A two-stage free piston Stirling generator

Abstract

This invention provides a two-stage free piston Stirling generator, comprising: a first cylinder; a power piston; a valve train assembly, which includes a second valve train, a first valve train, and an elastic element connecting the first and second valve trains within the first cylinder; and a heat exchange assembly. In this Stirling generator, the movement of the first valve train lags behind the second valve train by a certain phase angle due to the hysteresis effect of the elastic element. This facilitates sufficient heat exchange between most of the gaseous working fluid and the second heater, improving the generator's operating efficiency. Furthermore, the hysteresis effect of the elastic element creates a phase angle between the movements of the two valve trains, allowing the gaseous working fluid to first pass through the second regenerator into the second expansion chamber, and then through the first regenerator into the first expansion chamber, absorbing heat from the second and first heaters respectively, thereby further improving the generator's efficiency.

Description

Technical Field

[0001] The invention relates to the technical field of Stirling generators, and in particular to a two-stage free piston Stirling generator. Background Art

[0002] With the continuous growth of population and the improvement of people's living standards, the demand for energy is increasing, and fossil energy is becoming increasingly depleted; at the same time, the use of fossil energy has also led to problems such as global warming and climate change. The above contradictions have prompted people to explore new alternative energy sources, which requires more efficient energy utilization methods. As the global energy and environmental protection situation becomes increasingly severe, the Stirling engine has received more and more attention due to its wide adaptability to multiple energy sources and excellent environmental characteristics.

[0003] Stirling generator is an externally heated closed cycle piston generator. Piston Stirling generator is an important branch of Stirling generator, and is a power device that realizes thermodynamic cycle by piston reciprocating motion. The traditional two-stage harmonic reciprocating free piston Stirling generator uses a single two-stage valve piston, and the two-stage piston motion phase is the same, so it can only push part of the working gas to flow between the two-stage heat exchanger, and the heat exchange between this part of the gas and the intermediate and heat exchanger is not sufficient, while the rest of the working gas can only absorb the heat of the intermediate heat exchanger and expand outward, which leads to the heat input to the generator not being fully utilized, reducing the working efficiency of the entire generator. Summary of the invention

[0004] In view of this, the present invention proposes a two-stage free piston Stirling generator to solve or at least partially solve the technical defects existing in the prior art.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] In a first aspect, the present invention provides a two-stage free piston Stirling generator, comprising:

[0007] First cylinder;

[0008] a power piston, which is located in the first cylinder and can reciprocate in the first cylinder;

[0009] A gas distribution piston assembly, comprising a second gas distribution piston located in the first cylinder, a first gas distribution piston, and an elastic member connecting the first gas distribution piston and the second gas distribution piston, wherein the first gas distribution piston and the second gas distribution piston can both reciprocate in the first cylinder, the second gas distribution piston is close to the power piston, a compression chamber is formed between the power piston and the second gas distribution piston, a first expansion chamber is formed between the first gas distribution piston and the inner wall of the first cylinder, and a second expansion chamber is formed between the first gas distribution piston and the second gas distribution piston;

[0010] The heat exchange assembly includes a first heater, a first heat regenerator, a second heater, a second heat regenerator and a cooler which are connected in series and communicated with each other and are arranged outside the first cylinder, wherein the first heater is connected to the first expansion chamber, the second heater is connected to the second expansion chamber, and the cooler is connected to the compression chamber.

[0011] Preferably, the two-stage free piston Stirling generator further comprises:

[0012] a power piston leaf spring fixed in the first cylinder;

[0013] A power piston rod has one end connected to the power piston leaf spring and the other end connected to the power piston.

[0014] Preferably, the two-stage free piston Stirling generator further comprises:

[0015] a gas distribution piston leaf spring, which is fixed in the first cylinder;

[0016] A gas distribution piston rod, one end of which is connected to the gas distribution piston leaf spring, and the other end of which passes through the power piston and is connected to the second gas distribution piston.

