A burner with rotating sliding arc discharge plasma to suppress combustion oscillation

Abstract

A burner for suppressing combustion oscillation by rotating sliding arc discharge plasma, the burner comprises a combustion chamber, an anode shell and a premixing insulation section connected in sequence, the combustible premixed gas is fed in from the front end of the premixing insulation section, a cathode truncated cone electrode is installed in the anode shell, an axial swirler is arranged in front of the cathode truncated cone electrode along the flow direction of the combustible premixed gas, the anode shell and the cathode truncated cone electrode are configured to generate an arc after power is turned on, the axial swirler is configured to generate a swirling airflow, the swirling airflow drives the arc to form a three-dimensional rotating sliding arc in the arc channel between the anode shell and the cathode truncated cone electrode, and forms a three-dimensional space discharge plasma area, which acts on the root and surroundings of the combustion oscillation flame. The present invention uses rotating sliding arc plasma as a dynamic and active way to act on the root and surroundings of the combustion chamber flame, and plays a role in regulating and suppressing the combustion oscillation state of the flame.

Description

Technical Field

[0001] The invention belongs to the field of energy and power technology, relates to a method for suppressing combustion oscillation by using plasma, and particularly relates to a burner for suppressing combustion by using rotating sliding arc discharge plasma. Background Art

[0002] With the implementation of increasingly stringent international environmental emission standards, modern advanced burners mostly use dry lean premixed combustion technology, where fuel and a large amount of air are mixed into the combustion zone for dilute phase combustion. This combustion method can effectively reduce the generation of pollutants such as NOx. But at the same time, the problem of combustion oscillation is more prominent. In the lean premixed combustion mode, the equivalence ratio tends to the flameout boundary, which is easily disturbed by the outside world and produces heat release rate pulsation. Once the fluctuation of the combustion heat release rate is coupled with the pressure fluctuation (thermoacoustic coupling), the positive feedback formed will convert the energy released by the combustion into the oscillation energy of the acoustic system, resulting in violent pressure and heat release rate pulsation, which is generally called combustion oscillation or thermoacoustic oscillation. In engineering applications, once thermoacoustic oscillation occurs, it will affect the stable working range of the combustion system at the least, and cause damage to the combustion device and other components at the worst, and seriously endanger the safe operation of the entire combustion system. Therefore, it is necessary to adopt an effective control method to avoid combustion oscillation in the combustion device.

[0003] Traditional control methods for thermoacoustic oscillations inside burners are mainly passive control and active control. Passive control refers to reducing the sensitivity of the combustion process to acoustic disturbances by redesigning the burner structure and air distribution method, or by adding silencer components to absorb acoustic energy and avoid the growth of sound waves. Passive control has a limited scope of application and only works on specific oscillation conditions of specific equipment. It can only be developed for a specific type of burner, resulting in long development cycles and high costs. Active control uses external monitors and active actuators to actively apply appropriate external excitations (to inlet air or fuel supply, etc.) based on signals such as pressure pulsation in the monitored combustion system to destroy the coupling process of heat release rate pulses and acoustic pressure pulsations. It has the characteristics of good control effect, wide application, and easy operation. However, this type of method requires additional control systems and actuators, and in terms of actuators, there are problems such as insufficient actuation frequency of mechanical valves (usually less than 100Hz), actuation time delay, and mechanical losses.

[0004] In view of the technical problems of insufficient actuation frequency, large actuation time delay and mechanical loss in the current methods for suppressing combustion pressure pulsation, existing patents such as CN201811639692.9, CN201811635818.5, CN201811635817.0, etc., all adopt the scheme of using central plasma or side plasma or both to coordinate as a dynamic and active way to regulate the pressure pulsation state of the combustion system during the combustion process, but all use the method of generating plasma by dielectric barrier discharge (DBD). Although this method can generate a large area of ​​low-temperature plasma, this method also has the problems of uneven discharge and its dielectric layer is very easy to rupture due to uneven heating, and the electrode is damaged. In addition, the working environment of the combustion chambers of aircraft engines, gas turbines, etc. is harsh, which makes its dielectric layer more easily damaged. Therefore, DBD discharge is not convenient for use in these combustion chambers. In addition, the above patents require the installation of electrodes that can generate plasma at the root and side of the flame at the same time to achieve a better effect of suppressing combustion pressure pulsation, and the structure is also more complicated. Summary of the invention

[0005] In order to overcome the shortcomings of the above-mentioned prior art, the purpose of the present invention is to provide a burner with a rotating sliding arc discharge plasma to suppress combustion oscillations. One purpose is to solve the problems of insufficient actuation frequency, delayed actuation time and mechanical loss in the active combustion control method in the prior art; another purpose is to solve the problems of uneven discharge, rupture of the dielectric layer due to uneven heating, damage to the electrode in the DBD discharge plasma suppression method of pressure pulsation, and the complex structure caused by the above-mentioned patent to achieve a better pressure pulsation suppression effect.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is:

[0007] A burner for suppressing combustion oscillation by rotating sliding arc discharge plasma comprises a combustion chamber, an anode shell and a premixing insulating section which are connected in sequence, combustible premixed gas is fed in from the front end of the premixing insulating section, a cathode truncated cone electrode is installed in the anode shell, an axial swirler is arranged in front of the cathode truncated cone electrode along the flow direction of the combustible premixed gas, the anode shell and the cathode truncated cone electrode are configured to generate an arc after power is turned on, the axial swirler is configured to generate a swirling airflow, the swirling airflow drives the arc to form a three-dimensional rotating sliding arc in the arc channel between the anode shell and the cathode truncated cone electrode, and forms a three-dimensional space discharge plasma area, which acts on the root and surroundings of the combustion oscillation flame.

