Heat engine

Abstract

The present invention relates to a heat engine with an external heat source, consisting of a main piston (B) which performs the mechanical work on a crankshaft, when driven by a preferably monatomic working fluid, which expands due to the discharge from a feeder (A1, A2), which is a container holding working fluid that has been previously heated at a constant volume inside the feeder, there being at least two feeders (A1, A2) for each main piston (B) and two more pistons (C, D) for recycling the working fluid, in order to refill each feeder (A1, A2) under the cycle start conditions. For optimal use, two identical engines are used, the operation of said engines being out of phase relative to one another by exactly one stroke of the cycle. Moreover, in another variant that improves the heating process, more than two feeders (A1, A'1, A2, A'2) are positioned connected to a single main piston (B), and time-division multiplexing of the feeders (A1, A'1, A2, A'2) is applied.

Description

[0001] DESCRIPTION

[0002] Internal combustion engine

[0003] Object of the invention

[0004] The present invention relates to a heat engine that transforms the thermal energy of a working fluid circulating between three cylinders into mechanical energy that is transferred to the engine shaft, wherein the heat source that heats the working fluid is located outside the engine cylinders.

[0005] The thermal engine that is the subject of the present invention falls within the field of thermal engines, intended to convert heat, or more precisely thermal energy, into mechanical energy; and within them, the engines called Stirling, or external combustion engines.

[0006] Background of the invention and technical problem to be solved

[0007] There is a wealth of literature on heat engines and machines, particularly on Stirling engines, a generic name that originally referred to a single-cylinder design in the 19th century, with heat and cold applied sequentially from the outside. Today, Stirling engines incorporate several conceptual and operational improvements, such as thermal regeneration through the use of two cylinders: a main cylinder, which is the true driving force of the mechanical components, and a smaller cylinder that restores the working fluid to its initial operating conditions. This working fluid circulates sequentially through the parts of a closed circuit, which is essentially powered by a hot source connected to the main piston and a cold source that dissipates excess heat from the cycle, allowing the fluid to reach the appropriate initial operating conditions.

[0008] For studying precedents in this field, document ES 2 654 338 T3 is particularly useful. It deals with improved efficiency positive displacement internal combustion engines. It is based on a large main piston and a smaller, cooler secondary piston, which is the most common configuration among Stirling engines today. This document contains a detailed account of the prior art of heat engines in different cycles, beginning with the Newcomen steam engine (which is simply a generic thermodynamic precedent, not specific to Stirling). Among the documents it discusses, Nissan's 1973 patent JP 1439446 stands out. It presents a piston expander driven by the explosive reaction of a fuel and a liquid oxidizer such as hydrogen peroxide or liquid oxygen, without the use of atmospheric air.Logically, this assembly does not correspond to a pure Stirling, but to a line called, among specialists, hybrid Stirling, which are also not precedents of the invention presented here.

[0009] Document ES 2 612 271 T3 corresponds to a hybrid engine, defined as having a variable volume working chamber for a working gas, and a distribution that connects this chamber with a cold inlet in a heat receiving path during an output transfer phase and with a heat outlet in the heat receiving path during an input transfer phase, the heat receiving path being intended to reheat the working gas on the outside of the chamber upon contact with the external source.

[0010] Document ES 2 852 024 describes a Stirling engine and its method of use. The most novel aspect is that the engine comprises at least one diaphragm connecting one of the pistons to a cylinder, with one end of the diaphragm fixed in place. Furthermore, this document clearly describes the ideal Stirling cycle, which it aims to approximate, and which consists of four stages:

[0011] 1 a : isothermal compression of the working gas;

[0012] 2 a : isochoric displacement of the gas (through the regenerator) from cold to hot;

[0013] 3 a : isothermal expansion of the working gas; and

[0014] 4 a : isochoric displacement of the gas (through the regenerator) from hot to cold

[0015] Document ES 2 886454 T3 presents another configuration of a regenerative closed-cycle thermal engine, with an elastically deformable displacer housed in the main chamber of the engine; and with a shaft connected to said displacer, through which the mechanical action is exerted.

[0016] There are several other documents that present proposals for engines of this type, such as ES 2 939 241 T3, which corresponds to a high-efficiency linear combustion engine; or ES 2 557 632 T3, with two cylinders connected to each other for the passage of the working fluid, and also a suitable heat transfer fluid to activate the cyclic motion. Also worth mentioning is ES 2 433 128 T3, which is a thermal cycle engine with an increased thermal energy input area, since a crucial problem in these engines is how to transfer heat from the external heat source to the hottest part of the engine.

[0017] Finally, it is worth mentioning document US 2006 / 028318.6 A1, which presents a set of mechanisms for operating a classic Stirling cycle, optimized in the thermodynamic-mechanical relationship.

[0018] Description of the invention

[0019] The present invention relates to a thermal engine with a configuration or assembly of the elements necessary so that through them, circulating a working fluid in a closed circuit, the thermal energy carried by a stream of another fluid, the hot fluid, is used, converting its thermal energy into mechanical energy of the main shaft of the engine.

[0020] By taking advantage of the characteristics and properties of the different available thermal engineering components, and by carrying out the thermodynamic analysis necessary for the designed thermodynamic and mechanical cycle to be physically feasible, the present invention achieves a high-efficiency thermal engine in the energy conversion of thermal energy into mechanical energy.

[0021] Therefore, in order to achieve the aforementioned objectives, the present invention relates to a heat engine. The heat engine of the present invention comprises a plurality of elements forming a closed circuit of a working fluid, wherein the heat engine comprises:

[0022] - at least a first feeder (A1) comprising a sealed container for the working fluid, wherein the first feeder (A1) is located in a first branch of the closed circuit of the working fluid, and has controlled opening valves;

[0023] - at least a second feeder (A2) comprising a sealed container for the working fluid, wherein the second feeder (A2) is located in a second branch of the closed circuit of the working fluid and has controlled opening valves;

[0024] - a main piston (B) located in correspondence with a main cylinder, where the main piston (B) is connected to a shaft of the heat engine by means of a connecting rod and crankshaft; where the main piston (B) is configured to move, in each operating cycle of the heat engine, at least twice in the compression direction in the main cylinder and at least twice in the expansion direction in the main cylinder, and where the main cylinder is configured to: either be filled with working fluid taken alternately from at least a first feeder (A1) and from at least a second feeder (A2) on each expansion stroke of the main piston (B) through the corresponding valve; and either expel working fluid on each compression stroke of the main piston (B), sending said working fluid to a secondary cylinder through the corresponding valve;

[0025] - a secondary piston (C) located corresponding to the secondary cylinder, wherein the secondary piston (C) is configured to move, in each operating cycle of the heat engine, at least twice in the compression direction in the secondary cylinder and at least twice in the expansion direction in the secondary cylinder; wherein the secondary piston (C) is configured to move in the expansion direction when the main piston (B) moves in the compression direction and vice versa, wherein the secondary cylinder is configured to: either be filled with working fluid taken from the main cylinder on each expansion stroke of the secondary piston (C) through the valve provided for that purpose, and; or expel working fluid on each compression stroke of the secondary piston (C), sending said working fluid to a feeder (A1, A2) through the valve provided for that purpose;

[0026] - a tertiary piston (D) located in correspondence with a tertiary cylinder, where the tertiary piston (D) is configured to move, in each operating cycle of the heat engine, at least twice in the compression direction in the tertiary cylinder and at least twice in the expansion direction in the tertiary cylinder; where the tertiary piston (D) is configured to move in the expansion direction when the main piston (B) moves in the compression direction and vice versa, where the tertiary cylinder is configured to: either be filled with working fluid taken from a feeder (A1, A2) on each expansion stroke of the tertiary piston (D), and; or expel working fluid on each compression stroke of the tertiary piston (D), sending said working fluid to a feeder (A1, A2).where the feeders (A1, A2) are configured so that, within them, the working fluid is heated by the heat received from an external heat transfer fluid.

