CN109546533B

CN109546533B - Spark plug for internal combustion engine

Info

Publication number: CN109546533B
Application number: CN201811055193.5A
Authority: CN
Inventors: K·斯特尔威根; F·舍费尔
Original assignee: Caterpillar Energy Solutions GmbH
Current assignee: Caterpillar Energy Solutions GmbH
Priority date: 2017-09-22
Filing date: 2018-09-11
Publication date: 2022-01-25
Anticipated expiration: 2038-09-11
Also published as: CN109546533A; EP3460929A1; ES2821656T3; EP3460929B1

Abstract

A spark plug (30) for an internal combustion engine. The spark plug (30) is configured to be installed in a spark plug hole (44) of an engine such that the length of a heat transfer path from the center electrode (68) and the ground electrode (94) is shortened. To this end, a seal portion (58) through which heat transfer is effected is disposed closer to an end portion (51) of a housing (50) of the spark plug (30) than a mounting portion (56) for mounting the spark plug (30) in the spark plug hole (44). In this way, heat from the center electrode (68) and the ground electrode (94) can be transferred from the shell (50) to the inner surface of the spark plug hole (44) without flowing through the mounting portion (56).

Description

Spark plug for internal combustion engine

Technical Field

The present invention relates generally to internal combustion engines, and more particularly to spark plugs for internal combustion engines.

Background

Internal combustion engines (e.g., gaseous-fueled internal combustion engines driven by a mixture of gaseous fuel and air) may include a spark plug for each cylinder for ignition. In particular, large bore gaseous fuel internal combustion engines may benefit from a spark plug disposed in a pre-combustion chamber (also referred to as a pre-chamber) because otherwise it may be difficult to consistently achieve complete and thorough combustion of the gaseous fuel/air mixture.

Typically, such a prechamber is fluidly connected to the main combustion chamber of the respective cylinder via a lift pipe passage and a plurality of flow transfer passages. The flow transfer passage and the riser passage allow a mixture of gaseous fuel and air from the main combustion chamber to flow into the pre-chamber during a compression stroke. The enrichment of the mixture in the prechamber may be influenced by feeding a small amount of (gaseous) fuel to the prechamber via a separate fuel feed channel, for example during the intake stroke. The concentrated mixture is ignited by a spark plug in the prechamber. Ignition of the concentrated mixture causes a flame front of hot gases to propagate from the pre-chamber into the main combustion chamber via the flow transfer passage. Thus, the mixture in the main combustion chamber ignites and combusts, and thereby expands against the movable piston driving the crankshaft.

The present disclosure is directed, at least in part, to improving or overcoming one or more aspects of existing systems.

Disclosure of Invention

In one aspect, the present disclosure is directed to a spark plug for an internal combustion engine. The spark plug includes a center electrode extending in a longitudinal direction, a heat insulator disposed around the center electrode, and a housing mounted to the heat insulator. The housing is in thermal contact with the thermal shield at a first contact interface and has an opening at one end in the longitudinal direction through which the center electrode is exposed. The mounting portion is provided on an outer surface of the housing and is configured to removably mount the spark plug in a spark plug hole of the internal combustion engine. The sealing portion is disposed on an outer surface of the housing and is configured to sealingly engage an inner surface of the spark plug bore at the second contact interface when the spark plug is installed in the spark plug bore. The sealing portion is disposed between the mounting portion and the opening in the longitudinal direction.

According to another aspect, the present disclosure is directed to a prechamber assembly for an internal combustion engine. The prechamber assembly comprises a prechamber body defining a prechamber, and a spark plug according to the above aspect mounted in a spark plug bore formed in the prechamber such that a sealing portion of the spark plug sealingly engages an inner surface of the spark plug bore at the second contact interface.

Other features and aspects of the present invention will become apparent from the following description and the accompanying drawings.

