Two-stroke free piston linear generator and working method

Abstract

The invention discloses a two-stroke free piston linear generator and a working method. The two-stroke free piston linear generator comprises a cylinder body and a free piston linear power generation structure. Free piston linear power generation structures are symmetrically arranged on the left side and the right side of the cylinder body. The free piston linear power generation structure comprises a free piston starting mechanism and a magnetic resistance type power generation mechanism; the cylinder body is used for temporarily storing combustible mixed gas and providing a closed working space, the combustible mixed gas is combusted to do work to provide power for the free piston starting mechanism, the free piston starting mechanism does linear reciprocating motion in a two-stroke mode, and then the magnetic resistance type power generation mechanism converts linear motion mechanical energy into electric energy. The symmetrical free piston starting mechanisms are adopted, the problems that an existing free piston linear generator is poor in vibration characteristic and combustion cycles influence one another are solved, the magnetic resistance type power generation mechanism is adopted, the problem that a permanent magnet loses efficacy at the high temperature is avoided, premixed gas serves as a gas spring to increase the compression ratio of the mixed gas, and the energy efficiency is improved. The combustion efficiency is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of power generation devices, and particularly relates to a two-stroke free piston linear generator and a working method thereof. Background Art

[0002] A free piston linear generator is a power generation device composed of a free piston internal combustion engine and a linear generator. It converts the chemical energy of fuel into heat energy through combustion, then converts the heat energy into mechanical energy through the expansion work of high-temperature and high-pressure gas in the cylinder, and finally converts the mechanical energy of the reciprocating motion of the piston into electrical energy through the linear generator. The free piston linear generator abandons the crank connecting rod mechanism of the traditional engine. Compared with the traditional engine, it has the advantages of high thermal efficiency, variable compression ratio, wide fuel adaptability, etc. As a power generation device with great potential, it has gradually received wide attention.

[0003] The free piston internal combustion engine has no crank connecting rod mechanism. The piston only makes reciprocating linear motion inside the cylinder block and the stroke is not mechanically restricted. Compared with the traditional internal combustion engine, it has the advantages of simple structure, small volume, light weight, easy start and stop, etc.; the linear generator is a power generation device that directly converts mechanical energy into electrical energy. It does not require intermediate rotating components. Through the interaction between the linearly moving magnetic field and the conductor, the conductor cuts the magnetic induction line to generate induced electromotive force and induced current, and has the characteristics of simple structure, high transmission efficiency, fast response speed, etc.; the reluctance generator is based on the reluctance effect and the principle of electromagnetic induction. When the mover moves relative to the stator, it will cause the magnetic reluctance of the closed magnetic circuit to change. The stator winding generates a magnetic field under the action of the exciting current. The change in magnetic reluctance caused by the movement of the mover makes the magnetic flux passing through the stator winding change, and then induces electromotive force and induced current in the stator winding. It has the advantages of simple structure, no permanent magnet and complex winding structure, high reliability, low cost, high energy conversion efficiency, fast dynamic response speed, etc. The existing technical solutions of free piston linear generators mostly use double-piston internal combustion engines as prime movers, that is, two free piston engines are placed on both sides of the linear generator, and jointly push a set of generator movers installed on the connecting rod to reciprocate to achieve the relative motion of cutting the magnetic force line. In this design, the movement directions of the two pistons are the same and they need to rely on each other to complete their respective compression strokes, resulting in problems such as poor vibration characteristics and mutual influence of combustion cycles; a large amount of heat will be generated during the working process of the free piston engine. Under the action of heat conduction and heat radiation on the cylinder wall, the temperatures of the linear motor and the engine will rise. If the permanent magnet is used for the mover of the linear motor, demagnetization failure may occur.

[0004] In view of the above problems, the present invention proposes to adopt a two-stroke free piston linear generator combined with reluctance power generation technology to avoid the problems of poor vibration characteristics and mutual influence of combustion cycles in the existing free piston generators and the demagnetization failure of the permanent magnet of the generator at high temperatures. Summary of the Invention

[0005] The object of the present invention is to provide a two-stroke free piston linear generator and a working method for the above deficiencies, to solve the problems of poor vibration characteristics and mutual influence of combustion cycles in the existing free piston linear generators, to avoid the problem of permanent magnet failure at high temperatures, and to increase the compression ratio of the mixture on the basis of using the premixed gas as a gas spring to improve the combustion efficiency. To achieve the above object, the present invention provides the following technical solutions:

[0006] A two-stroke free piston linear generator, characterized in that: it includes a cylinder block and a free piston linear power generation structure; the left and right sides of the cylinder block are symmetrically provided with free piston linear power generation structures; the free piston linear power generation structure includes a free piston engine structure and a reluctance power generation structure; the cylinder block is used to temporarily store the combustible mixture gas and provide a closed working space, and provides power for the free piston engine structure through the combustion work of the combustible mixture gas, so that the free piston engine structure makes a linear reciprocating motion in a two-stroke mode, and the reluctance power generation structure then converts the linear motion mechanical energy into electrical energy.

