CN115143488B - Unstable combustion control method and system for air heater - Google Patents
Unstable combustion control method and system for air heater Download PDFInfo
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- CN115143488B CN115143488B CN202210769628.2A CN202210769628A CN115143488B CN 115143488 B CN115143488 B CN 115143488B CN 202210769628 A CN202210769628 A CN 202210769628A CN 115143488 B CN115143488 B CN 115143488B
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- 238000002485 combustion reaction Methods 0.000 title claims abstract description 226
- 238000000034 method Methods 0.000 title claims abstract description 27
- 238000002347 injection Methods 0.000 claims abstract description 44
- 239000007924 injection Substances 0.000 claims abstract description 44
- 230000010355 oscillation Effects 0.000 claims description 24
- 239000000446 fuel Substances 0.000 claims description 10
- 239000007800 oxidant agent Substances 0.000 claims description 9
- 230000001590 oxidative effect Effects 0.000 claims description 9
- 238000004458 analytical method Methods 0.000 claims description 7
- 238000009792 diffusion process Methods 0.000 claims description 5
- 230000005284 excitation Effects 0.000 description 15
- 238000004364 calculation method Methods 0.000 description 8
- 239000011521 glass Substances 0.000 description 7
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 4
- 239000001301 oxygen Substances 0.000 description 4
- 229910052760 oxygen Inorganic materials 0.000 description 4
- 239000000243 solution Substances 0.000 description 4
- 230000000694 effects Effects 0.000 description 3
- 238000010183 spectrum analysis Methods 0.000 description 3
- 230000033228 biological regulation Effects 0.000 description 2
- 230000008878 coupling Effects 0.000 description 2
- 238000010168 coupling process Methods 0.000 description 2
- 238000005859 coupling reaction Methods 0.000 description 2
- 239000002737 fuel gas Substances 0.000 description 2
- 239000007788 liquid Substances 0.000 description 2
- 238000005259 measurement Methods 0.000 description 2
- 239000003380 propellant Substances 0.000 description 2
- 230000010349 pulsation Effects 0.000 description 2
- 238000004088 simulation Methods 0.000 description 2
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000009530 blood pressure measurement Methods 0.000 description 1
- 238000004891 communication Methods 0.000 description 1
- 230000008602 contraction Effects 0.000 description 1
- 230000008094 contradictory effect Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 230000003993 interaction Effects 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 230000035772 mutation Effects 0.000 description 1
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- 238000001228 spectrum Methods 0.000 description 1
- 239000007921 spray Substances 0.000 description 1
- 239000013589 supplement Substances 0.000 description 1
- 230000001629 suppression Effects 0.000 description 1
- 238000011144 upstream manufacturing Methods 0.000 description 1
- 230000010356 wave oscillation Effects 0.000 description 1
Classifications
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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
- F23R3/16—Continuous combustion chambers using liquid or gaseous fuel characterised by the air-flow or gas-flow configuration with devices inside the flame tube or the combustion chamber to influence the air or gas 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
- F23R3/286—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
- F23R3/42—Continuous combustion chambers using liquid or gaseous fuel characterised by the arrangement or form of the flame tubes or combustion chambers
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- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Combustion & Propulsion (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Control Of Combustion (AREA)
Abstract
The invention belongs to the field of combustion control of combustion chambers, and particularly relates to a combustion instability control method and system of an air heater, wherein the method comprises the following steps: acquiring sound wave conditions in a combustion chamber of the air heater; according to the sound wave condition in the air heater combustion chamber, the sound wave transmitting device transmits the active intervention sound wave with the same or multiple frequency and opposite phase to the sound wave in the air heater combustion chamber to the air heater combustion chamber, and at least one sound wave transmitting device transmits the active intervention sound wave along the injection mixing section of the air heater combustion chamber to the combustion section direction.
Description
Technical Field
The invention belongs to the field of combustion control of combustion chambers, and particularly relates to a combustion instability control method and system of an air heater.
