CN118705647B - A double-layer structured duty fuel nozzle, burner and operation method - Google Patents

Abstract

The present invention belongs to the technical field of gas turbine burners, and discloses a double-layered duty fuel nozzle, a burner and an operation method. The duty fuel nozzle includes a double-layer duty fuel flow chamber and a duty fuel spray hole connected in sequence, and the double-layer duty fuel flow chamber includes a central duty fuel channel, an inner duty air channel, an outer duty fuel channel and an outer duty air channel from the center to the outside in sequence; the central duty fuel channel is connected to the central duty fuel spray hole, and an inner duty swirler is provided on the front side of the inner duty air channel; an outer duty swirler and an outer duty fuel spray hole are provided on the front side of the outer duty air channel; the outer duty fuel spray hole is provided on the swirl blade of the outer duty swirler and conducts and connects the outer duty fuel channel and the outer duty air channel, or is provided at the front end of the outer duty fuel channel. The present invention can solve the problem of easy explosion during ignition of hydrogen-containing fuel, and has stable combustion, avoids backfire, and can reduce NO _x emissions.

Description

A double-layer structured duty fuel nozzle, burner and operation method

Technical Field

The invention belongs to the technical field of burners, and in particular relates to a double-layer structured on-duty fuel nozzle, a burner and an operating method.

Background Art

Due to the high price of natural gas, the revenue of domestic gas turbine power plants is mostly lower than expected, or even loss-making. In order to reduce fuel costs, it has gradually become a trend to use petrochemical by-product gas or IGCC synthesis gas as gas turbine fuel for power generation. However, the main design fuel for gas turbines is natural gas, especially the burners using premixed combustion technology, which have extremely strict requirements on the hydrogen ratio, generally requiring the hydrogen ratio to be within 2% (volume fraction). Therefore, for petrochemical by-product gas with a high hydrogen content, there are great limitations in using this type of gas turbine for combustion. For example, Zhejiang Petrochemical modified the fuel system of three Siemens SGT-2000Es so that they can burn fuel containing 0-25% hydrogen, but during ignition and low-load conditions, due to deflagration and flashback problems, natural gas fuel still needs to be used completely.

Therefore, there is an urgent need to improve the existing burners to solve the problem that they are unable to ignite and burn at low loads with fuels containing more than 1% hydrogen.

Summary of the invention

The present invention aims to solve the problem that the existing burner cannot burn fuel with a hydrogen content of more than 1% for ignition and low-load combustion, and provides a double-layer structure of a duty fuel nozzle, a burner and an operating method, which can be used for direct ignition and start-up of hydrogen-containing fuel (hydrogen gas volume fraction <25%) of a gas turbine, and switch to premixed combustion after pushing to a certain load. At the same time, under high-load conditions, by shutting down the central duty fuel, the duty fuel amount is reduced, thereby reducing _NOx emissions and achieving low emission targets.

In order to achieve the above technical objectives, the present invention adopts the following technical solutions:

A double-layer duty fuel nozzle, comprising a double-layer duty fuel flow chamber and a duty fuel spray hole connected in sequence; the double-layer duty fuel flow chamber comprises a central duty fuel channel, an inner duty air channel, an outer duty fuel channel and an outer duty air channel in sequence from the center to the outside; the front side of the central duty fuel channel is connected to the central duty fuel spray hole, the front side of the inner duty air channel is provided with an inner duty swirler, and the inner duty swirler is provided between the central duty fuel channel and the outer duty fuel channel;

The front side of the outer duty air passage is provided with an outer duty swirler and an outer duty fuel spray hole;

The outer layer duty fuel spray hole is arranged on the swirl blade of the outer layer duty swirler, the front end side wall of the outer layer duty fuel channel is connected to the outer layer duty fuel spray hole, and is connected to the outer layer duty air channel through the outer layer duty fuel spray hole, or,

The outer duty fuel injection hole is arranged at the front end of the outer duty fuel channel, and the fuel in the outer duty fuel channel is mixed with the air sprayed from the outer duty air channel at the front end of the outer duty swirler.

Furthermore, the inner layer on-duty cyclone adopts spirally bent blades.

Furthermore, the swirl number of the inner layer duty cyclone is >1.3.

Furthermore, the outer layer duty cyclone adopts straight blades with leaf shapes.

Furthermore, the swirl number of the outer layer duty cyclone is <0.8.

Furthermore, an igniter is installed in the middle of the swirl blades of the inner layer duty swirler toward the front.

