INTERNAL COMBUSTION ENGINE

Abstract

A piston arrangement (12) for an internal combustion engine (10) comprises one or more pistons (14) which are at least partly constructed from a technical ceramic material. An axially disposed bore (20) for receiving a heat transfer member (22) is provided in at least one of the pistons (14). The heat transfer member (22) is reconfigurable from a first, solid, state to a second state in which at least part of the heat transfer member (22) is in a liquid state so as to transfer heat away from and thus cool the piston rod (16) as the piston reciprocates. A cylinder arrangement (46) for the internal combustion engine (10) comprises one or more cylinders (48) which are at least partly constructed from a technical ceramic material. One or more grooves (54) are formed in the cylinder (48), to decrease the thermal gradient between the inside and outside of the cylinder (48). A piston (14) for the internal combustion engine (10) comprises a piston rod (16) and a piston crown (18) which is at least partly constructed from a technical ceramic material. An insulation arrangement (40) between the piston rod (16) and the piston crown (18) comprises segments (42) configured such that when disposed on the piston rod (16) axial slots or spaces are defined between the segments (42).

Claims

1. A piston arrangement for an internal combustion engine, the piston arrangement comprising: a plurality of pistons, wherein the pistons are arranged in an opposed configuration, and wherein one or more of said pistons is at least partially constructed from a technical ceramic material.

2. The piston arrangement of claim 1, wherein the one or more pistons are wholly or substantially wholly constructed from the technical ceramic material.

3. The piston arrangement of claim 1, wherein the one or more pistons are partially constructed from the technical ceramic material.

4. The piston arrangement of claim 1, wherein the technical ceramic material comprise or takes the form of Silicon Nitride.

5. The piston arrangement of claim 1, wherein at least one of the pistons is at least partially constructed from a metallic material.

6. The piston arrangement of claim 1, wherein the one or more pistons each comprise a piston rod.

7. The piston arrangement of claim 6, wherein the piston rod of at least one of the pistons comprises an axially disposed bore formed therein and a heat transfer member is configured for location in the bore of the piston rod, wherein the heat transfer member is reconfigurable from a first, solid, state to a second state in which at least part of the heat transfer member is in a liquid state, the heat transfer member in said second state being movable relative to the bore of the piston rod so as to transfer heat away from and thus cool the piston rod as the piston reciprocates.

8. The piston arrangement of claim 7, wherein the heat transfer member is formed from a metallic material, e.g. sodium.

9. (canceled)

10. The piston arrangement of claim 6, wherein the piston rod comprises: a pushrod portion; and a wedge portion, wherein the wedge portion of the piston rod comprises a plurality of segments.

11. The piston arrangement of claim 6, wherein at least one of the pistons comprises an insulation arrangement interposed between the piston rod and a piston crown of the respective piston, wherein the insulation arrangement comprises a plurality of segments, and wherein the insulation arrangement is configured and/or arranged such that when disposed on the piston rod axial slots or spaces are defined between the segments of the insulation arrangement, and wherein optionally the insulation arrangement is constructed from a technical ceramic material.

12.-14. (canceled)

15. The piston arrangement of claim 1, wherein one or more of the pistons comprises a fluid communication arrangement, wherein the fluid communication arrangement comprises one or more axial bores and one or more radial bores, the radial bores communicating with the one or more axial bores.

16. A piston and cylinder assembly for an internal combustion engine, the piston and cylinder assembly comprising: the piston arrangement of claim 1; and a cylinder arrangement comprising cylinders for receiving the pistons of the piston arrangement.

17. (canceled)

18. The piston and cylinder assembly of claim 17, wherein one or more of the cylinders is wholly or substantially wholly constructed from the technical ceramic material.

19. The piston and cylinder assembly of claim 17, wherein one or more of the cylinders is partially constructed from the technical ceramic material.

20. The piston and cylinder assembly of claim 17, wherein the technical ceramic material comprises or takes the form of Silicon Nitride.

