characterized in that the distance between the front end face of the premixing passage tube (3) and the gaseous fuel injection device (1) is not less than 5mm.

8. A combined nozzle device for preventing flashback as claimed in claim 3, characterized in that the premixing passage outlet wall (3-2) gradually converges from front to back, and that the angle between the generatrix of the premixing passage outlet wall (3-2) and the axis of the central body (4) is 0 ° to 20 °.

9. A combined nozzle device for preventing flashback as claimed in claim 1, characterized in that the gas fuel injection means (1) have a plurality of gas fuel injection means uniformly distributed along the circumference of the central body (4).