Drawings

The accompanying drawings, which are incorporated herein and form a part of the specification, illustrate exemplary embodiments of the present invention and, together with the description, serve to explain the principles of the invention. In the drawings:

figure 1 shows a schematic cross-sectional view of a portion of an internal combustion engine fitted with a pre-combustion chamber assembly according to the present invention;

FIG. 2 shows a schematic cross-sectional view of a prechamber body comprising a spark plug according to the invention; and

fig. 3 shows a partial cross-sectional view of a spark plug according to the invention.

Detailed Description

The following is a detailed description of exemplary embodiments of the invention. The exemplary embodiments described herein and illustrated in the figures are intended to teach the principles of the present invention so that one of ordinary skill in the art can implement and use the invention in many different environments and for many different applications. Accordingly, the exemplary embodiments are not intended to, and should not be considered as, limiting the scope of the patent protection. Rather, the scope of patent protection is defined by the appended claims.

The present invention is based in part on the fact that: known spark plug designs have the disadvantage that heat flow from the electrodes of the spark plug occurs over long distances, and as a result, the electrodes can become extremely hot and experience considerable wear. This is particularly true when high pressure and rich combustion are used. Furthermore, even in the case of using materials like iridium, platinum and rhodium, the effect is only reduced and the problem cannot be overcome.

In view of the above, it has been recognized that there is a need for a new spark plug design that can significantly reduce the heat transfer distance from the electrode to the component of the engine in which the spark plug is installed. In this way, the temperature of the electrode can be significantly reduced and the oxidation of the material of the electrode can be reduced.

The present invention is also based in part on the fact that: providing additional thermal insulation of the spark plug from the combustion chamber further reduces the amount of heat transferred from the combustion chamber and also enhances heat transfer from the electrode. In particular, it has been recognized that materials having low thermal conductivity, such as inconel or ceramics, can be advantageously employed.

Referring now to the drawings, FIG. 1 shows a piston 2 disposed in a cylinder 4 that is part of an internal combustion engine 1 (not shown in further detail). The cylinder 4 is covered by a cylinder head 6. The piston 2, cylinder 4 and cylinder head 6 together define a main combustion chamber 8 of the internal combustion engine 1. The piston 2 is reciprocally disposed in the cylinder 4 so as to move between a Top Dead Center (TDC) and a Bottom Dead Center (BDC) during operation of the internal combustion engine 1.

For the purpose of describing an exemplary embodiment of the present invention, the internal combustion engine 1 is considered to be a four-stroke, stationary or marine internal combustion engine, such as a gaseous fuel engine or a dual-fuel engine, which is operated at least partially on gaseous fuel. However, those skilled in the art will appreciate that the internal combustion engine may be any type of engine (turbine, gas, diesel, natural gas, propane, two-stroke, etc.) that may utilize the pre-chamber assembly described herein or may not have a pre-chamber assembly. Further, the internal combustion engine may be of any size, have any number of cylinders, and be of any configuration (V-shaped, inline, radial, etc.). Further, the internal combustion engine may be used to power any machine or other device, including locomotive applications, on-highway trucks or vehicles, off-highway trucks or machines, earth moving equipment, generators, aerospace applications, marine applications, pumps, stationary equipment, or other engine-powered applications.

The cylinder head 6 comprises at least one inlet valve 10, for example a poppet valve. An inlet valve 10 is received in an inlet passage 12 opening in a piston side 14 of the cylinder head 6 for feeding a mixture of gaseous fuel and air into the main combustion chamber 8. Similarly, at least one outlet valve 16 (e.g., also a poppet valve) is received in an outlet passage 18 of the cylinder head 6 to direct exhaust gas away from the main combustion chamber 8.

Cylinder head 6 further includes prechamber assembly 20. A plurality of flow transfer passages 22 fluidly connect main combustion chamber 8 with the interior of prechamber assembly 20.

Prechamber assembly 20 is mounted in cylinder head 6 via a mounting body 24 as shown in fig. 1. Alternatively, prechamber assembly 20 may be mounted in cylinder head 6 in any other suitable manner.