21. The piston and cylinder assembly of claim 16, wherein one or more grooves are formed or otherwise provided in the outer surface of at least one of the cylinders.

22. The piston and cylinder assembly of claim 21, wherein at least one of the grooves comprises or takes the form of a micro-groove, e.g. having a width in the range 1 micron to 100 mm.

23. (canceled)

24. The piston and cylinder assembly of claim 16, comprising a gas scavenging arrangement operatively associated with the cylinder arrangement.

25. An internal combustion engine comprising the piston arrangement of claim 1 and/or (ii) the piston arrangement and a cylinder arrangement comprising cylinders for receiving the pistons of the piston arrangement.

26. The internal combustion engine of claim 25, comprising an exhaust reservoir housing, the exhaust reservoir housing defining an exhaust reservoir, wherein one or more grooves are formed or otherwise provided in the inner surface of the exhaust reservoir housing.

27. The internal combustion engine of claim 25, comprising a cooling arrangement for a fuel injection arrangement of the internal combustion engine, wherein the cooling arrangement comprises one or more heat pipes.

28. The internal combustion engine of claim 27, wherein at least one of: the one or more heat pipes are coupled to or operatively associated with a heat sink; at least one off the one or more heat pipes comprises: an envelope, a saturated working fluid; and a wick.

29. (canceled)

30. A generator set comprising the internal combustion engine of claim 25.

31. A cylinder arrangement for an internal combustion engine, the cylinder arrangement comprising: a cylinder for receiving a piston of the internal combustion engine, wherein the cylinder is at least partially constructed from a technical ceramic material, and wherein one or more grooves are formed or otherwise provided in the outer surface of the cylinder.

32.-56. (canceled)

57. A piston arrangement for an internal combustion engine, the piston arrangement comprising: one or more pistons, wherein a piston rod of at least one of the pistons comprises an axially disposed bore formed therein; and a heat transfer member configured for location in the bore of the piston rod, wherein the heat transfer member is reconfigurable from a first, solid, state to a second state in which at least part of the heat transfer member is in a liquid state, the heat transfer member in said second state being movable relative to the bore of the piston rod so as to transfer heat away from and thus cool the piston rod as the piston reciprocates.

58.-60. (canceled)

61. A cooling arrangement for a fuel injection arrangement of an internal combustion engine, wherein the cooling arrangement comprises one or more heat pipes.

62.-63. (cancelled)

64. A piston sealing element for an internal combustion engine, the piston sealing element comprising: a first component, wherein the first component comprises or takes the form of a first technical ceramic material; and a second component embedded or otherwise provided on an outer surface of the first component, wherein the second component comprises or takes the form of a second, different, technical ceramic material.

65.-72. (canceled)

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0246] These and other aspects will now be described, by way of example only, with reference to the accompanying drawings, in which:

[0247] FIG. 1 shows a diagrammatic view of an internal combustion engine according to the present disclosure;

[0248] FIG. 2 shows an enlarged view of a piston arrangement of the internal combustion engine shown in Figure, with the piston at its bottom dead centre (BDC) position;

[0249] FIG. 3 shows an enlarged view of the piston arrangement of the internal combustion engine shown in FIG. 2, with the piston at its top dead centre (TDC) position;

[0250] FIG. 4 shows an exploded view of a piston of the internal combustion engine shown in FIG. 1;

[0251] FIG. 5 shows an axial section view of the cylinder of the internal combustion engine shown in FIG. 1;

[0252] FIG. 6 shows an exhaust reservoir housing of the internal combustion engine shown in FIG. 1;

[0253] FIGS. 7 and 8 show a fuel injection arrangement of the internal combustion shown in FIG. 1; and

[0254] FIGS. 9, 10 and 11 show a cooling arrangement for the fuel injection arrangement shown in FIGS. 7 and 8;

[0255] FIG. 12 shows a generator set comprising the internal combustion engine;

[0256] FIGS. 13 and 14 show diagrammatic views of an alternative internal combustion engine according to the present disclosure, with a piston at its bottom dead centre position and top dead centre position respectively;

[0257] FIG. 15 shows a diagrammatic view of an alternative internal combustion engine according to the present disclosure;

[0258] FIGS. 16 to 32 show a number of different pistons for use in the piston arrangements of the present disclosure; and

[0259] FIGS. 33 and 34 show a piston sealing element according to an example of the present disclosure.

