A heat-to-force conversion device driven by low-grade thermal energy and alloy assembly method

Abstract

A low-grade thermal energy driven heat-to-energy conversion device and alloy assembly method, the device includes a driver main body pipeline and a fluid alternating circulation loop connected to the driver main body pipeline, a driving pump is provided in the fluid alternating circulation loop, and the driving pump drives the heat exchange fluid to circulate in the fluid alternating circulation loop, the fluid alternating circulation loop has parallel high and low temperature fluid branches, the high temperature fluid branch is provided with a high temperature circulation solenoid valve and a high temperature heat sink in series, and the low temperature fluid branch is provided with a low temperature circulation solenoid valve and a low temperature heat source in series; a shape memory alloy and a connecting rod-slider structure are provided inside the driver main body pipeline, and the driving force and displacement generated by the phase change of the shape memory alloy are output through the connecting rod-slider structure. The present invention adopts different assembly methods for shape memory alloys of different shapes, and outputs force and displacement by recovering heat energy through shape memory alloys and heat transfer fluids, so as to effectively recycle and utilize low-grade thermal energy.

Description

Technical Field

[0001] The present invention belongs to the technical field of low-grade thermal energy recovery and utilization, and in particular relates to a thermal-mechanical conversion device driven by low-grade thermal energy and an alloy assembly method. Background Art

[0002] At present, there are many mature and efficient recycling technologies for high-grade energy above 400℃, such as low-temperature steam turbines to recover waste heat for power generation, and medium-grade energy between 100℃ and 400℃ can be recovered by technologies such as supercritical Rankine cycle. However, for low-grade energy below 100℃, existing technologies often only recover waste heat to heat domestic water or heating according to local conditions. At present, this part of energy is difficult to store or has not been more widely and effectively utilized.

[0003] Shape memory alloys represented by nickel-titanium alloys undergo a martensite-austenite phase transformation when absorbing heat and generate deformation and force. After releasing heat, the alloy returns to its original size. In order to output a sufficiently large deformation, a sufficiently long shape memory alloy must be used, which will lead to uneven temperature distribution in the driver, and then to uneven distribution of alloy phase components, reducing the output efficiency of the thermal driver. In addition, due to the characteristics of high hardness and large thermal deformation of shape memory alloys, it is difficult to perform thermal processing such as welding. Summary of the invention

[0004] The purpose of the present invention is to address the problems in the above-mentioned prior art and provide a low-grade thermal energy driven thermal-mechanical conversion device and an alloy assembly method. The device can output force and displacement by recovering thermal energy through shape memory alloys and heat transfer fluids, thereby filling the technical gap in the recovery and utilization of low-grade thermal energy below 100°C. At the same time, according to the conversion temperature of different shape memory alloy materials, it can also be used in the scenario of medium-grade thermal energy utilization. The mechanical work output by the shape memory alloy can drive caloric elastic materials or piezoelectric materials to produce refrigeration effect or electrical effect, and can also be used in other industrial scenarios.

[0005] In order to achieve the above object, the present invention has the following technical solutions:

[0006] A heat-to-mechanical conversion device driven by low-grade thermal energy comprises a driver main pipeline and a fluid alternating circulation loop connected to the driver main pipeline, wherein a driving pump is arranged in the fluid alternating circulation loop, and a heat exchange fluid is driven by the driving pump to circulate in the fluid alternating circulation loop, and the fluid alternating circulation loop has parallel high and low temperature fluid branches, wherein a high temperature circulation solenoid valve and a high temperature heat sink are arranged in series on the high temperature fluid branch, and a low temperature circulation solenoid valve and a low temperature heat source are arranged in series on the low temperature fluid branch; a shape memory alloy and a connecting rod-slider structure are arranged inside the driver main pipeline, and a driving force and displacement generated by a phase change of the shape memory alloy are output through the connecting rod-slider structure.

