Reciprocating heat engine with hot cylinder head and cold cylinder

Abstract

Reciprocating heat engine with hot cylinder head and cold cylinder The reciprocating heat engine (1) having a hot cylinder head and a cold cylinder comprises a cooled cylinder casing (5) receiving a cold cylinder (6) covered with a lubricating film (7) and in which a piston (2) connected to a power transmission means (3) translates to form a variable-volume hot chamber (11), and a hot cylinder head (10) applied to and held by a cylinder head application means (24) but free to expand on said cylinder casing (5), while a hot crown (19) is interposed between said chamber (11) and the piston (2) and applied to and held by a crown application means (23) on said piston (2) but free to expand, the piston (2) including a cooled piston sealing ring (37) having a piston sealing means (30).

Description

[Technical field]

[0001] The present invention relates to a reciprocating heat engine having a hot cylinder head and a cold cylinder, the engine being particularly adapted to carry out a regenerative Brayton thermodynamic cycle, usually carried out by a centrifugal compressor and a turbine. [Background technology]

[0002] Regenerative Brayton cycle engines generally include separate components dedicated to each of the phases of the cycle, which occur sequentially and simultaneously within the components, unlike Rocha, Miller, Atkinson, or Diesel Beau cycle reciprocating internal combustion engines, whose phases occur sequentially within one and the same cylinder.

[0003] Thus, a regenerative Brayton cycle engine includes at least one compressor, at least one regenerative exchanger, at least one continuously operating combustor or internal or external heat source, and at least one expansion valve.

[0004] Assigning each phase of the thermodynamic cycle to a dedicated member has various advantages: in particular, the temperature of the inner wall of each such member can remain very close to the temperature of the gas during that phase.

[0005] For example, the temperature of the inner walls of the compressor of a regenerative Brayton cycle engine can be kept as low as possible, thereby helping to minimize the work of compression and maximize the overall thermodynamic efficiency of the engine.

[0006] Conversely, the inner walls of the engine's expansion valves are in contact with the hot gases coming from the combustor, so their temperature is high and must in any case be kept as close as possible to the average temperature of those gases from the start to the end of their expansion.

[0007] Despite these advantages, the maximum thermodynamic efficiency of an engine with a centrifugal compressor and a regenerative Brayton cycle turbine is actually not much higher than that of a conventional spark ignition engine, and is at most comparable to that of a high speed diesel engine.

[0008] In all cases, the efficiency remains lower than that of slow-speed, two-stroke diesel engines of tens of megawatts used, for example, for ship propulsion or stationary power generation.

[0009] Furthermore, engines with centrifugal compressors and regenerative Brayton cycle turbines are not well suited for low power output and can only operate over a limited power range, outside of which their efficiency drops significantly.

[0010] This is why engines with centrifugal compressors and regenerative Brayton cycle turbines are primarily used in applications where efficiency is not the sole objective, but rather requiring, for example, high specific and volumetric power, low sound and vibration emissions, long service life, or reduced maintenance.

[0011] This is the case, for example, in certain naval vessels fitted with "Rolls-Royce WR 21" regenerative Brayton cycle engines having centrifugal compressors and turbines, the efficiency of which hardly exceeds 40 percent, whereas the efficiency of slow speed two-stroke diesel engines fitted to certain vessels exceeds 50 percent.

[0012] This is also the case for certain generators, such as the microturbine T100 from Turbec or the microturbine C65 from Capstone, which most often operate in combined electricity and heat generation, and which, although their electrical efficiency is only around 28-30 percent, offer a very long service life and require almost no maintenance.

[0013] An advantage of these turboshaft engines is that their turbines can withstand temperatures of about 1300 degrees Celsius. However, their overall thermodynamic efficiency remains limited by the efficiency of their constituent centrifugal compressors and turbines, which rarely exceed 80 percent over a relatively narrow operating range.

[0014] In view of the above, it would be particularly advantageous to be able to replace the centrifugal compressor and turbine of a regenerative Brayton cycle engine with a positive displacement piston machine, which, as is well known, has a higher efficiency.

[0015] This is the subject, for example, of U.S. Pat. No. 4,653,269, issued Mar. 31, 1987, in which the expansion turbine normally found in a regenerative Brayton cycle turboshaft engine is replaced by a piston positive displacement expansion cylinder.

[0016] However, calculations demonstrate that if the inner walls of the positive displacement expansion valve are cooled, for example, and maintained at about 100 degrees Celsius, as is the case for large-scale commercially produced reciprocating engines, the thermodynamic efficiency of a regenerative Brayton cycle engine cannot exceed that of a motor vehicle diesel engine.

[0017] In order for a regenerative Brayton cycle engine having a positive displacement expansion valve to provide very high thermodynamic efficiency, it is essential that the inner walls of the expansion valve be maintained at a temperature close to the average temperature of the gases expanded within the expansion valve.

[0018] For example, if hot gas is introduced into an expansion valve at a temperature of 1300 degrees Celsius and exits the expansion valve at the end of expansion at a temperature of 600 degrees Celsius, the inner walls of the expansion valve must be maintained at a temperature of approximately 950 degrees Celsius.

[0019] The problem is that at such temperatures it is not possible to maintain an oil film on the walls of the expansion valve cylinder to lubricate any sealing segments that the expansion valve piston may include as it moves within the cylinder.

[0020] In fact, from about 160 degrees Celsius, the oil film on the cylinder begins to coke and then combust above 250 degrees Celsius.

[0021] Thus, the construction of a regenerative Brayton cycle engine having high thermodynamic efficiency faces a two-fold challenge.

[0022] In fact, the engine consists of a centrifugal compressor and a turbine capable of withstanding high temperatures, but in this case the modest efficiency of these components does not allow the engine to exceed an overall efficiency equivalent to that of an automobile diesel engine, or it consists of a piston positive displacement expansion valve, which requires a piston with a sealing segment sliding on an oil film formed on the surface of the cylinder in order to be sealed, and which for this purpose must remain at a temperature not exceeding about 120 degrees Celsius, which also does not allow the overall efficiency of the engine to be competitive.

[0023] In this regard, it would be advantageous to be able to combine the ability of a turbine to operate at high temperatures with the ability of a piston displacement machine to expand gases with high efficiency.

[0024] For this purpose, the heat engine with transmission-expansion and regeneration according to WO2016120560, published on August 4, 2016 and belonging to the present Applicant, is provided with a non-contact piston sealing means consisting of an expandable perforated continuous ring which expands when subjected to a certain internal pressure and approaches to within a few micrometers of the expansion valve cylinder associated with it without contacting said expansion valve cylinder, while allowing the compressed air to escape through a calibrated orifice which penetrates said continuous ring in its radial thickness.

[0025] The above mentioned fluid cushion sealing device is also the subject of French Patent No. 3032252, belonging to the applicant, published on May 25, 2018. This device makes it possible to provide a contactless sealing, thus no longer using oil to lubricate segments operating by contact, and thus making it possible to engage with high temperature expansion valve cylinders maintained at temperatures of several hundred degrees Celsius.

[0026] In this regard, therefore, the use of a piston positive displacement expansion valve effectively enables the production of a regenerative Brayton cycle engine, maximizing the efficiency of the engine to significantly exceed that of a Diesel cycle engine.

[0027] Specifically, calculations and simulations have demonstrated that the thermodynamic efficiency of a piston positive displacement regenerative Brayton cycle engine can reach or even exceed 70 percent, which in practice indicates that, once unavoidable thermal and mechanical irreversibilities due to the very construction of the engine are eliminated, may lead to the production of engines with brake energy efficiencies in excess of 60 percent.

[0028] A problem encountered with the fluid cushion sealing device of FR 3032252 is that the temperature of the cylinder remains excessive with respect to the available material with which the perforated continuous ring can be made.

[0029] In fact, in order for the efficiency of a piston positive displacement regenerative Brayton cycle engine to be significantly higher than that of existing diesel engines, gas must be introduced into its expansion valve at a temperature of the order of 1300 degrees Celsius and under a pressure of about 20 bar.

[0030] These operating conditions indicate that the temperature of the inner wall of the expansion valve stabilizes at approximately 950 degrees Celsius.

[0031] If the continuous perforated ring according to French Patent No. 3032252 is located within a few microns of the cylinder with which it cooperates, it will in fact be at the temperature of the cylinder, which is about 950 degrees Celsius.

[0032] However, there is no material that can both manufacture the ring and withstand such temperatures.

[0033] Even superalloys such as "Udimet 720", which are used in particular in the aeronautical and space industries and are known for their resistance to extreme temperatures, are unable to withstand such temperatures without undergoing creep and whilst being subjected to the expansion stresses exerted by the continuous perforated ring of the fluid cushion sealing device according to French Patent No. 3 032 252.

[0034] It is for this reason in particular that in the regenerative cooling system of EP Patent No. 3585993 belonging to the present Applicant, published on April 7, 2021, the temperature of the expansion valve, in particular of the inner wall of the cylinder, is reduced to a practical value of approximately 700 degrees Celsius, by using more conventional materials than high-temperature resistant ceramics.

[0035] For example, the superalloy Udimet 720 resists creep at temperatures of 700 degrees Celsius when subjected to stresses not exceeding 230 megapascals.

[0036] The regenerative cooling system according to EP 3585993 provides a cooling enclosure which surrounds the expansion valve, but leaves a gas circulation space between the enclosure and the expansion valve in which gases leaving the expansion valve itself circulate at temperatures in the range of 500 degrees Celsius to 600 degrees Celsius.

[0037] Thus, in accordance with the regenerative cooling system of EP 3585993, the exhaust gases of the expansion valve maintain the temperature of the inner walls of the expansion valve at a temperature of about 700 degrees Celsius, while the heat rejected by said gases is essentially recovered for reintroduction into the cycle by a regenerative heat exchanger included in the piston regenerative Brayton cycle reciprocating engine.

[0038] In this connection, the fluid cushion sealing device of French Patent No. 3032252 can be used with a continuous perforated ring, for example made of the "Udimet 720" superalloy.

[0039] However, in return for this possibility, the cylinders and cylinder heads of regenerative Brayton cycle reciprocating engines must be made from materials having a high nickel content, such as "Ni-resist" cast iron, which presents an economic disadvantage due to nickel's high volatility and high price.

[0040] It should be noted that in all cases the temperature of the expansion valve remains at least 600 degrees Celsius higher than the temperature of the rest of the engine, particularly the movable joint and the transmission casing in which it is housed.

[0041] Advantageously, the expansion differential resulting from this temperature difference can be managed in particular by a double-acting expansion cylinder with adaptive support, which is the subject of European Patent No. 3350433, published on August 7, 2019, belonging to the present Applicant.

[0042] The support allows for isotropic or anisotropic expansion of an expansion cylinder that is significantly different from the expansion of the transmission casing to which it is fixed, without impairing either the operation of the cylinder or the operation of the piston moving within the cylinder.

[0043] The support also keeps the piston centered within the cylinder, transmits axial forces resulting from gas expansion to the transmission casing, and limits heat transfer from the expansion valve cylinder to the casing.

[0044] From reading the above, it will be appreciated that at this stage there is no entirely satisfactory configuration which allows for the manufacture of a piston regenerative Brayton cycle reciprocating engine under the best possible conditions.

[0045] Specifically, the fluid cushion sealing device must be supplied with compressed air by a compressor which consumes a portion of the work available on the shaft of the piston regenerative Brayton cycle reciprocating engine, compromising the overall efficiency of the piston regenerative Brayton cycle reciprocating engine.

[0046] This reduces the ultimate energy efficiency of the engine, which becomes even more so when the engine is operating at low power because the amount of compressed air supplied to the fluid cushion sealing system remains approximately constant regardless of the engine speed and load.

[0047] Furthermore, to ensure permanent operation of the fluid cushion sealing device one has to resort to a regenerative cooling system according to EP 3585993, which system is not energy neutral.

[0048] Specifically, the cooling system causes the gases exhausted from the expansion valve to follow a tortuous path, creating a pressure drop that reduces the overall efficiency of the piston regenerative Brayton cycle reciprocating engine.

[0049] Additionally, heat extracted from the inside walls of the expansion valve by the regenerative cooling system is reintroduced into the Brayton cycle upstream of the combustor or heat source by a regenerative heat exchanger that is not 100 percent efficient.

[0050] Thus, part of the heat extracted from the inner wall of the expansion valve is lost and the power passing through the exchanger is increased by the presence of the cooling system.

[0051] In addition, the specific power output of a piston regenerative Brayton cycle reciprocating engine is substantially reduced by the regenerative cooling system according to EP 3585993. This implies an upward sizing of the engine to meet the power output target of the intended application.

[0052] It is also noted that the development of the fluid cushion sealing device of FR 3032252 remains complex, in particular to ensure its correct operation in situations of non-stationary applications subject to shocks and vibrations. Summary of the Invention

[0053] Thus, without excluding other applications in any field, the hot cylinder head and cold cylinder reciprocating heat engine according to the invention is provided inter alia for making a piston regenerative Brayton cycle reciprocating engine in which the hot expansion valve primarily limits heat losses and at the same time ensures a robust and durable sealing between the piston of said expansion valve and the cylinder.

[0054] In the field of application of piston reciprocating heat machines in general, and heat engines in particular, the result of the present invention is a reciprocating heat engine having a hot cylinder head and a cold cylinder, The cylinder head and piston crown of this reciprocating heat engine are maintained at high temperatures to limit cooling of the hot gases in contact therewith; The sealing between the piston and cylinder of this reciprocating heat engine can be achieved by segments made of cast iron or steel, such as those contained in conventional spark ignition or diesel cycle internal combustion engines; This reciprocating heat engine no longer uses the fluid cushion sealing device that is the subject of FR Patent No. 3032252 and therefore no longer requires a regenerative cooling system as described in EP Patent No. 3585993 and therefore no longer suffers the power and efficiency losses associated with the use of a compressor to feed said sealing device, or the additional pressure losses at the outlet of the expansion valve associated with a more tortuous path for the gas, or the heat losses due to a regenerative heat exchanger efficiency less than "1", or the specific power losses of the engine associated with this configuration.