DETAILED DESCRIPTION OF THE DRAWINGS

[0260] Referring first to FIG. 1 of the accompanying drawings, there is shown an internal combustion engine 10 according to the present disclosure.

[0261] As shown in FIG. 1, the internal combustion engine 10 comprises a piston arrangement, generally denoted 12, comprising a number of pistons 14 (two pistons are shown in FIG. 1). As will be described further below, each of the pistons 14 comprises a piston rod 16 and a piston crown 18.

[0262] As shown in FIG. 1, and referring now also to FIGS. 2 and 3 of the accompanying drawings, the piston rods 16 each comprise an axially disposed bore 20 formed therein. Heat transfer members 22 are configured for location in the bores 20 of the piston rods 16. The heat transfer members 22 are reconfigurable from a first, solid, state to a second state in which at least part of the heat transfer members 22 is in a liquid state, the heat transfer members 22 in said second state being movable relative to their respective bore 20 so as to transfer heat away from and thus cool the piston rod 16 as the pistons 14 reciprocate.

[0263] In use, the piston rods 16 will heat up during operation of the internal combustion engine 10. When the temperature of at least part of the heat transfer members 22 exceeds a preselected temperature threshold, e.g. the melting temperature of the heat transfer members 22, at least part of, and in particular embodiments all or a substantial part of, the heat transfer member 22 are reconfigured from the first, solid, state to the second, liquid, state. Reconfiguration of the heat transfer members 22 permits the heat transfer members 22 to move within the respective bores 20 and thus transport heat away from the hot piston end as the pistons 14 reciprocate between their bottom dead centre (BDC) position (as shown in FIG. 2) and their top dead centre (TDC) position (as shown in FIG. 3).

[0264] Beneficially, embodiments of the present invention resolve or at least mitigate issues with conventional systems in that no components are subjected to tensile cyclic loads, and no significant temperature gradients are developed. Embodiments of the present invention can thus achieve a life of at least 30,000 hours with a brake thermal efficiency of at least 70%.

[0265] In the illustrated piston arrangement 12, the heat transfer members 22 are formed from sodium. The heat transfer members 22 take the form of cylindrical members or substantially cylindrical members, the dimensions and/or shape of the heat transfer members 22 selected to facilitate location of the heat transfer members 22 in the bores 20 of the piston rods 16. However, it will be recognised that the heat transfer members 22 may be any suitable shape and/or size to complement the bores 20. The heat transfer members 22 may comprise or take the form of a slug of material.

[0266] In the illustrated piston arrangement 12, the piston rods 16 are constructed from cast iron. However, it will be understood that the piston rods 16 may alternatively be constructed from any other suitable material such as steel, e.g. stainless steel or an austenitic nickel-chromium-based superalloy such as Inconel®.

[0267] As shown in FIGS. 2 and 3, the internal combustion engine 10 further comprises a piston ring 24. In the illustrated internal combustion engine 10, the piston ring 24 is constructed from a technical ceramic material, namely Silicon Nitride.

[0268] An exploded view of one of the pistons 14 is shown in FIG. 4 of the accompanying drawings.

[0269] As shown in FIG. 4, the piston rod 16 comprises a pushrod portion 26. The pushrod portion 26 is constructed from cast iron. However, it will be understood that the pushrod portion 26 may alternatively be constructed from any suitable material, such as steel, e.g. stainless steel or an austenitic nickel-chromium-based superalloy such as Inconel®. The pushrod portion 26 comprises a threaded portion 28 for coupling the pushrod portion 26 to conrod 30 (shown in FIG. 1) of the internal combustion engine 10. The pushrod portion 26 comprises a threaded portion 32 for coupling the pushrod portion 26 to a wedge portion 34 of the piston rod 16.

