A plasma ignition and combustion-supporting device for a sub-combustion ramjet combustion chamber with retractable electrodes

Abstract

The present invention provides a plasma ignition and combustion-supporting device for a subcombustion ramjet combustion chamber with a retractable electrode, comprising a combustion chamber barrel (1), a circumferential flame stabilizer (2), a guide rail (3), a fixed-axis sleeve (4), a slider (5), a hinged seat (6), a slide rod (7), a ceramic tube (8), and a high-voltage electrode (9). A plasma ignition and combustion-supporting method for a subcombustion ramjet combustion chamber with a retractable electrode is also provided. The present invention is used to solve the problem that the electrode of a plasma excitation device is ablated, resulting in a short working life. The present invention adopts an innovative telescopic device on the combustion chamber barrel, which can realize the telescopic movement of a metal electrode with a simple structure, reduce electrode ablation, and extend the electrode life.

Description

Technical Field

[0001] The invention relates to the field of aviation engines, and in particular to a plasma ignition and combustion-supporting device for a ramjet combustion chamber with retractable electrodes. Background Art

[0002] Turbine engines have good performance within the flight Mach number of 2.0, while ramjet engines are suitable for operation above Mach 3.0. During the conversion process between turbine mode and ramjet mode, the ramjet combustion chamber of the turbine-based combined cycle (TBCC) engine has problems such as difficulty in ignition and low combustion efficiency, which significantly reduces the engine thrust. Currently, most of the existing studies have been carried out using conventional geometric optimization methods, which have problems such as narrow adjustable parameter range and limited effect.

[0003] The evaporative flame holder is a widely used structure in the ramjet combustion chamber. Its geometric structure and working principle are similar to those of the afterburner of a turbine engine. Existing research results have shown that applying plasma excitation has shown good effects in broadening the flameout boundary of the combustion chamber, enhancing fuel activity, and improving combustion efficiency.

[0004] The plasma excitation applied in the combustion chamber only plays an ignition and auxiliary combustion role during the conversion process between the turbine mode and the ramjet mode. When the engine works in a single mode, there is no need to discharge to generate plasma, but the high-voltage electrode is continuously in a high-temperature environment, which reduces the service life and performance of the material to a certain extent.

[0005] In summary, the flame stabilizer plasma excitation device in the prior art has the disadvantages of severe electrode ablation, short working life and low working efficiency. Therefore, there is an urgent need for a plasma ignition and combustion-supporting device that avoids electrode ablation, has a longer working life and higher working efficiency. Summary of the invention

[0006] Based on the above problems, the present invention provides a plasma ignition and combustion-supporting device for a sub-combustion ramjet combustion chamber with a retractable electrode, comprising a combustion chamber cylinder 1, a circumferential flame stabilizer 2, a guide rail 3, a fixed axis sleeve 4, a slider 5, a hinge seat 6, a slide rod 7, a ceramic tube 8, and a high-voltage electrode 9; wherein

[0007] The combustion chamber barrel 1 is in the shape of a hollow cylinder and is made of a high-temperature alloy;

[0008] The circumferential flame stabilizer 2 is installed inside the combustion chamber barrel 1 and is coaxial with the combustion chamber barrel 1. It is fixed inside the combustion chamber barrel through a connecting device and is arranged close to the inlet end of the combustion chamber barrel 1.

[0009] The guide rail 3 has a rectangular groove inside, which is opened on the outer shell of the combustion chamber barrel 1 along a direction parallel to the axis of the combustion chamber barrel 1;

[0010] The slider 5 is installed on the guide rail 3 and slides freely along the guide rail 3;

[0011] The slide bar 7 is a broken line rod, including a first folding part and a second folding part. The free end of the first folding part is connected to the hinge seat 6 on the slide block 5 through a fixing pin, and the second folding part is fixedly connected to the first folding part with a certain angle. The ceramic tube 8 is in the shape of a hollow cylinder, one end of the ceramic tube 8 is glued and fixed to the free end of the second folding part of the slide bar 7, and the other end is suspended. When the plasma excitation device is working, it goes deep into the combustion chamber cylinder 1, and when the excitation device is not working, it exits the combustion chamber cylinder 1.

