A double-actuator air-floating free-piston Stirling generator with a cooling center column

Abstract

The present invention discloses a double-motor air-floating free piston Stirling generator with a cooling center column, which belongs to the field of thermal power technology. Compared with existing models, the Stirling generator has three structural innovations: first, a T-shaped center column is set in the inner cavity of the ejector, and the separation cavity formed by cooperating with the ejector configuration functions as two gas springs with superimposed stiffness, and the air-floating bearing is constructed by using the dynamic pressure phase; second, the air film surface of the power piston air-floating bearing and the functional holes of the high and low pressure air chambers are placed on the inner and outer walls of the power piston to suppress the parasitic flow on the air-floating bearing surface; third, a cooling center column is set, and the cooling medium in it can maintain the stability of the air gap size of the mover. The whole machine has no wearing parts, the ejector does not rely on lightweight precious metal materials, and can operate for a long time without maintenance at high temperatures. It provides a high-performance, cost-effective thermoelectric conversion device for a variety of scenarios including aerospace-grade nuclear power sources, unmanned underwater power compartments and other harsh environment applications.

Description

Technical Field

[0001] The invention relates to thermal power technology, and in particular to a double-motor air-floating free-piston Stirling generator with a cooling center column. Background Art

[0002] The Stirling device uses the Stirling cycle as its working principle and is a closed-cycle machine that works based on the temperature difference of the heat source. It is divided into two categories according to its use: the one that uses the forward Stirling cycle is called a Stirling engine. The working fluid in the device absorbs heat and expands at high temperatures and releases heat and compresses at room temperature. The expansion work obtained is greater than the compression work, thereby converting thermal energy into mechanical energy; the one that uses the reverse Stirling cycle is called a Stirling refrigerator. The device needs to consume mechanical energy to achieve the working fluid's heat release and compression at room temperature, and absorbs heat and expands at low temperatures to produce a refrigeration effect. It is divided into two categories according to the structure of the actuator transmission: the mechanical Stirling that relies on the transmission of the mechanism, the motion phase and amplitude of the actuator are determined by the mechanism; the other is the free piston Stirling, there is no rigid mechanism connecting the actuators, the moving parts follow the laws of dynamics, and reciprocate under the constraints of gas force, inertia force and restoring force; the amplitude and phase of the actuator can change with different working parameters. Modern free-piston Stirling machines integrate linear reciprocating motors to improve transmission efficiency, and achieve oil-free lubrication, wear-free operation, and even long life and high reliability through leaf spring support, air flotation or magnetic levitation. Vibration and noise levels are greatly reduced through opposition or additional vibration absorbers. They are superior to mechanical Stirling machines in many indicators.

[0003] The Stirling device has a wall-type heat exchange with the external heat source, so it is suitable for various types of heat sources such as gas, liquid, and solid fuels, medium and high temperature waste heat, solar thermal energy, and nuclear reactor heat. The working medium is usually helium, which is environmentally friendly. Generators have been used in underwater power, space power, solar dish power generation, mobile generators, combined heat and power, and other scenarios. Refrigerator is used in infrared, superconducting device cooling, biological, pharmaceutical refrigeration and cold chain and other fields.

[0004] At least two movers are required inside the free-piston Stirling machine to realize the volume change of the expansion chamber and the compression chamber, thereby achieving the heat-to-work conversion effect. The mover whose end is close to the compression chamber is called the power piston or compression piston, and the mover whose end is close to the expansion chamber is called the ejector or valve piston; the reciprocating motion of the two movers will drive the working fluid to shuttle back and forth between the expansion chamber and the compression chamber through the adjacent heat exchangers, regenerators, and cooler flow channels. The pressure of the working fluid will undergo periodic changes that are not synchronized with the movers in this process, thereby generating heat-to-work conversion. If the two movers work in their respective resonant states, a large amplitude can be obtained, a higher working chamber pressure amplitude can be achieved, and a stable working condition can be achieved under the constraints of internal damping and external loads.

[0005] In the design of free piston Stirling machines, in order to achieve oil-free lubrication and wear-free operation of the mover, it is necessary to clarify the way to achieve the radial support force and axial restoring force of the mover. In the typical products of the representative manufacturer Infinia, such as Fig.17 As shown, the displacer and the power piston are placed in two cylinders, one large and one small, and each is independently supported by a leaf spring. The function of the leaf spring is to provide radial support force for the mover while providing appropriate axial restoring force. The volume of the gas in the back pressure chamber and the inner cavity of the displacer changes periodically due to the oscillation of the mover, which is equivalent to a gas spring. In this model, there are two groups of leaf springs fixed to the center column inside the displacer, and the power piston is supported by another two groups of leaf springs. There is a gas spring with a static volume of V inside the displacer, and the gas in the back pressure chamber also has the function of a gas spring. The axial restoring force (also called stiffness) of the displacer is provided by the leaf spring and the gas spring V; the stiffness of the power piston includes not only the leaf spring, the equivalent gas spring of the back pressure chamber, but also the electromagnetic stiffness of the motor.

[0006] In the typical products of another representative manufacturer, Sunpower, USA, the displacer and the power piston run coaxially in the same caliber cylinder, and the thin rod at the bottom of the displacer passes through the power piston coaxially, and its end is fixed to the center of the leaf spring located in the back pressure chamber. The leaf spring provides radial support and axial stiffness for the displacer. The axial stiffness of the power piston is provided by the back pressure chamber gas spring and the electromagnetic stiffness of the motor, and its radial support force is provided by the static pressure air bearing based on the one-way valve arranged on the power piston. The company's patent US5525845 further discloses the scheme of the combined application of this type of air bearing and leaf spring.

[0007] Limited by the fatigue limit of elastic metal materials, models using leaf springs and one-way valve air bearings using elastic gas valves are not suitable for long-term operation in harsh, unmanned scenarios (such as aerospace, unmanned submarines, etc.). The US MTI patent US5140905 discloses a maintenance-free, long-life model with integrated gas springs, no elastic elements, and double-actuator air flotation realized by hole-slot structure, such as Fig.18 shown.

[0008] In this model, the ejector is composed of four components, which are surrounded by the surrounding structural parts to form an upper gas spring chamber and a lower gas spring chamber, and the side gas spring chamber is connected to the upper gas spring chamber through an air path. The upper gas spring refers to the gas spring chamber close to the hot zone, and the lower gas spring refers to the gas spring chamber close to the compression chamber. The upper and lower gas spring chambers jointly provide axial stiffness for the reciprocating oscillation of the ejector; there is a hydrostatic bearing air storage chamber inside the ejector assembly, and the lower gas spring chamber periodically and pulse-type pumps air to the air storage chamber, and forms an air flotation effect in the air gap through the jet holes circumferentially arranged on the wall of the assembly, providing radial support for the ejector. In terms of the power piston, this model uses a hole and groove structure arranged on the cylinder wall and the piston wall to achieve periodic and pulse-type pumping and pressure relief of the high and low pressure air chambers inside the piston. Specifically, Fig.19 , Fig. 20 As shown, when the fourth hole 138 intersects with the first hole 124, pulse pumping gas is applied to the high-pressure gas chamber 122, and the gas in the high-pressure gas chamber 122 is ejected from the second hole 128 arranged circumferentially on the piston wall surface, and then flows along the air gap to the adjacent annular groove 134, and then enters the low-pressure gas chamber 120 through the third hole 136 in the annular groove 134, and then the fifth hole 140 depressurizes the low-pressure gas chamber 120 when intersecting with the annular groove 134. Thus, an air flotation effect is formed in the air gap between the power piston and the cylinder, providing radial support force for the power piston; and the axial stiffness of the power piston is provided by the back pressure chamber gas spring and the electromagnetic stiffness of the motor.

[0009] Long-life, maintenance-free, high-power, and cost-effective models are the basis for the free piston Stirling device to expand its application scenarios and enhance its competitiveness with other technical solutions. In the existing model solutions, there are some constraints that limit the free piston Stirling to achieve high performance and high cost-effectiveness, and there is also room for innovation in the axial and radial support methods of the mover.