[0027] According to a first embodiment of the thermal engine of the present invention, the thermal engine comprises only two feeders (A1, A2), and:

[0028] - the main piston (B) is configured to move, in each operating cycle of the heat engine, twice in the compression direction in the main cylinder and twice in the expansion direction in the main cylinder; such that: either in a first compression and expansion sub-cycle of the main piston (B), during the expansion movement of the main piston (B), the main cylinder is configured to be connected to the first feeder (A1) by opening a discharge valve of the first feeder (Ga1 b), and; or in a second compression and expansion sub-cycle of the main piston

[0029] (B), during the expansion movement of the main piston (B), the main cylinder is configured to be connected to the second feeder (A2) by opening a discharge valve of the second feeder (Ga2b); or in the first sub-cycle and in the second sub-cycle of compression and expansion of the main piston (B), during the compression movement of the main piston (B), the main cylinder is configured to be connected to the secondary cylinder by opening a bypass valve (Gbc);

[0030] - the secondary piston (C) is configured to move, in each operating cycle of the heat engine, twice in the compression direction in the secondary cylinder and twice in the expansion direction in the secondary cylinder, such that: or in a first compression and expansion sub-cycle of the secondary piston

[0031] (C):

[0032] ■ During the compression movement of the secondary piston (C), the secondary cylinder is configured to be connected to the second feeder (A2) by opening a second charging valve (Gca2), and;

[0033] ■ During the expansion movement of the secondary piston (C), the secondary cylinder is configured to be connected to the main cylinder by opening the bypass valve (Gbc), and; or in a second sub-cycle of compression and expansion of the secondary piston (C):

[0034] ■ During the compression stroke of the secondary piston (C), the secondary cylinder is configured to be connected to the first (A1) by opening a first charging valve (Gca1), and;

[0035] ■ During the expansion movement of the secondary piston (C), the secondary cylinder is configured to be connected to the main cylinder by opening the bypass valve (Gbc);

[0036] - the tertiary piston (D) is configured to move, in each operating cycle of the heat engine, twice in the compression direction in the tertiary cylinder and twice in the expansion direction in the tertiary cylinder, such that: or in a first compression and expansion sub-cycle of the tertiary piston (D):

[0037] ■ During the compression stroke of the tertiary piston (D), the tertiary cylinder is configured to be connected to the second feeder (A2) by opening a fourth charging valve (Gda2), and;

[0038] ■ During the expansion movement of the tertiary piston (D), the tertiary cylinder is configured to be connected to the first feeder (A1) by opening a first suction valve (Ga1 d), and; or in a second sub-cycle of compression and expansion of the tertiary piston (D):

[0039] ■ During the compression movement of the tertiary piston (D), the tertiary cylinder is configured to be connected to the first feeder (A1) by opening a third charging valve (Gda1), and; ■ During the expansion movement of the tertiary piston (D), the tertiary cylinder is configured to be connected to the second feeder (A2) by opening a second suction valve (Ga2d).

[0040] According to a second embodiment of the heat engine of the present invention, the heat engine comprises:

[0041] - at least a third feeder (A'1) located in the first branch of the closed circuit of the working fluid;

[0042] - at least a fourth feeder (A'2) located in the second branch of the closed circuit of the working fluid; where the heat engine is configured to:

[0043] - multiplex the actuation of the valves that connect each feeder (A1, A'1, A2, A'2) to the main cylinder during the expansion movements of the main piston (B);

[0044] - multiplex the actuation of the valves that connect each feeder (A1, A'1, A2, A'2) to the secondary cylinder during the compression movements of the secondary piston (C);

[0045] - Multiplex the actuation of the valves that connect each feeder (A1, A'1, A2, A'2) to the tertiary cylinder during the compression and expansion movements of the tertiary piston (D).

[0046] According to a variant of this second embodiment of the invention, the thermal engine comprises a thermal inertia reservoir (H) connected between the main cylinder and the secondary cylinder.

[0047] Preferably, in any embodiment of the heat engine of the invention, the heat engine comprises a working fluid flow management system in the feeders (A1, A'1, A2, A'2). According to one possible embodiment, this working fluid flow management system in the feeders (A1, A'1, A2, A'2) comprises a charging device connected to the feeders (A1, A'1, A2, A'2), wherein said charging device comprises:

[0048] - an ejection valve (Z21) in each working fluid feeder (A1, A'1, A2, A'2), whose outlet communicates with a low-pressure reservoir (Z23), configured to store said working fluid for a period of time;

[0049] - a pump (Z24) configured to pump and pressurize the working fluid from the low-pressure reservoir (Z23) to a high-pressure reservoir (Z25), and;

[0050] - an injection valve (Z26), configured to control the passage of the working fluid from the high pressure reservoir (Z25) to the corresponding feeder (A1, A'1, A2, A'2).

