Engines that operate using compressed SMA material

Abstract

This invention provides an improved system and method for generating a large power output from an SMA or NTE engine core for use in an energy recovery device. [Solution] An energy recovery apparatus and energy recovery method comprising: an engine comprising a plurality of elongated shape memory alloy (SMA) elements or negative thermal expansion (NTE) elements configured as a core and connected to a drive mechanism; an immersion chamber adapted to house the engine and adapted to being sequentially filled with fluid so as to expand and contract the SMA elements or NTE elements by heating and cooling cycles of the SMA elements or NTE elements; and a compressor configured to apply a compressive mechanical force to at least one of the SMA elements or at least one of the NTE elements. The applied compressive mechanical force further compresses at least one SMA element or at least one NTE element during the cooling cycle.

Description

Technical Field

[0001] This application relates to energy recovery, particularly to engines that utilize shape memory alloys (SMA) or negative thermal expansion (NTE) materials.

Background Art

[0002] Low-grade heat, generally considered to be below 100 degrees Celsius, constitutes a significant waste energy stream in industrial processes, power generation, and transportation applications. The recovery and reuse of such waste streams are desirable. An example of a technology proposed for this purpose is the thermoelectric generator (TEG). Unfortunately, TEGs are relatively expensive. Another highly experimental approach proposed for recovering such energy is the adoption of shape memory alloys.

[0003] A shape memory alloy (SMA) is an alloy that "remembers" its original shape by cold forging and returns to its previous deformed shape when heated once deformed. This material is a lightweight solid that can replace conventional actuators such as hydraulic, pneumatic, and motor-based systems.

[0004] The three main types of shape memory alloys are alloys of copper-zinc-aluminum-nickel, copper-aluminum-nickel, and nickel-titanium (NiTi), but SMA can also be fabricated, for example, by alloying zinc, copper, gold, or iron. This list is non-exhaustive.

[0005] Memory of such materials has been adopted and proposed since the early 1970s for use in heat recovery processes, particularly by constructing SMA engines that recover energy from heat as kinetic energy. Recent publications relating to energy recovery devices include Patent Document 1 (International Publication No. 2013 / 087490), which has been assigned to the assignee of the present invention. The energy recovery device consists of an engine core having multiple long wires arranged in a bundle configuration or tightly packaged together. It is desirable to efficiently convert the contraction of SMA or negative thermal expansion (NTE) wire material into mechanical force. Complex stress-strain-temperature relationships are observed in SMA materials. Generally, the deformation of SMA material from the "de-twined" martensite phase to the austenite phase involves a combination of stress and temperature.

[0006] Patent document 2 (UK Patent No. 2,533,357, Exergyn) deals with the use of a core that provides a restoring force to a material in a stretched martensitic state and a spring that dampens deviations with smooth operation, in an antagonistic arrangement. Patent document 3 (US Patent Application Publication No. 2014 / 007572, GM Global) describes a method for improving the performance of a material at various high environmental temperatures by applying an appropriate amount of restoring force to a martensitic state. Patent document 4 (US Patent No. 5,442,914, Otsuka) discloses a shape memory alloy (SMA) heat engine including at least one mounting body with a conical disc spring attached to a perforated tube. This engine functions by applying tension to an SMA heat engine, and does not produce efficient output. Furthermore, the tensile stress leads to damage to the SMA material.

[0007] As occurs in the prior art described above, SMA materials tend to break, so fatigue life is a major issue related to the tension or stress applied to the SMA material. In cases where SMA wires are used, the wire breaks. When a load is applied to the wire in the complete martensite (or complete austenite) phase, strain occurs according to Young's modulus. Even without applied external stress, austenite and twinned martensite states spontaneously occur in the wire. A drawback of unloaded shape memory alloys is that the wire does not undergo specific bending, and the transition occurs based solely on temperature differences. To obtain useful power from wire cycle operation, stress must be applied to it. The magnitude of the stress depends on the desired deformation. Problems have been found with SMA wire elongation, which is limited in relation to some shape memory alloys or NTE materials. In addition, elongation limitations occur because the wire temperature is not low enough during the cooling / relaxation cycle. This limitation on the amount of wire strain available for recovery during the power stroke means that power output is limited. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] International Publication No. 2013 / 087490 [Patent Document 2] British Patent No. 2,533,357 Exergyn [Patent Document 3] U.S. Patent Application Publication No. 2014 / 007572, GM Global [Patent Document 4] U.S. Patent No. 5,442,914 Otsuka [Overview of the project] [Problems that the invention aims to solve]

[0009] Therefore, the objective is to provide improved systems and methods for generating a large power output from an SMA or NTE engine core for use in energy recovery devices. [Means for solving the problem]

[0010] According to the present invention, an energy recovery device is provided, comprising an engine having a plurality of shape memory alloy (SMA) elements or negative thermal expansion (NTE) elements configured to define a core and optionally connected to a drive mechanism, as presented in the appended claims; an immersion chamber adapted to house the engine and adapted to being sequentially filled with fluid to expand and contract the SMA elements by heating and cooling cycles of the SMA elements; and a compressor configured to apply a compressive force to at least one of the SMA elements during the heating and / or cooling cycles.

