A glow discharge tube having a set of electrodes within a gas seal envelope

Abstract

A glow discharge tube includes a gas-sealed envelope, a first electrode, and a second electrode. The gas-sealed envelope defines an interior having an interior surface that defines a first interior portion having a first interior surface and a second interior portion having a second interior surface. The first electrode is located within the first interior portion, and the second electrode is located within and in contact with the second interior portion.

Description

TECHNICAL FIELD

[0001] The present disclosure relates generally to a glow discharge tube, and more particularly to a glow discharge tube having a set of electrodes. BACKGROUND

[0002] A spark gap is a passive two-terminal switch that opens when the voltage across the terminals is low, and then closes when the voltage across the terminals exceeds a design value (e.g., 1-3 kV). The spark gap then reopens when the current drops to a low level or when most of the energy from the voltage source is dissipated. Internally, the current is carried between two metal electrodes separated by a small gap (~mm) filled with a gas or gas mixture near atmospheric pressure. The gas is normally insulating, but when the voltage between the two electrodes exceeds a design value corresponding to the breakdown voltage, it becomes a conductive plasma spark.

[0003] For various applications, one parameter of interest can be the time between when sufficient voltage is applied to the spark gap and when it becomes conductive. This time corresponds to the breakdown process that initiates the transition of the gas from an insulator to a conductor.

[0004] The electrical breakdown can be seen as a two-step process - a statistical time for the first electron to appear, followed by a formation time for an electron avalanche to a highly conductive state. A free electron appears in the gap at some time and location, and is accelerated by the electric field produced by the potential difference between the electrodes. Once the electron gains sufficient energy, it has a certain probability of ionizing a gas atom or molecule and releasing a second free electron. Each electron is then accelerated and the process repeats, resulting in an electron avalanche that makes the gas highly conductive. The energy gain and multiplication process must overcome various energy and particle loss processes, and for maximum efficiency, the first free electron should be produced at a preferred location (e.g., at or near the negative electrode).

[0005] The time required for the second (avalanche) process is the formation time lag. It is usually very short and practically negligible. Thus, the time required for the first process (the initial electron) is the statistical time lag, and it is this first electron problem that is of most interest in practice. In some devices, such as laboratory equipment or large discharge lamps, the first electron problem is solved by waiting for a cosmic ray to produce a free electron upon collision with a gas atom, gas molecule, or surface within the device. Electron-ion pairs are always produced in the atmosphere at a given rate by high-energy cosmic rays, which can easily penetrate the gas volumes within devices and structures. However, one cannot rely on the ubiquitous cosmic ray process to produce an effective free electron within the time frame required, which can be necessary for reliable operation of many devices that incorporate a spark gap. In particular, for devices that employ a spark gap, the time frame is usually too short to rely on a cosmic ray-based process because the interaction volume (the region of gas between the electrodes) is relatively small.

[0006] Conversely, the conventional approach to solving the first electron problem in a spark gap environment (and in other devices that deal with similar problems, such as small discharge lamps) is to add a radioactive source, for example in the form of radioactive krypton-85, which undergoes beta decay to emit high-energy electrons, to seed electrons, and to reduce the statistical time lag to an acceptable value. Other radioactive materials, such as tritium or thorium, are sometimes used. The addition of a radioactive component is sometimes referred to as radioactive excitation. However, radioactive materials, even at trace levels, are often undesirable in components or products because these materials increase the cost of manufacture, handling, and transportation. SUMMARY

[0007] TECHNICAL SOLUTION 1. A glow discharge tube comprising:

[0008] a gas-tight envelope defining an interior having an inner surface, the inner surface defining a first interior portion having a first inner surface and a second interior portion having a second inner surface;

[0009] a first electrode having a first portion with a first outer surface located within the first interior portion; and

[0010] a second electrode having a second portion with a second outer surface located within the second interior portion, and at least a portion of the second outer surface is in contact with the second inner surface.

[0011] TECHNICAL SOLUTION 2. The glow discharge tube of any preceding technical solution, wherein the first portion terminates in a first end and the second portion terminates in a second end facing and spaced apart from the first end.

[0012] TECHNICAL SOLUTION 3. The glow discharge tube of any preceding technical solution, wherein at least one of the first end or the second end comprises a non-planar topography feature.

[0013] TECHNICAL SOLUTION 4. The glow discharge tube of any preceding technical solution, wherein the second surface comprises the non-planar topography feature.

[0014] TECHNICAL SOLUTION 5. The glow discharge tube of any preceding technical solution, wherein the first electrode is an anode and the second electrode is a cathode.

[0015] TECHNICAL SOLUTION 6. The glow discharge tube of any preceding technical solution, wherein the non-planar topography feature is at least one of a castellation topography feature, a wave topography feature, a peak and valley topography feature, or a knurl topography feature.

[0016] TECHNICAL SOLUTION 7. The glow discharge tube of any preceding technical solution, wherein the non-planar topography feature is a knurl topography feature.

[0017] TECHNICAL SOLUTION 8. The glow discharge tube of any preceding technical solution, wherein the non-planar topography feature is a peak and valley topography feature.

[0018] TECHNICAL SOLUTION 9. The glow discharge tube of any preceding technical solution, wherein the first interior portion is defined by a first cross-sectional area perpendicular to the first inner surface, and the second interior portion is defined by a second cross-sectional area perpendicular to the second inner surface, wherein the first cross-sectional area is greater than the second cross-sectional area.

[0019] TECHNICAL SOLUTION 10. The glow discharge tube of any preceding technical solution, wherein the first outer surface is spaced apart from the first inner surface to define a gap between the first electrode and the gas-tight enclosure.

[0020] TECHNICAL SOLUTION 11. The glow discharge tube of any preceding technical solution, wherein the gap is 0.1 mm.

[0021] TECHNICAL SOLUTION 12. The glow discharge tube of any preceding technical solution, wherein the first electrode and the second electrode are spaced apart from each other by a distance between 3 mm and 6 mm.

[0022] TECHNICAL SOLUTION 13. The glow discharge tube of any preceding technical solution, wherein the first electrode comprises a first set of wires and the second electrode comprises a second set of wires facing the first set of wires, and wherein the first set of wires defines the first outer surface and the second set of wires defines the second outer surface.

[0023] Technical Solution 14. The glow discharge tube of any preceding technical solution, wherein the first electrode is an anode and the second electrode is a cathode.

[0024] Technical Solution 15. The glow discharge tube of any preceding technical solution, wherein at least one of the first electrode or the second electrode is operably coupled to a power source that supplies an electric current to at least one of the first electrode or the second electrode to generate an electric field between the first electrode and the second electrode.

[0025] Technical Solution 16. The glow discharge tube of any preceding technical solution, wherein the electric field is between 10 and 20 volts / micron.

[0026] Technical Solution 17. The glow discharge tube of any preceding technical solution, wherein the gas-sealed envelope comprises dielectric glass.

[0027] Technical Solution 18. An ignition device comprising:

[0028] a spark gap device comprising:

[0029] a first spark gap electrode;

[0030] a second spark gap electrode spaced apart from and opposing the first spark gap electrode; and

[0031] a glow discharge tube comprising:

[0032] a gas-sealed envelope defining an interior having an inner surface, the inner surface defining a first interior portion having a first inner surface and a second interior portion having a second inner surface;

[0033] a first electrode having a first portion having a first outer surface located within the first interior portion; and

[0034] a second electrode having a second portion having a second outer surface located within the second interior portion, and at least a portion of the second outer surface is in contact with the second inner surface.

