A transcritical thermoacoustic engine

Abstract

This invention discloses a transcritical thermoacoustic engine, comprising a casing, a high-temperature heat exchange chamber on one side of the casing, a room-temperature cooling chamber on the other side of the casing, and a gas working fluid chamber at the center of the casing. A high-temperature heat exchanger is fixedly mounted in the high-temperature heat exchange chamber, a room-temperature heat exchanger is fixedly mounted in the room-temperature cooling chamber, and a thermoacoustic stack assembly is fixedly mounted in the gas working fluid chamber. The thermoacoustic stack assembly includes multiple oil-water channel plates and multiple gas channel plates fixedly mounted in the gas working fluid chamber. This invention fully utilizes the special physical properties of fluids under transcritical conditions to achieve low oscillation temperature difference and high pressure amplitude. Furthermore, the core thermoacoustic stack assembly is manufactured from a thin stainless steel plate through channel etching and diffusion welding. The channel size is on the order of hundreds of micrometers, allowing it to operate normally under high temperature and high pressure environments, meeting the requirements of transcritical conditions, achieving ideal heat exchange performance, and simultaneously achieving a compact structure, reducing the overall engine size.

Description

Technical Field

[0001] This invention relates to the field of thermoacoustic engine technology, specifically a transcritical thermoacoustic engine. Background Technology

[0002] Thermoacoustic oscillation principle is a device that generates self-excited pressure oscillations based on the principle of thermoacoustic instability. A thermoacoustic engine can be developed based on this principle, utilizing the oscillating pressure to perform work and convert thermal energy into mechanical energy. A transcritical thermoacoustic engine refers to a thermoacoustic engine operating at both supercritical and quasi-critical temperatures. According to published literature, the use of near-critical fluids in thermoacoustic engines was first suggested by Jin Tao's team at Zhejiang University in 2014. They conducted theoretical analysis on the operation of CO2 working fluid at different state points within a resonant tube, pointing out that the near-critical state can reduce acoustic power loss within the resonant tube and has certain potential. In 2017, the Compressible Fluids and Acoustics Laboratory at Purdue University, with funding from Rolls-Royce, began working on developing transcritical thermoacoustic engines. The high thermal expansion coefficient of near-critical fluids provides favorable conditions for high thermoacoustic conversion rates. Based on theoretical analysis, a prototype was developed using refrigerant R218 as the working fluid (critical pressure 2.68 MPa). By early 2019, one iteration had been completed, achieving a stable pressure amplitude of 0.69 MPa at a temperature difference of 150 K. Unlike traditional thermoacoustic engines, transcritical thermoacoustic engines operate under supercritical pressure. When the temperature crosses the critical line, the gas density changes drastically, thus generating oscillations even with a small temperature difference. To achieve supercritical pressure, a thermoacoustic engine resistant to high temperature and pressure needs to be designed. However, existing transcritical thermoacoustic engines have the following drawbacks:

[0003] Currently, most transcritical thermoacoustic engines use flat or tube bundle thermoacoustic stacks, which result in unsatisfactory heat exchange effects, make it difficult to achieve a compact structure, are difficult to manufacture, have low cost-effectiveness, and ultimately have a large size.

[0004] Therefore, we propose a transcritical thermoacoustic engine to solve the above problems. Summary of the Invention

[0005] The purpose of this invention is to provide a transcritical thermoacoustic engine to solve the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a transcritical thermoacoustic engine, comprising a casing, a high-temperature heat exchange chamber formed on one side of the casing, a room-temperature cooling chamber formed on the other side of the casing, a gas working fluid chamber formed at the center of the casing, a high-temperature heat exchanger fixedly connected in the high-temperature heat exchange chamber, a room-temperature heat exchanger fixedly connected in the room-temperature cooling chamber, and a thermoacoustic stack assembly fixedly connected in the gas working fluid chamber.

[0007] The thermoacoustic stack assembly includes multiple oil-water channel plates and multiple gas channel plates fixed in the gas working fluid cavity. The multiple oil-water channel plates and multiple gas channel plates are parallel to each other. Multiple water channel etching grooves are opened on one side of the surface of the oil-water channel plate and multiple oil channel etching grooves are opened on the other side. Multiple gas channel etching grooves are opened on the surface of the gas channel plate. Both the gas channel plate and the oil-water channel plate are made of stainless steel sheet.