[0008] In one embodiment, the rear end of the combustion chamber, i.e., the gas outlet end, is connected to the large diameter end of the conical exhaust port, and the front end, i.e., the gas inlet end, is connected to the rear end, i.e., the gas outlet end, of the anode shell; the front end, i.e., the gas inlet end, of the anode shell is connected to the rear end, i.e., the gas outlet end, of the premixed insulating section; the premixed insulating section is provided with a honeycomb rectifier plate.

[0009] In one embodiment, the inner diameter D of the anode shell is 60-80 mm, the inner diameter of the combustion chamber is 1.2-1.5 times the inner diameter of the anode shell, and the inner diameter of the premixed insulating section is the same as the inner diameter of the anode shell; the inner diameter of the large diameter end of the conical exhaust port is the same as the inner diameter of the combustion chamber, and the inner diameter of the small diameter end is 0.7-1.1 times the inner diameter of the anode shell.

[0010] In one embodiment, the front end of the premixed insulating section is connected to a base, and a hole for connecting to an air inlet is drilled at the front end of the base along the axial direction of the burner; the inner diameter of the base is the same as the inner diameter of the anode shell; a connecting rod passes through the base, the honeycomb rectifier plate and the axial cyclone in sequence, and is connected to the end face of the large diameter end of the cathode truncated cone electrode, and the connecting rod is configured as a grounding end.

[0011] In one embodiment, the air inlet end of the axial cyclone is flush with the air inlet end of the anode shell; the large diameter end of the cathode truncated cone electrode is close to one side of the air outlet end of the axial cyclone.

[0012] In one embodiment, the axial swirler is a blade-type axial swirler, comprising a hub, a plurality of swirl blades and a central through hole; the plurality of swirl blades are evenly distributed on the hub of the blade-type axial swirler along the circumference; the central through hole is used to install a connecting rod, and the inner diameter is the same as the diameter of the connecting rod; the number of the swirl blades is 4 to 12; the guide airflow outlet angle of the swirl blades is 15° to 85°; the outer diameter of the blade-type axial swirler is the same as the inner diameter of the anode shell.

[0013] In one embodiment, the diameter D2 of the large diameter end of the cathode truncated cone electrode is 40 mm to 60 mm; the angle between the side surface of the cathode truncated cone electrode and the central axis of the burner is θ The angle d between the cathode truncated cone electrode and the anode shell is 30°~80°; the distance between the large diameter end of the cathode truncated cone electrode and the inner surface of the anode shell is 5~15 mm; the end face of the small diameter end of the cathode truncated cone electrode is lower than the end face of the gas outlet end of the anode shell, and the distance d between the end face of the small diameter end of the cathode truncated cone electrode and the end face of the gas outlet end of the anode shell is 15 mm~30 mm, and the end face of the small diameter end of the cathode truncated cone electrode is used to fix the flame.

[0014] The present invention also provides a method for suppressing combustion oscillation of a burner based on the rotating sliding arc discharge plasma to suppress combustion oscillation, wherein the anode shell is connected to a power supply and the cathode truncated cone electrode is grounded; a combustible premixed gas is injected into the combustion chamber and ignited; when the combustion chamber generates a combustion oscillation phenomenon accompanied by a pressure fluctuation of a certain amplitude, the power supply is started, and an arc is generated between the anode shell and the cathode truncated cone electrode under the excitation of a high-voltage electric field, and the arc slides downstream driven by the swirling airflow generated by the axial swirler and is continuously elongated, and when the arc moves to the farthest end, it is blown off by the airflow, and then it is broken down again at the minimum distance between the anode shell and the cathode truncated cone electrode, and is driven by the airflow to rotate and slide again, and this cycle is repeated over and over again, and finally a three-dimensional space discharge plasma region is formed, and the region acts on the root and surroundings of the flame where the combustion oscillation occurs; the discharge frequency of the plasma is adjusted to be an integer multiple of the main frequency when the flame undergoes combustion oscillation, and the discharge intensity of the plasma is adjusted at the same time, so as to suppress the combustion oscillation in the combustion chamber.

[0015] In one embodiment, the power supply is a nanosecond pulse power supply with a voltage of 0~20kV and a pulse repetition frequency of 20kHz; or the power supply is a high-frequency AC power supply with an output voltage of 0~40kV and a frequency range of 1~150kHz; or the power supply is a DC-AC coupled power supply, that is, a power supply obtained by superimposing a high-frequency and high-voltage AC component on a high-voltage DC, wherein the DC power supply power is 20kW, the maximum current is 0.5A, the AC power supply frequency is 1~150kHz, and the voltage is 0~40kV.