[0012] The high-voltage electrode 9 is installed inside the ceramic tube 8. The diameter of the high-voltage electrode 9 is equal to or slightly smaller than the inner diameter of the ceramic tube 8, so that it can be inserted into the ceramic tube 8. At the end of the ceramic tube 8 connected to the slide bar 7, the high-voltage electrode 9 is flush with the ceramic tube 8 and connected to the high-voltage power supply. At the suspended end of the ceramic tube 8, the length of the high-voltage electrode 9 exceeds the ceramic tube 8 and is exposed to the air.

[0013] A displacement limiting hole is provided on the outer shell of the combustion chamber barrel 1 in the axial direction and upstream of the guide rail 3. The fixed axis sleeve 4 is installed in the displacement limiting hole through a fixing pin and can rotate around the fixing pin. A through hole is provided on the fixed axis sleeve 4, and its size is equal to or slightly larger than the outer diameter of the slide bar 7. The second folded portion of the slide bar 7 can pass through the through hole on the fixed axis sleeve 4 and can slide in the through hole.

[0014] The second folded portion of the slide rod 7 passes through the circular hole on the fixed axis sleeve 4, and the free end of the second folded portion is fixed to the ceramic tube 8. When the slider 5 moves axially in the guide rail 3, the ceramic tube 8 and the electrode 9 can be extended and retracted, making them move away from or close to the flame stabilizer 2.

[0015] In one embodiment of the present invention, the circumferential flame stabilizer 2 adopts an evaporation chamber flame stabilizer or an evaporation tube flame stabilizer commonly used in a ramjet combustion chamber, and is fixedly connected to the combustion chamber cylinder through a fixing device.

[0016] In a specific embodiment of the present invention, the turning angle between the second folding portion and the first folding portion is 150°.

[0017] In another embodiment of the present invention, the guide rail 3 is provided on the outer shell of the combustion chamber barrel 1 or directly provided on the combustion chamber barrel 1 , and the width and height of the slider 5 are adapted to the width and height of the guide rail 3 .

[0018] In another specific embodiment of the present invention, the guide rail has a length of 100 mm, a width of 10 mm, and a height of 8 mm. The slider 5 has a length of 50 mm, and the slider 5 can slide on the guide rail 3 .

[0019] In another specific embodiment of the present invention,

[0020] The combustion chamber cylinder 1 has a wall thickness of 9.4 mm, an inner diameter of 234 mm, and a length of 500 mm;

[0021] The fixed axis sleeve 4 has a bottom diameter of 8 mm and a height of 8 mm, and a through hole with a diameter of 4 mm is provided on the side wall;

[0022] The diameter of the hinge hole is 2mm;

[0023] The sliding rod 7 and the ceramic tube 8 are bonded and connected by high temperature glue;

[0024] The diameter of the high-voltage electrode 9 is 2 mm, and the high-voltage electrode 9 is exposed 1-2 mm from the end of the ceramic tube 8;

[0025] The inner diameter of the ceramic tube 8 is 2 mm and the outer diameter is 4 mm. The high-voltage electrode 9 is inserted into the ceramic tube 8 and fixed with high-temperature glue.

[0026] A method for plasma ignition and combustion support in a subcombustion ramjet combustion chamber with retractable electrodes is based on the above-mentioned plasma ignition and combustion support device in a subcombustion ramjet combustion chamber with retractable electrodes, specifically: when a TBCC engine switches from a turbine mode to a ramjet mode, a slider 5 moves along a guide rail 3 toward a flame stabilizer 2, and the slider 5 and a slide rod 7 are connected together through a hinge hole on a hinge seat 6. When the slider 5 moves axially in the guide rail, the slide rod 7 is driven to rotate through the hinge seat 6; a ceramic tube 8 connected to the slide rod 7 extends out of a through hole in a fixed axis sleeve 4 toward a flame stabilizer, and a high-voltage electrode 9 in the ceramic tube 8 extends into the flame stabilizer as an anode, and the wall of the flame stabilizer serves as a cathode. When the voltage is high enough, the air between the two electrodes is broken down to generate plasma.