Background
The air heater is a key device for high-speed aircraft and a high-altitude simulation test of a propulsion system of the high-speed aircraft, and is used for simulating the total enthalpy, total pressure, mach number, oxygen component in the air and other flight parameters when the aircraft actually flies. The air heater uses a liquid rocket engine technology, provides heat through fuel combustion, supplements oxygen to mix high-temperature fuel gas with normal-temperature air and discharges the mixture through a Laval nozzle, so as to obtain high-speed hot air with the same oxygen content as the air and uniform flow field quality. In the working process of the air heater, high-frequency combustion instability caused by factors such as disturbance of an internal flow field, turbulent combustion pulsation and the like occurs due to the coupling of the combustion reaction of the combustion chamber propellant and the acoustic characteristics of the combustion chamber, so that the combustion efficiency and the safety of the air heater are mainly affected.
Although there is a study on the control of the thermo-acoustic instability of the burner by means of a loudspeaker, the coupling between the heat release and the sound pressure is broken mainly by changing the acoustic boundary conditions of the combustion system, and the suppression mode is single, so that the combustion instability in the combustion section can be suppressed only.
Disclosure of Invention
The invention aims to provide an air heater combustion instability control method and system based on active acoustic excitation, which can improve combustion efficiency, eliminate combustion instability and avoid flame backflow.
The invention provides a combustion instability control method of an air heater, which comprises the following steps:
Acquiring sound wave conditions in a combustion chamber of the air heater;
And according to the condition of sound waves in the air heater combustion chamber, actively intervening sound waves with the same or multiple frequency and opposite phase to the sound waves in the air heater combustion chamber are emitted into the air heater combustion chamber through the sound wave emission device, and at least one sound wave emission device emits the actively intervening sound waves along the injection mixing section of the air heater combustion chamber towards the combustion section.
Still further, the acquiring the acoustic wave condition in the combustion chamber of the air heater includes: the method comprises the steps of acquiring the attribute of sound waves in a combustion chamber of an air heater and the distribution condition of the sound waves, wherein the sound wave transmitting device selects active intervention sound waves with proper frequency and phase according to the attribute of the sound waves, and the sound wave transmitting device selects proper transmitting positions and transmitting directions according to the distribution condition of the sound waves to transmit the active intervention sound waves.
Further, the active intervention sound waves emitted along the injection mixing section in the air heater combustion chamber towards the combustion section are emitted parallel or oblique to the air heater combustion chamber axis.
Further, at least two sound wave emitting devices emit the active intervention sound waves to the direction of the combustion section along the injection mixing section in the combustion chamber of the air heater, and the at least two sound wave emitting devices are symmetrically distributed along the axis of the combustion chamber of the air heater.
Still further, the method further comprises: and acquiring the sound wave condition in the combustion chamber of the air heater after the active intervention sound wave intervention, and changing the frequency, the phase, the direction and the position of the sound wave transmitting device for transmitting the active intervention sound wave according to the sound wave condition in the combustion chamber of the air heater after the active intervention sound wave intervention.
The invention also provides an air heater combustion instability control system, which comprises an air heater combustion chamber, an acoustic wave emission device and an acoustic wave acquisition and analysis assembly, wherein the air heater combustion chamber is sequentially divided into an injection mixing section, a combustion section and an outlet section, and the acoustic wave emission device comprises loudspeakers which are arranged along the direction from the injection mixing section to the combustion section.
Still further, the injection panel of air heater combustion chamber or the lateral wall of air heater near the injection mixing section side is provided with the speaker mounting port, speaker embedding speaker mounting port sets up.
Still further, the acoustic wave emitting device further includes a speaker disposed at a position of the air heater near the combustion section.