[0016] In one embodiment, the main frequency of the combustion chamber combustion oscillation is in the range of 100 Hz to 500 Hz, and the discharge frequency of the plasma is adjusted to be an integer multiple of the main frequency when the flame combustion oscillates, that is, 500 Hz to 100 kHz.

[0017] The beneficial effects of the present invention are:

[0018] Compared with traditional active control such as mechanical valves, the present invention uses rotating sliding arc discharge plasma as a new type of active control method with obvious advantages: lower energy consumption, fast start-up, no moving parts or other complex structures, easy adjustment of excitation parameters, high excitation efficiency of active particles, and its own high-frequency actuation characteristics of thousands of hertz and small delay, thus solving the problems of insufficient actuation frequency, delayed actuation time and mechanical loss in traditional active control. In addition, the rotating sliding arc can generate large-volume low-temperature plasma, stable and uniform discharge, small electrode ablation, and long electrode life, thus solving the problems of uneven DBD discharge, uneven heating of the dielectric layer and cracking, electrode damage, and inability to adapt to the harsh working environment of gas turbines and aircraft engine combustion chambers. At the same time, the present invention uses rotating sliding arc discharge plasma to act on the root and surroundings of the flame at the same time, and does not need to install electrodes that can generate plasma at the root and sides of the flame at the same time, making its structure simple. From the phenomenon point of view, when the rotating sliding arc discharge plasma is started, it can be seen that the flame is stably attached to the vicinity of the electrode, the flame shape is stable, and it is less affected by airflow disturbance. In addition, by connecting different power supplies and adjusting the parameters, a series of results with different degrees of suppression of combustion chamber combustion oscillation can be obtained, and finally the best effect of suppressing combustion chamber combustion oscillation can be obtained. For the combustion oscillation of a dynamic combustion chamber, there are good feedback adjustment implementation conditions, and by adjusting various relevant parameters, the best effect of suppressing combustion chamber combustion oscillation can be achieved.

[0019] In the present invention, for a flame with combustion oscillation in a combustion chamber, the sliding arc discharge plasma acts on the root and the periphery of the flame at the same time, which can significantly change the heat release rate law of the flame, thereby breaking the formation conditions of the heat release rate and pressure of the flame in the combustion chamber to meet the combustion oscillation, achieving the reduction of heat release pulsation and pressure pulsation, and suppressing the combustion oscillation. Experiments have found that the amplitude of the pressure oscillation in the combustion chamber with the action of rotating sliding arc discharge plasma can be reduced to about 3% of that in the combustion chamber without the action of rotating sliding arc discharge plasma, and the effect is very significant. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 The present invention is a schematic diagram of the structure of a burner that uses rotating sliding arc discharge plasma to suppress combustion oscillation.

[0021] Figure 2 Schematic diagram of three-dimensional rotating sliding arc discharge.

[0022] Figure 3 Schematic diagram of the three-dimensional structure of the conical exhaust port.

[0023] Figure 4 Schematic diagram of the three-dimensional structure of the anode shell.

[0024] Figure 5(a) and (b) are schematic diagrams of the three-dimensional structure of the cathode truncated cone electrode.

[0025] Figure 6 Schematic diagram of the three-dimensional structure of the axial cyclone.

[0026] Figure 7 Schematic diagram of the three-dimensional structure of the connecting rod.

[0027] Figure 8 Schematic diagram of the three-dimensional structure of the premixed insulation section.

[0028] Fig. 9 Schematic diagram of the three-dimensional structure of the honeycomb rectifier plate.

[0029] Fig.10 (a) and (b) are schematic diagrams of the three-dimensional structure of the base.

[0030] Fig.11 Schematic diagram of the three-dimensional structure of a single air inlet.

[0031] Fig.12 The combustion oscillation data of the combustion chamber without rotating sliding arc discharge plasma and the combustion chamber with rotating sliding arc discharge plasma whose power source is nanosecond pulse power source.

[0032] Fig.13 The combustion oscillation data are for a combustion chamber without rotating sliding arc discharge plasma and a combustion chamber with rotating sliding arc discharge plasma whose power source is a high-frequency AC power source.

[0033] Fig.14 The combustion oscillation data of the combustion chamber without rotating sliding arc discharge plasma and the combustion chamber with rotating sliding arc discharge plasma whose power supply is DC-AC coupled power supply.

[0034] Figure 1 and Figure 2 In the figure, 1 is a conical exhaust port, 2 is a combustion chamber, 3 is an anode shell, 4 is a cathode truncated cone electrode, 5 is an axial cyclone, 6 is a connecting rod, 7 is a premixed insulating section, 8 is a honeycomb rectifier plate, 9 is a base, 10 is an air inlet, 11 is a power source, 12 is a flame, 13 is a combustible premixed gas, and 14 is a three-dimensional rotating sliding arc. DETAILED DESCRIPTION

[0035] The embodiments of the present invention are described in detail below with reference to the accompanying drawings and examples.