[0007] As a preferred solution, the driver main body pipeline includes a top outlet cover, a top fixed bin, a frame connection structure, an intermediate pipeline, a bottom connection structure and a bottom fixed bin; the top outlet cover and the bottom fixed bin are both provided with fluid pipeline interfaces, and are respectively connected to the fluid alternating circulation loop outlet and the fluid alternating circulation loop inlet; a supporting frame is provided outside the driver main body pipeline, and the frame connection structure is connected and fixed to one end of the supporting frame; the bottom fixed bin is connected to the bottom connection structure, the top fixed bin is connected to the frame connection structure, the intermediate pipeline is connected between the bottom connection structure and the frame connection structure, the shape memory alloy is placed in the intermediate pipeline, and the two ends are respectively connected to the top fixed bin and the connecting rod-slider structure, and the connecting rod-slider structure is connected and fixed to the driving member fixed at the other end of the supporting frame through the output limiting structure.

[0008] As a preferred solution, the bottom connecting rod of the connecting rod-slider structure extends out of the bottom fixed bin, and the bottom connecting rod of the connecting rod-slider structure is connected to the output limiting structure, and is connected to the load structure through the output limiting structure.

[0009] As a preferred solution, the intermediate pipe is equipped with a filling structure, which is made of a variable cross-sectional area structure made of insulating material. By controlling the cross-sectional area, the flow rate distribution of the heat exchange fluid in each part of the intermediate pipe is redistributed.

[0010] As a preferred solution, the volume V of the filling structure 501 is t The volume V of the intermediate pipe 104 0 、Volume V of shape memory alloy 301 s and the inlet volume flow rate Q of the driver body pipeline m The following calculation formula is met:

[0011]

[0012] As a preferred solution, one end of the shape memory alloy is connected to a slider structure in a connecting rod-slider structure, and the slider structure moves in a bottom fixed bin, and the movement of the slider structure is constrained by the inner wall of the bottom fixed bin.

[0013] As a preferred solution, the connecting rod in the connecting rod-slider structure is sealed with a sealing ring and the bottom fixed bin, a positioning structure is arranged on the output limiting structure, and the output limiting structure uses a weight or a motor to apply an external force to pre-tighten the shape memory alloy.

[0014] An assembly method of the low-grade thermal energy driven heat-to-mechanical conversion device, using different assembly methods for shape memory alloys of different shapes, includes:

[0015] When the shape memory alloy is in the form of a wire: a through hole is drilled on the side of the bolt, and after the shape memory alloy passes through the through hole of the bolt, a nut is used to tighten the two sides of the shape memory alloy, and the shape memory alloy is fixed by the friction force after the nut is tightened; when multiple shape memory alloys need to be fixed, multiple through holes with center lines parallel to each other are drilled along the axial direction of the bolt, and each shape memory alloy is separated by a gasket or a nut; bosses are provided on both sides of the bolt, holes are drilled on the bosses, and the bolts are fixed in the top fixing chamber through the through holes on the bosses;

[0016] When the shape memory alloy is columnar or cylindrical: a ferrule is arranged on the outside of the shape memory alloy, and the ferrule is deformed by mechanical coupling to be nested with the shape memory alloy; the shape memory alloy with the ferrule is loaded onto a disk with one or more through holes, the inner diameter of the through holes on the disk is larger than the outer diameter of the shape memory alloy and smaller than the outer diameter of the ferrule; a positioning structure is arranged on the outside of the disk to be connected to the inside of the top fixed bin;

[0017] When the shape memory alloy is in the form of a sheet or other structure: a special fixture is designed to fix the shape memory alloy, and the shape memory alloy is fixed by geometric constraints and static friction; the size of the special fixture fills the internal volume of the top fixed bin as much as possible, and a through hole is reserved on the special fixture as a fluid channel, through which the heat exchange fluid can normally pass through the top fixed bin and enter the top outlet cover.