[0007] Further, the cylinder block includes a combustion chamber; a spark plug is provided in the combustion chamber; a first exhaust valve and a first intake valve are respectively provided on both side walls of the combustion chamber.

[0008] Further, the cylinder block further includes a premixing chamber; premixing chambers are provided on both the left and right sides of the combustion chamber; a movable compression plate is provided between the premixing chamber and the combustion chamber and is separated by the compression plate; the compression plate is connected to the free piston engine structure; a second intake valve and a second exhaust valve are respectively provided on both side walls of the premixing chamber; the first exhaust valve and the second intake valve are on the same side, and the first intake valve and the second exhaust valve are on the same side; an intake channel is provided on the outer wall between the combustion chamber and the premixing chamber; the combustion chamber and the premixing chamber are respectively communicated with the intake channel through the first intake valve and the second exhaust valve; a fuel nozzle and a pressure sensor are provided in the premixing chamber.

[0009] Further, a pressure balance passage is provided outside between the premixing chambers on both sides of the combustion chamber; a pressure balance valve is provided at the connection of the premixing chamber wall and the pressure balance passage.

[0010] Further, the free piston engine structure includes a piston and a piston rod; the piston is arranged in the combustion chamber and is fixedly connected to the compression plate; one end of the piston rod passes through the chamber wall opposite to the compression plate and the compression plate in the premixing chamber in sequence and then is connected to the piston; a distance sensor is provided on the piston rod.

[0011] Further, the magnetoresistive power generation mechanism includes a rotor iron core, a stator iron core, and windings; the cylinder block further includes a power generation chamber; a power generation chamber is provided on the side of the premixing chamber away from the combustion chamber; part of the piston rod is located in the power generation chamber, and the other end passes through the chamber wall of the power generation chamber; a plurality of rotor iron cores are provided on the side wall of the piston rod; a plurality of stator iron cores are provided at positions corresponding to the rotor iron cores on the chamber wall of the power generation chamber; windings are wound around the stator iron cores.

[0012] Further, a rotor yoke is provided between the piston rod and the rotor iron core; a stator yoke is provided between the stator iron core and the chamber wall of the power generation chamber.

[0013] Further, a cooling mechanism is further included; the cooling mechanism includes an encapsulation sleeve, a circulation pump, a radiator, and a circulation pipeline; the encapsulation sleeve is arranged on the outer side wall of the cylinder block, filled with a coolant inside, and is provided with a temperature sensor; the encapsulation sleeve is connected to the radiator through the circulation pipeline; a circulation pump is provided on the circulation pipeline.

[0014] Further, an electrical mechanism is further included; the electrical mechanism includes an excitation power supply unit, a power conversion unit, a control unit, and a load unit; the power conversion unit is electrically connected to the excitation power supply unit, the control unit, the load unit, and the windings respectively.

[0015] A working method of the above two-stroke free piston linear generator includes the following steps:

[0016] Step S1, the first stroke, top dead center → bottom dead center, the spark plug ignites, the gas in the combustion chamber is ignited, the expanding gas pushes the pistons on both sides to move from the top dead center to the bottom dead center, the second exhaust valve of the premixing chamber opens, when the piston moves just enough not to block the first exhaust valve of the combustion chamber, the first exhaust valve opens; when the piston moves just enough not to block the first intake valve of the combustion chamber, the first intake valve opens; the first exhaust valve and the first intake valve close after remaining open for a period of time, and at the same time the second exhaust valve closes, and the piston continues to move downward to compress the gas in the premixing chamber until it reaches the bottom dead center.

[0017] Step S2, the second stroke, bottom dead center → top dead center, after the piston reaches the bottom dead center, under the action of the compressed gas, it moves from the bottom dead center to the top dead center. When the air pressure in the premixing chamber is lower than the set value p1, the control unit controls the excitation power supply unit to energize the windings through the power conversion unit to assist the piston to continue moving upward to the top dead center until the air pressure value is lower than the set value p2, the second intake valve and the second exhaust valve open, and at the same time the fuel nozzle opens. When the piston is about to reach the top dead center, the spark plug ignites, and the piston finally reaches the top dead center under the action of inertia, and then moves from the top dead center to the bottom dead center under the action of gas expansion, repeating step S1.

