Liquid piston quasi-isothermal compression and / or expansion system with rotary heat exchanger

Abstract

The invention relates to a system for the substantially quasi-isothermal compression and / or expansion of a gas, comprising at least one cylinder containing a liquid introduced and extracted during a cycle, the liquid acting as a liquid piston, and a rotary heat exchanger arranged inside the cylinder. The exchanger is designed to be immersed in the liquid during a part of the cycle in order to be brought substantially to the temperature of the liquid, then to emerge and be rotated so as to agitate the gas, expel the residual liquid by centrifugal force and promote rapid heat transfer. The system may be associated with a variable-delivery positive displacement pumping device capable of modulating the flow rate of the liquid depending on the pressure of the gas.

Description

[0001] TITLE OF THE INVENTION: QUAS-ISOTHERMAL LIQUID PISTON COMPRESSION AND / OR EXPANSION SYSTEM WITH ROTARY HEAT EXCHANGER

[0002] This patent relates to an isothermal liquid piston compression and expansion system designed to improve the efficiency of energy storage and conversion. It integrates particularly well with cryogenic storage technologies for liquid air and other fluids, which offer a dense and economical solution for large-scale energy storage. The key innovation lies in a rotary heat exchanger immersed in a compression and / or expansion liquid, which is rapidly drained by centrifugal force with each cycle. This instantaneous draining enables:

[0003] "Rapid cylinder filling in compression mode."

[0004] "A complete gas expansion in decompression mode."

[0005] • A reduction in cycle time, while ensuring near-isothermal compression and expansion.

[0006] This architecture significantly improves energy efficiency and increases the number of cycles per hour, a key factor for industrial energy storage applications.

[0007] Differentiation from existing patents: Conventional compression and expansion systems suffer from long cycle times, primarily due to:

[0008] "A slow evacuation of the thermal fluid in the fixed exchangers."

[0009] "Insufficient thermal convection, limiting heat dissipation."

[0010] The invention overcomes these limitations thanks to a rotary heat exchanger, optimizing both the management of the thermal fluid and the heat exchange:

[0011] 1. Instantaneous drainage by centrifugal force:

[0012] o During compression: the heat exchanger quickly empties of the thermal fluid, ensuring optimal cylinder filling,

[0013] o During expansion: the exchanger is completely purged of residual fluid, allowing for complete gas expansion and a rapid transition to the next cycle.

[0014] 2. Reduction of cycle time:

[0015] o Rapid purging accelerates heat transfer, reducing the duration of the compression and expansion phases.

[0016] o The rotary heat exchanger actively stirs the gas, stabilizing the temperature and optimizing heat exchange,

[0017] 3. Near-isothermal compression and expansion:

[0018] Unlike systems with static heat exchangers, the rotary heat exchanger maximizes the heat exchange surface area, reduces losses, and improves energy efficiency. Operation

[0019] Isothermal Compression Mode. The compression fluid is cooled by the cylinder walls throughout the cycle, either by its level in the cylinder or by being projected against the walls by the rotary heat exchanger. 1. Cylinder Draining - Gas Intake

[0020] • The pump evacuates the compression fluid while the intake valve (111) (fig.1) opens, allowing gas to enter the cylinder (110).

[0021] ® When the compression fluid level falls below the heat exchanger, the latter starts to rotate and expels the residual compression fluid almost instantly by centrifugal force, carrying away with it the heat accumulated during the previous cycle.

[0022] 2. Cylinder filling - Gas compression - Exhaust

[0023] "The pump (107), powered by energy, gradually injects the compression fluid with a controlled flow rate, thus reducing the volume of the gas and increasing its pressure, while the heat exchanger is rotating.

[0024] ® The rotary heat exchanger (102) stirs the gas inside the cylinder, absorbs the heat generated by compression and transfers it to the compression fluid injected within it. "When the level of the compression fluid reaches the base of the heat exchanger, it stops rotating.

[0025] • When the desired pressure is reached, the exhaust valve opens to release the compressed gas until the cylinder is completely filled. At this point, the heat exchanger is completely flooded and finishes cooling.

[0026] Isothermal Expansion Mode (System Reversibility). An external heat exchanger heats the expansion fluid inside the cylinder by transferring heat through its walls. This maintains the fluid at an optimal temperature throughout the cycle, depending on its level and when it is projected against the cylinder walls.

[0027] 1. Compressed gas admission - Gas expansion

[0028] “At the beginning of the cycle, the cylinder is completely filled with expansion fluid.

