A device and method for suppressing combustion hot-sonic oscillation in advance by plasma jet

Abstract

The application discloses a kind of plasma jet advanced active inhibition combustion thermoacoustic oscillation device, belongs to industrial combustion technical field, including combustion thermoacoustic oscillation signal advanced acquisition unit and plasma jet inhibition unit;The combustion thermoacoustic oscillation signal advanced acquisition unit includes several photomultiplier tubes;Photomultiplier tube is installed on the side wall of combustion chamber, is located above flame, monitors flame heat release rate pulsation;The plasma jet inhibition unit includes plasma generator and several plasma torches;Plasma generator is connected with several plasma torches, and active particle generated by plasma generator and compressed gas form plasma jet through plasma torch;Plasma jet enters combustion chamber, and is contacted with oscillating flame front, and combustion thermoacoustic oscillation is inhibited.The application can perceive thermoacoustic oscillation in advance, and thermoacoustic oscillation is inhibited in advance in the budding stage before destruction is generated.

Description

Technical Field

[0001] This invention belongs to the field of industrial combustion technology, and relates to a combustion auxiliary device, particularly to a plasma jet-based active suppression device for combustion thermoacoustic oscillation and its suppression method. Background Technology

[0002] Industrial burners typically employ premixed combustion chambers with compact structures and high load regulation ratios. However, the complex flame-sound-flow coupling within these chambers can lead to thermoacoustic oscillations. These oscillations pose the greatest safety hazard in the premixed combustion process, severely impacting the safe and reliable operation of the combustion equipment. Therefore, proactive control of combustion thermoacoustic oscillations is crucial for ensuring stable operation of industrial burners over a wide range of conditions.

[0003] Most existing active control systems for thermoacoustic oscillations are based on pressure signals, which are indirect signals and cannot directly reflect the source term of thermoacoustic oscillations—the change in the flame heat release rate. Furthermore, most existing active control systems for thermoacoustic oscillations employ methods with significant time delays, such as fuel injection and acoustic excitation. While these methods effectively suppress thermoacoustic oscillations, they also add delays of tens or even hundreds of milliseconds. By the time the pressure sensor detects an abnormal sound pressure signal in the combustion chamber, thermoacoustic oscillations have already occurred or are about to be fully triggered within milliseconds. In reality, combustion thermoacoustic oscillations also exhibit hysteresis and nonlinear characteristics. If the limiting cycle of thermoacoustic oscillations fully forms, the destructiveness and control difficulty increase significantly.

[0004] In addition, conventional active control methods for thermoacoustic oscillations often use acoustic excitation, which not only has a long control process delay but is also often difficult to apply to actual industrial combustion scenarios. Summary of the Invention

[0005] To address the aforementioned problems, this invention provides a plasma jet-based proactive suppression device and method for combustion thermoacoustic oscillations. This device not only suppresses combustion thermoacoustic oscillations but also inhibits them at the initial stage before they are fully triggered and cause resonance damage.

[0006] To achieve the above objectives, this invention provides a plasma jet-based active suppression device for combustion thermoacoustic oscillation, used to control the flame within a burner. The burner comprises a gas premixing section, a combustion chamber, and a flue gas exhaust channel connected in sequence. It features a combustion thermoacoustic oscillation signal advance acquisition unit and a plasma jet suppression unit. The advance acquisition unit includes several photomultiplier tubes (PMTs). These PMTs are mounted on the side wall of the combustion chamber, above the flame, and monitor the pulsation of the flame's heat release rate. The plasma jet suppression unit includes a plasma generator and several plasma nozzles. The plasma generator is connected to the plasma nozzles, and the active particles generated by the plasma generator react with compressed gas to form a plasma jet. The plasma jet enters the combustion chamber and contacts the oscillating flame front, thus suppressing the combustion thermoacoustic oscillation.

[0007] Furthermore, the present invention provides a plasma jet advanced active suppression combustion thermoacoustic oscillation device, which may also have the following features: the device further includes an active controller; the active controller receives data collected by a photomultiplier tube and controls the plasma jet to enter the combustion chamber according to the collected data.