[0010] Fig.17 The model shown in the scheme does not require the displacement assembly and the power piston assembly to be strictly coaxial, which reduces the difficulty of manufacturing and assembly and is suitable for manufacturing large-bore, high-power machines. However, the limitations of this model that uses a large number of leaf springs are reflected in the following aspects: (1) Limited by the fatigue limit of the spring, it is limited to its use in applications requiring 10 9 (2) From a dynamic point of view, in the oscillation system, the equivalent mass of the leaf spring's own weight will be incorporated into the mass of the mover. The approach of increasing the number of leaf springs to increase the machine's operating frequency has limited engineering effect and it is difficult to obtain high-frequency, high-power density working conditions. The gas spring inside the ejector occupies a large space because the leaf spring assembly occupies a small proportion of the total stiffness.

[0011] Due to its working principle, the gas spring can only provide axial stiffness and cannot provide radial support for the mover alone. Even if a certain technical approach is adopted to provide radial support for the ejector, Fig.17 The ejector of the model shown does not use a leaf spring assembly, which makes it possible to significantly reduce the volume V of the internal gas spring chamber; however, due to the following two reasons, it will also limit the effective improvement of the gas spring stiffness: (1) In order to obtain performance indicators with commercial value, Fig.17 The ratio of the diameter of the center column D1 to the outer diameter of the ejector D2 should not be too large. The ratio of the area S1 corresponding to D1 to the volume V is proportional to the stiffness of the gas spring, so the improvement is limited; (2) The gas spring itself has relaxation loss. The larger the S1 / V, the greater the internal irreversible loss. In engineering, ΔV / V is generally less than 0.1. It is not possible to simply reduce the volume V to obtain a high-efficiency, high-stiffness gas spring.

[0012] Fig.18The main shortcomings of the model shown are in two aspects: (1) The axial dimension of the ejector structure is too long, which increases the overall length and volume of the machine and dramatically increases the cost. Fig.17 In this model, the bottom surface of the ejector is close to the bottom plane AA of the cooler, and Fig.18 The machine model realizes double gas springs and air bearings. The ejector component shown in the dotted box significantly crosses the bottom plane BB of the cooler, and the ejector parts that form the upper gas spring cavity with the structural parts are thick and heavy, resulting in the use of the same material. Fig.18 The mass of the solution ejector is significantly greater than Fig.17 Solution. MTI Company achieved the engineering indicators by using expensive rare lightweight metal pure beryllium to manufacture the ejector. In addition to pure beryllium, engineering materials that are resistant to high temperature and pressure, have good dimensional stability, and are extremely light in density are rare, which limits the application of this model outside aerospace scenarios. In addition, in order to ensure the air flotation effect, a large-volume side air spring needs to be installed, which further increases the size and weight of the machine. (2) The hole and groove structure of the power piston air flotation bearing has non-ideal parasitic working fluid migration. When the machine is working, the high-pressure air chamber 122 maintains a quasi-static level of pressure above the equalizing pressure and below the highest pressure of the back-pressure chamber 116, and the low-pressure air chamber 120 maintains a quasi-static level of pressure below the equalizing pressure and above the lowest pressure of the back-pressure chamber 116; however, the pressure of the back-pressure chamber fluctuates periodically between the highest pressure and the lowest pressure. During most of the period, the pressure in the back-pressure chamber 116 is higher than that in the low-pressure air chamber 120, causing the back-pressure chamber working fluid to flow back into the low-pressure air chamber 120 through the fifth hole 140 and the third hole 136 in the annular groove 134, causing its pressure to rise and reducing the air film carrying capacity. Moreover, the presence of the fourth hole 138 will also introduce disturbances to the air film caused by the back-pressure chamber 116, affecting the mainstream direction and stability of the air film.

[0013] As mentioned before, the realization of radial support and axial stiffness of the two movers, the displacer and the power piston, is the core of the free piston model design, which will essentially determine the life, performance and cost of the machine. The starting point of this invention is to provide a new solution for the axial stiffness and radial support of the mover through structural innovation and avoid the drawbacks of the existing solution.

[0014] From a dynamics perspective, gas springs do not generate additional mass on the mover, and are the preferred way to build a high-rigidity structure and ensure high-frequency operation. The high-rigidity gas spring structure should be as compact as possible to reduce the length of the ejector, thereby reducing the manufacturing cost of the ejector. The self-pumping air bearing built in the machine provides radial support for the mover, which is also the preferred way to achieve no wear, long life, and high reliability. The configuration of air bearings needs to consider four factors: (1) There needs to be a narrow air gap. The width of the air gap should generally be less than 0.02 mm. The gas ejected from the small hole forms an air film in this narrow air gap and produces an air flotation effect on the mover. The supporting force of the air film and the air consumption of the air flotation are very sensitive to the change of the air gap width. If there are structural measures to ensure the stability of the air gap width and suppress the temperature effect from cold to hot, it will be very beneficial. (2) The construction of the air chamber. One way is to achieve high and low pressure air chambers with quasi-static pressure by designing the hole and slot structure. If certain functional cavities inside the machine (such as compression chambers, air spring chambers, etc.) can be reused through structural innovation, the structural complexity of the air bearing will be significantly reduced, and the mover will be lighter. (3) Reasonable arrangement of the structure and air path to suppress the parasitic flow that occurs when the air bearing is working as much as possible. (4) The periodic stability and reliability of the air bearing, which is reflected in the need to have measures to suppress the circumferential pulsation associated with the axial oscillation of the mover and prevent the directional migration of the working fluid between the cavities.

[0015] Based on the above considerations, the present invention achieves in principle (1) a compact high-rigidity ejector gas spring through three aspects of structural innovation; (2) suppressing parasitic flow on the bearing surface of the mover air bearing; and (3) maintaining the stability of the air gap size of the ejector and power piston. This model has no movement wear, no elastic parts prone to fatigue failure, and the ejector does not rely on lightweight precious metal materials. It can operate stably and maintenance-free at high temperatures all year round; it provides high-performance, cost-effective thermoelectric conversion device solutions for multiple application scenarios. Summary of the invention

[0016] First, the present invention creatively proposes a new configuration inside the ejector, such as Fig.21 As shown, the ejector assembly is typically composed of three bodies, upper, middle and lower, including inner and outer coaxial cylinders and a cylinder No. 1 fixed to the inner wall of the outer cylinder through a partition, wherein the cylinder No. 1 is newly added, and the newly added structural member matched with the cylinder No. 1 is called a T-shaped center column. In this scheme, in order to simplify the position relationship and the movement air gap relationship between the ejector and other components, the outer cylinder of the ejector is referred to as the outer wall of the ejector, and the inner cylinder of the ejector is referred to as the inner wall of the ejector. C1 represents the movement air gap between the No. 1 cylinder and the T-shaped center column, C2 represents the movement air gap between the inner wall of the ejector and the cooling center column or the upper cylinder sleeve, and C3 represents the movement air gap between the outer wall of the ejector and the main cylinder sleeve.

[0017] like Fig. 22As shown, inside the new configuration ejector, the T-shaped center column and the associated structural parts divide the internal volume into two cavities. The volumes of the two cavities are filled with different types of dots, which are indicated as V1 and V2. Because the T-shaped center column is a static structural part, when the ejector reciprocates, the two cavities V1 and V2 are equivalent to two gas springs, respectively called gas spring chamber 1 and gas spring chamber 2. The outer diameter of the T-shaped center column is D3, the outer wall diameter of the ejector is D2, and the inner wall aperture of the ejector is D1. The corresponding motion air gaps are Fig.21 The stiffness of C1, C3, C2, and V1 is proportional to The stiffness of V2 is proportional to Because the pressure phases are opposite, the stiffness is superimposed; when this configuration is applied, the outer diameter D3 of the T-shaped center column can be significantly larger than D1, and is not constrained by the ratio between D1 and D2, so there are loose parameter conditions to obtain high stiffness; in addition, the ejector structure is compact, and the entire ejector does not pass through the bottom plane CC of the cooler. This high rigidity and compact configuration allows the ejector made of conventional materials to operate in high-frequency conditions without relying on rare lightweight materials.