[0018] Compared with the prior art, the low-grade thermal energy driven thermal-mechanical conversion device of the present invention has at least the following beneficial effects:

[0019] The fluid alternating circulation loop is connected to the main pipeline of the driver, and the heat exchange fluid is driven by the driving pump, and high and low temperature fluid branches are formed by controlling the solenoid valve. Among them, in the high temperature fluid branch, the fluid absorbs heat from the high temperature heat sink above 70°C, and ensures that the temperature is above 70°C when flowing into the heat driver, so that the shape memory alloy in the main pipeline of the driver can be transformed from martensite to austenite; in the low temperature fluid branch, the fluid exchanges heat with the environment or low temperature heat source, and dissipates the residual heat in the heat driver to the environment or low temperature heat source. The rotation speed of the driving pump in the fluid alternating circulation loop and the start and stop cycle of the high temperature circulation solenoid valve and the low temperature circulation solenoid valve can be determined by the required force or displacement output rate. In the present invention, by cooperating with the alternating flow of the heat transfer fluid, the shape memory alloy achieves more efficient energy utilization efficiency and effectively expands the way of utilizing low-grade thermal energy.

[0020] Compared with the prior art, the assembly method of the low-grade thermal energy driven heat-to-power conversion device of the present invention has the following beneficial effects:

[0021] It is recommended that shape memory alloys be used in filament, column or tube shapes. Shape memory alloys in sheet or other structures may also be used. Compared with other elastic heat refrigeration devices or elastic heat drive devices, the present invention is not affected by the shape of the shape memory alloy, and the assembly method of the present invention does not cause additional deformation of the shape memory alloy. During the assembly process, the various structures are mutually constrained, and the shape memory alloy does not spin, which increases its service life. The shape memory alloy shrinks when heated, and is subjected to tensile stress generated by the outside world when it recovers. No compressive stress is generated during the whole process, and yield performance does not need to be considered. Since the martensitic transformation temperatures of different shape memory alloys are different, the heat-to-force conversion device provided by the present invention can achieve the benefits of heat recovery within a relatively wide temperature range. The present invention is reasonably designed and can effectively and efficiently recover low-grade thermal energy, filling the application gap. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0023] Figure 1 Schematic diagram of fluid alternating circulation of a heat-to-power conversion device driven by low-grade thermal energy according to an embodiment of the present invention;

[0024] Figure 2 A schematic diagram of a cycle of input temperature-output displacement of a heat-to-force conversion device according to an embodiment of the present invention on a state diagram;

[0025] Figure 3 A schematic diagram of the assembly structure of the driver main body pipeline according to an embodiment of the present invention;

[0026] Figure 4 A schematic diagram of the three-dimensional structure of the driver main body pipeline according to an embodiment of the present invention;

[0027] Figure 5 Schematic diagram of the top fixed bin structure and shape memory alloy assembly according to an embodiment of the present invention;

[0028] Figure 6 Schematic diagram of the bottom fixed bin structure and shape memory alloy assembly according to an embodiment of the present invention;

[0029] 101-top outlet cover; 102-top fixed bin; 103-rack connection structure; 104-middle pipeline; 105-bottom connection structure; 106-bottom fixed bin; 107-connecting rod-slider structure; 201-fluid alternating circulation loop inlet; 202-fluid alternating circulation loop outlet; 203-heat exchange fluid; 204-driving pump; 205-high-temperature heat sink; 206-low-temperature heat source; 207-high-temperature circulation solenoid valve; 208-low-temperature circulation solenoid valve; 301-shape memory alloy; 401-output limit structure; 501-filling structure; 601-support rack. DETAILED DESCRIPTION

[0030] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, ordinary technicians in this field can also obtain other embodiments without making creative work.

