Device and method for preventing flashback of surface dielectric barrier discharge based on flow control

Abstract

A device and method for preventing flashback of dielectric barrier discharge along the surface based on flow control, the device comprises a premixing tube, a central blunt body and a plasma actuator; the plasma actuator is a first plasma actuator and / or a second plasma actuator; a pair of electrodes are arranged inside and outside the premixing tube and / or inside and outside the central blunt body respectively, and after the power is turned on, plasma is generated inside the premixing tube and / or outside the central blunt body; the flow field of the inner wall surface of the premixing tube and / or the outer wall surface of the central blunt body is changed by the flow control effect of the plasma, and the flashback of the boundary layer along the premixing tube and / or the central blunt body is suppressed. The present invention utilizes plasma excitation flow control, changes the boundary layer flow field, introduces ion wind to increase the flow velocity of the boundary layer, thereby suppressing flashback and increasing the stable combustion range.

Description

Technical Field

[0001] The present invention belongs to the field of energy and power technology, relates to combustion technology of gas turbines and other equipment, and particularly to a surface dielectric barrier discharge flashback prevention device and method based on flow control. Background Art

[0002] Gas turbines have high fuel adaptability, and it is technically feasible to expand their fuel application range to hydrogen-rich and even pure hydrogen fuels. The scalability of gas turbines from small distributed devices to large centralized devices will play a greater role in future energy networks.

[0003] Advanced low-pollution combustion technology usually adopts lean premixed combustion technology, organizes combustion under a lean equivalence ratio, and reduces NOx emissions by reducing the residence time. However, lean premixed combustion is prone to combustion instability problems, such as blowout, flashback, and thermoacoustic oscillation. For hydrogen-rich or pure hydrogen fuels, due to the high chemical reactivity and high laminar combustion velocity (290cm / s) of hydrogen, the risk of flashback in the gas turbine combustion chamber will increase. The flame will propagate from the combustion chamber to the upstream of the premixing tube, causing overheating and serious damage to the upstream components of the combustion chamber, thereby affecting the operation of the entire combustion system. Flashback is considered to be one of the important obstacles to the development of hydrogen-rich or pure hydrogen combustion technology. Therefore, it is necessary to prevent flashback of gas turbines due to the use of hydrogen-rich or pure hydrogen fuels, avoid damage to expensive components, and expand the reliable operation range of gas turbines.

[0004] Traditional control methods for combustion chamber flashback instability are mainly passive control, which usually involves optimizing the burner structure, designing and optimizing the nozzle, or using fuse-type flashback prevention nozzles to reduce the risk of flashback. Passive control methods cannot prevent flashback when it occurs. 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 surface dielectric barrier discharge flashback prevention device and method based on flow control, which utilizes plasma-excited flow control to suppress the flashback of the hydrogen-rich flame or the pure hydrogen flame in the combustion chamber, so as to avoid damage to expensive components upstream of the combustion chamber and expand the reliable operation range of the gas turbine.

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

[0007] A surface dielectric barrier discharge flashback prevention device based on flow control, comprising a premixing tube, a central blunt body and a plasma actuator;

[0008] The central bluff body is axially disposed in the premixing tube, and a premixing gas channel is formed between the two, and the end of the premixing gas channel is connected to the intake end of the combustion chamber;

[0009] The plasma actuator is a first plasma actuator and / or a second plasma actuator;

[0010] The first plasma exciter comprises a premixing tube, a first electrode, a second electrode and a first power source; the first electrode is arranged on the outer wall of the premixing tube and can be encapsulated, and the second electrode is arranged on the inner wall of the premixing tube; the first electrode is connected to the first power source, and the second electrode is grounded;

[0011] The second plasma exciter includes a central bluff body, a third electrode, a fourth electrode and a second power supply; a chamber is formed inside the central bluff body; the third electrode is arranged on the inner wall of the central bluff body and can be encapsulated, and the fourth electrode is arranged on the outer wall of the central bluff body; the third electrode is connected to the second power supply, and the fourth electrode is grounded.

[0012] In one embodiment, when the plasma actuator is a first plasma actuator, or a first plasma actuator and a second plasma actuator; the projections of the first electrode and the second electrode in the radial direction of the premixing tube do not overlap;

[0013] When the plasma actuator is the second plasma actuator, or the first plasma actuator and the second plasma actuator; the projections of the third electrode and the fourth electrode in the radial direction of the premixing tube do not overlap.

[0014] In one embodiment, when the plasma actuator is a first plasma actuator and a second plasma actuator, the projections of the first electrode and the third electrode in the radial direction of the premixing tube overlap, and the projections of the second electrode and the fourth electrode in the radial direction of the premixing tube overlap.

