CN112066412A - Combustion chamber, gas turbine and method for suppressing oscillatory combustion - Google Patents
Combustion chamber, gas turbine and method for suppressing oscillatory combustion Download PDFInfo
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- CN112066412A CN112066412A CN201910496248.4A CN201910496248A CN112066412A CN 112066412 A CN112066412 A CN 112066412A CN 201910496248 A CN201910496248 A CN 201910496248A CN 112066412 A CN112066412 A CN 112066412A
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23R—GENERATING COMBUSTION PRODUCTS OF HIGH PRESSURE OR HIGH VELOCITY, e.g. GAS-TURBINE COMBUSTION CHAMBERS
- F23R3/00—Continuous combustion chambers using liquid or gaseous fuel
- F23R3/28—Continuous combustion chambers using liquid or gaseous fuel characterised by the fuel supply
- F23R3/286—Continuous combustion chambers using liquid or gaseous fuel characterised by the fuel supply having fuel-air premixing devices
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23R—GENERATING COMBUSTION PRODUCTS OF HIGH PRESSURE OR HIGH VELOCITY, e.g. GAS-TURBINE COMBUSTION CHAMBERS
- F23R3/00—Continuous combustion chambers using liquid or gaseous fuel
- F23R3/02—Continuous combustion chambers using liquid or gaseous fuel characterised by the air-flow or gas-flow configuration
- F23R3/26—Controlling the air flow
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23R—GENERATING COMBUSTION PRODUCTS OF HIGH PRESSURE OR HIGH VELOCITY, e.g. GAS-TURBINE COMBUSTION CHAMBERS
- F23R3/00—Continuous combustion chambers using liquid or gaseous fuel
- F23R3/28—Continuous combustion chambers using liquid or gaseous fuel characterised by the fuel supply
- F23R3/38—Continuous combustion chambers using liquid or gaseous fuel characterised by the fuel supply comprising rotary fuel injection means
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Abstract
The invention relates to a combustion chamber of a gas turbine, which comprises a flame tube head part, wherein the head part comprises a main combustion stage and a pre-combustion stage, the pre-combustion stage is taken as a center, a plurality of main combustion stages are distributed around the pre-combustion stage along the circumferential direction, the pre-combustion stage is provided with a pre-combustion stage fuel nozzle and a pre-combustion stage outer wall positioned at the circumferential outer part of the pre-combustion stage, the main combustion stage is provided with a main combustion stage inner wall, and a radial space in the inner part of the pre-combustion stage outer wall provides a pre-combustion stage channel for mixing air entering the pre-combustion stage through a pre-combustion stage air inlet part and fuel sprayed by the pre-combustion stage fuel nozzle; the pre-combustion stage air inlet part comprises a pre-combustion stage first air inlet part and a pre-combustion stage second air inlet part; the precombustion stage first air intake includes a second orifice having an acoustic throttling effect through a radial thickness of the precombustion stage outer wall.
Description
Technical Field
The invention relates in particular to a combustion chamber, a gas turbine and a method of suppressing oscillatory combustion.
Background
In order to meet the airworthiness requirement, the aero-engine adopts the lean oil combustion technology to reduce NOxWhile lean combustion tends to initiate oscillatory combustion, it can be severe enough to cause ablation of the hot end components of the combustion chamber. In addition, to reduce NOxEmission, more air needs to be distributed to the combustion chamber head to reduce the equivalence ratio of the combustion zone, whenThe flame tube cooling air is reduced, the acoustic impedance of the flame tube wall surface is increased, and the oscillation combustion degree is also increased.
In order to suppress the oscillatory combustion, there are two embodiments of active control and passive control. For active control, dynamic signals of pulsating pressure or other pneumatic parameters in the combustion chamber need to be monitored in real time, and according to the oscillation frequency and waveform of the pulsating pressure, a control system supplies fuel or adds an opposite-phase excitation to a gas path through a high-speed actuating element so as to reduce the pulsating pressure in the combustion chamber. But this requires a more complex control system and the requirements on the sensor itself are high. For passive control, it is necessary to identify the conditions of the occurrence of the oscillatory combustion or the mechanism of the occurrence of the oscillatory combustion through experiments, and to improve the structure of the combustion chamber or change the fuel supply manner according to the actual conditions of the oscillatory combustion.