[0031] Although there are a few solutions that use shape memory alloys as thermal drivers, there is no solution for a thermal-mechanical conversion device that uses shape memory alloys and heat transfer fluids. However, some nickel-titanium alloys can generate driving forces at temperatures of 70-100°C, and this property can be used to make thermal drivers for thermal-mechanical conversion. Since fluid-solid heat exchange allows shape memory alloys to obtain more heat than solid-solid heat exchange in a short period of time, shape memory alloy drivers based on fluid-solid heat exchange have certain advantages. This type of thermal driver requires the passage of a fluid with alternating temperatures: a high-temperature heat transfer fluid heats the shape memory alloy to generate deformation and driving force, and a low-temperature or ambient temperature fluid cools the shape memory alloy and restores it to its original length. Since a low-grade heat source below 100°C can drive the shape memory alloy to produce a martensite-austenite phase transition, this type of thermal driver can well fill the gap in low-grade energy utilization. Therefore, an embodiment of the present invention proposes a thermal-mechanical conversion device driven by low-grade thermal energy, which utilizes the deformation and driving force generated by the process of shape memory alloy absorbing heat to produce a martensite-austenite phase transition, and recovers low-grade thermal energy. The shape memory alloy used in the present invention is a nickel-titanium alloy with an initial martensite phase: when the temperature is higher than 70°C, the shape memory alloy undergoes a martensite-austenite phase transition, the material contracts, and outputs force and displacement; when the temperature returns to below 30°C, the shape memory alloy undergoes an austenite-martensite phase transition, and the material returns to its original length. Shape memory alloys of different components correspond to different martensite and austenite transformation temperatures, that is, by using different shape memory alloys, the device proposed by the present invention can be applied to different temperature ranges.

[0032] See also Figure 1 and Figure 2The embodiment of the present invention is a heat-to-mechanical conversion device driven by low-grade thermal energy based on shape memory alloy and heat transfer fluid, which mainly includes a driver main pipeline and a fluid alternating circulation loop. Furthermore, the fluid alternating circulation loop mainly includes a driving pump 204, a high-temperature heat sink 205, a low-temperature heat source 206, a high-temperature circulation solenoid valve 207 and a low-temperature circulation solenoid valve 208. The fluid alternating circulation loop is connected to the fluid alternating circulation loop inlet 201 and the fluid alternating circulation loop outlet 202 reserved on the driver main pipeline. Driven by the driving pump 204 and the high-temperature circulation solenoid valve 207 and the low-temperature circulation solenoid valve 208, the heat exchange fluid 203 forms a high and low temperature cycle. During high-temperature circulation, the high-temperature circulation solenoid valve 207 is opened and the low-temperature circulation solenoid valve 208 is closed. At this time, it is necessary to ensure that: the heat exchange fluid 203 passes through the high-temperature heat sink 205, and then its temperature needs to be increased to above 75°C, so as to ensure that the fluid temperature at the inlet 201 of the fluid alternating circulation loop is higher than 70°C; during low-temperature circulation, the high-temperature circulation solenoid valve 207 is closed and the low-temperature circulation solenoid valve 208 is opened. It is necessary to ensure that: after the heat exchange fluid 203 passes through the low-temperature heat source 206, the temperature drops to 10°C-30°C, and the temperature at the inlet 201 of the fluid alternating circulation loop is also within this range. During the high-temperature circulation process, the shape memory alloy 301 undergoes austenite-martensite transformation, the material contracts along the length direction, and the driving force and displacement are output; during the low-temperature circulation process, the shape memory alloy 301 undergoes austenite-martensite transformation, and the material returns to its original length. Among them, the temperature-displacement curve of the shape memory alloy 301 during actual use is shown as follows Figure 2 As shown, according to different loads, the thermal-mechanical driving device of the embodiment of the present invention corresponds to different input-output curves.