The beneficial effects of the invention are as follows:
firstly, the invention improves the combustion efficiency of the air heater by actively intervening at least one injection mixing section of the sound wave passing through the combustion chamber of the air heater and promoting the mixing of fuel and oxidant near the nozzle by the sound wave, and simultaneously changes the diffusion flame into the premixed flame to further improve the combustion stability of the air heater;
Secondly, after the active intervention sound wave enters the combustion section from the injection mixing section, the active intervention sound wave has the same frequency or a frequency which is multiplied by the sound wave in the combustion chamber of the air heater and opposite in phase, so that combustion oscillation can be avoided, and the combustion stability of flame in the combustion chamber of the air heater is improved;
Thirdly, actively intervening sound waves pass through the injection mixing section, so that combustion flame near the injection mixing section is pushed to the direction of the combustion section, and the problems that the inner wall surface of an injection panel and the inner wall surface of a combustion chamber of an air heater are burnt out by flame backflow are avoided;
The invention adopts non-contact acoustic excitation on the premise of not changing the structure of the combustion chamber of the air heater and not changing the conveying modes of fuel and oxidant, so that the combustion efficiency can be improved, the unstable combustion can be eliminated, the flame backflow can be avoided, and the working efficiency and the safety of the air heater can be effectively improved.
Drawings
FIG. 1 is a schematic view of a rectangular cross-section air heater with a glass viewing window according to the present invention;
FIG. 2 is a front view of a rectangular cross-section air heater with a glass viewing window according to the present invention;
FIG. 3 is a front cross-sectional view of a rectangular cross-section air heater according to the present invention;
FIG. 4 is a typical air heater combustion chamber pressure time history;
FIG. 5 shows FFT results for air heater combustion chamber pressures between 23.5 and 24.7 seconds;
fig. 6 is a temperature field distribution on the z=0 plane calculated by CFD numerical calculation;
FIG. 7 is a comparison of the numerical calculation of the temperature field with the high-speed photographic result;
FIG. 8 is a schematic diagram of the active acoustic excitation coordinates of an air heater combustion chamber;
FIG. 9 is an average temperature field at different excitation amplitudes.
In the figure, 1-air heater combustion chamber; 11-injecting the mixing section; 12-a combustion section; 13-an outlet section; 14-glass viewing window; 15-speaker mounting port; 16-injecting a panel; 2-nozzles; 3-a pressure sensor; 4-speakers.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and fully with reference to the accompanying drawings, in which it is evident that the embodiments described are only some, but not all embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
It should be noted that all directional indicators (such as up, down, left, right, front, and rear … …) in the embodiments of the present invention are merely used to explain the relative positional relationship, movement, etc. between the components in a particular posture (as shown in the drawings), and if the particular posture is changed, the directional indicator is changed accordingly.
Furthermore, descriptions such as those referred to as "first," "second," and the like, are provided for descriptive purposes only and are not to be construed as indicating or implying a relative importance or implying an order of magnitude of the indicated technical features in the present disclosure. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include at least one such feature. In the description of the present invention, the meaning of "plurality" means at least two, for example, two, three, etc., unless specifically defined otherwise.
In the present invention, unless specifically stated and limited otherwise, the terms "connected," "affixed," and the like are to be construed broadly, and for example, "affixed" may be a fixed connection, a removable connection, or an integral body; the device can be mechanically connected, electrically connected, physically connected or wirelessly connected; either directly or indirectly, through intermediaries, or both, may be in communication with each other or in interaction with each other, unless expressly defined otherwise. The specific meaning of the above terms in the present invention can be understood by those of ordinary skill in the art according to the specific circumstances.
In addition, the technical solutions of the embodiments of the present invention may be combined with each other, but it is necessary to be based on the fact that those skilled in the art can implement the technical solutions, and when the technical solutions are contradictory or cannot be implemented, the combination of the technical solutions should be considered as not existing, and not falling within the scope of protection claimed by the present invention.
As shown in fig. 1 to 9, the present invention provides a combustion instability control method of an air heater, comprising:
Acquiring sound wave conditions in the combustion chamber 1 of the air heater;
According to the sound wave condition in the air heater combustion chamber 1, the active intervention sound wave with the same frequency or multiple frequency and opposite phase to the sound wave in the air heater combustion chamber 1 is emitted into the air heater combustion chamber 1 through a sound wave emitting device, and at least one sound wave emitting device emits the active intervention sound wave along the injection mixing section 11 of the air heater combustion chamber 1 towards the combustion section 12.