For the central staged combustion technique, as shown in fig. 1, by adjusting the staged proportion of fuel, more fuel can be fed into the precombustion stage, thereby achieving a reduction in the intensity of the oscillatory combustion. But the intensity of the oscillatory combustion is reduced and NO is increasedxAnd (4) discharging, so that the discharge margin is reduced. In order to ensure the emission characteristics, the boundary of stable combustion needs to be widened, i.e., the oscillation boundary (dotted line, i.e., position where the oscillation amplitude suddenly increases) in fig. 1 needs to be shifted to the left of the coordinate axis by a new design or a system control means.
For the central staged combustion mode, through optical diagnostic techniques, one of the main driving mechanisms of the currently known oscillatory combustion is pre-combustion stage flow instability, which is mainly related to the number of swirl flows of the pre-combustion stage, the pre-combustion stage strong swirl facilitates the formation of a central recirculation zone to stabilize the flame, but unstable spiral vortex and vortex shedding are easily formed, the frequency of the vortex shedding is related to the number of swirl flows (generally, the higher the number of swirl is, the higher the vortex shedding frequency is), the periodic change of the flame structure (i.e., the interaction between the flame and the vortex) is caused by the spiral vortex and the vortex shedding, and the corresponding type of heat release fluctuation occurs in the time and space dimensions of the combustion zone, so as to drive the circumferential modal pressure oscillation (prone to spiral vortex) and the axial modal pressure oscillation (prone to vortex shedding) of the full-ring combustor.
Most of the design results of the conventional combustion chamber aerodynamic heating power scheme only consider the steady-state working state or the steady combustion state, but cannot meet the transient state or the unsteady combustion state, such as the influence of oscillatory combustion on aerodynamic heating power. In order to inhibit the oscillatory combustion and ensure the safety, the performances such as emission and outlet temperature distribution have to be sacrificed, so that the conventional combustion chamber pneumatic-thermal design scheme has difficulty in ensuring that all indexes are met at the same time.
There is a need in the art for a combustor, a gas turbine, and a method of suppressing oscillatory combustion that suppresses the oscillatory combustion phenomenon of the combustor, widens the stable combustion boundary, improves combustion performance, and ensures the life of the combustor and the performance and life of the gas turbine.
Disclosure of Invention
It is an object of the present invention to provide a combustion chamber.
It is another object of the present invention to provide a gas turbine.
It is a further object of the present invention to provide a method of suppressing ringing combustion.
A combustion chamber according to an aspect of the present invention comprises a liner head, the head comprising a main combustion stage and a precombustion stage, the precombustion stage being centered on the precombustion stage, a plurality of the main combustion stages being distributed circumferentially around the precombustion stage, the precombustion stage having a precombustion stage fuel nozzle and a precombustion stage outer wall circumferentially outside thereof, the main combustion stage having a main combustion stage inner wall, a radial space inside the precombustion stage outer wall providing a precombustion stage passage through which air entering the precombustion stage through a precombustion stage intake part mixes with fuel injected from the precombustion stage fuel nozzle; the pre-combustion stage air inlet part comprises a pre-combustion stage first air inlet part and a pre-combustion stage second air inlet part; the precombustion stage first air intake includes a second orifice having an acoustic throttling effect through a radial thickness of the precombustion stage outer wall.
In an embodiment of the combustion chamber, the second port with acoustic throttling is structured such as to satisfy:
wherein, P'4Is the amplitude of the pulsating pressure in the flame tube, P4Is the mean pressure, Δ P, in the flame tubeoriThe constant beta is the energy conversion efficiency of converting the acoustic energy of the second duct into kinetic energy for the via hole pressure drop of the acoustic orifice.
In an embodiment of the combustion chamber, the second air intake has a second air intake passage provided by a radial space between the outer wall of the pre-combustion stage and the outer wall of the fuel nozzle of the pre-combustion stage, and a swirler is arranged in the second air intake passage.
In an embodiment of the combustion chamber, the first pre-combustion stage air inlet portion and the second pre-combustion stage air inlet portion respectively and independently deliver air to the pre-combustion stage passage, and the air input from the two air inlet portions is mixed in the pre-combustion stage passage.
In an embodiment of the combustion chamber, the second port axis is parallel to a radial direction.
In an embodiment of the combustion chamber, the axis of the second port is inclined with respect to the radial direction in a positive or negative direction.
In an embodiment of the combustion chamber, the pre-stage fuel nozzle is a centrifugal nozzle.