[0008] Furthermore, the present invention provides a plasma jet advanced active suppression combustion thermoacoustic oscillation device, which may also have the following features: wherein the plasma jet suppression unit further includes a gas storage tank and a gas flow meter; the gas storage tank is connected to the plasma spray gun through a pipeline to provide compressed air; the gas flow meter is installed on the pipeline between the gas storage tank and the plasma spray gun.

[0009] Furthermore, the present invention provides a plasma jet advanced active suppression combustion thermoacoustic oscillation device, which may also have the following features: wherein the device further includes a phase synchronizer; the active controller is connected to the phase synchronizer, and the phase synchronizer is connected to the plasma generator and the gas flow meter respectively; the active controller controls the plasma generator and the gas flow meter to form a plasma jet through the phase synchronizer.

[0010] Furthermore, the present invention provides a plasma jet advanced active suppression device for combustion thermoacoustic oscillation, which may also have the following features: wherein the plasma jet suppression unit further includes a probe and an oscilloscope; the probe measures the voltage and current signals of the plasma jet, and the oscilloscope monitors them in real time and transmits them to the phase synchronizer.

[0011] Furthermore, the present invention provides a plasma jet advanced active suppression combustion thermoacoustic oscillation device, which may also have the following feature: wherein the plurality of photomultiplier tubes are symmetrically arranged circumferentially on the side wall of the combustion chamber to form a photomultiplier tube array.

[0012] Furthermore, the present invention provides a plasma jet advanced active suppression combustion thermoacoustic oscillation device, which may also have the following feature: wherein the photomultiplier tube is inclined and perpendicular to the normal direction of the flame front.

[0013] Furthermore, the present invention provides a plasma jet advanced active suppression device for combustion thermoacoustic oscillation, which may also have the following features: wherein the plasma jet suppression unit further includes a plurality of quartz glass tubes; the number of quartz glass tubes is equal to the number of plasma spray guns, and they correspond one-to-one; the quartz glass tubes are fixed on the side wall of the combustion chamber, with one end inside the combustion chamber and the other end outside the combustion chamber, and connected to the corresponding plasma spray gun; the plasma jet generated by the plasma spray gun enters the combustion chamber through the quartz glass tubes.

[0014] Furthermore, the present invention provides a plasma jet advanced active suppression combustion thermoacoustic oscillation device, which may also have the following features: wherein the plurality of quartz glass tubes are divided into several groups, and the plurality of quartz glass tubes in each group are arranged vertically with a height matching the height of the flame, and the plurality of groups of quartz glass tubes are arranged symmetrically along the circumference on the side wall of the combustion chamber.

[0015] The present invention also provides a suppression method for the aforementioned plasma jet advanced active suppression of thermoacoustic oscillations, characterized by the following steps: S1, a time-series signal of the flame heat release rate pulsation from a photomultiplier tube is input to an active controller; S2, the active controller performs fast Fourier analysis on the acquired time-series signal to obtain the amplitude and frequency of the flame oscillation; S3, the active controller determines whether the flame oscillation reaches the threshold for thermoacoustic oscillation excitation; if the threshold is not reached, the active controller does not generate a voltage signal for suppression; if the threshold is reached, the active controller further analyzes the amplitude and frequency of the flame oscillation and generates an analog voltage signal accordingly to control the plasma generator to generate active particles, which, together with compressed gas, generate a plasma jet through a plasma nozzle, and then repeats S1-S3.

[0016] The beneficial effects of this invention are as follows:

[0017] This invention can detect the triggering of combustion thermoacoustic oscillations in advance: In this invention, the pulse of flame heat release rate is measured by a photomultiplier tube array. In the transition time window before the complete triggering of combustion thermoacoustic oscillations, the large pulse of flame heat release rate will appear tens of milliseconds earlier than the pressure fluctuation. Therefore, the triggering of thermoacoustic oscillations can be detected in advance based on the flame heat release rate signal, thus providing the prerequisite for the early prevention and control of thermoacoustic oscillations.