[0036] The embodiment of the present invention provides a burner for suppressing combustion oscillation by rotating sliding arc discharge plasma, such as Figures 1 to 11As shown, it mainly includes a combustion chamber 2, an anode shell 3, a cathode truncated cone electrode 4, an axial cyclone 5, and a premixed insulating section 7. Among them, the combustion chamber 2, the anode shell 3 and the premixed insulating section 7 are connected in sequence. For the convenience of description, the present invention defines the sequence according to the flow direction of the combustible premixed gas 13. The combustible premixed gas 13 is fed in from the front end of the premixed insulating section 7. The cathode truncated cone electrode 4 is installed in the anode shell 3, with a certain gap between the two, and the large diameter end of the cathode truncated cone electrode 4 is located upstream, and the small diameter end is located downstream. The axial cyclone 5 is arranged in front of the cathode truncated cone electrode 4. Through this structure, when the anode shell 3 and the cathode truncated cone electrode 4 are connected to the power supply 11, an arc will be generated between the two under the excitation of the high-voltage electric field. The combustible premixed gas 13 is output as a swirling airflow under the action of the axial swirler 5. The swirling airflow drives the arc to form a three-dimensional rotating sliding arc 14 in the arc channel between the anode shell 3 and the cathode truncated cone electrode 4, and forms a three-dimensional space discharge plasma area, which acts on the root and surroundings of the combustion oscillation flame.

[0037] In one embodiment of the present invention, the burner further comprises a conical exhaust port 1, the large diameter end of the conical exhaust port 1 being the front end connected to the rear end (i.e., the gas outlet end) of the combustion chamber 2, the front end (i.e., the gas inlet end) of the combustion chamber 2 being connected to the rear end (i.e., the gas outlet end) of the anode shell 3, and the front end (i.e., the gas inlet end) of the anode shell 3 being connected to the rear end (i.e., the gas outlet end) of the premixed insulating section 7.

[0038] This embodiment provides a connection method for the burner and the structure of the conical exhaust port 1. Through the conical exhaust port 1, the exhaust gas after the burner combustion can be accelerated in the convergent channel and then discharged into the atmosphere, thereby playing the role of exhausting waste gas.

[0039] In one embodiment of the present invention, the burner further comprises a base 9, the front end (i.e., the air inlet end) of the premixed insulating section 7 is connected to the rear end (i.e., the air outlet end) of the base 9, and the front end (i.e., the air inlet end) of the base 9 is drilled with a hole connected to an air inlet 10 along the axial direction of the burner, and the air inlet 10 is located at one end of the outer surface of the base 9 and is sealed and connected to the gas supply system. For example, at least two air inlets 10 are provided here, respectively for inputting two or more gases. It is easy to understand that the air inlets 10 are preferably arranged symmetrically with respect to the center.

[0040] In one embodiment of the present invention, a honeycomb rectifier plate 8 is provided in the premixed insulating section 7, and the air inlet end of the honeycomb rectifier plate 8 is flush with the air inlet end of the premixed insulating section 7. After the combustible premixed gas 13 passes through the honeycomb rectifier plate 8, premixing is completed in the premixed insulating section 7.

[0041] In one embodiment of the present invention, in order to form an electrical path, the anode housing 3 is directly connected to an external power source 11, and the cathode truncated cone electrode 4 needs to be grounded. In this embodiment, a connecting rod 6 is provided, and the connecting rod 6 passes through the base 9 (if any), the honeycomb rectifier plate 8 (if any) and the axial cyclone 5 in sequence, and is connected to the end face of the large diameter end of the cathode truncated cone electrode 4. When in use, the connecting rod 6 is configured as a grounding end to achieve grounding of the cathode truncated cone electrode 4. It is easy to understand that in a specific project, the connecting rod 6 can also be replaced by a similar component such as a cable.

[0042] In this embodiment, a specific structural form is also given, that is, one end of the connecting rod 6 passes through the central through hole of the axial cyclone 5 and is inserted into the central straight hole of the cathode truncated cone electrode 4 near the outlet end of the axial cyclone 5, and the other end passes through the central through hole of the honeycomb rectifier plate 8 and extends out of the outer surface of the base 9 through the central through hole of the base 9. At this time, the conical exhaust port 1, the combustion chamber 2, the anode shell 3, the cathode truncated cone electrode 4, the connecting rod 6, the axial cyclone 5, the premixed insulating section 7, the honeycomb rectifier plate 8, and the base 9 are coaxial.

[0043] In one embodiment of the present invention, the air inlet end of the axial cyclone 5 is flush with the air inlet end of the anode shell 3 ; obviously, in the present invention, the large diameter end of the cathode truncated cone electrode 4 is close to one side of the air outlet end of the axial cyclone 5 .

[0044] In one embodiment of the present invention, the anode housing 3 is a hollow rotating body made of stainless steel. The gas outlet end of the anode housing 3 is connected to the gas inlet end of the combustion chamber 2 through a flange, and the gas inlet end is connected to the gas outlet end of the premixed insulation section 7 through a flange. The inner diameter D of the anode housing 3 is 60-80 mm. In this embodiment, the inner diameter D of the anode housing 3 is 70 mm.