[0051] Thus, in the present invention, a thermodynamic engine is defined that consists of a series of components connected to each other by means of ducts, forming a closed circuit, part of it formed by two parallel branches, called even and odd, and along the circuit circulates a working fluid, which is a gas of practically ideal behavior, selected from monatomic, particularly argon, or polyatomic, and even a mixture of them, such as air, the components of this circuit being those presented below, starting with two feeders, each one integrated into a branch of the circuit, these feeders being sealed containers, resistant to pressures and temperatures of the level that will be needed, according to the external heat source whose exhaust flow will heat the feeders in the corresponding stage of the cycle, which is four strokes, or four stages, which is actually the result of a double two-stroke cycle,symmetrically offset from each other, each one followed along a branch, with a common trunk to both branches, in which there is a main piston, from whose connecting rod the mechanism is actuated, with the corresponding crank, to rotate the engine crankshaft, which is where the generated mechanical energy is obtained, said piston circulating, up and down, twice in each four-stroke cycle, each of the times in connection with a certain branch, even or odd, the piston receiving the discharge of the high temperature and high pressure gas that was contained in the feeder of the turn, which causes the expansion of said main piston, it being noted that, in the time or stage prior to this of the expansion, the gas of the feeder is heated at constant volume by the hot external flows, and after the expansion, as the main piston begins the rise towards its top dead center reducing the volume of its cylindrical chamber,The connecting valve between the feeder and the main piston closes, and the gas that occupied the cylinder is pushed towards the secondary piston, through the exhaust valve, which is open only during the exhaust stroke. The gas then passes to a second cylinder, or secondary piston, not dedicated to the production of mechanical energy, but to replenishing the gas transferred from the main piston to the starting conditions of the cycle. For this purpose, the gas must be cooled, not only inside this second cylinder, but also during its transfer from the main piston. In the next stage, when the main piston is expanding again due to the action of the other feeder, and therefore descending to its bottom dead center, the piston of the second piston rises, pushing the gas to fill the feeder of the branch, which is cold at that moment, and to do so at the appropriate temperature.And just as there is a main piston and a second piston or secondary piston in the common trunk, there is a third piston or tertiary piston, which partially evacuates the feeder that has just finished expanding, cooling the transferred gas to recover the conditions at the beginning of the cycle. This tertiary piston moves parallel to the secondary piston, so that when the secondary piston loads its gas into the corresponding feeder, the tertiary piston also loads its gas into the same feeder at the same time. Thus, in the four stages of a complete cycle, two consecutive phases are distinguished, each of a complete revolution. In the first of these, one of the branches has been in a mechanically active phase, turning the crankshaft, while the other branch was in the phase of recycling the working gas flows, replenishing the contents of the cold feeder, to close it and begin a new active phase.in which the roles of the branches are exchanged, and the feeder that has just been filled is subjected to constant volume heating, which is the stage prior to expansion; there are also corresponding valves in all the connecting ducts, which open when prescribed by the operating mode with which the desired cycle is generated, which is composed of the following stages: an expansion between adiabatic and isothermal; a cooling at almost constant pressure, followed by a small adiabatic compression provided by the thrust of the secondary, C and tertiary, D pistons, the fourth and last stage being constant volume heating, after which an expansion begins again.

[0052] The accuracy in the execution of the cycle is achieved by the synchronization in the movement of the piston plungers, and the opening and closing of the various valves that regulate the passage from one component to another. Regarding the synchronization between pistons, it should be noted that as the main piston descends, in the expansion, from its top dead center to its bottom dead center, the secondary and tertiary pistons move in the intrinsically opposite direction, each from its bottom dead center to its top dead center; and vice versa, when the main piston rises from its bottom dead center to its top dead center, and is evacuating gas towards the secondary piston, the latter descends from top dead center to bottom dead center; and likewise the tertiary piston descends, sucking in some of the gas that remained inside the feeder that would have made the last expansion.

[0053] And as for the valves, the general rule to apply is that only those strictly necessary should be opened, which is specified by identifying each valve or tap with the letter G followed in lowercase by the initials of the components that are assigned below, which are:

[0054] -a1 for the odd branch feeder

[0055] -a2 for the even branch feeder

[0056] -b for the main piston

[0057] -c for the secondary piston

[0058] -d for the tertiary piston

[0059] -e for heaters coming from the external hot source

[0060] -f for the coolers coming from the cold source, the components having the following functions in each of the four times,

[0061] From the table above, it can be indicated which valves or taps should be open at each time, and the others closed.

[0062] Time 1: Ga1 b; Gca2; Gda2; Gea1 ; Gfca2; Gfda2

[0063] Time 2; Gbc; Ga1d; Gea2; Gfbc; Gfald

[0064] Time 3: Ga2b; Gca1 ; Gda1 ; Gea2; Gfcal ; Gfdal

[0065] Time 4: Gbc; Ga2d; Gea1 ; Gfbc; Gfa2d And with that the operating mode of the motor is defined.

[0066] The invention preferably uses auxiliary equipment for filling the working gas, ideally argon. The circuit can be filled at several points, particularly the secondary and tertiary pistons, as well as the feeders, where there would also need to be a relief valve to empty or reduce the amount of argon in the closed circuit. This amount is very important for the performance of the invention, since as the density increases, dimensionless numbers, such as the Reynolds number, change, and this also changes the power transferred from the heat source to the motor of the invention, and ultimately, the motor's power output.

[0067] Two other auxiliary pieces of equipment that are very useful to complement the features are:

[0068] -the redefinition of the heating and cooling subsystems, so that the heat transferred to the engine is supplied by hot flows of a liquid, which in the first selection can be a thermal oil (reaching 400 e C).

[0069] As for the chillers, these can use water, practically at atmospheric pressure.

[0070] In both cases, the result is a reduction in the volume and contact area required for the transfer of a given heat power. That is, these intermediate circuits substantially improve the heat transfer rate, since heat generally appears with very low energy density, which implies very large volumes are needed to capture a significant portion of the residual energy that is to be harnessed. In general, it would be impossible, or very difficult, to build an engine of the dimensions required to capture a given power output. Introducing an intermediate liquid, such as synthetic oil, to transfer thermal power quickly and efficiently is a reality in today's technology, but in this case, it is a fundamental component that must be included in the assembly of the invention.The configuration of the heat exchanger that ultimately heats the working gas within the feeders can vary greatly in geometry and materials. It can range from a spherical casing, leaving an internal gap for the hot oil to pass around the outside of the feeder sphere, to a helical hose or pipe that enters and exits the feeder. Finally, for a proper understanding of this invention, it is important to note that the mechanical response of a fluid depends essentially on pressure, and specifically on its gradient, but not directly on temperature, although both quantities are related by the equation of state.

[0071] PV = NRT

[0072] Where P is the pressure, V the total volume to which the expression applies, N is the number of moles enclosed in that volume, and since it is measured in moles, R must be the universal gas constant, which is 8.35 J / mol·K, with T being the absolute temperature. Alternatively, N can be given in kg, in which case R must be in accordance with the SI system of units and must be expressed in J / kg·K. Specifically, for Argon, its atomic weight is 40, which means that there are 25 moles in 1 kg, so R will be 209 J / kg·K.

[0073] Temperature influences the pressure field, but it is not in itself a variable that induces acceleration in fluids, because thermal agitation occurs isotropically, and in statistical physics it is observed that the result of thermal agitation is zero motion. Therefore, the invention makes use of a very important property, which is the fact that the best way to generate pressure by increasing thermal energy is through rapid heating at constant volume, which is the function applied in the feeders of the invention.

[0074] The presented invention is defined by the description of its physical components, but this must be complemented by an explanation of the thermal phenomena that govern the movement of the working fluid through the circuit. This circulation is governed by the pressure distribution, and to create this distribution, it must be verified that the mass balance, or continuity equation, is satisfied; that the mechanical balance is satisfied, and therefore that the manometric pressure loss is compensated by the pressure supplied from the feeder; and that the enthalpy balance, typically expressed as the first law of thermodynamics, is satisfied.

[0075] The continuity equation states that, under steady-state conditions, in any control volume, real or ideal, identified in the circuit, the mass flow rate (in kg / s) entering the control volume is equal to the mass flow rate leaving it, since there are no rising points or sinks in the circuit. This holds true for steady-state conditions, but not for transients, particularly during startup and changes in the power applied externally and the power generated by the motor. In these cases, there are rising points or sources of working fluid, the content of which in the circuit must increase when the power output is to be increased.