[0033] Figure 3 The present invention provides an assembly structure of the driver main pipeline when the heat-force conversion device is used to drive a certain load structure; it involves a support frame 601, a driver main pipeline, an output limit structure 401, and a fluid alternating circulation loop. Among them, the bottom of the support frame 601 is fixed, and the top is welded or threaded with the driver main pipeline. A reinforcement beam is arranged above the support frame 601, and a displacement sensor and other devices can be additionally arranged on the reinforcement beam to monitor the output of the heat-force conversion device of the present invention. The support frame 601 is divided into upper and lower parts, and the length of the upper half can be adjusted to adapt to main pipelines of different sizes, that is, shape memory alloys of different lengths. The driver main pipeline is connected to the load structure through the output limit structure 401, and a positioning structure is arranged on the output limit structure 401 to ensure the positioning accuracy of the device during assembly. An additional interface can be arranged or reserved on the output limit structure 401 to connect with a motor or a mechanical structure, which is used to pre-tighten the shape memory alloy 301 in the main pipeline.

[0034] Figure 4The three-dimensional structure of the main pipeline of the driver is shown: the mechanical structure of the main pipeline of the driver is composed of a top outlet cover 101, a top fixed bin 102, a rack connection structure 103, an intermediate pipeline 104, a bottom connection structure 105, a bottom fixed bin 106 and a connecting rod-slider structure 107. The interior of the intermediate pipeline 104 can be arranged with a filling structure 501 close to the inner wall according to actual needs. The filling structure 501 is made of insulating material to reduce the temperature change of the pipeline shell when the heat exchange fluid 203 flows through the main pipeline, thereby reducing heat loss. In addition, the filling structure 501 in the intermediate pipeline 104 adopts a variable cross-sectional area structure. By controlling the cross-sectional area of ​​the structure, the flow velocity distribution of the heat exchange fluid 203 in each part of the intermediate pipeline 104 is redistributed, so that the heat exchange between the shape memory alloy 301 and the heat exchange fluid 203 in different areas along the flow direction is as uniform as possible.

[0035] Furthermore, the volume V of the filling structure 501 t The volume V of the intermediate pipe 104 0 、Volume V of shape memory alloy 301 s and the inlet volume flow rate of the driver main pipeline Q m , the specific range is limited by the formula:

[0036] The specific limit range can be adjusted according to parameters such as cycle time under different usage conditions.

[0037] Figure 4 The mechanical structure shown is to assemble the shape memory alloy 301, provide it with space for convective heat exchange with the heat exchange fluid 203, and output force and displacement. The additional filling structure 501 arranged in the pipeline can adjust the mass ratio of the heat exchange fluid 203 and the shape memory alloy 301, optimize the temperature distribution in the pipe, and reduce the heat loss through the casing.

[0038] The support frame 601 is divided into two parts, upper and lower, which can be freely disassembled. The upper part is fixed to the frame connection structure 103, and the lower part is arranged with the driving load. By changing the height of the support frame 601 and the middle pipe 104, the driver main pipe can be suitable for shape memory alloys 301 of different lengths, thereby obtaining different output displacements.

[0039] One end of the shape memory alloy 301 is fixed in the top fixed chamber 102 by a mechanical structure, and the other end is connected to the slider structure of the connecting rod-slider structure 107 in the bottom fixed chamber 106. The driver main pipe needs to be as easy to disassemble and assemble as possible under the premise of ensuring positioning accuracy and sealing performance. The fixing methods of shape memory alloys 301 of different shapes are as follows:

[0040] -For the filamentary shape memory alloy 301, the assembly method is as follows: a through hole is drilled on the side of the bolt, and after the shape memory alloy 301 passes through the through hole, nuts are tightened on both sides of the alloy. The friction force after the nuts are tightened fixes the shape memory alloy 301. When multiple materials need to be fixed, multiple through holes with parallel center lines can be drilled along the axial direction of the bolt, and each material can be separated by a gasket or nut. Bosses are left on both sides of the bolt, holes are drilled on the bosses, and the bolts are fixed in the top fixing chamber 102 through the through holes.