Referring to FIG. 2, an exemplary embodiment of prechamber assembly 20 is shown in schematic cross-sectional view.

Prechamber assembly 20 comprises a first prechamber body 26, a second prechamber body 28, a spark plug 30, and a fuel supply 32. The first and

second prechamber bodies

26, 28 are connected to each other. A spark plug 30 and a fuel supply 32 are received in the second prechamber body 28.

The first prechamber body 26 comprises and defines a prechamber 34, a riser channel 38 and a flow transfer channel 22. In the assembled state, the flow transfer passage 22 fluidly connects the interior of the prechamber body 26 (prechamber 34 and riser passage 38) and the main combustion chamber 8 (fig. 1). It can be observed, for example, in fig. 2 that the diameter of the prechamber 34 is greater than the diameter of the riser channel 38, which in turn is greater than the diameter of the flow transfer channel 22.

The prechamber 34 extends along the longitudinal axis a of the first prechamber body 26, is funnel-shaped, and tapers towards the riser channel 38. Alternatively, the prechamber 34 may have any other shape, such as a cylindrical shape, a pyramidal shape, a conical shape, and combinations thereof. For example, the prechamber 34 may have a volume in the range between 0.1% and 10% of the compressed volume of the cylinder 4 (see fig. 1).

The bottom section of the prechamber 34 smoothly transitions into a riser channel 38. The riser channel 38 extends longitudinally in the first prechamber body 26 and opens with one end in the prechamber 34. In the configuration shown in FIG. 2, the riser passage 38 is aligned with the prechamber longitudinal axis A. Alternatively, the riser passage 38 may run parallel to the prechamber longitudinal axis a, or may define an angle with the prechamber longitudinal axis a. The riser passage 38 fluidly connects the prechamber 34 and the flow transfer passage 22.

To fluidly connect the bottom section of the riser channel 38 and the top section of the main combustion chamber 8 (see fig. 1), the flow transfer channel 22 is provided. The flow transfer passage 22 extends through a tip portion 43 of the first prechamber body 26. In some embodiments, the flow transfer passage 22 may open directly in the prechamber 34. In other words, the riser channel fluidly interconnected between the prechamber and the flow transfer channel may be omitted.

Spark plug 30 is mounted in prechamber assembly 20 such that spark plug 30 is operably coupled to prechamber 34.

As used herein, "operably coupled" means that the spark plug 30 is configured and arranged to ignite an ignitable mixture in the pre-chamber 34. For example, spark plug 30 may extend into pre-chamber 34. Specifically, the electrodes of the spark plug 30 may reach into the pre-chamber 34 such that a spark between the electrodes ignites the mixture in the pre-chamber 34. The spark plug 30 may be mounted in a spark plug hole 44 formed in the first and/or

second prechamber bodies

26, 28.

The fuel supply 32 is mounted in a fuel supply hole 46 extending through the second prechamber body 28. Alternatively, the fuel supply 32 may be mounted in the first prechamber body 26. The fuel supply device 32 is configured to supply fuel, such as gaseous fuel, or a rich mixture of fuel and air to the pre-chamber 34 for enrichment thereof.

As shown in fig. 2, the spark plug 30 includes a center electrode 68 that extends along the longitudinal direction L. A thermal shield 70 is disposed about and in thermal contact with the center electrode 68. Further, the case 50 is attached to the heat insulator 70. The housing 50 is a substantially cylindrical body that surrounds the thermal shield 70 and is in thermal contact with the thermal shield 70 at a first contact interface 80. As used herein, the term "contact interface" generally refers to an interface between two components that are in direct or indirect contact with each other, specifically in thermal contact with each other. Thus, as used herein, the term "contact interface" includes direct contact between surfaces of two members, or indirect contact between two members via an intermediate member. Specifically, as used herein, the term "contact interface" refers to an interface between two components through which heat transfer occurs. The first contact interface 80 will be described in more detail below.