[0035] Technical Solution 19. The ignition device of any preceding technical solution, wherein the first electrode is an anode and the second electrode is a cathode, and at least a portion of the second electrode comprises a non-planar topography.

[0036] Technical Solution 20. The ignition device of any preceding technical solution, wherein the non-planar topography is at least one of a castellation topography, a wave topography, a peak and valley topography, or a knurl topography. BRIEF DESCRIPTION OF DRAWINGS

[0037] The complete and enabling disclosure of the present description, including the best mode thereof, to one of ordinary skill in the art, is set forth in the specification, which is to be read in conjunction with the drawings, wherein:

[0038] Figure 1 is a schematic perspective view of a turbine engine including an ignition device having a spark gap device and a light source.

[0039] Figure 2 is Figure 1 is a cross-sectional perspective view of a glow discharge tube of

[0040] Figure 3 is Figure 2 is a cross-sectional perspective view of an example glow discharge tube of

[0041] Figure 4 is Figure 2 is a cross-sectional perspective view of another example glow discharge tube of

[0042] Figure 5 is Figure 2 is a cross-sectional perspective view of an example glow discharge tube of

[0043] Figure 6 is Figure 2 is a cross-sectional perspective view of an example glow discharge tube of

[0044] Figure 7 is Figure 3 is a cross-sectional perspective view of another example glow discharge tube of DETAILED DESCRIPTION

[0045] Aspects of the disclosure described herein broadly relate to ignition devices for combustion engines. As non-limiting examples, aspects of the disclosure described herein relate to ignition devices for turbine engines including combustion sections. The ignition devices can include a spark gap device in combination with a light source having a glow discharge tube. The spark gap device can be a radiation-free spark gap device. The glow discharge tube can include a sealed tube having a first electrode and a second electrode disposed within an interior of the sealed tube. A gas seal enclosure can at least partially enclose the first electrode and the second electrode.

[0046] A glow discharge tube can be used to generate light or photon emission through an electron breakdown event as described herein, thereby defining a light source. The photon emission can impinge on at least one electrode within a spark gap device, which in turn can cause electron emission within the spark gap device. A glow discharge tube as described herein can be used to generate sufficient photon emission even in dark conditions. As used herein, the term "dark conditions" or iterations thereof can refer to an environment that would result in photon emission from the glow discharge tube having a wavelength insufficient to generate electron emission from an electrode in a spark gap device.

[0047] For purposes of illustration, an exemplary environment within which an ignition device can be utilized will be described in the form of a turbine engine. In non-limiting examples, such a turbine engine can be in the form of a gas turbine engine, a turboprop engine, a turboshaft engine, or a turbofan engine having a power gear box. However, it will be understood that the disclosed aspects described herein are not so limited and can have universal applicability in any suitable combustion engine including an ignition device. For example, the present disclosure can have applicability to ignition devices in other engines or vehicles and can be used to provide benefits in industrial, commercial, and residential applications.

[0048] As used herein, the term "upstream" refers to a direction opposite to a direction of fluid flow, and the term "downstream" refers to a direction the same as the direction of fluid flow. The term "forward" or "forwardly" means in front of something, and "rearward" or "rearwardly" means behind something. For example, when used in terms of fluid flow, forward / forwardly can mean upstream, and rearward / rearwardly can mean downstream.

[0049] Additionally, as used herein, the term "radial" or "radially" refers to a direction away from a common center. For example, in the overall context of a turbine engine, radial refers to a direction along a ray extending between a central longitudinal axis of the engine and an outer circumference of the engine. Further, as used herein, the term "set" or "a set" of elements can be any number of elements, including only one.

[0050] All directional references (e.g., radial, axial, proximal, distal, upper, lower, upward, downward, left, right, lateral, front, back, top, bottom, above, below, vertical, horizontal, clockwise, counterclockwise, upstream, downstream, forward, aft, etc.) are only used for identification purposes to aid the reader’s understanding of the present disclosure, and do not create limitations, particularly as to the position, orientation, or use of the aspects of the present disclosure described herein. Connection references (e.g., attached, coupled, connected, joined, fixed, secured, and the like) are to be construed broadly and can include intermediate members between the elements being connected and relative movement between elements unless otherwise indicated. As such, connection references do not necessarily infer that two elements are directly connected and in fixed relation to one another. The exemplary drawings are for purposes of illustration only and the dimensions, positions, order and relative sizes reflected in the attached drawings attached hereto can vary.

[0051] Figure 1 is a schematic view of a turbine engine 10. As a non-limiting example, the turbine engine 10 can be used within an aircraft. The turbine engine 10 can include at least a compressor section 12, a combustion section 14, and a turbine section 16. A drive shaft 18 rotationally couples the compressor section 12 and the turbine section 16 such that rotation of one section affects rotation of the other section and defines an axis of rotation 20 for the turbine engine 10.

[0052] The compressor section 12 can include a low pressure (LP) compressor 22 and a high pressure (HP) compressor 24 fluidly coupled to one another in series. The turbine section 16 can include a LP turbine 26 and a HP turbine 28 fluidly coupled to one another in series. The drive shaft 18 can operatively couple the LP compressor 22, the HP compressor 24, the LP turbine 26, and the HP turbine 28 together. Alternatively, the drive shaft 18 can include a LP drive shaft (not shown) and a HP drive shaft (not shown). The LP drive shaft can couple the LP compressor 22 to the LP turbine 26, and the HP drive shaft can couple the HP compressor 24 to the HP turbine 28. A LP rotating shaft can be defined as a combination of the LP compressor 22, the LP turbine 26, and the LP drive shaft such that rotation of the LP turbine 26 can impart a driving force to the LP drive shaft, which in turn can rotate the LP compressor 22. A HP rotating shaft can be defined as a combination of the HP compressor 24, the HP turbine 28, and the HP drive shaft such that rotation of the HP turbine 28 can impart a driving force to the HP drive shaft, which in turn can rotate the HP compressor 24.

[0053] The compressor section 12 can include a plurality of axially spaced stages. Each stage includes a set of circumferentially spaced rotating blades and a set of circumferentially spaced stationary vanes. The compressor blades for a stage of the compressor section 12 can be mounted to a disk that is mounted to the drive shaft 18. Each set of blades for a given stage can have its own disk. The vanes of the compressor section 12 can be mounted to a casing that can extend circumferentially around the turbine engine 10. It will be appreciated that the representation of the compressor section 12 is merely illustrative and that there can be any number of stages. Further, it is contemplated that there can be any other number of components within the compressor section 12.

[0054] Similar to the compressor section 12, the turbine section 16 can include a plurality of axially spaced stages, with each stage having a set of circumferentially spaced rotating blades and a set of circumferentially spaced stationary vanes. The turbine blades for a stage of the turbine section 16 can be mounted to a disk that is mounted to the drive shaft 18. Each set of blades for a given stage can have its own disk. The vanes of the turbine section can be mounted to a casing in a circumferential manner. It should be noted that there can be any number of blades, vanes, and turbine stages as the illustrated turbine section is merely a representative illustration. Further, it is contemplated that there can be any other number of components within the turbine section 16.

[0055] The combustion section 14 can be disposed in series between the compressor section 12 and the turbine section 16. The combustion section 14 can be fluidly coupled to at least a portion of the compressor section 12 and the turbine section 16 such that the combustion section 14 at least partially fluidly couples the compressor section 12 to the turbine section 16. As a non-limiting example, the combustion section 14 can be fluidly coupled to the HP compressor 24 at an upstream end of the combustion section 14 and fluidly coupled to the HP turbine 28 at a downstream end of the combustion section 14.