[0018] The beneficial effects of the present invention are:

[0019] The present invention discloses a two-stroke free piston linear generator and a working method thereof, including a cylinder block and a free piston linear power generation structure; the left and right sides of the cylinder block are symmetrically provided with free piston linear power generation structures; the free piston linear power generation structure includes a free piston engine structure and a reluctance power generation structure; the cylinder block is used to temporarily store a combustible mixture and provide a closed working space, and the combustible mixture burns and does work to provide power for the free piston engine structure, so that the free piston engine structure makes a linear reciprocating motion in a two-stroke mode, and the reluctance power generation structure then converts the linear motion mechanical energy into electrical energy. The present invention adopts a symmetrical free piston engine structure to solve the problems of poor vibration characteristics and mutual influence of combustion cycles in existing free piston linear generators, and adopts a reluctance power generation structure to avoid the problem of permanent magnet failure at high temperatures, and increases the compression ratio of the mixture on the basis of using the premixed gas as a gas spring to improve the combustion efficiency. Description of the Drawings

[0020] Figure 1 is a schematic structural diagram of the two-stroke free piston linear generator of the present invention;

[0021] In the drawings: 1 - cylinder block, 2 - free piston engine structure, 3 - reluctance power generation structure, 4 - combustion chamber, 5 - first exhaust valve, 6 - first intake valve, 7 - premixing chamber, 8 - second intake valve, 9 - second exhaust valve, 10 - compression plate, 11 - intake passage, 12 - pressure balance passage, 13 - pressure balance valve, 14 - spark plug, 15 - fuel nozzle, 16 - piston, 17 - piston rod, 18 - piston ring, 19 - sliding bearing, 20 - mover core, 21 - stator core, 22 - stator yoke, 23 - mover yoke, 24 - winding, 25 - power generation chamber, 26 - cooling mechanism, 27 - encapsulation sleeve, 28 - circulation pump, 29 - radiator, 30 - circulation pipeline, 31 - excitation power supply unit, 32 - power conversion unit, 33 - control unit, 34 - load unit, 35 - pressure sensor, 36 - distance sensor, 37 - temperature sensor. Detailed Embodiments

[0022] Hereinafter, exemplary embodiments of the present disclosure will be described in more detail with reference to the drawings. Although the exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided so that the present disclosure can be more thoroughly understood and the scope of the present disclosure can be completely conveyed to those skilled in the art.

[0023] It should be understood that the terms used herein are for the purpose of describing particular example embodiments only and are not intended to be limiting. Unless the context clearly dictates otherwise, the singular forms "a", "an", and "the" as used herein may also include the plural forms. The terms "comprising", "including", "containing", and "having" are inclusive and thus specify the presence of the stated features, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, steps, operations, elements, components, and / or combinations thereof. The method steps, processes, and operations described herein are not to be construed as necessarily requiring their performance in the particular order described or illustrated, unless explicitly indicated as the order of performance. It should also be understood that additional or alternative steps may be used.

[0024] Although the terms first, second, third, etc. may be used herein to describe multiple elements, components, regions, layers, and / or sections, these elements, components, regions, layers, and / or sections should not be limited by these terms. These terms may be used only to distinguish one element, component, region, layer, or section from another. Unless the context clearly indicates otherwise, terms such as "first", "second", and other numerical terms when used herein do not imply an order or sequence. Thus, the first element, component, region, layer, or section discussed below may be referred to as the second element, component, region, layer, or section without departing from the teachings of the example embodiments.

[0025] For ease of description, spatial relative relation terms may be used herein to describe the relationship of one element or feature shown in the figures to another element or feature, such as "inside", "outside", "inner side", "outer side", "below", "beneath", "above", "upper", etc. The meaning of such spatial relative relation terms includes different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is flipped, an element described as "below" or "beneath" other elements or features will then be oriented "above" or "upper" other elements or features. Thus, the example term "below" can include both the upper and lower orientations. The device may be otherwise oriented (rotated 90 degrees or in other directions) and the spatial relative relation descriptors used herein are to be interpreted accordingly.

[0026] Example 1

[0027] See the appendix Figure 1。The two-stroke free-piston linear generator of the present invention includes a cylinder block 1 and a free-piston linear power generation structure. The free-piston linear power generation structures are arranged on the left and right sides of the cylinder block 1, and the free-piston linear power generation structures are axisymmetric about the center axis of the cylinder block 1. The free-piston linear power generation structure includes a free-piston engine mechanism 2 and a reluctance power generation mechanism 3. The cylinder block 1 is used to temporarily store the combustible mixture and provide a closed working space. Through the combustible mixture, the gas expansion provides power for the free-piston engine mechanism 2, so that the free-piston engine mechanism 2 makes a linear reciprocating motion in a two-stroke mode. The motion directions of the free-piston engine mechanisms 2 on the left and right sides of the cylinder block 1 are opposite, so that the magnetic flux of the reluctance power generation mechanism 3 changes to generate an induced electromotive force and an induced current, and the linear motion mechanical energy of the free-piston engine mechanism 2 is converted into electrical energy. The two-stroke free-piston linear generator of the present invention adopts a symmetrically arranged free-piston engine mechanism 2, and the opposite free-piston engine mechanisms 2 move in opposite directions, with self-balanced structure and good vibration characteristics. And the reluctance power generation mechanism 3 is adopted to avoid the demagnetization failure of the permanent magnet at high temperature, and improve the environmental adaptability of the two-stroke free-piston linear generator of the present invention.