[0011] This invention utilizes a mechanical compression device and method to compress SMA elements defining the core during use. Compression of the engine increases the fatigue life of the material and reduces maintenance of the entire core. Since access to SMA components for maintenance purposes is not required, this reduces overall lifetime costs and simplifies the system design. In addition, using a compressed core design allows for the use of lower-grade SMA materials, which are less expensive, and the amount of SMA material used can be reduced by increasing the cycle speed.

[0012] Mechanical compression of SMA elements will open up the market for many power generation applications by reducing maintenance costs and enabling technologies that generate power at low efficiency.

[0013] In one embodiment, a step is provided to apply controlled compression.

[0014] In another embodiment, an energy recovery device is provided, comprising an engine having a plurality of elongated shape memory alloy (SMA) elements or negative thermal expansion (NTE) elements fixed at a first end and connected at a second end to a drive mechanism, and an immersion chamber adapted to house the engine and adapted to being sequentially filled with fluid to expand and contract the SMA elements by heating and cooling cycles of the SMA elements, wherein controlled mechanical compression is applied to at least one of the SMA elements during the cooling cycle.

[0015] In one embodiment, the SMA element comprises at least one mounting body made of multiple plates, wherein at least two plates made of shape memory alloy are assembled vertically.

[0016] In one embodiment, plates are assembled vertically, and each plate is machined with multiple fluid ports that allow the passage of a fluid at a specific temperature within the mounting body. The fluid is introduced into the mounting body through the intake port, passes through the mounting body, and is then discharged to the outside through the discharge port.

[0017] In a preferred embodiment of the present invention, the intake port and the exhaust port are independent structural units and are formed using the same SMA used to manufacture the plates. Furthermore, at least one mounting body made of multiple SMA plates comprises an SMA core.

[0018] In one embodiment, SMA elements or SMA plates are formed using an additive manufacturing or 3D printing process.

[0019] In a preferred embodiment of the present invention, an SMA core is positioned inside a housing having a plurality of buckling supports adapted to maintain the integrity of a mounting plate by at least one SMA core while a load is applied.

[0020] In one embodiment, the composition of the SMA forming each of the plurality of mounting plates is the same. In another embodiment of the present invention, the composition of the SMA forming at least one plate is different from that of the other plates of the mounting body.

[0021] In another embodiment of the present invention, a number of SMA cores are arranged within the housing, and the composition of the SMA forming the plurality of plates mounted on one SMA core is different from the composition of the SMA forming the plurality of plates mounted on the other SMA cores.

[0022] The present invention increases the surface area between the SMA material and the fluid. Further, the fluid contacts only the SMA material when passing through the SMA plate mounting body, reducing the overall heat loss.

[0023] The configuration of the suction port and the discharge port using the SMA material further reduces the heat loss. The form of the mounting body described in the present invention resists buckling and reduces the need for an external support.

[0024] In one embodiment, the compression device includes an electromechanical actuator.

[0025] In one embodiment, the compression device includes a hydraulic compression module configured to apply pressure to a piston using pressurized hydraulic fluid.

[0026] The housing and the buckling support ensure that the SMA plate is thermally insulated and can withstand the applied hydraulic load, while allowing the movement of individual mounting bodies when in the compressed state. The present invention also enables easy improvement of the engine core due to the ease of exchanging one SMA mounting body with another.

[0027] This means that when a better SMA composition becomes available, it is easy to replace the mounting body with plates formed from the old SMA composition with a mounting body with plates formed from the new and improved SMA composition.

[0028] In one embodiment, an engine core is provided for use in energy recovery, comprising: at least one mounting body made of a plurality of plates, at least two of which are formed of a shape memory alloy and assembled vertically, the plurality of shape memory alloy plates having a plurality of fluid ports, such as serpentine ports, adapted to allow the passage of fluid through the mounting body; an intake port adapted to introduce fluid into the mounting body; and an exhaust port adapted to discharge the fluid introduced from the intake port to the outside, wherein the intake port and the exhaust port are formed of a shape memory alloy.