[0055] Furthermore, as an alternative to materials having a high nickel content, such as "Niresist" cast iron, the high temperature cylinder head of a reciprocating heat engine having a high temperature cylinder head and a low temperature cylinder according to the present invention can be made from silicon carbide (a material which has high mechanical strength at high temperatures, is abundant and inexpensive), while the cylinders of the engine can be made from lower cost cast iron, such as that typically used to make cylinder casings for automotive diesel engines.

[0056] In addition, the lower density of silicon carbide and the absence of a regenerative cooling system leads to a lower weight of the reciprocating heat engine having a high temperature cylinder head and a low temperature cylinder according to the present invention and a lower overall heat capacity of the engine, which promotes a quicker rise in temperature of the engine by reducing the energy required to reach the operating temperature of the engine, leading to a lower energy consumption of the engine, especially when the engine is applied in road, rail or sea transport.

[0057] It will be understood that the reciprocating heat engine with a hot cylinder head and a cold cylinder according to the invention may further be applied to any other application which is similar in concept and principle to heat engines, generally stationary or mobile, with internal or external combustion, and which may advantageously utilize the specific features and functions of said engine according to the invention.

[0058] Other features of the invention are set forth in the description and in the secondary claims which depend directly or indirectly from the specification and the main claims.

[0059] A reciprocating heat engine having a hot cylinder head and a cold cylinder, comprising a cooled cylinder casing in which is arranged at least one cold cylinder in which a piston oriented and / or positioned by a piston guide means can move in translation, said piston being directly or indirectly connected to at least one rotating or reciprocating power output shaft by a power transmission means housed in a transmission casing, the reciprocating heat engine comprising: A lubricating means for forming a lubricating film between the low-temperature cylinder and the piston; a cylinder casing cooling means for cooling the cold cylinder casing to maintain all or a portion of the inner surface of the cold cylinder at a temperature sufficiently low to prevent premature aging, coking, or burning of the lubricating film; at least one high-temperature cylinder head, the operating temperature of which is significantly higher than the operating temperature of a cooled cylinder casing which it covers to form, together with a piston, a high-temperature variable volume chamber for accommodating a working gas, said cylinder head being applied and held against said cooled cylinder casing by cylinder head application means which allow the cylinder head to freely expand relative to said cylinder casing, and being positioned against said cylinder casing by cylinder head centering means, on the other hand; at least one piston sealing ring provided on the periphery of the piston, said ring comprising, on the one hand, piston sealing means forming a seal between the piston and the cold cylinder, and on the other hand being cooled by sealing ring cooling means; at least one high temperature crown interposed between the high temperature variable volume chamber and the piston, the operating temperature of which is significantly higher than the operating temperature of the cooled cylinder casing, said crown being applied and held against the piston on the one hand by a crown application means which allows said crown to freely expand relative to said piston, and on the other hand being positioned against said piston by a crown centering means.

[0060] A reciprocating heat engine having a hot cylinder head and a cold cylinder according to the present invention includes a sealed thermal insulation means interposed between the cold cylinder casing and the hot cylinder head.

[0061] A reciprocating heat engine having a hot cylinder head and a cold cylinder according to the present invention includes thermal insulation means interposed between the hot crown and the piston.

[0062] A reciprocating heat engine having a hot cylinder head and a cold cylinder according to the present invention is provided with thermal insulation means comprising a reflective screen.

[0063] A reciprocating heat engine having a hot cylinder head and a cold cylinder according to the present invention includes thermal insulation means comprising a honeycomb or fibrous insulating material occupying all or a portion of the space between the hot crown and the piston.

[0064] The reciprocating heat engine with a hot cylinder head and a cold cylinder according to the invention is provided with a thermal insulation means consisting of sealed thermal insulation means and / or at least one thermal insulation ring made of a material with low thermal conductivity.

[0065] The reciprocating heat engine having a high temperature cylinder head and a low temperature cylinder of the present invention comprises a low thermal conductivity material consisting essentially of zirconium oxide.

[0066] The reciprocating heat engine having a hot cylinder head and a cold cylinder according to the present invention comprises an insulating ring forming a sealed insulating means in direct or indirect contact with the cold cylinder casing and / or the hot cylinder head via at least one contact edge of small surface area which prevents the working gas from passing between the cold cylinder casing and the hot cylinder head.

[0067] The reciprocating heat engine having a hot cylinder head and a cold cylinder according to the invention comprises an insulating ring forming an insulating means which is in direct or indirect contact with the hot crown and / or the piston by at least one contact edge of small surface area.

[0068] The reciprocating heat engine having a hot cylinder head and a cold cylinder according to the present invention comprises a cylinder head seal interposed between an insulating ring forming a sealed insulation means and the cooling cylinder casing and / or between said ring and the hot cylinder head.

[0069] The reciprocating heat engine having a hot cylinder head and a cold cylinder according to the invention comprises a piston seal interposed between an insulating ring forming the thermal insulation means and the hot crown and / or between said ring and the piston.

[0070] A reciprocating heat engine having a hot cylinder head and a cold cylinder according to the present invention includes a hot cylinder head and / or a hot crown made wholly or partially of a material that can withstand high temperatures.

[0071] A reciprocating heat engine having a high temperature cylinder head and a low temperature cylinder according to the present invention comprises a material that can withstand high temperatures and that is primarily comprised of silicon carbide.

[0072] A reciprocating heat engine having a hot cylinder head and a cold cylinder according to the invention comprises a hot cylinder head having a concave conical cylinder head surface by means of which the cylinder head is applied and held by a cylinder head application means against a circular cylinder contact edge provided on a cold cylinder casing, the angle of the concave cone formed by said surface being such that, when said surface slides over said edge due to the difference between the thermal expansion of the cylinder head and the thermal expansion of the cylinder casing, the axial distance separating the bearing point of the cylinder head application means for the hot cylinder head from the cold cylinder casing remains approximately constant, all other conditions being equal.

[0073] A reciprocating heat engine having a hot cylinder head and a cold cylinder according to the invention comprises a hot crown having a concave conical crown surface by which the crown is applied and held against a piston circular contact edge provided on the piston by a crown application means, the angle of the concave cone formed by the surface being such that when the surface slides over the edge due to the difference between the thermal expansion of the crown and the thermal expansion of the piston, the axial distance separating the bearing point of the crown application means against the hot crown from the piston remains substantially constant, all other conditions being equal, while the concave conical crown surface and the piston circular contact edge form a crown centering means.

[0074] A reciprocating heat engine having a hot cylinder head and a cold cylinder in accordance with the present invention includes a hot crown having an aerodynamic passivation bead around its periphery.

[0075] A reciprocating heat engine having a hot cylinder head and a cold cylinder according to the present invention has the outside of the hot cylinder head covered with a thermal insulation material.

[0076] A reciprocating heat engine having a hot cylinder head and a cold cylinder according to the present invention is provided with a piston sealing ring having a piston guide means consisting of an annular sliding surface.

[0077] The reciprocating heat engine with hot cylinder head and cold cylinder according to the invention comprises a cooled cylinder casing clamped and held between a lower hot cylinder head and an upper hot cylinder head by a cylinder head application means, while the piston is double-acting and includes, on the one hand, a lower piston rod connecting the piston to a power transmission means and passing through the lower hot cylinder head via a lower rod orifice, and, on the other hand, a lower hot crown and an upper hot crown to define, together with the lower and upper hot cylinder heads, a lower variable-volume hot chamber and an upper variable-volume hot chamber.

[0078] The reciprocating heat engine having a high-temperature cylinder head and a low-temperature cylinder according to the present invention comprises: at least one setback pillar longitudinally penetrated by a rod tunnel, a first pillar end of the pillar resting directly or indirectly on a transmission casing while a second pillar end of the pillar supports a lower hot cylinder head, the first end being capable of pivoting about a ball joint and / or bending relative to the casing while the second end being capable of pivoting about a ball joint and / or bending relative to the lower hot cylinder head; at least one traction rod forming a cylinder head application means and housed at least partially in a rod tunnel, a first rod end of said traction rod being fixed directly or indirectly to the transmission casing while a second rod end of said rod being fixed directly or indirectly to the upper high-temperature cylinder head, said first end being able to pivot about a ball joint and / or bend relative to the casing while said second end being able to pivot about a ball joint and / or bend relative to the cylinder head; a lower cylinder head centering means fixed to the transmission casing and bearing directly or indirectly on the lower hot cylinder head, which allows said cylinder head to move freely relative to the transmission casing a short distance parallel to the longitudinal axis of the cold cylinder, but prevents said cylinder head from moving relative to said casing in a plane perpendicular to said axis; upper cylinder head centering means fixed to a centering gantry which is rigidly fixed to the transmission casing, said means bearing directly or indirectly on the upper hot cylinder head, said means allowing said cylinder head to move freely relative to the transmission casing over a short distance parallel to the longitudinal axis of the cold cylinder but preventing said cylinder head from moving relative to said casing in a plane perpendicular to said axis.

[0079] The reciprocating heat engine with a hot cylinder head and a cold cylinder according to the invention comprises a rod cooling tube which hermetically surrounds the traction rod over all or part of its length, so that a heat transfer liquid coming from a cooling liquid source can circulate in the space left between the inner wall of the tube and the outer surface of the rod, while the largest possible part of the outer surface of the tube does not come into contact with the inner wall of the rod tunnel and defines an empty space together with this latter wall.

[0080] A reciprocating heat engine having a hot cylinder head and a cold cylinder according to the present invention comprises at least one first tube supply orifice communicating with the interior of the rod cooling tube near the first rod end and at least one second tube supply orifice communicating with the interior of the rod cooling tube near the second rod end, and a heat transfer liquid can be circulated between the two orifices.

[0081] The reciprocating heat engine having a high temperature cylinder head and a low temperature cylinder according to the present invention is provided with a rod cooling tube including a tube collar clamped and held directly or indirectly by a traction rod against a fixed lug on the upper high temperature cylinder head or against a transmission casing.

[0082] The reciprocating heat engine having a hot cylinder head and a cold cylinder according to the invention comprises a tube collar clamped and held by a traction rod against a fixed lug by a banjo connection including at least one radial connecting duct, connected on the one hand to a coolant source and on the other hand communicating with the interior of the rod cooling tube.

[0083] The reciprocating heat engine having a hot cylinder head and a cold cylinder according to the invention comprises a thermally insulating riser interposed between the tube collar and the fixed lug, said riser being penetrated in its length by a riser tunnel in which the traction rod and the rod cooling tube which hermetically surrounds it are housed, while the largest possible part of the outer surface of said tube is not in contact with the inner wall of the riser tunnel and defines an empty space together with this latter wall.

[0084] The reciprocating heat engine having a high temperature cylinder head and a low temperature cylinder according to the present invention comprises a rod cooling tube including at least one tube bulge consisting of an axial portion, the free diameter of the tube bulge being substantially equal to or slightly larger than the free diameter of the rod tunnel in which the tube bulge is housed.

[0085] The reciprocating heat engine having a high-temperature cylinder head and a low-temperature cylinder of the present invention is provided with a rod cooling pipe including at least one pipe diameter restriction consisting of an axial portion, the free diameter of the pipe diameter restriction being substantially equal to or slightly smaller than the diameter of the body of the traction rod.

[0086] A reciprocating heat engine having a hot cylinder head and a cold cylinder according to the present invention comprises a traction rod which is hollow to form an internal rod cooling channel along its length, the channel opening axially or radially near each end of the rod while a heat transfer liquid originating from a cooling liquid source can circulate within the channel.

[0087] The reciprocating heat engine with a hot cylinder head and a cold cylinder according to the invention comprises a piston cooling lubrication chamber connected to a source of lubricating cooling fluid, which is fixed to or arranged on or in the centering gantry, while an upper piston rod extending a double-acting piston on the side of the upper variable-volume hot chamber passes through an upper rod orifice provided in the cylinder head and through an access orifice to the cooling lubrication chamber passing through the centering gantry and opening into the piston cooling lubrication chamber, so that the end of the upper piston rod furthest from the piston remains always immersed in the chamber, regardless of the position of the piston.

[0088] The reciprocating heat engine having a hot cylinder head and a cold cylinder according to the present invention is provided with a lubricating cooling fluid that can be circulated from the piston cooling lubrication chamber to the transmission casing by passing sequentially through an upper piston rod internal channel longitudinally provided in the upper piston rod, the internal piston cavity, and a lower piston rod internal channel longitudinally provided in the lower piston rod.

[0089] The reciprocating heat engine having a hot cylinder head and a cold cylinder according to the invention comprises a peripheral portion of an internal piston cavity which communicates with an outer peripheral surface of the piston sealing ring through at least one peripheral ring lubrication orifice opening axially between at least two piston sealing means, said orifice comprising a lubrication means.

[0090] The reciprocating heat engine having a hot cylinder head and a cold cylinder according to the invention comprises a transmission casing covered with a centering and sealing plate pierced with an orifice for access to the power transmission means through which the lower piston rod passes in order to be connected to the power transmission means, said plate being rigidly fixed to said casing.

[0091] A reciprocating heat engine having a hot cylinder head and a cold cylinder according to the present invention is provided with an orifice for access to a cooled lubrication chamber, said orifice including rod sealing means providing sealing between said orifice and an upper piston rod.

[0092] A reciprocating heat engine having a hot cylinder head and a cold cylinder according to the present invention is provided with an orifice for access to a transfer means, said orifice including rod sealing means providing sealing between said orifice and a lower piston rod.

[0093] The reciprocating heat engine with hot cylinder head and cold cylinders according to the invention comprises means for centering the lower cylinder head and / or means for centering the upper cylinder head, which consist of an elastic centering disk which can be drilled centrally with a disk hole through which the lower piston rod or the upper piston rod respectively passes, while the periphery of the elastic centering disk consists of a disk fixing collar which is sealingly fixed to the transmission casing and / or to the centering gantry, respectively.