[0028] Specifically, as shown in the attached Figure 1 figure, the cylinder block 1 can be a long cuboid including a combustion chamber 4 and two pre-mixing chambers 7. The combustion chamber 4 is located in the middle position, and the two pre-mixing chambers 7 are arranged on the left and right sides of the combustion chamber 4 and are axisymmetric about the center axis of the combustion chamber 4. The pre-mixing chamber 7 and the combustion chamber 4 are separated by a compressible plate 10 that can move left and right. The compressible plate 10 is connected to the free-piston engine mechanism 2 and moves with the free-piston engine mechanism 2. It can be understood that as the compressible plate 10 moves, the volume of the combustion chamber 4 increases or decreases, and the volume of the pre-mixing chamber 7 decreases or increases. A first exhaust valve 5 and a first intake valve 6 are respectively arranged on the two side walls of the combustion chamber 4, and a second intake valve 8 and a second exhaust valve 9 are respectively arranged on the two side walls of the pre-mixing chamber 7. The first exhaust valve 5 and the second intake valve 8 are on the same side, and the first intake valve 6 and the second exhaust valve 9 are on the same side. As shown in the attached Figure 1As shown in the figure, two symmetric first exhaust valves 5 can be arranged at the top of the combustion chamber 4, and two symmetric first intake valves 6 can be arranged at the bottom. A second intake valve 8 is provided at the top of the premixing chamber 7, and a second exhaust valve 9 is provided at the bottom. A fuel nozzle 15 and a pressure sensor 35 are arranged in the premixing chamber 7. The fuel nozzle 15 supplies fuel to the premixing chamber 7, and air enters the premixing chamber 7 from the second intake valve 8 and mixes with the supplied fuel. An intake passage 11 is provided on the outer wall between the combustion chamber 4 and the premixing chamber 7. The intake passage 11 is located at the bottom of the cylinder block 1. The mixed combustible gas in the premixing chamber 7 passes through the second exhaust valve 9, the intake passage 11, and finally enters the combustion chamber 4 from the first intake valve 6. A spark plug 14 is arranged in the combustion chamber 4, and the spark plug 14 is used to ignite the combustible gas in the combustion chamber 4. A spark plug 14 can be arranged at both the bottom and the top of the combustion chamber 4. The spark plug 14 is located on the central axis of the combustion chamber 4. The first exhaust valve 5 is closer to the spark plug 14 than the first intake valve 6. Through this symmetric arrangement, the present invention further makes the forces exerted by the gas expansion on the two sides of the free piston engine mechanism 2 equal in magnitude and opposite in direction, ensuring the self - balance of the structure. The pressure sensor 35 is used to detect the gas pressure in the premixing chamber 7 and is used to judge whether to supply air and fuel to the premixing chamber 7.

[0029] Specifically, an external pressure balance passage 12 is provided between the left and right premixing chambers 7. The left and right premixing chambers 7 can be connected through the pressure balance passage 12. A pressure balance valve 13 is provided on the wall of the premixing chamber 7 at the connection of the pressure balance passage 12 and the premixing chamber 7. When the pressure difference between the gases in the two premixing chambers 7 on both sides exceeds the set value due to external factors, the pressure balance valve 13 is opened to connect the two premixing chambers 7 to balance the air pressures on both sides.

[0030] Specifically, the free piston engine mechanism 2 includes a piston 16 and a piston rod 17. The piston 16 is disposed in the combustion chamber 4 and fixedly connected to the compression plate 10. One end of the piston rod 17 sequentially passes through the chamber wall of the pre-mixing chamber 7 opposite to the compression plate 10 and the compression plate 10, and then is connected to the piston 16. A piston ring 18 is provided between the piston 16 and the wall of the combustion chamber 4. A groove can be provided on the side wall of the piston 16, and the piston ring 18 is provided in the groove to isolate the combustible gas in the combustion chamber 4 and prevent leakage. After the combustible gas in the combustion chamber 4 is ignited, the gas expands and pushes the pistons 16 on both sides to move in opposite directions. For example, the left piston 16 moves linearly to the left, and the right piston 16 moves linearly to the right. The compression plate 10 moves with the piston 16 on the same side, and can compress the combustible gas in the pre-mixing chamber 7. When the piston 16 stops moving, the pressure potential energy accumulated during the compression of the combustible gas is released, acting on the compression plate 10, which can push the compression plate 10 to move in the opposite direction, and the piston 16 moves accordingly. At this time, the left piston 16 moves linearly to the right, and the right piston 16 moves linearly to the left, and at the same time, the combustible gas in the combustion chamber 4 is compressed again. In the present invention, the combustible gas in the pre-mixing chamber 7 is also used as a gas spring, which not only increases the compression ratio of the combustible mixture, but also reduces the use of redundant components.