[0029] In another embodiment, an engine is provided for use in energy recovery, comprising: at least one mounting body made of a plurality of plates, wherein at least two plates are formed of a shape memory alloy and assembled vertically, and the plurality of shape memory alloy plates have at least one fluid port adapted to allow the passage of fluid in the mounting body; a compressor configured to apply a compressive mechanical force to at least one of the SMA plates during a heating cycle and / or cooling cycle; an intake port adapted to introduce fluid into the mounting body; and an exhaust port adapted to discharge the fluid introduced from the intake port to the outside, wherein the intake port and the exhaust port are formed of a shape memory alloy.

[0030] In one embodiment, the compressor applies a mechanical force to at least one of the SMA plates during the cooling cycle. [Brief explanation of the drawing]

[0031] Referring to the attached drawings, the present invention will be more clearly understood from the following description of embodiments of the present invention, which are merely given as examples. [Figure 1] The diagram illustrates the SMA material action cycle between heating and cooling cycles. [Figure 2a] This is a perspective view of a preferred embodiment of the present invention. [Figure 2b] An embodiment of the present invention illustrates a housing for an engine having a fluid inlet port and an outlet port. [Figure 3a] A preferred embodiment of the present invention is illustrated, showing side and top views of multiple SMA materials placed on top of each other. [Figure 3b] A preferred embodiment of the present invention is illustrated, showing side and top views of multiple SMA materials placed on top of each other. [Figure 4] This is a front view of a preferred embodiment of the present invention. [Figure 5a] The diagram illustrates several stepped configurations using different engine cores for energy recovery devices. [Figure 5b] The diagram illustrates several stepped configurations using different engine cores for energy recovery devices. [Figure 5c] The diagram illustrates several stepped configurations using different engine cores for energy recovery devices. [Figure 5d] The diagram illustrates several stepped configurations using different engine cores for energy recovery devices. [Modes for carrying out the invention]

[0032] This invention relates to a heat recovery system, such as an engine, that can use either a shape memory alloy (SMA) or another negative thermal expansion material (NTE) (both referred to as elastocaloric materials) to generate greater power output from a heated fluid using compression. The invention provides an engine cycle in which the SMA is compressed. In compression mode, the fatigue life is extended and no longer limited. The compression load is considerably higher than the tensile load, thus resulting in high efficiency.

[0033] A well-known energy recovery device is described in International Publication No. 2013 / 087490, which has been transferred to the assignee of the present invention and is fully incorporated herein by reference.

[0034] In such applications, the shrinkage of such materials when exposed to a heat source is incorporated and converted into usable mechanical action. Nickel-titanium alloys (NiTi) have proven to be useful materials as working elements in such engines. This alloy is a well-known shape memory alloy with numerous applications across diverse industries. In the context of the present invention, it will be recognized that suitable SMA or NTE materials can be used. While elongated bodies or wires have been proposed for such engines, it has been found that wires tend to break due to the applied stress.

[0035] Forces are generated through the contraction and expansion of the SMA material during high-temperature and low-temperature cycles within the working core via a piston-transmission mechanism. A key aspect of this system is that a reliable assembly can be fabricated so that the force is large and the displacement small for the maximum number of working cycles.

[0036] Figure 1 illustrates the action cycle of an SMA material between heating and cooling cycles. The invention described herein outlines systems and methods for increasing the action power of a shape memory alloy during high-temperature and low-temperature cycles. An important aspect of the invention is the compression of the SMA material during the cycle.

[0037] In compression mode, the fatigue life of the SMA material or core is extended and no longer limited. The compressive load is considerably higher than the tensile load, and therefore compressing the SMA material results in increased power output and improved efficiency.

[0038] Thermodynamic engine cycles can consist of conventional gas cycles such as the Stirling, Brayton, or Ericsson cycle, or any combination of these cycles, as illustrated in Figure 1.

[0039] As shown in Figure 1, the cycle can be configured such that the SMA material attempts to recover from its deformed state [martensite-austenite] as it absorbs heat from a high-temperature source [process 1-2]. Thus the material expands, and therefore the action can be extracted using a hydraulic cylinder or other device.

[0040] Once this process is complete, the material temperature is cooled using the heat recovery circuit until the material temperature approaches the low-temperature source temperature [Process 2-3]. At this point, a low compressive load is applied to the material to compress it by increasing the drive temperature. Doing so causes the material to contract and release heat to the low-temperature source [Process 3-4]. Once complete, the heat recovery circuit is used again to raise the material temperature using the heat stored in the circuit. At this point, the cycle is complete.

[0041] Compression of SMA elements or materials in low-temperature cycles can be employed using appropriate mechanical or tensile mechanisms, such as a power module. The power control module can be controlled independently.