[0015] In one embodiment, when the plasma actuator is a first plasma actuator, or a first plasma actuator and a second plasma actuator; along the flow direction of the premixed gas, the first electrode is located downstream of the second electrode and can be encapsulated; the axial distance between the head of the first electrode and the tail of the second electrode is 0-10 mm; the axial distance between the tail of the first electrode and the inlet of the combustion chamber is not less than 40 mm;

[0016] When the plasma exciter is a second plasma exciter, or a first plasma exciter and a second plasma exciter; the third electrode is located downstream of the fourth electrode and can be packaged; the axial distance between the head of the third electrode and the tail of the fourth electrode is 0-10mm; the axial distance between the tail of the third electrode and the entrance of the combustion chamber is not less than 30mm.

[0017] In one embodiment, when the plasma actuator is a first plasma actuator, the premixing tube is an insulating medium;

[0018] When the plasma actuator is a second plasma actuator, the central bluff body is an insulating medium;

[0019] When the plasma actuator is a first plasma actuator and a second plasma actuator; the premixing tube and the central bluff body are insulating media.

[0020] In one embodiment, when the plasma actuator is a first plasma actuator, or a first plasma actuator and a second plasma actuator; the first electrode and the second electrode are ring-shaped;

[0021] When the plasma actuator is the second plasma actuator, or the first plasma actuator and the second plasma actuator; the third electrode and the fourth electrode are ring-shaped;

[0022] Each electrode is a metal electrode.

[0023] In one embodiment, a swirl blade is provided in the premixed gas channel.

[0024] In one embodiment, when the plasma actuator is a first plasma actuator and a second plasma actuator, the first power supply and the second power supply are a common power supply.

[0025] In one embodiment, the first power supply and the second power supply are sinusoidal AC high-voltage power supplies with a peak-to-peak voltage of 0-40 kV and a frequency range of 1-100 kHz; or, the first power supply and the second power supply are nanosecond pulse power supplies or microsecond pulse power supplies with an output voltage of 0-20 kV, a repetition frequency of 5-100 kHz, a rising edge and a falling edge range of 50-500 ns, and the polarity of the pulse power supply is unipolar or bipolar; or, the first power supply and the second power supply are any combination of an AC high-voltage power supply and a pulse power supply.

[0026] The present invention also provides a method for preventing flashback using the surface dielectric barrier discharge flashback prevention device based on flow control, wherein a premixed gas of hydrogen-rich fuel or pure hydrogen fuel is introduced into the premixed gas channel to form a stable V-shaped flame in the combustion chamber. When the combustion condition is close to flashback:

[0027] If the plasma actuator is a first plasma actuator, starting a first power supply to generate plasma inside the premixing tube near the second electrode;

[0028] If the plasma actuator is a second plasma actuator, starting a second power supply to generate plasma outside the central bluff body near the fourth electrode;

[0029] If the plasma actuator is a first plasma actuator and a second plasma actuator, the first power supply and the second power supply are started to simultaneously generate plasma inside the premixing tube near the second electrode and outside the central bluff body near the fourth electrode;

[0030] The flow field of the inner wall of the premixing tube and / or the outer wall of the central bluff body is changed by the flow control effect of the plasma, so as to suppress the flashback of the boundary layer along the premixing tube and / or the central bluff body.

[0031] Compared with the prior art, the present invention utilizes plasma-stimulated flow control, which is an electrically excited, fast-response and actively regulated method. After the power supply is turned on, the discharge plasma responds quickly, and by changing the boundary layer flow field, the ion wind is introduced to increase the flow velocity of the boundary layer, thereby suppressing flashback and increasing the stable combustion range. From the preliminary experimental results, at the same flow rate, the application of plasma can significantly increase the flashback limit equivalent ratio and expand the stable combustion range. Therefore, the surface dielectric barrier discharge flashback prevention method based on flow control proposed by the present invention has important application potential. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a schematic structural diagram of the premixed blunt body swirl model combustion chamber of the coupled plasma device of the present invention.

[0033] Figure 2 Schematic diagram of the premixed bluff body swirl model combustion chamber used in the present invention.

[0034] Figure 3 It is a schematic diagram of applying plasma discharge on the central bluff body of the present invention.

[0035] Figure 4 Schematic diagram of applying plasma discharge on the premixing tube of the present invention.

[0036] Figure 5 It is a schematic diagram of simultaneously applying plasma discharge to the central blunt body and the premixing tube of the present invention.