The housing 50 of the spark plug 30 further has an opening 54 at the end 51 in the longitudinal direction a. The center electrode 68 is exposed through the opening 54. In the example shown in FIG. 2, the center electrode 68 protrudes from the opening 54 into the prechamber 34. However, in other embodiments, the center electrode 68 may not protrude from the opening 54 and may be disposed within a groove formed in the end 51 of the housing 50. Thus, as used herein, the term "exposed" is used to refer to accessibility of the center electrode 68 from the side of the prechamber 34 via the opening 54 formed in the housing 50.

As shown in FIG. 2, in one exemplary embodiment, the spark plug 30 further includes at least one ground electrode 94 mounted at the end 51 of the shell 50. Specifically, the ground electrode 94, which may be a J-gap electrode, is disposed facing the center electrode 68 such that a spark can be generated between the center electrode 68 and the ground electrode 94 in a known manner. For example, as will be described in greater detail below, the at least one ground electrode 94 is configured to be in thermal contact with the inner surface of the spark plug bore 44 via the shell 50 and the second contact interface 82, as will also be described in greater detail below.

A mounting portion 56 configured to removably mount the spark plug 30 in the spark plug hole 44 is provided on an outer surface of the housing 50. Specifically, as shown in fig. 2, the mounting portion 56 includes a shoulder 88 formed in an outer surface of the housing 50. The shoulder 88 is formed, for example, as a substantially annular flange on the housing 50.

Moreover, as shown in fig. 2, in the exemplary embodiment, mounting portion 56 further includes a mounting sleeve 90 that is configured to be mounted on an outer surface of housing 50 to engage shoulder 88 and bias housing 50 in longitudinal direction L toward end 51 of housing 50. Specifically, the mounting sleeve 90 includes a male threaded portion 92 configured to engage a corresponding female threaded portion formed in the inner surface of the spark plug bore 44. In this manner, the spark plug 30 is installed in the spark plug hole 44 by tightening the mounting sleeve 90 to press the housing 50 of the spark plug 30 against the

prechamber body

26, 28, as will be described in greater detail below.

The sealing portion 58 is disposed on an outer surface of the housing 50 and is configured to sealingly engage an inner surface of the spark plug bore 44 at the second contact interface 82 when the spark plug 30 is installed in the spark plug bore 44 in the manner described above.

With the above configuration, heat transferred to center electrode 68 and ground electrode 94 due to combustion in prechamber 34 is transferred to

prechamber bodies

26, 28 via first contact interface 80 and second contact interface 82. Specifically, heat is transferred from the ground electrode 94 to the shell 50, specifically the end 51 of the shell where the ground electrode 94 is attached to the shell 50, and from the end 51 of the shell 50 to the second prechamber body 28 via the second contact interface 82 where the shell 50 is pressed against the inner surface of the spark plug hole 44. Further, heat is transferred from the center electrode 68 to the second prechamber body 28 via the thermal shield 70, the first contact interface 80, and the second contact interface 82.

According to the invention, the sealing portion 58 of the spark plug 30 is arranged in the longitudinal direction L between the mounting portion 56 and the opening 54 at the end 51 of the housing 50. As shown in fig. 2, this has the effect that heat transfer from the housing 50 to the second prechamber body 28 takes place in close proximity to the end 51 where the center electrode 68 and the ground electrode 94 are heated due to combustion in the prechamber 34. This is in contrast to known designs in which the corresponding seal portions are disposed further from the end of the spark plug than the corresponding mounting portions, such that heat transfer occurs over a significant distance, i.e., resulting in significantly less efficient cooling of the exposed portions of the center and

ground electrodes

68, 94.

FIG. 3 illustrates in more detail an exemplary configuration of a spark plug 30 according to the present invention.