[0041] - For the columnar or cylindrical shape memory alloy 301, the assembly method is as follows: a ferrule is arranged outside the shape memory alloy 301, and the ferrule is deformed by mechanical coupling to be nested with the shape memory alloy 301. The shape memory alloy 301 with the ferrule is loaded onto a disk with one or more through holes, wherein the inner diameter of the through hole is larger than the outer diameter of the shape memory alloy 301 and smaller than the outer diameter of the ferrule. A positioning structure is arranged outside the disk, which is connected to the inside of the top fixed chamber 102.

[0042] - For the shape memory alloy 301 of sheet and other structures, the assembly method is as follows: Design a special fixture to fix the shape memory alloy 301. Use geometric constraints and static friction to fix the shape memory alloy 301. It should be noted that the size of the fixture should fill the internal volume of the top fixed chamber 102 as much as possible, and a through hole, i.e., a fluid channel, is reserved on the fixture so that the heat exchange fluid 203 can normally pass through the top fixed chamber 102 and enter the top outlet cover 101.

[0043] Figure 5 and Figure 6The schematic diagram of the top and bottom structures in the heat-power conversion device of the present invention is shown. In the top structure, the top fixed chamber 102 is connected to the intermediate pipe 104 by welding or threading, and after connection, it is fixed above the frame connection structure 103. The top fixed chamber 102 and the frame connection structure 103 can be connected by flanges; or by arranging a groove-boss structure, and an additional O-type rubber ring is arranged in the groove for sealing. After the top structure is assembled, it is connected to the support frame 601 by threading. During use, different displacements can be output by changing the length of the shape memory alloy 301, the intermediate pipe 104 and the support frame 601. The bottom structure is similar to the top structure, and the bottom connection structure 105 is connected to the intermediate pipe 104 by welding or threading, and then assembled and sealed with the bottom fixed chamber 106. A channel is arranged inside the bottom fixed chamber 106 to constrain the motion trajectory of the connecting rod-slider structure 107. Specifically, one side of the shape memory alloy 301 is connected to the slider structure of the connecting rod-slider structure 107. The slider structure moves in the bottom fixed bin 106, and the inner wall of the bottom fixed bin 106 constrains the movement of the slider structure to prevent it from rotating during operation, ensuring that its output is a linear motion. If there are other requirements for the output motion trajectory, different output motion trajectories can also be achieved by changing the internal profile of the bottom fixed bin 106 and the shape of the connecting rod-slider structure 107. The side wall of the bottom fixed bin 106 is arranged with a fluid inlet connector, and an additional groove is reserved inside as a fluid passage. A through hole is opened at the bottom of the bottom fixed bin 106, and a sliding seal is achieved with the connecting rod-slider structure 107 through a sealing ring and other structures.

[0044] When the heat-to-power conversion device based on low-grade heat energy driven by shape memory alloy and flow transfer fluid of the present invention is working, the driving pump 204 in the fluid alternating circulation loop drives the heat exchange fluid 203 to circulate, and the fluid alternating circulation loop is provided with a high-temperature circulation solenoid valve 207 and a low-temperature circulation solenoid valve 208. When the high-temperature circulation solenoid valve 207 is turned on, the low-temperature circulation solenoid valve 208 is turned off, and the heat exchange fluid 203 exchanges heat with the high-temperature heat sink 205. The temperature of the heat exchange fluid 203 needs to reach above 70°C, and the system is in a high-temperature state at this time; when the high-temperature circulation solenoid valve 207 is turned off and the low-temperature circulation solenoid valve 208 is turned on, the heat exchange fluid 203 exchanges heat with the low-temperature heat source 206. The temperature of the heat exchange fluid 203 is between 10°C and 30°C (ambient temperature), and the system is in a low-temperature state. In the circulation loop, the driving pump 204 is normally open, and the two solenoid valves are periodically switched on and off alternately.

[0045] After the heat exchange fluid 203 exchanges heat with the high-temperature heat sink 205, the device is in a high-temperature state, and the shape memory alloy 301 in the main pipe absorbs heat, deforms, and generates driving force. The driving force and displacement generated by the shape memory alloy 301 are output through the connecting rod-slider structure 107 through the mechanical structure transmission in the main pipe.

