CN107559882B - An axially graded low-pollution combustion chamber - Google Patents

Abstract

The invention relates to an axially graded low-pollution combustion chamber. The axially graded combustion technology is used to divide the combustion chamber into a duty class and a main combustion class. Both the duty class and the main combustion class adopt multiple premixed models to effectively control the duty The equivalence ratio between the combustion zone and the main combustion zone improves the degree of oil-gas mixing and reduces the pollution emission level of the combustion chamber under different working conditions, and the pre-mixing model adopts a reasonable structural design to prevent problems such as spontaneous combustion and tempering.

Description

An axially graded low-pollution combustion chamber

technical field

The invention belongs to the field of gas turbine combustors, and relates to an axially graded low-pollution combustor, in particular to an axially graded low-pollution combustor in which both the duty class and the main combustion stage adopt multi-point injection lean oil premixing and pre-evaporation.

Background technique

In recent years, due to the high power of a single gas turbine and the gas turbine unit participating in the combined cycle to achieve higher thermal efficiency of the entire system, the application of gas turbines in electric power, petrochemical, metallurgy and other fields has become more and more extensive. Gas turbines will produce a large amount of pollutants during work. The increasingly serious environmental problems have made the requirements for gas turbine pollution emissions more and more stringent. Under 15% O2 concentration, for natural gas fuel, NOx emissions are less than 25ppm, and CO emissions are less than For diesel fuel, NOx emissions are less than 65ppm, and CO emissions are less than 100ppm. Low-pollution combustion technology has become the development trend of advanced ground gas turbines, but the improvement of the overall performance of gas turbines puts forward higher requirements for the design of the main combustion chamber.

At present, the commonly used combustion pollutant control technologies for ground gas turbines mainly include "wet" low emission technology of spraying water/steam into the combustion chamber, "dry" low NOx DLN emission technology, catalytic combustion, etc. The "wet" low emission technology further reduces NOx emissions due to water injection and steam injection, which will have an impact on the cycle performance and component life of the gas turbine. At the same time, the emissions of carbon monoxide and unburned hydrocarbons have also begun to increase. At present, the most widely used and most developed is the "dry" low-NOx combustion technology, which is based on the formation mechanism of thermal NOx and reduces NOx emissions by controlling the flame temperature in the main combustion zone between 1670-1900K. Using the pre-mixing and pre-evaporation method, the fuel is mixed with air to form a uniform oil-air mixture before entering the combustion zone, and the combustion temperature is controlled by adjusting the oil-air ratio, thereby controlling the NOx emission level. The DLN combustor used by RR's RB211 industrial gas turbine includes 9 radially installed counter-flow single-tube combustors, each flame tube has a 2-stage combustor assembly, and the oil supply and gas supply between the two poles are independent. The purpose of staging is to maintain a high fuel-air ratio and reduce emissions under partial load; RR's Trent dry low-emission combustion chamber contains a series of lean-oil premixed fuel injection systems, which do not change the air distribution ratio under different operating conditions, while It is to adjust the distribution of fuel from one zone to another, so as to maintain a relatively constant combustion temperature to reduce the level of pollution emissions; GE's LM6000 gas turbine uses an annular DLN combustor, which is reduced by fuel staging and ultra-lean flame temperature Pollution emission, the ring includes 30 premixed burners, which work in the entire engine operating range, and the inner and outer rings have 15 and 30 premixed burners respectively, which can be adjusted to ensure that the combustion chamber is in a narrow temperature range Internal work; the low-emission combustors developed by PW mainly use radial staging, staged combustion, fuel premixing and pre-combustion to reduce pollution emission levels, such as E3 engine combustors, Vorbix combustors, FT8-2 gas turbine combustors, etc.

Relevant research has also been carried out on the combustion chamber of ground gas turbines in China. The patent 201610054669.8 of Nanjing University of Aeronautics and Astronautics invented a single-tube combustion chamber for ground gas turbines. flow device to strengthen the mixing of air and natural gas; Northwestern Polytechnical University's patent 201610016396.8 relates to a ground gas turbine combustion chamber structure and its hierarchical combustion organization mode. The duty-level combustion area uses a small flame tube with a converging section at the front. , The rear main combustion zone adopts a large flame tube with a flame stabilizer, the duty level forms a stable ignition source, and the main combustion level is pre-mixed to improve combustion efficiency.