[0018] How can the new configuration of the ejector achieve radial support? The ejector should be as light as possible. If a separate air chamber is opened, the weight of the mover will inevitably increase, and the complexity of the structure will also increase. From the above analysis of the elements of the air bearing, it can be seen that the three narrow and long moving air gaps C1, C2, and C3 in the new configuration provide the basic conditions for constructing the air bearing. The present invention realizes the reuse of functional cavities through structural innovation by analyzing the pressure phase of the internal cavity of the machine.

[0019] Specifically:

[0020] (1) Fig.23 The displacement of the free piston Stirling thermal motor and the pressure vector diagram of the compression chamber under typical working conditions. d is the displacement vector of the ejector, X p is the displacement vector of the power piston, P c is the compression chamber pressure vector. In the new configuration, the pressure vector P2 in the gas spring chamber V2 is proportional to the displacement vector X d have the same phase.

[0021] (2) Fig.24The characteristic points of the amplitude changes of Pc and P2 within a cycle under typical working conditions are illustrated. It can be seen that during the period ab, the gas spring chamber 2 can relieve pressure to the compression chamber; during the adjacent period bc, the compression chamber can relieve pressure to the gas spring chamber 2, and so on. This feature is combined with the new configuration, and it is conceived to directly achieve the pressure relief of the gas spring chamber 2 to the compression chamber through the throttling injection of small holes arranged circumferentially on the circumferential surface of the inner wall of the ejector, and form an air-floating air film in the moving air gap C2 in the ab period to form radial support for the ejector; and the pressure relief of the compression chamber to the gas spring chamber 2 in the bc period requires the construction of a pressure-inducing flow channel, a throttling small hole, and a converging slot hole structure on the circumference of the outer wall of the ejector, forming an air-floating air film in the moving air gap C3 to form radial support for the ejector.

[0022] (3) Fig.25 The pressure amplitude changes of gas spring chamber 1 and gas spring chamber 2 in the cycle are shown. Based on the structural characteristics of the new configuration, the phase difference between P1 and P2 is 180 degrees. By setting small injection holes connecting gas spring chamber 1 and gas spring chamber 2 respectively on the circumference of the T-shaped center column or the first cylinder of the ejector, an air-floating air film with alternating flow direction in half a cycle can be formed in the moving air gap C1, forming radial support for the ejector.

[0023] (4) By adopting the above two structures, the three narrow and long moving air gaps C1, C2, and C3 can form an alternating and partially superimposed air flotation effect, thereby avoiding the poor air flotation effect of the air flotation bearing when the pressure difference between the associated cavities is small. Fig.24 The air flotation effect in C2 and C3 near the characteristic moments a, b, and c is very weak, while the air flotation effect in C1 is very strong at this time; thus ensuring that the new configuration ejector can obtain sufficient radial support force at any time in the cycle. Moreover, the above-mentioned air flotation effect is achieved by reusing the existing gas spring cavity of the new configuration machine, without the need to construct an additional air storage chamber. When the air bearing is working, only a trace amount of gas is required, which will not have a significant impact on the large volume functional cavity.

[0024] On the second aspect, since the air-floating bearing is very sensitive to the change of the air gap width, which is theoretically a cubic relationship, an air gap width that is too wide or too narrow will lead to air flotation failure. Under the existing technical scheme, with the thermal diffusion effect of the hot end of the machine being heated, the air gaps in various places inside the machine will change to varying degrees. If the dimensional changes of as many air gap positions as possible with temperature can be suppressed, the operating reliability and air flotation stability of the model will be improved. The present invention creatively proposes a cooling center column structure, in which the cooling medium flowing inside can maintain the temperature of the cooling center column and the air gap of the T-shaped center column at a level slightly higher than the temperature of the cooling medium. The collaborative cooler can maintain the temperature of the three moving air gaps C1, C2, and C3 of the new configuration ejector at a level slightly higher than the temperature of the cooling medium, and the moving air gap on the inner side of the power piston adapted to the cooling center column is also at a level slightly higher than the temperature of the cooling medium, which can avoid the jamming of the mover or air flotation failure when running for a long time at high temperature. The specific structure is illustrated in the figure below.

[0025] Furthermore, in terms of radial support measures for the power piston, in view of the drawback of parasitic flow in the patented solution of the MTI power piston static pressure air floating bearing, the present invention configures the outer cylindrical wall surface of the mover piston as an air floating bearing surface, and only provides jet holes and confluence groove holes, so that the air film functional area in the moving air gap between the power piston and the cylinder always maintains a fixed flow direction without parasitic disturbance; and on the inner cylindrical surface of the power piston, air inlet holes and air vents are arranged at large intervals, and in the significantly elongated narrow air gap, the cross-flow between chambers is greatly suppressed. The specific structure is illustrated in the following figure.

[0026] In addition, when the free piston Stirling device is in operation, there may be a problem that the half-cycle asymmetry of the leakage along the moving air gap may induce the drift of the center of the mover. The commonly used method known in the industry is the "midpoint venting method", that is, setting an airway to allow the associated chamber to experience a short and sufficient pressure equalization in the area of ​​the center point of the mover oscillation. In the new configuration ejector, it is preferred to set a pressure equalization hole on the T-shaped middle column and the No. 1 cylinder of the ejector. The specific structure is described in the following figure.

[0027] Finally, in models without leaf spring constraints, technical measures are needed to stabilize the circumferential angle of the mover to prevent failure when the holes on the mover intersect with the holes on the stationary structural parts. For example, pressure equalization, pumping, and pressure relief processes all involve the intersection between the holes on the mover and the holes on the structural parts. By utilizing the inherent characteristics of the magnetic poles of magnets that like polarities repel each other and opposite polarities attract each other, constructing magnetic suspension components at appropriate positions on the mover and structural parts can prevent obvious angle pulsations in the circumferential position. Typical magnetic suspension structures are as follows: Fig.26As shown, on two parts that need to keep the relative angle fixed, magnets of opposite polarity are arranged in pairs along the circumferential direction. In the new configuration machine, the circumferential position of both movers needs to be constrained during axial movement. It is preferred to set the magnetic suspension assembly in a suitable area where the installation space is allowed and the temperature is relatively low. To ensure the constraint effect, the length of the magnet along the axial direction of the mover should be greater than the amplitude of the mover. The specific structure is described in the following figure.

[0028] A double-acting air-floating free-piston Stirling generator with a cooling center column, comprising an outer shell, a heat head, a hot end heat exchanger, a regenerator, a cooler, an ejector, a power piston, a main cylinder sleeve, a T-shaped center column, a cooling center column, a spacer column and a linear motor assembly, wherein the outer shell, the heat head and the cooling center column form a closed cavity, the ejector is arranged inside the heat head, and an expansion cavity is formed between the heat head and the hot end heat exchanger, the hot end heat exchanger, the regenerator and the cooler are arranged in an annular flow channel between the heat head and the ejector in sequence, and the main The cylinder sleeve is arranged in the outer shell and is fixedly connected to the outer shell. There is a moving air gap between the outer wall of the displacer and the inner wall of the main cylinder sleeve, and there is a moving air gap between the inner wall and the cooling center column or the main cylinder sleeve. The power piston is arranged between the main cylinder sleeve and the cooling center column. There is a moving air gap between the outer wall of the power piston and the inner wall of the main cylinder sleeve, and there is a moving air gap between the inner wall and the cooling center column. The power piston, the displacer, the cooling center column and the main cylinder sleeve form a compression chamber. The main cylinder sleeve is evenly provided with a flow passage for connecting the compression chamber and the cooler along the circumferential direction. The partition column is arranged at the bottom of the cooling center column, and a gas chamber is formed between the partition column and the cooling center column. The power piston, the outer shell and the cooling center column form a back pressure chamber. The lower part of the cooling center column is evenly provided with vent holes for connecting the back pressure chamber and the gas chamber along the circumferential direction. The gas chamber is a component of the back pressure chamber volume; the T-shaped center column is arranged inside the ejector and is fixedly connected to the cooling center column or the top of the main cylinder sleeve. The ejector includes a No. 1 cylinder, which is fixed to the middle part of the ejector through a partition. There is a moving air gap between the inner wall of the cylinder and the outer wall of the T-shaped center column. The gas spring chamber inside the ejector is divided into gas spring chamber one and gas spring chamber two by the T-shaped center column and the cooling center column or the T-shaped center column and the main cylinder sleeve. The cavity formed by the interior of the partition column, the interior of the cooling center column and the bottom of the T-shaped center column or the interior of the partition column, the interior of the cooling center column, the bottom of the T-shaped center column and the upper part of the main cylinder sleeve is used to circulate cooling medium; the linear motor assembly is arranged between the outer shell and the main cylinder sleeve, and the annular magnet in the linear motor assembly is fixedly connected to the bottom of the power piston through a magnet base.