[0017] Preferably, the two-stage free piston Stirling generator further comprises:

[0018] a gas distribution piston leaf spring, which is fixed in the first cylinder;

[0019] A gas distribution piston rod, one end of which is connected to the gas distribution piston leaf spring, and the other end of which passes through the power piston rod and the power piston and is connected to the second gas distribution piston.

[0020] Preferably, in the two-stage free-piston Stirling generator, the elastic member is a spring.

[0021] Preferably, the two-stage free-piston Stirling generator further includes a linear motor, which is installed outside the first cylinder and connected to the power piston.

[0022] In a second aspect, the present invention further provides a two-stage free piston Stirling generator, comprising:

[0023] A second cylinder having a power piston disposed therein, wherein the power piston can reciprocate in the second cylinder;

[0024] a third cylinder, which is in communication with the second cylinder;

[0025] A gas distribution piston assembly, comprising a second gas distribution piston located in the third cylinder, a first gas distribution piston, and an elastic member connecting the first gas distribution piston and the second gas distribution piston, wherein the first gas distribution piston and the second gas distribution piston can both reciprocate in the third cylinder, the second gas distribution piston is close to the power piston, a compression chamber is formed between the power piston and the second gas distribution piston, a first expansion chamber is formed between the first gas distribution piston and the inner wall of the third cylinder, and a second expansion chamber is formed between the first gas distribution piston and the second gas distribution piston;

[0026] The heat exchange assembly includes a first heater, a first heat regenerator, a second heater, a second heat regenerator and a cooler which are connected in series and communicated with each other and are arranged outside the third cylinder, wherein the first heater is connected to the first expansion chamber, the second heater is connected to the second expansion chamber, and the cooler is connected to the compression chamber.

[0027] The two-stage free piston Stirling generator of the present invention has the following beneficial effects compared with the prior art:

[0028] (1) The two-stage free piston Stirling generator of the present invention comprises a first gas distribution piston and a second gas distribution piston, and the first gas distribution piston and the second gas distribution piston are connected by an elastic member, and the hysteresis effect of the elastic member makes the movement of the first gas distribution piston lag behind the second gas distribution piston by a certain phase angle, which helps most of the gas working medium to fully exchange heat with the second heater, thereby improving the operating efficiency of the generator; at the same time, the two-stage free piston Stirling generator of the present invention also comprises a first expansion chamber and a second expansion chamber, and the hysteresis effect of the elastic member makes there be a certain phase angle between the movements of the two gas distribution pistons, so that the movement of the gas distribution piston is used to push the gas working medium to first pass through the second heat regenerator into the second expansion chamber, and then pass through the first heat regenerator into the first expansion chamber, thereby absorbing heat from the second heater and the first heater respectively, thereby improving the efficiency of the generator. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0030] Figure 1 A schematic diagram of the structure of a two-stage free piston Stirling generator in one embodiment of the present invention;

[0031] Figure 2 Schematic diagram of the structure of a two-stage free piston Stirling generator in another embodiment of the present invention. DETAILED DESCRIPTION

[0032] The embodiments of the present application are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be interpreted as limiting the present application.

[0033] like Figure 1 As shown, the embodiment of the present application provides a two-stage free piston Stirling generator, comprising:

[0034] First cylinder 1;

[0035] A power piston 2, which is located in the first cylinder 1 and can reciprocate in the first cylinder 1;

[0036] The gas distribution piston assembly 3 includes a second gas distribution piston 32 located in the first cylinder 1, a first gas distribution piston 31, and an elastic member 33 connecting the first gas distribution piston 31 and the second gas distribution piston 32. Both the first gas distribution piston 31 and the second gas distribution piston 32 can reciprocate in the first cylinder 1. The second gas distribution piston 32 is close to the power piston 2. A compression chamber 11 is formed between the power piston 2 and the second gas distribution piston 32. A first expansion chamber 12 is formed between the first gas distribution piston 31 and the inner wall of the first cylinder 1. A second expansion chamber 13 is formed between the first gas distribution piston 31 and the second gas distribution piston 32.