[0018] This invention enables proactive suppression of combustion thermoacoustic oscillations. Active thermoacoustic oscillation control systems typically consist of sensors, controllers, and actuators. The key to solving the problem of proactive thermoacoustic oscillation prevention lies in shortening the overall delay time and efficiently suppressing the oscillations, based on proactively sensing their triggering. In this invention, the plasma jet can directly act on the flame front, representing direct combustion reaction regulation. Compared to traditional active control methods, plasma jet active control is electrically excited, offering significant advantages such as fast response (<0.1ms) and wide bandwidth (0–100kHz). Therefore, this invention can achieve proactive suppression of combustion thermoacoustic oscillations.

[0019] This invention can be applied to the thermal acoustic oscillation suppression of actual industrial burners: This invention has good flexibility and robustness. Without changing the burner geometry, it can effectively measure and control combustion thermal acoustic oscillations through a plasma jet active control system. It can be used in combustion equipment such as gas turbines, industrial boilers, rockets, and internal combustion engines.

[0020] This invention has high measurement accuracy: In this invention, an array of photomultiplier tubes perpendicular to the flame front is used to capture the pulsation of the flame heat release rate, which significantly reduces measurement error compared with the traditional single-point measurement method; at the same time, the array of photomultiplier tubes can capture the spatiotemporal pulsation of the flame heat release rate very well, and reflect the combustion thermoacoustic oscillation in a timely and effective manner.

[0021] This invention offers high control precision: using a single plasma jet excitation method can lead to problems such as weak ionization intensity and small plume cross-section. However, employing a plasma jet array excitation method can increase the processing area and control efficiency, thereby enabling more precise and efficient suppression of thermoacoustic oscillations. In this invention, multiple nanosecond pulsed plasma jets are used to suppress thermoacoustic oscillations during flame combustion. This directly alters the structure of the recirculation zones inside and outside the flame, as well as the pulsating distribution of the local flame heat release rate, thereby precisely disrupting the original thermoacoustic coupling process and achieving advanced suppression of combustion thermoacoustic oscillations. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of a plasma jet-assisted active suppression of combustion thermoacoustic oscillation.

[0023] Figure 2 This is a schematic diagram of the burner, photomultiplier tube arrangement, and jet orifice arrangement;

[0024] Figure 3 This is a schematic diagram showing the relative positions of the quartz glass tube and the flame;

[0025] Figure 4 This is a schematic diagram of the arrangement of the quartz glass tube and the jet orifice;

[0026] Figure 5 This is a schematic diagram of a photomultiplier tube measurement array;

[0027] Figure 6 This is a schematic diagram showing the relative positions of the plasma spray gun and the flame;

[0028] Figure 7 This is a schematic diagram of signal acquisition by the active controller;

[0029] Figure 8 This is a flowchart of a method for proactively suppressing combustion thermoacoustic oscillations using plasma jets;

[0030] Figure 9 This is a diagram illustrating the combustion thermoacoustic oscillation triggering mechanism.

[0031] Figure 10 This is a diagram illustrating the mechanism of proactive suppression of combustion thermoacoustic oscillations.

[0032] Figure 11 It is a timing signal diagram of the advanced sensing of combustion thermoacoustic oscillation signal;

[0033] Figure 12 The results are from fast Fourier analysis before and after the active control of combustion thermoacoustic oscillation. Detailed Implementation

[0034] The specific embodiments of the present invention will be described below with reference to the accompanying drawings.

[0035] like Figure 1 and 2 As shown, the present invention provides a plasma jet advanced active suppression combustion thermoacoustic oscillation device for controlling the flame in the burner.

[0036] The burner includes a gas premixing section 1, a combustion chamber 2, and a flue gas exhaust passage 3 connected in sequence.

[0037] The plasma jet advanced active suppression device for combustion thermoacoustic oscillation includes a combustion thermoacoustic oscillation signal advanced acquisition unit, a plasma jet suppression unit, an active controller 6, and a phase synchronizer 7.