[0094] The reciprocating heat engine with hot cylinder head and cold cylinders according to the invention comprises a centering and sealing plate carrying a lower cylinder head centering means consisting of an elastic centering disk, the periphery of which forms a disk fixing collar sealingly fixed to said plate, said disk being drilled in its center with a disk hole through which the lower piston rod passes without contacting said disk, the edge of the disk hole carrying a circular contact pad which is maintained in sealing contact with a centering and sealing cone carried by the lower hot cylinder head, which cone may be male or female, the contact between said pad and said cone having the effect of deforming the elastic centering disk axially from its center.

[0095] The reciprocating heat engine having a hot cylinder head and a cold cylinder according to the invention comprises means for centering the upper cylinder head consisting of an elastic centering disk, the periphery of which forms a disk fixing collar sealed and fixed to the centering gantry, said disk being drilled with a disk hole in its center, the edge of the disk hole having a circular contact pad which is maintained in sealing contact with a centering and sealing cone carried by the upper hot cylinder head, said cone may be male or female, the contact between said pad and said cone having the effect of deforming the elastic centering disk axially from its center.

[0096] The reciprocating heat engine with hot cylinder head and cold cylinder according to the invention comprises an anti-rotation connection directly or indirectly connecting the lower hot cylinder head and / or the upper hot cylinder head and / or the cooling cylinder casing to a centering gantry.

[0097] The reciprocating heat engine having a hot cylinder head and a cold cylinder according to the invention comprises a cylinder head application means consisting of at least one cylinder head application screw cooled by a cylinder casing cooling means.

[0098] A reciprocating heat engine having a high-temperature cylinder head and a low-temperature cylinder according to the present invention includes a thermal insulating riser interposed between a screw head of a cylinder head application screw and the high-temperature cylinder head.

[0099] The reciprocating heat engine having a hot cylinder head and a cold cylinder according to the present invention comprises at least one compression spring interposed between the screw head and the insulating riser. [Brief description of the drawings]

[0100] The following description, given by way of non-limiting example and with reference to the accompanying drawings, makes it possible to better understand the invention and to appreciate the characteristics it possesses and the advantages it can offer. [Figure 1] 1 is a schematic cross-sectional view of a reciprocating heat engine having a hot cylinder head and a cold cylinder according to the invention, the valves feeding the hot variable volume chamber of the engine not appearing in the cross-section; [Diagram 2] FIG. 3 is a three-dimensional view of a reciprocating heat engine according to the invention with a hot cylinder head and a cold cylinder, the pistons of which are double-acting and which form an expansion valve, for example, making it possible to implement a regenerative Brayton thermodynamic cycle. [Diagram 3] FIG. 3 is a three-dimensional cross-sectional view of a reciprocating heat engine having a hot cylinder head and a cold cylinder according to the present invention, according to the particular configuration of the engine shown in FIG. 2, in which the double-acting pistons together with the lower and upper hot cylinder heads define a lower variable-volume hot chamber and an upper variable-volume hot chamber. [Figure 4] FIG. 4 is a cross-sectional view of a reciprocating heat engine having a hot cylinder head and a cold cylinder according to the invention, according to the particular configuration of said engine shown in FIGS. 2 and 3. [Diagram 5] FIG. 5 is an enlarged cross-sectional view of a reciprocating heat engine having a hot cylinder head and a cold cylinder according to the present invention, according to the particular configuration of the engine shown in FIGS. 2 to 4, which particularly highlights how the double acting piston is connected to the power transmission means and how sealing between the lower piston rod and the transmission casing is achieved. [Figure 6] FIG. 6 is an enlarged cross-sectional view of a reciprocating heat engine having a hot cylinder head and a cold cylinder according to the present invention, in accordance with the particular configuration of the engine shown in FIGS. 2-5, which particularly highlights how the upper piston rod of the double-acting piston opens into the piston cooling and lubrication chamber, and how sealing between the rod and the centering gantry is achieved. [Figure 7] FIG. 3 is a three-dimensional exploded view of a reciprocating heat engine with a hot cylinder head and a cold cylinder according to the invention, according to the particular configuration of said engine shown in FIG. 2. [Figure 8]FIG. 8 is a partially three-dimensional, partially schematic, cross-sectional view of a portion of a reciprocating heat engine having a hot cylinder head and a cold cylinder according to the invention, according to the particular configuration of said engine shown in FIGS. 2 to 7, the view emphasizing the main parts constituting the retractable pillars and traction rods which form the means for applying the cylinder head of the hot cylinder head against the cold cylinder casing. [Figure 9] FIG. 1 is an enlarged schematic cross-sectional view of a reciprocating heat engine having a hot cylinder head and a cold cylinder according to the present invention, for the particular configuration of the engine as shown in FIGS. 2-8, showing the position and dimensions of the hot crown relative to the double acting piston, and of the upper hot cylinder head relative to the cooled cylinder casing, when the crown and the cylinder head are cold. [Figure 10] FIG. 10 is a schematic cross-sectional view similar to that shown in FIG. 9, showing the position and dimensions of the hot crown of a double-acting piston relative to a cooled cylinder casing, and of the upper hot cylinder head, when said crown and said cylinder head are hot and expand under the influence of temperature. [Figure 11] 3D cutaway view of a reciprocating heat engine according to the invention with a hot cylinder head and a cold cylinder, the pistons of which are double-acting, forming, for example, an expansion valve for implementing a regenerative Brayton thermodynamic cycle, the cooling cylinder casing being directly fixed to the transmission casing, the engine receiving a regenerative hydraulic valve actuator according to the applicant's patent no. 3071896 of October 11, 2019, as well as its hydraulic closing and regenerative motor. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0101] 1 to 10 show a reciprocating heat engine 1 with a hot cylinder head and a cold cylinder according to the invention, various details of its components, its variants and its accessories.

[0102] The reciprocating heat engine 1 having a hot cylinder head and a cold cylinder comprises a cooled cylinder casing 5 provided with at least one cold cylinder 6 in which a piston 2 oriented and / or positioned by piston guide means 29 can translate.

[0103] The piston 2 is connected directly or indirectly to at least one rotating or reciprocating power output shaft 4 by power transmission means 3 housed within a transmission casing 42 .

[0104] The power transmission means 3 may, for example, take the form of a connecting rod 34 hinged around a crank 48 disposed on the crankshaft 35, which may be connected to the piston 2 directly by a piston pin or indirectly by a crosshead 49.

[0105] Said means 3 may also consist of a cam, a transmission hydraulic pump, a linear or rotary generator, or any other transmission means known to a person skilled in the art.

[0106] As can be seen in Figures 1 to 10, the reciprocating heat engine 1 having a high-temperature cylinder head and a low-temperature cylinder according to the present invention is provided with a lubrication means 8 for forming a lubricating film 7 interposed between the low-temperature cylinder 6 and the piston 2, and the means 8 can be made, for example, by spraying the power transmission means 3 in a liquid lubricant contained in the transmission casing 42.

[0107] Figures 1, 3, 4, 9 and 10 clearly show that the reciprocating heat engine 1 with hot cylinder head and cold cylinder according to the invention also comprises cylinder casing cooling means 9, for example consisting of a cooling chamber 27 surrounding the cold cylinder casing 5, while a heat transfer liquid 32 can circulate in said chamber 27, said means 9 cooling the cold cylinder casing 5 in such a way as to maintain all or part of the inner surface of the cold cylinder 6 at a temperature low enough so that the lubricating film 7 does not age prematurely, coke or burn.

[0108] In Figures 1 to 10, the reciprocating heat engine 1 having a high-temperature cylinder head and a low-temperature cylinder according to the present invention is shown to also have at least one high-temperature cylinder head 10 which may include at least one intake valve 31 and at least one exhaust valve 33 controlled by a valve actuator 50.

[0109] The operating temperature of the hot cylinder head 10 is significantly higher than the operating temperature of the cooled cylinder casing 5 which it covers to form, together with the piston 2 , the hot variable volume chamber 11 which contains the working gas 17 .

[0110] As can be easily seen from Figures 9 and 10, the hot cylinder head 10 is, on the one hand, applied and held against the cold cylinder casing 5 by cylinder head application means 24 which allow it to expand freely relative to said cylinder casing 5, and, on the other hand, is positioned against said cylinder casing 5 by cylinder head centering means 39 which may consist, for example, of a centering pin or a bearing collar.

[0111] Furthermore, as shown in Figures 1 and 3 to 10, the reciprocating heat engine 1 having a hot cylinder head and a cold cylinder comprises at least one piston sealing ring 37 provided on the periphery of the piston 2, said ring 37 comprising, on the one hand, a piston sealing means 30 consisting of a compression ring 44 of, for example, cast iron or steel as is usually found on the pistons of conventional automobile engines, forming a seal between the piston 2 and the cold cylinder 6, and, on the other hand, cooled by sealing ring cooling means 38.

[0112] As shown in Figures 1 and 3 to 10, the reciprocating heat engine 1 having a high-temperature cylinder head and a low-temperature cylinder according to the present invention also includes at least one high-temperature crown 19 interposed between the high-temperature variable volume chamber 11 and the piston 2, and the operating temperature of the high-temperature crown is significantly higher than the operating temperature of the cooled cylinder casing 5.

[0113] As Figures 9 and 10 clearly show, the crown 19 is, on the one hand, applied and held against the piston 2 by crown application means 23 which allow the crown 19 to expand freely relative to the piston 2, and, on the other hand, is positioned against the piston 2 by crown centering means 40 which may consist, for example, of a centering pin or a bearing collar.

[0114] In Figures 1, 2 to 7, 9 and 10 it can be seen that the reciprocating heat engine 1 having a hot cylinder head and a cold cylinder according to the invention can be provided with sealed thermal insulation means 12 interposed between the cold cylinder casing 5 and the hot cylinder head 10, said means 12 further being able to form an integral part of the cold cylinder casing 5 and / or of the hot cylinder head 10 according to certain embodiments.

[0115] Similarly, as can be seen particularly in Figures 9 and 10, insulating means 22 may be interposed between the high temperature crown 19 and the piston 2, said means 22 possibly forming an integral part of the high temperature crown 19 and / or of the piston 2.

[0116] In FIG. 1 it is shown that the thermal insulation means 22 may consist of a reflective screen 57 which returns the heat radiating in the direction of the piston 2 to the hot crown 19, in particular in the form of infrared radiation.

[0117] FIG. 1 also shows that the insulating means 22 may consist of a honeycomb or fibrous insulating material 58 occupying all or part of the space between the high temperature crown 19 and the piston 2, which may consist of a low density porous ceramic, as is known per se.

[0118] It should further be noted that in this case the reflective screen 57 can be bonded to the honeycomb or fibrous insulating material 58 so as to form a composite insulating component which, on the one hand, transmits back the heat emitted by radiation from the hot crown 19 and, on the other hand, prevents the transfer of gas between said crown 19 and the piston 2, said transfer being such as to maximize the exchange of heat between these two components 19, 2 by convection forcing.

[0119] Further, it is noted in Figures 1, 3-7, 9 and 10 that the sealed insulation means 12 and / or insulation means 22 may consist of at least one insulation ring 13 made of a material 14 with low thermal conductivity, which may consist primarily of zirconium oxide 15.

[0120] As shown in particular in Figures 1, 9 and 10, the insulating ring 13 forming the sealed insulating means 12 can be in direct or indirect contact with the cooling cylinder casing 5 and / or the high-temperature cylinder head 10 by at least one small surface contact edge 16 that prevents the working gas 17 from passing between the cooling cylinder casing 5 and the high-temperature cylinder head 10.

[0121] As another variant of the reciprocating heat engine 1 with a hot cylinder head and a cold cylinder according to the present invention, particularly seen in Figures 1, 9 and 10, the insulating ring 13 forming the insulating means 22 can also be in direct or indirect contact with the hot crown 19 and / or the piston 2 by at least one small surface contact edge 16, which prevents the working gas 17 from passing between the hot crown 19 and the piston 2.

[0122] It should also be noted in Figures 1, 9 and 10 that a cylinder head seal 18 can be interposed between the insulating ring 13 forming the sealed insulating means 12 and the cooled cylinder case 5 and / or between said ring 13 and the high temperature cylinder head 10.

[0123] Similarly, a piston sealing seal 36 may be interposed between the insulating ring 13 forming the thermal insulation means 22 and the high temperature crown 19 and / or between said ring 13 and the piston 2 .

[0124] It should be noted that the cylinder head seal 18 and / or piston seal 36 may comprise multiple metal sheets, as is the case for example with cylinder head gaskets in modern automotive internal combustion engines, or may be made of a material that can withstand high temperatures, such as the "Therma-pur" material developed by "Garlock".

[0125] It should also be noted that the high temperature cylinder head 10 and / or the high temperature crown 19 may be comprised, in whole or in part, of a material 20 that is resistant to high temperatures, which may consist primarily of silicon carbide 21.

[0126] According to a variant of the hot cylinder head and cold cylinder 1 of the reciprocating heat engine according to the invention, which can be seen in particular in Figures 9 and 10, the hot cylinder head 10 can have a concave conical cylinder head surface 25, whereby said cylinder head 10 is applied and held by the cylinder head application means 24 against a circular cylinder contact edge 51 provided on the cooling cylinder casing 5.

[0127] In this case, the angle of the concave cone formed by the surface 25 is such that when the surface 25 slides over the edge 51 due to the difference between the thermal expansion of the cylinder head 10 and the thermal expansion of the cylinder casing 5, the axial distance separating the bearing point of the cylinder head application means 24 on the hot cylinder head 10 from the cold cylinder casing 5 remains approximately constant, all other conditions being equal, while the concave conical surface of the cylinder head 25 and the circular cylinder edge contact portion 51 form a cylinder head centering means 39.