[0029] • The intake valve (formerly the exhaust valve in compression mode) opens, allowing compressed gas to enter the cylinder (110), while another valve opens simultaneously to gradually evacuate the expansion fluid to a hydraulic motor.

[0030] "Once the amount of gas injected reaches the required value in the cylinder, the intake valve closes and the gas begins to expand.

[0031] ® As soon as the heat exchanger begins to emerge from the expansion fluid, it starts rotating to optimize heat transfer and preheat the expanding gas. Simultaneously, expansion fluid is injected into it to further enhance heat transfer.

[0032] "When the cylinder is empty and the gas is completely expanded, the cycle reverses.

[0033] 2. Escape of the expanded gas and preparation for the next cycle

[0034] ® The exhaust valve opens, allowing the expanded gas to exit the cylinder, while the expansion fluid is gradually reintroduced.

[0035] "When the level of the expansion fluid reaches the base of the heat exchanger, it stops rotating.

[0036] ® Once the cylinder is completely filled, the cycle reverses and a new cycle begins. State of the art: Limitations of existing technologies and proposed solution. The rotary heat exchanger, integrated into the cylinder, optimizes heat transfer by combining forced convection, heat dissipation, gas mixing, and rapid removal of the liquid inside. The dynamic thermal management mechanism is in two phases:

[0037] • OIE cooling: gradual and isothermal heating thanks to total immersion in the thermal fluid.

[0038] * Rapid drainage under the effect of centrifugal force from the moment of emergence or submersion guaranteeing the possibility of using a heat exchanger with a large exchange surface for a small volume and a stabilized heat exchange before each cycle.

[0039] This approach enables near-isothermal compression and expansion operation, minimizing thermodynamic losses and significantly increasing efficiency. Unlike existing systems, which rely on a fixed heat exchanger or a simple stirrer, it ensures dynamic mixing with a large exchange surface area in both compression and expansion modes.

[0040] Limitations of existing technologies: Current compression and expansion systems suffer from several limitations:

[0041] ® Fixed heat exchanger: Offers a large exchange surface, but its efficiency is reduced by the slow evacuation of the liquid and limited thermal convection.

[0042] • Mechanical stirrer: Improves convection with the cylinder, but its reduced exchange surface limits its performance.

[0043] "Microdroplet spraying: Offers good thermal performance, but its high energy cost makes its industrial application difficult.

[0044] Proposed solution: Rotary heat exchanger with dynamic thermal management. The innovation is based on adaptive operation depending on the compression or expansion mode:

[0045] "In compression mode: The compression fluid is injected into its center as a controlled jet, ensuring active cooling. The exchanger combines dynamic mixing, thermal absorption and rapid fluid removal at the end of the cycle to stabilize the gas temperature and maintain near-isothermal compression."

[0046] • In expansion mode: The expansion fluid is gradually injected into the heat exchanger, where it transfers its heat to the expanding gas. It is heated by an external heat exchanger attached to the cylinder walls, ensuring a near-isothermal expansion.

[0047] Thanks to this dynamic thermal management, the system optimizes both gas compression and expansion, offering improved efficiency for energy storage via liquid air, as well as for compressing high-pressure gases such as hydrogen. Its large heat exchange surface and active mixing maximize heat transfer, thus increasing the efficiency of the energy storage and release cycle.

[0048] The rotary heat exchanger does not function as a heat exchanger between two separate gas flows, but as a dynamic thermal regulator that stabilizes the gas temperature during pressure changes. Unlike conventional external cooling or heating systems, this integrated exchanger absorbs heat from the gas during compression and releases heat during expansion. It thus ensures near-instantaneous thermal regulation, minimizing temperature fluctuations during pressure variations and improving the system's energy efficiency. Specific thermal conditions of the system

[0049] "The average pressure of the gas (e.g. 50 bars) increases the density of the gaseous fluid, thus improving thermal convection.

[0050] ® At lower pressures (~8 bars), a larger volume is available, allowing the exchange surface area of ​​the exchanger to be increased.

[0051] ® A rotary heat exchanger can achieve a heat transfer coefficient of 300 to 600 W / m 2 .K, depending on the rotation speed and the flow rate of the compression or expansion fluid.