At the same time, the present invention provides a burner, comprising a service fuel nozzle with a double-layer structure as described in any of the above items, and also comprising a nozzle shell, wherein the service fuel nozzle is arranged at the center of the nozzle shell, and a premixing fuel nozzle is arranged at the periphery of the service fuel nozzle.

Further, the premix fuel nozzle comprises a premix fuel flow cavity and a premix fuel spray hole which are connected in sequence;

The premixed fuel flow cavity includes a premixed fuel channel and a premixed air channel from inside to outside. A premixed air swirler is arranged in the premixed air channel. The premixed air swirler is obliquely arranged perpendicular to the flow axis of the premixed air channel. An oblique hole is opened on the premixed air swirler for connecting the premixed fuel channel with the premixed air channel.

In addition, the present invention also provides a burner combustion operation method, which is implemented using the burner as described above, wherein the burner includes three combustion modes, namely: central duty fuel combustion, outer duty fuel diffusion combustion and premixed fuel premixed combustion;

According to the operating load, the process of the burner from initial ignition to full load operation is as follows:

Stage 1: Unit ignition:

Only central duty fuel is used for combustion;

The inner layer of central duty fuel is sprayed in from the central duty fuel spray hole, and the igniter facing the front side of the swirl blade fixed in the middle of the inner layer of duty swirl device ignites, thereby igniting the inner layer of central duty fuel;

Stage 2: Unit operation from startup to 30% load:

The outer duty fuel diffusion combustion is used as the main method, and the central duty fuel combustion is used as the auxiliary method;

The fuel enters the combustion chamber through the outer duty fuel nozzles of the outer duty swirler, forming a diffusion flame; at the same time, the inner central duty fuel still maintains the set proportion of combustion;

Stage 3: The unit operates between 30% and 50% load:

Simultaneous operation of outer duty fuel diffusion combustion, central duty fuel combustion and premixed fuel premixed combustion;

As a supplement to the second stage combustion method, the premixed air is fully mixed with the premixed fuel sprayed from the oblique holes of the premixed air swirler and then injected into the combustion chamber for combustion. At this time, the inner layer of central duty fuel, the outer layer of duty fuel and the premixed fuel exist and burn at the same time;

Stage 4: The unit operates between 50% load and 100% load:

The premixed fuel is mainly used for premixed combustion, and the outer layer duty fuel is used for diffusion combustion as a supplement;

Premixed fuel and premixed combustion are mainly adopted. At the same time, the preset proportion of outer duty fuel is maintained for combustion, and the inner central duty fuel channel is closed, while the inner duty air channel is kept open.

Furthermore, when the unit is running from startup to 30% load, the volume fraction of the central duty fuel in the inner layer is maintained at 15-20%;

When the unit operates between 50% load and 100% load, the volume fraction of the outer duty fuel is maintained at 5%-10%.

Compared with the prior art, the beneficial effects of the present invention are:

(1) The duty fuel nozzle of the present invention is designed as a double-layer structure, including a double-layer duty fuel and a double-layer duty air channel, and is respectively provided with an inner layer swirler and an outer layer swirler. During ignition, only a small amount of central duty fuel is supplied, which solves the problem that hydrogen-containing fuel is easy to deflagrate when directly ignited and started. At the same time, the design of the double-layer duty fuel channel and the double-layer duty air channel can make the duty fuel distribution more uniform, thereby increasing the stability of combustion;

(2) The inner duty cyclone adopts spirally bent blades with a swirl number of >1.3 and a strong swirl intensity, which can stabilize the flame when igniting a small amount of fuel. Due to the strong swirl number of the inner duty cyclone, only a small amount of central duty fuel is supplied during ignition. With a small amount of central duty fuel, the flame can be stabilized and ignited successfully. At the same time, due to the existence of the inner duty cyclone, the heat load of the unit during ignition can be effectively reduced, preventing the occurrence of deflagration and avoiding the damage of the deflagration to the unit.