It can be seen from the research status at home and abroad that most of the light gas turbines currently in use are aeroderivative gas turbines, and their combustion chambers basically follow the annular structure of aeroengines, but corresponding changes have been made to meet the requirements of ground pollution emissions. The ground gas turbine combustor must not only ensure stable operation, but also ensure a very low level of pollution emissions within the entire operating range. The stable work of the combustion chamber includes widening the boundary of lean flameout, avoiding spontaneous combustion, backfire, and combustion instability; the low pollution emission level of the combustion chamber avoids combustion in the combustion zone at a chemically appropriate ratio, eliminates the local high temperature zone, and controls the equivalent of the combustion zone Reduce the pollution emission in the whole working range by reducing the residence time of the gas in the high temperature area and other methods.

Contents of the invention

technical problem to be solved

In order to avoid the deficiencies of the prior art, the present invention proposes an axially graded low-pollution combustion chamber, which can effectively control the equivalence ratio between the on-duty combustion zone and the main combustion zone, improve the degree of oil-gas mixing, and reduce the different working conditions of the combustion chamber. The lower pollution emission level, and the pre-mixed mold adopts a reasonable structural design to prevent spontaneous combustion, tempering and other problems.

Technical solutions

An axially graded low-pollution combustion chamber, including a short burst diffuser, a combustion chamber flame tube, a combustion chamber casing, a duty level 10 and a main combustion level 12; it is characterized in that: the duty level 10 is a plurality of pre-combustion The mixed mode is evenly distributed on the end wall 11 of the combustion chamber head along the circumferential direction, and the outlet of the premixed mode convergence section is flush with the inner side of the end wall of the combustion chamber head; the main combustion stage 12 is a combination of multiple premixed modes, and the combination form is : Multiple rows of premixed molds are arranged on the inner wall 13 of the downstream flame cylinder and the outer wall 14 of the flame cylinder, the outlet of the convergent section of the premixed mold is flush with the inner side of the flame cylinder wall, and one row of premixed molds is at the same circumferential position as the duty level premixed mold The number of the premixed molds of the duty level 10 is equal to the number of the premixed molds arranged on the downstream flame tube inner wall 13 and the flame tube outer wall 14; each of the premixed molds is provided with a fuel pipeline, and the on-duty All the premixed models of the main combustion stage are supplied by one fuel pipeline; all the premixed modules of the main combustion stage are supplied by another fuel pipeline.

The multi-row setting premixed mode is 1 to 5 rows.

The premixing model of the duty stage 10 and the main combustion stage 12 adopts a multi-point injection lean fuel premixing pre-evaporation structure, including fuel nozzles 15, swirlers 17, oil collector rings 18, fuel injection holes 21 and premixing ring chambers 22. The rear end of the swirler 17 is provided with a premixing ring cavity 22 composed of a straight section 19 and a converging section 20. The fuel nozzle 15 is installed on the axis of the swirler 17 through the fuel nozzle mounting seat 16, and the outlet of the nozzle It is flush with the outlet of the swirler; the exterior of the swirler 17 is provided with an oil collecting ring 18, and 10-30 fuel injection holes 21 are evenly distributed on the straight section 19 along the circumferential direction at 3-5mm downstream of the swirler , connecting the oil collecting ring 18 and the premixing annular chamber 22, the diameter of the nozzle hole is 0.2-0.8mm; the length of the premixing annular chamber 22 is 0.25-0.75 times the product of the average flow velocity of the annular chamber and the spontaneous combustion time of the fuel, and the convergence section and the shaft The included angle is 30°～45°.

The swirler 17 is an axial swirler, the shape of the blades is straight blades, the number of blades is 6-18, and the blade angle is 30°-60°.

The center-to-center distance of the premixed molds of adjacent duty classes is 1.25 to 2.5 times the diameter of the premixed molds and not greater than 125mm.

The axial distance between the first row of premixed molds and the duty class is 0.75 to 1.5 times the diameter of the flame cylinder.

The axial distance between two adjacent rows of premixed molds is 1.25 to 2.5 times the diameter of the premixed molds.