[0270] As shown in FIG. 4, the wedge portion 34 is constructed from cast iron. However, it will be understood that the wedge portion 34 may alternatively be constructed from any suitable material, such as steel, e.g. stainless steel or an austenitic nickel-chromium-based superalloy such as Inconel®. The wedge portion 34 comprise a plurality of segments. The segments each have a threaded portion 36 for engaging the threaded portion 32 of the pushrod portion 26. The threaded portions 32, 36 form a coupling arrangement between the pushrod portion 26 and the wedge portion 34.

[0271] As shown in FIG. 4, the piston crown 18 is coupled to, or forms an end portion of the piston 14. The piston crown 18 is configured for coupling to the piston rod 16. In the illustrated internal combustion engine 10, the piston crown 18 is coupled to the piston rod 16 by an interference fit. The piston crown 18 comprises a wedge portion 38 configured, e.g. shaped and/or sized, to complementarily engage the wedge portion 28 of the piston rod 16. The piston crown 18 is constructed from Silicon Nitride.

[0272] In use, the configuration of the piston 14 means that load forces exerted on the piston crown 18 by the combustion reaction (as shown by the arrow F1 in FIG. 3) place the piston crown 18 in compression. This ensures that the ceramic material of the piston crown 18 is in compression, eliminating a common failure mode of ceramic materials.

[0273] As shown in FIG. 4, the piston 14 comprises an insulation arrangement, generally denoted 40. The insulation arrangement 40 is interposed between the piston rod 16 and the piston crown 18.

[0274] In the illustrated internal combustion engine 10, the insulation arrangement 40 comprises a plurality of segments 42. The insulation arrangement 40 is constructed from a Zirconium oxide material such as Zirconia®.

[0275] As shown in FIG. 4, the insulation arrangement 40 is configured and/or arranged such that when disposed on the piston rod 16 axial slots or spaces are defined between the segments 42 of the insulation arrangement 40.

[0276] Beneficially, this allows for differential thermal expansion of components of the piston 14 while providing thermal insulation between the piston crown 18 and the piston rod 16.

[0277] Referring again to FIG. 3, a lubrication arrangement 44 is provided. In the illustrated internal combustion engine 10, the lubrication arrangement 44 taking the form of a solid lubricant embedded in a coating applied to the piston crowns 18.

[0278] Referring again to FIG. 1 and now also to FIGS. 5 and 6 of the accompanying drawings, the internal combustion engine 10 comprises a cylinder arrangement, generally denoted 46, comprising a cylinder 48. In the illustrated internal combustion engine 10, the cylinder 48 is constructed from Silicon Nitride. The cylinder 48 comprises one or more inlet ports 50 and one or more exhaust ports 52.

[0279] As shown in FIG. 5, the internal combustion engine 10 comprises a gas scavenging arrangement, configured so that plug flow inlet charge air displaces combustion products with minimal mixing. In the illustrated internal combustion engine the gas scavenging arrangement comprises providing relatively large intake and/or exhaust total port flow areas.

[0280] Beneficially, the gas scavenging arrangement provides uniform circumferential heat flow into the cylinder 48 to minimise circumferential thermal gradients.

[0281] As shown in FIG. 6, one or more grooves 54 are formed or otherwise provided in the outer surface of the cylinder 48. The groove or grooves 54 comprise or take the form of micro-grooves. In the illustrated internal combustion engine 10, the grooves 54 are machined into the outer surface of the cylinder 48.

[0282] In use, hot exhaust gas, for example but not exclusively at a pressure of around 5 bar flows through the grooves 54 at high speed, maintaining the outer surface of the cylinder 48 at a relatively high temperature.