A combustion chamber according to another aspect of the present invention comprises a liner head portion including a main combustion stage and a pre-combustion stage, air for mixing with fuel injected from a fuel nozzle of the pre-combustion stage enters the pre-combustion stage through an air intake portion of the pre-combustion stage, the combustion chamber includes a steady state and an oscillatory combustion state, the air intake portion of the pre-combustion stage includes a first air intake portion of the pre-combustion stage and a second air intake portion of the pre-combustion stage, the first air intake portion of the pre-combustion stage has a second port passage, in the steady state, air can enter the pre-combustion stage through the first air intake portion of the pre-combustion stage and the second air intake portion of the pre-combustion stage respectively, in the oscillatory combustion state, the throttling effect of the second port passage reduces the proportion of air entering the pre-combustion stage through the first air intake portion of the pre-combustion stage under the oscillatory combustion environment of propagation of pressure waves in a liner chamber of the combustion chamber, the proportion of air entering the pre-combustion stage through the second air inlet part of the pre-combustion stage is increased, so that the swirl number of the outlet of the pre-combustion stage is adjusted.
A gas turbine according to a further aspect of the invention comprises a combustor as described in any one of the above.
A method of suppressing ringing combustion in accordance with yet another aspect of the present invention includes:
a plurality of air flow paths are arranged to provide air for the pre-combustion stage of the combustion chamber;
in a steady state, the plurality of air flow paths provide air to the precombustion stage;
in the oscillation combustion state, the throttling effect generated by one air flow path of the multiple air flow paths under the environment of oscillation pressure waves propagated by the flame tube cavity of the combustion chamber enables the proportion of the air flow path to be reduced, the proportion of the air flow of other air flow paths in the multiple air flow paths is correspondingly increased, and the number of swirl at the outlet of the pre-combustion stage is adjusted.
In conclusion, the improved effects of the invention include that the air inlet duct with the acoustic throttling function is arranged, so that the combustion performance under the stable state is ensured, the oscillation combustion boundary is widened, more fuel oil can be distributed to the main combustion stage, the potential of further reducing emission is realized, and the outlet temperature distribution quality is improved; even if oscillatory combustion occurs, the first air inlet part of the precombustion stage is sealed through the acoustic throttling action of pressure waves, the proportion of the air inflow of the first air inlet part of the precombustion stage is reduced, the proportion of the air inflow of the second air inlet part of the precombustion stage is increased, the number of outlet rotational flows of the precombustion stage is changed (the design target is generally the direction of reducing the number of rotational flows, but the condition of inhibiting the oscillatory combustion by designing in the direction of increasing is not denied), the spiral vortex/vortex shedding strength of the precombustion stage is weakened, the spiral vortex/vortex shedding and the oscillation frequency can be subjected to frequency mismatch, the heat release driving force in a combustion area is weakened, the circumferential modal pressure oscillation amplitude or the axial modal pressure oscillation amplitude of the full-ring combustion chamber is reduced, the combustion stability is ensured, and the performance and the service life of the combustion chamber and a gas turbine are improved.
Drawings
The above and other features, properties and advantages of the present invention will become more apparent from the following description of the embodiments in conjunction with the accompanying drawings, it being noted that the drawings are given by way of example only and are not drawn to scale, and should not be taken as limiting the scope of the invention which is actually claimed, wherein:
FIG. 1 is a schematic illustration of the effect of fuel staging ratio on pulsating pressure and emissions.
FIG. 2 is a graph of pulsating pressure and combustor via pressure drop as a function of acoustic throttling effect.
FIG. 3 is a schematic illustration of an air flow path of a combustor for one or more embodiments.
FIG. 4 is a schematic view of an air flow path of a combustor head at steady state in one or more embodiments.
FIG. 5 is a schematic air flow path of a combustor head in an oscillatory combustion regime according to one or more embodiments.
FIG. 6 is a schematic view of a pre-combustion stage configuration of a combustor head in accordance with one or more embodiments.
FIG. 7 is a schematic structural diagram of a first air intake portion of one or more embodiments.
FIG. 8 is a pre-combustion stage structured gas quantity analysis schematic according to FIG. 6.
Detailed Description
The following discloses many different embodiments or examples for implementing the subject technology described. Specific examples of components and arrangements are described below to simplify the present disclosure, but these are merely examples and do not limit the scope of the invention. For example, if a first feature is formed over or on a second feature described later in the specification, this may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features are formed between the first and second features, such that the first and second features may not be in direct contact. Additionally, reference numerals and/or letters may be repeated among the various examples throughout this disclosure. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed. Further, when a first element is described as being coupled or coupled to a second element, the description includes embodiments in which the first and second elements are directly coupled or coupled to each other, as well as embodiments in which one or more additional intervening elements are added to indirectly couple or couple the first and second elements to each other.