[0056] The turbine engine 10 can also include, or otherwise be operably coupled to, a fuel ignition system 30. As a non-limiting example, the combustion section 14 can include, or otherwise be operably coupled to, the ignition system 30. The ignition system 30 can include a set of igniters 32, an exciter 36, and a set of leads 34 that operably connect the set of igniters 32 to the exciter 36. As a non-limiting example, at least a portion of the igniters 32 can extend into, or otherwise be directly coupled to, the combustion section 14. An ignition device 100 can be disposed within the exciter 36. As illustrated, the ignition device 100 can include a spark gap device 102 and a light source including a glow discharge tube 104. Although a single ignition device 100 is illustrated, it will be appreciated that the exciter 36 can include any number of one or more ignition devices 100.

[0057] During operation of the turbine engine 10, ambient or atmospheric air is drawn into the compressor section 12 via a fan (not shown) upstream of the compressor section 12, where it is compressed, defining pressurized air. The pressurized air may then flow into the combustion section 14, where it is mixed with fuel and ignited by an ignition system 30 (e.g., a set of igniters 32), thereby generating combustion gases. Some work is extracted from these combustion gases by an HP turbine 28 driving the HP compressor 24. The combustion gases are exhausted to a LP turbine 26, which extracts additional work to drive the LP compressor 22, and the exhaust gases are ultimately exhausted from the turbine engine 10 via an exhaust section (not shown) downstream of the turbine section 16. The drive of the LP turbine 26 drives the LP rotor shaft, which rotates the fan (not shown) and the LP compressor 22. Together, the pressurized air flow and the combustion gases may define the working air flow through the fan, compressor section 12, combustion section 14, and turbine section 16 of the turbine engine 10.

[0058] Ignition within the combustion section 14 may occur by generating a spark within the ignition device 100. As a non-limiting example, the spark may be generated within the spark gap device 102. The spark, in turn, may cause electron emission from a corresponding set of igniters 32. The electron emission from the set of igniters 32 may ignite the fuel-air mixture within the combustion section 14 and cause ignition and combustion, thereby generating combustion gases.

[0059] Figure 2 yes Figure 1 FIG2 is a cross-sectional perspective view of a glow discharge tube 104. The glow discharge tube 104 may include a gas-tight enclosure 124 defining an interior 126. A set of opposing electrodes may be disposed within the interior 126. As a non-limiting example, the set of opposing electrodes may include a first electrode 110 and a second electrode 112 disposed within the interior 126.

[0060] The first electrode 110 and the second electrode 112 can be defined by their relative charges relative to each other. As a non-limiting example, the first electrode 110 can be positively charged, thereby defining an anode, and the second electrode 112 can be negatively charged, thereby defining a cathode. Alternatively, the first electrode 110 and the second electrode 112 can be cathode / anode rather than anode / cathode.

[0061] The first electrode 110 and the second electrode 112 of the glow discharge tube 104 can be any suitable electrode such as, but not limited to, a wire electrode, a point electrode, or any combination thereof. The first electrode 110 and the second electrode 112 can be made of any suitable material for an electrode such as, but not limited to, nickel. The first electrode 110 and the second electrode 112 can also comprise a generally cylindrical form. Alternatively, the first electrode 110 and the second electrode 112 can comprise any suitable shape such as, but not limited to, a spherical shape, a rectangular shape, a triangular shape, or any combination thereof. As illustrated, the first electrode 110 and the second electrode 112 can each comprise a hollow interior. It is contemplated that the hollow interior can assist during the breakdown process and the generation of an electric field within the glow discharge tube 104. Further, the hollow interior can result in an electrode that requires less material than an electrode without a hollow interior.

[0062] The first electrode 110 can comprise a first distal end 114, while the second electrode can comprise a second distal end 116 opposite the first distal end 114. The first electrode 110 can extend between the first distal end 114 and a third distal end 115. The second electrode 112 can extend between the second distal end 116 and a fourth distal end 117. The first distal end 114 and the second distal end 116 can be spaced apart from one another and define a distance 118 therebetween. As a non-limiting example, the distance 118 can be between 3 mm and 6 mm. It is contemplated that the distance 118 can be adjusted based on a nominal operating voltage of the glow discharge tube 104. As illustrated, both the first distal end 114 and the second distal end 116 can be defined by the same planar or otherwise flat topography. However, both the first distal end 114 and the second distal end 116 can have the same or different topography, which can be planar or non-planar.

[0063] The first electrode 110 can also have a first outer portion defined by a first outer surface 120. The first outer surface 120 can interconnect the first distal end 114 and the third distal end 115. The second electrode can also have a second outer surface defined by a second outer surface 122. The second outer surface 122 can interconnect the second distal end 116 and the fourth distal end 117.

[0064] As discussed herein, the first electrode 110 and the second electrode 112 can have a generally cylindrical form such that the first outer surface 120 and the second outer surface 122 can define an outer circumference of a cylinder. The first electrode 110 and the second electrode 112 can be sized and shaped such that the first electrode 110 is a mirror image of the second electrode 112. As a non-limiting example, the first electrode 110 can have the same cross-sectional area or diameter as the second electrode 112. Alternatively, the first electrode 110 can be larger or smaller than the second electrode 112, or shaped differently than the second electrode 112.

[0065] The glow discharge tube 104 can also include a gas seal enclosure 124 that includes an interior 126 and at least partially encloses the first electrode 110 and the second electrode 112. Although illustrated as open (e.g., hollow interior), it will be appreciated that the first electrode 110 and the second electrode 112 can be sealed along the third distal end 115 or the fourth distal end 117, respectively. As such, the interior 126 of the gas seal enclosure 124 is completely sealed. It is contemplated that at least one of the first electrode 110 and the second electrode 112 has at least one of the third distal end 115 or the fourth distal end 117 extending through the gas seal enclosure 124. It is contemplated that the gas seal enclosure 124 can completely enclose the first electrode 110 and the second electrode 112 such that they are sealed within the interior 126. As a non-limiting example, the first electrode 110 can be at least partially disposed within or enclosed by a first interior portion of the gas seal enclosure 124, while the second electrode 112 can be at least partially disposed within or enclosed by a second interior portion of the gas seal enclosure 124.

[0066] As illustrated, the gas seal enclosure 124 can be formed to correspond to the first electrode 110 and the second electrode 112. In other words, the gas seal enclosure can be formed in a generally cylindrical form having a hollow interior. The gas seal enclosure 124 can also be defined by a first interior portion defined by a first interior surface 128 and a second interior portion defined by a second interior surface 130, each defining an outer circumference of the gas seal enclosure 124 or an inner circumference of the interior 126. As a non-limiting example, the first interior surface 128 can face the first exterior surface 120, while the second interior surface 130 faces the second exterior surface 122.

[0067] The first interior portion can define a first cross-sectional area 132, while the second interior portion can define a second cross-sectional area 134. The first electrode 110 can be at least partially received within the first interior portion, while the second electrode 112 can be at least partially located within the second interior portion. As illustrated, the first cross-sectional area 132 can be greater than the second cross-sectional area 134 such that a shelf 136 is formed between the junction between the first interior portion and the second interior portion. As illustrated, the shelf 136 can extend perpendicular to the first interior surface 128 and the second interior surface 130 to create a sharp change in cross-sectional area between the first cross-sectional area 132 and the second cross-sectional area 134. However, it will be appreciated that the region can include any suitable transition between the first interior portion and the second interior portion. As a non-limiting example, the first cross-sectional area 132 can decrease non-sharply, forming a linear or non-linear transition between the first cross-sectional area 132 and the second cross-sectional area 134.