[0283] Beneficially, this decreases the thermal gradient between the inside and outside of the cylinder 48. As the cylinder 48 is constructed from a ceramic material, the decrease in thermal gradient between the inside and outside of the cylinder 48 mitigates a failure mode of ceramic materials.

[0284] As shown in FIG. 6, the internal combustion engine 10 comprises an exhaust reservoir 56 configured to receive exhaust from the combustion reaction. The exhaust reservoir 56 is disposed around an outer surface portion of the cylinder 48. The exhaust reservoir 56 may be defined by an exhaust reservoir housing 58.

[0285] As shown in FIG. 6, one or more grooves 60 are formed or otherwise provided in the inner surface of the exhaust reservoir housing 58. The grooves 60 comprise or take the form of micro-grooves. In the illustrated internal combustion engine 10, the grooves 60 are machined into the one or more inner surface of the exhaust reservoir housing 58, e.g. an axial end face of the exhaust reservoir housing 58.

[0286] In use, hot exhaust gas, for example but not exclusively at a pressure of around 5 Bar flows through the grooves 60 at high speed, maintaining the outer surface of the cylinder 48 at a relatively high temperature.

[0287] Beneficially, this decreases the thermal gradient between the inside and outside of the cylinder 48. Since the cylinder 48 is constructed from a ceramic material, the decrease in thermal gradient between the inside and outside of the cylinder 48 mitigates a failure mode of ceramic materials.

[0288] In use, exhaust ducts (not shown) transport combustion products from the exhaust reservoir 56 to an exhaust turbine inlet (not shown).

[0289] Referring now also to FIGS. 7 and 8 of the accompanying drawings, the exhaust reservoir housing 58 is modular in construction, the exhaust reservoir housing 58 being manufactured in two or more parts. Beneficially, this facilitates ease of manufacture.

[0290] As shown in FIGS. 7 and 8, and referring now also to FIGS. 9, 10 and 11 of the accompanying drawings, the internal combustion engine 10 has a fuel injection arrangement, generally denoted 62, comprising a tubular boss portion 64 having a bore 66 for receiving a fuel injector 68 (shown in FIG. 9). The boss portion 64 extends radially inwards from a circumferential wall of the exhaust reservoir housing 58. A distal end portion of the boss portion 64 is shaped and dimensioned to engage the outer surface of the cylinder 48, such that the bore 66 surrounds and communicates with injector port 70 formed through the wall of the cylinder 48.

[0291] As shown in FIGS. 9 and 10, a cooling arrangement, generally denoted 72 is associated with the fuel injection arrangement 62. The cooling arrangement 72 comprises or takes the form of a heat pipe-type cooling arrangement, as described further below.

[0292] Beneficially, the cooling arrangement 72 ensures that the fuel injector 68 remains within maximum service temperature even when located in a wall of the cylinder 48 at high temperature, e.g. a temperature of around 1000C.

[0293] As shown in FIGS. 9 and 10, a sleeve 74 is disposed within the bore 66. The sleeve 74 is constructed from a technical ceramic material, in particular a technical ceramic with low thermal conductivity. In the illustrated internal combustion engine 10, the sleeve 74 is constructed from Zirconia. A cylindrical block 76 is disposed within the sleeve 74. The cylindrical block 76 is constructed from a technical ceramic, in particular a technical ceramic with high thermal conductivity. In the illustrated internal combustion engine 10, the cylindrical block 76 is constructed from Aluminium Nitride.

[0294] As shown in FIGS. 9 and 10, the cooling arrangement 72 comprises heat pipes 78 arranged in parallel and which communicate with a heat sink 80. In the illustrated internal combustion engine 10, the heat pipes 78 are constructed from stainless steel.

[0295] The heat sink 80 is disposed in a charge volume, generally denoted 82, which is cooled. As shown, the heat pipes 78 have a length greater than the fuel injector 68, with the heat pipes 78 extending from at or near a tip of the fuel injector 68 and past the head of the fuel injector 68.