[0037] The heat exchange component includes a first heater 4, a first heat regenerator 5, a second heater 6, a second heat regenerator 7 and a cooler 8 which are connected in series and communicated with each other outside the first cylinder 1. The first heater 4 is connected to the first expansion chamber 12, the second heater 6 is connected to the second expansion chamber 13, and the cooler 8 is connected to the compression chamber 11.

[0038] It should be noted that, in the embodiment of the present application, the power piston 2, the second gas distribution piston 32 and the first gas distribution piston 31 are all located in the first cylinder 1 and can reciprocate in the first cylinder 1. A sliding seal is formed between the power piston 2 and the first cylinder 1. A gap seal is formed between the second gas distribution piston 32, the first gas distribution piston 31 and the first cylinder 1. A first expansion chamber 12 is formed between the first gas distribution piston 31 and the inner wall of the first cylinder 1. A second expansion chamber 13 is formed between the first gas distribution piston 31 and the second gas distribution piston 32. A compression chamber 11 is formed between the power piston 2 and the second gas distribution piston 32. The first expansion chamber 12, the second expansion chamber 13 and the compression chamber 11 are collectively referred to as a working chamber. When working, the working chamber is filled with a gas working medium, which may be helium, argon, hydrogen, nitrogen, air, etc. When working, the gas working medium reciprocates in the compression chamber 11, the first expansion chamber 12 and the second expansion chamber 13, and pushes the power piston 2, the second gas distribution piston 32 and the first gas distribution piston 31 to reciprocate. Since the second gas distribution piston 32 and the first gas distribution piston 31 are connected by an elastic member 33, the hysteresis effect of the elastic member 33 causes the phases of the two gas distribution pistons to be different, that is, the movement of the first gas distribution piston 31 lags behind the second gas distribution piston 32 by a certain phase angle, which helps most of the gas working fluid to fully exchange heat with the second heater 6, thereby improving the operating efficiency of the generator. Specifically, during operation, the gas working medium is heated by an external high-temperature heat source in the first heater 4; the gas working medium is heated by an external low-temperature heat source in the second heater 6, that is, the temperature of the external heat source heating the first heater 4 in the present application is higher than the temperature of the external heat source heating the second heater 6, that is, the second heater 6 is a low-temperature heater, and the first heater 4 is a high-temperature heater; the first regenerator 5 and the second regenerator 7 are both heat storage regenerators, specifically, the heat storage regenerators are both porous metal media arranged in a metal casing, for example, porous stainless steel, nickel and other porous metal media, the first regenerator 5 and the second regenerator 7 absorb the high-temperature gas working medium flowing through, and release heat to the low-temperature gas working medium flowing in the opposite direction; the gas working medium is cooled by an external cold source in the cooler 8. During use, heat with a higher temperature is provided to the first heater 4, while heat with a lower temperature is provided to the second heater 6. The above functions are realized by the second gas distribution piston 32 and the first gas distribution piston 31. The second gas distribution piston 32 and the first gas distribution piston 31 replace the gas working medium through the first heater 4, the first heat regenerator 5 and the second heater 6 connected in series. The first heater 4 and the second heater 6 operate at different temperatures. The heat with a lower temperature can be the exhaust gas from the main burner or the waste heat of other processes when used in the cogeneration device. This structure can reduce the volume of the first heater 4 and reduce the quality and cost of the generator.

[0039] The two-stage free piston Stirling generator of the present application includes a first heater 4 and a second heater 6. The heat source temperatures used by the two-stage heaters are different. The external heat source used by the two-stage heaters can be waste heat resources of different types or different temperature zones generated in daily life or industrial production processes. The heat loss generated by the first heater 4 or the high-temperature part of the generator can also be introduced into the second heater 6 for recycling with the help of a heat recovery device, thereby improving the energy utilization efficiency and making the system structure more compact.