[0027] The electrode-retractable subcombustion ramjet combustion chamber plasma ignition and combustion-supporting device provided by the present invention is used to solve the problems of severe electrode ablation, short working life and low working efficiency of the stabilizer excitation device in the prior art. In the present invention, the layout of the evaporative flame stabilizer matches the combustion chamber cylinder, and only an innovative telescopic device is used on the combustion chamber cylinder, so that the electrode-retractable subcombustion ramjet combustion chamber plasma ignition and combustion-supporting device can avoid high-temperature ablation, have a longer working life and higher working efficiency.

[0028] The advantages of the present invention are as follows:

[0029] The sliding of the slider in the guide rail drives the slide rod to move, and the ceramic tube connected to the slide rod, under the restriction of the fixed axis sleeve, realizes the extension and retraction movement of the high-voltage electrode in the combustion chamber cylinder toward the flame stabilizer.

[0030] The high-voltage electrode forms a sliding arc with the wall in the flame stabilizer, and the plasma generated by the sliding arc discharge activates the fuel, thereby improving the ignition performance of the ramjet combustion chamber and improving the combustion efficiency and combustion stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the implementation of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art are briefly introduced below.

[0032] Figure 1 It is a front view structural diagram of the present invention;

[0033] Figure 2 It is a schematic top view of the structure of the present invention;

[0034] Figure 3 It is a three-dimensional structural diagram of the telescopic assembly of the present invention.

[0035] Figure numerals: ① combustion chamber cylinder, ② flame stabilizer, ③ guide rail, ④ fixed axis sleeve, ⑤ slider, ⑥ hinge seat, ⑦ slide rod, ⑧ ceramic tube, ⑨ high voltage electrode. DETAILED DESCRIPTION

[0036] In order for those skilled in the art to better understand the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and the following embodiments.

[0037] Embodiment 1:

[0038] like Figure 1 As shown, a plasma ignition and combustion-supporting device for a sub-combustion ramjet combustion chamber with a retractable electrode includes a combustion chamber barrel 1, a circumferential flame stabilizer 2, a guide rail 3, a fixed axis sleeve 4, a slider 5, a hinged seat 6, a slide rod 7, a ceramic tube 8, and a high-voltage electrode 9.

[0039] The combustion chamber barrel 1 is in the shape of a hollow cylinder and is made of a high-temperature alloy.

[0040] The circumferential flame stabilizer 2 is installed inside the combustion chamber barrel 1 and is coaxial with the combustion chamber barrel 1. It is arranged near the inlet end of the combustion chamber barrel 1. The circumferential flame stabilizer 2 can adopt an evaporation chamber flame stabilizer or an evaporation tube flame stabilizer commonly used in a sub-combustion ramjet combustion chamber (Liu Ran, Liu Yuying, Gao Zhao. Research on the influence of structural parameters on the lean oil flameout performance of evaporation flame stabilizer and its prediction method [J]. Propulsion Technology, 2017, 38(12): 2753-2760. DOI: 10.13675 / j.cnki.tjjs.2017.12.014.), for example, through three connecting lugs evenly distributed around the circumference, and fixed to the combustion chamber barrel by bolts.

[0041] like Figure 1 AA cross section and Figure 2 As shown, the guide rail 3 is a rectangular groove, and its cross-sectional shape is similar to that of the slider 5. For example, by designing inwardly protruding fixed edges on the two sides of the upper surface of the guide rail 3 parallel to the extension direction of the guide rail, the slider 5 can be constrained in the guide rail 3 (this method is well known to those skilled in the art and will not be described again), or other techniques well known to those skilled in the art can be used to constrain the slider 5 in the guide rail 3 and make it slide in the guide rail 3 along the direction of the axis of the combustion chamber barrel 1.

[0042] The slider 5 is installed on the guide rail 3 and can slide freely along the guide rail 3 .

[0043] like Figure 3 As shown, the slide rod 7 is a broken line rod, including a first folding portion and a second folding portion. The free end of the first folding portion is connected to the hinge seat 6 on the slider 5 through a fixing pin, and the turning angle between the second folding portion and the first folding portion is 150°.

[0044] The ceramic tube 8 is in the shape of a hollow cylinder. When the plasma excitation device is working, it goes deep into the combustion chamber barrel 1. When the excitation device is not working, it exits the combustion chamber barrel 1. One end of the ceramic tube 8 is glued and fixed to the free end of the second folded portion of the slide rod 7, and the other end is suspended.