[0068] The gas-sealed enclosure 124 can also be made of a dielectric material, such as but not limited to glass, ceramic (e.g., silicon dioxide, quartz, aluminum oxide, etc.), or any combination thereof. As such, the gas-sealed enclosure 124 can also be defined as a dielectric gas-sealed enclosure 124. As a non-limiting example, the gas-sealed enclosure can have a thickness of 0.9 mm and include a magnetic permeability of 3-9.

[0069] The first cross-sectional area 132 can be dimensioned such that it is greater than a diameter of the first electrode 110. As such, a gap 138 can be formed between the first outer surface 120 and the first inner surface 128. As a non-limiting example, the gap 138 can be 1 mm. The gap 138 can be constant around an entire perimeter of the first electrode 110. Alternatively, the gap 138 can be non-constant around the entire perimeter of the first electrode 110. The second cross-sectional area 134 can be dimensioned such that it is equal to a cross-sectional area of the second electrode 112. As such, the gas-sealed enclosure 124 can be dimensioned such that the second inner surface 130 contacts the second outer surface 122.

[0070] The interior 126 of the gas-sealed enclosure 124 can include a gas. As a non-limiting example, the gas can be a non-radioactive gas or otherwise include an inert gas, such as but not limited to nitrogen, argon, helium, neon, krypton, or any combination thereof. As a non-limiting example, a gas pressure within the gas-sealed enclosure 124 can be between 75 Torr and 150 Torr. As a non-limiting example, the gas-sealed enclosure 124 can define a vacuum.

[0071] During operation of the glow discharge tube 104, a voltage (e.g., a direct current (DC) voltage) can be applied from a power source to at least one of the first electrode 110 or the second electrode 112. The voltage can cause an electric field to be generated between the first electrode 110 and the second electrode 112 and cause field emission or electron emission to occur within the glow discharge tube 104. As a non-limiting example, the field emission can occur from the second distal end 116 of the second electrode 112. With the electric field generated, a breakdown event can occur within the glow discharge tube 104. As used herein, the term “breakdown event” can refer to a time or, in addition, a process that it takes for electrons to be emitted from at least one of the electrodes, as well as a time or process for the emitted electrons to avalanche into a high conductive state.

[0072] Because the gas seal envelope 124 includes a dielectric material, contact between the gas seal envelope 124 and the second electrode 112 can contribute to the generation of an electric field within the glow discharge tube 104. As a non-limiting example, contact between the gas seal envelope 124 and the second electrode 112 can generate a triple point emission. As used herein, the term "triple point emission" or iterations thereof can refer to a process in which electrons are emitted (e.g., field emission) from a surface that is in contact at a point or boundary from a conductor (e.g., the second distal end 116 of the second electrode 112), an insulator (e.g., the dielectric material of the gas seal envelope 124), and a gas or vacuum (e.g., the gas or vacuum within the interior 126), and the local electric field can be very high compared to a glow discharge tube that includes an electrode that does not contact a dielectric surface. In other words, field emission can occur at the intersection of these three media (hence the triple point). The difference in surface potential between the adjacent conductive and insulating regions results in the formation of a very high electric field at the boundary between the two regions. The electric field then pulls electrons out of the conductive material through field emission. As a non-limiting example, the very high electric field can be between 10 and 20 volts / micron.

[0073] The gap 138 can serve to prevent, limit, or otherwise constrain the possible conduction of surface electrons along the dielectric material (e.g., the gas seal envelope 124). This, in turn, can force a breakdown event to occur between the first electrode 110 and the second electrode through triple point emission. It is contemplated that the electric field generated within the glow discharge tube 104 can be between 1 and 3 volts / micron. As a non-limiting example, the electric field can vary based on the composition of the gas within the interior 126 of the gas seal envelope 124.

[0074] Figure 3 is Figure 2 A cross-sectional perspective view of an exemplary glow discharge tube 204. The glow discharge tube 204 is similar to the glow discharge tube 104, and thus, like parts will be identified with like numbers increased by 200, it being understood that the description of like parts of the glow discharge tube 104 apply to the glow discharge tube 204 unless otherwise noted. It will be appreciated that the glow discharge tube 204 can be suitable for use within the ignition device 100.

[0075] The glow discharge tube 204 is similar to the glow discharge tube 104 in that it includes a gas sealed envelope 224 that defines a second interior 226, a first electrode 210, and a second electrode 212, where both the first electrode 210 and the second electrode 212 are disposed within the second interior 226. The gas sealed envelope 224 can be similar to the gas sealed envelope 124 in that it includes a first interior portion defined by a first inner surface 228 and defining a first cross-sectional area 232, a second interior portion defined by a second inner surface 230 and defining a second cross-sectional area 234, and a shelf 236 defining a transition region between the first cross-sectional area 232 and the second cross-sectional area 234. The first electrode 210 can be at least partially disposed within or enclosed by the first interior portion of the gas sealed envelope 224. The second electrode 212 can be at least partially disposed within or enclosed by the second interior portion of the gas sealed envelope 224. The first cross-sectional area 232 can be sized such that a gap 238 is formed between the first inner surface 228 and the first outer surface 220, while the second cross-sectional area 234 can be sized such that the second inner surface 230 contacts the second electrode 212. The first electrode 210 can be similar to the first electrode 110 in that it can include a first distal end 214 and a third distal end 215 interconnected by the first outer surface 220. The second electrode 212 can be similar to the second electrode 112 in that it includes a second distal end 216 opposite the first distal end 214 and a fourth distal end 217 interconnected by the second outer surface 222. The first electrode 210 and the second electrode 212 can be spaced apart from one another such that the first distal end 214 and the second distal end 216 can be spaced apart from one another by a distance 218.

[0076] The glow discharge tube 204 differs from the glow discharge tube 104 in that the first distal end 214 of the first electrode 210 and the second distal end 216 of the second electrode 212 do not include the same topographical features. Similar to the first distal end 114, the first distal end 214 can include a planar or otherwise flat topographical feature. However, the second distal end 216 can be defined by a non-planar topographical feature. As a non-limiting example, the non-planar topographical feature can be a knurled or diamond-shaped topographical feature.

[0077] It will be appreciated that the non-planar topography features can be formed as part of the first electrode 210 or the second electrode 212 by any suitable method. As non-limiting examples, the non-planar topography features can be formed by machining of the first distal end 214 or the second distal end 216 after the first electrode 210 or the second electrode 212, respectively, has been manufactured. As non-limiting examples, the non-planar topography features can be formed during manufacture of the first electrode 210 or the second electrode 212 such that no additional machining is required (e.g., the first electrode 210 or the second electrode 212 can be cast, additively manufactured, etc. with the non-planar topography features). Alternatively, the non-planar topography features can be separate pieces that are coupled to the remaining portion of the first electrode 210 or the second electrode 212. The non-planar topography features can be coupled to the remaining portion of the first electrode 210 or the second electrode 212 by any suitable coupling method, such as but not limited to welding, adhering, magnetic force, fastening, or any combination thereof.

[0078] The non-planar topography features can be used to create a larger local electric field at the tips or points of the knurl topography features. This, in turn, can result in field emission from the tips or points of the knurl topography features. As non-limiting examples, the knurl topography features can be used to generate a triple point emission from the second distal end 216 of the second electrode 212. The local electric field can be very high when compared to an electrode with planar topography features, and even higher when compared to a glow discharge tube without an electrode contact dielectric material and with an electrode having planar topography features.