[0040] The working process of the two-stage free piston Stirling generator of the present application is as follows: before working, the working chamber of the first cylinder 1 is filled with a gas working medium of a certain pressure. At the initial moment, the power piston 2 is at the top dead center. At this time, the gas working medium pressure in the working chamber is the highest. The gas working medium in the first expansion chamber 12 and the second expansion chamber 13 absorbs external heat from the first heater 4 and the second heater 6. The high-pressure gas expands due to heat, pushing the power piston 2 to move to the bottom dead center. The gas pressure in the working chamber decreases, but due to the continuous input of heat, this expansion process is close to an isothermal expansion process; afterwards, the second gas distribution piston 32 and the first gas distribution piston 31 move to the top dead center, but due to the action of the elastic member 33, the movement of the first gas distribution piston 31 lags behind the second gas distribution piston 32 by a certain phase angle. The first gas distribution piston 31 pushes the gas working medium from the first expansion chamber 12 through the first regenerator 5 into the second expansion chamber 13, absorbs external heat from the second heater 6 in the second expansion chamber 13, and pushes the power piston 2 to continue to move to the bottom dead center. The second gas distribution piston 32 pushes the gas working medium from the second expansion chamber 13 through the second regenerator 7 into the compression chamber 11. The gas completes the heat release process in the first regenerator 5 and the second regenerator 7, and transfers the heat to the porous metal medium in the first regenerator 5 and the second regenerator 7. The power piston 2 moves to the bottom dead center and turns to the top dead center. In this process, the power piston moves to the bottom dead center and turns to the top dead center. The volume change of the working chamber is very small, which is approximately an isochoric process. Then, the second gas distribution piston 32 and the first gas distribution piston 31 successively move to the top dead center and reverse to start moving to the bottom dead center. The movement of the first gas distribution piston 31 still lags behind the second gas distribution piston 32 by a certain phase angle. At the same time, the power piston 2 continues to move to the top dead center, and the gas is compressed in the compression chamber 11. The shrinkage heat is dissipated outwards by the cooler 8, thereby realizing an isothermal compression process; thereafter, the power piston 2 reaches the top dead center and reverses direction to start moving toward the bottom dead center, and the movement of the second valve piston 32 pushes the gas working medium from the compression chamber 11 in the reverse direction through the second regenerator 7 into the second expansion chamber 13, and the gas working medium absorbs the external heat from the second heater 6 in the second expansion chamber 13, and then under the action of the first valve piston 31, it reverses through the first regenerator 5 into the first expansion chamber 12, and this process is approximately an isochoric heating process; finally, the power piston 2 starts to move toward the bottom dead center again, and performs an isothermal expansion process, and the gas in the working chamber of the generator starts a new round of circulation. In the two-stage free piston Stirling generator of the present application, the second gas distribution piston 32 and the first gas distribution piston 31 are connected by an elastic member 33. With the help of the hysteresis effect of the elastic member 33, there is a certain phase angle between the movements of the two gas distribution pistons, so that the movement of the gas distribution pistons is used to push the gas working medium to first pass through the second heat regenerator 7 into the second expansion chamber 13, and then pass through the first heat regenerator 5 into the first expansion chamber 12, thereby absorbing the heat in the second heater 6 and the first heater 4 respectively, thereby improving the efficiency of the generator.

[0041] Specifically, in some embodiments, the first heater 4 , the first regenerator 5 , the second heater 6 , the second regenerator 7 and the cooler 8 are all sleeved on the outer periphery of the first cylinder 1 and are connected in series and communicated with each other.

[0042] In some embodiments, it also includes:

[0043] A power piston leaf spring 21, which is fixed in the first cylinder 1;

[0044] The power piston rod 22 has one end connected to the power piston leaf spring 21 and the other end connected to the power piston 2 .

[0045] In the embodiment of the present application, the power piston leaf spring 21 is a leaf spring composed of at least one piece of spring steel. The power piston leaf spring 21 is used to support the power piston 2. During the reciprocating movement of the power piston 2, the power piston leaf spring 21 will deform, thereby controlling the movement of the power piston 2.