[0038] The advanced acquisition unit for combustion thermoacoustic oscillation signals includes several photomultiplier tubes 4.

[0039] The photomultiplier tube 4 is mounted on the side wall of the combustion chamber 2, above the flame, to monitor the pulsation of the flame heat release rate. It can detect the signal of the flame heat release rate pulsation before the thermoacoustic oscillations in the combustion chamber 2 are fully triggered. The photomultiplier tube 4 is powered by a programmable DC power supply.

[0040] In a preferred embodiment, a plurality of photomultiplier tubes 4 are symmetrically arranged circumferentially on the side wall of the combustion chamber 2 to form a photomultiplier tube array.

[0041] In a preferred embodiment, the photomultiplier tube 4 is tilted, perpendicular to the normal direction of the flame front. Since the fluctuations perpendicular to the normal direction of the flame front are the most intense, this arrangement best reflects the pulsating behavior of the flame heat release rate.

[0042] The plasma jet suppression unit includes a plasma generator 51 and several plasma spray guns 52.

[0043] A plasma generator 51 is connected to several plasma spray guns 52. The active particles (plasma) generated by the plasma generator 51 and the compressed gas form a plasma jet through the plasma spray guns 52. The controlled oscillating flame is located in the combustion chamber 2. The plasma jet enters the combustion chamber 2 and comes into contact with the oscillating flame front. The periodic pulsation and folding state of the flame front are improved, and the combustion thermoacoustic oscillation is suppressed in the triggering stage before damage occurs, thus achieving advanced prevention and control of combustion thermoacoustic oscillation.

[0044] The excitation voltage, frequency, and compressed gas flow rate of the plasma jet can all be adjusted as needed. The compressed gas is supplied by the compressed gas storage tank 531 and can be non-flammable and non-explosive gases such as argon, helium, air, and nitrogen. The compressed gas flow rate is adjusted using a gas flow meter 532. The plasma jet intensity can also be adjusted. The plasma jet enters the internal and external circulation zones of the flame, thereby improving the problem of local flame heat release rate pulsation and suppressing the triggering of combustion thermoacoustic oscillations at the source.

[0045] Suppressing the triggering of combustion thermoacoustic oscillations at their source is achieved because the plasma jet entering the combustion chamber introduces flow field disturbances. These disturbances cause changes in the flame front, as well as the formation and shedding of vortices, thereby regulating the pulsation of the flame heat release rate, breaking the coupling between flame, flow, and acoustic waves, and suppressing the triggering of combustion thermoacoustic oscillations. Simultaneously, the plasma jet itself carries a large number of excited-state particles and free radicals, which can improve the chemical / physical characteristics of the flame within the combustion chamber from the source, influencing chemical reaction kinetics and temperature field distribution.

[0046] Advanced prevention refers to detecting the triggering of thermoacoustic oscillations earlier by relying on the flame heat release rate rather than the combustion chamber sound pressure, thereby reducing the delay time of the active control process. Furthermore, by using plasma jet excitation to directly act on the flame front, rather than first altering the sound waves or fuel characteristics and then indirectly changing the flame front, the delay time of the active control process can be further shortened.

[0047] Specifically, the plasma jet suppression unit also includes a gas storage tank 531 and a gas flow meter 532. The gas storage tank 531 is connected to the plasma nozzle 52 via a pipeline to supply compressed air. The gas flow meter 532 is installed on the pipeline between the gas storage tank 531 and the plasma nozzle 52. A pressure regulating valve 533 is provided at the outlet of the gas storage tank 531.

[0048] The plasma jet suppression unit also includes several quartz glass tubes 54. The number of quartz glass tubes 54 is equal to the number of plasma spray guns 52, and they correspond one-to-one. The quartz glass tubes 54 are fixed to the side wall of the combustion chamber 2, with one end inside the combustion chamber 2 and the other end outside, connected to the corresponding plasma spray gun 52. The plasma jet generated by the plasma spray gun 52 enters the combustion chamber 2 through the quartz glass tubes 54. Specifically, as... Figure 3 and 4 As shown, jet orifices are provided on the side wall at the bottom of combustion chamber 2. Quartz glass tube 54 is fixed to the bottom of combustion chamber 2 through the jet orifices. The distance between the outlet of quartz glass tube 54 and the flame front can be adjusted as needed. The inner diameter, wall thickness, and length of quartz glass tube 54 can all be adjusted according to the actual burner power and size.