As shown in fig. 3, the sealing portion 58 includes a conical sealing surface 84 formed in the outer surface of the housing 50 and configured to sealingly engage a mating sealing surface of the spark plug bore 44 (see fig. 2). However, it should be clearly understood that the conical sealing surface 84 is merely exemplary of the sealing portion 58 for the present invention and that other suitable configurations can be used. For example, a shoulder or step could be formed in the outer surface of the housing 50 in addition to the conical sealing surface, so long as an extended sealing surface is provided that can press against a mating sealing surface of the spark plug hole when the spark plug 30 is installed in the spark plug hole 44. Further, in other embodiments, heat transfer between the housing 50 and the spark plug hole 44 may be effected by disposing an intermediate member, such as an annular seal, therebetween, mounted to an outer surface of the housing 50 and configured to sealingly engage an inner surface of the spark plug hole 44.

Further, while FIG. 3 illustrates an exemplary configuration in which the mounting portion 56 includes a shoulder 88 formed on the outer surface of the housing 50 and a mounting sleeve 90 as described above, it should be apparent that in other embodiments, the mounting portion may be configured as a male threaded portion formed on the housing 50 and engaging a female threaded portion formed in the inner surface of the spark plug to mount the spark plug inside the housing such that the sealing portion 58 sealingly engages the inner surface of the spark plug bore 44 at the second contact interface 82. Obviously, in any of the above-described configurations, the heat transfer path from both the center electrode 68 and the ground electrode 94 to the

prechamber body

26, 28 or any other component of the engine in which the spark plug 30 is mounted can be shortened because the seal portion 58 is disposed closer to the end portion 51 of the housing 50 than the mounting portion 56.

As shown in fig. 3, in the exemplary embodiment, first contact interface 80 is formed between a conical outer surface of insulation 70 and a corresponding conical inner surface of housing 50 with seal 87 disposed therebetween. When the spark plug 30 is assembled, heat transfer between the thermal insulator 70 and the housing 50 occurs primarily between the two conical surfaces mentioned above via the seal 87. Thus, heat transfer from the center electrode 68 to the housing 50 also occurs primarily via the first contact interface 80. The heat transferred from the center electrode 68 to the housing 50 via the first contact interface 80 is then transferred to the second prechamber body 28 via the second contact interface 82 (see fig. 2). The corresponding heat transfer path from the center electrode 68 is shown by the dashed lines in fig. 3.

Similarly, heat from ground electrode 94 is also transferred from housing 50 to second prechamber body 28 via second contact interface 82, specifically via conical sealing surface 84 in thermal contact with the mating surface of spark plug bore 44.

As shown in fig. 3, in one embodiment, the at least one ground electrode 94 may be configured as a plurality of linear electrodes 96 that protrude from the housing 50 relative to the longitudinal axis L at an angle of between 0 ° and 15 °, for example. Further, in some embodiments, a plurality of linear electrodes 96 (e.g., three such linear electrodes) may be disposed equidistantly in the circumferential direction. The heat transfer from the linear electrode 96 to the second contact interface 82 is also illustrated by the dashed lines in fig. 3.

It will be appreciated that the configuration of ground electrode 94 shown in the figures is merely exemplary, and any suitable configuration for these ground electrodes can be used. Further, in some embodiments, ground electrode 94 may be omitted. Specifically, in some cases, the housing 50 itself may serve as a "ground electrode" to create a spark to ignite the combustion products in the pre-chamber 34. Obviously, also in this case the above-mentioned advantageous effects of a short heat transfer path from the housing 50 to the second prechamber body 28 of the engine or corresponding component can be obtained.