[0037] Figure 6 Schematic diagram of flow field velocity distribution at different heights in the premixing tube. DETAILED DESCRIPTION

[0038] The embodiments of the present invention are described in detail below with reference to the accompanying drawings and examples.

[0039] The traditional method of controlling flashback is to design and optimize the nozzle and prevent flashback through mechanical structure. However, this is a typical passive control method and can only “prevent” flashback. When the design conditions are exceeded and “prevention” is impossible, and flashback has already occurred, no intervention can be performed.

[0040] like Figure 1 and Figure 2 As shown, the present invention first provides a surface dielectric barrier discharge anti-flashback device based on flow control, which mainly includes a premixing tube 6, a central blunt body 2 and a plasma exciter, which acts on the combustion chamber 1, and the purpose is to control the flashback when flashback occurs in the combustion chamber 1.

[0041] The central bluff body 2 is coaxially arranged in the premixing tube 6 along the axial direction, and a premixed gas channel is formed between the two, wherein a chamber can be formed inside the central bluff body 2 to arrange electrodes. The end of the premixed gas channel is connected to the air inlet end of the combustion chamber 1, and the premixed gas enters the combustion chamber 1 through the premixed gas channel. The premixed gas of the present invention can be a mixture of any combustible gas and oxygen-containing gas, and is particularly suitable for hydrogen-rich gas or pure hydrogen gas.

[0042] The plasma actuator is the main functional part of the present invention. In the present invention, it can have three components: a first plasma actuator, a second plasma actuator, or a combination of the first plasma actuator and the second plasma actuator.

[0043] The first plasma exciter of the present invention mainly includes a premixing tube 6, a first electrode 5, a second electrode 7 and a first power supply 16-1; wherein the first electrode 5 is arranged on the outer wall of the premixing tube 6 and can be encapsulated, the second electrode 7 is arranged on the inner wall of the premixing tube 6, the first electrode 5 is connected to the first power supply 16-1, and the second electrode 7 is grounded.

[0044] The second plasma exciter of the present invention mainly includes a central bluff body 2, a third electrode 4, a fourth electrode 8 and a second power supply 16-2; wherein the third electrode 4 is arranged on the inner wall of the central bluff body 2 and can be encapsulated, and the fourth electrode 8 is arranged on the outer wall of the central bluff body 2; the third electrode 4 is connected to the second power supply 16-2, and the fourth electrode 8 is grounded.

[0045] The present invention can realize discharge excitation at different positions by arranging two pairs of electrodes in the premixing tube 6 and the central bluff body 2.

[0046] In the description of the present invention, when the first electrode 5, the second electrode 7 and the first power supply 16-1 are mentioned, it is considered that the plasma actuator of the present invention includes the first plasma actuator or only the first plasma actuator. Similarly, when the third electrode 4, the fourth electrode 8 and the second power supply 16-2 are mentioned, it is considered that the plasma actuator of the present invention includes the second plasma actuator or only the second plasma actuator.

[0047] According to the above structure, when the present invention is applied, a premixed gas of hydrogen-rich fuel or pure hydrogen fuel is introduced into the premixed gas channel to form a stable V-shaped flame in the combustion chamber 1. When the combustion condition is close to backfire, combustion instability occurs in the combustion chamber, accompanied by flame propagation upstream of the combustion chamber. At this time, the following method for preventing backfire can be performed:

[0048] Start the first power supply 16-1, apply high voltage to the first electrode 5, form a dielectric barrier discharge along the inner wall of the premixing tube 6, thereby generating a plasma jet inside the premixing tube 6 near the second electrode 7, causing ion wind, changing the flow field structure of the inner wall of the premixing tube 6, and suppressing the boundary layer flashback along the premixing tube 6; or,

[0049] Start the second power supply 16-2 to apply high voltage to the third electrode 4, form a dielectric barrier discharge along the wall of the central bluff body 2, thereby generating a plasma jet 17 outside the central bluff body 2 near the fourth electrode 8, causing ion wind, changing the flow field structure of the outer wall of the central bluff body 2, and suppressing the boundary layer flashback along the central bluff body 2; or,

[0050] The first power supply 16-1 and the second power supply 16-2 are started to generate surface dielectric barrier discharge at the central bluff body 2 and the premixing tube 6 simultaneously, and plasma jets are generated at the inner side of the premixing tube 6 near the second electrode 7 and the outer side of the central bluff body 2 near the fourth electrode 8, thereby causing ion wind, which can simultaneously suppress the flashback of the boundary layers along the central bluff body 2 and the premixing tube 6.

[0051] This results in three working modes, namely, discharge in the premixing tube 6 alone, discharge on the central bluff body 2 alone, and simultaneous discharge coupling to synergistically generate plasma.