[0046] After the heat exchange fluid 203 exchanges heat with the low-temperature heat source 206, the shape memory alloy 301 cools down and is unloaded, and the material returns to its length before heating. At this time, by changing the mechanical connection structure, the output limit structure 401 connected to the connecting rod-slider structure 107 no longer provides the shape memory alloy 301 with a load in the opposite direction of its deformation. If the heat-to-mechanical conversion device driven by low-grade thermal energy provides a driving force to a device with a periodic change in the load direction (for example, an elastic heat refrigeration device), when the shape memory alloy 301 is unloaded, the output limit structure 401 can provide a load in the same direction as the deformation, allowing the driver to reset faster.

[0047] The shape memory alloy 301 is periodically deformed through the fluid alternating circulation loop, and the driving force and displacement are periodically output through the connecting rod-slider structure 107 in the main pipe.

[0048] The specific assembly process of the low-grade thermal energy driven heat-to-power conversion device of the present invention is as follows:

[0049] Step 1: Connect the shape memory alloy 301 to the bolts or other fixing structures in the top fixed bin 102, and fix the structure in the top fixed bin 102 by means of threaded connection or the like; then, install the output limit structure 401 and the filling structure 501 into the bottom fixed bin 106 and the intermediate pipe 104; next, connect from top to bottom: the top fixed bin 102, the frame connection structure 103, the intermediate pipe 104 to the bottom connection structure 105; then connect the unfixed end of the shape memory alloy 301 to the connecting rod-slider structure 107, and install the connecting rod-slider structure 107 into the bottom fixed bin 106; finally, install the bottom fixed bin 106, the top fixed bin 102 and the supporting frame 601, and connect the thermal driver to the fluid alternating circulation loop through the fluid alternating circulation loop inlet 201 and the fluid alternating circulation loop outlet 202 of the top fixed bin 102 and the bottom fixed bin 106.

[0050] -Step 2: Before operation, the shape memory alloy 301 needs to be pre-tightened, which can be done by applying external force using a weight or a motor.

[0051] The above description is only a preferred embodiment of the present invention and is not intended to impose any limitation on the technical solution of the present invention. Those skilled in the art should understand that, without departing from the spirit and principles of the present invention, the technical solution can also be subjected to several simple modifications and substitutions, and these modifications and substitutions are also within the scope of protection covered by the claims.

Claims

1. A thermal-mechanical conversion device driven by low-grade thermal energy, characterized in that: The invention comprises a driver main body pipeline and a fluid alternating circulation loop connected to the driver main body pipeline, wherein a driving pump (204) is arranged in the fluid alternating circulation loop, and the driving pump (204) drives a heat exchange fluid (203) to circulate in the fluid alternating circulation loop, and the fluid alternating circulation loop has parallel high and low temperature fluid branches, wherein the high temperature fluid branch is provided with a high temperature circulation solenoid valve (207) and a high temperature heat sink (205) connected in series, and the low temperature fluid branch is provided with a low temperature circulation solenoid valve (208) and a low temperature heat source (206) connected in series; a shape memory alloy (301) and a connecting rod-slider structure (107) are arranged inside the driver main body pipeline, and the driving force and displacement generated by the phase change of the shape memory alloy (301) are output through the connecting rod-slider structure (107); The driver main body pipeline comprises a top outlet cover (101), a top fixed chamber (102), a frame connection structure (103), an intermediate pipeline (104), a bottom connection structure (105) and a bottom fixed chamber (106); the top outlet cover (101) and the bottom fixed chamber (106) are both provided with fluid pipeline interfaces, and are respectively connected to the fluid alternating circulation loop outlet (202) and the fluid alternating circulation loop inlet (201); a supporting frame (601) is provided outside the driver main body pipeline, and the frame connection structure (103) is connected to the supporting frame (601). one end of the connecting rod (107) is connected and fixed; the bottom fixed bin (106) is connected to the bottom connecting structure (105), the top fixed bin (102) is connected to the frame connecting structure (103), the middle pipe (104) is connected between the bottom connecting structure (105) and the top fixed bin (102), the shape memory alloy (301) is placed in the middle pipe (104), and the two ends are respectively connected to the top fixed bin (102) and the connecting rod-slider structure (107), and the connecting rod-slider structure (107) is connected and fixed to the driving load via the output limiting structure (401); The bottom connecting rod of the connecting rod-slider structure (107) extends out of the bottom fixed bin (106), and the bottom connecting rod of the connecting rod-slider structure (107) is connected to the output limiting structure (401), and is connected to the load structure through the output limiting structure (401); The intermediate pipe (104) is equipped with a filling structure (501), and the filling structure (501) is made of a heat-insulating material and has a variable cross-sectional area structure. By controlling the cross-sectional area, the flow rate distribution of the heat exchange fluid (203) in each part of the intermediate pipe (104) is redistributed.