Further, it is to be understood that the positional or orientational relationships indicated by the terms "front, rear, upper, lower, left, right", "transverse, vertical, horizontal" and "top, bottom" and the like are generally based on the positional or orientational relationships illustrated in the drawings and are provided for convenience in describing the invention and for simplicity in description, and that these terms are not intended to indicate and imply that the referenced devices or elements must be in a particular orientation or be constructed and operated in a particular orientation without departing from the scope of the invention. Also, this application uses specific language to describe embodiments of the application. The terms "inside" and "outside" refer to the inner and outer parts relative to the outline of each part itself, and the terms "first", "second", "third", and the like are used to define the parts, and are used only for the convenience of distinguishing the corresponding parts, and unless otherwise stated, the terms have no special meaning, and therefore, the scope of the present invention should not be construed as being limited. Reference throughout this specification to "one embodiment," "an embodiment," and/or "some embodiments" means that a particular feature, structure, or characteristic described in connection with at least one embodiment of the present application is included in at least one embodiment of the present application. Therefore, it is emphasized and should be appreciated that two or more references to "an embodiment" or "one embodiment" or "an alternative embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, some features, structures, or characteristics of one or more embodiments of the present application may be combined as appropriate.
Referring to fig. 3, the combustion chamber structure of the gas turbine comprises a front diffuser 1, an outer casing 2, an inner casing 9, a head 8, a fuel nozzle 3, an ignition electric nozzle 5, an outer ring flame tube 6 and an inner ring flame tube 11; the head part 8 can adopt an air inlet structure comprising a swirler, and both the outer ring flame tube 6 and the inner ring flame tube 11 can adopt an air film cooling mode. Under the stable combustion state, air flows out from the outlet of the preposed diffuser 1 and is divided into three flows to enter the flame tube cavity 12: air 7 enters the flame tube chamber 12 through the swirler passages of the head 8; air 4 enters the flame tube cavity 12 through the cooling holes of the outer ring flame tube 6; air 10 enters the combustor basket cavity 12 through the inner ring combustor basket 11 cooling holes.
It should be noted that the axial and radial directions of the following embodiments refer to the axial and radial directions of the combustion chamber head 8, and the combustion chamber head 8 may be arranged obliquely to the axial direction of the engine as shown in fig. 3, so that the axial and radial directions of the following embodiments may not necessarily be the same as the axial and radial directions of the engine.
Referring to fig. 4, in one embodiment, for air entering the liner cavity 12 through the head 8 when the combustion chamber is in a steady state, the air flow paths associated with unsteady pre-stage flow of one of the primary mechanisms of oscillatory combustion include air flow paths 21, 22 entering the pre-stage through the pre-stage intake and air flow path 23 entering through the main stage swirler 16, the air flow path 22 being fed to the pre-stage channel 301 through the first pre-stage intake 101, the air flow path 21 being fed to the pre-stage channel 301 through the second pre-stage intake 201, the air flow paths 22, 21 meeting in the pre-stage channel 301 and being blended with fuel injected from the fuel injector 19 and being output from the outlet end of the pre-stage channel 301. Referring to fig. 5, when the combustion chamber is in the oscillation combustion state, the pre-combustion stage first intake portion 101 is closed, and air cannot enter the pre-combustion stage through the air flow path 22 passing through the pre-combustion stage first intake portion 101 but can enter the pre-combustion stage passage 301 only through the air flow path 21 entering the pre-combustion stage from the pre-combustion stage second intake portion 201. The principle of achieving the effect of suppressing the oscillatory combustion is that, because the swirl number of the outlet of the precombustion stage is determined by the air flow path 21 and the air flow path 22, the swirl number of the precombustion stage directly affects the flow stability of the precombustion stage, and plays a leading role in the formation of the spiral vortex and the vortex shedding, when in the oscillatory combustion state, because the first air inlet 101 of the precombustion stage is closed, the swirl number of the precombustion stage is determined only by the air flow path 21, and the design is matched with the CFD method through the design of the opening of the first air inlet 101 of the precombustion stage, so that the swirl number of the outlet of the precombustion stage changes (the design target is generally in the direction of reducing the swirl number, but the situation of suppressing the oscillatory combustion is not excluded when the first air inlet 101 is closed, for example, although the increase of the swirl number has the negative effect of increasing the strength of the oscillatory combustion, the increase of the swirl number also has the positive effect of enabling the vortex frequency and the oscillation frequency to, when the positive effect is greater than the negative effect under the specific combustion chamber structure and working condition, namely the oscillatory combustion can be inhibited), the spiral vortex/vortex shedding strength of the precombustion stage is weakened, the spiral vortex/vortex shedding and the oscillation frequency can generate the frequency error, the heat release driving force in the combustion area is weakened, and the circumferential modal pressure oscillation amplitude or the axial modal pressure oscillation amplitude of the full-ring combustion chamber is reduced.