[0008] Preferably, the high-temperature heat exchange chamber is connected to the gas working fluid chamber, the gas working fluid chamber is connected to the room temperature cooling chamber, one end of the shell near the high-temperature heat exchange chamber is fixed to the gas inlet and outlet, the other end is fixed to the resonant tube assembly, and the other end of the resonant tube assembly is fixed to the gas reservoir.

[0009] Preferably, a high-temperature heat transfer oil inlet pipe and a high-temperature heat transfer oil outlet pipe are fixedly connected to both sides of the shell located in the high-temperature heat exchange chamber, and a room temperature cooling water inlet pipe and a room temperature cooling water outlet pipe are fixedly connected to both sides of the shell located in the room temperature cooling chamber. The room temperature cooling water outlet pipe and the high-temperature heat transfer oil outlet pipe are located on the same side of the shell, and the high-temperature heat transfer oil inlet pipe and the room temperature cooling water inlet pipe are located on the same side of the shell.

[0010] Preferably, the high-temperature heat exchanger is connected to a gas inlet and outlet, a high-temperature heat transfer oil inlet pipe, and a high-temperature heat transfer oil outlet pipe; the room-temperature heat exchanger is connected to a room-temperature cooling water inlet pipe, a room-temperature cooling water outlet pipe, and a cold cavity; the high-temperature heat exchanger is connected to a thermoacoustic stack assembly; and the thermoacoustic stack assembly is connected to the room-temperature heat exchanger.

[0011] Preferably, the resonant tube assembly includes a horizontal section and a vertical section, the horizontal section is connected to the vertical section, the free end of the horizontal section is fixedly connected to and connected to the cold cavity, and the bottom end of the vertical section is fixedly connected to and connected to the gas reservoir.

[0012] Preferably, the high-temperature heat transfer oil inlet pipe is connected to the high-temperature heat transfer oil inlet, the high-temperature heat transfer oil outlet pipe is connected to the high-temperature heat transfer oil outlet, the room temperature cooling water inlet pipe is connected to the room temperature cooling water inlet, the room temperature cooling water outlet pipe is connected to the room temperature cooling water outlet, a first valve is fixedly connected to the gas inlet and outlet, and a second valve is fixedly connected to the gas reservoir.

[0013] Compared with the prior art, the beneficial effects of the present invention are:

[0014] This invention fully utilizes the special physical properties of fluids under transcritical conditions to achieve low starting temperature difference and high pressure amplitude. On this basis, the core thermoacoustic stack component is made of stainless steel sheet through channel etching and diffusion welding. The channel size is on the order of hundreds of micrometers, which can work normally in high temperature and high pressure environment, meet the requirements of transcritical conditions, and achieve ideal heat exchange effect. At the same time, it achieves a compact structure and reduces the overall size of the engine. Attached Figure Description

[0015] Figure 1 These are schematic diagrams of the main structure in the first, second, and third embodiments of the present invention;

[0016] Figure 2 These are schematic diagrams of the main body cross-section structure in the first, second, and third embodiments of the present invention;

[0017] Figure 3 These are schematic diagrams of the thermoacoustic stack assembly in the first and third embodiments of the present invention;

[0018] Figure 4 This is a schematic diagram of the transcritical process in the third embodiment of the present invention;

[0019] Figure 5 This is a schematic diagram of some phenomena of transcritical carbon dioxide in the third embodiment of the present invention.