[0052] The flow field of the inner wall of the premixing tube 6 and / or the outer wall of the central bluff body 2 is changed by the flow control effect of the plasma, and the boundary layer flashback along the premixing tube 6 and / or the central bluff body 2 can be effectively suppressed by increasing the flow velocity by the ion wind.

[0053] As the fourth state of matter, plasma has thermal, chemical kinetic and fluid dynamic effects on combustion. Plasma combustion regulation is an electrically excited, high-frequency, fast-response and actively regulated method. The present invention is based on an active regulation method of plasma flow control to suppress the combustion instability flashback phenomenon in the gas turbine combustion chamber. Compared with traditional anti-flashback methods, the method of the present invention is an electrically excited, fast-response and actively regulated method. The boundary layer flow field is changed by generating plasma through discharge, and the introduction of ion wind increases the flow velocity of the boundary layer, thereby suppressing flashback and increasing the stable combustion range.

[0054] The plasma generated by the two pairs of electrodes of the present invention respectively acts on the flow field near the wall of the premixing tube 6 and the flow field near the wall of the central bluff body 2. When the local flow velocity is lower than the flame velocity, the flame will propagate upstream. The flow velocity near the wall is generally low, which is easy to cause boundary layer flashback. Therefore, through plasma flow control, it is possible to actively control and change the flow field structure of the wall of the premixing tube 6 and the wall of the central bluff body 2 to avoid flashback. The surface dielectric barrier discharge at the two positions has a significant effect on preventing flashback. In practical applications, it can be applied separately or simultaneously to achieve the synergistic effect of the two plasmas, so that the boundary layer flashback along the wall of the premixing tube 6 and along the wall of the central bluff body 2 is effectively suppressed.

[0055] It is worth noting that the premixing tube 6, the central bluff body 2 and the combustion chamber 1 of the present invention are the main parts of the premixed bluff body swirl model combustion chamber in the gas turbine, so the present invention is particularly suitable for the premixed bluff body swirl model combustion chamber and the gas turbine using the premixed bluff body swirl model combustion chamber. Figure 1 and Figure 2 , including an air inlet 15, a fuel inlet 14, a venturi mixing tube 13, a mixing tube 11, a swirl blade 9, the premixing tube 6, the central bluff body 2 and the combustion chamber 1; the swirl blade 9 is installed in the premixing gas channel, and the central bluff body 2 is coaxially arranged at the center of the premixing tube 6. The combination of swirl and central bluff body can better stabilize the flame and make the fuel burn better. The combustion chamber 1 is preferably a visual combustion chamber, and the premixing tube 6 is preferably a visual premixing tube. Quartz glass is used to provide a visual window and facilitate laser diagnostic measurement. The tail end of the premixing tube 6 is assembled on the combustion chamber 1 through the cover plate 3, and the combustion chamber 1 and the premixing tube cover plate 3 are assembled by threaded connection. The head end of the premixing tube 6 is assembled on the mixing tube 11 through the combustion chamber support base 10, and the swirl blade 9 is installed on the combustion chamber support base 10 to generate a swirl flow field. The number and angle of the swirl blades 9 are adjustable. The central bluff body 2 is used to stabilize the flame and can also be installed on the combustion chamber support base 10. A rectifying plate 12 may be provided at the tail end of the venturi mixing tube 13. Air and fuel enter from the air inlet 15 and the fuel inlet 14 respectively, are mixed in the venturi mixing tube 13, are rectified by the rectifying plate 12, are further mixed in the mixing tube 11, and then enter the combustion chamber 1 through the swirl blades 9 and the central bluff body 2 installed downstream for ignition and combustion.

[0056] In one embodiment of the present invention, the radial projections of the first electrode 5 and the second electrode 7 in the premixing tube 6 do not overlap, the first electrode 5 and the second electrode 7 are asymmetrically arranged on both sides of the premixing tube 6, and the gap is 0-10mm; the radial projections of the third electrode 4 and the fourth electrode 8 in the premixing tube 6 do not overlap; the third electrode 4 and the fourth electrode 8 are asymmetrically arranged on both sides of the central bluff body 2, and the gap is 0-10mm. The first electrode 5 and the third electrode 4 are encapsulated, which will suppress the discharge of the first electrode 5 and the third electrode 4, and can effectively generate surface dielectric barrier discharge near the second electrode 7 and the fourth electrode 8 and reduce power consumption.

[0057] In one embodiment of the present invention, the radial projections of the first electrode 5 and the third electrode 4 in the premixing tube 6 overlap, and the radial projections of the second electrode 7 and the fourth electrode 8 in the premixing tube 6 overlap. When the first and second plasma actuators are applied at the same time, plasma can be generated synergistically to regulate the flow field on the inner wall of the premixing tube 6 and the outer wall of the central blunt body 2.