[0045] In one embodiment of the present invention, the axial cyclone 5 is a blade-type axial cyclone, which is made of polytetrafluoroethylene with good insulation, and includes a hub, a plurality of swirl blades and a central through hole. The plurality of swirl blades are evenly distributed on the hub of the blade-type axial cyclone along the circumference; the central through hole is used to install the connecting rod, and the inner diameter is the same as the diameter of the connecting rod; the number of swirl blades is 4 to 12; the guide airflow outlet angle of the swirl blade is 15° to 85°; the outer diameter of the blade-type axial cyclone is the same as the inner diameter of the anode shell 3. In this embodiment, the blade-type axial cyclone 5 has 6 swirl blades, and the guide airflow outlet angle of each blade is 60°, and the outer diameter of the blade-type axial cyclone 5 is 70 mm.

[0046] In one embodiment of the present invention, the combustion chamber 2 is a hollow rotating body made of stainless steel, and its inner diameter is 1.2 to 1.5 times the inner diameter D of the anode shell 3. In this embodiment, the inner diameter of the combustion chamber 2 is 95 mm.

[0047] In one embodiment of the present invention, the conical exhaust port 1 is a hollow rotating body made of stainless steel, and its large diameter end is connected to the combustion chamber 2 through a flange. The combustion exhaust gas enters from the large diameter end of the conical exhaust port 1 and is discharged through the small diameter end of the conical exhaust port 1. The inner diameter of the large diameter end of the conical exhaust port 1 is the same as the inner diameter of the combustion chamber 2. The inner diameter of the small diameter end of the conical exhaust port 1 is 0.7 to 1.1 times the inner diameter D of the anode shell 3. In this embodiment, the inner diameter of the large diameter end of the conical exhaust port 1 is 95 mm, and the inner diameter of the small diameter end of the conical exhaust port 1 is 55 mm.

[0048] In one embodiment of the present invention, the premixed insulating section 7 is a central rotating body made of polytetrafluoroethylene, and its inner diameter is the same as the inner diameter of the anode shell 3. The air inlet end of the premixed insulating section 7 is connected to the air outlet end of the base 9 through a flange. In this embodiment, the inner diameter of the premixed insulating section 7 is 70 mm.

[0049] In one embodiment of the present invention, the honeycomb rectifier plate 8 is made of polytetrafluoroethylene and includes honeycomb circular holes and a central through hole evenly distributed along the circumference. The diameter D1 of the honeycomb circular hole is 4 mm to 6 mm. The central through hole is used to install the connecting rod 6, and the inner diameter is the same as the diameter of the connecting rod 6. The outer diameter of the honeycomb rectifier plate 8 is the same as the inner diameter of the premixed insulation section 7. In this embodiment, the outer diameter of the honeycomb rectifier plate 8 is 70 mm, and the diameter D1 of the honeycomb circular hole is 5 mm.

[0050] In one embodiment of the present invention, the base 9 is made of polytetrafluoroethylene. The center of the base 9 has a through hole that matches the connecting rod 6; the end of the base 9 away from the premixing insulation section 7 is bored with a hole connecting two air inlets 10 along the axial direction of the burner; the inner diameter of the base 9 is the same as the inner diameter of the anode shell 3. In this embodiment, the inner diameter of the base 9 is 70 mm.

[0051] In one embodiment of the present invention, the cathode truncated cone electrode 4 is a truncated cone electrode made of stainless steel, and the diameter D2 of the large diameter end close to the gas outlet end of the axial cyclone 5 is 40 mm to 60 mm. The angle between the side of the cathode truncated cone electrode 4 and the central axis of the burner is θis 30°~80°. When the cathode truncated cone electrode 4 is installed in the anode shell 3, the distance between the maximum diameter D2 of the cathode truncated cone electrode 4 and the inner surface of the anode shell 3 is 5~15 mm. There is a straight hole for installing the connecting rod 6 in the center of the plane on one side of the large diameter end of the cathode truncated cone electrode 4. The end face of the small diameter end of the cathode truncated cone electrode 4 is lower than the end face of the gas outlet end of the anode shell 3, and the distance d between the end face of the small diameter end of the cathode truncated cone electrode 4 and the end face of the gas outlet end of the anode shell 3 is 15 mm~30 mm. The end face of the small diameter end of the cathode truncated cone electrode 4 can be used to fix the flame 12. In this embodiment, the diameter D2 of the large diameter end of the cathode truncated cone electrode 4 close to the gas outlet end of the axial cyclone 5 is 60 mm, and the distance between the maximum diameter D2 of the cathode truncated cone electrode 4 and the inner surface of the anode shell 3 is 5 mm. The angle between the side of the cathode truncated cone electrode 4 and the center axis of the burner θ The plane of one side of the small diameter end of the cathode truncated cone electrode 4 is lower than the end face of the anode shell 3 on the gas outlet side, and the distance d between the two end faces is 20 mm.

[0052] In one embodiment of the present invention, the connecting rod 6 is made of stainless steel, with a diameter D3 of 10-15 mm and a length of 300-400 mm. In this embodiment, the connecting rod 6 has a diameter of 15 mm and a length of 360 mm.