[0296] As shown in FIG. 11, the heat pipes 78 comprise an envelope 84, a saturated working fluid 86 and a wick 88. The working fluid 86 comprises or takes the form of a liquid at ambient temperature. In the illustrated internal combustion engine 10, the working fluid comprises sodium.

[0297] In use, when the end of the fuel injector 68 heats up and the temperature of the working fluid 86 exceeds its boiling point, the working fluid 86 will vaporise and travel up the heat pipes 68 towards the heat sink 80 where it will condense and be returned to the hot end via the wick 88 through capillary pressure. Beneficially, the cooling arrangement 72 conducts heat from the fuel injector 68, due to the latent heat of vaporisation.

[0298] Beneficially, this ensures that the fuel injectors remain within maximum service temperature even when located in a wall of a cylinder 48 at high temperature, e.g. a temperature of around 1000C.

[0299] Referring again to FIG. 1, the illustrated internal combustion engine 10 comprises one or more crank 90 (two cranks 90 are shown in FIG. 1), the pistons 14 coupled to the cranks 90.

[0300] In the illustrated internal combustion engine 10, a metal frame 92 is provided to react axial combustion and/or inertial loads and/or side loads from the cranks 90. Sleeve bearings 94 are provided to react side loads from the cranks 90.

[0301] As shown in FIGS. 1, 2 and 3, the internal combustion engine 10 further comprises collars 96 and insulating collars 98. The collars 96 are constructed from a ceramic material, namely Silicon Nitride. The insulating collars 98 are constructed from a ceramic insulation material, namely Zirconium oxide.

[0302] In the illustrated internal combustion engine 10, the internal combustion engine 10 further comprises non-structural insulation 100. The insulation 100 is provided between the outside of the cylinder 48 and the exhaust reservoir housing 58 and around the outside of the exhaust reservoir housing 58.

[0303] FIG. 12 of the accompanying drawings shows a generator set 102 comprising the internal combustion engine 10.

[0304] As shown in FIG. 12, the generator set 102 comprises a generator 104 coupled to the internal combustion engine 10. The generator 104 converts the mechanical energy output from the internal combustion engine 10 into electrical energy. The generator set 102 comprises a power source 106, which in the illustrated generator set 102 takes the form of a rechargeable battery, coupled to the generator 104. The generator 104 supplies the electrical energy to charge the power source 106.

[0305] As shown in FIG. 12, the generator set 102 is coupled to an electric motor 108. The motor 108 is coupled to the power source 106. The power source 106 supplies the electrical energy to drive the motor 108. As shown, the power source 106 may supply the electrical energy to another component or system, for example but not exclusively the electrical system of a vehicle (not shown).

[0306] In use, the internal combustion engine 10 will run at constant load/speed and peak efficiency. The generator set 102 can provide power either directly to an appliance, for example for static generator set applications, to electric motors to provide propulsion for transport applications, and/or an auxiliary propulsion unit (APU), e.g. a marine APU or heavy good vehicle (HGV) APU.

[0307] In use, surplus power can be stored in the power source, e.g. battery. Once the power source, e.g. battery, charges, the internal combustion engine can cut out for all-electric operation until the battery discharges and the cycle repeats.

[0308] The generator sets can be self-contained 100 kW and 300 kW power modules housed in thermally- and acoustically-insulating casings. The power modules are scalable, with multi-module power plants being used to meet the specific power requirements of end users.

[0309] It will be understood that various modifications may be made without departing from the scope of the claimed invention.

[0310] For example, while the internal combustion engine 10 shows an opposed piston and cylinder arrangement, FIGS. 13 and 14 show an alternative internal combustion engine 110 having another, non-opposed, piston and cylinder arrangement.

[0311] As shown in FIGS. 13 and 14, the internal combustion engine 110 comprises a piston arrangement, generally denoted 112, comprising a piston 114. The piston 114 comprises a piston rod 116 and a piston crown 118.