Fig. 3 also shows that, in order to enhance the thermal insulation of the housing 50 from the combustion inside the prechamber 34, a shielding member 98 can be provided which at least partially covers the front surface 53 of the housing 50 at the end 51 thereof. Specifically, the shield member 98 may be formed as a cover that covers the front surface 53 of the housing 50 (e.g., a cap-like member attached to the end 51 of the housing 50) such that the plurality of linear electrodes 96 and the center electrode 68 protrude from the housing. Advantageously, the shield member 98 is made of a material having a lower thermal conductivity than the material forming the housing 50. For example, the shield member 98 may be made of a material such as inconel or ceramic to further reduce the amount of heat transferred from the sides of the prechamber 34 to the housing 50. This further increases the amount of heat that can be transferred from the center electrode 68 and the plurality of linear electrodes 96 to the housing 50 and

prechamber bodies

26, 28. On the other hand, the case 50 may be formed of a material having high thermal conductivity, such as an aluminum alloy and/or a copper alloy.

According to some exemplary embodiments, the second contact interface 82 is disposed closer to the opening 54 than the first contact interface 80, or at substantially the same location along the longitudinal direction L. In this way, heat transfer from the shell 50 to the component to which the spark plug 30 of the engine is mounted can occur as close as possible to the end 51 of the shell 50 to minimize the length of the heat transfer path from the center electrode 68 and the at least one ground electrode 94 to the component to which the spark plug 30 of the engine is mounted.

With the spark plug 30 according to the present invention, the distance to at least one of the center electrode 68 and the ground electrode 94 (if present) can be shortened to effectively cool the electrodes. Further, the mounting portion 56 of the housing 50 is isolated from the side of the prechamber 34 by a sealing portion 58 disposed therebetween. Specifically, in the case where the male threaded portion is formed on the outer surface of the housing 50 or the mounting sleeve 90, the male threaded portion is not subjected to heat generated due to combustion in the precombustion chamber 34. Further, the housing 50 itself can be thermally insulated from the prechamber 34 by providing a shield member 98 to further enhance heat transfer from the electrode.

Industrial applicability

The spark plug 30 disclosed herein by way of example is particularly applicable to gaseous fuel internal combustion engines that operate with a mixture of gaseous fuel and air. However, those of ordinary skill in the art will appreciate that the spark plug 30 described herein may be used with other engine configurations and types as well.

Generally, a gaseous-fueled internal combustion engine useful in the teachings of the present invention includes a plurality of cylinders and a plurality of pre-combustion chamber assemblies. Each prechamber assembly comprises a prechamber body defining a prechamber, a fuel supply arrangement received in the prechamber body and configured to supply gaseous fuel to the prechamber, and a spark plug according to the invention mounted in a spark plug bore formed in the prechamber body and configured to ignite the gaseous fuel in the prechamber. The plurality of pre-combustion chamber assemblies configured as described above are respectively mounted to cylinder heads of a plurality of cylinders of a gaseous fuel internal combustion engine.

It should be noted that while these embodiments have been described with reference to a spark plug disposed in a pre-chamber assembly, in other embodiments, a spark plug may be disposed in an engine that does not have a pre-chamber assembly. In other words, the spark plug disclosed herein may be mounted to a cylinder head of an internal combustion engine and may be disposed in a main combustion chamber of the engine. Further, while the present embodiments have been described with reference to the combustion of gaseous fuels, it should be appreciated that in some embodiments, different types of fuels can be used, such as liquid fuels and/or mixtures of gaseous and/or liquid fuels.

As used herein, terms such as "about," "approximately," or "substantially," when referring to measurable values such as parameters, amounts, durations, are meant to encompass variations of ± 10% or less, preferably ± 5% or less, more preferably ± 1% or less, and even more preferably ± 0.1% or less, relative to the stated value, provided such variations are suitable for implementation in the disclosed invention. It is to be understood that the value to which the modifier "about" refers is itself also specifically, and preferably, disclosed. The recitation of numerical ranges by endpoints includes all numbers and fractions subsumed within the respective range and the recited endpoint.

While preferred embodiments of the invention have been described herein, improvements and modifications may be incorporated without departing from the scope of the following claims.