According to the invention, the sound wave condition in the air heater combustion chamber 1 is obtained, and the active intervention sound wave is emitted into the air heater combustion chamber 1 through the sound wave emitting device according to the sound wave condition, and at least one sound wave emitting device emits the active intervention sound wave along the injection mixing section 11 of the air heater combustion chamber 1 towards the combustion section 12, wherein the active intervention sound wave firstly passes through the injection mixing section 11 and promotes the mixing of fuel and oxidant near the nozzle 2 through the sound wave, so that the combustion efficiency of the air heater is improved, and meanwhile, the molecular movement of the fuel and the oxidant is accelerated due to the sound wave effect, so that the initial mixing speed and efficiency are improved, the mixing is changed from diffusion mixing into premixing trend, and finally the diffusion flame is changed into premixed flame, so that the combustion stability of the air heater is further improved;
Because the propellant combustion reaction in the combustion section 12 is coupled with the acoustic characteristics of the air heater combustion chamber 1, factors such as flow field disturbance, turbulent combustion pulsation and the like in the air heater combustion chamber 1 can be caused, so that combustion instability is formed, and the active intervention sound wave emitted by the invention is the same frequency or multiple frequency as the sound wave in the air heater combustion chamber 1 and opposite in phase after entering the combustion section 12 from the injection mixing section 11, so that combustion oscillation can be avoided, and the stability of flame combustion in the air heater combustion chamber 1 is further improved;
in addition, the active intervention sound wave firstly passes through the injection mixing section 11, so that combustion flame close to the injection mixing section 11 is pushed to the direction of the combustion section 12, flame backflow is avoided, the problem that the inner wall surface of the injection panel 16 and the inner wall surface of the air heater combustion chamber 1 are easily burnt out due to overlarge heat load because hot fuel gas and backflow flame near the nozzle 2 of the current injection mixing section 11 are closer to the inner wall surface of the injection panel 16 and the inner wall surface of the air heater combustion chamber 1 is solved, and particularly when the air heater is unstable in combustion, the burning probability of the inner wall surface of the injection panel 16 and the inner wall surface of the air heater combustion chamber 1 is larger;
The invention adopts non-contact acoustic excitation on the premise of not changing the structure of the combustion chamber 1 of the air heater and not changing the conveying modes of fuel and oxidant, thereby improving the combustion efficiency, eliminating unstable combustion, avoiding flame backflow and effectively improving the working efficiency and safety of the air heater.
In one embodiment, the acquiring acoustic wave conditions within the air heater combustion chamber 1 comprises: the properties of the sound wave and the distribution of the sound wave in the air heater combustion chamber 1 are acquired.
The attribute of the acquired sound wave is the sound wave attribute selected for the sound wave transmitting device to transmit the active intervention sound wave, so that the transmitted active intervention sound wave and the sound wave in the combustion chamber 1 of the air heater are ensured to be in the same or double frequency and opposite in phase, and the unstable combustion condition of the combustion section 12 can be solved after the active intervention sound wave passes through the combustion section 12;
specifically, acquiring the properties of the acoustic wave in the air heater combustion chamber 1 includes: the high-frequency pressure oscillation in the middle of the air heater combustion chamber 1 is measured by adopting the pressure sensor 3, a pressure time history curve in the air heater combustion chamber 1 is obtained after a plurality of hot test runs, an oscillation main frequency is obtained after spectrum analysis, and the spectrum analysis adopts fast Fourier transform, and peak points on a frequency spectrum are correspondingly the oscillation main frequency as shown in fig. 5.
The distribution of the sound waves is obtained in order to determine the position of the sound waves in the air heater combustion chamber 1, so that the active intervention sound waves with the same or multiple frequency and opposite phase to the sound waves in the air heater combustion chamber 1 can be accurately emitted, and the situation that the active intervention sound waves influence stable combustion flame in the air heater combustion chamber 1 can be avoided.