[0053] In the present invention, the plasma generated by the rotating sliding arc discharge belongs to a low-temperature non-equilibrium plasma, so less heat is generated during the discharge process, and the premixed combustible gas 13 also helps to dissipate heat when passing through the air inlet 10, the base 9, the premixed insulating section 7, the honeycomb rectifier 8, the connecting rod 6, the axial cyclone 5, the cathode truncated cone electrode 4, and the anode shell 3, thereby reducing the ablation and oxidation of the metal surface. Therefore, the anode shell 3, the cathode truncated cone electrode 4, and the connecting rod 6 are all made of stainless steel. The axial cyclone 5, the premixed insulating section 7, the honeycomb rectifier 8, the base 9, and the air inlet 10 are all made of polytetrafluoroethylene, which is conducive to reducing the processing difficulty, cost, and weight of the burner.

[0054] Based on the burner, the embodiment of the present invention also provides a corresponding method for suppressing combustion oscillation by rotating sliding arc discharge plasma, which is specifically carried out according to the following steps:

[0055] The anode shell 3 is connected to the output end of the power supply 11 outside the burner, and the connecting rod 6 connected to the cathode truncated cone electrode 4 is connected to the ground wire as the ground end. Inject the combustible premixed gas 13 into the combustion chamber 2 and ignite it. When the combustion chamber 2 produces a combustion oscillation phenomenon accompanied by a pressure fluctuation of a certain amplitude, start the power supply 11 outside the burner. Under the excitation of the high-voltage electric field, an arc is generated between the anode shell and the cathode truncated cone electrode, and the gap between the two serves as an arc channel. Driven by the swirling airflow generated by the axial swirler 5, the arc slides downstream and continues to lengthen. When the arc moves to the farthest end, it is blown off by the airflow, and then breaks down again at the minimum distance between the anode shell 3 and the cathode truncated cone electrode 4, and is driven by the airflow to rotate and slide again. This cycle is repeated over and over again, and finally a three-dimensional space discharge plasma region is formed, which acts on the root and surroundings of the combustion oscillation flame 12. That is, the plasma generated by the rotating sliding arc discharge acts on the root and surroundings of the flame at the same time, and the plasma discharge frequency should be an integer multiple of the main frequency of the flame pulsation, so that the suspended flame is adsorbed near the sliding arc electrode, and the flame in the combustion chamber is affected by the temperature rise effect, chemical effect and aerodynamic effect of the plasma, and the influence of airflow disturbance is reduced, and the heat release stability is also improved. The local heat release generated by the sliding arc discharge forms a local high-temperature area, which affects the phase and frequency of the flame heat release rate, and then the flame's response to the airflow disturbance in the combustion chamber changes; the plasma acting on the flame will change the relative distance and position between the main heat release area of ​​the flame and the combustion chamber outlet, resulting in a change in the path length of the pressure fluctuation reflected from the combustion chamber outlet, so that the phase difference between the combustion heat release rate and the pressure pulsation cannot meet the Rayleigh criterion, destroying the positive feedback loop formed between the fluctuating heat release rate and the combustion chamber sound field, thereby reducing or even eliminating the amplitude of the pressure pulsation in the combustion chamber, and achieving the effect of suppressing combustion oscillation.

[0056] Considering that the main frequency of combustion oscillation in the combustion chamber 2 is in the range of 100Hz~500Hz, the discharge frequency of the plasma is adjusted to an integer multiple of the main frequency when the flame 12 undergoes combustion oscillation, that is, 500Hz~100kHz, and the discharge intensity of the plasma is changed by adjusting the voltage to achieve the suppression of combustion oscillation in the burner.

[0057] The power supply 11 can be a nanosecond pulse power supply, a high-frequency AC power supply or a DC-AC coupled power supply; the voltage of the nanosecond pulse power supply is 0~20kV, and the pulse repetition frequency can reach 20kHz; the high-frequency AC power supply has an output voltage of 0~40kV and a frequency range of 1~150kHz; the DC-AC coupled power supply is a power supply obtained by superimposing a high-frequency and high-voltage AC component on a high-voltage DC. The DC power supply has a power of 20kW and a maximum current of 0.5A; the AC power supply has a frequency of 1~150kHz and a voltage of 0~40kV.

[0058] The present invention is verified by the following tests:

[0059] Test 1: This test is a method of suppressing combustion oscillations by rotating sliding arc discharge plasma, such as Figure 1 and Figure 2 As shown, the specific steps are as follows:

[0060] The anode shell 3 is connected to the output end of the power supply 11 outside the burner. The power supply 11 is a nanosecond pulse power supply. The connecting rod 6 connected to the cathode truncated cone electrode 4 is connected to the ground wire as the ground end. The combustible premixed gas 13 of propane-air is injected into the combustion chamber 2 and ignited. When the combustion chamber 2 produces a combustion oscillation phenomenon accompanied by a pressure fluctuation of a certain amplitude, the power supply 11 outside the burner is started, and a three-dimensional rotating sliding arc 14 is generated under the excitation of a high-voltage electric field at the minimum spacing between the anode shell 3 and the cathode truncated cone electrode 4, forming a three-dimensional space discharge plasma area, which acts on the root and surroundings of the flame 12 where the combustion oscillation occurs. The discharge frequency of the plasma is adjusted to an integer multiple of the main frequency (500Hz~100kHz) when the flame 12 undergoes combustion oscillation, and the discharge intensity of the plasma is changed by adjusting the voltage to achieve the suppression of combustion oscillation in the burner.