[0079] Figure 4 is Figure 2 A cross-sectional perspective view of an exemplary glow discharge tube 304. The glow discharge tube 304 is similar to the glow discharge tubes 104, 204, and thus, like parts will be identified with like numbers increased by 300 series, it being understood that the description of like parts of the glow discharge tubes 104, 204 apply to the glow discharge tube 304 unless otherwise noted. It will be appreciated that the glow discharge tube 304 can be suitable for use within the ignition device 100.

[0080] The glow discharge tube 304 is similar to the glow discharge tubes 104, 204 in that it includes a gas sealed envelope 324 that defines a second interior 326, a first electrode 310, and a second electrode 312, where both the first electrode 310 and the second electrode 312 are disposed within the second interior 326. The gas sealed envelope 324 can be similar to the gas sealed envelopes 124, 224 in that it includes a first interior portion defined by a first inner surface 328 and defining a first cross-sectional area 332, a second interior portion defined by a second inner surface 330 and defining a second cross-sectional area 334, and a shelf 336 defining a transition region between the first cross-sectional area 332 and the second cross-sectional area 334. The first electrode 310 can be at least partially disposed within or enclosed by the first interior portion of the gas sealed envelope 324. The second electrode 312 can be at least partially disposed within or enclosed by the second interior portion of the gas sealed envelope 324. The first cross-sectional area 332 can be sized such that a gap 338 is formed between the first inner surface 328 and the first outer surface 320, while the second cross-sectional area 334 can be sized such that the second inner surface 330 contacts the second electrode 312. The first electrode 310 can be similar to the first electrodes 110, 210 in that it can include a first distal end 314 and a third distal end 315 interconnected by the first outer surface 320. The second electrode 312 can be similar to the second electrodes 112, 212 in that it includes a second distal end 316 opposite the first distal end 314 and a fourth distal end 317 interconnected by the second outer surface 322. The first electrode 310 and the second electrode 312 can be spaced apart from one another such that the first distal end 314 and the second distal end 316 can be spaced apart from one another by a distance 318.

[0081] The glow discharge tube 304 differs from the glow discharge tube 104 in that the first distal end 314 of the first electrode 310 and the second distal end 316 of the second electrode 312 do not include the same topographical features similar to the glow discharge tube 204. Similar to the first distal end 114, 214, the first distal end 314 can include a planar or otherwise flat topographical feature. Similar to the second distal end 216, the second distal end 316 can be defined by a non-planar topographical feature that is functionally similar to the non-planar topographical feature of the second distal end 216 in that it facilitates the generation of field emission through the use of triple point emission. However, the non-planar topographical feature of the second distal end 316 can differ from the non-planar topographical feature of the second distal end 216. As a non-limiting example, the non-planar topographical feature can be a peak and valley topographical feature. However, it will be appreciated that the non-planar topographical feature can take any suitable non-planar topographical feature, such as but not limited to a battlemented topographical feature, a wave topographical feature, or any combination thereof.

[0082] Figure 5 is Figure 2FIG. 4 is a cross-sectional perspective view of an exemplary glow discharge tube 404. The glow discharge tube 404 is similar to the glow discharge tubes 104, 204, 304, and thus, like parts will be identified with like numerals increased by 400 series, it being understood that the description of like parts of the glow discharge tubes 104, 204, 304 applies to the glow discharge tube 404 unless otherwise noted. It will be appreciated that the glow discharge tube 404 can be suitable for use within the ignition device 100.

[0083] The glow discharge tube 404 is similar to the glow discharge tubes 104, 204, 304 in that it includes a gas sealed envelope 424 that defines a second interior 426, a first electrode 410, and a second electrode 412. The gas sealed envelope 424 can be similar to the gas sealed envelopes 124, 224, 324 in that it includes a first interior portion defined by a first interior surface 428 and defining a first cross-sectional area 432 and a second interior portion defined by a second interior surface 430 and defining a second cross-sectional area 434. The first electrode 410 can be at least partially disposed within or enclosed by the first interior portion of the gas sealed envelope 424. The second electrode 412 can be at least partially disposed within or enclosed by the second interior portion of the gas sealed envelope 424. The second cross-sectional area 434 can be sized such that the second interior surface 430 contacts the second electrode 412. The first electrode 410 can be similar to the first electrodes 110, 210, 310 in that it can include a first distal end 414 and a third distal end 415 interconnected by a first outer surface 420. The second electrode 412 can be similar to the second electrodes 112, 212, 312 in that it includes a second distal end 416 opposite the first distal end 414 and a fourth distal end 417 interconnected by a second outer surface 422. The first electrode 410 and the second electrode 412 can be spaced apart from one another such that the first distal end 414 and the second distal end 416 can be spaced apart from one another by a distance 418.

[0084] The glow discharge tube 404 is similar to the glow discharge tube 104 in that the first electrode 410 and the second electrode 412 include planar topographies along the first distal end 414 and the second distal end 416, respectively. However, the gas sealed envelope 424 is different from the gas sealed envelopes 124, 224, 324 due to the first cross-sectional area 432 being equal to the second cross-sectional area 434. In other words, the cross-sectional area of the gas sealed envelope 424 is constant along the entire gas sealed envelope 424. As illustrated, the second electrode 412 can have a smaller diameter than the first electrode 410. As such, a gap 438 can be formed between the first interior portion or first interior surface 428 and the first electrode 410. In other words, the diameter of the first electrode 410 can be smaller than the diameter of the second electrode 412 and the first cross-sectional area 432.

[0085] Figure 6 is Figure 2FIG. 5 is a cross-sectional perspective view of an exemplary glow discharge tube 504. The glow discharge tube 504 is similar to the glow discharge tubes 104, 204, 304, 404, and thus, like parts will be identified with like numerals increased by 500 series, it being understood that the description of like parts of the glow discharge tubes 104, 204, 304, 404 apply to the glow discharge tube 504 unless otherwise noted. It will be appreciated that the glow discharge tube 504 can be suitable for use within the ignition device 100.

[0086] The glow discharge tube 504 is similar to the glow discharge tubes 104, 204, 304, 404 in that it includes a gas sealed enclosure 524 that defines a second interior 526, a first electrode 510, and a second electrode 512. The gas sealed enclosure 524 can be similar to the gas sealed enclosures 124, 224, 324 in that it includes a first interior portion defined by a first interior surface 528 and defining a first cross-sectional area 532, a second interior portion defined by a second interior surface 530 and defining a second cross-sectional area 534. As illustrated, the gas sealed enclosure 524 can be similar to the gas sealed enclosure 424 in that the first cross-sectional area 532 can be equal to the second cross-sectional area 534. However, it will be appreciated that the gas sealed enclosure 524 can be formed similar to the gas sealed enclosures 124, 224, 324 such that the first cross-sectional area 532 is not equal to the second cross-sectional area 534. The first electrode 510 can be at least partially disposed within or enclosed by the first interior portion of the gas sealed enclosure 524. The second electrode 512 can be at least partially disposed within or enclosed by the second interior portion of the gas sealed enclosure 524. The second cross-sectional area 534 can be sized such that the second interior surface 530 contacts at least a portion of the second electrode 512. The first electrode 510 can be similar to the first electrodes 110, 210, 310, 410 in that it can include a first distal end 514 and a third distal end 515 interconnected by a first exterior surface 520. The second electrode 512 can be similar to the second electrodes 112, 212, 312, 412 in that it includes a second distal end 516 opposite the first distal end 514 and a fourth distal end 517 interconnected by a second exterior surface 522. The first electrode 510 and the second electrode 512 can be spaced apart from one another such that the first distal end 514 and the second distal end 516 can be spaced apart from one another by a distance 518.