[0029] As a preferred embodiment of the above technical solution, there is a moving air gap between the inner wall of the ejector and the cooling center column, and the gas spring cavity inside the ejector is divided into gas spring cavity one and gas spring cavity two by the T-shaped center column and the cooling center column. The cavity surrounded by the interior of the partition column, the interior of the cooling center column and the bottom of the T-shaped center column is used to circulate the cooling medium; the bottom of the ejector is evenly provided with air guide holes connected to the compression cavity along the circumference, the outer wall of the ejector is evenly provided with jet holes connected to the air guide holes along the circumference, and the outer wall of the ejector is also provided with an annular confluence groove one, and the annular confluence groove one is evenly provided with gas flow holes connected to the compression cavity. An air inlet hole one connected to the gas spring chamber two is evenly provided, and jet holes two are evenly provided on the inner wall of the ejector along the circumferential direction. When the pressure of the compression chamber is greater than the pressure of the gas spring chamber two, the jet hole one throttles and sprays, forming an air flotation effect in the moving air gap between the ejector and the main cylinder sleeve; when the pressure of the gas spring chamber two is greater than the pressure of the compression chamber, the jet hole two throttles and sprays, forming an air flotation effect in the moving air gap between the ejector and the cooling center column. The air flotation effect provides radial support for the reciprocating motion of the ejector, and the outer diameter of the T-shaped center column is greater than the outer diameter of the cooling center column.

[0030] As a preferred embodiment of the above technical solution, the main cylinder sleeve includes an upper cylinder sleeve and a lower cylinder sleeve, and the upper cylinder sleeve and the lower cylinder sleeve are fixedly connected to the outer shell, the upper cylinder sleeve includes an inner cylinder and an outer cylinder connected by a bottom plate, there is a moving air gap between the inner wall of the discharger and the outer wall of the inner cylinder, there is a moving air gap between the outer wall of the discharger and the inner wall of the outer cylinder, the gas spring chamber inside the discharger is divided into gas spring chamber one and gas spring chamber two by the T-shaped middle column and the upper cylinder sleeve, the bottom of the upper cylinder sleeve is fixedly sealed and connected to the top of the cooling middle column, the cavity surrounded by the interior of the partition column, the interior of the cooling middle column, the bottom of the T-shaped middle column and the upper cylinder sleeve is used to circulate cooling medium, there is a moving air gap between the inner wall of the lower cylinder sleeve and the outer wall of the power piston, and a vent hole three is provided on the bottom plate of the upper cylinder sleeve for connecting the compression chamber separated by the bottom plate, the vent hole one It is arranged at the bottom of the outer cylinder; the bottom of the ejector is evenly provided with air guide holes connected to the compression chamber along the circumference, the outer wall of the ejector is evenly provided with jet holes connected to the air guide holes along the circumferential direction, the outer wall of the ejector is also provided with an annular confluence groove, and the annular confluence groove is evenly provided with an air inlet hole connected to the gas spring chamber 2, and the inner wall of the ejector is evenly provided with jet holes along the circumferential direction. When the pressure of the compression chamber is greater than the pressure of the gas spring chamber 2, the jet hole 1 throttles the jet to form an air flotation effect in the moving air gap between the ejector and the outer wall of the outer cylinder; when the pressure of the gas spring chamber 2 is greater than the pressure of the compression chamber, the jet hole 2 throttles the jet to form an air flotation effect in the moving air gap between the ejector and the outer wall of the inner cylinder, and the air flotation effect provides radial support for the reciprocating motion of the ejector; the outer diameter of the T-shaped center column is greater than the outer diameter of the inner cylinder.

[0031] As a preferred embodiment of the above technical solution, the upper cylinder sleeve and the lower cylinder sleeve can be cylinder sleeves with different diameters.

[0032] As a preferred embodiment of the above technical solution, the width of the moving air gap formed between the inner wall of the No. 1 cylinder and the outer wall of the T-shaped middle column is less than 0.02 mm, and the length of the moving air gap is greater than 4 times the single-sided stroke of the ejector.

[0033] As a preferred embodiment of the above technical solution, the outer wall of the T-shaped center column or the inner wall of the No. 1 cylinder is evenly provided with jet holes along the circumferential direction, the jet hole connected to the gas spring chamber one is the jet hole three, and the jet hole connected to the gas spring chamber two is the jet hole four. When the pressure of the gas spring chamber one is greater than the pressure of the gas spring chamber two, the jet hole three throttles the jet to form an air flotation effect in the moving air gap between the inner wall of the No. 1 cylinder and the outer wall of the T-shaped center column; when the pressure of the gas spring chamber two is greater than the pressure of the gas spring chamber one, the jet hole four throttles the jet to form an air flotation effect in the moving air gap between the inner wall of the No. 1 cylinder and the outer wall of the T-shaped center column. The air flotation effect provides radial support for the reciprocating motion of the ejector.

[0034] As a preferred embodiment of the above technical solution, the distance between the jet hole three and the jet hole four is greater than twice the single-side stroke of the ejector.

[0035] As a preferred embodiment of the above technical solution, the power piston contains a high-pressure air chamber and a gas-pressure air chamber, and the outer wall of the power piston is evenly provided with jet holes five connected with its high-pressure air chamber along the circumferential direction, and the outer wall of the power piston is also provided with an annular confluence groove two, and the annular confluence groove two is evenly provided with air inlet holes two connected with the low-pressure air chamber of the power piston, and the side wall of the cooling middle column and the partition column that form the gas chamber is evenly provided with upper pump holes and lower pressure relief holes along the circumferential direction, and the inner wall of the power piston is also evenly provided with air inlet holes three and air vent holes four along the circumferential direction, and the air inlet hole three cooperates with the upper pump hole to connect the high-pressure air chamber and the back-pressure chamber, and the air vent hole four cooperates with the lower pressure relief hole to connect the low-pressure air chamber and the back-pressure chamber, and when the jet hole five is throttled for jetting, an air flotation effect is formed in the moving air gap between the outer wall of the power piston and the inner wall of the main cylinder sleeve, providing radial support for the reciprocating motion of the power piston.

[0036] As a preferred embodiment of the above technical solution, the distance between the upper pump air hole and the air inlet hole three is smaller than the unilateral stroke of the power piston, the distance between the lower pressure relief hole and the vent hole four is smaller than the unilateral stroke of the power piston, the air inlet hole three is closer to the T-shaped center column than the upper pump air hole, and the lower pressure relief hole is closer to the T-shaped center column than the vent hole four.

[0037] As a preferred embodiment of the above technical solution, the T-shaped center column and the No. 1 cylinder are provided with a pressure equalizing hole 1 for instantaneously connecting the gas spring chamber 1 and the gas spring chamber 2.

[0038] As a preferred embodiment of the above technical solution, the power piston and the main cylinder sleeve are provided with a second pressure equalizing hole for instantaneously connecting the compression chamber and the back pressure chamber.

[0039] As a preferred embodiment of the above technical solution, a magnetic suspension base is fixed to the inner bottom of the outer shell, and No. 1 magnets that cooperate with each other are evenly fixed on the magnetic steel base and the magnetic suspension base along the circumferential direction.