[0045] The high-voltage electrode 9 is installed inside the ceramic tube 8. The diameter of the high-voltage electrode 9 is equal to or slightly smaller than the inner diameter of the ceramic tube 8, so that it can be inserted into the ceramic tube 8. The high-voltage electrode 9 is exposed at the suspended end of the ceramic tube 8 to achieve plasma discharge. At the end of the ceramic tube 8 connected to the slide bar 7, the high-voltage electrode 9 is flush with the ceramic tube 8 and connected to a high-voltage power supply (for example, a wire is directly drawn out from the place where the slide bar 7 and the ceramic tube 8 are connected, and then connected to the power supply); and at the suspended end of the ceramic tube 8, the length of the high-voltage electrode 9 exceeds the ceramic tube 8 and is exposed in the air to achieve air breakdown discharge.

[0046] A displacement limiting hole is provided on the outer shell of the combustion chamber barrel 1 axially upstream of the guide rail 3 (on the side close to the flame stabilizer 2 ), and the fixed axis sleeve 4 is installed in the displacement limiting hole through a fixing pin and can rotate around the fixing pin.

[0047] The fixed-axis sleeve 4 is provided with a through hole, the size of which is equal to or slightly larger than the outer diameter of the slide bar 7 , so that the second folded portion of the slide bar 7 can pass through the through hole on the fixed-axis sleeve 4 and slide in the through hole.

[0048] The second folded portion of the slide rod 7 passes through the circular hole on the fixed axis sleeve 4, and the free end of the second folded portion is glued and fixed to the ceramic tube 8. Through the above structure, when the slider 5 moves axially in the guide rail 3, the ceramic tube 8 and the electrode 9 can be extended and retracted, making them move away from or close to the flame stabilizer 2.

[0049] Working principle: When the TBCC engine switches from turbine mode to ramjet mode, the slider 5 moves along the guide rail 3 toward the flame stabilizer 2. The slider 5 and the slide rod 7 are connected together through the hinge hole on the hinge seat 6. When the slider 5 moves axially in the guide rail, the slide rod 7 is driven to rotate through the hinge seat 6. The ceramic tube 8 connected to the slide rod 7 extends in the through hole of the fixed axis sleeve 4 toward the flame stabilizer. The high-voltage electrode 9 in the ceramic tube 8 extends into the flame stabilizer as an anode, and the wall of the flame stabilizer serves as a cathode. When the voltage is high enough, the air between the two electrodes is broken down to generate plasma. In the present invention, an innovative telescopic device is used on the combustion chamber cylinder to avoid the flame from ablating the electrode when plasma generation is not required, thereby extending the working life of the plasma ignition and combustion-supporting device.

[0050] like Figure 1-2 As shown, in a specific embodiment of the present invention:

[0051] The guide rail 3 is arranged on the outside of the combustion chamber cylinder 1, and the slider 5 is embedded in the guide rail 3; the guide rail has a length of 100 mm, a width of 10 mm, and a height of 8 mm; the slider 5 has a length of 50 mm, a width of 10 mm, and a height of 8 mm (in fact, the width and height of the slider 5 can be slightly smaller than the width and height of the guide rail slider 5 to facilitate sliding therein). The reciprocating motion of the slider in the guide rail is controlled by the inlaid structure.

[0052] The guide rail 3 is directly opened on the combustion chamber barrel 1, which ensures that the telescopic device occupies less space and can also make the structure of the present invention simpler. The width of the slider 5 is equal to the width of the guide rail 3, which ensures that the slider 5 can only achieve reciprocating motion in a single direction in the guide rail. In fact, the guide rail 3 can be directly opened on the combustion chamber barrel, or it can be additionally fixed on the outer surface of the combustion chamber. In order to reduce weight, it is chosen here to directly groove the combustion chamber barrel as the guide rail 3.

[0053] like Figure 1-3 As shown, in another specific embodiment of the present invention:

[0054] The combustion chamber cylinder 1 has a wall thickness of 9.4 mm, an inner diameter of 234 mm, and a length of 500 mm.

[0055] The fixed axis sleeve 4 has a bottom diameter of 8 mm and a height of 8 mm, and a through hole with a diameter of 4 mm is provided on the side wall.