[0087] The first electrode 510 can include a first body 552, while the second electrode 512 can include a second body 554. The first body 552 and the second body 554 can be disposed at opposite distal ends of the gas-sealed enclosure 524. However, the first electrode 510 and the second electrode 512 are each different from the first electrode 110, 210, 310, 410 and the second electrode 112, 212, 312, 412 in that the first electrode 510 includes a first set of wires 556 and the second electrode 512 includes a second set of wires 558. As such, the first electrode 510 and the second electrode 512 can each be defined as a wire electrode.

[0088] The first set of wires 556 can extend from the first body 552 of the first electrode 510 and toward at least a portion of the second electrode 512. The second set of wires 558 can extend from the second body 554 of the second electrode 512 and toward at least a portion of the first electrode 510. Distal ends of the first set of wires 556 and the second set of wires 558 can define the first distal end 514 and the second distal end 516, respectively. Portions of the first set of wires 556 that oppose the first inner surface 528 of the gas-sealed enclosure 524 can at least partially define the first outer surface 520. While portions of the second set of wires 558 that oppose the second inner surface 530 of the gas-sealed enclosure 524 can at least partially define the second outer surface 522.

[0089] It will be appreciated that the first set of wires 556 and the second set of wires 558 can further define tapered portions of the first electrode 510 and the second electrode 512, respectively. As a non-limiting example, at least one of the first set of wires 556 can taper (e.g., angle) relative to the first body 552, or the second set of wires 558 can taper (e.g., angle) relative to the second body 554. As illustrated, the first set of wires 556 and the second set of wires 558 each include two wires disposed at opposite ends of the first body 552 and the second body 554, respectively. However, it will be appreciated that there can be any number of one or more first wires 556 or second wires 558 that extend across at least a portion of the first body 552 or the second body 554, respectively. As a non-limiting example, the first set of wires 556 can include a single first wire 556 that extends in a continuous manner across an entire circumference of the first body 552. In other words, the first wire 556 can form a frustoconical portion of the first electrode 510 that extends from the first body 552 and faces the second electrode 512.

[0090] Similar to the first electrode 110, 210, 310, 410, the first body 552 and the first set of wires 556 are not in contact with the first inner surface 528. As such, a gap 538 can be formed between the first distal end 514 or any other portion of the first outer surface 520 defined by the first set of wires 556 and the first inner surface 528. Similar to the second electrode 112, 212, 312, 412, at least a portion of the first electrode 510 can be in contact with the gas-sealed enclosure 524. As a non-limiting example, the second distal end 516 or any other portion of the second inner surface 530 defined by the second set of wires 558 can be in contact with the second inner surface 530 of the gas-sealed enclosure 524.

[0091] Figure 7 is Figure 1 a more detailed illustration of the ignition device 100. As illustrated, the ignition device 100 can include the spark gap device 102 and the glow discharge tube 104 spaced apart from one another. Although described from the perspective of the ignition device 100 disposed within the ignition system 30 of the turbine engine 10 Figure 1 ) it will be appreciated that the ignition device 100 can be used within any suitable ignition system 30 of any suitable combustion engine. It will be further appreciated that although described from the perspective of the glow discharge tube 104, the glow discharge tube 104 can be any glow discharge tube 104, 204, 304, 404, 504 as described herein.

[0092] The spark gap device 102 can include a sealed environment 140 defining an interior 142. The sealed environment 140 can include any suitable material such as, but not limited to, at least semi-transparent glass. As a non-limiting example, the sealed environment 140 can include any light-transmissive material. The interior 142 of the sealed environment 140 can be filled with any suitable non-radioactive gas similar to the interior 126. As a non-limiting example, the interior 142 can include an inert gas such as, but not limited to, nitrogen, argon, helium, neon, or any combination thereof. A set of opposing spark gap electrodes can be disposed within the interior 142 and spaced apart from one another. As a non-limiting example, the set of opposing spark gap electrodes includes a first spark gap electrode 144 and a second spark gap electrode 146. As illustrated, the first spark gap electrode 144 and the second spark gap electrode 146 can include distal ends that oppose and are spaced apart from one another to define a gap therebetween. The first spark gap electrode 144 and the second spark gap electrode 146 can also be defined by their relative charges with respect to one another. As a non-limiting example, the first spark gap electrode 144 can be positively charged, thereby defining a cathode, while the second spark gap electrode 146 can be negatively charged, thereby defining an anode.

[0093] As illustrated, the glow discharge tube 104 is disposed outside of the spark gap device 102. However, it will be appreciated that at least a portion of the glow discharge tube 104 can be disposed within the interior 142 of the sealed environment 140.

[0094] The ignition device 100 can also include or otherwise be operably coupled to a power source 148. The power source 148 can be any suitable power source capable of supplying a direct current (DC) voltage to at least one of the electrodes 110, 112, 144, 146 of the ignition device 100. The power source 148 can be operably coupled to the first spark gap electrode 144 such that the power source 148 can supply a DC voltage to the first spark gap electrode 144. As a result, an electrical current (e.g., approximately 1 milliampere) can be generated within the interior 142 of the spark gap device 102. At least one of the first electrode 110 and the second electrode 112 of the glow discharge tube 104 can be coupled to the first spark gap electrode 144, the second spark gap electrode 146, or both. As illustrated, the power source 148 of the glow discharge tube 104 can be the same as the power source 148 of the spark gap device 102.

[0095] During operation, a DC voltage is supplied from the power source 148 to at least one of the first electrode 110 and the second electrode 112. As a non-limiting example, the DC voltage can be supplied to the second electrode 112, thereby defining a cathode. The DC voltage can cause an electric field to be generated between the first electrode 110 and the second electrode 112 and cause a field emission to occur within the glow discharge tube 104. As discussed herein, the field emission can generate a breakdown event and a subsequent electron avalanche, which can ultimately generate a photon emission 150 (e.g., a light emission) that will be emitted from the glow discharge tube 104. With the photon emission 150, the glow discharge tube 104 can be defined as a light source for the ignition device 100. The amount of the DC voltage can be used to adjust the wavelength, frequency, and / or amount of energy of the light emitted by the glow discharge tube 104. As a non-limiting example, the photon emission 150 can be defined by a wavelength between 100 nanometers (nm) and 1000 nm, between 200 nm and 800 nm, or between 300 nm and 500 nm. It is contemplated that the wavelength of the glow discharge tube 104 (e.g., the wavelength of the photon emission 150) can be adjusted by the gas composition within the glow discharge tube 104, and the intensity of the photon emission 150 can be adjusted by the power source 148 increasing or decreasing the amount of the DC voltage supplied to the first electrode 110 and the second electrode 112.