[0040] As a preferred embodiment of the above technical solution, No. 2 magnets that cooperate with each other are evenly fixed on the T-shaped center column and the inner wall of the ejector along the circumferential direction.

[0041] The beneficial effects of the present invention are:

[0042] 1. A T-shaped center column is set to separate the gas spring chamber in the ejector into gas spring chamber 1 and gas spring chamber 2. The diameter of the T-shaped center column is designed to have a wide range of values, which can loosely achieve low loss and high rigidity. Compared with the existing solution, it can greatly reduce the weight of the ejector, does not rely on rare lightweight materials, and greatly saves production and processing costs.

[0043] 2. The air bearing solution of the ejector realizes the reuse of functional cavities, so that there is no need to open up additional chambers. The ejector has a simple and light structure and is easier to achieve high-frequency and large-amplitude working conditions.

[0044] 3. A cooling center column is set to effectively cool down the dynamic sealing area of ​​the ejector, power piston and upper cylinder sleeve, inhibit the temperature effect of high-temperature heat diffusion on the size of the moving air gap, and prevent the amplitude attenuation of the mover, air flotation failure, and even the mover from getting stuck when the machine works for a long time.

[0045] 4. The air film surface of the mover piston air bearing and the air chamber inlet and outlet holes are placed on the inner and outer cylindrical surfaces, which ensures the stability of the gas flow in the air film and suppresses parasitic flow.

[0046] 5. In the model scheme where the main cylinder liner is decomposed into an upper cylinder liner and a lower cylinder liner, the overall machine diameter will be reduced because the lower cylinder liner has a smaller diameter than the upper cylinder liner, which is suitable for application scenarios that are sensitive to the diameter; and the cooling center column is shortened, and the upper cylinder liner and the lower cylinder liner do not need to be strictly coaxial, which reduces manufacturing costs and assembly difficulty.

[0047] 6. The machine is equipped with a comprehensive pressure-equalizing and magnetic suspension structure to prevent the center drift and circumferential pulsation of the mover, which structurally guarantees the operational reliability of the gas spring and air bearing.

[0048] The above beneficial effects enable the machine model of the present invention to adapt to the requirements of maintenance-free operation in harsh environments all year round and the manufacturing cost has a significant advantage over existing models. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 It is a cross-sectional view of embodiment 1.

[0050] Figure 2 It is a partial structural schematic diagram of the outer wall of the ejector and the main cylinder sleeve when the air flotation effect is formed in the first embodiment.

[0051] Figure 3 It is a partial structural schematic diagram of the inner wall of the ejector and the cooling middle column when the flotation effect is formed in Example 1.

[0052] Figure 4 It is a structural schematic diagram of the pressure equalizing hole when it is in action.

[0053] Figure 5 It is a partial structural schematic diagram of the power piston in the first embodiment when it moves away from the back pressure chamber and the low pressure air chamber of the power piston releases pressure to the back pressure chamber through the vent hole.

[0054] Figure 6 It is a partial structural diagram of the power piston in Example 1 when it moves toward the back pressure chamber and the back pressure chamber inflates the high pressure air chamber of the power piston through the pump air hole.

[0055] Figure 7 It is a schematic diagram of the structure when the pressure equalizing hole 2 is in action.

[0056] Figure 8 and Fig. 9 This is a schematic diagram of the T-shaped center column structure.

[0057] Fig.10 , Fig.11 This is a schematic diagram of the power piston structure.

[0058] Fig.12 Schematic diagram of the cooling center column structure.

[0059] Fig.13 This is a cross-sectional view of the power piston magnetic suspension.

[0060] Fig.14 This is a cross-sectional view of Example 2.

[0061] Fig.15 It is a partial structural schematic diagram of the ejector No. 1 cylinder and the T-shaped middle column when the air flotation effect is formed in the second embodiment.

[0062] Fig.16 This is a cross-sectional view of the upper cylinder liner.

[0063] Fig.17 , Fig.18 , Fig.19 , Fig. 20 It is a prior art view in the background technology.

[0064] Fig.21 This is a cross-sectional view of the ejector.

[0065] Fig. 22 This is the specific division principle diagram of the ejector gas spring chamber.

[0066] Fig.23 Vector diagram of the free piston Stirling thermal motor displacement and compression chamber pressure.

[0067] Fig.24 This is a graph showing the amplitude changes of Pc and P2 within a cycle under typical working conditions.

[0068] Fig.25 It is a diagram of the pressure amplitude change of gas spring chamber 1 and gas spring chamber 2 during the cycle.

[0069] Fig.26 Schematic diagram of a typical magnetic suspension structure.

[0070] The accompanying drawings are marked as follows: 1-outer shell, 2-heat head, 3-hot end heat exchanger, 4-regenerator, 5-cooler, 6-discharger, 601-cylinder No. 1, 7-power piston, 8-main cylinder sleeve, 801-upper cylinder sleeve, 801a-inner cylinder, 801b-outer cylinder, 802-lower cylinder sleeve, 9-T-shaped middle column, 10-cooling middle column, 11-partition column, 12-linear motor assembly, 13-expansion chamber, 14-compression chamber, 15-vent one, 16-gas chamber, 17-back pressure chamber, 18-vent two, 19-partition plate, 20-gas spring chamber, 2001-gas spring chamber one, 2002-gas spring chamber two, 21-magnetic steel base, 22-air guide hole, 23-jet hole one, 24-annular confluence groove one, 2 5-inlet hole one, 26-jet hole two, 27-bottom plate, 28-vent hole three, 29-jet hole three, 30-jet hole four, 31-high pressure air chamber, 32-jet hole five, 33-annular confluence groove two, 34-low pressure air chamber, 35-inlet hole two, 36-upper pump air hole, 37-lower pressure relief hole, 38-inlet hole three, 39-vent hole four, 40-equalizing hole one, 41-equalizing hole two, 42-magnetic suspension base, 43-magnet No. 1, 44-magnet No. 2, 45-jet hole six, 116-back pressure cavity one, 120-low pressure air chamber one, 122-high pressure air chamber one, 124 No. 1 hole, 128-No. 2 hole, 134-annular groove, 136-No. 3 hole, 138-No. 4 hole, 140-No. 5 hole. DETAILED DESCRIPTION

[0071] The technical solution of the present invention is described clearly and completely below in conjunction with the accompanying drawings of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present invention.

[0072] Embodiment 1

[0073] like Figures 1 to 13The double-acting air-floating free-piston Stirling generator with a cooling center column shown in the figure comprises an outer shell 1, a heat head 2, a hot end heat exchanger 3, a regenerator 4, a cooler 5, an ejector 6, a power piston 7, a main cylinder sleeve 8, a T-shaped center column 9, a cooling center column 10, a spacer column 11 and a linear motor assembly 12. The outer shell 1, the heat head 2 and the cooling center column 10 form a closed cavity. The ejector 6 is arranged inside the heat head 2 to form an expansion cavity 13 between the heat head 2 and the hot end heat exchanger 3. The hot end heat exchanger 3, the regenerator 4 and the cooler 5 are arranged in sequence between the heat head 2 and the ejector 6. In the annular flow channel between, the main cylinder sleeve 8 is arranged in the outer shell 1 and is fixedly connected to the outer shell 1. There is a moving air gap between the outer wall of the discharger 6 and the main cylinder sleeve 8, and there is a moving air gap between the inner wall and the cooling middle column 10. The power piston 7 is arranged between the main cylinder sleeve 8 and the cooling middle column 10. There is a moving air gap between the outer wall of the power piston 7 and the inner wall of the main cylinder sleeve 8, and there is a moving air gap between the inner wall and the cooling middle column 10. The power piston 7 and the discharger 6, the cooling middle column 10 and the main cylinder sleeve 8 form a compression chamber 14. The main cylinder sleeve 8 is evenly provided with a compression chamber 14 for connecting the compression chamber 14 along the circumferential direction. The cavity 14 and the vent hole 15 of the cooler 5 flow channel, the partition column 11 is arranged at the bottom of the cooling middle column 10, and a gas chamber 16 is formed between the partition column 11 and the cooling middle column 10. The power piston 7, the outer shell 1 and the cooling middle column 10 surround the back pressure cavity 17. The lower part of the cooling middle column 10 is evenly provided with vent holes 18 for connecting the back pressure cavity 17 and the gas cavity 16 along the circumferential direction. The gas cavity 16 is a component of the volume of the back pressure cavity 17; the T-shaped middle column 9 is arranged inside the ejector 6 and is fixedly connected to the top of the cooling middle column 10. The ejector 6 includes a cylinder 601 The No. 1 cylinder 601 is fixed to the middle part of the ejector 6 through the partition 19. There is a moving air gap between the inner wall of the No. 1 cylinder 601 and the outer wall of the T-shaped middle column 9. The gas spring chamber 20 inside the ejector 6 is divided into gas spring chamber 1 2001 and gas spring chamber 2 2002 by the T-shaped middle column 9 and the cooling middle column 10. The cavity surrounded by the inside of the partition column 11, the inside of the cooling middle column 10 and the bottom of the T-shaped middle column 9 is used for circulating cooling medium; the linear motor assembly 12 is arranged between the outer shell 1 and the main cylinder sleeve 8, and the annular magnet in the linear motor assembly 12 is fixedly connected to the bottom of the power piston 7 through the magnet base 21.