[0312] The piston rod 116 comprises an axially disposed bore 120 formed therein. A heat transfer member 122 is configured for location in the bore 120 of the piston rod 116. The heat transfer member 122 is reconfigurable from a first, solid, state to a second state in which at least part of the heat transfer member 122 is in a liquid state, the heat transfer member 122 in said second state being movable relative to the bore 120 so as to transfer heat away from and thus cool the piston rod 116 as the piston 114 reciprocates.

[0313] In use, the piston rod 116 will heat up during operation of the internal combustion engine 110. When the temperature of at least part of the heat transfer member 122 exceeds a preselected temperature threshold, e.g. the melting temperature of the heat transfer member 122, at least part of, and in particular embodiments all or a substantial part of, the heat transfer member 122 is reconfigured from the first, solid, state to the second, liquid, state. Reconfiguration of the heat transfer member 122 permits the heat transfer member 122 to move within the respective bore 120 and thus transport heat away from the hot piston end as the piston 114 reciprocates between the bottom dead centre (BDC) position and top dead centre (TDC) position.

[0314] In the illustrated piston arrangement 112, the heat transfer member 122 is formed from sodium. The heat transfer member 122 takes the form of a cylindrical member or substantially cylindrical member, the dimensions and/or shape of the heat transfer member 122 selected to facilitate location of the heat transfer member 122 in the bore 120 of the piston rod 116. However, it will be recognised that the heat transfer member 122 may be any suitable shape and/or size to complement the bore 120. The heat transfer member 122 may comprise or take the form of a slug of material.

[0315] In the illustrated piston arrangement 112, the piston rod 116 is constructed from cast iron. However, it will be understood that the piston rod 116 may alternatively be constructed from any other suitable material such as steel, e.g. stainless steel or an austenitic nickel-chromium-based superalloy such as Inconel®.

[0316] Referring now to FIG. 15, there is shown an alternative internal combustion engine 210. The internal combustion engine 210 is similar to the internal combustion engine 10 with like reference signed incremented by 200.

[0317] As shown in FIG. 15, the internal combustion engine 210 comprises a piston arrangement, generally denoted 212, comprising a number of pistons 214 (two pistons are shown in FIG. 12). Each of the pistons 214 comprises a piston rod 216 and a piston crown 218.

[0318] As shown in FIG. 15, the piston rods 216 each comprise an axially disposed bore 220 formed therein. Heat transfer members 222 are configured for location in the bores 220 of the piston rods 216. The heat transfer members 222 are reconfigurable from a first, solid, state to a second state in which at least part of the heat transfer members 222 is in a liquid state, the heat transfer members 222 in said second state being movable relative to their respective bore 220 so as to transfer heat away from and thus cool the piston rod 216 as the pistons 214 reciprocate.

[0319] In use, the piston rods 216 will heat up during operation of the internal combustion engine 10. When the temperature of at least part of the heat transfer members 222 exceeds a preselected temperature threshold, e.g. the melting temperature of the heat transfer members 222, at least part of, and in particular embodiments all or a substantial part of, the heat transfer member 222 are reconfigured from the first, solid, state to the second, liquid, state. Reconfiguration of the heat transfer members 222 permits the heat transfer members 222 to move within the respective bores 220 and thus transport heat away from the hot piston end as the pistons 214 reciprocate between their bottom dead centre (BDC) position and their top dead centre (TDC) position.

[0320] In the illustrated piston arrangement 212, the heat transfer members 222 are formed from sodium. The heat transfer members 222 take the form of cylindrical members or substantially cylindrical members, the dimensions and/or shape of the heat transfers members 222 selected to facilitate location of the heat transfer members 222 in the bores 220 of the piston rods 216. However, it will be recognised that the heat transfer members 222 may be any suitable shape and/or size to complement the bores 220. The heat transfer members 222 may comprise or take the form of a slug of material.