[0020] In the diagram: 1. Shell; 2. High-temperature heat exchange chamber; 3. Gas working fluid chamber; 4. Room temperature cooling chamber; 5. Gas inlet and outlet; 6. Cold chamber; 7. Resonant tube assembly; 8. Gas reservoir; 9. Thermoacoustic stack assembly; 11. High-temperature heat transfer oil inlet pipe; 12. High-temperature heat transfer oil outlet pipe; 13. High-temperature heat transfer oil outlet pipe; 14. High-temperature heat transfer oil outlet pipe; 15. Room temperature cooling water inlet pipe; 16. Room temperature cooling water inlet pipe; 17. Room temperature cooling water outlet pipe; 18. Room temperature cooling water outlet pipe; 21. High-temperature heat exchanger; 41. Room temperature heat exchanger; 51. First valve; 71. Horizontal section; 72. Vertical section; 81. Second valve; 91. Oil-water passage plate; 92. Gas passage plate; 911. Water passage etching groove; 912. Oil passage etching groove; 921. Gas passage etching groove. Detailed Implementation

[0021] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] Example 1:

[0023] Please see Figure 1-3 The present invention provides a technical solution: a transcritical thermoacoustic engine, comprising a housing 1, a high-temperature heat exchange chamber 2 formed on one side of the housing 1, a room temperature cooling chamber 4 formed on the other side of the housing 1, a gas working fluid chamber 3 formed in the center of the housing 1, a high-temperature heat exchanger 21 fixedly connected in the high-temperature heat exchange chamber 2, a room temperature heat exchanger 41 fixedly connected in the room temperature cooling chamber 4, and a thermoacoustic stack assembly 9 fixedly connected in the gas working fluid chamber 3.

[0024] The thermoacoustic stack assembly 9 includes multiple oil-water channel plates 91 and multiple gas channel plates 92 fixed in the gas working fluid cavity 3. The multiple oil-water channel plates 91 and multiple gas channel plates 92 are parallel to each other. Multiple water channel etching grooves 911 are opened on one side of the surface of the oil-water channel plate 91, and multiple oil channel etching grooves 912 are opened on the other side. Multiple gas channel etching grooves 921 are opened on the surface of the gas channel plate 92. Both the gas channel plate 92 and the oil-water channel plate 91 are made of stainless steel sheet. Due to the influence of the special physical properties in the critical region, the channel width of the transcritical thermoacoustic stack should be on the order of 100 micrometers. This thermoacoustic engine makes full use of the special physical properties of the fluid under transcritical conditions to achieve low starting temperature difference and high pressure amplitude. The core thermoacoustic stack assembly 9 of the device is made of stainless steel sheet through channel etching and diffusion welding. The channel size is on the order of hundreds of micrometers. It can work normally in a high temperature and high pressure environment, meet the requirements of transcritical conditions, and the overall structure is compact and occupies very little space.

[0025] Example 2:

[0026] Please see Figure 1-2 This is the second embodiment of the present invention. This embodiment is based on the previous embodiment. The high-temperature heat exchange chamber 2 is connected to the gas working fluid chamber 3, the gas working fluid chamber 3 is connected to the room temperature cooling chamber 4, the shell 1 is fixed to the gas inlet and outlet 5 at one end near the high-temperature heat exchange chamber 2, and the other end is fixed to the resonant tube assembly 7. The other end of the resonant tube assembly 7 is fixed to the gas storage 8.

[0027] High-temperature heat transfer oil inlet pipe 11 and high-temperature heat transfer oil outlet pipe 13 are fixedly connected to both sides of the shell 1 located in the high-temperature heat exchange chamber 2, respectively. Room temperature cooling water inlet pipe 15 and room temperature cooling water outlet pipe 17 are fixedly connected to both sides of the shell 1 located in the room temperature cooling chamber 4, respectively. Room temperature cooling water outlet pipe 17 and high-temperature heat transfer oil outlet pipe 13 are located on the same side of the shell 1, and high-temperature heat transfer oil inlet pipe 11 and room temperature cooling water inlet pipe 15 are located on the same side of the shell 1.

[0028] The high-temperature heat exchanger 21 is connected to the gas inlet / outlet 5, the high-temperature heat transfer oil inlet pipe 11, and the high-temperature heat transfer oil outlet pipe 13. The room temperature heat exchanger 41 is connected to the room temperature cooling water inlet pipe 15, the room temperature cooling water outlet pipe 17, and the cold cavity 6. The high-temperature heat exchanger 21 is connected to the thermoacoustic stack assembly 9, and the thermoacoustic stack assembly 9 is connected to the room temperature heat exchanger 41.