[0096] Because the sealed environment 140 includes a light-transmissive material (e.g., glass), the photon emission 150 can pass through the sealed environment 140 and impinge or otherwise be incident on at least one surface of the first spark gap electrode 144, the second spark gap electrode 146, or both the first spark gap electrode 144 and the second spark gap electrode 146. In either case, when the photon emission 150 impinges on the first spark gap electrode 144 and / or the second spark gap electrode 146, the first spark gap electrode 144 and the second spark gap electrode 146 can absorb at least a portion of the photon emission 150. This, in turn, causes the electrodes to emit electrons that have absorbed the photons. It is contemplated that the energy of the photon emission 150 must exceed the work-function of the material of the first spark gap electrode 144 and the second spark gap electrode 146 in order for electron emission to occur. The energy ε of a photon is related to its wavelength λ by the expression ε = hc / λ, where h is Planck's constant and c is the speed of light. In practical units, ε = 1240 / λ, where ε is in electron volts and λ is in nanometers. With this in mind, the wavelength of the photon emission 150 will depend on the work-function of the material. As a non-limiting example, if the work-function of the material is 2-6 electron volts, the wavelength of the photon emission 150 will need to be in the range of 200-600 nm. It will also be appreciated that the material of the sealed environment 140 can affect the wavelength of the photon emission 150. As a non-limiting example, borosilicate glass strongly absorbs at wavelengths less than 300 nanometers, which corresponds to an energy of 4 electron volts. Thus, as an example, if a given material has a work-function of 3 electron volts, and the glow discharge tube 104 is placed outside of the sealed environment 140 to produce the photon emission 150, only photons with an energy of 3-4 electron volts (300-400 nanometers) will be effective. Photon emissions 150 that include wavelengths longer than 400 nanometers will not have enough energy to cause photon emission, and photons with wavelengths less than 300 nanometers will be absorbed by the glass. Thus, the material of the first spark gap electrode 144 and the second spark gap electrode 146, the wavelength of the photon emission 150, and the transmission properties of the sealed environment 140 are all factors to be considered in the design and construction of a spark gap system or as discussed herein. As discussed herein, at least a portion of the glow discharge tube 104 can be disposed within the sealed environment 140.

[0097] With the above in mind, the glow discharge tube 104 can be positioned relative to the first spark gap electrode 144 and the second spark gap electrode 146 such that the photon emission 150 is incident on a surface of at least one of the first spark gap electrode 144 or the second spark gap electrode 146. This, in turn, causes the first spark gap electrode 144 or the second spark gap electrode 146 to emit electrons via the photoelectric effect. These electrons can then be used to simulate a gas discharge or breakdown event. These electrons can then be used to initiate a gas discharge or breakdown event. The breakdown event can ultimately produce an electron avalanche, which can in turn cause the spark gap device 102 to fire or otherwise generate a spark, which can ultimately be used to ignite a fuel-air mixture within the combustion section 14 by a set of igniters 32 as discussed herein. Figure 1

[0098] It is contemplated that the electrodes (e.g., the first spark gap electrode 144 and the second spark gap electrode 146) from which the photon emission 150 from the glow discharge tube 104 is incident and emits electrons can be, but are not limited to, conventional electrodes (e.g., conventional electrically conductive metal bases and surfaces), electrodes having a coated surface or other emissive coating (e.g., a special purpose emissive coating), or photoelectrodes (e.g., a photocathode or other ring electrode or coil having a coating or composition specifically for emitting electrons in response to light photons).

[0099] It is further contemplated that the power source 148 can be configured to apply sufficient voltage to the glow discharge tube 104 prior to supplying sufficient voltage to the spark gap device 102. This can allow time to start the glow discharge tube 104 and generate the photon emission 150. As a non-limiting example, the power source 148 can provide voltage to the glow discharge tube 104 between 100 milliseconds (ms) and 200 ms prior to a desired time for the spark gap device 102 to fire.

[0100] ​Benefits of the present disclosure include a glow discharge tube that is capable of consistently operating over a wide range of conditions, including dark conditions, when compared to conventional glow discharge tubes. For example, conventional glow discharge tubes rely on a pair of spaced apart electrodes received within a sealed tube. In this case, the electrodes both include flat surfaces and are not in contact with any dielectric material. As such, when a conventional glow discharge tube is in dark conditions, the ability to produce electron breakdown and photon emission is greatly inhibited. Conventional glow discharge tubes can rely on intervention from additional components (e.g., a high voltage trigger transformer external to the conventional glow discharge tube) in order to produce the required field emission, which can ultimately produce photon emission from the conventional glow discharge tube. In conventional glow discharge tubes, electron breakdown and photon emission can occur over time as free electrons will eventually be generated within the glow discharge tube. However, this process can take time, and therefore, if response time is critical (e.g., photon emission is needed within a small amount of time after DC current is supplied to the glow discharge tube), conventional glow discharge tubes can not meet the time requirements. However, a glow discharge tube as described herein includes components that can enhance the generation of electric fields that ultimately lead to field emission, breakdown events, electron avalanches, and ultimately photon emission. As a non-limiting example, a gas seal envelope can help enhance the generation of electric fields. As the gas seal envelope includes a dielectric material, and the cathode is in contact with the dielectric material, the gas seal envelope can help the generation of electric fields within the glow discharge tube. As another non-limiting example, the non-planar topography of at least the cathode can enhance the generation of electric fields. As discussed herein, the non-planar topography can generate large local electric fields, which can be used to generate electric fields between the electrodes. With the gas seal envelope made of a dielectric material, the contact between the cathode and the dielectric material, and the non-planar topography, a triple point emission can occur. The triple point emission, in turn, can generate very high electric fields (e.g., 10-20 V / micron) when compared to the electric fields in conventional glow discharge tubes. The very high electric fields can ultimately induce field emission within the glow discharge tube without the need for intervention from additional components. As such, electric fields can be generated over a wider range of operating conditions, including dark conditions as discussed herein. Moreover, it is contemplated that the high electric fields can lead to the generation of the first free electron, and subsequent electron avalanches and photon emission occur more quickly when compared to conventional glow discharge tubes. Thus, a glow discharge tube as described herein allows for relatively easy generation of photon emission over a wide range of operating conditions within a required time frame when compared to conventional glow discharge tubes.

[0101] Additional benefits of the present disclosure when compared to conventional ignition devices include an ignition device that is free of any radioactive gases. For example, conventional ignition devices rely on radioactive gases (e.g., krypton-85) within their respective sealed environments in order to generate field emission and sparking. However, the ignition devices as described herein allow for the elimination of these radioactive substances from the gas mixtures that are typically present within spark gap devices and glow discharge tubes, while still maintaining the same performance and functionality of the ignition device. The present approach utilizes the photoelectric effect to generate seed electrons at a specific emission flux level using a light source (e.g., a glow discharge tube) having a specific rated wavelength (or range of wavelengths). The light source is positioned relative to a surface of at least one of the electrodes within the spark gap device, and the emitted photons that are incident on the surface of the electrode(s) cause at least one of them to emit an electron that is required to initiate a gas discharge or breakdown event. The present approach can be retrofitted in existing packaging, such that there would be no significant changes in the manufacture of the spark gap device, glow discharge tube, or the rest of the ignition system.

[0102] To the extent not already described, the different features and structures of the various aspects can be used in combination with each other, as desired. One feature cannot be illustrated in all aspects, but is not intended to be excluded from the claims, and is described for illustrative purposes only. Thus, features of the different aspects can be mixed and matched as desired in order to form new aspects, whether or not the new aspects have been described or are even implied. Combinations of features of the aspects described herein are within the scope of the disclosure.

[0103] This written description uses examples to describe aspects of the disclosure described herein, including the best mode, and also to enable any person skilled in the art to practice aspects of the disclosure, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the aspects of the disclosure is defined by the claims, and can include other examples that occur to those skilled in the art. Such other examples are intended to fall within the scope of the claims if they have structural elements in common with the words recited in the claims or if they include equivalent structural elements with insubstantial differences from the recited claims.