[0049] In a preferred embodiment, several quartz glass tubes 54 are divided into several groups, and multiple quartz glass tubes 54 in each group are arranged vertically with a height matching the height of the flame. The several groups of quartz glass tubes 54 are symmetrically arranged circumferentially on the side wall of the combustion chamber 2. That is, the flame is located at the center of the bottom of the combustion chamber 2, and the plasma jet contacts the flame front circumferentially.

[0050] The active controller 6 receives data collected by the photomultiplier tube 4 and controls the plasma jet to enter the combustion chamber 2 based on the collected data.

[0051] The active controller 6 is connected to the phase synchronizer 7, which is connected to the plasma generator 51 and the gas flow meter 532, respectively. The active controller 6 controls the plasma generator 51 and the gas flow meter 532 to form a plasma jet through the phase synchronizer 7.

[0052] Specifically, the active controller 6 is equipped with a high-frequency dynamic data acquisition card 61 and an active control signal output card 62. Several photomultiplier tubes 4 are connected to the active controller 6 via the high-frequency dynamic data acquisition card 61, and the active controller 6 is connected to the phase synchronizer 7 via the active control signal output card 62. The voltage signals measured by the photomultiplier tubes 4 are acquired in real time by the high-frequency dynamic data acquisition card 61 via a signal transmission line. The high-frequency dynamic data acquisition card 61 acquires analog signals and outputs digital signals, which are then fed into the active controller 6. The digital signals output by the active controller 6 enter the active control signal output card 62, and under the coordinated action of the phase synchronizer 7, drive the plasma generator 51 and the gas flow meter 532 to generate a plasma jet in the plasma spray gun 52.

[0053] The plasma jet suppression unit also includes a probe and an oscilloscope. The probe measures the voltage and current signals of the plasma jet, which are monitored in real time by the oscilloscope and transmitted to the phase synchronizer 7 to ensure that the phase of the generated plasma jet is consistent with the phase of the active controller 6.

[0054] In one specific embodiment, such as Figure 2 As shown, the burner has a swirling premixing structure, with the flame located at the bottom of the combustion chamber 2. The bottom of the combustion chamber 2 has a sudden expansion design. After the plasma jet generated by the plasma spray gun 52 passes through the quartz glass tube 54, it enters the bottom of the combustion chamber 2 and comes into contact with the flame front. In order to reduce the thermal stress damage to the upper part of the combustion chamber 2 caused by high temperature, a combustion chamber water cooling device 21 is provided on the side wall of the upper part of the combustion chamber 2.

[0055] After the combustion-supporting gas enters the combustion-supporting gas inlet buffer section 11, it enters the bottom of the gas premixing section 1 through the combustion-supporting gas inlet pipe 12. The fuel gas enters the bottom of the gas premixing section 1 through the fuel gas inlet pipe 13. The combustion-supporting gas inlet pipe 12 and the fuel gas inlet pipe 13 are arranged in a cross-flow pattern at the bottom of the gas premixing section 1, thereby improving the mixing of the fuel gas and combustion-supporting gas to obtain a premixed gas and reducing flame equivalence ratio disturbance. The combustion-supporting gas is air. The fuel gas may include flammable gases such as natural gas, coal gas, methane, propane, biomass gas, and coalbed methane, as well as zero-carbon renewable gases such as hydrogen and ammonia.