Beneficial effect

An axially graded low-pollution combustion chamber proposed by the present invention adopts the axially graded combustion technology to divide the combustion chamber into a duty class and a main combustion class. The equivalence ratio between the on-duty combustion zone and the main combustion zone improves the degree of oil-gas mixing, reduces the pollution emission level of the combustion chamber under different working conditions, and the pre-mixing model adopts a reasonable structural design to prevent spontaneous combustion, backfire and other problems.

Compared with the prior art, the present invention has the following advantages:

1. The present invention provides an axially graded low-pollution combustion chamber. The combustion chamber is divided into the main combustion stage and the duty stage by adopting the axial staged combustion technology. The oil pre-mixing and pre-evaporation structure reduces the pollution emission level under small working conditions, and adopts axial classification to avoid mutual interference between the duty class and the main combustion stage, ensuring the flame stability in the duty combustion area.

2. As the working conditions increase, the main combustion stage starts to work, and the duty stage is located upstream of the main combustion stage. The high-temperature gas in the duty combustion area is conducive to the oil-gas mixing of the main combustion stage and the ignition of the main combustion stage. The axial classification improves Concentration of the high temperature area in the radial classification head, the main combustion stage adopts the multi-point injection lean oil premixing pre-evaporation structure to make the oil and gas in the main combustion area mix evenly, avoiding the local high temperature area, and at the same time, a large amount of air enters from the main combustion stage along the casing , resulting in faster gas flow in the flame tube, shortening the residence time of gas in the high temperature zone, and greatly reducing the pollutant emission level under large working conditions.

3. Multiple premixing modes of the main combustion stage are evenly distributed on the inner and outer walls of the flame tube along the circumferential direction, which improves the temperature distribution at the outlet of the combustion chamber, thereby omitting the mixing hole, allowing more air to participate in the combustion, and increasing the power of the gas turbine.

Description of drawings

Figure 1: Schematic diagram of an axially graded low-pollution combustion chamber according to an embodiment of the present invention

Figure 2: Schematic diagram of the structure of the combustion chamber flame tube applicable to different working ranges according to the embodiment of the present invention

Figure 3: Schematic diagram of the distribution structure of the duty class and the main combustion class premixed mode of the embodiment of the present invention

Figure 4: Schematic diagram of the structure of the axially graded full-ring combustion chamber of the embodiment of the present invention

Figure 5: Schematic diagram of the premixed mold structure of the embodiment of the present invention

In the figure: 1-inner wall of the pre-diffuser, 2-outer wall of the pre-diffuser, 3-flow path of the pre-diffuser, 4-sudden expansion section, 5-combustion outer casing, 6-outer ring cavity, 7-flame tube support plate, 8-chassis in combustion chamber, 9-inner ring cavity, 10-duty level, 11-end wall of combustion chamber head, 12-main combustion level, 13-inner wall of flame tube, 14-flame tube Outer wall, 15-fuel nozzle, 16-nozzle mounting seat, 17-swirl, 18-oil collecting ring, 19-straight section, 20-converging section, 21-fuel injection hole, 22-premixing ring cavity

Detailed ways

Now in conjunction with embodiment, accompanying drawing, the present invention will be further described:

The present invention adopts the following technical solutions: an axially graded low-pollution combustion chamber, including the inner wall of the pre-diffuser, the outer wall of the pre-diffuser, the flow channel of the pre-diffuser, the sudden expansion section, the casing outside the combustion chamber, and the outer wall of the pre-diffuser. ring cavity, flame tube support plate, combustion chamber casing, inner ring cavity, duty stage, combustion chamber head end wall, main combustion stage, flame tube inner wall, flame tube outer wall, the pre-diffuser flow path is composed of The inner wall of the pre-diffuser and the outer wall of the pre-diffuser are surrounded, and the pre-diffuser and the sudden expansion section constitute a short sudden expansion diffuser, which plays the role of deceleration and supercharging, which is beneficial to ignition and flame stable, the outer ring cavity is surrounded by the casing outside the combustion chamber and the outer wall of the flame tube, the inner ring cavity is surrounded by the casing inside the combustion chamber and the inner wall of the flame tube, and the main combustion stage air and the cooling air of the flame tube come from the outer ring cavity and the inner ring cavity, the duty level and the main combustion level are composed of multiple premixed molds, the duty level premixed molds are evenly distributed on the end wall of the combustion chamber head along the circumferential direction, and the main combustion level premixed molds are evenly distributed along the circumferential direction On the outer wall of the flame tube downstream of the duty level and on the inner wall of the flame tube, the duty level and the main combustion level are independently controlled to meet the requirements of different working conditions of the combustion chamber. ring, straight section, converging section, fuel injection hole, and premixing annular cavity, the premixing annular cavity is surrounded by a straight section and a converging section, fuel and air are premixed and pre-evaporated in the premixing annular cavity, A uniform mixture of oil and gas is formed, and spontaneous combustion is prevented through an appropriate length of the premixed ring cavity. The convergent section increases the axial velocity of the mixture of oil and gas, generates a detached flame, and prevents the occurrence of backfire.