[0061] In this test, after the burner induces combustion oscillations of a certain intensity, the power supply 11 is turned on to break down the air at the shortest point of the gap between the rotating sliding arc anode shell 3 and the cathode truncated cone electrode 4, and a three-dimensional rotating sliding arc 14 is generated under the blowing of the swirling gas. The three-dimensional rotating sliding arc 14 continuously lengthens and extends during the downstream rotating sliding process. When the length of the three-dimensional rotating sliding arc 14 reaches a critical length, the three-dimensional rotating sliding arc 14 is extinguished and breaks down again from the shortest point of the gap, and the three-dimensional rotating sliding arc 14 moves into the next cycle. During this process, the large-area, highly active non-equilibrium plasma generated by the discharge of the three-dimensional rotating sliding arc 14 will act on the root and surroundings of the flame 12, and the frequency of the plasma will be adjusted to a multiple of the main frequency of the flame 12 when it undergoes combustion oscillation. At this time, the thermal effect, activation effect (dynamics) and transport effect (aerodynamics) of the plasma act on the flame 12 to reduce the influence of the premixed airflow disturbance on it, and improve the heat release stability; and the flame heat release law is adjusted, so that the amplification degree of the pulsating energy in the burner is reduced, that is, the process in which the velocity pulsation affects the pulsation of the flame heat release rate is blocked, thereby achieving the suppression of combustion oscillations in the combustion chamber 2. Fig.12As shown, when the pressure pulsation frequency is consistent, when there is no sliding arc discharge plasma, the pressure pulsation amplitude of the flame in the combustion chamber is 411Pa, and under the action of plasma, the pressure pulsation amplitude of the flame is 14.5Pa. It can be seen that the use of a nanosecond pulse power supply in this embodiment and the use of a rotating sliding arc discharge plasma to act on the flame 12 can significantly suppress combustion oscillations. At the same time, practice has found that the method for suppressing combustion oscillations by a rotating sliding arc discharge plasma proposed in the present invention has significant effects on single swirl flames, stratified swirl flames, combustible premixed gases and combustible premixed liquids, etc., and has good versatility. In addition, a burner and a suppression method for suppressing combustion oscillations by a rotating sliding arc discharge plasma designed by the present invention are suitable for common working ranges, such as the range of equivalence ratio 0.50~0.90, and can significantly suppress combustion oscillations.

[0062] Experiment 2: This experiment is a method of suppressing combustion oscillation by rotating sliding arc discharge plasma, such as Figure 1 and Figure 2 As shown, the specific steps are as follows:

[0063] The anode shell 3 is connected to the output end of the power supply 11 outside the burner. The power supply 11 is a high-frequency AC power supply. The connecting rod 6 connected to the cathode truncated cone electrode 4 is connected to the ground wire as the ground end. The combustible premixed gas 13 of propane-air is injected into the combustion chamber 2 and ignited. When the combustion chamber 2 produces combustion oscillations accompanied by pressure fluctuations of a certain amplitude, the power supply 11 outside the burner is started, and a three-dimensional rotating sliding arc 14 is generated under the excitation of a high-voltage electric field at the minimum spacing between the anode shell 3 and the cathode truncated cone electrode 4, forming a three-dimensional space discharge plasma region, which acts on the root and surroundings of the flame 12 where the combustion oscillation occurs. The discharge frequency of the plasma is adjusted to an integer multiple of the main frequency (500Hz~100kHz) when the flame 12 undergoes combustion oscillations, and the discharge intensity of the plasma is changed by adjusting the voltage to achieve the suppression of combustion oscillations in the burner. Fig.13 As shown, when the pressure pulsation frequency is consistent and there is no sliding arc discharge plasma action, the pressure pulsation amplitude of the flame 12 in the combustion chamber is 411Pa, while under the action of plasma, the pressure pulsation amplitude of the flame is 17.1Pa.

[0064] Experiment 3: This experiment is a method of suppressing combustion oscillations by rotating sliding arc discharge plasma, such as Figure 1 and Figure 2 As shown, the specific steps are as follows:

[0065] The anode shell 3 is connected to the output end of the power supply 11 outside the burner. The power supply 11 is a DC-AC coupled power supply. The connecting rod 6 connected to the cathode truncated cone electrode 4 is connected to the ground wire as the ground end. The combustible premixed gas 13 of propane-air is injected into the combustion chamber 2 and ignited. When the combustion chamber 2 produces combustion oscillations accompanied by pressure fluctuations of a certain amplitude, the power supply 11 outside the burner is started, and a three-dimensional rotating sliding arc 14 is generated under the excitation of a high-voltage electric field at the minimum spacing between the anode shell 3 and the cathode truncated cone electrode 4, forming a three-dimensional space discharge plasma region, which acts on the root and surroundings of the flame 12 where the combustion oscillation occurs. The discharge frequency of the plasma is adjusted to an integer multiple of the main frequency (500Hz~100kHz) when the flame 12 undergoes combustion oscillations, and the discharge intensity of the plasma is changed by adjusting the voltage to achieve the suppression of combustion oscillations in the burner. As Fig.14 As shown, when the pressure pulsation frequency is consistent, when there is no sliding arc discharge plasma action, the pressure pulsation amplitude of the flame 12 in the combustion chamber 2 is 411Pa, while under the action of plasma, the pressure pulsation amplitude of the flame is 18.2Pa.