[0128] It should be noted that this particular configuration of the reciprocating heat engine 1 with hot cylinder head and cold cylinders according to the invention makes it possible to maintain the forces experienced by the cylinder head application means 24 approximately constant, whatever the difference between the thermal expansion of the hot cylinder head 10 and that of the cold cylinder casing 5, said difference resulting from both the possibly different temperatures and thermal expansion coefficients between those of the hot cylinder head 10 and those of the cold cylinder casing 5.

[0129] Moreover, the arrangement makes it possible to limit the variation of the volume ratio of a reciprocating heat engine 1 having a hot cylinder head and a cold cylinder as a function of its temperature, in particular during the cold start phase of the engine 1 .

[0130] It should be noted that advantageously, the circular cylinder contact edge 51 can have a spherical contact with the cylinder head concave conical surface 25 .

[0131] As another variant of the reciprocating heat engine 1 with a hot cylinder head and a cold cylinder according to the invention, particularly seen in Figures 9 and 10, the hot crown 19 can also have a concave conical crown surface 26, whereby said crown 19 is applied and held by a crown application means 23 against a piston circular contact edge 52 formed on the piston 2.

[0132] In this case, the angle of the concave cone forming the surface 26 is such that when the surface 26 slides over the edge 52 due to the difference between the thermal expansion of the crown 19 and the piston 2, the axial distance separating the bearing point of the crown application means 23 on the high temperature crown 19 from the piston 2 remains approximately constant, all other conditions being equal, while the concave conical surface of the crown 26 and the piston circular contact edge 52 form the crown centering means 40.

[0133] It should be noted that this particular configuration of the reciprocating heat engine 1 with hot cylinder head and cold cylinder according to the invention makes it possible to keep the force experienced by the crown application means 23 approximately constant, regardless of the difference between the thermal expansion of the hot crown 19 and the thermal expansion of the piston 2.

[0134] Moreover, the arrangement makes it possible to limit the variation of the volume ratio of a reciprocating heat engine 1 having a hot cylinder head and a cold cylinder as a function of its temperature, in particular during the cold start phase of the engine 1 .

[0135] It should be noted that, advantageously, the piston circular contact edge 52 may have a spherical contact with the concave conical crown surface 26 .

[0136] As shown in FIG. 1, in a variant embodiment of the reciprocating heat engine 1 with a hot cylinder head and a cold cylinder according to the invention, the hot crown 19 can have an aerodynamic passivation bead 53 at its periphery, which limits the turbulence of the working gas 17 in the vicinity of the cold cylinder 6 and, as a consequence, on the one hand, the convection forces that increase the loss of heat of said gas 17 by heat transfer to said cold cylinder 6.

[0137] FIG. 1 also shows that the outside of the cylinder head 10 may be covered with insulation 41 that prevents heat from the hot cylinder head 10 from dissipating into the environment of a reciprocating heat engine 1 having a hot cylinder head and a cold cylinder according to the present invention.

[0138] The insulation 41 can consist, for example, of several layers of thin metal sheets containing spikes that leave air blades between each sheet, or it can be any other insulation material 41 known to those skilled in the art.

[0139] In Figures 1, 2 to 7, 9 and 10 it can be seen that the piston sealing ring 37 can have a piston guide means 29 consisting of an annular sliding surface 43 having a barrel shape in contact with the low-temperature cylinder 6, which shape can be positioned between two compression segments 44 and adjacent to the oil scraper segment 45.

[0140] According to the particular configuration of the reciprocating heat engine 1 with hot cylinder head and cold cylinder according to the present invention shown in Figures 2 to 10, the cooled cylinder casing 5 can be clamped and held between the lower hot cylinder head 10 and the upper hot cylinder head 10 by the cylinder head application means 24, while the piston 2 is double-acting and includes, on the one hand, a lower piston rod 46 connecting the piston 2 to the power transmission means 3 and penetrating the lower hot cylinder head 10 via a lower rod orifice 47, and, on the other hand, a lower high temperature crown 19 and an upper high temperature crown 19 to define, together with the lower and upper high temperature cylinder heads 10, a lower variable volume high temperature chamber 11 and an upper variable volume high temperature chamber 11.

[0141] Further according to this particular configuration, the reciprocating heat engine 1 with a hot cylinder head and a cold cylinder according to the present invention comprises at least one receding pillar 101, which may be either completely closed or perforated, through which a rod tunnel 102 passes in the longitudinal direction from one side to the other.

[0142] In this case, a first pillar end 103 of the rearward-recessed pillar 101 is mounted directly or indirectly on the transmission casing 42, while a second pillar end 104 of the pillar 101 supports the lower high-temperature cylinder head 10, and the first end 101 is capable of pivoting about a ball joint 105 and / or bending relative to the casing 42, while the second end 104 is capable of pivoting about a ball joint 105 and / or bending relative to the lower high-temperature cylinder head 10.

[0143] It should be noted that the pivoting of said ends 103, 104 can be achieved by means of a pivot or cardan type mechanical connection or ball joint 105, or by bending all or part of the retractable pillar 101, or both.

[0144] According to a particular embodiment of the reciprocating heat engine 1 with a hot cylinder head and a cold cylinder according to the invention, the receding pillars 101 can be made of zirconium dioxide, also known as "zirconia", which offers good mechanical strength at high temperatures, low thermal conductivity, and a coefficient of expansion close to that of steel.

[0145] Furthermore, in this case, at least one traction rod 106 forms the cylinder head application means 24, said rod 106 being at least partially housed in the rod tunnel 102, said first rod end 107 of said rod 106 being fixed directly or indirectly to the transmission casing 42, while said second rod end 108 of said rod 106 is fixed directly or indirectly to the upper high-temperature cylinder head 10, said first end 107 being able to pivot about a ball joint 105 and / or bend relative to said casing 42, while said second end 108 being able to pivot about a ball joint 105 and / or bend relative to said cylinder head 10, said ends 107, 108 therefore being able to pivot by a pivot or cardan type mechanical connection or by the ball joint 105, or by bending all or part of the traction rod 106, or by both.

[0146] As shown in FIG. 8, for fixing to the upper high-temperature cylinder head 10, the second end of the rod 19 can pass through a lug orifice 144 consisting of a fixing lug 117 of the cylinder head 10, while it can be seen that either a rod head 145 or a rod nut 147 screwed onto a rod thread 146 provided on the traction rod 106 bears against the lug 117.

[0147] Additionally, in FIG. 8 , it is noted that the first rod end 107 may also be secured to the transmission casing 42 by a rod head 145 or a rod nut 147 threaded onto the rod threads 146 .

[0148] Alternatively, the rod threads 146 may be threaded into tappings made directly or indirectly in the transmission casing 42 .

[0149] According to a particular embodiment of the double-acting expansion cylinder 1 according to the invention, a compression spring 148 can be interposed either between the rod head 145 or the rod nut 147 and the fixed lug 117, or between said head 145 or any other threaded part into which the rod thread 146 is screwed and any other bearing part.

[0150] As shown in FIG. 8, the spring 148 may consist of one or more "Belleville" washers.

[0151] Such a spring 148 can in particular limit the tension forces to which the traction rod 106 is subjected when the various members which it clamps together and which it holds expand under the effect of their increased temperature.

[0152] Even in the case shown in Figures 2 to 10, in which the cooled cylinder casing 5 is clamped and held between a lower hot cylinder head 10 and an upper hot cylinder head 10, while the pistons 2 are double-acting, the reciprocating heat engine 1 with hot cylinder head and cold cylinders according to the present invention comprises lower cylinder head centering means 109 fixed to the transmission casing 42 and supported directly or indirectly on the lower hot cylinder head 10, which allow the cylinder head 10 to move freely relative to the transmission casing 42 over a short distance parallel to the longitudinal axis of the cold cylinders 6, but prevent the cylinder head 10 from moving relative to the casing 42 in a plane perpendicular to said axis.

[0153] Similarly, an upper cylinder head centering means 110 fixed to a centering gantry 127 rigidly fixed to the transmission casing 42 is directly or indirectly supported on the upper hot cylinder head 10, said means 109 allowing said cylinder head 10 to move freely relative to the transmission casing 42 a short distance parallel to the longitudinal axis of the cold cylinder 6, but preventing said cylinder head 10 from moving relative to said casing 42 in a plane perpendicular to said axis.

[0154] In this case, as can be seen in Figures 2, 3, 7 and 8, a rod cooling tube 111 can hermetically surround the traction rod 106 over all or part of its length, and heat transfer liquid 32 coming from a cooling liquid source 113 can circulate in the space left between the inner wall of the tube 111 and the outer surface of the rod 106, while the largest possible part of the outer surface of the tube 111 does not contact the inner wall of the rod tunnel 102, thereby defining a space that is empty or filled with air, or filled with any type of gas.

[0155] Thus, the heat transfer liquid 32 can cool the traction rod 106 and maintain it at a temperature low enough so that the constituent material of the rod 106 retains its best mechanical characteristics, while the empty space left between the outer surface of the rod cooling tube 111 and the inner wall of the rod tunnel 102 limits the cooling of the receding pillar 101.

[0156] It should be noted that according to a particular embodiment of the reciprocating heat engine 1 having a high-temperature cylinder head and a low-temperature cylinder according to the present invention, only the rod head 145 that the traction rod 106 may have can be cooled, said head 145 being in direct or indirect contact with the upper high-temperature cylinder head 10.

[0157] As clearly shown in FIG. 8, at least one first tube supply orifice 114 can be in communication with the interior of the rod cooling tube 111 near the first rod end 107 and at least one second tube supply orifice 115 can be in communication with the interior of the rod cooling tube 111 near the second rod end 108, and the heat transfer liquid 32 can circulate between the two orifices 114, 115, the liquid 32 being at a lower temperature when it enters the rod cooling tube 111 than when it leaves it.

[0158] It should be noted that a fluid pump can be provided to forcefully circulate the heat transfer liquid 32 within the rod cooling tube 111, and the pump can continue to operate for a certain period of time after the thermal machine to which the reciprocating heat engine 1 having a high-temperature cylinder head and a low-temperature cylinder according to the present invention is applied has been stopped.

[0159] This latter configuration allows, for example, the lower and upper hot cylinder heads 10 to shed heat that can continue to be transferred to the traction rod 106 during their cooling.

[0160] It should be noted that upon removal from the rod cooling tubes 111 , the heat transfer liquid 32 may be cooled or refreshed by a heat exchanger before being reintroduced into the tubes 111 .

[0161] In FIG. 8, it should be noted that the rod cooling tube 111 may include a tube collar 116 that is clamped and held against a fixed lug 117 on the upper high temperature cylinder head 10 or against the transmission casing 42, directly or indirectly by a traction rod 106.

[0162] In this regard, the tube collar 116 can be clamped and held by the traction rod 106 against the fixed lug 117 by a banjo connection 118 which includes at least one radial connection duct 119 connected on the one hand to the coolant source 113 and communicating with the interior of the rod cooling tube 111 on the other hand.

[0163] It should be noted that the radial connecting duct 119 can be connected to the coolant source 113 or to other radial connecting ducts 119 that the banjo connection 118 includes for other rod cooling tubes 111 by flexible or deformable ducts that can adapt to the variations in distance caused by the thermal expansion of the various components that make up the reciprocating heat engine 1 with a hot cylinder head and a cold cylinder according to the present invention.

[0164] Further in this regard, as shown in FIG. 8, an insulating riser 120 can be interposed between the tube collar 116 and the fixed lug 117, said riser 120 being penetrated in its length by a riser tunnel 121 in which the traction rod 106 and the rod cooling tube 111 sealingly surrounding it are housed, while the largest possible part of the outer surface of said tube 111 does not contact the inner wall of the riser tunnel 121 and defines together with this latter wall a space that is empty or filled with atmosphere, or filled with any kind of gas.

[0165] It should be noted that the insulating riser 120 may be advantageously made from a material that is resistant to high temperatures and provides low thermal conductivity, such as zirconium dioxide.

[0166] FIG. 8 also shows that according to a variant of the embodiment of the reciprocating heat engine 1 with a hot cylinder head and a cold cylinder according to the invention, the rod cooling tube 111 may include at least one tube bulge 122 consisting of an axial portion of the tube 111, the free diameter of which is substantially equal to or slightly larger than the free diameter of the rod tunnel 102 in which it is housed, thereby making it possible to center the tube 111 in the tunnel 102 or even to perform local sealing between the tube 111 and the tunnel 102.

[0167] Conversely, the rod cooling tube 111 may include at least one tube diameter restriction 123 consisting of an axial portion of the tube 111, the free diameter of which is substantially equal to or slightly smaller than the diameter of the body of the traction rod 106, thereby allowing the tube 111 to be centered around the rod 106 or even allowing local sealing to be performed between the tube 111 and the rod 106.

[0168] Alternatively or additionally, as clearly shown in FIG. 8, it should be noted that the rod cooling tube 111 can receive at least one elastomer or plastic tube seal 157 to improve the sealing formed between the tube 111 and the rod tunnel 102.

[0169] As a variant not shown, the traction rod 106 can be hollow so as to form internal rod cooling channels along the length of the rod 106, which open axially or radially near each end of the rod 106, while a heat transfer liquid 32 coming from a cooling liquid source 113 can circulate within the channels, thereby cooling the traction rod 106 and maintaining it at a sufficiently low temperature so that the material of which the rod 106 is made retains its best mechanical characteristics.

[0170] As shown in Figures 4, 6 and 7, a piston cooling lubrication chamber 125 connected to a lubrication cooling fluid source 126 can be fixed to the centering gantry 127 or made on or in it, while an upper piston rod 128 extending the double-acting piston 2 on the side of the upper variable volume high temperature chamber 11 passes through the upper high temperature cylinder head 10 through an upper rod orifice 129 provided in the upper rod orifice 129 and through an access orifice 130 to the cooling lubrication chamber which passes through the centering gantry 127 and opens into the piston cooling lubrication chamber 125, so that the end of the upper piston rod 128 farthest from the piston 2 remains always immersed in the chamber 128, regardless of the position of the piston 2.