[0046] In some embodiments, it also includes:

[0047] A gas distribution piston leaf spring 23, which is fixed in the first cylinder 1;

[0048] The gas distribution piston rod 24 has one end connected to the gas distribution piston leaf spring 23 and the other end passing through the power piston 2 and connected to the second gas distribution piston 32 .

[0049] In the embodiment of the present application, the gas distribution piston leaf spring 23 is a leaf spring composed of at least one piece of spring steel. The gas distribution piston leaf spring 23 is used to support the second gas distribution piston 32. During the reciprocating movement of the second gas distribution piston 32, the gas distribution piston leaf spring 23 will deform, thereby controlling the movement of the second gas distribution piston 32.

[0050] In some embodiments, it also includes:

[0051] A gas distribution piston leaf spring 23, which is fixed in the first cylinder 1;

[0052] The gas distribution piston rod 24 has one end connected to the gas distribution piston leaf spring 23 , and the other end passes through the power piston rod 22 and the power piston 2 and is connected to the second gas distribution piston 32 .

[0053] In some embodiments, the elastic member 33 is a spring, which may be a leaf spring, a coil spring, a torsion bar spring, a spring tube, a rubber spring, or the like.

[0054] In some embodiments, a linear motor 14 is further included, which is installed outside the first cylinder 1 and connected to the power piston 2. In the embodiment of the present application, the power piston 2 is connected to the linear motor 14, and the reciprocating motion of the power piston 2 drives the linear motor to generate electrical energy.

[0055] In some embodiments, Figure 2 As shown, the present invention also provides a two-stage free piston Stirling generator, comprising:

[0056] A second cylinder 9 is provided with a power piston 2 therein, and the power piston 2 can reciprocate in the second cylinder 9;

[0057] A third cylinder 91, which is connected to the second cylinder 9;

[0058] The gas distribution piston assembly 3 includes a second gas distribution piston 32, a first gas distribution piston 31, and an elastic member 33 connected between the first gas distribution piston 31 and the second gas distribution piston 32, which are located in the third cylinder 91. The first gas distribution piston 31 and the second gas distribution piston 32 can both reciprocate in the third cylinder 91. The second gas distribution piston 32 is close to the power piston 2. A compression chamber 11 is formed between the power piston 2 and the second gas distribution piston 32. A first expansion chamber 12 is formed between the first gas distribution piston 31 and the inner wall of the third cylinder 91. A second expansion chamber 13 is formed between the first gas distribution piston 31 and the second gas distribution piston 32.

[0059] The heat exchange assembly includes a first heater 4, a first heat regenerator 5, a second heater 6, a second heat regenerator 7 and a cooler 8 which are connected in series and communicated with each other and are arranged outside the third cylinder 91. The first heater 4 is connected to the first expansion chamber 12, the second heater 6 is connected to the second expansion chamber 13, and the cooler 8 is connected to the compression chamber 11.

[0060] In the embodiment of the present application, the power piston 2 and the second gas distribution piston 32 and the first gas distribution piston 31 are respectively located in different cylinders. Specifically, the power piston 2 is located in the second cylinder 9, the second gas distribution piston 32 and the first gas distribution piston 31 are both located in the third cylinder 91, and the second cylinder 9 is connected to the third cylinder 91 through a conduit. Please refer to the above embodiment for the specific working principle.

[0061] Specifically, in the embodiment of the present application, a power piston leaf spring 21, a power piston rod 22, a distribution piston leaf spring 23 and a distribution piston rod 24 are also provided; wherein, the power piston leaf spring 21 is fixed in the second cylinder 9, one end of the power piston rod 22 is connected to the power piston leaf spring 21, and the other end is connected to the power piston 2; the distribution piston leaf spring 23 is fixed in the third cylinder 91, one end of the distribution piston rod 24 is connected to the distribution piston leaf spring 23, and the other end is connected to the second distribution piston 32.