[0076] What cannot increase is the temperature, as the temperature range is limited, above it by the external heat input, the most plausible hypothesis being a flue gas exhaust at constant temperature. However, the exhaust flow rate, in kg / s, can vary, depending on the operating conditions of the original exhaust source.

[0077] Therefore, the invented motor can operate with higher or lower working fluid pressure, allowing it to operate at higher or lower power levels, including during start-up and shutdown transients. This is illustrated in the following equation, representing the heat balance in a motor feeder:

[0078] QT = M T C v T f - T ¿ )

[0079] Where M TThis would be the total mass of the working fluid contained in the feeder (in kg) that can rise or fall depending on how the circuit charging device is operated, which is an auxiliary element of the motor, but essential for its correct operation, and which ensures that the feeder contains said mass M T , to which a total heat QT is applied, being C v its specific heat; T! the temperature at the start of heating, and T f the final temperature of that process.

[0080] This loading device will be connected to both feeders and consists of an ejection valve in each working fluid feeder. The outlet of this valve connects to a low-pressure reservoir, where the fluid is stored for a period of time until it is pumped to the high-pressure reservoir. From there, it can be injected into the feeder via a valve. Although all the aforementioned components are conventional, the Preferred Embodiment of the invention will present a novel feeder configuration with all the indicated valves plus a system for varying the working gas content.

[0081] Other important auxiliary elements are the coolers surrounding the working fluid transfer channels, but their specific design is not part of the invention, since cooling is an engineering function on which numerous treatises exist, and therefore there are many possible solutions for each specific case. Despite the existence of multiple solutions for the heat exchange stages, there is a procedural innovation directly linked to the invented engine, and it relates to its use according to the nature and circumstances of the external heat-carrying flow that is to be utilized.Since the motor operates on a 4-stroke cycle, and the working fluid is heated only during two of these strokes in each cycle, 50% of the available hot flow cannot transfer heat to any feeder in the installation and is therefore lost. This is unacceptable for a properly engineered installation, and it is 100% corrected by a usage specification that involves installing two motors, each handling 50% of the total available power. The motors are synchronized with each other but with a one-stroke offset, so that in a complete cycle, which is divided into 4 strokes, each stroke is unambiguously assigned to heat one of the four feeders, two for each motor.To achieve this, the external heat flow that is to be harnessed is divided into time intervals that coincide with the duration of one downward stroke of the main piston, and the external heat flow is alternately channeled to one engine or the other, and in turn, within each engine, it is alternately channeled to one feeder or the other. This is summarized in the following table, where A1 and A2 are the feeders for the first engine, and A3 and A4 for the second engine:

[0082] The operating method allows for a variation that can be applied to using a single engine to harness thermal energy from an external source. This variation is based on using an intermediate fluid, such as thermal oil, between the heat source and the engine's fuel lines. This is achieved using a heat exchanger that provides a stream of hot fluid, which can be stored in the required quantities. The necessary flow rates can then be sent to the fuel lines for heating, or none at all, if not required.

[0083] The invention is completed with mounting variants that allow for more precise compliance with the type of thermodynamic cycle on which it is based; and these variants refer, on the one hand, to constant volume heating, since in order to allow time for this heating, more than two feeders are provided, always in pairs, for example 4 in total instead of 2, and their operation follows a time multiplexing, extending the heating duration from the duration of one time of the main piston, to five times that duration.

[0084] The cooling performance, whether using air or water, is also improved by using a buffer tank containing the cooled working fluid, maintained at the lowest pressure and temperature in the circuit. Once the fluid has expanded, the feeders, as well as the main piston, send their contents to the intermediate tank. From there, after being acclimated to the minimum temperature and pressure of the cycle, the fluid is fed into the appropriate feeder.

[0085] Brief description of the figures

[0086] A figure is briefly described here as a non-limiting example, which helps to better understand the invention:

[0087] Figure 1: shows a schematic diagram of the main elements that make up the thermal engine, according to a first embodiment of the thermal engine that is the subject of the present invention.

[0088] Figure 2: Shows a schematic diagram of the heat engine from Figure 1, representing the operation of the heat engine during the first of the four strokes of its operating cycle. Figure 3: Shows a schematic diagram of the heat engine from Figure 1, representing the operation of the heat engine during the second of the four strokes of its operating cycle.

[0089] Figure 4: shows a schematic diagram of the heat engine from Figure 1, which represents the operation of the heat engine during the third of the four strokes of its operating cycle.

[0090] Figure 5: shows a schematic diagram of the heat engine from Figure 1, which represents the operation of the heat engine during the fourth and final time of its operating cycle.

[0091] Figure 6: shows a possible way of implementing the working fluid flow management system in the feeders.

[0092] Figure 7: schematically shows the thermodynamic evolution of the working fluid or gas throughout an operating cycle of the thermal engine, the object of the present invention.

[0093] Figure 8: shows a schematic diagram of the main elements that make up the thermal engine, according to a second embodiment of the thermal engine that is the subject of the present invention.

[0094] Figure 9: shows a schematic diagram of a possible variant of the thermal engine in Figure 8.

[0095] Detailed description Figure 1 shows a diagram that exposes all the relevant elements of the thermal engine, according to a first embodiment of the invention, where the ducts that connect the different elements of the thermal engine to each other are also shown.

[0096] Figure 2 represents the state of the heat engine during the cycle time chosen as the first. Feeder A1 is discharging onto the main piston plunger, B.

[0097] Figure 3 represents the state of the heat engine during the second phase of the cycle.

[0098] Figure 4 represents the state of the heat engine during the third phase of the cycle.

[0099] Figure 5 represents the state of the heat engine during the fourth time of the cycle.

[0100] Figure 6 shows a configuration of the working gas flow variation (or management) system in the feeders. Figure 6 illustrates, as an example, the management of the working fluid quantity in feeder A2.

[0101] Managing the amount of working fluid in the feeders is important for adapting the power of the heat engine to the availability of the heat source. This management system comprises a charging unit connected to the feeders and consists of an ejection valve (Z21) in each working fluid feeder. The outlet of this valve connects to a low-pressure reservoir (Z23), where the fluid is stored for a period of time until it is pumped (Z24) to the high-pressure reservoir (Z25). From there, it can flow to the feeder via an injection valve (Z26). When both valves are closed, no fluid flow occurs, neither charging nor discharging. The figures are labeled alphanumericly to allow for the precise identification of the components of each embodiment of the heat engine of the invention, which are governed by the following relationships:

[0102] A1: feeder of the odd branch

[0103] A2: even branch feeder

[0104] B: main piston

[0105] C: secondary piston

[0106] D: tertiary piston

[0107] E1: Heat input to the odd branch feeder, from the external source

[0108] E2: Heat input to the even branch feeder, from the external source

[0109] F1: cooler, which cools from the external cold source, located in the transfer duct from C to A1, said transfer being controlled by valve Gca1

[0110] F2: cooler, which cools from the external cold source, located in the transfer duct from C to A2, said transfer being controlled by valve Gca2

[0111] F3: cooler, which cools from the external cold source, located in the transfer duct from D to A1, said transfer being controlled by valve Gda1. F4: cooler, which cools from the external cold source, located in the transfer duct from D to A2, said transfer being controlled by valve Gda2.