[0031] Specifically, the reluctance type power generation mechanism 3 includes a rotor iron core 20, a stator iron core 21 and a winding 24. A power generation chamber 25 is provided on the side of the pre-mixing chamber 7 away from the combustion chamber 4. A part of the piston rod 17 is located in the power generation chamber 25, and the other end passes through the chamber wall of the power generation chamber 25 and is located outside the cylinder block 1. A rotor yoke 23 is provided on the side wall of the piston rod 17, and a plurality of rotor iron cores 20 are provided on the rotor yoke 23. A stator yoke 22 is provided at a position corresponding to the rotor yoke 23 on the chamber wall of the power generation chamber 25. A plurality of stator iron cores 21 are provided on the stator yoke 22, and a winding 24 is wound on the stator iron core 21. Among them, the rotor iron core 20 and the stator iron core 21 are usually laminated by ferromagnetic materials with good magnetic conductivity, and both the stator yoke 22 and the rotor yoke 23 are made of materials with good magnetic conductivity, providing a low magnetic resistance path for the magnetic field of the reluctance type power generation mechanism 3. As the piston rod 17 makes a reciprocating linear motion, the magnetic flux changes to generate an induced current. A sliding bearing 19 is provided on the chamber wall of the pre-mixing chamber 7 corresponding to the compression plate 10 and the chamber wall of the power generation chamber 25. The sliding bearing 19 is located at the penetration of the piston rod 17 and sleeved on the outside of the piston rod 17 to reduce the frictional resistance between the piston rod 17 and each chamber wall during the reciprocating motion. A distance sensor 36 is provided on the piston rod 17. The distance sensor 36 can be located on one side of the rotor yoke 23. The distance sensor 36 is used to detect the distance between the distance sensor 36 and the chamber wall of the power generation chamber 25 on the same side, where the chamber wall of the power generation chamber 25 is the chamber wall on the side away from the pre-mixing chamber 7.

[0032] Specifically, the two-stroke free piston linear generator of the present invention further includes an electrical mechanism and a cooling mechanism 26. The cooling mechanism 26 includes a packaging sleeve 27, a circulation pump 28, a radiator 29, and a circulation pipeline 30. The packaging sleeve 27 is arranged on the outer wall of the cylinder block 1 and avoids the first exhaust valve 5 and the second intake valve 8. The interior of the packaging sleeve 27 is filled with a coolant. The packaging sleeve 27 is connected to the radiator 29 through the circulation pipeline 30. The circulation pump 28 is provided on the circulation pipeline 30. The coolant in the packaging sleeve 27 cools the cylinder block 1 and then heats up. Under the action of the circulation pump 28, it flows through the radiator 29 to take away the heat exchanged by the coolant. The coolant cools down and then returns to the packaging sleeve 27 through the circulation pipeline 30 to continue cooling the cylinder block 1. A temperature sensor 37 is provided in the packaging sleeve 27 to detect the temperature of the coolant. When the temperature of the coolant is higher than the set value, the circulation pump 28 is started.

[0033] Specifically, the two-stroke free piston linear generator of the present invention further includes an electrical mechanism. The electrical mechanism includes an excitation power supply unit 31, a power conversion unit 32, a control unit 33, and a load unit 34. The power conversion unit 32 is electrically connected to the excitation power supply unit 31, the control unit 33, the load unit 34, and the winding 24 respectively. The power conversion unit 32 plays a key role in energy conversion and control. After the excitation power supply unit 31 first performs power conversion through the power conversion unit 32, it provides an excitation current for the winding 24 to work. Moreover, the excitation power supply can also receive the charging current returned through the power conversion unit 32 after the generator of the present invention operates normally. The current generated when the generator of the present invention operates normally is regulated by the power conversion unit 32 for parameters such as its amplitude, frequency, and phase, and is supplied to the load unit 34. The control unit 33 is used to receive the signals of the pressure sensor 35, the distance sensor 36, and the coolant temperature sensor 37, and control the opening and closing of the first exhaust valve 5, the first intake valve 6, the second exhaust valve 9, the second intake valve 8, the pressure balance valve 13, and the circulation pump 28 according to the received signals.