[0062] In some embodiments, a linear motor 14 is further included, which is installed outside the second cylinder 9 and connected to the power piston 2. In the embodiment of the present application, the power piston 2 is connected to the linear motor 14, and the reciprocating motion of the power piston 2 drives the linear motor to generate electrical energy.

[0063] The above description is only a partial implementation method of the present application. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present application. These improvements and modifications should also be regarded as the scope of protection of the present application.

Claims

1. A two-stage free piston Stirling generator, characterized in that: include: First cylinder; a power piston, which is located in the first cylinder and can reciprocate in the first cylinder; A gas distribution piston assembly, comprising a second gas distribution piston located in the first cylinder, a first gas distribution piston, and an elastic member connecting the first gas distribution piston and the second gas distribution piston, wherein the first gas distribution piston and the second gas distribution piston can both perform reciprocating motion in the first cylinder, the second gas distribution piston is close to the power piston, a compression chamber is formed between the power piston and the second gas distribution piston, a first expansion chamber is formed between the first gas distribution piston and the inner wall of the first cylinder, and a second expansion chamber is formed between the first gas distribution piston and the second gas distribution piston; the first gas distribution piston and the second gas distribution piston are connected by an elastic member, and the hysteresis effect of the elastic member causes the movement of the first gas distribution piston to lag behind that of the second gas distribution piston by a certain phase angle; The heat exchange assembly includes a first heater, a first heat regenerator, a second heater, a second heat regenerator and a cooler which are connected in series and communicated with each other and are arranged outside the first cylinder, wherein the first heater is connected to the first expansion chamber, the second heater is connected to the second expansion chamber, and the cooler is connected to the compression chamber.

2. The two-stage free-piston Stirling generator according to claim 1, characterized in that: Also includes: a power piston leaf spring fixed in the first cylinder; A power piston rod has one end connected to the power piston leaf spring and the other end connected to the power piston.

3. The two-stage free piston Stirling generator according to claim 1, characterized in that: Also includes: a gas distribution piston leaf spring, which is fixed in the first cylinder; A gas distribution piston rod, one end of which is connected to the gas distribution piston leaf spring, and the other end of which passes through the power piston and is connected to the second gas distribution piston.

4. The two-stage free-piston Stirling generator according to claim 2, characterized in that: Also includes: a gas distribution piston leaf spring, which is fixed in the first cylinder; A gas distribution piston rod, one end of which is connected to the gas distribution piston leaf spring, and the other end of which passes through the power piston rod and the power piston and is connected to the second gas distribution piston.

5. The two-stage free-piston Stirling generator according to claim 1, characterized in that: The elastic member is a spring.

6. The two-stage free-piston Stirling generator according to claim 1, characterized in that: It also includes a linear motor, which is installed outside the first cylinder and connected to the power piston.

7. A two-stage free piston Stirling generator, characterized in that: include: A second cylinder having a power piston disposed therein, wherein the power piston can reciprocate in the second cylinder; a third cylinder, which is in communication with the second cylinder; A gas distribution piston assembly, comprising a second gas distribution piston, a first gas distribution piston and an elastic member connecting the first gas distribution piston and the second gas distribution piston, the first gas distribution piston and the second gas distribution piston can both perform reciprocating motion in the third cylinder, the second gas distribution piston is close to the power piston, a compression chamber is formed between the power piston and the second gas distribution piston, a first expansion chamber is formed between the first gas distribution piston and the inner wall of the third cylinder, and a second expansion chamber is formed between the first gas distribution piston and the second gas distribution piston; the first gas distribution piston and the second gas distribution piston are connected by an elastic member, and the hysteresis effect of the elastic member makes the movement of the first gas distribution piston lag behind that of the second gas distribution piston by a certain phase angle; The heat exchange assembly includes a first heater, a first heat regenerator, a second heater, a second heat regenerator and a cooler which are connected in series and communicated with each other and are arranged outside the third cylinder, wherein the first heater is connected to the first expansion chamber, the second heater is connected to the second expansion chamber, and the cooler is connected to the compression chamber.

Images