[0112] F5: cooler, which cools from the external cold source, located in the transfer duct from A1 to D, said transfer being controlled by valve Ga1d

[0113] F6: cooler, which cools from the external cold source, located in the transfer duct from A2 to D, said transfer being controlled by valve Ga2d

[0114] F7: cooler, which cools from the external cold source, located in the transfer duct from B to C, said transfer being controlled by the Gbc valve

[0115] Gbc: valve that controls the flow of working gas from the main piston B to the secondary piston C

[0116] Ga1b: valve that controls the expanding gas discharge from feeder A1 to main piston B

[0117] Ga2b: valve that controls the expanding gas discharge from feeder A2 to main piston B

[0118] Ga1d: valve that controls the discharge from A1 drawn in by the tertiary piston, D

[0119] Ga2d: valve that controls the discharge from A2 sucked in by the tertiary piston, D

[0120] Gca1: valve that controls the load of A1 driven by the secondary piston, C

[0121] Gca2: valve that controls the load of A2 driven by the secondary piston, C. Gda1: valve that controls the load of A1 driven by the tertiary piston, D.

[0122] Gda2: valve that controls the load of A2 driven by the tertiary piston, D

[0123] In addition, the relevant elements of the heating system and mass flow management of the working fluid or gas (increase or decrease of its content) are represented and labeled as shown in Figure 6.

[0124] Figure 6 shows, as an example, feeder A2.

[0125] E2e: fluid inlet to heater A2

[0126] E2s: A2 heater fluid outlet

[0127] Z21: working gas extraction valve, from feeder A2

[0128] Z22: Low-pressure working gas tank

[0129] Z23: connection manifold between the low pressure tank and the high pressure tank.

[0130] Z24: compressor in connection manifold Z23

[0131] Z25: High-pressure working gas tank

[0132] Z26: Working gas injection valve in feeder A2. Figure 7 shows the thermodynamic evolution of the working gas throughout a cycle, and its analysis is essential, as it summarizes the physics of the invention. It should be noted first of all that the cycle only has three stages in this representation because the times can overlap by placing two of them, as will be explained below, subsequently, as the same effect in two subsequent times: one in the suction of working fluid by the secondary and tertiary pistons, and the other in the injection of this fluid into the corresponding feeder. This is represented by the linear isobars from point 2 to 3. This cooling isobar is intended to ensure that at point 3 the starting conditions of the preceding cycle are restored.

[0133] It's also important to consider that the stage from point 3 to 1 has a dual effect on the working fluid, as it compresses and heats it simultaneously. This is because constant-volume heating occurs in the feeder, and the pressure and temperature will evolve proportionally to each other. However, this also imposes limitations on the cycle, since the thermodynamic variables cannot be chosen arbitrarily. The cycle must close precisely, based on two boundary conditions: the highest and lowest achievable temperatures, designated T1 and T3, respectively.

[0134] To better explain the invention, the following table indicates the function performed by each component at a given time, of the four that successively make up a complete cycle of the mechanical movement of the motor, which corresponds to two complete revolutions. Figure 8 presents the second embodiment of the thermal engine of the invention in which, instead of having two feeders for a main cylinder, which is the minimum required, four are used, multiplexing their operation over time.

[0135] Figure 8 uses alphanumeric labels or references for the additional feeders, which include a tilde that in mathematics is read as "prime", and correspond to feeders A'1 and A'2.

[0136] Furthermore, the same accent mark is used on the valves that connect to these feeders, which also have heating systems E'1 and E'2 respectively. The valves shown in Figure 8 are:

[0137] Ga'1 b: valve that controls the expanding gas discharge from feeder A'1 to main piston B

[0138] Ga'2b: valve that controls the expanding gas discharge from feeder A'2 to main piston B

[0139] Ga'1d: valve that controls the discharge from A'1 drawn in by the tertiary piston, D

[0140] Ga'2d: valve that controls the discharge from A'2 sucked in by the tertiary piston, D

[0141] Gca'1: valve that controls the load of A'1 driven by the secondary piston, C

[0142] Gca'2: valve that controls the load of A'2 driven by the secondary piston, C

[0143] Gda'1: valve that controls the load of A'1 driven by the tertiary piston, D. Gda'2: valve that controls the load of A'2 driven by the tertiary piston, D.

[0144] The relevant elements of the heating system and management of the mass flow of the working gas (increase or decrease of its content) are those shown in Figure 6.

[0145] Figure 9 represents a variant of the thermal engine in Figure 8, where, in addition to eliminating the elements related to the cooling of the working fluid, a thermal inertia tank (H) has been incorporated. This tank stores the working fluid to reach the lowest possible temperature and pressure. From there, the fluid is injected at this temperature and pressure into the corresponding feeder. The equipment and component designation labels are:

[0146] H: intermediate inertia reservoir, low T and P

[0147] J: piston for loading the working fluid from reservoir H to the feeders

[0148] K: discharge piston of the feeders, and loading piston of the tank H

[0149] The new valves added are:

[0150] Gbh: valve that controls the discharge from the main piston to the tank H

[0151] Ghj: valve that controls the discharge from tank H to piston J

[0152] Gkh: valve that controls the discharge from piston K to tank H

[0153] Gja1: valve that controls the load from J to feeder A1 Gja' 1: valve that controls the load from J to feeder A'1

[0154] Gja2: valve that controls the load from J to feeder A2

[0155] Gja'2: valve that controls the load from J to feeder A'2

[0156] Gal k: valve that controls the discharge from feeder A1 to piston K

[0157] Ga'1 k: valve that controls the discharge from feeder A'1 to piston K

[0158] Ga2k: valve that controls the discharge from feeder A2 to piston K

[0159] Ga'2k: valve that controls the discharge from feeder A'2 to piston K

[0160] The operation of the thermal engine of the invention is described below, according to a preferred mode.

[0161] First and foremost, a thermodynamic invention must demonstrate its feasibility, meaning that it is not flawed by arguments that violate the principles and laws of this science. This is achieved by representing its cycle on a Cartesian pressure-volume diagram, as shown in Figure 7. Furthermore, certain parameters are used to adequately characterize the cycle.

[0162] The Carnot factor T is defined as the quotient: Thus, in the relief heating stage, PI=TP3 is also present. This implies that the final pressure P2 of the expansion cannot be less than P3, as a mechanical compressor would be needed to recover the P3 level, which is essential to close the cycle. This is not included in the invention. The ideal minimum value of P2 would be exactly P3, but in reality, the transition from the end of the expansion to the beginning of the relief heating stage requires a certain pressure drop. Therefore, in a more realistic representation, the end of the expansion would not reach point 2, but would stop at 2'. This would provide the small pressure gradient that would help the working fluid pass through the secondary and tertiary pistons to fill the feeder that will undergo the relief heating stage.