[0104] Further aspects of the disclosure are provided by the subject matter of the following clauses:

[0105] A glow discharge tube comprising: a gas sealed envelope defining an interior, the interior having an inner surface defining a first interior portion having a first inner surface and a second interior portion having a second inner surface; a first electrode having a first portion having a first outer surface located within the first interior portion; and a second electrode having a second portion having a second outer surface located within the second interior portion, and at least a portion of the second outer surface is in contact with the second inner surface.

[0106] The glow discharge tube of any of the preceding clauses, wherein the first portion terminates in a first end and the second portion terminates in a second end facing and spaced apart from the first end.

[0107] The glow discharge tube of any of the preceding clauses, wherein at least one of the first end or the second end comprises a non-planar topography feature.

[0108] The glow discharge tube of any of the preceding clauses, wherein the second surface comprises the non-planar topography feature.

[0109] The glow discharge tube of any of the preceding clauses, wherein the first electrode is an anode and the second electrode is a cathode.

[0110] The glow discharge tube of any of the preceding clauses, wherein the non-planar topography feature is at least one of a castellation topography feature, a wave topography feature, a peak and valley topography feature, or a knurl topography feature.

[0111] The glow discharge tube of any of the preceding clauses, wherein the non-planar topography feature is a knurl topography feature.

[0112] The glow discharge tube of any of the preceding clauses, wherein the non-planar topography feature is a peak and valley topography feature.

[0113] The glow discharge tube of any of the preceding clauses, wherein the first interior portion is defined by a first cross-sectional area perpendicular to the first inner surface and the second interior portion is defined by a second cross-sectional area perpendicular to the second inner surface, wherein the first cross-sectional area is greater than the second cross-sectional area.

[0114] The glow discharge tube of any of the preceding clauses, wherein the first outer surface is spaced apart from the first inner surface to define a gap between the first electrode and the gas-tight enclosure.

[0115] The glow discharge tube of any of the preceding clauses, wherein the gap is 0.1 mm.

[0116] The glow discharge tube of any of the preceding clauses, wherein the first electrode and the second electrode are spaced apart from each other by a distance between 3 mm and 6 mm.

[0117] The glow discharge tube of any of the preceding clauses, wherein the first electrode comprises a first set of wires and the second electrode comprises a second set of wires facing the first set of wires, and wherein the first set of wires defines the first outer surface and the second set of wires defines the second outer surface.

[0118] The glow discharge tube of any of the preceding clauses, wherein the first electrode is an anode and the second electrode is a cathode.

[0119] The glow discharge tube of any of the preceding clauses, wherein at least one of the first electrode or the second electrode is operably coupled to a power source that supplies an electric current to at least one of the first electrode or the second electrode to generate an electric field between the first electrode and the second electrode.

[0120] The glow discharge tube of any of the preceding clauses, wherein the electric field is between 10 and 20 volts / micron.

[0121] The glow discharge tube of any of the preceding clauses, wherein the gas- sealed envelope comprises dielectric glass.

[0122] An ignition device comprising: a spark gap device comprising a first spark gap electrode, a second spark gap electrode spaced apart and opposite the first spark gap electrode; and a glow discharge tube comprising: a gas-sealed envelope defining an interior, the interior having an inner surface defining a first interior portion having a first inner surface and a second interior portion having a second inner surface; a first electrode having a first portion having a first outer surface located within the first interior portion; and a second electrode having a second portion having a second outer surface located within the second interior portion, and at least a portion of the second outer surface is in contact with the second inner surface.

[0123] The ignition device of any of the preceding clauses, wherein the first electrode is an anode and the second electrode is a cathode, and at least a portion of the second electrode comprises a non-planar topography feature.

[0124] The ignition device of any of the preceding clauses, wherein the non-planar topography feature is at least one of a castellation topography feature, a wave topography feature, a peak and valley topography feature, or a knurl topography feature.

Claims

1. A glow discharge tube comprising: a gas containment enclosure defining an interior having an interior surface, the interior surface defining a first interior portion having a first interior surface and a second interior portion having a second interior surface; a first electrode having a first portion with a first outer surface positioned within the first interior portion; and A second electrode has a second portion having a second outer surface located within the second inner portion, and at least a portion of the second outer surface is in contact with the second inner surface.

2. The glow discharge tube according to claim 1, wherein The first portion terminates in a first end, and the second portion terminates in a second end facing the first end and spaced apart from the first end.

3. The glow discharge tube according to claim 2, wherein: At least one of the first end or the second end includes a non-planar topography.

4. The glow discharge tube according to claim 3, wherein The second outer surface includes the non-planar topography.

5. The glow discharge tube according to claim 4, wherein The first electrode is an anode, and the second electrode is a cathode.

6. The glow discharge tube according to claim 3, wherein The non-planar topographical feature is at least one of a crenellated topographical feature, a wavy topographical feature, a peak and valley topographical feature, or a knurled topographical feature.

7. The glow discharge tube according to claim 6, wherein The non-planar topographical feature is a knurled topographical feature.

8. The glow discharge tube according to claim 6, wherein The non-planar topographic features are peak and valley topographic features.

9. The glow discharge tube according to claim 2, wherein The first interior portion is defined by a first cross-sectional area perpendicular to the first interior surface, and the second interior portion is defined by a second cross-sectional area perpendicular to the second interior surface, wherein the first cross-sectional area is larger than the second cross-sectional area.

10. The glow discharge tube according to claim 1, wherein The first outer surface is spaced apart from the first inner surface to define a gap between the first electrode and the gas sealing enclosure.

11. The glow discharge tube according to claim 10, wherein The gap is 0.1 mm.

12. The glow discharge tube according to any one of claims 1 to 11, wherein: The first electrode and the second electrode are spaced apart from each other by a distance between 3 mm and 6 mm.

13. The glow discharge tube according to any one of claims 1 to 11, wherein: The first electrode comprises a first set of wires and the second electrode comprises a second set of wires facing the first set of wires, and wherein the first set of wires defines the first outer surface and the second set of wires defines the second outer surface.

14. The glow discharge tube according to any one of claims 1 to 11, wherein: The first electrode is an anode, and the second electrode is a cathode.

15. The glow discharge tube according to any one of claims 1 to 11, wherein: At least one of the first electrode or the second electrode is operably coupled to a power source that supplies current to at least one of the first electrode or the second electrode to generate an electric field between the first electrode and the second electrode.

16. The glow discharge tube according to claim 15, wherein The electric field may be between 10 and 20 volts per micron.

17. The glow discharge tube according to any one of claims 1 to 11, wherein: The gas-tight enclosure comprises dielectric glass.

18. An ignition device comprising: A spark gap device comprising: a first spark gap electrode; a second spark gap electrode spaced apart from and opposed to the first spark gap electrode; and A glow discharge tube comprising: a gas containment enclosure defining an interior having an interior surface, the interior surface defining a first interior portion having a first interior surface and a second interior portion having a second interior surface; a first electrode having a first portion with a first outer surface located within the first interior portion; and A second electrode has a second portion having a second outer surface located within the second inner portion, and at least a portion of the second outer surface is in contact with the second inner surface.

19. The ignition device according to claim 18, wherein: The first electrode is an anode and the second electrode is a cathode, and at least a portion of the second electrode includes a non-planar topography.

20. The ignition device according to claim 19, wherein: The non-planar topographical feature is at least one of a crenellated topographical feature, a wavy topographical feature, a peak and valley topographical feature, or a knurled topographical feature.

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