(3) The outer cyclone uses straight blades with a swirl number of <0.8, which can increase the axial flow velocity of the outer duty air. Before the premixed fuel is cut in at low load, the outer duty fuel is used to promote the increase of the operating load, which can effectively avoid flashback;

(4) Under high load conditions, a small amount of outer duty fuel is used to stabilize the flame while closing the inner central duty fuel, which can effectively reduce the temperature of the central combustion area of the duty fuel nozzle and further reduce the _NOx emissions of the unit.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a schematic diagram of the internal structure of a burner with a double-layer structured fuel nozzle in Example 1 of the present invention;

FIG2 is a schematic diagram of the three-dimensional structure of a burner with a double-layer structured fuel nozzle in Example 1 of the present invention;

FIG3 is a schematic diagram of the front (front side) structure of a burner with a double-layer structured fuel nozzle in Example 1 of the present invention;

FIG4 is a schematic diagram of the back side (rear side) structure of a burner with a duty fuel nozzle having a double-layer structure in Example 1 of the present invention;

FIG5 is a schematic diagram of the assembly structure of the inner layer duty cyclone and the outer layer duty cyclone in Example 1 of the present invention;

FIG6 is a schematic diagram of the straight blade structure of the outer layer on-duty cyclone in Example 1 of the present invention;

FIG7 is a schematic diagram of the structure of the spirally bent blades of the inner layer on-duty cyclone in Example 1 of the present invention;

FIG8 is a schematic diagram of the structure of the fuel and air flow paths of the burner of Example 1 of the present invention;

FIG9 is a schematic diagram of the combustion process of the burner from startup to full load operation according to Example 1 of the present invention;

FIG10 is a schematic diagram of the three-dimensional structure of a burner with a double-layer structure of a duty fuel nozzle in Example 2 of the present invention;

Description of the markings in the figure:

1-nozzle housing; 2-premixed air swirler; 3-outer duty swirler; 4-outer duty fuel nozzle; 5-premixed air channel; 6-inner duty swirler; 7-central duty fuel nozzle; 8-central duty fuel channel; 9-inner duty air channel; 10-outer duty fuel channel; 11-outer duty air channel; 12-premixed fuel channel.

DETAILED DESCRIPTION

The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

In the description of the present invention, it is necessary to understand that the terms "coaxial", "bottom", "one end", "top", "middle", "the other end", "upper", "one side", "top", "inside", "front", "center", "both ends" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

In the present invention, unless otherwise clearly stipulated and limited, the terms such as "installation", "setting", "connection", "fixation" and "screw-on" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral one; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be the internal connection of two elements or the interaction relationship between two elements. Unless otherwise clearly defined, ordinary technicians in this field can understand the specific meanings of the above terms in the present invention according to the specific circumstances.

Example 1

1 to 7 , an embodiment of the present invention provides a burner, including a nozzle housing 1 , a service fuel nozzle with a double-layer structure is arranged at the center of the nozzle housing 1 , and a premixing fuel nozzle is arranged at the periphery of the service fuel nozzle.

The duty fuel nozzle includes a double-layer duty fuel circulation cavity and a duty fuel spray hole which are connected in sequence. The double-layer duty fuel circulation cavity includes a central duty fuel channel 8, an inner duty air channel 9, an outer duty fuel channel 10 and an outer duty air channel 11 from the center to the outside.

The front side of the central duty fuel channel 8 is connected to the central duty fuel injection hole 7 , and the front side of the inner duty air channel 9 is provided with an inner duty swirler 6 , and the inner duty swirler 6 is arranged between the central duty fuel channel 8 and the outer duty fuel channel 10 .

An outer layer duty swirler 3 and an outer layer duty fuel injection hole 4 are arranged at the front side of the outer layer duty air passage 11 .

In an embodiment of the present invention, the outer layer duty fuel spray hole 4 is arranged on the swirl blade of the outer layer duty swirler 3, and the front end side wall of the outer layer duty fuel channel 10 is connected to the outer layer duty fuel spray hole 4, and is connected to the outer layer duty air channel 11 through the outer layer duty fuel spray hole 4; specifically, the outer layer duty fuel spray hole 4 is a bent through hole that penetrates the side wall and the front wall of the swirl blade of the outer layer duty swirler 3 (see Figure 6).

The premix fuel nozzle includes a premix fuel flow cavity and a premix fuel spray hole which are connected in sequence. The premix fuel flow cavity includes a premix fuel channel 12 and a premix air channel 5 from the inside to the outside. A premix air swirler 2 is arranged in the premix air channel 5. The premix air swirler 2 is obliquely arranged perpendicular to the flow axis of the premix air channel 5. An oblique hole is opened on the premix air swirler 2 for connecting the premix fuel channel 12 with the premix air channel 5.