Referring to fig. 4-6, in one or more embodiments, a specific structure of the head 8 may be that the head 8 includes a main combustion stage and a pre-combustion stage centered on the pre-combustion stage, and a plurality of main combustion stages are distributed circumferentially around the pre-combustion stage. The pre-combustion stage may include a pre-combustion stage fuel nozzle 19 and a pre-combustion stage outer annular wall 18 located circumferentially outward thereof. The main combustion stage may include a main combustion stage inner annular wall 14 and a main combustion stage outer annular wall 13, a main combustion stage upstream end wall 170 projecting radially from the main combustion stage inner annular wall 14 and a main combustion stage downstream end wall 171 projecting radially from the main combustion stage outer annular wall 13, with air entering the main combustion stage being channeled along an air flow path 23 from an axial space between the main combustion stage upstream end wall 170 and the main combustion stage downstream end wall 171 into the main combustion stage through the main combustion stage swirler 16 and blended with fuel injected from the main combustion stage fuel injection holes 17 in a radial space between the main combustion stage inner annular wall 14 and the main combustion stage outer annular wall 13 for output to the combustor basket receptacle 12. The radial space inside the outer ring wall 18 of the pre-combustion stage provides a pre-combustion stage channel 301 for mixing air entering the pre-combustion stage through the air inlet part of the pre-combustion stage and fuel injected by the fuel nozzle 19 of the pre-combustion stage; the pre-combustion stage air inlet part comprises a pre-combustion stage first air inlet part 101 and a pre-combustion stage second air inlet part 201, the pre-combustion stage first air inlet part 101 comprises a second pore passage 25 which penetrates through the radial thickness of the pre-combustion stage outer annular wall 18 and has an acoustic throttling effect, and air enters an air passage provided by a radial space between the pre-combustion stage outer annular wall 18 and the main combustion stage inner annular wall 14 along the air flow path 22 and then enters the pre-combustion stage passage 301 from the second pore passage 25. And the specific structure of the second air inlet portion 201 may be a second air inlet passage provided by the radial space between the outer ring wall 18 of the pre-combustion stage and the outer wall of the fuel nozzle 19 of the pre-combustion stage, and the swirler 20 is arranged in the second air inlet passage. The pre-combustion stage fuel nozzle 19 is a centrifugal nozzle to enhance the atomization and mixing effect of the fuel and air. As shown in fig. 4, the first and second pre-combustion stage air inlets 101 and 201 may independently deliver air to the pre-combustion stage passage 301, and the air flow paths 21 and 22 may interact with each other after entering the pre-combustion stage passage 301. It is understood that the acoustic throttling of the second port 25 shown in fig. 5 is closed in the oscillatory combustion state so that gas cannot pass through the second port 25 to close the first intake portion 101, which is an example of an ideal throttling state and should not be limited thereto. An example of reducing the flow rate of intake air to the first intake portion 101 may also be employed. The principle of the acoustic throttling effect of the second duct 25 is that when the combustion chamber is in the oscillatory combustion state, the pressure wave of the oscillatory combustion can generate the acoustic throttling effect on the gas passing through the duct with a specific structure, and the actual pressure drop of the via hole is increased, and the specific phenomenon can be referred to fig. 2.