[0074] In this embodiment, the bottom of the ejector 6 is evenly provided with air guide holes 22 connected to the compression chamber 14 along the circumference, the outer wall of the ejector 6 is evenly provided with jet holes 23 connected to the air guide holes 22 along the circumferential direction, the outer wall of the ejector 6 is also provided with an annular confluence groove 24, and the annular confluence groove 24 is evenly provided with an air inlet hole 25 connected to the gas spring chamber 2002, and the inner wall of the ejector 6 is evenly provided with jet holes 26 along the circumferential direction. When the pressure of the compression chamber 14 is greater than the pressure of the gas spring chamber 2002, the jet hole 23 throttles the jet to form an air flotation effect in the moving air gap between the ejector 6 and the main cylinder sleeve 8; when the pressure of the gas spring chamber 2002 is greater than the pressure of the compression chamber 14, the jet hole 26 throttles the jet to form an air flotation effect in the moving air gap between the ejector 6 and the cooling center column 10. The air flotation effect provides radial support for the reciprocating motion of the ejector 6, and the outer diameter of the T-shaped center column 9 is greater than the outer diameter of the cooling center column 10.

[0075] In this embodiment, the air gap width of the moving air gap formed between the inner wall of the No. 1 cylinder 601 and the outer wall of the T-shaped middle column 9 is less than 0.02 mm, and the length of the moving air gap is greater than 4 times the single-sided stroke of the ejector 6.

[0076] In this embodiment, the outer wall of the T-shaped center column 9 or the inner wall of the No. 1 cylinder 601 is evenly provided with jet holes along the circumferential direction, the jet hole connected to the gas spring chamber 1 2001 is the jet hole 3 29, and the jet hole connected to the gas spring chamber 2 2002 is the jet hole 4 30. When the pressure of the gas spring chamber 1 2001 is greater than the pressure of the gas spring chamber 2 2002, the jet hole 3 29 throttles the jet to form an air flotation effect in the moving air gap between the inner wall of the No. 1 cylinder 601 and the outer wall of the T-shaped center column 9; when the pressure of the gas spring chamber 2 2002 is greater than the pressure of the gas spring chamber 1 2001, the jet hole 4 30 throttles the jet to form an air flotation effect in the moving air gap between the inner wall of the No. 1 cylinder 601 and the outer wall of the T-shaped center column 9, and the air flotation effect provides radial support for the reciprocating motion of the ejector 6.

[0077] In this embodiment, the distance between the jet hole 3 29 and the jet hole 4 30 is greater than twice the single-side stroke of the ejector 6 .

[0078] In this embodiment, the outer wall of the power piston 7 is evenly provided with jet holes 5 32 connected with its high-pressure air chamber 31 along the circumferential direction, and the outer wall of the power piston 7 is also provided with an annular confluence groove 2 33. The annular confluence groove 2 33 is evenly provided with air inlet holes 2 35 connected with the low-pressure air chamber 34 of the power piston 7. The side wall of the cooling middle column 10 that forms the gas chamber 16 with the partition column 11 is evenly provided with upper pump air holes 36 and lower pressure relief holes 37 along the circumferential direction. The inner wall of the power piston 7 is also evenly provided with air inlet holes 38 and air vent holes 4 39 along the circumferential direction. The air inlet holes 38 cooperate with the upper pump air holes 36 to connect the high-pressure air chamber 31 and the back pressure chamber 17, and the air vent holes 4 39 cooperate with the lower pressure relief holes 37 to connect the low-pressure air chamber 34 and the back pressure chamber 17. When the jet hole 5 32 is throttled for jetting, an air flotation effect is formed in the moving air gap between the outer wall of the power piston 7 and the inner wall of the main cylinder sleeve 8, providing radial support for the reciprocating motion of the power piston 7. In order to further enhance the air flotation effect, a jet head 45 connected to the high-pressure air chamber 31 can be arranged on the inner wall of the power piston 7.

[0079] In this embodiment, the distance between the upper pump air hole 36 and the air inlet hole three 38 is smaller than the single-sided stroke of the power piston 7, the distance between the lower pressure relief hole 37 and the air vent hole four 39 is smaller than the single-sided stroke of the power piston 7, the air inlet hole three 38 is closer to the T-shaped center column 9 than the upper pump air hole 36, and the lower pressure relief hole 37 is closer to the T-shaped center column 9 than the air vent hole four 39.

[0080] In this embodiment, a pressure equalizing hole 40 for instantaneously connecting the gas spring chamber 1 2001 and the gas spring chamber 2 2002 is provided on the T-shaped center column 9 and the first cylinder 601 .

[0081] In this embodiment, the power piston 7 and the main cylinder sleeve 8 are provided with a second pressure equalizing hole 41 for instantaneously connecting the compression chamber 14 and the back pressure chamber 17 .

[0082] In this embodiment, a magnetic suspension base 42 is fixed to the inner bottom of the outer shell 1, and No. 1 magnets 43 that cooperate with each other are evenly fixed on the magnetic steel base 21 and the magnetic suspension base 42 along the circumferential direction.

[0083] In this embodiment, the T-shaped center column 9 and the inner wall of the ejector 6 are evenly fixed with No. 2 magnets 44 along the circumferential direction for use in conjunction with each other.

[0084] The working principle of this Stirling generator follows the Stirling cycle heat-work conversion process. The relative movement of the displacer 6 and the power piston 7 causes the expansion chamber 13, the compression chamber 14, and the back pressure chamber 17 to change periodically, so that the PV work generated by the expansion chamber 13 is greater than the PV work consumed by the compression chamber, so that electrical energy can be output through the linear reciprocating motor. The linear reciprocating motor adopts the existing technology and is not described in detail here. The main innovation of the present invention is that the new structure is used to achieve radial support and axial stiffness for the two movers of the displacer 6 and the power piston 7. Under the control of fluid laws, under the action of the internal and external pressure difference, the gas in the closed cavity with a moving surface will produce pressure on the moving surface opposite to the direction of movement, similar to the stiffness characteristics of the spring, which is the gas spring effect. The air film in the narrow air gap with the injection source has the characteristic of resisting external force to reduce the width of the air gap within a certain load range, showing radial stiffness, that is, the static pressure flotation effect.

[0085] A high-rigidity ejector gas spring is realized through the T-shaped center column and the No. 1 cylinder 601, and when the ejector 6 and the power piston 7 move, a highly reliable air flotation effect is formed between the ejector 6 and the main cylinder sleeve 8 and the cooling center column 10, or between the ejector 6 and the T-shaped center column 9, the power piston 7 and the main cylinder sleeve 8, thereby achieving zero friction and greatly extending the service life of the entire machine.