[0058] In one embodiment of the present invention, the premixing tube 6 is an insulating medium, separating the first electrode 5 and the second electrode 7 on both sides of the insulating medium. The central blunt body 2 is an insulating medium, separating the third electrode 4 and the fourth electrode 8 on both sides of the insulating medium. All electrodes of the present invention are metal electrodes.

[0059] In one embodiment of the present invention, the first electrode 5 and the second electrode 7 are annular, with a wall thickness of 0.05 mm. The two electrodes are respectively attached to the outer side and the inner side of the premixing tube wall 6. Along the flow direction of the premixed gas, the first electrode 5 is located downstream of the second electrode 7, and the axial distance between the two electrodes is 0-10 mm. The second electrode 7 is connected to the combustion chamber support base 10 as a grounding electrode, and the first electrode 5 is connected to the high-voltage output end of the plasma power supply 16 as a high-voltage electrode. The distance from the tail of the first electrode 5 to the combustion chamber entrance is not less than 40 mm. The second electrode 7 can be a stainless steel sleeve or copper foil, and the first electrode 5 can be a stainless steel mesh or copper foil. The material of the premixing tube 6 is a visual insulating material, quartz, with a wall thickness of 2 mm.

[0060] The third electrode 4 and the fourth electrode 8 are annular, with a wall thickness of 0.05mm. The two electrodes are respectively attached to the inner and outer sides of the central bluff body 2. Along the flow direction of the premixed gas, the fourth electrode 8 is located downstream of the third electrode 4; the axial distance between the two electrodes is 0-10mm. The fourth electrode 8 is connected to the combustion chamber support base 10 as a grounding electrode, and the axial distance from the tail of the third electrode 4 to the entrance of the combustion chamber 1 is not less than 30mm. The third electrode 4 is connected to the high-voltage output end of the second power supply 16-2 through a high-voltage wire 19 wrapped in an insulating ceramic tube 18. The fourth electrode 8 can be a stainless steel casing or copper foil, and the third electrode 4 can be a copper ring or a stainless steel ring. The material of the central bluff body 2 is an insulating material, quartz or ceramic, with a wall thickness of 2mm.

[0061] In one embodiment of the present invention, the first power supply 16-1 and the second power supply 16-2 can select a common power supply 16, that is, the present invention can be a power supply that works alone, or two power supplies that work simultaneously. The first power supply 16-1 and the second power supply 16-2 are sinusoidal AC high voltage power supplies with a peak-to-peak voltage of 0-40kV and a frequency range of 1-100kHz; or, the first power supply 16-1 and the second power supply 16-2 are nanosecond pulse power supplies or microsecond pulse power supplies with an output voltage of 0-20kV, a repetition frequency of 5-100kHz, a rising edge and a falling edge range of 50-500ns, and the polarity of the pulse power supply is unipolar or bipolar.

[0062] The power supply type of the plasma actuator of the present invention can be AC ​​and pulse mode, that is, AC power supply, pulse power supply, or a combination of the two power supplies. For example, the surface dielectric barrier discharge is usually driven by a sinusoidal high voltage. Higher voltage and frequency can increase the ion wind speed generated by the plasma actuator. The pulse power supply can also generate surface dielectric barrier discharge and can also perform flow control.

[0063] In the specific application of the present invention, the size, shape and position of each electrode must be designed first, and then the circuit is connected through wires. As needed, the discharge state and effect can be detected by a high-voltage probe, a current coil and an oscilloscope, so as to optimize and select appropriate discharge parameters.

[0064] like Figure 3 , showing the working mode of the present invention of discharging on the central bluff body 2 alone, the second power supply 16-2 selects a sinusoidal AC high voltage power supply.

[0065] The third electrode 4 and the fourth electrode 8 are arranged closely on the inner and outer sides of the central bluff body 2, respectively. The third electrode 4 and the fourth electrode 8 are both annular electrodes. The third electrode 4 is used as a high-voltage electrode and is connected to the high-voltage output end of the power supply 16 through a high-voltage wire 19 wrapped by a ceramic insulating tube 18. At the same time, the ceramic insulating tube 18 plays a packaging role; the fourth electrode 8 is connected to the combustion chamber support base 10 as a grounding electrode, forming a closed circuit loop. The axial distance between the third electrode 4 and the fourth electrode 8 is 0 mm, and the axial distance from the tail of the third electrode 4 to the entrance of the combustion chamber 1 is 30 mm. A premixed gas of hydrogen-rich or pure hydrogen fuel is introduced into the combustion chamber 1 to form a stable V-shaped flame in the combustion chamber 1. When the combustion condition is close to flashback, combustion instability occurs in the combustion chamber, and the high-voltage power supply 16 is started, so that a plasma jet 17 is generated near the fourth electrode 8 on the outer side of the central bluff body 2. The flow field of the outer wall of the central bluff body 2 is changed by the plasma flow control function. The flashback along the boundary layer of the central bluff body 2 can be effectively suppressed by increasing the flow rate by the ion wind.