FIG. 2 is the inventors' discovery of the acoustic throttling effect of the cooling holes of the combustor basket assembly, plotted on the ordinate as the actual through hole pressure drop Δ P versus the mean pressure P of the basket receptacle 124To the power of 3/2, i.e. of
The abscissa is the pulsating pressure amplitude | P 'of the liner cavity 12'4The value of the average pressure P and the value of the amplitude corresponding to the main frequency after Fourier transform4Is a percentage of
Since the flow mach number in the combustion chamber is generally 0.2 or less, each combustion chamber is normally (for example, in the case of the absence of the oscillatory combustion)Pressure drop in the intake passage
Determined by its flow resistance characteristics, i.e. only with the effective area ACdAnd intake air composition parameter
In connection with, wherein, W31For the outlet flow, T, of the pre-diffuser 1 of the combustion chamber31Is the outlet temperature, P, of the pre-diffuser 1 of the combustion chamber31The outlet pressure of a front diffuser 1 of the combustion chamber; if it is
Without change, the combustor pressure drop is controlled by ACdAnd (6) determining. FIG. 2 shows that
Under the condition of no change, the fuel-air ratio is increased, so that the combustion chamber generates oscillation combustion, and the oscillation amplitude is increased along with the increase of the fuel-air ratio, so that the combustion chamber pressure drop observed in the test is changed along with the oscillation amplitude. Test data analysis results show that the pore passage for cooling air inlet of the flame tube is throttled under the pressure wave environment of oscillatory combustion, so that the AC of the cooling air of the flame tubedReduced, total combustion chamber flow ACdDecreasing, resulting in an increase in combustion chamber pressure drop. The oblique lines in the figure represent the pulsating pressure amplitude corresponding to the trigger throttling effect; in the range of the upper left side of the oblique line (y is equal to x in the figure), the pulsating pressure cannot change the pressure drop of the combustion chamber, in the range of the lower right side of the oblique line, the pulsating pressure can cause the pressure drop of the combustion chamber to increase, when the pulsating pressure increases to a certain degree, the air inlet of the flame tube is completely blocked, and all the air inlet can only enter the flame tube from the head. By theoretical derivation, the triggering conditions for acoustic throttling can be derived as follows:
wherein, P'4Is a flame tubeAmplitude of internal pulsating pressure, P4Is the mean pressure, Δ P, in the flame tubeoriAnd for the design of the acoustic throttling hole, the constant beta is the energy conversion efficiency of converting the acoustic energy of the second hole channel with the acoustic throttling function into the kinetic energy. The constant β is related to the pore diameter d, the pore length l, with β being greater the smaller d or the larger l. For example, as can be seen from FIG. 2
1) Designing a pore passage with pressure drop of 3 percent (oil-gas ratio is low, and oscillation combustion is not generated), wherein the pulsating pressure is less than 0.5 percent, and at the moment, acoustic throttling does not occur, so that the actual pressure drop in the combustion chamber is basically the same as the designed pressure drop; when the pulsating pressure is between 0.5 and 3 percent, a small part of the flame tube assembly (such as an inner ring or an outer ring of the flame tube) generates throttling action first, and the pressure drop of the combustion chamber is slightly increased; when the pulsating pressure is more than 3%, most of the flame tube assemblies are throttled, and the pressure drop of a combustion chamber is obviously increased;
2) the design pressure drop of 5% is similar to the 3% case, but due to the design pressure drop increase, it is required that the pulsating pressure exceeds 1%, and a small part of the flame tube assembly is throttled. The staged throttling mode (a small part of the flame tube assembly and then a large part of the flame tube assembly) is related to the opening mode of the cooling holes; additional experimental results designed for 3% and 5% pressure drop also demonstrate that throttling is related to pressure drop.
Based on the principle, the inventor creatively applies the adverse phenomenon of the acoustic throttling of the flame tube cooling hole, which is found in the combustion chamber test, to the design of the head pre-burning stage, namely, the head pre-burning stage air hole with the acoustic throttling function is designed, the first air inlet part is closed during the oscillatory combustion to adjust the outlet swirl number of the pre-burning stage (the design target is generally the direction of reducing the swirl number, but the condition of inhibiting the oscillatory combustion by designing the pre-burning stage air hole in the increasing direction is not excluded) and inhibit the oscillatory combustion.