[0042] The required strain is achieved by mechanically compressing the SMA element. A power control module for applying compression can be implemented in several ways. Compression of SMA elements can be achieved using a wide range of compression techniques, including electromechanical and hydraulic compression. A suitable electromechanical actuator converts rotational motion from an electric motor into linear motion. Most designs are similar to a nut-bolt system, where the threaded bolt is mounted on a motor and rotatable, and the nut is fixed to the component being compressed, allowing the bolt's shaft to move up and down. In hydraulic compression, pressure is applied to a piston by a pressurized hydraulic fluid. When the pressure is released, the SMA material becomes expandable.

[0043] Figure 2a shows a perspective view of a preferred embodiment of the present invention. The disclosed engine comprises at least one mounting body made of a plurality of plates 101 formed from SMA and assembled vertically. Each of the plurality of plates 101 has a plurality of fluid ports 102 machined into it. The fluid ports 102 are designed to allow the passage of a fluid of a specific temperature through the mounting body of plates 101. The mounting body of plates 101 is adapted to absorb heat and conserve energy as the fluid passes through and further comprises a plurality of plate reinforcement slots 103. The plate reinforcement slots 103 allow for the insertion of a robust rod to resist buckling under compression. The slots 103 have a diameter of several millimeters and are the length of the mounting body, and their size can be selected based on the desired design.

[0044] Figure 2b shows an example of a housing in which a plate mount / core is installed. A fluid at a predetermined temperature, such as water, is introduced or supplied to the chamber housing the mount / core through a single inlet 104 and a fluid outlet 105. Inlet 104, adapted for introducing fluid to the mount and outlet 105, is adapted for discharging fluid introduced from the intake port to the outside. In a preferred embodiment of the present invention, the intake port and exhaust port are independent structural units and are fabricated using the same SMA material as the mount, which consists of multiple plates, to minimize heat loss. Fluid ports 102 machined into each plate significantly increase the surface area between the plate and the fluid, and ensure that the fluid comes into contact only with the SMA material, reducing overall heat loss. The fluid ports can be configured in any geometric pattern, such as a grid, circular, or polygonal pattern. The SMA plate 101 in the shown embodiment is substantially rectangular in shape. SMA plates can be considered basic building blocks for constructing core and engine systems of a certain size. The plate design correlates with heat transfer optimization, and the embodiments shown are merely illustrative. Smaller plates and mounts may be used for reduction using the same principle. It will be recognized that the engine operates between high-stress and low-stress states. Ideally, low stress = low temperature (starting point), high stress = high temperature, and the SMA plate is kept in a compressed state throughout the cycle. The applied compressive mechanical force provides further compression to at least one SMA element during the cooling cycle.

[0045] Figures 3a and 3b illustrate preferred embodiments of the present invention in which a core or SMA material comprises a plurality of SMA components 101 and is arranged as a mounting body of a plurality of SMA plates 101 to define an engine core. The plurality of SMA plates 101, which are mounted one above the other, can be compressed during the cycle as needed. Buckling supports 202 ensure that the SMA plates 101 are thermally insulated and that the entire structure is supported and able to withstand hydraulic loads.

[0046] The cycle may be a single stage or may include multiple stages to increase the temperature range for heat recovery.

[0047] In one embodiment, a cycle may involve multiple cores and internal heat recovery between cores, or heat from a single core may be stored between cycles. This arrangement configuration increases the efficiency of the system.

[0048] The system may include action recovery, where the energy stored in the compression material is directly used to compress the second SMA component (engine core), or the energy is stored and indirectly used to compress additional SMA components in a later stage.

[0049] This stored energy can be stored in the form of a pressurized fluid or converted into electricity and stored or used elsewhere in the system.

[0050] Figure 4 shows a front view of another preferred embodiment of the present invention. In the figure shown, a mounting body made of SMA plates 101 forming an SMA core is placed in a housing 201. The housing 201 has a plurality of buckling supports 202 to maintain the integrity of the SMA core when a load is applied. When a compressive force is applied to the SMA core of the engine, it is important to optimize the location, size, and number of buckling supports in order to estimate the amount of force that can be applied without crushing the structure. This ensures the optimal extraction of the heat characteristics of the SMA. The housing 201 and the buckling supports 202 ensure that the SMA plates 101 are thermally insulated and that the entire structure is supported and can withstand hydraulic loads while allowing movement of the individual mounting bodies in a compressed state.

[0051] In the context of the present invention, it will be recognized that the engine / core can be assembled in several different configurations, as shown in Figure 5. In one embodiment, the composition of at least one plate of the mounting body made of SMA plates is different from that of the other plates of the mounting body. Different SMA material mixtures can be used for different SMA plates within a single mounting body.