[0034] Embodiment 2

[0035] The working method of the two-stroke free piston linear generator of Embodiment 1 includes the following steps.

[0036] Step S1, the first stroke, top dead center → bottom dead center, as shown in the appendix Figure 1As shown, the piston rod 17 on the left moves from right to left, and the piston rod 17 on the right moves from left to right. When the piston 16 is near the top dead center, the distance between the distance sensor 36 on the piston rod 17 and the wall of the cylinder block 1 on the same side is L5. According to the actual working conditions, this relative distance is set as L5. At this time, the relative positions of the two pistons 16 should be close to the spark plug 14, with the piston 16 on the left being on the right side of the first exhaust valve 5 close to it and the piston 16 on the right being on the left side of the first exhaust valve 5 close to it. When the distance sensor 36 sends back L5 to the control unit 33, the control unit controls the spark plug 14 to ignite, and the gas in the combustion chamber 4 is ignited. The expanding gas will push the pistons 16 on both sides to move from the top dead center to the bottom dead center. At this time, the first exhaust valve 5, the first intake valve 6, and the second intake valve 8 are closed, and the second exhaust valve 9 is open; the piston 16 moves towards the bottom dead center and drives the compression plate 10 to compress the gas in the premixing chamber 7. When the piston 16 just stops blocking the first exhaust valve 5 in the combustion chamber 4, that is, the piston 16 on the left moves to the left side of the first exhaust valve 5 close to it and the piston 16 on the right moves to the right side of the first exhaust valve 5 close to it. At this time, the distance between the distance sensor 36 on the piston rod 17 and the wall of the cylinder block 1 on the same side is L2. When the distance sensor 36 sends back L2 to the control unit 33, the control unit controls the first exhaust valve 5 to open, and the exhaust gas in the combustion chamber 4 is discharged from the combustion chamber 4 under the action of its own remaining pressure; the piston 16 continues to move towards the bottom dead center until it stops blocking the first intake valve 6 in the combustion chamber 4, that is, the piston 16 on the left moves to the left side of the first intake valve 6 close to it and the piston 16 on the right moves to the right side of the first intake valve 6 close to it. The distance between the distance sensor 36 on the piston rod 17 and the wall of the cylinder block 1 on the same side is L3. When the distance sensor 36 sends back L3 to the control unit 33, the control unit controls the first intake valve 6 to open, and the premixing chamber 7 and the combustion chamber 4 are connected. The compressed gas in the premixing chamber 7 enters the combustion chamber 4 through the intake channel 11, replenishing the combustible mixture in the combustion chamber 4 and purging out the residual exhaust gas; after the first exhaust valve 5 and the first intake valve 6 remain open for a time t1, they are closed, and at the same time, the second exhaust valve 9 is also closed. t1 is a value set according to the actual working conditions. The piston 16 continues to move towards the bottom dead center, and the compression plate 10 continues to compress the remaining gas in the premixing chamber 7 until it stops. This position is the bottom dead center, and at this time, the distance between the distance sensor 36 on the piston rod 17 and the wall of the cylinder block 1 on the same side is L4, which can be detected by the distance sensor 36.

[0037] Step S2, second stroke, bottom dead center → top dead center. After the piston 16 reaches the bottom dead center, the compressed gas in the pre-mixing chamber 7 will act as a gas spring, applying a force to the piston 16 to push the piston 16 to move from the bottom dead center to the top dead center. Since the compression plate 10 moves with the piston 16, the volume of the pre-mixing chamber 7 increases, and the air pressure in the pre-mixing chamber 7 becomes lower and lower. The pressure in the pre-mixing chamber 7 can be measured by the pressure sensor 35. When the air pressure transmitted back by the pressure sensor 35 to the control unit 33 is lower than the set value p1 (p1 is set according to the actual working conditions), the reluctance power generation mechanism 3 switches from the power generation mode to the motor working mode. At this time, the excitation power supply unit 31 is disconnected from the external load, and the control unit 33 controls the excitation power supply unit 31 to energize the winding 24 through the power conversion unit 32, applying a magnetic pulling force to the mover iron core 20. Under the action of the magnetic pulling force, the mover iron core 20 drives the piston 16 to continue moving towards the top dead center. The air pressure in the pre-mixing chamber 7 continues to decrease until the air pressure transmitted back by the pressure sensor 35 to the control unit 33 is lower than the set value p2 (p2 is set according to the actual working conditions). Then, the second intake valve 8, the second exhaust valve 9, and the fuel nozzle 15 are controlled to open. While replenishing air into the pre-mixing chamber 7, fuel is replenished into the pre-mixing chamber 7 by the fuel nozzle 15. The piston 16 continues to move towards the top dead center. When the piston 16 is about to reach the top dead center, that is, when the distance sensor 36 transmits back L5 to the control unit 33, the spark plug 14 ignites. At this time, the reluctance power generation mechanism 3 switches from the motor working mode to the power generation mode, and the excitation power supply unit 31 is connected to the external load. The piston 16 will continue to move a short distance in the original direction under the action of inertia and finally reach the top dead center. At this time, the distance between the distance sensor 36 on the piston rod 17 and the opposite cylinder wall 1 on the same side is L1, which can be detected by the distance sensor 36. Then, under the action of gas expansion, it starts to move from the top dead center to the bottom dead center, repeating step S1.