The acquisition of the distribution of sound waves in the air heater combustion chamber 1 comprises: when an air heater is subjected to thermal test, a high-speed camera is adopted to record flame disturbance forms from a glass window of a combustion chamber 1 of the air heater; and obtaining the temperature field distribution condition of the air heater combustion chamber 1 by adopting a numerical value meter method, and combining experimental observation and numerical value calculation to jointly judge the position of the high-frequency oscillation. Specifically, numerical calculation and temperature field distribution are mainly calculated by using Fluent software and adopting Large Eddy Simulation (LES); the experimental observation mainly adopts a high-speed camera to observe and record flame disturbance forms. The disturbance form is related to the distribution of the temperature field, the disturbance form and the temperature field are combined, and the position where the oscillation is located is obtained by combining the increasing position of the disturbance with the mutation position of the temperature field.
In one embodiment, the active intervention sound waves emitted along the direction of the injection mixing section 11 towards the combustion section 12 inside the air heater combustion chamber 1 are emitted parallel or inclined to the axis of the air heater combustion chamber 1, improving the mixing effect of the fuel and the oxidant near the nozzle 2 and improving the effect of avoiding backflow.
At least two sound wave emitting devices emit the active intervention sound waves to the direction of a combustion section 12 along the injection mixing section 11 in the air heater combustion chamber 1, and at least two sound wave emitting devices are symmetrically distributed along the axis of the air heater combustion chamber 1, so that the uniform and stable combustion of all parts in the air heater combustion chamber 1 is ensured, and the overall combustion stability is ensured.
The combustion instability control method of the air heater further comprises the following steps: the method comprises the steps of acquiring the sound wave condition in the air heater combustion chamber 1 after the active intervention sound wave intervention, changing the frequency, the phase, the direction and the position of the sound wave emitted by the sound wave emitting device to actively intervene the sound wave according to the sound wave condition in the air heater combustion chamber 1 after the active intervention sound wave intervention, acquiring the sound wave condition in the air heater combustion chamber 1 after the active intervention sound wave intervention, judging whether the combustion instability condition is eliminated or not, and if not, controlling the combustion instability again by adjusting the frequency, the phase, the direction and the position of the sound wave emitted by the sound wave emitting device according to the sound wave collecting condition, so as to realize closed loop control until the combustion instability is completely eliminated. The embodiment greatly improves the success rate of unstable combustion control.
The invention also provides an air heater combustion instability control system, which comprises an air heater combustion chamber 1, an acoustic wave emitting device and an acoustic wave acquisition and analysis assembly, wherein the acoustic wave acquisition and analysis assembly is used for acquiring acoustic wave conditions in the air heater combustion chamber 1, in the embodiment, the acoustic wave acquisition and analysis can accurately acquire the attribute of acoustic waves and the distribution condition of the acoustic waves, the requirements can be met, the specific acquisition mode and the acquisition equipment are not excessively limited, the air heater combustion chamber 1 is sequentially divided into an injection mixing section 11, a combustion section 12 and an outlet section 13, and the acoustic wave emitting device comprises loudspeakers 4 which are arranged along the direction from the injection mixing section 11 to the combustion section 12.
The unstable control system of the air heater can realize the unstable control method of the air heater, so that the combustion efficiency can be improved, the unstable combustion can be eliminated, the flame backflow can be avoided, and the working efficiency and the safety of the air heater can be effectively improved on the premise that the structure of the combustion chamber 1 of the air heater is not changed and the conveying mode of fuel and oxidant is not changed.
The injection panel 16 of the air heater combustion chamber or the side wall of the air heater close to one side of the injection mixing section 11 is provided with a speaker mounting opening 15, and the speaker 4 is embedded into the speaker mounting opening 15, so that the mounting of the speaker 4 can be simplified and the loss of the speaker 4 can be reduced.
The sound wave emitting device also comprises a loudspeaker 4 arranged at the position of the air heater close to the combustion section 12, and can be used for precisely controlling the unstable condition in the combustion section 12.