[0086] The principle of radial support achieved by the ejector 6 is as follows: within the cycle, the pressure change in the lower air spring chamber 2002 is ahead of the pressure change in the compression chamber 14. When in the cycle time period ab, the working medium is sprayed into the moving air gap between the ejector 6 and the cooling center column 10 from the injection hole 26, and then flows into the compression chamber 14 from the moving air gap. When in the cycle time period bc, the working medium enters the injection hole 1 23 through the air guide hole 22, and the working medium is sprayed into the moving air gap between the ejector 6 and the main cylinder sleeve 8. The working medium flows along the moving air gap, merges into the annular confluence groove 1 24, and then flows back into the air spring chamber 2 2002 from the air inlet hole 1 25.

[0087] The complementary and enhanced flotation process is that when the pressure of the gas spring chamber 1 2001 rises and the pressure of the gas spring chamber 2 2002 drops, the gas injection hole 3 29 ejects the trace gas in the gas spring chamber 1 2001, flows through the moving air gap formed between the inner wall of the first cylinder 601 and the outer wall of the T-shaped middle column 9, and enters the gas spring chamber 2 2002. In the symmetrical second half of the cycle, the gas injection hole 4 30 ejects the trace gas in the gas spring chamber 2 2002, and flows back to the gas spring chamber 1 2001 along the moving air gap. Fig.24 , Fig.25 It can be seen that due to the symmetry of the pressure difference, the realization of the above-mentioned flotation process does not require that the dynamic pressure amplitudes in the compression chamber 14, the gas spring chamber 1 2001, and the gas spring chamber 2 2002 are equal.

[0088] The principle of radial support of the power piston 7 is as follows: when the power piston 7 moves toward the back pressure chamber 17, the back pressure chamber 17 is compressed and the pressure increases. When the upper pump air hole 36 intersects with the air inlet hole three 38, the working medium in the gas chamber 16 enters the high-pressure air chamber 31 of the power piston 7 along the upper pump air hole 36 and the air inlet hole three 38. Due to the pressure difference between the high-pressure air chamber 31 and the low-pressure air chamber 34, the working medium will be sprayed into the moving air gap between the power piston 7 and the main cylinder sleeve 8 through the jet hole five 32, flow along the air gap, merge into the annular confluence groove two 33, and then enter the low-pressure air chamber 34 through the air inlet hole two 35; when the power piston 7 moves away from the back pressure chamber 17, the back pressure chamber 17 is depressurized due to volume expansion. When the lower pressure relief hole 37 intersects with the vent hole four 39, the working medium in the low-pressure air chamber 34 will enter the gas chamber 16 along the vent hole four 39 and the lower pressure relief hole 37, and flow back into the back pressure chamber 17. Under the reasonable matching parameters of holes, slots, air chambers and motion air gaps, the high-pressure air chamber 31 and the low-pressure air chamber 34 will maintain a quasi-static pressure condition, and there will always be a directional flow from the jet hole 5 32 to the confluence slot 2 33 in the air film. In each cycle, the amount of gas consumed by the back-pressure chamber 17 pumping gas to the high-pressure air chamber 31 will be compensated by the pressure relief process of the low-pressure air chamber 34 to the back-pressure chamber 17. Because the amount of gas involved in the air film flow only accounts for a small part of the gas volume of the high-pressure and low-pressure air chambers, the high-pressure and low-pressure air chambers will only fluctuate slightly at their respective pressure levels, showing quasi-steady-state characteristics.

[0089] The function of the pressure equalizing hole 40 is that when a pressure deviation occurs between the pressure of the gas spring chamber 1 2001 and the pressure of the gas spring chamber 2 2002 at the midpoint of the oscillation of the ejector 6, the working medium in the gas spring chamber 1 2001 and the gas spring chamber 2 2002 will undergo a short and sufficient pressure equalizing flow process through the pressure equalizing hole 40, thereby suppressing the accumulation of pressure deviation.

[0090] The function of the second pressure equalizing hole 41 is that when a pressure deviation occurs between the compression chamber 14 and the back pressure chamber 17 at the midpoint of the oscillation of the power piston 7, the working medium in the compression chamber 14 and the back pressure chamber 17 will undergo a short and sufficient pressure equalizing flow process through the second pressure equalizing hole 41, thereby suppressing the accumulation of pressure deviation.

[0091] The purpose of the first magnet 43 and the second magnet 44 is to prevent the circumferential pulsation of the displacer 6 and the power piston 7, so that the air holes correspond to each other in an even manner, avoid the damage of the gas bearing due to the misalignment of the corresponding air holes, and make the air flotation effect invalid.

[0092] The low-pressure air chamber 34 of the power piston 7 in this embodiment includes two parts connected to each other in an upper and lower direction. Accordingly, two annular confluence grooves 2 33 are provided on the outer wall of the power piston 7. The annular confluence grooves 2 33 are symmetrically arranged relative to the circumferentially arranged jet holes 5 32.

[0093] Embodiment 2

[0094] like Figures 14 to 16 As shown, the difference between the second embodiment and the first embodiment is that the main cylinder sleeve 8 in the embodiment includes an upper cylinder sleeve 801 and a lower cylinder sleeve 802 which are both fixedly connected to the outer shell, the upper cylinder sleeve 801 includes an inner cylinder 801a and an outer cylinder 801b connected by a bottom plate 27, there is a moving air gap between the inner wall of the ejector 6 and the outer wall of the inner cylinder 801a, there is a moving air gap between the outer wall of the ejector 6 and the inner wall of the outer cylinder 801b, and the gas spring chamber 20 inside the ejector 6 is connected to the T-shaped center column 9. The upper cylinder sleeve 801 is divided into a gas spring chamber 1 2001 and a gas spring chamber 2 2002. The bottom of the upper cylinder sleeve 801 is fixedly sealed and connected to the top of the cooling middle column 10. The interior of the partition column 11, the interior of the cooling middle column 10, the bottom of the T-shaped middle column 9 and the upper cylinder sleeve 801 form a cavity for circulating cooling medium. There is a moving air gap between the inner wall of the lower cylinder sleeve 802 and the outer wall of the power piston 7. The bottom plate 27 of the upper cylinder sleeve 801 is provided with a vent hole 3 28 for connecting the compression chamber separated by the bottom plate 27. 14, the vent hole 15 is arranged at the bottom of the outer cylinder 801b; the bottom of the discharger 6 is evenly provided with an air guide hole 22 connected to the compression chamber 14 along the circumference, and the outer wall of the discharger 6 is evenly provided with an injection hole 23 connected to the air guide hole 22 along the circumferential direction, and the outer wall of the discharger 6 is also provided with an annular confluence groove 24, and the annular confluence groove 24 is evenly provided with an air inlet hole 25 connected to the gas spring chamber 2002, and the inner wall of the discharger 6 is evenly provided with an injection hole 26 along the circumferential direction. When the force is greater than the pressure of the gas spring chamber 2002, the jet hole 23 throttles the jet to form an air flotation effect in the moving air gap between the ejector 6 and the outer wall of the outer cylinder 801b; when the pressure of the gas spring chamber 2002 is greater than the pressure of the compression chamber 14, the jet hole 26 throttles the jet to form an air flotation effect in the moving air gap between the ejector 6 and the outer wall of the inner cylinder 801a, and the air flotation effect provides radial support for the reciprocating motion of the ejector 6; the outer diameter of the T-shaped center column 9 is greater than the outer diameter of the inner cylinder 801a. The upper cylinder sleeve 801 and the lower cylinder sleeve 802 can use cylinder sleeves of different diameters. Preferably, the upper cylinder sleeve 801 has a larger diameter and the lower cylinder sleeve 802 has a smaller diameter. This can reduce the caliber of the entire machine and adapt to scenarios that are sensitive to caliber. Since this embodiment shortens the length of the cooling center column 10 relative to the first embodiment, the upper cylinder sleeve 801 and the cooling center column 10 are not required to be strictly coaxial, which reduces the difficulty of processing and assembling the cooling center column 10 and the cylinder sleeve, and is more suitable for high-power applications.