[0052] In another embodiment of the present invention, an SMA core comprising multiple SMA mounts is used. In this multiple mount configuration, each mount consists of a plate having a different SMA composition, meaning that plates within the same mount have the same SMA composition.

[0053] In another embodiment of the present invention, a plurality of mounting bodies are used, each mounting body having a plurality of SMA plates. Each mounting body has at least one SMA plate having a different alloy composition from the other plates of the same mounting body.

[0054] Figures 5a to 5d illustrate several stepped configurations of an engine according to another embodiment of the present invention. Stepped configurations of SMA plates that can be used to increase delta T can be achieved using several approaches. For example, Figure 5a shows an in-mount configuration in which different mixtures by optimized SMA plates can be used within a single mount. For example, plates of mixture 1, mixture 2, and mixture 3 are arranged within a single mount. Figure 5b illustrates a multi-mount version of Figure 5a. Mounts of plates, each containing the same SMA mixture, interact with other plate mounts containing different SMA mixtures. For example, a mixture 1 mount interacts with a mixture 2 mount in series within a multi-mount configuration (and so on). Figure 5c is a multi-mount version of Figure 5b. Mounts of plates, each containing a number of SMA mixtures, interact with other plate mounts containing similar or different SMA mixtures within a multi-mount configuration. For example, within a multi-mount configuration, different or similar stepped configurations within the mounts interact in series. Figure 5d shows a multi-core configuration where the cores of a plate consisting of multi-mount version 1, multi-mount version 2, or a combination of both interact in series to form a single stage.

[0055] In this specification, the words “comprise,” “comprises,” “comprised,” and “comprising,” or any variation thereof, and the words “include,” “includes,” “included,” and any variation thereof, are considered to be interchangeable as a whole, and the broadest possible interpretations and their opposites should all be given.

[0056] The present invention is not limited to the embodiments described above, and may vary in both configuration and detail. [Explanation of symbols]

[0057] 101 SMA Plate 102 Fluid Ports 103 Plate reinforcement slots 104 Entrance 105 Exit 201 Housing 202 Buckling support

Claims

1. An energy recovery device, An engine comprising multiple shape memory alloy (SMA) elements or negative thermal expansion (NTE) elements configured to define a core and connected to a drive mechanism, An immersion chamber adapted to house the engine and adapted to sequential filling with fluid such that the SMA element or NTE element expands and contracts due to heating and cooling cycles of the SMA element or NTE element, A compression device configured to apply a compressive mechanical force to at least one of the SMA elements or at least one of the NTE elements during the heating cycle and / or cooling cycle, An energy recovery device equipped with the following features.

2. The energy recovery apparatus according to claim 1, wherein the applied compressive mechanical force further compresses the at least one SMA element or at least one NTE element during the cooling cycle.

3. The energy recovery device according to claim 1 or 2, wherein the SMA element or the NTE element comprises at least one mounting body made of a plurality of plates, and at least two plates are formed of a shape memory alloy and assembled vertically.

4. The energy recovery device according to claim 3, wherein the plurality of shape memory alloy plates comprises a plurality of fluid ports adapted to allow the passage of fluid in the aforementioned body.

5. The energy recovery device according to claim 1, wherein the compression device comprises an electromechanical actuator.

6. The energy recovery device according to claim 1, wherein the compression device comprises a hydraulic compression module configured to apply pressure to a piston using a pressurized hydraulic fluid.

7. The energy recovery apparatus according to claim 1, wherein SMA elements or SMA plates are formed using an additive manufacturing or 3D printing process.

8. The energy recovery device according to claim 1, comprising a plurality of SMA cores arranged within the housing, each core configured to be compressed independently during the cycle.

9. The energy recovery apparatus according to claim 8, wherein the composition of the SMA forming the plurality of plates placed on one SMA core is different from the composition of the SMA forming the plurality of plates placed on other SMA cores.

10. A method of energy recovery, The steps include defining a core and arranging multiple elongated shape memory alloy (SMA) elements or negative thermal expansion (NTE) elements so as to be connected at one end to a drive mechanism, The steps include: housing the SMA element or NTE element in a chamber so that it expands and contracts through heating and cooling cycles of the SMA element or NTE element, and sequentially filling the chamber with fluid; The steps include applying mechanical compression to at least one of the SMA element or the NTE element during the cooling and / or heating cycle, A method of including.

11. The method according to claim 10, further comprising the step of applying a compressive mechanical force to the at least one SMA element or the at least one NTE element during the cooling cycle.

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