Specifically, in the embodiment of the present invention, referring to FIG. 5 and FIG. 7, the swirler blades of the inner duty swirler 6 are spirally bent blades, the swirl number is greater than 1.3, the swirl intensity is relatively strong, and the flame can be stabilized when a small amount of fuel is ignited. The spirally bent blades of the inner duty swirler 6 surround the periphery of the central duty fuel nozzle 7, and the central duty fuel nozzle 7 is connected to the central duty fuel channel 8, which is used to spray the central duty fuel for ignition when the engine is started. Since the swirl number of the inner duty swirler 6 is large and the swirl intensity is relatively strong, when a small amount of air passes through the inner duty swirler 6 and a small amount of central duty fuel passes through the central duty fuel nozzle 7, the two are contacted and mixed and ignition is started, and ignition can be successful and stable combustion can be achieved, overcoming the defect that hydrogen-containing fuel is easy to explode when directly ignited and started.

As shown in Figures 5 and 6, the swirler blades of the outer duty swirler 3 are straight blades with a blade shape, and the swirl number is <0.8, so as to increase the axial velocity of the outer duty air and avoid backfire. The nozzle end of the outer duty fuel nozzle 4 is located at the front of the fluid channel between two adjacent straight blades of the outer duty swirler 3, which is used to spray the outer duty fuel for combustion under low load conditions and push the unit to 30% load.

An igniter is installed in the middle of the swirl blades of the inner layer of the duty swirler 6 of the duty fuel nozzle toward the front (front side). During ignition, the central duty fuel is introduced from the central duty fuel channel 8, the igniter is started, and the ignition is successful.

Since only air passes through the swirler blade channel of the inner duty swirler 6, the igniter structure can be effectively cooled to prevent the igniter from burning out. At the same time, due to the setting of the inner duty swirler 6, the unit can be directly ignited when the fuel contains hydrogen, avoiding the damage to the unit caused by deflagration, so that the double-layer structure of the duty fuel nozzle and its burner of the embodiment of the present invention can be suitable for hydrogen-containing fuel with a hydrogen volume fraction of <25% and a low calorific value of >25MJ/ ^Nm3 .

Under high load conditions, most of the fuel enters the subsequent premixing channel from the premixing fuel nozzle to form premixed combustion. At this time, the outer layer of duty fuel is still retained, maintaining a volume fraction of 5%-10% of the outer layer of duty fuel to stabilize the premixed flame. At the same time, the inner layer of the central duty fuel is closed, but the inner layer of the duty swirler 6 still has air passing through it to reduce the flame temperature in the center area of the duty fuel nozzle to reduce NO _x emissions.

The fuel and air flow paths of the burner of the embodiment of the present invention are shown in FIG8 , wherein:

The central duty fuel and the outer duty fuel enter the duty fuel nozzle from the central duty fuel channel 8 and the outer duty fuel channel 10 respectively. Then, the central duty fuel passes through the central duty fuel channel 8 and is sprayed from the central duty fuel spray hole 7. The outer duty fuel passes through the outer duty fuel channel 10 and is sprayed from the outer duty fuel spray hole 4.

The outer duty air enters the outer duty cyclone 3 through the outer duty air channel 11; at the outer duty cyclone 3, since the swirl number of the outer duty cyclone 3 is relatively low, a relatively high axial velocity can still be maintained;

The inner duty air passes through the inner duty air channel 9 and enters the inner duty cyclone 6; at the inner duty cyclone 6, the circumferential velocity of the inner duty air secondary combustion air increases, and the axial velocity decreases;

The outer duty fuel sprayed from the outer duty fuel spray hole 4 is mixed with the outer duty air while burning. At this time, since the outer duty fuel and the outer duty air have a certain axial velocity, the ablation of the duty fuel nozzle caused by fuel flashback can be effectively avoided;

The central duty fuel sprayed from the central duty fuel nozzle 7 is mixed with the inner duty air while burning. At this time, since both the central duty fuel and the inner duty air have a certain axial velocity, the ablation of the duty fuel nozzle caused by fuel backfire can be effectively avoided.

The embodiment of the present invention adopts a duty fuel nozzle with a double-layer structure design. Through the design of a double-layer duty fuel channel and a double-layer duty air channel, the duty fuel can be distributed more evenly, thereby increasing the stability of combustion.