[0052] The heat exchanger

[0053] The heat exchanger is positioned at the center of the compression cylinder, held in place by a device ensuring precise alignment and smooth rotation. Its active cooling is achieved by a controlled injection of compression fluid, delivered to its center via the central shaft (112) or any equivalent device. The compression and / or expansion fluid can be introduced into the exchanger in a form that promotes dispersion, such as a jet, a liquid film, or fine droplets, in order to increase the thermal contact surface between the fluid, the exchanger, and the gas, and to improve heat transfer. This fluid is then expelled by centrifugal force. The fluid may be temporarily retained within the exchanger before expulsion, promoting rapid and efficient heat exchange.Its surface is designed to maximize heat transfer by convection, thanks to structures such as louvers, fins, or embossed patterns that disrupt the airflow and improve heat dissipation. It must offer a large heat exchange surface area for a small volume, while having sufficient thermal capacity to efficiently absorb and transfer heat.

[0054] The heat exchanger has a cylindrical shape with a central or offset recess, allowing for the smooth circulation of gases and liquids. It can be made of stacked discs with vertical structures similar to those of a centrifugal pump turbine, to quickly expel the liquid from the exchanger for a new cycle. Another possible design consists of stamped aluminum circular plates stacked with a spacing of less than 1 mm, thus increasing the exchange surface area and the turbulence of the internal flows. To ensure continuous heat exchange, the exchanger can be segmented into several stacked and independent sections. When a lower section is immersed in the compression fluid, the upper section continues to operate, thus guaranteeing efficient heat exchange throughout the cycle, in both compression and expansion modes.

[0055] Exchanger drive modes

[0056] The rotation of the exchanger (102) is ensured by drive means arranged to set it in rotation at least when it emerges from the liquid, in order to stir the gas and expel the residual liquid by centrifugal effect.

[0057] • Magnetic field: The rotation of the exchanger sections, which have magnets fixed to their periphery, is ensured without contact via a magnetic field generated by electromagnets external to the cylinder. This configuration is the simplest when the exchanger consists of several sections rotating at different speeds, as it allows independent motion transmission without mechanical linkage.

[0058] Magnetic coupling: The heat exchanger can be rotated by the central axis (112) via a magnetic coupling located at the top of the cylinder. If the heat exchanger is composed of several independent sections rotating at different speeds, the transmission of motion becomes more complex. It is then possible to nest several coaxial axes, each coupled to a specific section of the heat exchanger. In either of these transmission methods, it is also possible to integrate a disengagement system for the lower sections. This mechanism would allow the lower sections to be driven without the need for independent motorization. The upper section would drive the lower section, and so on, ensuring a progressive transmission of motion while simplifying the management of speed and mechanical power.

[0059] The system is designed to operate in compression and expansion in a near-isothermal regime, requiring temperature control of both the gas and the liquid during the different phases of the cycle. During the compression phase, the heat generated by the gas compression is transferred to the compression liquid to limit the gas temperature rise. During the expansion phase, heat is supplied to the expanding gas via the expansion liquid to limit its cooling and maintain near-isothermal operation.

[0060] The compression and expansion fluids can be identical and circulate cyclically between the compression and expansion phases, ensuring efficient heat exchange during operation. To limit thermal drift of the fluid during successive cycles, the system can include heat exchange means located outside the cylinder, configured to remove or supply heat to the fluid depending on the operating phase, so as to maintain the gas compression and / or expansion phases in a substantially quasi-isothermal regime.

[0061] The compression fluid injection pump operates at variable flow rate, dynamically adjusted according to the compression cycles.

[0062] “At the beginning of the cycle, when the pressure in the cylinder is low, a higher flow rate allows for rapid filling and a gradual pressure increase.

[0063] "As compression progresses, and internal pressure increases, the flow rate is gradually reduced in order to maintain continuous compression power and avoid energy consumption peaks.

[0064] Conversely, during the expansion of the compressed gas, a hydraulic motor is used to recover the stored energy:

[0065] "At the beginning of expansion, when the gas pressure is at its maximum, a higher flow rate maximizes energy conversion.

[0066] “As the expansion progresses, the flow rate is gradually reduced, ensuring a stable and continuous energy conversion.

[0067] This dynamic flow rate control, in both compression and expansion, ensures stable operation, continuous power delivery despite relatively long cycles, and optimized integration into industrial applications requiring a regulated energy flow. The variable-flow pump and motor can be implemented as a single reversible unit, alternately performing both functions. The compression / expansion fluid can be water, treated water, an aqueous solution (e.g., glycol water), or any other fluid compatible with the materials and operating conditions.