Claims

1. A spark plug (30) for an internal combustion engine (1), the spark plug (30) comprising:

a central electrode (68) extending along a longitudinal direction (L);

a thermal shield (70) disposed about the center electrode (68);

a housing (50) mounted to the thermal shield (70), the housing (50) being in thermal contact with the thermal shield (70) at a first contact interface (80) and having an opening (54) at an end (51) along the longitudinal direction (L) through which the central electrode (68) is exposed;

a mounting portion (56) provided on an outer surface of the housing (50) and configured to removably mount the spark plug (30) in a spark plug hole (44) of the internal combustion engine (1); and

a sealing portion (58) disposed on the outer surface of the housing (50) and configured to sealingly engage an inner surface of the spark plug bore (44) at a second contact interface (82) when the spark plug (30) is installed in the spark plug bore (44),

wherein the sealing portion (58) is arranged between the mounting portion (56) and the opening (54) in the longitudinal direction (L);

the spark plug further comprises a shield member (98) at least partially covering a front surface (53) of the housing (50) at an end (51) thereof;

the shield member (98) is made of a material having a lower thermal conductivity than a material forming the housing (50).

2. The spark plug of claim 1, wherein the sealing portion (58) includes a conical sealing surface (84) configured to sealingly engage a mating sealing surface of the spark plug bore (44).

3. The spark plug of claim 1 or 2, wherein the sealing portion (58) includes an annular seal mounted to the outer surface of the housing (50) and configured to sealingly engage the inner surface of the spark plug bore (44).

4. The spark plug of claim 1 or 2, wherein the mounting portion (56) includes a shoulder (88) formed in the outer surface of the housing (50).

5. The spark plug of claim 4, wherein the shoulder (88) is formed as a substantially annular flange on the housing (50).

6. The spark plug of claim 4, further comprising a mounting sleeve (90) configured to be mounted on the outer surface of the housing (50) to engage the shoulder (88) and bias the housing (50) in the longitudinal direction (L) toward the end (51).

7. The spark plug of claim 6, wherein the mounting sleeve (90) includes a male threaded portion (92) configured to engage a female threaded portion formed on the inner surface of the spark plug bore (44) to mount the spark plug (30) in the spark plug bore (44).

8. The spark plug of claim 1 or 2, wherein the mounting portion (56) includes a male threaded portion formed on the housing (50) and configured to engage a female threaded portion formed in the inner surface of the spark plug bore (44) to mount the spark plug (30) inside the spark plug bore (44) such that the sealing portion (58) sealingly engages the inner surface of the spark plug bore (44) at the second contact interface (82).

9. The spark plug of any of claims 1, 2, 5-7, further comprising at least one ground electrode (94) mounted at an end (51) of the shell (50) and disposed facing the center electrode (68), the at least one ground electrode configured to be in thermal contact with the inner surface of the spark plug bore (44) via the shell (50) and the second contact interface (82).

10. The spark plug of claim 9, wherein the at least one ground electrode (94) includes a plurality of linear electrodes (96) protruding from the shell (50) at an angle between 0 ° and 15 ° relative to the longitudinal direction (L).

11. The spark plug of claim 10, wherein the plurality of linear electrodes (96) are disposed equidistantly in a circumferential direction.

12. The spark plug of any of claims 1, 2, 5-7, 10 and 11, wherein the shield member (98) is made of inconel and/or ceramic.

13. The spark plug of any of claims 1, 2, 5-7, 10 and 11, wherein the second contact interface (82) is disposed closer to the opening (54) than the first contact interface (80) or at substantially the same location along the longitudinal direction (L) as the first contact interface (80).

14. The spark plug of claim 11, wherein the plurality of linear electrodes (96) is three linear electrodes.

15. A prechamber assembly (20) for an internal combustion engine (1), comprising:

a prechamber body (26, 28) defining a prechamber (34); and

the spark plug (30) of any of claims 1-14, installed in a spark plug hole (44) formed in the pre-chamber body (26, 28) such that the sealing portion (58) of the spark plug (30) sealingly engages the inner surface of the spark plug hole (44) at the second contact interface (82).