Referring to fig. 7, in one or more embodiments, the structural parameters of the second orifice 25 having an acoustic throttling effect include the total number of orifices N, the orifice diameter d, and the orifice length l. In order to have an acoustic throttling effect, the pressure is required to be adjusted according to the requirementsVia design pressure drop for two channels 25
The appropriate hole diameter d and hole length l are selected. According to actual requirements, the shape of the second duct 25 may be a straight-hole duct 251 whose axis is parallel to the radial direction, or an inclined-hole duct 252 having a positive inclination angle α with the radial direction, or an inclined-hole duct 253 having a negative inclination angle- α with the axial direction, so as to ensure the swirl number of the outlet of the pre-combustion stage in a stable state, which may be specifically evaluated by a Computational Fluid Dynamics (CFD) method. In the oscillatory combustion state, the number of outlet swirls of the precombustion stage after closing the second port 25 due to the acoustic throttling effect is only related to the configuration of the swirl blades of the swirler 20 of the second intake portion, and can be evaluated specifically by a Computational Fluid Dynamics (CFD) method. Referring to fig. 8, the air flow rate for the precombustion stage first intake portion 101 is W1And the air flow rate W of the second air intake portion 2012The flow rate of air through the jet of the outlet cross section 26 of the pre-combustion stage channel 301 is W1+W2. When the combustion chamber is in a stable combustion state, W1＝a，W2B; during the oscillatory combustion, W is now present due to the acoustic throttling of the second port 251＝0，W2A + b (can be combined with a CFD method, and partial optimization of head air intake is carried out to ensure that the air intake flow of the precombustion stage does not change significantly or the variation is small under the condition of stable combustion or oscillatory combustion to the greatest extent), and the air flow passing through the fuel spray opening angle alpha of the precombustion stage can be basically maintained at W1+W2A + b, the aerodynamic atomization effect of the fuel injected from the pre-combustion stage fuel nozzle 19 is substantially unchanged. The change direction (decrease or increase) and the change degree of the jet swirl number at the outlet cross section 26 of the pre-combustion stage channel 301 in the stable state of the combustion chamber to the jet swirl number at the outlet cross section 26 of the pre-combustion stage channel 301 in the oscillating combustion state can be realized by designing the total number N of the structural dimensions of the second duct, the diameter d of the hole, the positive and negative directions of the inclination angle and the ratio a/(a + b) of the air inflow of the second duct 25 as shown in fig. 7, and the process can be preliminarily calculated by a CFD method. The general design requires the opening direction alpha of the second port 25 and the swirl of the pre-combustion stage swirler 20The flow blades are in the same direction, so that when the oscillatory combustion initially occurs, when the second duct 25 is subjected to an acoustic throttling action to reduce the air inlet flow of the first air inlet part 101 of the pre-combustion stage, the swirl number of the pre-combustion stage changes in the direction of reduction, the strength of the spiral vortex/vortex shedding of the pre-combustion stage is weakened, the movement frequency of the spiral vortex/vortex shedding is changed, and the design size of the second duct 25, and pre-combustion stage pneumatic design parameters such as a/(a + b), the positive and negative directions of inclination, the inclination angle and the like are determined by adjusting the target (the strength and the frequency of the vortex).
From the above description, it is known that a method of suppressing oscillatory combustion in a combustion chamber of a gas turbine may include the steps of:
a plurality of air flow paths are provided to provide air to the pre-combustion stage of the combustion chamber, for example, air flow paths 21, 22 are provided to provide air to the pre-combustion stage;
in a steady state, the plurality of air flow paths provide air for the pre-combustion stage; for example, in a steady state, the air flow paths 21, 22 provide air for the pre-combustion stage;
in an oscillatory combustion state, one air flow path of a plurality of air flow paths is subjected to the throttling action of oscillatory pressure waves propagated from the flame tube cavity, so that the air flow rate of the air flow path is reduced, the proportion of the air flow rates of other air flow paths in the plurality of air flow paths is correspondingly increased, and the number of the pre-combustion stage rotational flows is adjusted; for example, in the oscillation combustion state, the air flow path 22 is closed by the acoustic throttling action of the oscillation pressure wave propagated by the inner cavity, the total amount of air is approximately unchanged, the air enters the pre-combustion stage only from the air flow path 21, that is, the air flow of the air flow path 21 is increased, the number of the swirl flow of the pre-combustion stage is changed in the direction of decreasing, so that the spiral vortex/vortex shedding strength of the pre-combustion stage is weakened, the spiral vortex/vortex shedding and the oscillation frequency can be staggered, so that the heat release driving force in the combustion area is weakened, and the circumferential modal pressure oscillation amplitude or the axial modal pressure oscillation amplitude of the full-ring combustion chamber is reduced.
In summary, the combustion chamber, the gas turbine and the method for suppressing the oscillatory combustion in the embodiment have the advantages that the combustion performance in a stable state is ensured and the oscillatory combustion boundary is widened by arranging the air inlet duct with the acoustic throttling function, so that the performances of pollution emission, outlet temperature distribution and the like of the combustion chamber are ensured; even if oscillatory combustion occurs, acoustic throttling occurs on the air inlet under the action of pressure waves, the proportion of air inflow of the first air inlet portion is reduced, the proportion of air inflow of the second air inlet portion is increased, and therefore the number of swirl flows at the outlet of the pre-combustion stage is adjusted.