[0038] Starting process of the two-stroke free piston linear generator of the present invention:

[0039] When the piston 16 was last at any position in the cylinder block 1 and the generator of the present invention is to be started, the exciting power supply unit 31 is first energized as the starting power supply. The distance sensor 36 detects the distance between the distance sensor 36 and the wall of the cylinder block 1 on the same side and transmits it back to the control unit 33. The control unit 33 calculates the positional relationship between the mover core 20 and the stator core 21 and the position of the piston 16 in the combustion chamber 4. During the starting process of the reluctance power generation mechanism 3, it is in the motor working mode. After the initial relative positional relationship is determined, the control unit 33 issues commands for the energization sequence and energization duration of each phase winding 24. After receiving this command, the power conversion unit 32 controls the exciting power supply unit 31 to energize the winding 24. The mover core 20 drives the piston rod 17 and the piston 16 to start linear motion under the action of the magnetic pulling force. The control unit 33 records the motion state of the piston 16 at the previous shutdown. After starting, the acting direction of the magnetic pulling force is the same as the motion direction of the piston 16 before shutdown. For example, when the piston 16 is in the process of moving from the bottom dead center to the top dead center at shutdown, for the left piston rod 17, the magnetic pulling force direction is to the right at startup, and for the right piston rod 17, the magnetic pulling force direction is to the left. The opening sequence of each valve is determined by imitating the distance parameters L1 - L5 transmitted back by the distance sensor 36 during normal operation until the piston 16 moves near the top dead center and is ignited by the spark plug 14, and the generator of the present invention returns to normal, repeating the above steps S1 and S2.

[0040] In addition, when the values transmitted back by the distance sensors 36 on the left and right sides are inconsistent, that is, when the pistons 16 on the left and right sides perform asymmetric motion, when the reluctance power generation mechanism 3 switches from the power generation mode to the motor working mode, the magnitude of the energization current, the duration of energization, or the energization sequence of the winding 24 can be controlled to adjust the motion states of the pistons 16 on the left and right sides, so that the motions of the pistons 16 on the left and right sides tend to be symmetric.

[0041] All technical features in this embodiment can be freely combined according to actual needs. The above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the purpose and scope of the technical solutions of the present invention, and they should all be covered within the scope of the claims of the present invention. The technologies, shapes, and structures not described in detail in the present invention are all well-known technologies.

[0042] The above embodiments are the preferred implementation solutions of the present invention. In addition, there are other implementation methods. Any obvious replacement without departing from the concept of the technical solution is within the protection scope of the present invention.

Claims

1. A two-stroke free piston linear generator, characterized in that: The invention comprises a cylinder body (1) and a free piston linear power generation structure; the free piston linear power generation structure is symmetrically arranged on the left and right sides of the cylinder body (1); the free piston linear power generation structure comprises a free piston starting mechanism (2) and a magnetic resistance type power generation mechanism (3); the cylinder body (1) is used to temporarily store a combustible mixed gas and provide a closed working space, and the combustible mixed gas is burned to do work to provide power for the free piston starting mechanism (2), so that the free piston starting mechanism (2) performs linear reciprocating motion in a two-stroke mode, and the magnetic resistance type power generation mechanism (3) then converts the mechanical energy of the linear motion into electrical energy.

2. The two-stroke free piston linear generator according to claim 1, characterized in that: The cylinder body (1) comprises a combustion chamber (4); a spark plug (14) is arranged in the combustion chamber (4); and a first exhaust valve (5) and a first intake valve (6) are respectively arranged on two side walls of the combustion chamber (4).