[0066] In summary, the present invention uses rotating sliding arc plasma as a dynamic and active way to act on the root and surrounding of the flame in the combustion chamber, and plays a role in regulating and suppressing the combustion oscillation state of the flame. The flame is affected by the plasma and the influence of the premixed airflow disturbance is weakened, and the heat release stability is improved; and the flame heat release law is adjusted to decouple it from the acoustic system of the combustion system, thereby achieving the suppression of combustion oscillations in the combustion chamber. In addition, this method has a significant effect on single swirl flames, stratified swirl flames, combustible premixed gases and combustible premixed liquids, etc., and has good versatility.

Claims

1. A burner for suppressing combustion oscillation by rotating sliding arc discharge plasma, characterized in that: The invention comprises a combustion chamber (2), an anode shell (3) and a premixing insulating section (7) connected in sequence, wherein a combustible premixed gas (13) is fed into the anode shell (3) from the front end of the premixing insulating section (7), a cathode truncated cone electrode (4) is installed in the anode shell (3), and an axial swirler (5) is arranged in front of the cathode truncated cone electrode (4) along the flow direction of the combustible premixed gas (13), wherein the large diameter end of the cathode truncated cone electrode (4) is close to the side of the gas outlet end of the axial swirler (5); the anode shell (3) and the cathode truncated cone electrode (4) are configured to generate an arc after a power source (11) is turned on, and the axial swirler (5) is configured to generate a swirling airflow, and the swirling airflow drives the arc to form a three-dimensional rotating sliding arc (14) in the arc channel between the anode shell (3) and the cathode truncated cone electrode (4), and forms a three-dimensional space discharge plasma region, which acts on the root and surroundings of the combustion oscillation flame; The rear end, i.e., the gas outlet end, of the combustion chamber (2) is connected to the large diameter end of the conical exhaust port (1), and the front end, i.e., the gas inlet end, is connected to the rear end, i.e., the gas outlet end, of the anode shell (3); the front end, i.e., the gas inlet end, of the anode shell (3) is connected to the rear end, i.e., the gas outlet end, of the premixed insulating section (7); the premixed insulating section (7) is provided with a honeycomb rectifier plate (8); The diameter D2 of the large diameter end of the cathode truncated cone electrode (4) is 40 mm to 60 mm; the angle between the side surface of the cathode truncated cone electrode (4) and the central axis of the burner is θ The angle of the cathode truncated cone electrode (4) is 30° to 80°; the distance between the large diameter end of the cathode truncated cone electrode (4) and the inner surface of the anode shell (3) is 5 mm to 15 mm; the end surface of the small diameter end of the cathode truncated cone electrode (4) is lower than the end surface of the gas outlet end of the anode shell (3); the distance d between the end surface of the small diameter end of the cathode truncated cone electrode (4) and the end surface of the gas outlet end of the anode shell (3) is 15 mm to 30 mm; the end surface of the small diameter end of the cathode truncated cone electrode (4) is used to fix the flame.

2. The burner for suppressing combustion oscillation by rotating sliding arc discharge plasma according to claim 1, characterized in that: The inner diameter D of the anode shell (3) is 60 mm to 80 mm, the inner diameter of the combustion chamber (2) is 1.2 to 1.5 times the inner diameter of the anode shell (3), the inner diameter of the premixed insulating section (7) is the same as the inner diameter of the anode shell (3); the inner diameter of the large diameter end of the conical exhaust port (1) is the same as the inner diameter of the combustion chamber (2), and the inner diameter of the small diameter end is 0.7 to 1.1 times the inner diameter of the anode shell (3).

3. The burner for suppressing combustion oscillation by rotating sliding arc discharge plasma according to claim 1 or 2, characterized in that: The front end of the premixed insulating section (7) is connected to a base (9), and a hole connected to an air inlet (10) is bored at the front end of the base (9) along the axial direction of the burner; the inner diameter of the base (9) is the same as the inner diameter of the anode shell (3); the connecting rod (6) passes through the base (9), the honeycomb rectifier plate (8) and the axial cyclone (5) in sequence, and is connected to the end face of the large diameter end of the cathode truncated cone electrode (4), and the connecting rod (6) is configured as a grounding end.

4. The burner for suppressing combustion oscillation by rotating sliding arc discharge plasma according to claim 1, characterized in that: The air inlet end of the axial cyclone (5) is flush with the air inlet end of the anode shell (3).

5. The burner for suppressing combustion oscillation by rotating sliding arc discharge plasma according to claim 1, characterized in that: The axial swirler (5) is a blade-type axial swirler, comprising a hub, a plurality of swirl blades and a central through hole; the plurality of swirl blades are evenly distributed on the hub of the blade-type axial swirler along the circumference; the central through hole is used to install a connecting rod, and the inner diameter is the same as the diameter of the connecting rod; the number of the swirl blades is 4 to 12; the guide airflow outlet angle of the swirl blades is 15° to 85°; the outer diameter of the blade-type axial swirler is the same as the inner diameter of the anode shell (3).

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