[0056] The slider 5 is connected to the slide rod 7 through the hinge seat 6 located thereon, and the diameter of the hinge hole is 2mm; the slide rod 7 and the ceramic tube 8 are bonded together by high-temperature glue; the high-voltage electrode 9 has a diameter of 2mm, the inner diameter of the ceramic tube 8 is 2mm, and the outer diameter is 4mm. The high-voltage electrode 9 is inserted into the ceramic tube 8 and fixed with high-temperature glue; through the displacement mechanism, the slider 5 can drive the high-voltage electrode 9 to telescopically move in the circumferential flame stabilizer 2 when it moves.

[0057] The structural form and layout scheme of the telescopic device can not only improve the ignition and combustion performance of the sub-combustion ramjet combustion chamber under low working conditions, but also avoid excessive ablation of the metal electrode and increase the life of the electrode.

[0058] The hinge hole on the slide bar 7 is connected to the hinge seat 6, so that the slide block 5 can drive the slide bar 7 to move when sliding in the guide rail 3, thereby realizing motion association.

[0059] The fixed-axis sleeve 4 is installed in the displacement limiting hole through a fixing pin and can rotate around the fixing pin.

[0060] The slide rod 7 and the ceramic tube 8 that penetrate into the combustion chamber barrel 1 are coaxial with the through hole of the fixed axis sleeve 4, so that the ceramic tube 8 can perform telescopic movement in the combustion chamber barrel 1 toward the flame stabilizer.

[0061] The sliding rod 7 has a bending angle of 150°, and the cross-section of the sliding rod 7 and the ceramic tube 8 are both circles with a diameter of 4 mm. They are fixed with high-temperature glue to ensure that when the sliding rod 7 moves, it can drive the ceramic tube 8 to achieve maximum telescopic movement in the combustion chamber cylinder 1.

[0062] A layer of ceramic tube 8 is nested outside the high-voltage electrode 9, and the length of the ceramic tube 8 should be able to ensure that it extends from the outside of the combustion chamber barrel 1 to the inside of the combustion chamber, and the high-voltage electrode 9 is only exposed by 1-2mm to ensure reliable insulation between the high-voltage electrode 9 and the combustion chamber barrel 1, so that discharge only occurs between the high and low voltage electrodes.

[0063] In fact, in the existing evaporative flame stabilizer plasma excitation device, the electrode is fixed, and although the structure is simple, high-temperature ablation is serious. The technical solution of the present invention is more complex in structure, but when plasma excitation is not required, the electrode can be retracted to avoid electrode ablation.

Claims

1. A plasma ignition and combustion-supporting device for a sub-combustion ramjet combustion chamber with a retractable electrode, characterized in that: It comprises a combustion chamber body (1), a circumferential flame stabilizer (2), a guide rail (3), a fixed axis sleeve (4), a slide block (5), a hinge seat (6), a slide rod (7), a ceramic tube (8), and a high-voltage electrode (9); in The combustion chamber barrel (1) is in the shape of a hollow cylinder and is made of a high-temperature alloy; The circumferential flame stabilizer (2) is installed inside the combustion chamber barrel (1) and is coaxial with the combustion chamber barrel (1). It is fixed inside the combustion chamber barrel through a connecting device and is arranged close to the inlet end of the combustion chamber barrel (1); The guide rail (3) has a rectangular groove inside and is opened on the outer shell of the combustion chamber barrel (1) along a direction parallel to the axis of the combustion chamber barrel (1); The slider (5) is mounted on the guide rail (3) and slides freely along the guide rail (3); The slide bar (7) is a folded-line rod, comprising a first folded portion and a second folded portion, the free end of the first folded portion is connected to a hinge seat (6) on the slide block (5) via a fixing pin, and the second folded portion is fixedly connected to the first folded portion, with a certain angle; the ceramic tube (8) is in the shape of a hollow cylinder, one end of the ceramic tube (8) is glued and fixed to the free end of the second folded portion of the slide bar (7), and the other end is suspended; when the plasma excitation device is working, it penetrates into the combustion chamber barrel (1), and when the excitation device is not working, it exits the combustion chamber barrel (1); The high-voltage electrode (9) is installed inside the ceramic tube (8). The diameter of the high-voltage electrode (9) is equal to or slightly smaller than the inner diameter of the ceramic tube (8), so that the high-voltage electrode (9) can be inserted into the ceramic tube (8). At one end of the ceramic tube (8) connected to the slide rod (7), the high-voltage electrode (9) is flush with the ceramic tube (8) and is connected to a high-voltage power source. At the suspended end of the ceramic tube (8), the length of the high-voltage electrode (9) exceeds the ceramic tube (8) and is exposed to the air. A displacement limiting hole is provided on the outer shell of the combustion chamber barrel (1) upstream of the guide rail (3) in the axial direction, and the fixed axis sleeve (4) is installed in the displacement limiting hole through a fixing pin and can rotate around the fixing pin; a through hole is provided on the fixed axis sleeve (4), the size of which is equal to or slightly larger than the outer diameter of the slide rod (7), and the second folded portion of the slide rod (7) can pass through the through hole on the fixed axis sleeve (4) and can slide in the through hole; The second folded portion of the slide rod (7) passes through the circular hole on the fixed axis sleeve (4), and the free end of the second folded portion is fixed to the ceramic tube (8). When the slide block (5) moves axially in the guide rail (3), the ceramic tube (8) and the high-voltage electrode (9) can be extended and retracted, so that they are away from or close to the flame stabilizer (2).