The embodiment of the present invention also provides a combustion operation method of a burner. The burner of the embodiment of the present invention includes three combustion modes, namely: central duty fuel combustion, outer duty fuel diffusion combustion and premixed fuel premixed combustion. According to the operating load, combined with FIG8, the process of the burner of the embodiment of the present invention from initial ignition to full load operation is as follows:

Stage 1: Unit ignition:

The incoming air from the compressor enters the combustion chamber and enters the flame tube from the premixed air swirler 2, the outer duty swirler 3 and the inner duty swirler 6 respectively;

When the unit is ignited, only the central duty fuel is used for combustion; the inner layer of the central duty fuel is injected from the inner layer of the duty fuel injection nozzle 7, and the swirl blades fixed in the middle of the inner layer of the duty swirler 6 are ignited by the igniter facing the front, thereby igniting the inner layer of the central duty fuel;

Since the swirl number of the inner duty cyclone 6 is relatively strong, the flame can be stabilized and ignited successfully in the case of a small amount of central duty fuel; at the same time, due to the existence of the inner duty cyclone 6, the ignition can be successfully carried out in the case of a small amount of central duty fuel by relying on the igniter arranged in the middle of the swirl blades of the inner duty cyclone 6 facing the front. The heat load of the unit during ignition is effectively reduced, and the occurrence of deflagration is prevented, which avoids the damage to the unit caused by deflagration.

Stage 2: Unit operation from startup to 30% load:

The outer duty fuel diffusion combustion is mainly adopted, and the central duty fuel combustion is supplemented.

The fuel enters the combustion chamber through the outer duty fuel nozzle hole 4 of the outer duty swirler 3 to form a diffusion flame;

In this stage, the high-temperature flue gas generated by the combustion of the outer duty fuel mainly drives the engine speed and load to increase. Since the swirl number of the outer duty cyclone 3 is low and the axial velocity of the air is high, flashback can be avoided as the heat load increases;

At the same time, in order to ensure the stability of the flame in the combustion chamber, at this time, the inner layer of the central duty fuel still maintains a lower set proportion of combustion, such as: the volume fraction of the inner layer of the central duty fuel is maintained at 15-20%.

Stage 3: The unit operates between 30% and 50% load:

Simultaneous operation of outer duty fuel diffusion combustion, central duty fuel combustion and premixed fuel premixed combustion;

As a supplement to the combustion method in stage 2, the premixed air is fully mixed with the premixed fuel sprayed from the oblique holes of the premixed air swirler 2 and then injected into the combustion chamber for combustion. At this time, the inner layer of central duty fuel, the outer layer of duty fuel and the premixed fuel exist and burn at the same time;

The use of diffusion combustion and premixed combustion in parallel can effectively ensure combustion stability and improve combustion efficiency on the one hand, and reduce the emission of pollutants _NOX on the other hand.

Stage 4: The unit operates between 50% load and 100% load:

The premixed fuel is mainly used for premixed combustion, and the outer layer duty fuel is used for diffusion combustion as a supplement;

Premixed fuel premixed combustion is mainly adopted. At the same time, the preset proportion of outer duty fuel is maintained for combustion, and the inner central duty fuel channel is closed, and the inner duty air channel is kept open;

Before the premixed fuel enters the combustion chamber, the compressed air at the compressor outlet is fully mixed with the premixed fuel through the action of the obliquely arranged premixed air swirler 2, and then injected into the combustion chamber. The fuel can be quickly and fully burned in the combustion chamber, which can improve the combustion efficiency. At the same time, a small amount of outer duty fuel is used to stabilize the flame (such as maintaining the outer duty fuel with a volume fraction of 5%-10%). At this time, closing the inner central duty fuel channel 8 can reduce the temperature of the central combustion area and further reduce the _NOx emissions of the unit.

Example 2

The difference between the embodiment of the present invention and implementation 1 lies in the different locations of the outer duty fuel injection holes 4:

Specifically, referring to Figure 10, the outer duty fuel nozzle hole 4 is specifically located at the front end of the outer duty fuel channel 10. The fuel in the outer duty fuel channel 10 is directly sprayed out in a straight line through the outer duty fuel nozzle hole 4, and mixed with the air sprayed out of the outer duty air channel 11 in the combustion chamber at the front end of the outer duty swirler 3.

The remaining structures of the embodiment of the present invention and the process of the burner from initial ignition to full load operation are the same as those in Embodiment 1 and will not be described in detail here.

The above description is only an embodiment of the present invention and is not intended to limit the present invention. Any modification, equivalent replacement and improvement made within the application scope of the present invention shall be included in the protection scope of the present invention.