[0068] The flow profiles described above require a volumetric device capable of modulating the stroke (and therefore the flow rate) according to the gas pressure, while maintaining a substantially constant drive speed and limiting mechanical losses. In a preferred mode, this modulation is achieved by a pumping / motor device with a movable pivot and stroke control, capable of maintaining a substantially constant torque and / or power during the compression and expansion phases. Such a device is described below and can be implemented independently, or in combination with the rotary heat exchanger, depending on the intended applications. Variable flow pumping subsystem: volumetric device with movable pivot and stroke control

[0069] The invention relates to a volumetric device for pumping, compressing, or motorizing a fluid, particularly for gas compression / expansion cycles (air, nitrogen, etc.) in isothermal or cryogenic processes. The device aims to maintain a substantially constant power and / or torque despite significant pressure variations by modulating the stroke of a piston with a substantially constant oscillation frequency.

[0070] Technical problem

[0071] In traditional positive displacement pumps or motors with variable flow rates (swashplate, rotary cam, etc.), the torque on the shaft is strongly dependent on the pressure. During a cycle where the gas pressure increases sharply (e.g., from 20 to 300 bar), the mechanical load increases, leading to oversizing, fatigue, and losses. The invention aims to decouple the force transmitted to the crankshaft from pressure variations, while maintaining a stable speed / frequency drive. Principle of the solution

[0072] The device employs an oscillating pendulum (3) (fig. 2) articulated relative to a frame (1) around a movable pivot (2c). The pivot is supported by a carriage (2) comprising two guide elements:

[0073] » a first element (2a) guided in translation along the frame (1);

[0074] "a second element (2b) guided along the balance wheel (3) while allowing oscillation.

[0075] A rigid structure connects these elements (2a, 2b) and carries the pivot axis (2c), perpendicular to the plane of oscillation. The coordinated movement of the carriage (2) along the frame (1) and the balance wheel (3) modifies the lever arm, and therefore the stroke of at least one piston (6) sliding in at least one cylinder (8), without changing the oscillation frequency of the balance wheel.

[0076] Thus, when the pressure increases in the cylinder (8) or in the associated compression / expansion stage, the stroke can be reduced to maintain a substantially constant force (and therefore torque). This regulation improves durability, reduces lateral forces, and allows for operation at stable power.

[0077] Training and transmission

[0078] The rocker arm (3) is driven by drive means (10, 10a, 10b), for example a motor or alternator in reversible mode, imposing an oscillating motion. The rocker arm (3) is connected to the piston (6) by at least one connecting rod (9) (or functional equivalent: flexible rod, cable), having a pivot on the rocker arm side (9a) and a pivot on the piston side (9b), adapted for single- or double-acting operation.

[0079] In one variant, the connecting rod can be omitted if the cylinder (8) is mounted in an oscillating manner, so as to absorb variations in angle and limit stresses on the piston rod.

[0080] Stroke regulation during operation

[0081] The movement of the mobile pivot (2c) is ensured by actuation means (e.g., cylinders, motorized screws, belts) acting:» between the sleeve / guide (2a) and the frame (1);

[0082] "and between the sleeve / guide (2b) and the rocker arm (3),

[0083] in a coordinated manner. Position sensors associated with these actuators can synchronize the movements. The pivot movement is preferably carried out when the forces on the rocker arm are low (low load phase), in order to limit the driving energy and dynamic disturbances.

[0084] Decoupling “fast pump / slow gas cycle”

[0085] The device can operate at a high oscillation frequency (e.g., on the order of tens to thousands of cycles / min) while simultaneously powering slower gas compression / expansion cycles (on the order of seconds to minutes). This decoupling allows:

[0086] » to operate the pump / motor in a favorable efficiency zone (quasi-steady state),

[0087] ® while progressively adapting the pressure in the associated gas volume.

[0088] Valves and cycle architectures (optional)

[0089] The device includes fluid inlet and outlet means with at least two separate ports. In one configuration, each cylinder (8) can be equipped with a rotary disc valve mechanically synchronized with the rocker arm (3), ensuring intake / outlet switching without reversing the movement. A four-way valve can control, at a slower rate, the alternation between two gas reservoirs (20a, 20b) so that one fills while the other empties, and vice versa. Gas inlet / outlet valves can complete the assembly according to the chosen cycle scheme (compression or expansion).

[0090] Multi-level and reversible (optional)

[0091] The device can be implemented with several compression / expansion stages (cylinders of very different volumes and diameters) to successively handle low and high pressures. It is reversible and can operate in pump mode (mechanical energy compression) or in motor mode (expansion - mechanical energy), particularly in compressed air or cryogenic energy storage systems.

[0092] Benefits

[0093] The movable pivot and constant frequency stroke modulation allow for:

[0094] • a more consistent torque on the shaft / crankshaft despite the pressure increase,

[0095] "a reduction in stress and mechanical fatigue,

[0096] "improved operational stability and adaptation to cycles"

[0097] isothermal / cryogenic.