[0163] The expansion of the heated gas occurs against what can be considered a movable wall, against which the force of pressure is applied. This pressure must be greater than the pressure that must be overcome to displace the piston. The expansion phase can be carried out in different ways, beginning with a very common transformation, the adiabatic one, which is governed by the following expression, relating Pressure P and Specific Volume.

[0164] V and the ratio between specific heats at constant pressure and volume, and:

[0165] PF 7 = constant

[0166] And in which there is no heat input. On the contrary, if there is an input, the expansion would resemble an isotherm, with the equation PV=constant.

[0167] There could be intermediate situations, where heat is added, but less than in the isotherm. In general, the expansion can be studied using the polytropic approximation, where the exponent q in the equation:

[0168] PV q = constant can vary from 1 for the isotherm to y for the adiabatic.

[0169] The relationship between pressure and temperature is With this formulation, the following relationships are obtained for Work, W; and heat transferred, Q, all expressed in specific magnitudes (per unit mass):

[0170] For heating at constant volume, the equation is:

[0171] Q = C V T1— T2')

[0172] Note that an isochore is a polytropic with q tending to infinity.

[0173] In general terms, one can write:

[0174] Q = C q (T1- T2)

[0175] For adiabatic expansion C q is zero, and for the isotherm (q=1) it becomes infinite, because being an isotherm, T cannot change, which mathematically requires going to infinity with the supplied energy. For an isochore, where q is infinite, C q is equal to C v .

[0176] Note that between q=1 and q=y the value of C q It is negative, because the working fluid effectively loses part of its internal energy to expand, doing work.

[0177] Using the equations above, we can find the efficiency of this engine, which converts the waste heat used to heat the feeders into mechanical energy. To do this, we first use the most common assumption, which is adiabatic, and apply it to argon, which is monatomic, and therefore has a coefficient of γ=5 / 3.

[0178] Starting from T, already defined, 0 is defined, which is the ratio of temperatures in the expansion: Applying the First Law to an adiabatic expansion, the work done outwards is equal to the loss of internal energy, that is:

[0179] And the heat supplied from the external source in a constant volume heating is:

[0180] Q = C V (T1- T3)

[0181] Efficiency here is understood as the fraction of original (waste) heat that is converted into mechanical energy. Or more precisely, it is defined as the maximum energy that can be transferred to the connecting rod of the main piston, relative to the amount of thermal energy it has received from the heat source. That is, the mechanical effect that can actually be absorbed by the crankshaft, which in turn depends on the resisting torque attempting to slow it down, is not taken into account. Nor is the heat that must be removed by the cold reservoir considered, as this has no price or immediate limitations. The efficiency is therefore:

[0182] The following table shows the efficiency value in a fully idealized, loss-free cycle of a monatomic ideal gas:

[0183] T 1.5 1.75 2 2.25 2.5

[0184] 0 1 ,18 1 ,25 1 ,32 1 ,38 1 ,44

[0185] £ 0.449 0.468 0.484 0.499 0.511

[0186] The most striking feature of this table is the minimal variation in efficiency when the ratio between the maximum and minimum temperatures decreases significantly. Note that the Carnot efficiency is (T-1) / T, a factor that appears in the equation for E, and which can be less than E. In fact, the Carnot efficiency for T=1.5 is 0.33; however, these are not directly comparable, as the Carnot efficiency considers the cold reservoir, while the Carnot efficiency does not, due to the heat recovery nature of this invention. In any case, it is very interesting that the value of E remains high even as T decreases. This is fundamental for utilizing the exhaust of hot fluids at relatively low temperatures. The explanation for this lies in the fact that the triangular shape of the cycle maintains a certain self-similarity as its size decreases, essentially by reducing T.

[0187] The preceding equations are generally applicable, but logically, the actual sizing of the cycle components must take into account other branches of engineering, such as fluid mechanics, to calculate transfer velocities and other factors, strength of materials, valve actuation, etc. A methodology for sizing the cycle, its components, and their connections is presented below, using an example.

[0188] As a working hypothesis, it will be considered that T3=300 K and Ti=600 K, and that argon is used as the working gas, for which R=209 J / kg-K and therefore C v =314 J / kg-K. It will also be assumed that the external hot flow captured by the engine (by its feeders) is 100 kW, so that in the emergency heating we have:

[0189] (kg\ 100,000 100,000 m — = 777 - 777 = „ nn = 1.06 kg / s

[0190] \ s / — * 3) 14 • 300

[0191] The total mass is a function of the total length of the circuit and the chosen speed for the various phenomena involved. For example, the pistons of internal combustion engines move during each stroke at an average speed of between 10 and 12 m / s. If a cylinder with a stroke length equal to its diameter is chosen, its volume will be TTD 3 / 4, If a slow design is chosen to ensure more reliable heat transfer, and the speed is set at 1,000 rpm, each revolution, which consists of two strokes, will last 0.06 s. Therefore, the stroke length of D meters will be determined by the average cylinder speed. Values ​​for internal combustion engines were given earlier, but this invention uses lower speeds, for example, 2 m / s. In this case, D = 0.03 - 2 = 0.06 m (6 cm), and the volume would be 0.000678 m³ 3 That is, 0.678 liters, and the identified mass, 1.06 kg, should fit in that volume.

[0192] An underlying hypothesis in the description and implementation of the invention is that the time required for heat transfer in a given stage of the thermodynamic cycle is on the order of the time imposed by mechanical action. This is generally not true, as the transmission rate associated with thermal diffusivity is much lower than the mechanical rate due to the pressure gradient to which the system is subjected. Furthermore, the convection films on either side of the (usually metallic) wall through which heat transfer occurs introduce a time delay that makes rapid heating impossible unless a large temperature difference is maintained between the hot and cold fluids. However, even if this is done, the temperature reached in the cold fluid remains well below the maximum temperature of the hot fluid.

[0193] In summary, it is necessary to find an assembly of the heat engine of the invention that provides more time for heating, which is achieved by increasing the number of feeders working with a main cylinder and by temporally multiplexing them, so that the working fluid, in the actual cycle, spends more time being heated by the fluid coming from the outside than expanding in the cylinder. This assembly of the heat engine of the invention is shown in Figure 8 for the case of two additional feeders.

[0194] For a proper explanation of the time multiplexing of the feeders, the following table indicates the activity of each main component of the engine, whose fundamental part in terms of the work performed is piston B. Each row of the table represents a time of the engine, in which piston B is either undergoing an expansion, and therefore performing work, or is rising towards its top dead center, emptying the remains of the expansion into the secondary piston C.