[0066] like Figure 4 , showing the working mode of the present invention of discharging in the premixing tube 6 alone, the first power supply 16-1 selects a sinusoidal AC high voltage power supply.

[0067] The second electrode 7 and the first electrode 5 are closely arranged on the inner and outer sides of the premixing tube 6, respectively. The first electrode 5 and the second electrode 7 are both annular electrodes. The first electrode 5 is used as a high-voltage electrode and is encapsulated, and is connected to the high-voltage output end of the power supply 16 through a high-voltage wire 19; the second electrode 7 is connected to the combustion chamber support base 10 as a grounding electrode, forming a closed circuit loop. The axial distance between the first electrode 5 and the second electrode 7 is 0 mm, and the axial distance from the tail of the first electrode 5 to the entrance of the combustion chamber 1 is 40 mm. When the combustion condition is close to flashback, the power supply 16 is started to generate a plasma jet 17 near the second electrode 7 inside the premixing tube 6. The flow field on the inner wall of the premixing tube 6 is changed by the plasma flow control action. The boundary layer flashback along the wall of the premixing tube 6 can be effectively suppressed by increasing the flow rate through the ion wind.

[0068] like Figure 5 , showing the working mode of the present invention in which discharge coupling is simultaneously performed in the central bluff body 2 and the premixing tube 6 to synergistically generate plasma, and the first power supply 16-1 and the second power supply 16-2 are selected as sinusoidal AC high voltage power supplies.

[0069] The third electrode 4 and the fourth electrode 8 are closely arranged on the inner and outer sides of the central blunt body 2, respectively, and the second electrode 7 and the first electrode 5 are closely arranged on the inner and outer sides of the premixing tube 6, respectively. The third electrode 4 is used as a high-voltage electrode, and is connected to the high-voltage output end of the second power supply 16-2 through a high-voltage wire 19 wrapped in a ceramic insulating tube 18; the first electrode 5 is used as a high-voltage electrode and is encapsulated, and is connected to the high-voltage output end of the first power supply 16-1 through a high-voltage wire; the second electrode 7 and the fourth electrode 8 are connected to the combustion chamber support base 10 as grounding electrodes. The axial distance between the third electrode 4 and the fourth electrode 8 is 0 mm, and the axial distance from the tail of the third electrode 4 to the entrance of the combustion chamber 1 is 30 mm. The axial distance between the first electrode 5 and the second electrode 7 is 0 mm, and the axial distance from the tail of the first electrode 5 to the entrance of the combustion chamber 1 is 40 mm. When the combustion condition is close to flashback, the first power supply 16-1 and the second power supply 16-2 are started to generate a plasma jet near the fourth electrode 8 and the second electrode 7 on the outside of the central bluff body 2 and the inside of the premixing tube 6. The flow field of the outer wall of the central bluff body 2 and the inner wall of the premixing tube 6 is changed by the plasma flow control effect. The flashback of the boundary layer along the wall of the central bluff body 2 and the premixing tube 6 can be effectively suppressed by increasing the flow rate through the ion wind.

[0070] The present invention is verified by the following tests:

[0071] This experiment is a method for preventing flashback by dielectric barrier discharge along the surface based on flow control. A verification experiment was carried out for the working mode of discharge in the premixing tube 6 alone. The specific steps are as follows:

[0072] The second electrode 7 is closely arranged inside the premixing tube 6, and the first electrode 5 is closely arranged outside the premixing tube 6. The first electrode 5 is an annular copper mesh, and the second electrode 7 is an annular copper foil. The axial distance between the two electrodes is 0 mm, the thickness of the first electrode 5 is 30 mm, and the axial distance from its tail to the entrance of the combustion chamber 1 is 45 mm. A methane premixed gas with an equivalence ratio of 0.55 is introduced into the combustion chamber 1 and ignited. During the experiment, the inlet flow rate of the combustion chamber 1 is fixed at 2 m / s, and the swirl blade 9 is 45°. The fuel flow rate is slowly increased and the air flow rate is reduced through the mass flow meter to achieve the purpose of increasing the equivalence ratio. When the flame propagates upstream from the combustion chamber 1 to the premixing tube 6 by a V-shaped flame, it is considered that flashback occurs at this moment. The methane flow rate and air flow rate at this time are recorded, and the flashback limit equivalence ratio is obtained by calculation. The same steps are followed, and the first power supply 16-1 is ignited and started when the equivalence ratio is 0.55. At this time, purple filamentary plasma appears inside the premixing tube 6. Then the fuel flow rate is slowly increased and the air flow rate is reduced to increase the equivalence ratio until the methane flame propagates upstream back to the premixing tube 6. The flashback limit equivalence ratio when plasma is applied is calculated. When plasma is not applied, the methane flame flashback phenomenon occurs in a very short time. After plasma is applied, it can be found that the flashback process is delayed, and the flame does not immediately propagate upstream, but is "anchored" by the ion wind caused by the plasma, that is, it is stabilized between the premixing tube 6 and the combustion chamber 1, and slowly propagates upstream as the equivalence ratio continues to increase. After applying plasma, the methane flame flashback limit equivalence ratio can be extended from 0.64 to 0.7, which means that discharging in the premixing tube 6 alone can effectively suppress flashback and expand the stable combustion range. For practical applications, starting the first power supply 16-1 when approaching the backfire equivalence ratio can effectively avoid the backfire phenomenon and allow the operator to make operational adjustments in a timely manner, such as changing the combustion mode, increasing the flow rate or reducing the equivalence ratio, and changing the fuel pipeline.

[0073] The velocity distribution of the flow field at different height positions in the premixing tube 6 is as follows: Figure 6 As shown, it can be seen that the wall velocities of the central bluff body 2 and the premixing tube 6 are low and close to 0. Therefore, by applying surface dielectric barrier discharge in the central bluff body 2 and the premixing tube, the wall boundary layer velocity can be changed through the action of ion wind, thereby suppressing the flashback phenomenon.

[0074] In summary, the present invention applies surface dielectric barrier discharge (SDBD) in the premixing tube upstream of the combustion chamber or on the bluff body to generate a plasma jet, induces the flow of nearby gas through high-energy electron collisions, generates ion wind, and suppresses flashback by changing the flow field and boundary layer flow. Two pairs of electrodes are arranged in the premixing tube and on the bluff body, so that discharge excitation at different positions can be achieved. In practical applications, they can be applied separately, or the synergistic effect of two plasmas can be achieved, so that flashback along the wall of the premixing tube and along the boundary layer of the central bluff body is effectively suppressed. The present invention can control flashback in the combustion chamber through plasma excitation flow, avoid flashback when burning hydrogen-rich fuel or pure hydrogen fuel, increase the fuel flexibility of the gas engine, and expand the reliable operation range.

[0075] The above description is only a preferred embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical solution and invention patent concept of the present invention within the scope disclosed by the present invention, which shall fall within the protection scope of the present invention.

Claims

1. A surface dielectric barrier discharge anti-flashback device based on flow control, characterized in that: It comprises a premixing tube (6), a central blunt body (2) and a plasma actuator; The central bluff body (2) is axially disposed in the premixing tube (6), and a premixing gas channel is formed between the two. The end of the premixing gas channel is connected to the air inlet end of the combustion chamber (1), and a premixed gas of hydrogen-rich fuel or pure hydrogen fuel is introduced into the premixing gas channel; The plasma actuator is a first plasma actuator and / or a second plasma actuator; The first plasma exciter comprises a premixing tube (6), a first electrode (5), a second electrode (7) and a first power supply (16-1); the first electrode (5) is arranged on the outer wall of the premixing tube (6), and the second electrode (7) is arranged on the inner wall of the premixing tube (6); the first electrode (5) is connected to the first power supply (16-1), and the second electrode (7) is grounded; The second plasma exciter comprises a central bluff body (2), a third electrode (4), a fourth electrode (8) and a second power supply (16-2); a chamber is formed inside the central bluff body (2); the third electrode (4) is arranged on the inner wall of the central bluff body (2), and the fourth electrode (8) is arranged on the outer wall of the central bluff body (2); the third electrode (4) is connected to the second power supply (16-2), and the fourth electrode (8) is grounded.

2. The surface dielectric barrier discharge anti-flashback device based on flow control according to claim 1 is characterized in that: When the plasma actuator is a first plasma actuator, or a first plasma actuator and a second plasma actuator; the projections of the first electrode (5) and the second electrode (7) in the radial direction of the premixing tube (6) do not overlap; When the plasma actuator is the second plasma actuator, or the first plasma actuator and the second plasma actuator, the projections of the third electrode (4) and the fourth electrode (8) in the radial direction of the premixing tube (6) do not overlap.