Claims

Demands 1. A quasi-isothermal gas compression and / or expansion system, comprising at least one compression and / or expansion cylinder (110) containing a compression and / or expansion fluid intended to act as a liquid piston, the system comprising means arranged to vary, during the cycle, the level and / or quantity of said fluid in the cylinder (110) and a rotary heat exchanger (102) disposed inside the cylinder (110), the system being arranged such that, in operation: - the rotary heat exchanger (102) is, during part of the cycle, immersed in the compression and / or expansion fluid, so that its mass is brought substantially to the temperature of the compression and / or expansion fluid, and - when the level of the compression and / or expansion liquid falls below the rotary heat exchanger (102), the latter emerges from the liquid, is driven into rotation, stirs the gas present in the cylinder (110), exchanges heat with said gas, due to its thermal capacity previously brought to the temperature of the liquid, and expels, by effect of centrifugal force, the residual compression and / or expansion liquid which it contains and Zou retains. in order to allow rapid filling of the cylinder (110) in compression mode, complete expansion of the gas in expansion mode and to maintain the compression and / or expansion phases of the so-called gas in a substantially quasi-isothermal regime.

2. A system according to claim 1, characterized in that it comprises means for supplying compression and / or expansion fluid configured to introduce the compression and / or expansion fluid towards the center of the rotary heat exchanger (102) when the latter is rotating, said compression and / or expansion fluid being subsequently expelled outwards from the rotary heat exchanger (102) by the effect of the rotation, so as to provide active cooling or heating of the rotary heat exchanger (102) and to improve heat transfer between the rotary heat exchanger (102), the compression and / or expansion fluid, and the gas.

3. A volumetric device for pumping, compressing, or motorizing a fluid, comprising: » a frame (1) constituting the load-bearing structure of the device; "a pendulum (3) oscillating in a plane relative to said frame (1); • a connecting trolley (2) comprising: - two guide elements (2a, 2b) configured to allow said carriage (2) to move in translation respectively along the frame (1) and along the rocker arm (3), - a rigid structure linking said elements (2a, 2b) and carrying a pivot axis (2c) perpendicular to said plane, so that the rocker arm (3) is articulated on the frame (1) around said pivot (2c); "at least one piston (6) sliding in at least one cylinder (8); • means for the intake and evacuation of the fluid comprising at least two separate orifices; “at least one connecting rod (9) linking the rocker arm (3) to the piston (6); • means for driving or receiving energy (10, 10a, 10b) configured to impose an oscillating motion on the balance wheel (3); the device further comprising actuating means configured to move the carriage (2) along the frame (1) and the rocker (3), in a coordinated manner during operation, so as to modify the position of the movable pivot (2c), this movement adjusting the lever arm of the rocker (3) and therefore the stroke of the piston (6), in order to regulate the flow of pumped, compressed or motor fluid.

4. System according to claim 1 comprising the pumping device according to claim 3, the device being configured to modulate the flow rate of the compression and / or expansion liquid as a function of the gas pressure, so as to maintain substantially constant power and / or torque during a compression and / or expansion cycle.

5. System according to any one of claims 1, 2 or 4, characterized in that it comprises heat exchange means disposed outside the cylinder (110), configured to evacuate to an external environment at least part of the heat transferred to the compression and / or expansion fluid and / or to supply heat to said fluid, so as to limit the thermal drift of the cycle.

6. System according to any one of claims 1, 2, 4 or 5, characterized in that it comprises drive means configured to rotate the rotary heat exchanger (102) at least when it emerges from the compression and / or expansion liquid.

7. System according to any one of claims 1, 2, 4, 5 or 6, wherein the rotary heat exchanger (102) comprises several superimposed sections configured to operate independently, so as to ensure the operation of the heat exchanger when at least a part of it is immersed in the compression and / or expansion fluid.

8. System according to any one of claims 1, 2, 4, 5, 6 or 7, characterized in that the compression and / or expansion liquid is introduced into the rotary heat exchanger in a form that promotes its dispersion, so as to increase the heat exchange surface between the liquid, the exchanger and the gas.

9. System according to any one of the preceding claims, characterized in that the rotary heat exchanger (102) is configured to be alternately immersed in the compression and / or expansion liquid and exposed to the gas during the cycle, so as to thermally charge its mass during immersion and to exchange heat with the gas during its emergence.

10. System according to any one of the preceding claims, characterized in that the rotary heat exchanger (102) has a structure comprising gaps and / or a developed surface capable of temporarily retaining a portion of the compression and / or expansion fluid before its expulsion under the effect of rotation.

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