[0171] In this case, lubrication cooling fluid 139 can be circulated from the piston cooling lubrication chamber 125 to the transmission casing 42 by sequentially passing through an upper piston rod internal channel 140 longitudinally provided in the upper piston rod 128, an internal piston cavity 141, and a lower piston rod internal channel 142 longitudinally provided in the lower piston rod 46.

[0172] As can be seen in Figures 3, 9 and 10, the periphery of the internal piston cavity 141 can communicate with the outer circumferential surface of the piston sealing ring 37 through at least one peripheral ring lubrication orifice 143 opening axially between at least two piston sealing means 30, said orifice 143 being comprised of the lubrication means 8 and the sealing ring cooling means 38.

[0173] FIG. 5 shows that the transmission casing 42 can be covered with a centering and sealing plate 131 drilled with an orifice 132 for access to the power transmission means 3 through which the lower piston rod 46 passes to be connected to the transmission means, said plate 131 being rigidly fixed to said casing 42 by screws or by any other means known to the person skilled in the art.

[0174] Alternatively, the plate 131 may form an integral part of the casing 42 .

[0175] As shown in FIG. 6, the access orifice 130 to the cooling and lubrication chamber may include a rod sealing means 133 that provides sealing between the orifice 130 and the upper piston rod 128 .

[0176] FIG. 5 shows that the access orifice 132 to the transmission means may include rod sealing means 133 providing sealing between said orifice 132 and the lower piston rod 46 .

[0177] It should be noted that in Figures 5 and 6 the lower cylinder head centering means 109 and / or the upper cylinder head centering means 110 can consist of an elastic centering disk 134 which can be drilled at its centre with a disk hole 135 through which the lower piston rod 46 or the upper piston rod 128, respectively, passes, whilst the periphery of the elastic centering disk 134 consists of a disk fixing collar 136 which is sealingly fixed to the transmission casing 42 and / or to the centering gantry 127, respectively.

[0178] It will be noted in FIG. 5 that the centering and sealing plate 131 can carry the lower cylinder head centering means 109 consisting of a resilient centering disc 134, the periphery of which forms a disc fixing collar 136 sealingly fixed to said plate 131, said disc 134 being drilled in its centre with a disc hole 135 through which the lower piston rod 46 passes without contacting said disc 134, the edge of which has a circular contact pad 137 held in sealing contact with a centering and sealing cone 138 carried by the lower high-temperature cylinder head 10, which cone 138 may be male or female, the contact between said pad 137 and said cone 138 having the effect of deforming the resilient centering disc 134 axially from its centre.

[0179] It should be noted that the disk fixing collar 136 may be fixed to the centering and sealing plate 131 by at least one screw, clip, or any other fixing means known to those skilled in the art.

[0180] It should be noted that the resilient centering disk 134 may advantageously be made from a material that is resistant to high temperatures and provides low thermal conductivity, such as zirconium dioxide.

[0181] As shown in FIG. 6, the upper cylinder head centering means 110 may consist of an elastic centering disk 134, the periphery of which forms a disk fixing collar 136 sealingly fixed to the centering gantry 127, said disk 134 being drilled with a disk hole 135 in its center, the edge of which provides a circular contact pad 137 held in sealing contact with a centering and sealing cone 138 of the upper high-temperature cylinder head 10, which may be male or female, the contact between said pad 137 and said cone 138 having the effect of deforming the elastic centering disk 134 axially from its center.

[0182] It should be noted that the disk fixing collar 136 may be fixed to the centering gantry 127 by at least one screw, clip, or any other fixing means known to one skilled in the art.

[0183] It should be noted that when the double-acting piston 2 is extended by the upper piston rod 128 , the upper piston rod passes through the disk hole 135 without contacting the elastic centering disk 134 .

[0184] Additionally, it is noted that the resilient centering disk 134 may advantageously be made from a material that is resistant to high temperatures and provides low thermal conductivity, such as zirconium dioxide.

[0185] It should also be noted that, instead of what has been described above, whether it is the lower cylinder head centering means 109 or the upper cylinder head centering means 110, contact pads similar to those of the disk holes 135 can be provided on the lower high-temperature cylinder head 10 or on the upper high-temperature cylinder head 10, respectively, while centering and sealing cones similar to those of the cylinder head 10 are provided on or in the elastic centering disk 134.

[0186] It should be noted that the centering and sealing functions provided by the elastic centering disk 134 can be assigned, for example, to a split or non-split torus made of steel or superalloy, to an expandable washer made of the same piece of metal or ceramic, composed or not composed of multiple radially stacked folds, to at least three needles pressed by a spring and distributed every 120 degrees and engaging with sealing segments, and in general to any solution capable of ensuring centering and sealing under the desired functional conditions while limiting heat loss from any hot component to any cold component.

[0187] As shown in Figures 2 and 7, an anti-rotation connection 149 can directly or indirectly connect the lower high-temperature cylinder head 10 and / or the upper high-temperature cylinder head 10 and / or the cooling cylinder casing 5 to the centering gantry 127, and the connection 149 can consist of, for example, a pin or a connecting rod, and prevents the assembly formed by the cylinder head 10 and the cooling cylinder casing 5 from rotating around the longitudinal axis of the low-temperature cylinder 6.

[0188] It should be noted in FIG. 11 that according to the reciprocating heat engine having a high temperature cylinder head and a low temperature cylinder of the present invention, the cylinder head application means 24 can consist of at least one cylinder head application screw 59 cooled by the cylinder casing cooling means 9, which screw 59 can also consist of a stud engaging with a nut.

[0189] According to this particular configuration of the invention, an insulating riser 120 may be interposed between the screw head 60 of the cylinder head application screw 59 and the high temperature cylinder head 10, the riser 120 may be comprised of a quartz or "zirconia" tube surrounding the body of the cylinder head application screw 59.

[0190] In this case, at least one compression spring 148 may be interposed between the screw head 60 and the insulating riser 120, which may be a "Belleville" type washer, as is known per se, as shown in FIG. 11.

[0191] Operation of the invention The operation of the reciprocating heat engine 1 having a high-temperature cylinder head and a low-temperature cylinder according to the present invention can be easily understood with reference to FIGS.

[0192] The engine 1 may be equipped with a single acting piston 2 as shown in Figure 1, or a double acting piston 2 as shown in Figures 2 to 11. The engine may implement the Beau de Rochat, Miller, Atkinson, Diesel cycle, or any other thermodynamic cycle known to those skilled in the art.

[0193] In the particular embodiment of a reciprocating heat engine 1 with a hot cylinder head and a cold cylinder according to the invention shown in Figures 2 to 11, in which the piston 2 is a double-acting piston, the engine 1 performs a regenerative Brayton cycle identical to the regenerative Brayton cycle implemented by the transfer-expansion and regenerative heat engine according to WO2016120560.

[0194] In this particular situation, the present invention applies only to the expansion valve 28 of the engine 1; other components of the engine 1, such as one or more compressors, combustors, or regenerative exchangers required to implement a regenerative Brayton cycle, are not shown.

[0195] The objective of the reciprocating heat engine 1 with a hot cylinder head and a cold cylinder according to the present invention is to limit heat loss of the working gas 17 as much as possible by making the inner wall surface of the expansion valve 28 as hot as possible, while at the same time enabling the piston 2 to achieve sealing with the cold cylinder 6 by utilizing conventional piston sealing means 30, in particular a compression segment 44 and an oil scraper segment 45 similar to those installed in mass-produced automotive internal combustion engines.

[0196] It will be noted, particularly in Figures 1, 3, 4 and 11, that according to the particular example of embodiment of the reciprocating heat engine 1 with a hot cylinder head and a cold cylinder according to the invention described therein, power transmission means 3 housed in a transmission casing 42 are provided for converting the reciprocating motion performed by the double-acting piston 2 in the cold cylinder 6 into a continuous rotational motion of the crankshaft 35.

[0197] According to this non-limiting example of a particular embodiment of the engine 1 according to the invention, the transmission casing 42 and the power transmitting means 3 are maintained at a temperature close to 100 degrees Celsius.

[0198] 3, 4 and 11, as an example of an embodiment of a reciprocating heat engine 1 with a hot cylinder head and a cold cylinder according to the invention, it should be noted that in this case the power transmission means 3 advantageously consists of a connecting rod 34 connected to the double-acting piston 2 by a crosshead 49 itself connected to said double-acting piston 2 by a lower piston rod 46, said connecting rod 34 being hinged around a crank 48 provided on a crankshaft 35, which forms the power output shaft 4, as shown in FIGS. 3 and 4.

[0199] As can be clearly seen in Figures 3 and 4 as well as Figures 5 and 6, the reciprocating heat engine 1 with high-temperature cylinder head and low-temperature cylinder according to the present invention presented in this case has, for the same low-temperature cylinder 6, a lower high-temperature cylinder head 10 which, together with the double-acting piston 2, forms a lower variable-volume high-temperature chamber 11, and an upper high-temperature cylinder head 10 which, together with the piston 2, forms an upper variable-volume high-temperature chamber 11.

[0200] As can be seen from Figures 3, 4 and 11, the cooled cylinder casing 5 is axially clamped and held between a lower high-temperature cylinder head 10 and an upper high-temperature cylinder head 10, while the double-acting piston 2 receives a high-temperature crown 19 on each of its lower and upper axial faces, which crowns 19 are interposed between the pistons 2 and the variable volume high-temperature chamber 11 which they engage.

[0201] In this case, the working gas 17 is admitted to the expansion valve 28 through the intake valve 31 at a temperature of 1300 degrees Celsius, while the operating equilibrium temperature of the hot cylinder head 10 and hot crown 19 is assumed to be 950 degrees Celsius.

[0202] Advantageously, the intake valve 31 and the exhaust valve 33 through which the working gas 17 is discharged after expanding in the expansion valve 28 are autoclaved and may each be controlled by a regenerative hydraulic valve actuator 50 as described in Patent No. 3,071,896, dated October 11, 2019, belonging to the present applicant.

[0203] Note in FIG. 11 that the actuator accepts an input / output microaccumulator 162 in addition to that provided in Patent No. 3,071,896.

[0204] The particular location of the hydraulic lock-out and regeneration motor 161 is also shown in FIG.

[0205] Also shown in FIG. 11 is the presence of a solenoid valve block 163 arranged on the side of the reciprocating heat engine 1 having a hot cylinder head and a cold cylinder, said block 163 housing a preload valve as required for the operation of the intake hydraulic valve actuator 50 included in the two expansion valves of the engine 1 according to FIG. 11, said valve being provided in Patent No. 3,071,896 for said actuator 50.

[0206] Unlike the heat engine with transfer-expansion and regeneration according to WO2016120560, in which all inner walls are maintained at a high temperature of, for example, 950 degrees Celsius, the inner walls of the cold cylinder 6 of the expansion valve 28 of the heat engine 1 according to the invention are in this case maintained by the cylinder casing cooling means 9 at a relatively low temperature of only 100 degrees Celsius, this temperature being given by way of example only.

[0207] Figures 1, 3, 4, 9, 10 and 11 show that the cylinder casing cooling means 9 may consist of a cooling chamber 27 surrounding the outer surface of the low-temperature cylinder 6, within which a heat transfer liquid 32, in this case water, circulates.

[0208] Thus, as clearly shown in Figures 3, 6, 9, 10 and 11, virtually all of the inner walls of the expansion valve 28 of the reciprocating heat engine 1 having a high temperature cylinder head and a low temperature cylinder according to the present invention remain at high temperature, except for the low temperature cylinder 6, similar to that of the transfer-expansion and regenerative heat engine according to WO2016120560.

[0209] In this regard, it is further noted that in order to avoid heat losses, the expansion valve 28 shown in Figures 2, 3, 4, 7 and 11 includes a hinged intake plenum 159 and a hinged exhaust plenum 159 which can be made of silicon carbide 21, said plenums 159 being provided in accordance with the principles of French Patent No. 3094416, published on March 5, 2021, belonging to the present applicant.

[0210] In this regard, Figures 2 to 4 and 11 clearly show that the plenum 159 is applied and held, on the one hand, against the lower or upper high-temperature cylinder head 10, as the case may be, and, on the other hand, against the gas collector by an elastic plenum flange 158 which is clamped and held by screws and an elastic plenum flange spring 56.

[0211] This particular configuration allows the plenum 159, which provides a spherical bearing surface for the high temperature cylinder head 10 and manifold, to pivot freely around the cylinder head 10 and the manifold to allow the components of the reciprocating heat engine 1 having a high temperature cylinder head and low temperature cylinders according to the present invention to expand.

[0212] Similarly, in Figures 2, 3, 4, 7 and 11, in a reciprocating heat engine 1 having a hot cylinder head and a cold cylinder according to the present invention, according to a non-limiting exemplary embodiment, it is noted that the valve actuator 50 is applied and held against the hinged plenum 159 it engages by an elastic actuator flange 54 and by an elastic actuator flange spring 55 in the case of the actuator 50 controlling the intake valve 31 and exhaust valve 33 of the upper variable volume hot chamber 11, and by an elastic actuator pusher 160 in the case of the actuator 50 controlling the intake valve 31 and exhaust valve 33 of the lower variable volume hot chamber 11.

[0213] Further, note that the elastic actuator pusher 160 is telescoping and is pressurized by a nut pressing against a "Belleville" washer. In this regard, the force generated by the pusher 160 is adjustable.

[0214] As mentioned above, if virtually all of the inner walls of the expansion valve 28 remain hot, except for the cold cylinder 6, the remaining hot surface is sufficient to obtain a thermodynamic efficiency of the regenerative Brayton cycle that is actually significantly higher than the thermodynamic efficiencies of the Otto and Diesel cycles.

[0215] It should be noted in Figures 3, 4, 9, 10 and 11 that the piston guiding means 29 and the piston sealing means 30 of the piston 2 are also maintained at a temperature close to the temperature of the low temperature cylinder 6, in particular at about 100 degrees Celsius, in order to preserve the integrity of the lubricating film 7 covering the inner wall of said cylinder 6.