In one embodiment:
Taking the structure of the air heater as shown in fig. 1 as an example, the air heater comprises an air heater combustion chamber 11 and a nozzle 2, wherein the air heater combustion chamber 11 is divided into an injection mixing section 11, a combustion section 12 and an outlet section 13, the nozzle 2 adopts a coaxial direct-current nozzle 2, the nozzle 2 is not retracted, a loudspeaker 4 is arranged in the air heater combustion chamber 1 and on the injection panel 16 and the side wall, in addition, the cross section of the air heater combustion chamber 1 is preferably rectangular, and the specific disclosure of the air heater is shown in table 1.
TABLE 1
In this embodiment, a pressure sensor 3 with a sampling frequency of 5kHz is used to measure high-frequency pressure oscillations, with a pressure measurement point in the middle of the combustion section 12.
The partial steps of the combustion instability control method of the air heater comprise:
S1: a plurality of speaker mounting openings 15 are symmetrically arranged on the injection panel 16 of the air heater combustion chamber 1, a plurality of speaker mounting openings 15 are symmetrically arranged on the upper end surface and the lower end surface of the rectangular combustion chamber, when active acoustic excitation is carried out, a proper speaker 4 can be selected to be mounted on the proper speaker mounting opening 15 according to unstable combustion conditions, and the speaker mounting position, the direction and the working mode are set;
s2, frequency measurement: measuring high-frequency pressure oscillation by adopting a pressure sensor 3, wherein a pressure measuring point is arranged in the middle of the air heater combustion chamber 1, obtaining a pressure time history curve of the air heater combustion chamber 1 after a plurality of air heater hot test runs are completed, and obtaining an oscillation main frequency after spectrum analysis;
Specifically, the air heater hot test was performed to obtain the sonic frequency, and a total of 19 hot tests were performed in this example, in which 16 tests showed a large amplitude oscillation, and a typical pressure time history when the air heater hot test showed unstable combustion is shown in fig. 4. As can be seen from the figure, the air heater combustion chamber 1 pressure is subject to a large oscillation with an amplitude of 34.7% of the average value. After analysis of the pressure time history of the air heater combustion chamber 11 shown in fig. 4 between 23.5 and 24.7s, FFT (fast fourier transform) results below 2.5kHz shown in fig. 5 were obtained, with a time interval of the FFT analysis between 23.5 and 24.7s. From the FFT results, it can be seen that the unstable frequency peaks are 427.2Hz,1112Hz,1322Hz and 1570Hz, and therefore the sound emission frequency of the loudspeaker 4 is preferably in the range of 1000Hz to 5000 Hz. The front end of the loudspeaker 4 is connected with a power amplifier, so that the regulation and control of amplitude can be realized, and the amplitude regulation and control range is as follows: 0m/s-100m/s. The main frequencies of these oscillations correspond to oscillation modes of 1L,1T 1L,2T, respectively (L represents longitudinal oscillation, T represents tangential oscillation).
S3, judging the oscillation position: the high-frequency oscillation generation position can be determined by experimental observation in combination with numerical calculation. The method comprises the steps that a high-speed camera is adopted to record flame disturbance forms from a glass window when an air heater is used for hot trial run; the temperature field distribution condition of the combustion chamber is obtained by adopting a numerical value meter method, experimental observation and numerical calculation are combined, the position where high-frequency oscillation is located is judged, specifically, a CFD numerical value calculation method is adopted, the temperature field on a1 Z=0 plane (the Z=0 plane is a symmetry plane of a rectangular heater and is shown in an upper left corner coordinate system of fig. 1) of the combustion chamber of the air heater when the particle size of injected liquid drops is 10 mu m is obtained, and a remarkable temperature field asymmetric area caused by unstable high-frequency combustion exists as shown in fig. 6. The appearance of the local temperature field obtained by CFD numerical calculation is compared with the temperature field obtained by high-speed photographing of the glass observation window 14, as shown in fig. 7, and the flame shows an asymmetric phenomenon about the z=0 plane.