Further, the duty stage is located on the end wall of the combustion chamber head, the outlet of the premixed mode convergence section is flush with the inside of the end wall of the combustion chamber head, the main combustion stage is located on the outer wall of the flame tube and the inner wall of the flame tube, and the premixed mode The converging section is flush with the inner side of the outer wall of the flame tube and the outer side of the inner wall of the flame tube to ensure the service life of the premixed mold.

Further, the duty-level premixed molds are evenly distributed on the end wall of the combustion chamber head along the circumferential direction, and the center distance between adjacent premixed molds is 1.25 to 2.5 times the diameter of the premixed molds, and is not greater than 125mm, ensuring that the distance between adjacent premixed molds There will be no interference between them, and the normal joint flames can be guaranteed.

Further, the premixing modules of the main combustion level are evenly distributed on the outer wall of the flame tube downstream of the duty class and on the inner wall of the flame tube along the circumferential direction, and the premixing models are arranged in 1 to 5 rows along the direction of the flame tube, and the number of premixing modules in each row is the same as that of the duty class premixed modules. The number of mixed models is the same, the axial distance between the first row of premixed molds of the main combustion stage and the duty class is 0.75 to 1.5 times the diameter of the flame tube, and it is at the same circumferential position as the duty class premixed molds, and the two adjacent rows of premixed The axial distance between the mixed molds is 1.25 to 2.5 times the diameter of the premixed molds to ensure that two adjacent rows of premixed molds will not interfere with each other. The two adjacent rows of premixed molds are arranged in a fork row to ensure that the outlet Uniformity of temperature distribution.

Further, the pre-mixing model adopts a multi-point injection lean oil pre-mixing pre-evaporation structure, the swirler adopts an axial swirler, the blade shape is a straight blade, the number of blades is 6-18, and the blade angle is 30°- 60°, the angle between the convergent section and the axial direction is 30°~45°, the length of the premixing ring cavity is 0.25~0.75 times the product of the average flow velocity of the ring cavity and the fuel self-ignition time, the nozzle adopts a single oil circuit centrifugal nozzle, the nozzle outlet and the rotary The outlet of the swirler is flush, and the fuel injection holes are located 3 to 5 mm downstream of the swirler, and are evenly distributed on the straight section along the circumferential direction. The number of injection holes is 10 to 30, and the diameter of the injection holes is 0.2 to 0.8 mm.

The present invention is described in detail below in conjunction with specific embodiment

As shown in Figure 1, a schematic diagram of an axially graded low-pollution combustion chamber of the present embodiment, the casing 5 outside the combustion chamber is welded to the outer wall 2 of the pre-diffuser, and is connected to the outer wall 14 of the flame tube through the tail flame tube support plate 7, Enclosing an outer ring cavity 6, the casing 8 in the combustion chamber is welded to the inner wall 1 of the pre-diffuser, and connected to the inner wall 13 of the flame tube through the rear flame tube support plate 7 to form an inner ring cavity 9, the inner wall 13 of the flame tube and the flame tube The outer wall 14 is connected by the head end wall 11 of the combustion chamber, and the duty-level premixed mold 10 is evenly distributed on the head end wall 11 along the circumferential direction. The mixed mold 12 is evenly distributed on the inner wall of the flame tube and the outer wall of the flame tube downstream of the duty class along the circumferential direction, and the convergence section of the premixed mold is flush with the inner side of the outer wall of the flame tube and the outer side of the inner wall of the flame tube to ensure the service life of the premixed mold.