[0216] It is therefore understood that, unlike the transmission-expansion and regenerative heat engine of WO2016120560, the piston sealing means 30 no longer consists of the fluid cushion sealing device of FR3032252, but rather is constituted by sealing segments comparable to those of conventional automotive internal combustion engines, said means 30 being cooled and lubricated in the same way.

[0217] This similarity allows the reciprocating heat engine 1 with hot cylinder head and cold cylinder according to the invention to benefit from over 100 years of knowledge in the field of segmenting pistons in internal combustion engines.

[0218] The particular configuration of the engine 1 is justified in that, under the temperature conditions just described, the heat given to the cold cylinder 6 by the working gas 17 forms an energy loss comparable to or even smaller than the energy loss caused, on the one hand, by the fluid cushion sealing device, the subject of French patent No. 3 032 252, due to the compression means necessary for it to supply compressed air, and, on the other hand, by the regenerative cooling system according to European patent No. 3 585 993, due to the additional pressure loss at the exhaust which it generates, the efficiency of the regenerative heat exchanger being less than 1 due to the reintroduction into the thermodynamic cycle of the heat extracted from the inner wall of the expansion valve via the regenerative heat exchanger.

[0219] As proof of the effectiveness of the reciprocating heat engine 1 having a hot cylinder head and a cold cylinder according to the present invention, it should be noted that if all of the inner walls of the expansion valve 28 shown in Figures 3-7 and 9-11 (including the lower and upper cylinder heads 10 and the hot crown 19) were maintained at only 100 degrees Celsius, like the inner walls of a mass-produced automotive internal combustion engine, the average surface specific heat power (expressed, for example, in kilowatts per square meter) delivered by the working gas 17 to the cold cylinder 6 would be much lower than the average surface specific heat power delivered by the gas 17 to the hot cylinder head 10 and the hot crown 19.

[0220] Indeed, in contrast to the hot cylinder head 10 and hot crown 19, whose surface exposed to the working gas 17 remains constant, the surface exposed by the cold cylinder 6 to the working gas 17 is small at the beginning of the expansion of the gas 17 and then increases as the gas 17 expands and its temperature decreases.

[0221] Thus, assuming the cylinder head 10 and crown 19 are intentionally maintained at 100 degrees Celsius during expansion, the specific cooling power at the surface will be much lower on the inner walls of the cold cylinder 6 than on the inner walls of the cylinder head 10 and crown 19.

[0222] Furthermore, in accordance with the particular configuration of reciprocating heat engine 1 having a hot cylinder head and a cold cylinder shown in Figures 2-11, the piston 2 is double acting rather than single acting, which minimizes the surface of the cold cylinder 6 relative to the combined surfaces of the hot cylinder head 10 and the hot crown 19.

[0223] In fact, since the cold cylinder 6 is common to the lower and upper variable volume hot chambers 11 , its surface in this case represents less than 30 percent of the total internal surface of the expansion valve 28 in contact with the working gas 17 .

[0224] It is also observed that, at the same maximum power output, a reciprocating heat engine 1 having a high temperature cylinder head and a low temperature cylinder according to the present invention is equipped with a double acting piston 2 as shown in Figures 2 to 7 and 9 to 11 and performs a regenerative Brayton cycle, and the inner surface of the low temperature cylinder 6 is smaller than the inner surface of the cylinder of a conventional Otto or Diesel cycle engine.

[0225] This reduces the relative heat loss due to the cold cylinder 6 .

[0226] In addition, the maximum temperature reached by the gases in the cylinders of a conventional Otto or Diesel cycle engine is about 2500 degrees Celsius, compared to only about 1300 degrees Celsius for a reciprocating heat engine 1 having a hot cylinder head and a cold cylinder running a regenerative Brayton cycle.

[0227] All other things being equal, this lower temperature further reduces the heat loss of the working gas 17 in contact with the cold cylinder 6 .

[0228] It should further be noted that, unlike the hot cylinder head 10 and the hot crown 19, the cold cylinder 6 of the reciprocating heat engine 1 having a hot cylinder head and a cold cylinder according to the present invention is located in a low turbulence zone of the working gas 17 during the introduction of said gas 17 into either of the variable volume hot chambers 11 via the corresponding intake valve 31 or during the exhaust of said gas 17 from said chamber 11 via the exhaust valve 33.

[0229] This low intensity turbulence limits convective forcing and heat transfer by the working gas 17 to the cold cylinder 6 .

[0230] Further, it should be noted that, unlike conventional Otto or Diesel cycle engines, the turbulent flow of gases entering the expansion valve 28 does not need to be forced by motions known to those skilled in the art as "tumble," "swirl," or "squish" in order to promote any combustion.

[0231] Indeed, insofar as the reciprocating heat engine 1 with hot cylinder head and cold cylinder according to the present invention performs its primary purpose of the regenerative Brayton cycle, the combustion or heating of the working gas 17 is achieved not within the expansion valve 28 but by a heat source located upstream of the expansion valve 28, which may consist of a combustor, a heat exchanger or, as a non-limiting example, a solar radiation concentration sensor.

[0232] Thus, the lack of need to create spontaneous turbulence to promote combustion further reduces the heat losses of the reciprocating heat engine 1 having a hot cylinder head and a cold cylinder according to the present invention implementing a regenerative Brayton cycle relative to the heat losses of a conventional Otto or Diesel cycle engine due to the smaller convection forcing between the working gas 17 and the inner wall of the cold cylinder 6.

[0233] However, it will be appreciated that to benefit from the advantages of a reciprocating heat engine 1 having a high temperature cylinder head and a low temperature cylinder, the engine 1 involves engaging high temperature and low temperature components that are only a few millimeters apart.

[0234] In order to demonstrate how the reciprocating heat engine 1 with hot cylinder head and cold cylinder according to the invention allows this engagement of hot and cold parts in close proximity to each other, it is assumed in this case that the cooled cylinder casing 5 is made of cast iron, while the hot cylinder head 10 and the hot crown 19 are made of silicon carbide 21 and the body of the piston 2 itself is made of steel with high mechanical characteristics.

[0235] It is recalled that silicon carbide 21 retains its mechanical characteristics up to temperatures of about 1400 degrees Celsius and can be used in oxidizing media up to these high temperatures.

[0236] Also in this case it is assumed that the inside diameter of the low-temperature cylinder 6 is equal to 240 millimeters.

[0237] The close proximity of hot and cold components presents a dual challenge in terms of differential expansion and in terms of limiting heat loss.

[0238] For example, this is the case for the upper hot cylinder head 10 of a reciprocating heat engine 1 having a hot cylinder head and a cold cylinder according to the invention, according to the particular configuration shown in Figures 2 to 11 .

[0239] The hot cylinder head 10 and the cold cylinder 6 it mates with are both manufactured at a temperature of approximately 20 degrees Celsius.

[0240] However, during operation, the temperature of the cold cylinder 6 stabilizes at 100 degrees Celsius, while the temperature of the hot crown 10 stabilizes at 950 degrees Celsius.

[0241] Taking into account the expansion coefficients of the materials of construction of the hot cylinder head 10 and the cold cylinder 6, these temperatures result in a high temperature diameter difference of approximately one millimeter between the high temperature diameter of the hot cylinder head 10 and the high temperature diameter of the cold cylinder 6.

[0242] Similarly, under the influence of temperature, the overall height of the lower and upper high-temperature cylinder heads 10 also increases by about one millimeter, and such height variations are difficult to absorb by the cylinder head application means 24, which must also absorb the axial forces generated by the pressure of the working gas 17 in the lower and upper variable volume high-temperature chambers 11.

[0243] Furthermore, the proximity between the lower and upper hot cylinder heads 10 and the cold cylinders 6 is such that it promotes heat transfer from the cylinder heads 10 to the cylinders 6, which is detrimental to the thermodynamic efficiency of the regenerative Brayton cycle.

[0244] The reciprocating heat engine 1 with hot cylinder head and cold cylinder according to the invention serves both of these requirements, on the one hand, to absorb the large expansion differences between various parts held in contact with each other and operating at very different temperatures, and on the other hand, to limit the heat exchange between said parts.

[0245] Indeed, as can be seen in Figures 2 to 4, 7 and 8, the engine 1 may be provided with a swept-back pillar 101, e.g. made of stainless steel, penetrated longitudinally by a rod tunnel 102, the first pillar end 103 of which is mounted on the transmission casing 42 by a ball joint 105, while the second pillar end 104 of the pillar 101 supports the lower high-temperature cylinder head 10, also by a ball joint 105.

[0246] Because the setback pillars 101 are so long, they form a thermal barrier and limit the heat transfer through the lower cylinder head 10 to the transmission casing 42 .

[0247] In Figures 1, 2, 7 and 8 one can see the traction rods 106 forming the cylinder head application means 24, each of which is partially housed within the rod tunnel 102 of the rear pillar 101 with which they engage, the first rod end 107 of each of which is fixed to the transmission casing 42 by means of rod threads 146 and a rod nut 147 and by a compression spring 148, in this case consisting of a stack of Belleville washers.

[0248] It should be noted that the rod cooling tubes 111 hermetically surround each traction rod 106 over most of its length, and heat transfer liquid 32 supplied by a cooling fluid source 113 at a temperature of approximately 100 degrees Celsius circulates in the space left between the inner wall of the tubes 111 and the outer surface of the rod 106, while most of the outer surface of the tubes 111 is not in contact with the inner wall of the rod tunnel 102 but engages with said wall to define an empty space.

[0249] As can be seen in FIG. 8 , a first tube supply orifice 114 communicates with the interior of the rod cooling tube 111 near the first rod end 107, while a second tube supply orifice 115 communicates with the interior of the rod cooling tube 111 near the second rod end 108, and heat transfer liquid 32 can circulate between the two orifices 114, 115.

[0250] In Figure 8 it is shown that according to a variant of the embodiment of the reciprocating heat engine 1 with a high temperature cylinder head and a low temperature cylinder according to the present invention described, in this case the rod cooling tube 111 can advantageously include a tube collar 116 which is clamped and held against a fixing lug 117 carried by the upper high temperature cylinder head 10 by the traction rod 106 and by an insulating riser 120.

[0251] As shown in FIG. 8 , the tube collar 116 is clamped and held by the traction rod 106 against the fixed lug 117 by a banjo connection 118 which in this case is connected to the coolant source 113 on the one hand and includes a radial connection duct 119 which communicates with the interior of the rod cooling tube 111 on the other hand.

[0252] As can be seen from FIG. 8 , the rod cooling tube 111 includes a number of tube bulges 122 consisting of axial portions of the tube 111, the free diameter of which is slightly larger than the free diameter of the rod tunnel 102 in which it is housed, thereby making it possible to center the tube 111 within the tunnel 102.

[0253] In zone "D" of FIG. 8, it can be seen that the rod cooling tube 111 includes a first tube supply orifice 114 located between two tube bulges 122, which on the one hand communicates with the interior of the rod cooling tube 111 near the first rod end 107 and, on the other hand, is connected via a channel provided in the transmission casing 42 to a coolant source 113, as shown in FIG. 1.

[0254] It can be seen that on the side of the first rod end 107, the rod cooling tube 111 has a tube diameter restriction 123 consisting of an axial portion of the tube 111 whose free diameter is slightly smaller than the free diameter of the body of the traction rod 106, thereby making it possible to center the tube 111 around the rod 106 and to provide local sealing between the tube 111 and the rod 106.

[0255] Advantageously, the tube diameter restriction 123 can be completed or replaced by an elastomeric tube seal 157 to ensure perfect sealing between the traction rod 106 and the rod cooling tube 111.

[0256] When accomplished in this manner, the traction rod 106 can operate at temperatures of approximately 100 degrees Celsius whatever the temperature of the lower and upper high temperature cylinder heads 10 may be and can be made of steel with high mechanical properties without the risk of soaking the steel.

[0257] In any case, this particular configuration that allows the traction rod 106 to be cooled may not be necessary if the traction rod 106 is made of a material that can withstand high temperatures, such as "zirconia," silicon carbide, alumina, or any super alloy specially developed for this type of use.

[0258] Advantageously, the ball joints 105 in contact with the lower and upper high temperature cylinder heads 10 can be made of a material having a very low thermal conductivity, such as zirconium oxide, to limit the passage of heat from the lower and upper high temperature cylinder heads 10 to the rear pillars 101 and traction rods 106.

[0259] As shown in Figures 1, 2, 7 and 8, an insulating riser 120 can be effectively interposed between the traction rod 106 and the upper high-temperature cylinder head 10 to reduce the flow of heat passing from the upper high-temperature cylinder head 10 to the traction rod 106, which in this case is housed within a riser tunnel 121 that passes through the riser 120 in the longitudinal direction.

[0260] This particular arrangement is best illustrated in Figure 8 where it can be seen that each retraction pillar 101 actually has two ball joints 105 about which it is hinged.

[0261] It should be noted that in zone "D" of FIG. 8, a first ball joint 105 is interposed between the first pillar end 103 of the pillar 101 and the transmission casing 42, while zone "C" of the same FIG. 8 shows that a second ball joint 105 is interposed between the second pillar end 104 of the pillar 101 and the lower high-temperature cylinder head 10.

[0262] FIG. 8 also shows that each retraction pillar 101 is effectively threaded lengthwise from one side to the other by a rod tunnel 102 in which a traction rod 106 is housed.

[0263] As shown in zone “D” of FIG. 8, the first rod end 18 of the traction rod 107 is fixed to the transmission casing 42 by a first ball joint 105 .

[0264] Zone “A” in FIG. 8 recalls that the second rod end 108 is actually indirectly fixed to the upper high temperature cylinder head 10 by the rod head 145, the ball joint 105, and the insulating riser 120.

[0265] The rod head 145 holds a lower hot cylinder head 10 and an upper hot cylinder head 10 applied to a cooling cylinder casing 5 , which is clamped between the two cylinder heads 10 .