[0321] While in the internal combustion engine 10 the pistons are modular in construction and are at least partially constructed from a technical ceramic, in the internal combustion engine 210, the pistons 214 are each a unitary construction and are constructed from Inconel® or stainless steel.

[0322] As described above, various modifications may be made without departing from the scope of the claimed invention.

[0323] For example, FIGS. 16 to 32 of the accompanying drawings show a number of different pistons 314,414,514,614,714 according to the present disclosure.

[0324] The piston 314 shown in FIG. 16 is a solid piston. Beneficially, the provision of a solid piston facilitates ease of manufacture.

[0325] FIGS. 17 and 20 to 23 show an alternative piston 414 to that shown in FIG. 16. As shown, the piston 414 comprises a plurality of axial bores 424, 426, which in the illustrated piston 414 are formed by drilling, in the piston crown 418.

[0326] Beneficially, the provision of a piston which comprises one or more bores 424,426 results in a reduction in the mass of the piston 414. This, in turn, results in a reduction of the reciprocating mass within the internal combustion engine, which given that the engine may be running at a high rotational speed, for example but not exclusively 3000 rpm to 7000 rpm, reduces the inertial load and thus significantly improves the working life of the piston arrangement.

[0327] As shown in FIG. 22, the piston 414 further comprises a fluid communication arrangement, general denoted 428. The fluid communication arrangement 428 comprises axial bores 430 formed or otherwise provided, e.g. by a drilling and/or milling process, in the piston crown 418 and radial bores 432 (three radial bores 432 are shown in FIG. 22) formed or otherwise provided, e.g. by a drilling and/or milling process, in the piston crown 418. The radial bores 432 communicate with the one or more axial bores in the piston crown 418.

[0328] In use, the fluid communication arrangement 428 facilitates fluid communication to urge one or more seal elements, e.g. piston rings, mounted on the piston crown 418 against the cylinder bore during running.

[0329] Beneficially, this acts to energise and/or provide additional energisation of the seal elements, e.g. piston rings, against the cylinder.

[0330] FIGS. 18 and 24 to 26 show an alternative piston 514 to that shown in FIG. 16. As shown, the piston 514 comprises a plurality of bores 524 and a plurality of part-annular pockets 526 formed in piston crown 518, which in the illustrated piston 514 are formed by milling.

[0331] FIGS. 19 and 27 to 29 show a further alternative piston 614 to that shown in FIG. 16. As shown, the piston 614 has a cavity 626 formed in the piston crown 618. A number of radial struts 634 provide structural support. The piston 614 is formed by a casting process, .e.g. a lost core casing process, or injection moulding.

[0332] FIGS. 30 to 32 show a further alternative piston 714 to that shown in FIG. 16. As shown, the piston 714 has a cavity 726 formed in the piston crown 718. The piston 714 is formed by a casting process, .e.g. a lost core casing process or injection moulding.

[0333] It will be understood that the pistons may alternatively or additionally be manufactured using an additive manufacturing process such as 3D printing.

[0334] In each of the pistons 314, 414, 514, 614, 714 shown in FIGS. 16 to 32, the piston rods 316, 416, 516, 616, 716 are tapered, i.e. a distal end portion of the piston rod 316, 416, 516, 616, 716 defines a greater outer dimension e.g. diameter, that a proximal end portion of the piston rod 316, 416, 516, 616, 716.

[0335] As described above, various modifications may be made without departing from the scope of the claimed invention.

[0336] FIGS. 33 and 34 of the accompanying drawings show a piston sealing element 800 according to the present disclosure, which in the illustrated example takes the form of a piston ring. As shown, the piston sealing element 800 comprises a first component 802 and a second component 804. The first component 802 comprises or takes the form of a first technical ceramic material, which in the illustrated sealing element 800 is Silicon Nitride. The second component 804 is embedded on an outer surface of the first component 802. The second component 80 comprises or takes the form of a second, different, technical ceramic material, which in the illustrated sealing element 800 is Titanium Nitride.