Although the present invention has been disclosed in the above-mentioned embodiments, it is not intended to limit the present invention, and those skilled in the art may make variations and modifications without departing from the spirit and scope of the present invention. Therefore, any modification, equivalent change and modification of the above embodiments according to the technical essence of the present invention are within the protection scope defined by the claims of the present invention, unless the technical essence of the present invention departs from the content of the present invention.
Claims (10)
1. A combustion chamber of a gas turbine, the combustion chamber comprising a liner head, the head comprising a main combustion stage and a pre-combustion stage, centered on the pre-combustion stage, a plurality of the main combustion stages being distributed circumferentially around the pre-combustion stage, the pre-combustion stage having a pre-combustion stage fuel nozzle and a pre-combustion stage outer wall circumferentially outward thereof, the main combustion stage having a main combustion stage inner wall, characterized in that,
the radial space inside the outer wall of the pre-burning stage provides a pre-burning stage channel for mixing air entering the pre-burning stage through an air inlet part of the pre-burning stage with fuel injected by a fuel nozzle of the pre-burning stage;
the pre-combustion stage air inlet part comprises a pre-combustion stage first air inlet part and a pre-combustion stage second air inlet part; the precombustion stage first air intake includes a second orifice having an acoustic throttling effect through a radial thickness of the precombustion stage outer wall.
2. The combustion chamber as set forth in claim 1, wherein said second port having an acoustic throttling effect is configured to:
wherein, P'4Is the amplitude of the pulsating pressure in the flame tube, P4Is the mean pressure, Δ P, in the flame tubeoriThe constant beta is the energy conversion efficiency of converting the acoustic energy of the second duct into kinetic energy for the via hole pressure drop of the acoustic orifice.
3. The combustion chamber of claim 1, wherein the second intake portion has a second intake passage provided by a radial space between the outer wall of the pre-combustion stage and an outer wall of a pre-combustion stage fuel nozzle, and a swirler is disposed in the second intake passage.
4. The combustor of claim 1, wherein the first inlet portion and the second inlet portion of the precombustion stage independently supply air to the precombustion stage passage, and the air supplied from the first inlet portion and the second inlet portion is mixed in the precombustion stage passage.
5. The combustor of claim 4, wherein said second port axis is parallel to a radial direction.
6. The combustor of claim 4, wherein the axis of said second port is inclined to the radial direction in either a positive or negative direction.
7. The combustor of claim 1, wherein said pre-stage fuel nozzle is a centrifugal nozzle.
8. A combustion chamber of a gas turbine, the combustion chamber comprising a liner head, the head comprising a main combustion stage and a pre-combustion stage, air for mixing with fuel injected from a pre-combustion stage fuel nozzle entering the pre-combustion stage through a pre-combustion stage intake, the combustion chamber comprising a steady state and a oscillatory combustion state, the combustion chamber being characterized in that the pre-combustion stage intake comprises a pre-combustion stage first intake and a pre-combustion stage second intake, the pre-combustion stage first intake having a second port, in the steady state air can enter the pre-combustion stage through the pre-combustion stage first intake and the pre-combustion stage second intake, respectively, in the oscillatory combustion state the pre-combustion stage first intake has a throttling effect on the second port under an oscillatory combustion environment propagating through a liner cavity of the combustion chamber, such that a proportion of air entering the pre-combustion stage through the pre-combustion stage first intake is reduced, the proportion of air entering the pre-combustion stage through the second air inlet part of the pre-combustion stage is increased, and the swirl number of the outlet of the pre-combustion stage is adjusted.
9. A gas turbine comprising a combustor according to any one of claims 1 to 8.
10. A method of suppressing a screech combustion of a gas turbine, comprising:
a plurality of air flow paths are arranged to provide air for the pre-combustion stage of the combustion chamber;
in a steady state, the plurality of air flow paths provide air to the precombustion stage;
in an oscillatory combustion state, the throttling action generated by one air flow path of the multiple air flow paths under the environment of oscillatory pressure waves propagated by a flame tube cavity of the combustion chamber enables the proportion of the air flow path to be reduced, the proportion of the air flow of other air flow paths in the multiple air flow paths is correspondingly increased, and the number of swirl at the outlet of the precombustion stage is adjusted.
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| CN112066412B (en) | 2022-03-29 |
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