[0266] This is made possible in particular by fixing a lug 117 in the cylinder head 10, the lug 117 having a lug orifice 144 through which the traction rod 106 passes.

[0267] Zones "B" and "C" in FIG. 8 show this configuration in a particularly clear manner.

[0268] Thus, the different ball joints 105 around which the four setback pillars 101 and traction rods 106 are hinged and which they engage allow the lower and upper high temperature cylinder heads 10 to expand freely, particularly relative to the transmission casing 42.

[0269] However, this can occur when the rearward-facing pillar 101 transmits traction and compression forces to the casing 42, which arise from the pressure exerted alternately on the lower high-temperature cylinder head 10 and the upper high-temperature cylinder head 10 by the working gas 17.

[0270] As shown in Figures 9 and 10, the expansion of the lower and upper hot cylinder heads 10 has little or no effect on the overall length of the assembly formed by the cylinder heads 10 and the cooled cylinder casing 5 together.

[0271] This results from the fact that the cylinder heads 10 each have a concave conical cylinder head surface 25 by means of which the cylinder heads 10 are applied and held by the traction rods 106 against a circular cylinder contact edge 51 provided on the cooling cylinder casing 5.

[0272] The angle of the concave cone formed by the surface 25 is pre-calculated so that the distance separating the rod head 145 from the cooling cylinder casing 5 as the surface 25 slides over the edge 51 due to the difference between the thermal expansion of one or the other of the cylinder head 10 and the thermal expansion of the cylinder casing 5 remains approximately constant, all other conditions being equal.

[0273] Whatever the expansion difference between the expansion of the lower and upper cylinder heads 10 and the expansion of the cooling cylinder casing 5, the circular cylinder contact edges 51 and the respective concave conical cylinder head surfaces 25 of the cylinder heads 10 ensure that the cylinder heads 10 are always centered in the cooling cylinder casing 5.

[0274] In this regard, the concave conical cylinder head surface 25 and the circular cylinder contact edge 51 form the cylinder head centering means 39 of the reciprocating heat engine 1 having a hot cylinder head and a cold cylinder according to the present invention.

[0275] As clearly shown in Figures 9 and 10, the cylinder head centering means 39 and the insulating ring 13 forming the sealed insulating means 12 may form a single unit, with the circular cylinder contact edge 51 forming an integral part of said ring 13, which constitutes a thermal barrier that significantly limits the heat transfer from the hot cylinder head 10 to the cooled cylinder casing 5.

[0276] It should be noted that the advantageous arrangement described above can only function correctly together with the lower cylinder head centering means 109 which is integral with the transmission casing 42, as seen in particular in FIG. 5, and the upper cylinder head centering means 110 as shown in FIG. 6 which is integral with the casing 42 via a centering gantry 127 which is rigidly fixed to the casing 42.

[0277] Said means 109 , 110 ensure the centering and parallelism of the assembly formed by the lower and upper hot cylinder heads 10 and the cooled cylinder casing 5 relative to the transmission casing 42 .

[0278] Said means 109, 110 each consist of an elastic centering disk 134 having a centrally drilled disk hole 135 through which the lower piston rod 46 passes without contacting the elastic centering disk 134 on the side of the lower high-temperature cylinder head 10, and an upper piston rod 128 on the same side as the upper high-temperature cylinder head 10.

[0279] As can be seen in Figures 5 and 6, the periphery of the resilient centering disk 134 forms a disk fixing collar 136 that is sealingly fixed to either the transmission casing 42 or the centering gantry 127, as the case may be.

[0280] 5 and 6 show that the edge of the disk hole 135 has a circular male contact pad 137 that is held in sealing contact with a female centering and sealing cone 138 carried by the lower and upper high-temperature cylinder heads 10, the contact between said pad 137 and said cone 138 causing the centering elastic disk 134 to slightly deform axially from its center within its elastic range, which has the effect of preventing the working gas 17 contained in the lower and upper variable volume high-temperature chambers 11 from leaking out of said chambers 11.

[0281] 5 and 6 show that a relatively large radial length is left on the resilient centering disk 134 between the disk fixing collar 136 and the contact pad 137.

[0282] This length is necessary to allow the disk 134 to deform axially without damaging its center, and is also useful for limiting as much as possible the transfer of heat from the centering and sealing cone 138 to the collar 136.

[0283] In this regard, the body of the resilient centering disk 134 is preferably of small thickness and may be made from zirconium oxide or quartz, both of which are known for their low thermal conductivity.

[0284] It should also be noted that the narrow linear contact formed between centering and sealing cone 138 and contact pad 137 also constitutes an effective thermal barrier in its own right.

[0285] According to this particular configuration of the reciprocating heat engine 1 with hot cylinder heads and cold cylinders according to the invention, the assembly formed by the lower and upper hot cylinder heads 10 and the cooling cylinder casing 5 can substantially expand longitudinally or move relative to the transmission casing 42 over very short distances parallel to the longitudinal axis of the cold cylinders 6, but said assembly can never move relative to said casing 42 in a plane perpendicular to said axis.

[0286] 2 and 7 also show an anti-rotation connection 149 that connects the cooling cylinder casing 5 to the centering gantry 127 to prevent the assembly from rotating about the longitudinal axis of the cryogenic cylinder 6.

[0287] As can be seen in FIG. 5 , the elastic centering disc 134 of the lower high-temperature cylinder head 10 is engaged with a centering and sealing plate 131 rigidly fixed to the transmission casing 42, said plate 131 being pierced by an orifice 132 for access to the power transmission means, through which the lower piston rod 46 passes to be connected to the power transmission means 3.

[0288] It will be noted that the orifice 132 for access to the transmission means includes rod sealing means 133, in this case in the form of two cut segments 150 applied and held against each other by a segment application spring 156 and with offset cut faces, said segments 150 providing sealing between said orifice 132 and the lower piston rod 46.

[0289] As can be seen in FIG. 6 , the elastic centering disk 134 of the upper high temperature cylinder head 10 is fixed to a centering gantry 127 having an orifice 130 for accessing the cooling lubrication chamber, through which the upper piston rod 128 passes and opens into a piston cooling lubrication chamber 125 which is connected to a lubricating cooling fluid source 126.

[0290] It will be noted in FIG. 6 that the access orifice 130 to the cooling lubrication chamber also has a rod sealing means 133 in the form of two cut segments 150 which are also offset in cut plane, and which segments 150 are also held applied against each other by a segment application spring 156.

[0291] As can be readily understood from Figures 5 and 6, the lower piston rod 46 and the upper piston rod 128 are lubricated, sealed and cooled by lubricant present and / or circulating within the transmission casing 42 and the piston cooling lubrication chamber 125, respectively.

[0292] As shown in FIGS. 9 and 10, the principle prevailing in the lower and upper cylinder heads 10 and the cooling cylinder casing 5 is also found in the double-acting piston 2.

[0293] It should be noted in this figure that the piston sealing ring 37 provided on the periphery of the piston 2 comprises piston sealing means 30, in this case formed by a piston ring 151 similar to the piston ring of a conventional spark ignition or compression internal combustion engine.

[0294] The piston sealing ring 37 is maintained at a temperature of approximately 100 degrees Celsius by a lubricating cooling fluid 139 (in this case oil), which circulates from the piston cooling lubrication chamber 125 to the transmission casing 42 through an upper piston rod internal channel 140 longitudinally disposed in the upper piston rod 128, an internal piston cavity 141, and a lower piston rod internal channel 142 longitudinally disposed in the lower piston rod 46.

[0295] It should be noted that when the reciprocating heat engine 1 having a hot cylinder head and a cold cylinder (described in this case as an example) is stopped, as long as the hot cylinder head 10 and the lower and upper hot crowns 19 continue to transfer heat to the components of the double-acting piston 2 and risk bringing the lubrication cooling fluid 139 contained therein to coking or even combustion temperatures, the lubrication cooling fluid source 126 can continue to circulate the lubrication cooling fluid 139 from the piston cooling lubrication chamber 125 through the internal piston cavity 141 to the transmission casing 42 to cool the components of the double-acting piston 2.

[0296] It should be noted in particular in Figures 9 and 10 that the periphery of the internal piston cavity 141 communicates with the outer circumferential surface of the piston sealing ring 37 via a peripheral ring lubrication orifice 143 opening axially between the two piston rings 151, said orifice 143 forming both the lubrication means 8 and at least part of the sealing ring cooling means 38.

[0297] It should be noted that the piston sealing ring 37 has, between the two piston rings 151, piston guide means 29 for guiding the piston 2 in the low-temperature cylinder 6, which in this case consist of a barrel-shaped annular sliding surface 43, which promotes the hydrodynamic lift of the lubricating film 7 interposed between it and the cylinder 6.

[0298] As can be easily seen from Figures 5, 6, 9 and 10, an oil scraper segment 152 can be advantageously inserted between the annular sliding surface 43 and the piston ring 151 arranged on the side of the lower variable volume high temperature chamber 11, and it should also be noted that the peripheral ring lubrication orifice 143 opens between the two lips of said scraper segment 152.

[0299] The dual function of the oil scraper ring 152 is to spread the lubricating cooling fluid 139 over the inner walls of the cold cylinder 6 while collecting any excess fluid 139 on the walls.

[0300] As can be clearly seen in Figures 9 and 10, the lower and upper high temperature crowns 19 each have a concave conical crown surface 26 through which they are applied and held by crown application means 23 against a circular piston contact edge 52 provided on the piston 2.

[0301] It should be noted in particular in Figures 3, 7, 9 and 10 that the crown application means 23 in this case consists of an axial double-acting piston screw 153 which, on the one hand, fixes the double-acting piston 2 on the crosshead 49 and, on the other hand, applies the lower and upper high-temperature crowns 19 onto the piston sealing ring 37 via a crown application tube 154 and a crown application spring 155 which in this case consists of a stack of "Belleville" washers.

[0302] 9 and 10 show that the angle of the concave cone formed by the concave conical crown surface 26, whether it is the lower or upper hot crown 19, has been pre-calculated so that due to the difference between the thermal expansion of said crown 19 and that of the piston 2, the distance separating the head of the axial double-acting piston screw 153 from the bearing point of the crown application means 23 on the high temperature crown 19 as said surface 26 slides over the circular piston contact edge 52 it engages remains approximately constant, all other conditions being equal, so that the crown application spring 155 is neither further compressed nor expanded.

[0303] Therefore, all other things being equal, the traction force experienced by the axial double acting piston screw 153 remains approximately constant regardless of the thermal expansion difference between the thermal expansion of the lower and upper high temperature crowns 19 and the thermal expansion of the piston 2.

[0304] According to this particular configuration of the reciprocating heat engine 1 with hot cylinder head and cold cylinder according to the invention, the concave conical crown surface 26 and the circular piston contact edge 52 form the crown centering means 40.

[0305] It will be noted that the reciprocating heat engine 1 with hot cylinder head and cold cylinder according to the invention shown in FIG. 11 uses the above-described principles, except that the cooling cylinder casing 5 is fixed directly to the transmission casing 42, rather than being suspended on the rearward-reaching pillar 101 as shown in FIGS. 2, 3, 4, 7 and 8.

[0306] According to this particular configuration of the reciprocating heat engine 1 with hot cylinder head and cold cylinders according to the invention, the cylinder head application means 24 is formed by a cylinder head application screw 59 which holds the lower or upper hot cylinder head 10 applied onto the cooled cylinder casing 5, as the case may be, via an insulating riser 120 made, for example, of quartz, which is a ceramic with low thermal conductivity.

[0307] In FIG. 11 it will be noted that a compression spring 148, which in this case may consist of a stack of "Belleville" type elastic washers, is advantageously inserted between the screw head 60 of the cylinder head application screw 59 and the insulating riser 120 which it engages.

[0308] It should be understood that the possibilities of the reciprocating heat engine 1 with a hot cylinder head and a cold cylinder according to the invention are not limited to the applications described herein, and furthermore that the above description is given only as an example and does not in any way limit the field of the invention, and that the replacement of the implementation details described by other equivalent ones does not depart from the invention.

Claims

1. A reciprocating heat engine (1) having a hot cylinder head and a cold cylinder, comprising a cooling cylinder casing (5) in which is arranged at least one cold cylinder (6) in which a piston (2) oriented and / or positioned by a piston guide means (29) can move in translation, said piston (2) being directly or indirectly connected to at least one rotating or reciprocating power output shaft (4) by a power transmission means (3) housed in a transmission casing (42), a lubricating means (8) for forming a lubricating film (7) interposed between the low-temperature cylinder (6) and the piston (2); cylinder casing cooling means (9) for cooling the cooling cylinder casing (5) in order to maintain all or part of the inner surface of the low-temperature cylinder (6) at a temperature sufficiently low to prevent premature aging, coking or burning of the lubricating film (7); at least one high-temperature cylinder head (10), the operating temperature of which is significantly higher than the operating temperature of the cooled cylinder casing (5) which it covers in order to form, together with the piston (2), a high-temperature chamber (11) of variable volume for containing a working gas (17), said cylinder head (10) being applied and held against said cooled cylinder casing (5) by cylinder head application means (24) which, on the one hand, allow said cylinder head (10) to freely expand relative to said cylinder casing (5) and, on the other hand, being positioned against said cylinder casing (5) by cylinder head centering means (39); at least one piston sealing ring (37) arranged on the periphery of said piston (2), said ring (37) comprising, on the one hand, piston sealing means (30) forming a seal between said piston (2) and said cold cylinder (6) and, on the other hand, cooled by sealing ring cooling means (38); at least one high temperature crown (19) interposed between said variable volume high temperature chamber (11) and said piston (2) and having an operating temperature significantly higher than the operating temperature of said cooling cylinder casing (5), said crown (19) being applied and held against said piston (2) on the one hand by crown application means (23) allowing said crown (19) to freely expand relative to said piston (2) and, on the other hand, being positioned against said piston (2) by crown centering means (40).