[0056] The mixed combustible premixed gas first passes through the anti-backfire corrugated plate 14, then flows through the rectifier honeycomb plate 15, and is ignited at the bottom of the combustion chamber 2 under the action of the cyclone separator 16. Among them, such as... Figure 5 and 6As shown, the swirler 16 consists of multiple swirling blades, which can generate gas swirling flows of different intensities, thus stabilizing the flame. The swirling section of the burner consists of a flame disk 17, the swirler 16, and a blunt body 18. The edge of the flame disk 17 contacts the bottom of the combustion chamber 2, and the inner diameter of the flame disk 17 is smaller than the inner diameter of the lower wall of the combustion chamber 2. Both the swirler 16 and the blunt body 18 can stabilize the gas flame and prevent it from being blown out. Unburned premixed gas enters the bottom of the combustion chamber 2 and ignites, forming a premixed flame.

[0057] like Figure 7 As shown, a photomultiplier tube array composed of multiple photomultiplier tubes 4 is arranged uniformly and symmetrically at 360° to ensure comprehensive monitoring of the flame heat release rate pulsation within any angular range. To improve measurement accuracy, the number of photomultiplier tubes 4 should not be less than 6. The flame heat release rate pulsation signal from the photomultiplier tubes 4 is acquired by the high-frequency dynamic data acquisition card 61 and then enters the active controller 6. The active controller 6 is equipped with an uninterruptible power supply. The control action commands of the active controller 6 are digital signals. After being issued, the digital signals are converted into analog signals by the active control signal output card 62 and transmitted to the phase synchronizer 7. The phase synchronizer 7 issues commands, which are transmitted to the plasma generator 51 and the gas flow meter 532 respectively. The plasma generator 51 starts generating plasma, and the outlet valve of the gas flow meter 532 opens. The generated plasma enters the plasma spray gun 52. Meanwhile, the gas in the gas storage tank 531 enters the plasma jet gun 52 after passing through the pressure regulating valve 533. The pressure regulating valve 533 can adjust the compressed gas pressure as needed. The outlet of the plasma jet gun 52 carries a large number of active particles and free radicals, forming a plasma jet.

[0058] After combustion, the flue gas produced flows through the combustion chamber water cooling device 21 and is discharged from the burner through the flue gas discharge channel 3.

[0059] The active controller 6 is a real-time high-frequency controller composed of an embedded system. It has a built-in active control algorithm for advanced combustion thermoacoustic oscillation and executes a method for advanced active suppression of combustion thermoacoustic oscillation by plasma jet.

[0060] like Figure 8 As shown, the method for actively suppressing combustion thermoacoustic oscillations in advance using plasma jets is as follows:

[0061] First, the time-series signal of the flame heat release rate pulsation from the photomultiplier tube 4 is acquired by the high-frequency dynamic data acquisition card 61 and then enters the active controller 6.

[0062] Subsequently, the program built into the active controller 6 performs fast Fourier analysis on the acquired time series signal to obtain the amplitude and frequency of the flame oscillation.

[0063] Subsequently, the signal processing system of the active controller 6 determines whether the flame oscillation has reached the threshold for thermoacoustic oscillation excitation. If the threshold is not reached, the active controller 6 does not generate a voltage signal for suppression. If the threshold is reached, the active controller 6 further analyzes the amplitude and frequency of the flame oscillation to obtain the mode of combustion thermoacoustic oscillation. The active controller 6 then generates an analog voltage signal based on the specific oscillation mode. Under the action of the phase synchronizer 7, it controls the plasma generator 51 to generate active particles, which, together with compressed gas, generate a plasma jet through the plasma spray gun 52. Then, S1-S3 are repeated. That is, under the closed-loop control logic, the time sequence signal of the flame heat release rate pulsation of the photomultiplier tube 4 is used to determine whether there is still severe thermoacoustic oscillation in the combustion chamber 2. If there is no severe thermoacoustic oscillation, the active controller 6 stops operating. If severe thermoacoustic oscillation still exists, the active controller 6 continues operating until the flame oscillation in the combustion chamber 2 is suppressed.