As shown in Figure 2, it is a schematic diagram of the structure of three kinds of combustion chamber flame tubes suitable for different working ranges in this embodiment. The range increases successively. The axial distance between the first row of premixing molds in the main combustion stage and the duty class is 0.75 to 1.5 times the diameter of the flame tube, and it is at the same circumferential position as the duty class premixing molds. Two adjacent rows of premixing The axial distance between the molds is 1.25 to 2.5 times the diameter of the premixed molds to ensure that the two adjacent rows of premixed molds will not interfere with each other. The two adjacent rows of premixed molds are arranged in a fork row to ensure the outlet temperature. Uniformity of distribution.

The schematic diagram of the distribution structure of the duty-level and main combustion-level premixed molds in the embodiment of the present invention is shown in Figure 3. The duty-level premixed molds are evenly distributed on the head end wall 11, and the center distance between the adjacent duty-level premixed molds is the premixed mold 1.25-2.5 times of the diameter, and not more than 125mm, which can not only ensure that there will be no interference between adjacent premixed models, but also ensure normal joint flames. circumferential position.

Fig. 4 is a schematic diagram of the structure of the axially graded full-circle combustion chamber of the embodiment. The premixed mold 10 of the duty level is uniformly distributed on the head end wall 11 along the circumferential direction, and the premixed mold 12 of the main combustion level is uniformly distributed on the inner wall 13 of the downstream flame tube of the duty level along the circumferential direction. and on the outer wall 14 of the flame tube to ensure uniform oil and gas mixing in the full-ring combustion chamber, high combustion efficiency, uniform temperature distribution at the outlet of the combustion chamber, and low pollution emission levels.

Figure: 5 is a schematic diagram of the premixed model structure, which adopts a multi-point injection premixed preevaporation structure, including fuel nozzle 15, nozzle mounting seat 16, swirler 17, oil collection ring 18, straight section 19, convergent section 20, fuel oil Spray hole 21, premixing ring cavity 22, said premixing ring cavity 22 is composed of straight section 19 and converging section 20, swirler 16 adopts axial swirler, blade shape is straight blade, number of blades is 6 ～18 blades, the blade angle is 30°～60°, the angle between the convergent section and the axial direction is 30°～45°, the length of the premixing annular cavity 22 is 0.25～0.75 times of the product of the average flow velocity of the annular cavity and the spontaneous combustion time of the fuel, and the fuel Two paths enter the premixing ring cavity, one path is sprayed from the fuel nozzle 15, the fuel nozzle adopts a single oil path centrifugal nozzle, the outlet of the nozzle is flush with the outlet of the swirler, and one path is sprayed radially through the oil collecting ring 18 along the fuel injection hole 21 In the pre-mixing ring chamber, fuel and air form a uniform oil-air mixture in the pre-mixing ring chamber 22. The fuel injection holes are located 3 to 5 m downstream of the swirler, and are evenly distributed on the straight section 19 along the axial direction. The number of injection holes 10 to 30, nozzle diameter 0.2 to 0.8mm.

Working process of the present invention is as follows:

The axially graded low-pollution combustion chamber of the present invention adopts axially graded combustion technology to divide the combustion chamber into a duty class and a main combustion stage, and the air coming out of the diffuser is divided into three paths, which enter the outer ring cavity and the head duty respectively. Stage, inner ring cavity, most of the air in the inner ring cavity and outer ring cavity enters the flame tube through the main combustion stage to participate in combustion, and a small part of the air is used to cool the flame tube.

Under small working conditions, only the duty class works, and the duty class adopts a multi-point injection lean fuel premixed pre-evaporation structure. Combustion, to ensure the pollution emission level under small working conditions, the axial classification avoids the mutual interference between the duty class and the main combustion stage, widens the lean flameout boundary of the combustion chamber, and ensures the stability of the flame in the duty combustion area.