3. The surface dielectric barrier discharge anti-flashback device based on flow control according to claim 1, characterized in that: When the plasma actuator is a first plasma actuator and a second plasma actuator, the radial projections of the first electrode (5) and the third electrode (4) on the premixing tube (6) overlap, and the radial projections of the second electrode (7) and the fourth electrode (8) on the premixing tube (6) overlap.

4. The surface dielectric barrier discharge anti-flashback device based on flow control according to claim 1, characterized in that: When the plasma actuator is a first plasma actuator, or a first plasma actuator and a second plasma actuator; along the flow direction of the premixed gas, the first electrode (5) is located downstream of the second electrode (7) and is encapsulated; the axial distance between the head of the first electrode (5) and the tail of the second electrode (7) is 0-10 mm, and cannot be 0; the axial distance between the tail of the first electrode (5) and the inlet of the combustion chamber (1) is not less than 40 mm; When the plasma actuator is a second plasma actuator, or a first plasma actuator and a second plasma actuator; the third electrode (4) is located downstream of the fourth electrode (8) and is encapsulated; the axial distance between the head of the third electrode (4) and the tail of the fourth electrode (8) is 0-10 mm, and cannot be 0; the axial distance between the tail of the third electrode (4) and the entrance of the combustion chamber (1) is not less than 30 mm.

5. The surface dielectric barrier discharge anti-flashback device based on flow control according to claim 1, characterized in that: When the plasma actuator is a first plasma actuator, the premixing tube (6) is an insulating medium; When the plasma actuator is a second plasma actuator, the central bluff body (2) is an insulating medium; When the plasma actuator is a first plasma actuator and a second plasma actuator; the premixing tube (6) and the central bluff body (2) are insulating media.

6. The surface dielectric barrier discharge anti-flashback device based on flow control according to claim 1, characterized in that: When the plasma actuator is a first plasma actuator, or a first plasma actuator and a second plasma actuator; the first electrode (5) and the second electrode (7) are ring-shaped; When the plasma actuator is the second plasma actuator, or the first plasma actuator and the second plasma actuator; the third electrode (4) and the fourth electrode (8) are ring-shaped; Each electrode is a metal electrode.

7. The surface dielectric barrier discharge anti-flashback device based on flow control according to claim 1, characterized in that: The premixed gas channel is provided with a swirl blade (9).

8. The surface dielectric barrier discharge anti-flashback device based on flow control according to claim 1, characterized in that: When the plasma actuator is a first plasma actuator and a second plasma actuator, the first power source (16-1) and the second power source (16-2) are a common power source (16).

9. The surface dielectric barrier discharge anti-flashback device based on flow control according to claim 1 or 8, characterized in that: The first power supply (16-1) and the second power supply (16-2) are sinusoidal AC high-voltage power supplies, with a peak-to-peak voltage of 0-40 kV and cannot be 0, and a frequency range of 1-100 kHz; or, the first power supply (16-1) and the second power supply (16-2) are nanosecond pulse power supplies or microsecond pulse power supplies, with an output voltage of 0-20 kV and cannot be 0, a repetition frequency of 5-100 kHz, a rising edge and a falling edge range of 50-500 ns, and the polarity of the pulse power supply is unipolar or bipolar; or, the first power supply (16-1) and the second power supply (16-2) are any combination of an AC high-voltage power supply and a pulse power supply.

10. A method for preventing flashback using the surface dielectric barrier discharge flashback prevention device based on flow control according to claim 1, characterized in that: A premixed gas of hydrogen-rich fuel or pure hydrogen fuel is introduced into the premixed gas passage to form a stable V-shaped flame in the combustion chamber (1). When the combustion condition is close to flashback: If the plasma actuator is a first plasma actuator, a first power source (16-1) is started to generate plasma inside a premixing tube (6) near the second electrode (7); If the plasma actuator is a second plasma actuator, a second power source (16-2) is started to generate plasma outside the central bluff body (2) near the fourth electrode (8); If the plasma actuator is a first plasma actuator and a second plasma actuator, the first power source (16-1) and the second power source (16-2) are started to simultaneously generate plasma inside the premixing tube (6) near the second electrode (7) and outside the central bluff body (2) near the fourth electrode (8); The flow field of the inner wall surface of the premixing tube (6) and / or the outer wall surface of the central bluff body (2) is changed by the flow control effect of the plasma, thereby suppressing the flashback of the boundary layer along the premixing tube (6) and / or the central bluff body (2).

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