[0195] The following abbreviations are used in the table:

[0196] Cal: heating at constant volume

[0197] Exp: expansion

[0198] BaC: transfer from B to C aX: load from the component of said column to feeder X (where X can be A1, A'1, A2, A'2)

[0199] Full: the feeder is full at the end of that time (thanks to what is received from C and D) aD: transfer from the feeder that corresponds to that column to the tertiary piston D. dX: it is filled from the transfer from X It must be emphasized that all ducts leading from or to the secondary piston C must be cooled, and likewise all ducts leading from or to the tertiary piston D must be cooled; and similarly, all heating ducts of all feeders must always be heating them, for which reason references to these valves have been removed from the drawings and operating instructions, as they have no role during operation (they are always open).

[0200] The following table specifies which valves must be open during each cycle, marked with A; the others are closed, to achieve the operation described in the previous table. In the table presented here, only 8 cycles are shown because, with the assembly used in the second embodiment of the invention, corresponding to Figure 8, the valve specifications are repeated cyclically, every 8 cycles.

[0201] To materialize the thermal engine of the invention, it is necessary to have the elements that compose it, which are several feeders, all of the same size, and all equipped with the mechanism to increase or reduce the amount of working fluid that fills the circuit, which obviously has its impact on the total power of the system.

[0202] The volume of the piston cylinders must be adjusted according to the anticipated ratios between the extreme cycle temperatures, which are the values ​​of T1 and T3 in Figure 7, plus the value of T2. In the ideal cycle, T2 is calculated from the pressure at the end of the expansion, which can be assumed to be adiabatic as a first approximation if a more precise polytropic coefficient is not available. The following equations apply. And for point 2, we have

[0203] P2= Ps

[0204] Where Vi is the volume of the fueled fluid and V2 is the volume of this fluid plus the volume of the piston cylinder. Thus, the volume of B would be V2 - Vi.

[0205] The volume of secondary piston C would be equal to (or very similar to) that of B; while the volume of tertiary piston D would be equal to or greater than that of the feeder, as it has to empty it after expansion, once the feeder connection valve (whichever is appropriate) has been closed to the main piston B. During the process of emptying the fluid that remained in the feeder into D, it is cooled. This can be achieved using the hydraulic connection pipe(s) from the feeder to piston D, and vice versa, because the purpose of this dual function—emptying and refilling—is to return the fluid to its starting condition for the cycle, allowing the feeder to absorb the amount of heat required for operation. This depends on the available cold source, but the physics involved follows the thermal evolution patterns described here.

[0206] Regarding the variant in Figure 9, with respect to the cold focus, in order to approximate as closely as possible the thermodynamic cycle followed by this invention, it includes a thermal inertia reservoir in which working fluid is stored at the minimum pressure and temperature values ​​required by the cycle. There is also a complementary piston, J, which provides the successive charging of the feeders, starting from the inertia reservoir, H, which is filled with the discharge from the main piston B, plus the discharges from the feeders, channeled by a second complementary piston, K. This ensures the appropriate flow of working fluid, and mechanical energy is also obtained through the expansions of the main piston. The opening and closing of valves is controlled to allow the passage of working fluid exclusively through the corresponding ports for each stage. Thus, for an engine with 4 feeders, the valves in this assembly are as follows:

[0207] Gbh; valve that controls the discharge from the main piston to the tank H

[0208] Ghj: valve that controls the discharge from tank H to piston J

[0209] Gkh: valve that controls the discharge from piston K to tank H Gja1: valve that controls the loading from J to feeder A1

[0210] Gja'1: valve that controls the load from J to feeder A'1

[0211] Gja2: valve that controls the load from J to feeder A2

[0212] Gja'2: valve that controls the load from J to feeder A'2

[0213] Gal k: valve that controls the discharge from feeder A1 to piston K

[0214] Ga'1 k: valve that controls the discharge from feeder A'1 to piston K

[0215] Ga2k: valve that controls the discharge from feeder A2 to piston K

[0216] Ga'2k: valve that controls the discharge from feeder A'2 to piston K. The following table shows the operating requirements, given as a function of the opening states, which are identified by A, with the valves being closed the rest of the time not corresponding to A. With the given valve arrangement, the sequence of times shown in the following table is obtained:

[0217] Once the invention has been clearly described, it is noted that the particular embodiments described above are subject to minor modifications provided they do not alter the fundamental principle and essence of the invention.

Claims

CLAIMS 1. A heat engine characterized in that it comprises a plurality of elements forming a closed circuit of a working fluid, wherein the heat engine comprises: - at least a first feeder (A1) comprising a sealed container for the working fluid, wherein the first feeder (A1) is located in a first branch of the closed circuit of the working fluid, and has controlled opening valves; - at least a second feeder (A2) comprising a sealed container for the working fluid, wherein the second feeder (A2) is located in a second branch of the closed circuit of the working fluid and has controlled opening valves; - a main piston (B) located in correspondence with a main cylinder, where the main piston (B) is connected to a shaft of the heat engine by means of a connecting rod and crankshaft; where the main piston (B) is configured to move, in each operating cycle of the heat engine, at least twice in the compression direction in the main cylinder and at least twice in the expansion direction in the main cylinder, and where the main cylinder is configured to: either be filled with working fluid taken alternately from at least a first feeder (A1) and from at least a second feeder (A2) on each expansion stroke of the main piston (B), through the corresponding valve; and either expel working fluid on each compression stroke of the main piston (B), sending said working fluid to a secondary cylinder through the corresponding valve; - a secondary piston (C) located in correspondence with the secondary cylinder, wherein the secondary piston (C) is configured to move, in each cycle of the operation of the heat engine, at least twice in the compression direction in the secondary cylinder and at least twice in the expansion direction in the secondary cylinder; wherein the secondary piston (C) is configured to move in the expansion direction when the main piston (B) moves in the compression direction and vice versa, wherein the secondary cylinder is configured to: either be filled with working fluid taken from the main cylinder on each expansion stroke of the secondary piston (C), through the valve existing for that purpose; and either expel working fluid on each compression stroke of the secondary piston (C), sending said working fluid to a feeder (A1, A2) through the valve existing for that purpose; - a tertiary piston (D) located in correspondence with a tertiary cylinder, where the tertiary piston (D) is configured to move, in each operating cycle of the heat engine, at least twice in the compression direction in the tertiary cylinder and at least twice in the expansion direction in the tertiary cylinder; where the tertiary piston (D) is configured to move in the expansion direction when the main piston (B) moves in the compression direction and vice versa, where the tertiary cylinder is configured to: either be filled with working fluid taken from a feeder (A1, A2) on each expansion stroke of the tertiary piston (D), and; or expel working fluid on each compression stroke of the tertiary piston (D), sending said working fluid to a feeder (A1, A2).where the feeders (A1, A2) are configured so that, within them, the working fluid is heated by the heat received from an external heat transfer fluid.