2. The low-grade thermal energy driven thermal-mechanical conversion device according to claim 1, characterized in that: The volume of the filling structure (501) V t The volume of the intermediate pipe (104) V 0. Volume of shape memory alloy (301) V s and the inlet volume flow rate of the actuator body pipeline Q m The following calculation formula is met: .

3. The low-grade thermal energy driven thermal-mechanical conversion device according to claim 1, characterized in that: One end of the shape memory alloy (301) is connected to a slider structure in a connecting rod-slider structure (107); the slider structure moves in a bottom fixed bin (106), and the movement of the slider structure is constrained by the inner wall of the bottom fixed bin (106).

4. The low-grade thermal energy driven thermal-mechanical conversion device according to claim 3, characterized in that: The connecting rod in the connecting rod-slider structure (107) and the bottom fixed bin (106) are sealed by a sealing ring, a positioning structure is arranged on the output limit structure (401), and the output limit structure (401) uses a weight or a motor to apply an external force to pre-tighten the shape memory alloy (301).

5. A method for assembling a low-grade thermal energy driven thermal-mechanical conversion device as claimed in any one of claims 1 to 4, characterized in that: Different assembly methods are used for shape memory alloys (301) of different shapes, including: When the shape memory alloy (301) is in the form of a wire: a through hole is drilled on the side of the bolt, and after the shape memory alloy (301) is passed through the through hole of the bolt, nuts are used to tighten the two sides of the shape memory alloy (301), and the shape memory alloy (301) is fixed by the friction force after the nuts are tightened; when multiple shape memory alloys (301) need to be fixed, multiple through holes with center lines parallel to each other are drilled along the axial direction of the bolt, and each shape memory alloy (301) is separated by a gasket or a nut; bosses are provided on both sides of the bolt, holes are drilled on the bosses, and the bolts are fixed in the top fixing chamber (102) through the through holes on the bosses; When the shape memory alloy (301) is columnar or cylindrical: a ferrule is arranged on the outside of the shape memory alloy (301), and the ferrule is deformed by mechanical coupling to be nested with the shape memory alloy (301); the shape memory alloy (301) with the ferrule is loaded onto a disk having one or more through holes, wherein the inner diameter of the through holes on the disk is larger than the outer diameter of the shape memory alloy (301) and smaller than the outer diameter of the ferrule; a positioning structure is arranged on the outside of the disk to be connected to the inside of the top fixed chamber (102); When the shape memory alloy (301) is in the form of a sheet or other structure: a special fixture is designed to fix the shape memory alloy (301), and the shape memory alloy (301) is fixed by geometric constraints and static friction; the size of the special fixture fills the internal volume of the top fixed bin (102) as much as possible, and a through hole is reserved on the special fixture as a fluid channel, through which the heat exchange fluid (203) can normally pass through the top fixed bin (102) and enter the top outlet cover (101).

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