With the increase of working conditions, the on-duty stage and the main combustion stage work at the same time. The premixing models of the main combustion stage are evenly distributed on the inner wall of the flame tube and the outer wall of the flame tube in the full-ring combustion chamber. The evaporation structure makes the oil and gas mixture in the main combustion area more uniform, and the formed uniform oil and gas mixture is ignited by the high-temperature gas in the upstream on-duty combustion area, and burns with higher efficiency under the heating of the upstream high-temperature gas. The cavity enters the combustion chamber from the main combustion stage, which leads to the acceleration of the gas flow rate in the flame tube, shortens the residence time of the gas in the high temperature area, and thus greatly reduces the pollutant emission level under large working conditions.

In the present invention, the pre-mixing mode adopts a multi-point injection pre-mixing and pre-evaporation structure, and by rationally designing the structure of the pre-mixing section, the problems of spontaneous combustion and tempering of the combustion chamber are avoided, and the stable operation of the combustion chamber is ensured.

Claims (6)

1. an axially graded low-pollution combustion chamber, comprising a short burst diffuser, a combustion chamber flame tube, a combustion chamber casing, a duty class (10) and a main combustion stage (12); it is characterized in that: the duty The stage (10) is that a plurality of premixed molds are evenly distributed on the end wall (11) of the combustion chamber head along the circumferential direction, and the outlet of the convergent section of the premixed mold is flush with the inner side of the end wall of the combustion chamber head; the main combustion stage (12) It is a combination of multiple premixed modes, and the combined form is: multiple rows of premixed modes are arranged on the inner wall (13) of the downstream flame tube and the outer wall (14) of the flame tube, and the outlet of the convergent section of the premixed mode is flush with the inner side of the flame tube wall. The position of the first row of premixed molds of the main combustion stage (12) in the circumferential direction of the flame tube outer wall (14) and the position of the premixed molds of the duty level (10) in the circumferential direction of the combustion chamber head end wall (11) are one by one. Corresponding; The number of the premixed molds of the duty level (10) is equal to the number of the premixed molds arranged on the downstream flame tube inner wall (13) and the flame tube outer wall (14); each premixed mold Fuel pipelines are provided, and all premixed models in the duty class are supplied with fuel by one fuel pipeline; all premixed modules in the main combustion stage are supplied with fuel by another fuel pipeline; The premixing model of the duty stage (10) and the main combustion stage (12) adopts a multi-point injection lean oil premixing pre-evaporation structure, including fuel nozzles (15), swirlers (17), oil collector rings (18) , the fuel injection hole (21) and the premixing annular chamber (22); the rear end of the swirler (17) is provided with a premixing annular chamber (22) composed of a straight section (19) and a converging section (20), The fuel nozzle (15) is installed on the axis of the swirler (17) through the fuel nozzle mounting seat (16), and the nozzle outlet is flush with the swirler outlet; the swirler (17) is provided with an oil collection ring ( 18), at 3-5mm downstream of the swirler, 10-30 fuel injection holes (21) are evenly distributed on the straight section (19) along the circumferential direction, communicating with the oil collecting ring (18) and the premixing ring chamber ( 22), the diameter of the injection hole is 0.2-0.8 mm; the length of the premixed annular cavity (22) is 0.25-0.75 times the product of the average flow velocity of the annular cavity and the fuel self-ignition time, and the angle between the convergent section and the axial direction is 30°-45° . 2. The axially graded low-pollution combustion chamber according to claim 1, characterized in that: the multi-row premixed mode is 1 to 5 rows. 3. The axially graded low-pollution combustion chamber according to claim 1, characterized in that: the swirler (17) is an axial swirler, the shape of the blades is straight blades, the number of blades is 6 to 18, and the number of blades is 6-18. The angle is 30°～60°. 4. The axially graded low-pollution combustion chamber according to claim 1, wherein the distance between the centers of the premixed molds of adjacent duty levels is 1.25 to 2.5 times the diameter of the premixed molds, and not greater than 125mm. 5. The axially graded low-pollution combustion chamber according to claim 1, wherein the axial distance between the first row of premixed molds and the duty class is 0.75 to 1.5 times the diameter of the flame cylinder. 6. The axially graded low-pollution combustion chamber according to claim 1, wherein the axial distance between two adjacent rows of premixed molds is 1.25 to 2.5 times the diameter of the premixed molds.