2. The plasma ignition and combustion-supporting device for a subcombustion ramjet combustion chamber with a retractable electrode as claimed in claim 1, characterized in that: The circumferential flame stabilizer (2) adopts an evaporation chamber flame stabilizer or an evaporation tube flame stabilizer commonly used in a sub-combustion ramjet combustion chamber, and is fixedly connected to the combustion chamber cylinder through a fixing device.

3. The plasma ignition and combustion-supporting device for a ramjet combustion chamber with a retractable electrode as claimed in claim 1, characterized in that: The turning angle between the second folding portion and the first folding portion is 150°.

4. The plasma ignition and combustion-supporting device for a ramjet combustion chamber with a retractable electrode as claimed in claim 1, characterized in that: The guide rail (3) is arranged on the outer shell of the combustion chamber barrel (1) or is directly arranged on the combustion chamber barrel (1), and the width and height of the slide block (5) are adapted to the width and height of the guide rail (3).

5. The plasma ignition and combustion-supporting device for a subcombustion ramjet combustion chamber with a retractable electrode as claimed in claim 1, characterized in that: The guide rail has a length of 100 mm, a width of 10 mm, and a height of 8 mm. The slider (5) has a length of 50 mm, and the slider (5) can slide on the guide rail (3).

6. The plasma ignition and combustion-supporting device for a subcombustion ramjet combustion chamber with a retractable electrode as claimed in claim 1, characterized in that: The combustion chamber cylinder (1) has a wall thickness of 9.4 mm, an inner diameter of 234 mm, and a length of 500 mm; The fixed axis sleeve (4) has a bottom diameter of 8 mm and a height of 8 mm, and a through hole with a diameter of 4 mm is provided on the side wall; The diameter of the hinge hole is 2mm; The sliding rod (7) and the ceramic tube (8) are connected by bonding with high temperature glue; The diameter of the high-voltage electrode (9) is 2 mm, and the high-voltage electrode (9) is exposed 1-2 mm from the end of the ceramic tube (8); The inner diameter of the ceramic tube (8) is 2 mm and the outer diameter is 4 mm. The high voltage electrode (9) is inserted into the ceramic tube (8) and fixed with high temperature glue.

7. A method for plasma ignition and combustion-supporting in a ramjet combustion chamber with a retractable electrode, which is based on the ramjet combustion chamber plasma ignition and combustion-supporting device with a retractable electrode as claimed in any one of claims 1 to 6, characterized in that: When the TBCC engine switches from a turbine mode to a ramjet mode, the slider (5) moves along the guide rail (3) toward the flame stabilizer (2), the slider (5) and the slide rod (7) are connected together through a hinge hole on a hinge seat (6), and when the slider (5) moves axially in the guide rail, the slide rod (7) is driven to rotate through the hinge seat (6); a ceramic tube (8) connected to the slide rod (7) extends from a through hole of a fixed axis sleeve (4) toward the flame stabilizer, and a high-voltage electrode (9) in the ceramic tube (8) extends into the flame stabilizer as an anode, and the wall of the flame stabilizer serves as a cathode. When the voltage is high enough, the air between the two electrodes is broken down to generate plasma.

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