2. Thermal engine according to claim 1, characterized in that the thermal engine comprises only two feeders (A1, A2), where: - the main piston (B) is configured to move, in each operating cycle of the heat engine, twice in the compression direction in the main cylinder and twice in the expansion direction in the main cylinder; such that: either in a first compression and expansion sub-cycle of the main piston (B), during the expansion movement of the main piston (B), the main cylinder is configured to be connected to the first feeder (A1) by opening a discharge valve of the first feeder (Ga1 b), and; or in a second compression and expansion sub-cycle of the main piston (B), during the expansion movement of the main piston (B), the main cylinder is configured to be connected to the second feeder (A2) by opening a discharge valve of the second feeder (Ga2b); or in the first sub-cycle and in the second sub-cycle of compression and expansion of the main piston (B), during the compression movement of the main piston (B), the main cylinder is configured to be connected to the secondary cylinder by opening a bypass valve (Gbc); - the secondary piston (C) is configured to move, in each operating cycle of the heat engine, twice in the compression direction in the secondary cylinder and twice in the expansion direction in the secondary cylinder, such that: or in a first compression and expansion sub-cycle of the secondary piston (C): ■ During the compression stroke of the secondary piston (C), the secondary cylinder is configured to be connected to the second feeder (A2) by opening a second charging valve (Gca2), and; ■ During the expansion movement of the secondary piston (C), the secondary cylinder is configured to be connected to the main cylinder by opening the bypass valve (Gbc), and; or in a second sub-cycle of compression and expansion of the secondary piston (C): ■ During the compression stroke of the secondary piston (C), the secondary cylinder is configured to be connected to the first (A1) by opening a first charging valve (Gca1), and; ■ During the expansion movement of the secondary piston (C), the secondary cylinder is configured to be connected to the main cylinder by opening the bypass valve (Gbc); - the tertiary piston (D) is configured to move, in each operating cycle of the heat engine, twice in the compression direction in the tertiary cylinder and twice in the expansion direction in the tertiary cylinder, such that: or in a first compression and expansion sub-cycle of the tertiary piston (D): ■ During the compression stroke of the tertiary piston (D), the tertiary cylinder is configured to be connected to the second feeder (A2) by opening a fourth charging valve (Gda2), and; ■ During the expansion movement of the tertiary piston (D), the tertiary cylinder is configured to be connected to the first feeder (A1) by opening a first suction valve (Ga1 d), and; or in a second sub-cycle of compression and expansion of the tertiary piston (D): ■ During the compression stroke of the tertiary piston (D), the tertiary cylinder is configured to be connected to the first feeder (A1) by opening a third charging valve (Gda1), and; ■ During the expansion movement of the tertiary piston (D), the tertiary cylinder is configured to be connected to the second feeder (A2) by opening a second suction valve (Ga2d).

3. Thermal engine according to claim 1, characterized in that it comprises: - at least a third feeder (A'1) located in the first branch of the closed circuit of the working fluid; - at least a fourth feeder (A'2) located in the second branch of the closed circuit of the working fluid; where the heat engine is configured to: - multiplex the actuation of the valves that connect each feeder (A1, A'1, A2, A'2) to the main cylinder during the expansion movements of the main piston (B); - multiplex the actuation of the valves that connect each feeder (A1, A'1, A2, A'2) to the secondary cylinder during the compression movements of the secondary piston (C); - Multiplex the actuation of the valves that connect each feeder (A1, A'1, A2, A'2) to the tertiary cylinder during the compression and expansion movements of the tertiary piston (D).

4. A heat engine according to any of claims 1 to 3, characterized in that there are coolers surrounding the working fluid transfer ducts, and all ducts leading from or to the secondary piston C must be cooled, and likewise all ducts leading from the tertiary piston D or They arrive at D and must be cooled; and likewise the feeders will be heated externally by the hot external fluid.

5. Thermal engine according to any of the preceding claims, characterized in that it comprises a working fluid flow management system in the feeders (A1, A'1, A2, A'2).

6. Thermal engine according to claim 5, characterized in that the working fluid flow management system in the feeders (A1, A'1, A2, A'2) comprises a charging apparatus connected to the feeders (A1, A'1, A2, A'2), wherein said charging apparatus comprises: - an ejection valve (Z21) in each working fluid feeder (A1, A'1, A2, A'2), whose outlet communicates with a low-pressure reservoir (Z23), configured to store said working fluid for a period of time; - a pump (Z24) configured to pump and pressurize the working fluid from the low-pressure reservoir (Z23) to a high-pressure reservoir (Z25), and; - an injection valve (Z26), configured to control the passage of the working fluid from the high pressure reservoir (Z25) to the corresponding feeder (A1, A'1, A2, A'2).

7. Thermal engine according to claim 2, characterized in that the accuracy in the execution of the cycle is achieved by the synchronization in the movement of the piston plungers, and the openings and closings of the various valves that regulate the passage from one component to another, and as regards the synchronization between pistons, it should be noted that as the main piston descends, in the expansion, from its top dead center to its bottom dead center, the secondary and tertiary pistons move in an intrinsically opposite direction, each from its bottom dead center to its top dead center; and vice versa when the main piston rises from its bottom dead center to its top dead center, and is evacuating gas towards the secondary piston, the latter is descending from the top dead center to the bottom dead center; and likewise the tertiary piston descends, sucking in part of the gas that has remained inside the feeder that would have made the last expansion;This is complemented, with regard to the valves, by the general rule to be applied, which is that only those strictly necessary should be opened, which is specified by identifying; each valve or tap by the letter G followed in lowercase by the initials of the components that are assigned below, which are -a1 for the odd branch feeder -a2 for the even branch feeder -b for the main piston -c for the secondary piston -d for the tertiary piston -e for heaters coming from the external hot source -f for the coolers coming from the cold source, the components having the following functions in each of the four times, indicating that the valves that must be open at each time, and the others closed, are the following: Time 1: Ga1 b; Gca2; Gda2; Gea1 ; Gfca2; Gfda2 Time 2; Gbc; Ga1 d; Gea2; Gfbc; Gfal d Time 3: Ga2b; Gca1 ; Gda1 ; Gea2; Gfcal ; Gfdal Time 4: Gbc; Ga2d; Gea1 ; Gfbc; Gfa2d 8. A heat engine according to the preceding claims, characterized in that the external heat flow to be utilized is temporarily divided into time intervals that coincide with the duration of a downward stroke of the main piston, and the external heat flow is alternately channeled to one or the other engine, and in turn, within each engine, it is alternately channeled to one or the other feeder, the engines being synchronized with each other but with a time offset, such that in a complete cycle, which is divided into 4 strokes, each of these is unambiguously assigned to heat one feeder, of which there are 4, two from each engine, In the following table, feeders A1 and A2 correspond to one motor, and feeders A3 and A4 to the other motor.

9. A heat engine according to the preceding claims, characterized in that the cooling flow necessary to cool the working fluid in the corresponding part of the cycle is constituted by a thermal inertia reservoir in which working fluid is stored at the minimum pressure and temperature values ​​required by the cycle, there also being a complementary piston, J, which provides the successive charging of the feeders, from the inertia reservoir, H, which is filled with the discharge from the main piston B, plus the discharges from the feeders, channeled by a second complementary piston, K, obtaining the appropriate flow of the working fluid, and also obtaining mechanical energy by the expansions of the main piston, according to the times in the following table For this purpose, all valves must be kept closed, except those marked with A at each time in the following table, which must be open.

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