[0064] like Figure 9 As shown, the plasma jet, through contact with the flame front, alters the structure of the flame front, as well as the formation and shedding of vortices, thereby affecting the pulsating process of the flame heat release rate. Meanwhile, as... Figure 10 As shown, the plasma jet energy band simultaneously changes the flow field, chemical reaction, and temperature field within combustion chamber 2. The plasma jet breaks the original combustion thermoacoustic oscillation coupling process, destroys the coupling of thermoacoustic oscillation, and thus suppresses the triggering of combustion thermoacoustic oscillation. This belongs to the control of the combustion reaction pathway. After the thermoacoustic oscillation is decoupled, the absolute value of the phase difference between the flame heat release rate and the sound pressure is greater than 90°.

[0065] The active control system for thermoacoustic oscillations consists of sensors, controllers, and actuators. Based on the ability to proactively detect the triggering of thermoacoustic oscillations, the key to fundamentally solving the problem of proactive prevention of thermoacoustic oscillations lies in how to shorten the overall delay time and efficiently suppress the oscillations. For example... Figure 10 As shown, by monitoring the pulsation of the flame heat release rate using a sensor (referred to as a flame heat release pulsation sensor), the combustion thermoacoustic oscillation signal within the combustion chamber 2 can be sensed and detected in advance. This invention uses a nanosecond pulsed plasma jet as an actuator, generating the plasma jet through an electrical signal. The short delay time allows it to quickly reach the combustion oscillation region. Specifically, the active control algorithm can be written using LabVIEW software and embedded into the active controller 6.

[0066] This invention, by constructing an active controller 6 based on actual physical processes, can further shorten the overall delay time of the active control system and suppress thermoacoustic oscillations within the transition zone before full triggering. First, the triggering of thermoacoustic oscillations can be detected in advance based on the flame heat release rate. Second, a plasma jet is used to directly act on the flame, rather than first altering the sound waves or fuel characteristics and then indirectly changing the flame. This method not only possesses the advantages of stable and reliable passive control but also fully leverages the rapid response and real-time online feedback advantages of active control. Finally, by combining the decoupling mechanism of thermoacoustic oscillations, an active control system based on actual physical processes is established, thereby achieving proactive prevention and control of thermoacoustic oscillations.

[0067] Combustion thermoacoustic oscillations have a time window for advance suppression, such as Figure 11 As shown, this time window lies between the absence of thermoacoustic oscillation and the complete formation of thermoacoustic oscillation, lasting approximately 100 milliseconds. The key is how to suppress combustion thermoacoustic oscillation within this advance suppression time window. In this invention, the pulse of the flame heat release rate is monitored using a photomultiplier tube array. This method is superior to monitoring sound pressure pulses because when the pressure amplitude pulse is less than 10%, the pulse of the flame heat release rate already exceeds 50%. By monitoring the pulse of the flame heat release rate, it is possible to determine more quickly and effectively whether combustion thermoacoustic oscillation has occurred, thus obtaining an advance time of approximately 50 milliseconds. This time window provides the prerequisite for advance suppression of combustion thermoacoustic oscillation. Under the action of the active controller 6 with extremely low delay time and the plasma spray gun 52 (actuator), the thermoacoustic oscillation in the combustion chamber 2 can be suppressed in its nascent stage before complete triggering.

[0068] The original periodic pulsating thermoacoustic oscillation signal will be changed, such as... Figure 12 As shown in (a), before using the method of actively suppressing combustion thermoacoustic oscillations by plasma jet, there is a periodic limit ring oscillation in the combustion chamber 2, and the flame pulsation amplitude is very high. After using the method of actively suppressing combustion thermoacoustic oscillations by plasma jet proposed in this invention, the combustion thermoacoustic oscillations in the limit ring state are suppressed, the oscillation signal changes significantly, the oscillation amplitude is significantly reduced, and the pulsation frequency also changes.

[0069] This invention enables safe, clean, and efficient combustion of combustible gases or liquids, and can be widely applied to the prevention and control of thermal and acoustic vibrations in combustion equipment such as gas turbines, industrial boilers, rockets, and internal combustion engines.

[0070] In this invention, unless otherwise stated, scientific and technical terms used herein have the meanings commonly understood by those skilled in the art.