3. The two-stroke free piston linear generator according to claim 2, characterized in that: The cylinder body (1) further comprises a premixing chamber (7); the premixing chamber (7) is provided on both the left and right sides of the combustion chamber (4); a movable compression plate (10) is provided between the premixing chamber (7) and the combustion chamber (4), and the premixing chamber (7) and the combustion chamber (4) are separated by the compression plate (10); the compression plate (10) is connected to the free piston engine mechanism (2); a second intake valve (8) and a second exhaust valve (9) are provided on the two side walls of the premixing chamber (7); the first exhaust valve (5) and the second intake valve (8) are located on the same side, and the first intake valve (6) and the second exhaust valve (9) are located on the same side; an intake cavity (11) is provided on the outer wall between the combustion chamber (4) and the premixing chamber (7); the combustion chamber (4) and the premixing chamber (7) are connected to the intake cavity (11) through the first intake valve (6) and the second exhaust valve (9) respectively; a fuel nozzle (15) and a pressure sensor (35) are provided in the premixing chamber (7).

4. The two-stroke free piston linear generator according to claim 3, characterized in that: An external pressure balancing passage (12) is provided between the premixing chambers (7) on both sides of the combustion chamber (4); a pressure balancing valve (13) is provided at the connection between the wall of the premixing chamber (7) and the pressure balancing passage (12).

5. The two-stroke free piston linear generator according to claim 3, characterized in that: The free piston engine mechanism (2) comprises a piston (16) and a piston rod (17); the piston (16) is arranged in a combustion chamber (4) and fixedly connected to a compression plate (10); one end of the piston rod (17) passes through a chamber wall of a premixing chamber (7) opposite to the compression plate (10) and the compression plate (10) in sequence, and is connected to the piston (16); a distance sensor (36) is provided on the piston rod (17).

6. The two-stroke free piston linear generator according to claim 5, characterized in that: The reluctance type power generation mechanism (3) comprises a mover core (20), a stator core (21) and a winding (24); the cylinder body (1) also comprises a power generation chamber (25); a power generation chamber (25) is provided on a side of the premixing chamber (7) away from the combustion chamber (4); a piston rod (17) is partially located in the power generation chamber (25), and the other end passes through the wall of the power generation chamber (25); a plurality of mover cores (20) are provided on the side wall of the piston rod (17); a plurality of stator cores (21) are provided at positions of the wall of the power generation chamber (25) corresponding to the mover core (20); and a winding (24) is wound around the stator core (21).

7. The two-stroke free piston linear generator according to claim 6, characterized in that: A mover yoke (23) is provided between the piston rod (17) and the mover iron core (20); and a stator yoke (22) is provided between the stator iron core (21) and the wall of the power generation chamber (25).

8. The two-stroke free piston linear generator according to any one of claims 1 to 7, characterized in that: The invention also comprises a cooling mechanism (26); the cooling mechanism (26) comprises a packaging sleeve (27), a circulation pump (28), a radiator (29) and a circulation pipeline (30); the packaging sleeve (27) is arranged on the outer wall of the cylinder body (1), is filled with a coolant, and is provided with a temperature sensor (37); the packaging sleeve (27) is connected to the radiator (29) through a circulation pipeline (30); and the circulation pipeline (30) is provided with a circulation pump (28).

9. The two-stroke free piston linear generator according to claim 6 or 7, characterized in that: It also includes an electrical mechanism; the electrical mechanism includes an excitation power supply unit (31), a power conversion unit (32), a control unit (33) and a load unit (34); the power conversion unit (32) is electrically connected to the excitation power supply unit (31), the control unit (33), the load unit (34) and the winding (24) respectively.

10. A method for operating a two-stroke free piston linear generator as claimed in claim 9, characterized in that: The following steps are included: Step S1, first stroke, top dead center→bottom dead center, the spark plug ignites, the gas in the combustion chamber is ignited, the gas expansion pushes the left and right pistons to move from the top dead center to the bottom dead center, the second exhaust valve of the premixing chamber opens, and when the piston moves to the point where it just does not block the first exhaust valve of the combustion chamber, the first exhaust valve opens; When the piston moves to the point where the first intake valve just does not cover the combustion chamber, the first intake valve opens; the first exhaust valve and the first intake valve close after being kept open for a period of time, and the second exhaust valve closes at the same time, and the piston continues to move toward the bottom dead center to compress the gas in the premixing chamber until it reaches the bottom dead center; Step S2, second stroke, bottom dead center→top dead center. After the piston reaches the bottom dead center, it moves from the bottom dead center to the top dead center under the action of the compressed gas. When the air pressure in the premixing chamber is lower than the set value p1, the control unit controls the excitation power supply unit to energize the winding through the power conversion unit, and the booster piston continues to move to the top dead center until the air pressure value is lower than the set value p2. The second intake valve and the second exhaust valve are opened, and the fuel nozzle is opened at the same time. When the piston is about to reach the top dead center, the spark plug ignites, and the piston finally reaches the top dead center under the action of inertia, and then moves from the top dead center to the bottom dead center under the action of gas expansion, and repeats step S1.

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