S4, active acoustic excitation: on the basis of the above frequency measurement and position determination, a speaker 4 having the same or a multiple frequency as the main frequency of vibration is selected and placed in the speaker mounting port 15 in the vicinity of the oscillation disturbance position. When the heater works, the loudspeaker 4 is started to generate active acoustic excitation; specifically, the coordinate orientation of the air heater combustion chamber 11 used in this embodiment is schematically shown in fig. 8, and the 0 point position, i.e., the nozzle contraction section, is the start position. The loudspeaker 4 is arranged in the front mounting port of the air heater combustion chamber 11, and the front end of the loudspeaker 4 is connected with the power amplifier, so that the amplitude adjustment can be realized. The method adopts a frequency multiplication mode, selects the excitation frequency of f=2685 Hz, and compares the flame structure when the excitation amplitude v' =15, 30 and 50m/s in the excitation area of [ -0.348m, -0.174m ]. As shown in fig. 9, it can be seen that the acoustic excitation promotes mixing between air/oxygen/alcohol vapor in the vicinity of the nozzle 2, changing the combustion flame structure, and as the excitation amplitude increases, the diffusion flame characteristics gradually disappear, the combustion flame moving upstream of the air heater combustion chamber 1, i.e., the combustion section 12, and the temperature field distribution in the acoustic excitation direction is more uniform downstream of the air heater combustion chamber 1, i.e., the combustion section 12. It can be stated that the control of the unstable high-frequency combustion of the air heater can be realized by adopting an active acoustic excitation method, and the phase selection of the active intervention sound wave is counteracted by the position of the loudspeaker 4 according to the first-order and second-order vibration modes. For example, the transverse oscillation is placed on the wall, the longitudinal oscillation is placed at the nozzle, and in this embodiment, the active intervention sound wave is emitted along the injection mixing section 11 of the air heater combustion chamber towards the combustion section 12, so that the mixing of the fuel and the oxidant is mainly promoted, the backflow is avoided, and the first-order longitudinal sound wave oscillation in the combustion section 12 can be eliminated.
S5: closed loop control: and judging whether the high-frequency combustion instability is eliminated or not according to the flame form observed by the glass observation window 14 and the frequency signal detected by the pressure sensor 3. And performing closed-loop control by adjusting the frequency, action direction and sound intensity of the generated sound of the loudspeaker through the secondary acquired combustion unstable frequency and oscillation position until the high-frequency combustion instability is completely eliminated.
The speakers 4 may be symmetrically disposed on the upper and lower end surfaces of the injection panel 16 and the square combustion chamber, or may be disposed on one surface alone, or may be disposed asymmetrically on both end surfaces. The number and the positions of single-side placement are determined by the combustion disturbance form. The direction of the loudspeaker can be perpendicular to the wall surface of the combustion chamber 1 of the air heater or inclined to the direction of the spray pipe 2 at a certain angle with the wall surface. The loudspeaker 4 works in a pulse mode, such as in the initial stage of combustion, eliminating unstable ignition; continuous operation is also possible, such as during steady state combustion; there may be two modes, such as a speaker 4 placed at the front end of the air heater combustion chamber 1 is pulsed on at the time of ignition, and a speaker 4 in the middle of the air heater combustion chamber 1 is started at the time of steady combustion.
What is not described in detail in this specification is prior art known to those skilled in the art.
Claims (8)
1. A combustion instability control method of an air heater, characterized by comprising:
Acquiring sound wave conditions in a combustion chamber of the air heater;
According to the condition of sound waves in the air heater combustion chamber, active intervention sound waves with the same or multiple frequency and opposite phase to the sound waves in the air heater combustion chamber are emitted into the air heater combustion chamber through a sound wave emission device, at least one sound wave emission device emits the active intervention sound waves to the combustion section direction along an injection mixing section of the air heater combustion chamber, and at least one axis of the active intervention sound waves emitted by the sound wave emission device is not coaxial with the axis of the nozzle;
The active intervention sound wave emitted from the injection mixing section of the air heater combustion chamber to the combustion section firstly passes through the injection mixing section, the mixing of fuel and oxidant near the nozzle is promoted by the sound wave, the diffusion flame is changed into the premixed flame, the flame backflow is avoided, the active intervention sound wave enters the combustion section after passing through the injection mixing section, the combustion oscillation is restrained in the combustion section, and the flame combustion stability in the air heater combustion chamber is improved.