[0071] It should be noted that the terms such as "upper", "lower", "left", "right", "front", and "back" used in the invention are only for clarity of description and are not intended to limit the scope of the invention. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of the invention.

[0072] Finally, it should be noted that the above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A plasma jet-guided active suppression device for combustion thermoacoustic oscillation, used to control the flame in a burner, the burner comprising a gas premixing section, a combustion chamber, and a flue gas exhaust channel connected in sequence, characterized in that: Includes a combustion thermoacoustic oscillation signal advance acquisition unit and a plasma jet suppression unit; The advanced acquisition unit for combustion thermoacoustic oscillation signals includes several photomultiplier tubes; The photomultiplier tube is installed on the side wall of the combustion chamber, above the flame, to monitor the pulsation of the flame heat release rate; The plasma jet suppression unit includes a plasma generator and several plasma spray guns; The plasma generator is connected to several plasma spray guns. The active particles generated by the plasma generator and the compressed gas form a plasma jet through the plasma spray guns. The plasma jet enters the combustion chamber and comes into contact with the oscillating flame front, suppressing the combustion thermoacoustic oscillations; The device also includes an active controller; the active controller receives data collected by the photomultiplier tube and controls the plasma jet to enter the combustion chamber based on the collected data; The photomultiplier tube is tilted and perpendicular to the normal direction of the flame front. The plasma jet suppression unit also includes several quartz glass tubes; the number of quartz glass tubes is equal to the number of plasma spray guns, and they correspond one-to-one; the quartz glass tubes are fixed to the side wall of the combustion chamber, with one end inside the combustion chamber and the other end outside the combustion chamber, connected to the corresponding plasma spray gun; the plasma jet generated by the plasma spray gun enters the combustion chamber through the quartz glass tubes. The suppression method includes the following steps: S1, the time-series signal of the flame heat release rate pulsation from the photomultiplier tube, enters the active controller; S2. The active controller performs fast Fourier analysis on the collected time series signal to obtain the amplitude and frequency of flame oscillation. S3. The active controller determines whether the flame oscillation has reached the threshold for thermoacoustic oscillation excitation. If the threshold is not reached, the active controller does not generate a voltage signal to suppress the action. If the threshold is reached, the active controller further analyzes the amplitude and frequency of the flame oscillation and generates an analog voltage signal accordingly to control the plasma generator to generate active particles, which, together with compressed gas, generate a plasma jet through the plasma spray gun. Then, S1-S3 are repeated.

2. The plasma jet advanced active suppression device for combustion thermoacoustic oscillation according to claim 1, characterized in that: in, The plasma jet suppression unit also includes a gas storage tank and a gas flow meter; The gas storage tank is connected to the plasma spray gun via pipeline to provide compressed air; The gas flow meter is installed on the pipeline between the gas storage tank and the plasma spray gun.

3. The plasma jet-assisted active suppression of combustion thermoacoustic oscillations device according to claim 2, characterized in that: in, The device also includes a phase synchronizer; The active controller is connected to the phase synchronizer, and the phase synchronizer is connected to the plasma generator and the gas flow meter respectively; The active controller uses a phase synchronizer to control the plasma generator and gas flow meter to form a plasma jet.

4. The plasma jet advanced active suppression device for combustion thermoacoustic oscillation according to claim 3, characterized in that: in, The plasma jet suppression unit also includes a probe and an oscilloscope; The probe measures the voltage and current signals of the plasma jet, which are monitored in real time by an oscilloscope and transmitted to the phase synchronizer.

5. The plasma jet advanced active suppression device for combustion thermoacoustic oscillation according to claim 1, characterized in that: in, The photomultiplier tubes are arranged symmetrically along the circumference on the side wall of the combustion chamber, forming a photomultiplier tube array.

6. The plasma jet advanced active suppression device for combustion thermoacoustic oscillation according to claim 1, characterized in that: in, The quartz glass tubes are divided into several groups, and the multiple quartz glass tubes in each group are arranged vertically with a height matching the height of the flame. The several groups of quartz glass tubes are arranged symmetrically along the circumference on the side wall of the combustion chamber.

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