[0029] The resonant tube assembly 7 includes a horizontal part 71 and a vertical part 72. The horizontal part 71 is connected to the vertical part 72. The free end of the horizontal part 71 is fixed and connected to the cold cavity 6. The bottom end of the vertical part 72 is fixed and connected to the air reservoir 8. Multiple pipes and housing 1 cooperate with each other to form the oil circuit, air circuit and water circuit of this engine.

[0030] The high-temperature heat transfer oil inlet pipe 11 is connected to the high-temperature heat transfer oil inlet 12 at one end, the high-temperature heat transfer oil outlet pipe 13 is connected to the high-temperature heat transfer oil outlet 14 at one end, the room temperature cooling water inlet pipe 15 is connected to the room temperature cooling water inlet 16 at one end, the room temperature cooling water outlet pipe 17 is connected to the room temperature cooling water outlet 18 at one end, the first valve 51 is fixedly connected to the gas inlet and outlet 5, and the second valve 81 is fixedly connected to the gas storage 8. After the working gas is filled, the first valve 51 and the second valve 81 can be closed to form a closed space.

[0031] Example 3:

[0032] Please see Figure 1-5 This is the third embodiment of the present invention, based on the two embodiments described above. When the present invention is running, the entire sealed standing wave thermoacoustic engine is first connected to a vacuum pump, and a vacuuming process is performed several times (at least three times) to remove the original air from the device and maintain cleanliness. Next, the gas inlet / outlet 5 is connected to a cylinder filled with carbon dioxide, and an air compressor is used to pressurize the carbon dioxide to a supercritical pressure (e.g., 7.38 MPa or higher). Then, it is injected into the transcritical standing wave gas path unit to begin operation. The present invention mainly consists of three parts: an oil path, a water path, and a gas path. The oil path consists of a high-temperature heat transfer oil inlet pipe 11, a high-temperature heat exchange chamber 2, and a high-temperature heat transfer oil outlet pipe 13. The water path consists of a room-temperature cooling water outlet pipe 17, a room-temperature cooling water inlet pipe 15, and a room-temperature cooling chamber 4. The gas path consists of a gas working fluid chamber 3 and gas inlet / outlet 5. During device operation, the high-temperature oil path provides heat input to the thermoacoustic experimental platform, maintaining the temperature at the high-temperature end. High-temperature heat transfer oil enters the high-temperature heat exchange chamber 2 directly from the high-temperature heat transfer oil inlet 12 and then exits from the high-temperature heat transfer oil outlet 13. The room-temperature water circuit design of the thermoacoustic engine is also crucial, ensuring a constant low temperature at the thermoacoustic stack's low-temperature end. Cooling water enters the room-temperature cooling chamber 4 from the room-temperature cooling water inlet 16 and then exits through the room-temperature cooling water outlet 18. Transcritical gas flows through the gas inlet / outlet 5, exchanging heat between the high-temperature heat exchange chamber 2 and the room-temperature cooling chamber 4. Heated by the high-temperature heat transfer oil and cooled by the cooling water, a temperature gradient forms in the gas working fluid chamber 3. Subsequently, the gas undergoes a transcritical process during temperature changes, resulting in strong density and drastic changes in physical properties, triggering oscillation phenomena. Please refer to the attached diagram in the instruction manual for details on the transcritical process. Figure 4 For some phenomena related to transcritical carbon dioxide in this engine, please refer to the accompanying drawings in the instruction manual. Figure 4As shown in the accompanying drawings, the closed-circuit standing-wave transcritical thermoacoustic engine of this invention can achieve the transcritical process of the gaseous working fluid under high pressure and high temperature, and the thermoacoustic oscillations generated in this process are investigated. This invention fully utilizes the special physical properties of fluids under transcritical conditions to achieve low oscillation temperature difference and high pressure amplitude. Furthermore, the core thermoacoustic stack component 9 is made of stainless steel sheet through channel etching and diffusion welding. The channel size is on the order of hundreds of micrometers, allowing it to operate normally under high temperature and high pressure, meeting the requirements of transcritical conditions, achieving ideal heat exchange, and simultaneously achieving a compact structure, reducing the overall engine size.