Claims (10)

1. The on-duty fuel nozzle with the double-layer structure is characterized by comprising a double-layer on-duty fuel circulation cavity and an on-duty fuel spray hole which are sequentially communicated; the double-layer duty fuel circulation cavity sequentially comprises a central duty fuel channel, an inner-layer duty air channel, an outer-layer duty fuel channel and an outer-layer duty air channel from the center to the outside; the front side of the central on-duty fuel channel is communicated with a central on-duty fuel spray hole, an inner-layer on-duty cyclone is arranged on the front side of the inner-layer on-duty air channel, and the inner-layer on-duty cyclone is arranged between the central on-duty fuel channel and the outer-layer on-duty fuel channel;

An outer-duty cyclone and an outer-duty fuel spray hole are arranged on the front side of the outer-duty air channel;

The outer-duty fuel spray holes are arranged on the swirl blades of the outer-duty swirler, the front end side wall of the outer-duty fuel channel is connected with the outer-duty fuel spray holes in a conducting mode and is communicated with the outer-duty air channel through the outer-duty fuel spray holes, or

The outer-duty fuel spray hole is arranged at the front end of the outer-duty fuel channel, and fuel in the outer-duty fuel channel and air sprayed out of the outer-duty air channel are mixed at the front end of the outer-duty cyclone.

2. The dual structure duty fuel nozzle of claim 1, wherein said inner duty swirler employs helical bend vanes.

3. The dual structure duty fuel nozzle of claim 2, wherein said inner duty swirler has a swirl number >1.3.

4. The dual duty fuel nozzle of claim 1, wherein said outer duty swirler employs straight vanes with a vane pattern.

5. The dual duty fuel nozzle of claim 4, wherein said outer duty swirler has a swirl number <0.8.

6. The dual-structure duty fuel nozzle of claim 1, wherein an igniter is mounted towards the front face in the middle of the swirl vanes of said inner-layer duty swirler.

7. A burner comprising the dual-layer duty fuel nozzle of any one of claims 1-6, further comprising a nozzle housing, wherein the duty fuel nozzle is disposed in the center of the nozzle housing, and wherein premix fuel nozzles are disposed on the periphery of the duty fuel nozzle.

8. The burner of claim 7 wherein the premix fuel nozzle comprises a premix fuel flow chamber and a premix fuel nozzle orifice in sequential communication;

The premixing fuel circulation cavity comprises a premixing fuel channel and a premixing air channel from inside to outside, a premixing air swirler is arranged in the premixing air channel and perpendicular to the circulation axis of the premixing air channel, and an inclined hole is formed in the premixing air swirler and used for communicating the premixing fuel channel with the premixing air channel.

9. A method of burner combustion operation using the burner of claim 8, wherein the burner comprises three combustion modes: the central duty fuel combustion, the outer duty fuel diffusion combustion and the premixed fuel premixed combustion;

according to the working condition operation load, the process from initial ignition to full load operation of the burner is specifically as follows:

stage one, ignition of a unit:

Only using central duty fuel for combustion;

The central duty fuel of the inner layer is sprayed from a central duty fuel spray hole, and an igniter which is fixed in the middle of a swirl blade of the inner layer duty swirler and faces to the front is ignited to ignite the central duty fuel of the inner layer;

Stage two, the unit is operated from starting to 30% load:

the outer-layer duty fuel diffusion combustion is adopted as a main part, and the central duty fuel combustion is adopted as an auxiliary part;

the fuel enters the combustion chamber through the outer-layer duty fuel spray holes of the outer-layer duty cyclone to form diffusion flame; meanwhile, the central duty fuel of the inner layer still maintains the set proportion combustion;

stage three, the unit operates between 30% -50% load:

the outer-layer duty fuel diffusion combustion, the central duty fuel combustion and the premixed fuel premixed combustion are adopted to run simultaneously;

As the supplement of the stage two combustion mode, the premixed air is fully mixed with the premixed fuel sprayed from the inclined holes of the premixed air cyclone and then injected into the combustion chamber for combustion, and at the moment, the central duty fuel of the inner layer, the outer duty fuel and the premixed fuel exist and combust simultaneously;

Stage four, the unit is operated between 50% load and 100% load:

Premixed combustion of premixed fuel is adopted as a main material, and diffusion combustion of outer-layer duty fuel is adopted as an auxiliary material;

The premixed combustion of the premixed fuel is adopted as a main part, and meanwhile, the combustion of the outer-layer duty fuel with a preset proportion is maintained, the central duty fuel channel of the inner layer is closed, and the opening of the air channel of the inner layer duty is maintained.

10. The method of claim 9, wherein the central on-duty fuel volume fraction of the inner layer is maintained at 15-20% from start-up to 30% load operation of the unit;

When the unit operates between 50% load and 100% load, the volume fraction of the outer-layer duty fuel is maintained to be 5% -10%.