2. The air heater combustion instability control method of claim 1 wherein said acquiring acoustic wave conditions in the air heater combustion chamber comprises: the method comprises the steps of acquiring the attribute of sound waves in a combustion chamber of an air heater and the distribution condition of the sound waves, wherein the sound wave transmitting device selects active intervention sound waves with proper frequency and phase according to the attribute of the sound waves, and the sound wave transmitting device selects proper transmitting positions and transmitting directions according to the distribution condition of the sound waves to transmit the active intervention sound waves.
3. The method of claim 2, wherein the active intervention sound waves emitted in the direction of the combustion section along the injection mixing section within the air heater combustion chamber are emitted parallel or oblique to the air heater combustion chamber axis.
4. A combustion instability control method according to claim 3 wherein at least two of said sonic wave emitting devices emit said active intervention sonic waves in the direction of the combustion section along an injection mixing section within the combustion chamber of the air heater, and at least two of said sonic wave emitting devices are symmetrically distributed along the axis of the combustion chamber of the air heater.
5. The air heater combustion instability control method of any of claims 1-4, further comprising: and acquiring the sound wave condition in the combustion chamber of the air heater after the active intervention sound wave intervention, and changing the frequency, the phase, the direction and the position of the sound wave transmitting device for transmitting the active intervention sound wave according to the sound wave condition in the combustion chamber of the air heater after the active intervention sound wave intervention.
6. An air heater combustion instability control system, which is used for realizing the air heater combustion instability control method according to any one of claims 1-5, and comprises an air heater combustion chamber, an acoustic wave emitting device and an acoustic wave acquisition and analysis assembly, wherein the air heater combustion chamber is sequentially divided into an injection mixing section, a combustion section and an outlet section, and the acoustic wave emitting device comprises speakers arranged along the direction from the injection mixing section to the combustion section.
7. The air heater combustion instability control system of claim 6 wherein either the injection panel of the air heater combustion chamber or the side wall of the air heater adjacent to the injection mixing section is provided with a speaker mounting port into which the speaker is inserted.
8. The air heater combustion instability control system of claim 7 wherein the acoustic wave emitting device further comprises a speaker positioned in the air heater proximate the combustion section.
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| US6464489B1 (en) * | 1997-11-24 | 2002-10-15 | Alstom | Method and apparatus for controlling thermoacoustic vibrations in a combustion system |
| CN101818899A (en) * | 2009-02-02 | 2010-09-01 | 通用电气公司 | Be used for reducing the system and method for the burning dynamic change of turbine |
| CN108414231A (en) * | 2018-06-07 | 2018-08-17 | 湖南云顶智能科技有限公司 | Modular trial device for swirl flow combustion thermal acoustic oscillation characteristic research |
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| DE102004013584B4 (en) * | 2003-05-10 | 2016-01-21 | IfTA Ingenieurbüro für Thermoakustik GmbH | Method for investigating the frequency-dependent vibration behavior of a burner |
| CN207019906U (en) * | 2017-08-04 | 2018-02-16 | 浙江大学 | A kind of device for measuring turbulent burner thermoacoustic transitive relation |
| CN111043623B (en) * | 2019-12-30 | 2021-07-30 | 哈尔滨工业大学 | Method for preventing combustion chamber from generating resonance based on closed-loop negative feedback regulation of electric field influencing flame root |
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Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6464489B1 (en) * | 1997-11-24 | 2002-10-15 | Alstom | Method and apparatus for controlling thermoacoustic vibrations in a combustion system |
| CN101818899A (en) * | 2009-02-02 | 2010-09-01 | 通用电气公司 | Be used for reducing the system and method for the burning dynamic change of turbine |
| CN108414231A (en) * | 2018-06-07 | 2018-08-17 | 湖南云顶智能科技有限公司 | Modular trial device for swirl flow combustion thermal acoustic oscillation characteristic research |
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