[0033] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A transcritical thermoacoustic engine, comprising a casing (1), characterized in that: A high-temperature heat exchange chamber (2) is opened on one side of the shell (1), a room temperature cooling chamber (4) is opened on the other side of the shell (1), a gas working fluid chamber (3) is opened in the center of the shell (1), a high-temperature heat exchanger (21) is fixedly connected in the high-temperature heat exchange chamber (2), a room temperature heat exchanger (41) is fixedly connected in the room temperature cooling chamber (4), and a thermoacoustic stack assembly (9) is fixedly connected in the gas working fluid chamber (3). The thermoacoustic stack assembly (9) includes multiple oil-water channel plates (91) and multiple gas channel plates (92) fixed in the gas working fluid cavity (3). The multiple oil-water channel plates (91) and multiple gas channel plates (92) are parallel to each other. Multiple water channel etching grooves (911) are opened on one side of the surface of the oil-water channel plate (91) and multiple oil channel etching grooves (912) are opened on the other side. Multiple gas channel etching grooves (921) are opened on the surface of the gas channel plate (92). Both the gas channel plate (92) and the oil-water channel plate (91) are made of stainless steel sheet.

2. The transcritical thermoacoustic engine according to claim 1, characterized in that: The high-temperature heat exchange chamber (2) is connected to the gas working fluid chamber (3), the gas working fluid chamber (3) is connected to the room temperature cooling chamber (4), the shell (1) is fixed to the gas inlet and outlet (5) at one end near the high-temperature heat exchange chamber (2), and fixed to the resonant tube assembly (7) at the other end, and fixed to the gas reservoir (8) at the other end of the resonant tube assembly (7).

3. A transcritical thermoacoustic engine according to claim 2, characterized in that: The shell (1) is fixed to the high temperature heat exchange chamber (2) on both sides of the shell (1) with a high temperature heat transfer oil inlet pipe (11) and a high temperature heat transfer oil outlet pipe (13) respectively. The shell (1) is fixed to the room temperature cooling chamber (4) on both sides of the shell (1) with a room temperature cooling water inlet pipe (15) and a room temperature cooling water outlet pipe (17) respectively. The room temperature cooling water outlet pipe (17) and the high temperature heat transfer oil outlet pipe (13) are located on the same side of the shell (1). The high temperature heat transfer oil inlet pipe (11) and the room temperature cooling water inlet pipe (15) are located on the same side of the shell (1).

4. A transcritical thermoacoustic engine according to claim 3, characterized in that: The high-temperature heat exchanger (21) is connected to the gas inlet and outlet (5), the high-temperature heat transfer oil inlet pipe (11), and the high-temperature heat transfer oil outlet pipe (13). The room temperature heat exchanger (41) is connected to the room temperature cooling water inlet pipe (15), the room temperature cooling water outlet pipe (17), and the cold cavity (6). The high-temperature heat exchanger (21) is connected to the thermoacoustic stack assembly (9), and the thermoacoustic stack assembly (9) is connected to the room temperature heat exchanger (41).

5. A transcritical thermoacoustic engine according to claim 2, characterized in that: The resonant tube assembly (7) includes a horizontal part (71) and a vertical part (72). The horizontal part (71) is connected to the vertical part (72). The free end of the horizontal part (71) is fixed to and connected to the cold cavity (6). The bottom end of the vertical part (72) is fixed to and connected to the gas reservoir (8).

6. A transcritical thermoacoustic engine according to claim 4, characterized in that: The high-temperature heat transfer oil inlet pipe (11) is connected to the high-temperature heat transfer oil inlet (12) at one end, the high-temperature heat transfer oil outlet pipe (13) is connected to the high-temperature heat transfer oil outlet (14) at one end, the room temperature cooling water inlet pipe (15) is connected to the room temperature cooling water inlet (16) at one end, the room temperature cooling water outlet pipe (17) is connected to the room temperature cooling water outlet (18) at one end, the first valve (51) is fixedly connected to the gas inlet and outlet (5), and the second valve (81) is fixedly connected to the gas reservoir (8).

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