2. 2. A reciprocating heat engine according to claim 1, characterized in that a sealed thermal insulation means (12) is interposed between the cold cylinder casing (5) and the hot cylinder head (10).

3. 2. A reciprocating heat engine according to claim 1, characterized in that a thermal insulation means (22) is interposed between said hot crown (19) and said piston (2).

4. 4. A reciprocating heat engine according to claim 3, characterized in that said thermal insulation means (22) consist of a reflective screen (57).

5. 4. A reciprocating heat engine according to claim 3, characterized in that said thermal insulation means (22) comprises a honeycomb or fibrous insulating material (58) occupying all or part of the space between said hot crown (19) and said piston (2).

6. A reciprocating heat engine according to claim 2 or 3, characterized in that the thermal insulation means (22) consist of at least one insulating ring (13) made of a material with low thermal conductivity (14).

7. 7. A reciprocating heat engine according to claim 6, characterized in that the low thermal conductivity material (14) consists essentially of zirconium oxide (15).

8. 7. A reciprocating heat engine according to claim 6, characterized in that the insulating ring (13) forming the sealed insulating means (12) is in direct or indirect contact with the cooling cylinder casing (5) and / or the hot cylinder head (10) by at least one small surface contact edge (16) which prevents the working gas (17) from passing between the cooling cylinder casing (5) and the hot cylinder head (10).

9. 7. A reciprocating heat engine according to claim 6, characterized in that the insulating ring (13) forming the insulating means (22) is in direct or indirect contact with the hot crown (19) and / or the piston (2) by at least one small surface contact edge (16).

10. 7. A reciprocating heat engine according to claim 6, characterized in that a cylinder head seal (18) is interposed between the insulating ring (13) forming the sealed insulating means (12) and the cold cylinder case (5) and / or between the ring (13) and the hot cylinder head (10).

11. 7. A reciprocating heat engine according to claim 6, characterized in that a piston seal (36) is interposed between the insulating ring (13) forming the thermal insulation means (22) and the hot crown (19) and / or between the ring (13) and the piston (2).

12. 2. A reciprocating heat engine according to claim 1, characterized in that the high-temperature cylinder head (10) and / or the high-temperature crown (19) are made entirely or partly of a high-temperature resistant material (20).

13. 13. A reciprocating heat engine according to claim 12, characterized in that the high-temperature resistant material (20) consists essentially of silicon carbide (21).

14. 2. A reciprocating heat engine according to claim 1, characterized in that the hot cylinder head (10) comprises a concave conical cylinder head surface (25) by means of which the cylinder head (10) is applied and held by the cylinder head application means (24) against a circular cylinder contact edge (51) provided on the cooling cylinder casing (5), the angle of the concave cone formed by the surface (25) being such that when the surface (25) slides over the edge (51) due to the difference between the thermal expansion of the cylinder head (10) and the thermal expansion of the cylinder casing (5), the concave conical cylinder head surface (25) and the circular cylinder contact edge (51) form the cylinder head centering means (39), while the axial distance separating the bearing point of the cylinder head application means (24) against the hot cylinder head (10) from the cooling cylinder casing (5) remains approximately constant, all other conditions being equal.

15. 2. A reciprocating heat engine according to claim 1, characterized in that the hot crown (19) has a concave conical crown surface (26) by which the hot crown (19) is applied and held by the crown application means (23) against a piston circular contact edge (52) provided on the piston (2), the angle of the concave cone formed by the surface (26) being such that when the surface (26) slides over the edge (252) due to the difference between the thermal expansion of the crown (19) and the thermal expansion of the piston (2), the axial distance separating the bearing point of the crown application means (23) against the hot crown (19) from the piston (2) remains substantially constant, all other conditions being equal, while the concave conical crown surface (26) and the piston circular contact edge (52) form the crown centering means (40).

16. 2. A reciprocating heat engine according to claim 1, characterized in that the hot crown (19) has an aerodynamic passivation bead (53) on its periphery.

17. 2. A reciprocating heat engine according to claim 1, characterized in that the outside of the high-temperature cylinder head (10) is covered with a heat insulating material (41).

18. 2. A reciprocating heat engine according to claim 1, characterized in that the piston sealing ring (37) has piston guide means (29) consisting of an annular sliding surface (43).

19. 2. A reciprocating heat engine according to claim 1, characterized in that the cooled cylinder casing (5) is clamped and held between a lower hot cylinder head (10) and an upper hot cylinder head (10) by means of the cylinder head application means (24), while the piston (2) is double-acting and comprises, on the one hand, a lower piston rod (46) connecting the piston to the power transmission means (3) and passing through the lower hot cylinder head (10) via a lower rod orifice (47), and, on the other hand, a lower high temperature crown (19) and an upper high temperature crown (19) for defining, together with the lower and upper high temperature cylinder heads (10), a lower variable volume high temperature chamber (11) and an upper variable volume high temperature chamber (11).

20. The reciprocating heat engine, at least one recessed pillar (101) longitudinally penetrated by a rod tunnel (102), a first pillar end (103) of said pillar (101) resting directly or indirectly on said transmission casing (42) while a second pillar end (104) of said pillar (101) supports said lower hot cylinder head (10), said first end (101) being able to pivot about a ball joint (105) and / or bend relative to said casing (42) while said second end (104) being able to pivot about a ball joint (105) and / or bend relative to said lower hot cylinder head (10); at least one traction rod (106) forming the cylinder head application means (24) and housed at least partially in the rod tunnel (102), a first rod end (107) of the traction rod (106) being fixed directly or indirectly to the transmission casing (42) while a second rod end (108) of the rod (106) is fixed directly or indirectly to the upper hot cylinder head (10), the first end (107) being able to pivot about a ball joint (105) and / or bend relative to the casing (42) while the second end (108) being able to pivot about a ball joint (105) and / or bend relative to the cylinder head (10); lower cylinder head centering means (109) fixed to the transmission casing (42) and bearing directly or indirectly on the lower hot cylinder head (10), allowing the cylinder head (10) to move freely relative to the transmission casing (42) a short distance parallel to the longitudinal axis of the cold cylinder (6), but preventing the cylinder head (10) from moving relative to the casing (42) in a plane perpendicular to said axis; 20. A reciprocating heat engine according to claim 19, characterized in that it comprises upper cylinder head centering means (110) fixed to a centering gantry (127) which is rigidly fixed to the transmission casing (42), said means (110) bearing directly or indirectly on the upper hot cylinder head (10), said means (109) allowing the cylinder head (10) to move freely relative to the transmission casing (42) for a short distance parallel to the longitudinal axis of the cold cylinder (6), but preventing the cylinder head (10) from moving relative to the casing (42) in a plane perpendicular to said axis.

21. 21. A reciprocating heat engine according to claim 20, characterized in that a rod cooling tube (111) hermetically surrounds the traction rod (106) over all or part of the length of the rod (106), so that a heat transfer liquid (32) coming from a cooling liquid source (113) can circulate in the space left between the inner wall of the tube (111) and the outer surface of the rod (106), while the largest possible part of the outer surface of the tube (111) does not come into contact with the inner wall of the rod tunnel (102) and defines an empty space together with this latter wall.

22. 22. A reciprocating heat engine according to claim 21, characterized in that at least one first tube supply orifice (114) communicates with the interior of the rod cooling tube (111) in the vicinity of the first rod end (107) and at least one second tube supply orifice (115) communicates with the interior of the rod cooling tube (111) in the vicinity of the second rod end (108), and the heat transfer liquid (32) can circulate between the two orifices (114, 115).

23. 22. The reciprocating heat engine according to claim 21, characterized in that the rod cooling tubes (111) have tube collars (116) clamped and held against fixed lugs (117) of the upper high-temperature cylinder head (10) or against the transmission casing (42) directly or indirectly by the traction rods (106).

24. 22. A reciprocating heat engine according to claim 21, characterized in that the tube collar (116) is clamped and held by the traction rod (106) against the fixed lug (117) by a banjo connection (118) including at least one radial connection duct (119) connected on the one hand to the cooling fluid source (113) and on the other hand in communication with the interior of the rod cooling tube (111).

25. 24. A reciprocating heat engine according to claim 23, characterized in that an insulating riser (120) is interposed between the tube collar (116) and the fixing lug (117), the riser (120) being penetrated in its length by a riser tunnel (121) in which the traction rod (106) and the rod cooling tube (111) sealingly surrounding it are housed, while the largest possible part of the outer surface of the tube (111) does not come into contact with the inner wall of the riser tunnel (121) and defines an empty space together with this latter wall.

26. 22. The reciprocating heat engine according to claim 21, characterized in that the rod cooling tube (111) comprises at least one tube bulge (122) consisting of an axial portion of the tube (111), the free diameter of the tube bulge being substantially equal to or slightly larger than the free diameter of the rod tunnel (102) in which the tube bulge is housed.

27. 22. A reciprocating heat engine according to claim 21, characterized in that the rod cooling tube (111) comprises at least one tube diameter restriction (123) consisting of an axial portion of the tube (111), the free diameter of the tube diameter restriction being substantially equal to or slightly smaller than the free diameter of the body of the traction rod (106).

28. 21. A reciprocating heat engine according to claim 20, characterized in that the traction rod (106) is hollow to form internal rod cooling channels along the length of the rod (106), said channels opening axially or radially near each end of the rod (106) while a heat transfer liquid (32) originating from a cooling liquid source (113) can circulate within said channels.

29. 21. A reciprocating heat engine according to claim 20, characterized in that a piston cooling lubrication chamber (125) connected to a lubrication cooling fluid source (126) is fixed to or made on or in the centering gantry (127), while an upper piston rod (128) extending the double-acting piston (2) on the side of the upper variable-volume high-temperature chamber (11) passes through the upper high-temperature cylinder head (10) through an upper rod orifice (129) provided in the cylinder head (10) and through an access orifice (130) to the cooling lubrication chamber passing through the centering gantry (127) and opening into the piston cooling lubrication chamber (125), so that the end of the upper piston rod (128) farthest from the piston (2) remains always immersed in the chamber (128), regardless of the position of the piston (2).

30. 30. The reciprocating heat engine of claim 29, characterized in that a lubrication cooling fluid (139) can be circulated from the piston cooling lubrication chamber (125) to the transmission casing (42) by passing sequentially through an upper piston rod internal channel (140) longitudinally provided in the upper piston rod (128), an internal piston cavity (141), and a lower piston rod internal channel (142) longitudinally provided in the lower piston rod (46).

31. 31. A reciprocating heat engine according to claim 30, characterized in that the periphery of the internal piston cavity (141) communicates with the outer circumferential surface of the piston sealing ring (37) through at least one peripheral ring lubrication orifice (143) opening axially between at least two piston sealing means (30), said orifice (143) consisting of said lubrication means (8).

32. 21. A reciprocating heat engine according to claim 20, characterized in that the transmission casing (42) is covered with a centering and sealing plate (131) drilled with orifices (132) for access to the power transmission means (3) through which the lower piston rod (46) passes in order to be connected to said transmission means, said plate (131) being rigidly fixed to the casing (42).

33. 30. A reciprocating heat engine according to claim 29, characterized in that the access orifice (130) to the cooling lubrication chamber includes rod sealing means (133) providing sealing between the orifice (130) and the upper piston rod (128).

34. 31. A reciprocating heat engine according to claim 30, characterized in that the access orifice (132) to the transmission means includes rod sealing means (133) providing sealing between the orifice (132) and the lower piston rod (46).

35. 21. A reciprocating heat engine according to claim 20, characterized in that the lower cylinder head centering means (109) and / or the upper cylinder head centering means (110) consist of an elastic centering disk (134) which can be drilled around a disk hole (135) through which the lower piston rod (46) or the upper piston rod (128), respectively, passes, while the periphery of the elastic centering disk (134) forms a disk fixing collar (136) which is sealingly fixed to the transmission casing (42) and / or to the centering gantry (127), respectively.

36. The centering and sealing plate (131) carries the lower cylinder head centering means (109) consisting of a resilient centering disc (134) whose periphery forms a disc fixing collar (136) sealingly fixed to the plate (131) and which has in its center a disc hole (135) through which the lower piston rod (46) passes without contacting the disc (134).

33. A reciprocating heat engine according to claim 32, characterized in that the elastic centering disk (134) is perforated, the edge of the disk hole (135) having a circular contact pad (137) maintained in sealing contact with a centering and sealing cone (138) of the lower high-temperature cylinder head (10), said cone (138) may be male or female, said contact between said pad (137) and said cone (138) having the effect of deforming said elastic centering disk (134) axially from its centre.

37. 21. A reciprocating heat engine according to claim 20, characterized in that the upper cylinder head centering means (110) consists of an elastic centering disk (134) whose periphery forms a disk fixing collar (136) sealingly fixed to the centering gantry (127), the disk (134) being drilled with a disk hole (135) in its center and the edge of the disk hole (135) having a circular contact pad (137) held in sealing contact with a centering and sealing cone (138) carried by the upper high-temperature cylinder head (10), the cone (138) may be male or female, the contact between the pad (137) and the cone (138) having the effect of deforming the elastic centering disk (134) axially from its center.

38. 21. A reciprocating heat engine according to claim 20, characterized in that an anti-rotation connection (149) connects the lower hot cylinder head (10) and / or the upper hot cylinder head (10) and / or the cooling cylinder casing (5) directly or indirectly to the centering gantry (127).

39. 2. A reciprocating heat engine according to claim 1, characterised in that said cylinder head application means (24) consist of at least one cylinder head application screw (59) cooled by said cylinder casing cooling means (9).

40. 40. A reciprocating heat engine according to claim 39, characterized in that a thermal insulating riser (120) is interposed between the screw head (60) of the cylinder head fastening screw (59) and the high temperature cylinder head (10).

41. A reciprocating heat engine according to claim 40, characterized in that at least one compression spring (148) is interposed between said screw head (60) and said insulating riser (120).

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