[0095] The working principle of radial support achieved by the displacer 6 and the power piston 7 is the same as that in the above example, except that the upper cylinder sleeve 801 structurally replaces the portion between the compression chamber of the cooling center column 10 and the T-shaped center column 9 in the above example.

[0096] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A double-actuator air-floating free piston Stirling generator with a cooling center column, characterized in that: It includes an outer shell, a heat head, a hot end heat exchanger, a regenerator, a cooler, an ejector, a power piston, a main cylinder sleeve, a T-shaped center column, a cooling center column, a spacer column and a linear motor assembly. The outer shell, the heat head and the cooling center column form a closed cavity. The ejector is arranged inside the heat head to form an expansion cavity between the heat head and the hot end heat exchanger. The hot end heat exchanger, the regenerator and the cooler are arranged in the annular flow channel between the heat head and the ejector in sequence. The main cylinder sleeve is arranged in the outer shell and fixedly connected to the outer shell. There is a moving air gap between the outer wall of the displacer and the inner wall of the main cylinder sleeve, and there is a moving air gap between the inner wall and the cooling center column or the main cylinder sleeve. The power piston is arranged between the main cylinder sleeve and the cooling center column. There is a moving air gap between the outer wall of the power piston and the inner wall of the main cylinder sleeve, and there is a moving air gap between the inner wall and the cooling center column. The power piston, the displacer, the cooling center column and the main cylinder sleeve form a compression chamber. The main cylinder sleeve is evenly provided with ventilation holes for connecting the compression chamber and the cooler flow channel along the circumferential direction. The partition column is arranged At the bottom of the cooling center column, a gas chamber is formed between the partition column and the cooling center column. The power piston, the outer shell and the cooling center column form a back pressure chamber. The lower part of the cooling center column is evenly provided with two vents for connecting the back pressure chamber and the gas chamber along the circumferential direction. The gas chamber is a component of the back pressure chamber volume; the T-shaped center column is arranged inside the ejector and is fixedly connected to the cooling center column or the top of the main cylinder sleeve. The ejector includes a No. 1 cylinder, which is fixed to the middle part of the ejector through a partition. The inner wall of the No. 1 cylinder is connected to the inner wall of the ejector. There is a moving air gap between the outer walls of the T-shaped center column, and the gas spring chamber inside the ejector is divided into gas spring chamber one and gas spring chamber two by the T-shaped center column and the cooling center column or the T-shaped center column and the main cylinder sleeve. The cavity formed by the interior of the partition column, the interior of the cooling center column and the bottom of the T-shaped center column or the interior of the partition column, the interior of the cooling center column, the bottom of the T-shaped center column and the upper part of the main cylinder sleeve is used for circulating cooling medium; the linear motor assembly is arranged between the outer shell and the main cylinder sleeve, and the annular magnet in the linear motor assembly is fixedly connected to the bottom of the power piston through a magnet base.

2. The Stirling generator according to claim 1, characterized in that: There is a moving air gap between the inner wall of the ejector and the cooling center column, and the gas spring cavity inside the ejector is divided into gas spring cavity 1 and gas spring cavity 2 by the T-shaped center column and the cooling center column. The cavity surrounded by the interior of the partition column, the interior of the cooling center column and the bottom of the T-shaped center column is used to circulate the cooling medium; the bottom of the ejector is evenly provided with air guide holes connected to the compression cavity along the circumference, and the outer wall of the ejector is evenly provided with jet holes connected to the air guide holes along the circumferential direction. The outer wall of the ejector is also provided with an annular confluence groove, and the annular confluence groove is evenly provided with gas springs. The first air inlet hole is connected to the second air spring chamber, and the inner wall of the ejector is evenly provided with two jet holes along the circumferential direction. When the pressure of the compression chamber is greater than the pressure of the second air spring chamber, the first jet hole throttles and sprays the jet, forming an air flotation effect in the moving air gap between the ejector and the main cylinder sleeve; when the pressure of the second air spring chamber is greater than the pressure of the compression chamber, the second jet hole throttles and sprays the jet, forming an air flotation effect in the moving air gap between the ejector and the cooling center column, and the air flotation effect provides radial support for the reciprocating motion of the ejector, and the outer diameter of the T-shaped center column is greater than the outer diameter of the cooling center column.

3. The Stirling generator according to claim 1, characterized in that: The main cylinder sleeve includes an upper cylinder sleeve and a lower cylinder sleeve, both of which are fixedly connected to the outer shell, the upper cylinder sleeve includes an inner cylinder and an outer cylinder connected by a bottom plate, there is a moving air gap between the inner wall of the displacer and the outer wall of the inner cylinder, there is a moving air gap between the outer wall of the displacer and the inner wall of the outer cylinder, the gas spring chamber inside the displacer is divided into gas spring chamber one and gas spring chamber two by the T-shaped middle column and the upper cylinder sleeve, the bottom of the upper cylinder sleeve is fixedly sealed and connected to the top of the cooling middle column, the cavity surrounded by the interior of the partition column, the interior of the cooling middle column, the bottom of the T-shaped middle column and the upper cylinder sleeve is used to circulate cooling medium, there is a moving air gap between the inner wall of the lower cylinder sleeve and the outer wall of the power piston, a vent hole three is provided on the bottom plate of the upper cylinder sleeve for connecting the compression chamber separated by the bottom plate, the vent hole one is provided at the bottom of the outer cylinder The bottom of the ejector is evenly provided with air guide holes connected to the compression chamber along the circumference, the outer wall of the ejector is evenly provided with jet holes connected to the air guide holes along the circumferential direction, the outer wall of the ejector is also provided with an annular confluence groove, and the annular confluence groove is evenly provided with an air inlet hole connected to the gas spring chamber 2, and the inner wall of the ejector is evenly provided with jet holes along the circumferential direction. When the pressure of the compression chamber is greater than the pressure of the gas spring chamber 2, the jet hole 1 throttles the jet to form an air flotation effect in the moving air gap between the ejector and the outer wall of the outer cylinder; when the pressure of the gas spring chamber 2 is greater than the pressure of the compression chamber, the jet hole 2 throttles the jet to form an air flotation effect in the moving air gap between the ejector and the outer wall of the inner cylinder, and the air flotation effect provides radial support for the reciprocating motion of the ejector; the outer diameter of the T-shaped center column is greater than the outer diameter of the inner cylinder.

4. The Stirling generator according to claim 3, characterized in that: The upper cylinder sleeve and the lower cylinder sleeve can be cylinder sleeves with different diameters.

5. The Stirling generator according to claim 1, characterized in that: The air gap width of the moving air gap formed between the inner wall of the No. 1 cylinder and the outer wall of the T-shaped middle column is less than 0.02 mm, and the length of the moving air gap is greater than 4 times the single-side stroke of the ejector.

6. The Stirling generator according to claim 1, characterized in that: The outer wall of the T-shaped center column or the inner wall of the No. 1 cylinder is evenly provided with jet holes along the circumferential direction, the jet hole connected to the gas spring chamber one is the jet hole three, and the jet hole connected to the gas spring chamber two is the jet hole four. When the pressure of the gas spring chamber one is greater than the pressure of the gas spring chamber two, the jet hole three throttles the jet to form an air flotation effect in the moving air gap between the inner wall of the No. 1 cylinder and the outer wall of the T-shaped center column; when the pressure of the gas spring chamber two is greater than the pressure of the gas spring chamber one, the jet hole four throttles the jet to form an air flotation effect in the moving air gap between the inner wall of the No. 1 cylinder and the outer wall of the T-shaped center column. The air flotation effect provides radial support for the reciprocating motion of the ejector.

7. The Stirling generator according to claim 6, characterized in that: The distance between the jet hole 3 and the jet hole 4 is greater than twice the single-side stroke of the ejector.

8. The Stirling generator according to any one of claims 1 to 7, characterized in that: The power piston contains a high-pressure air chamber and a low-pressure air chamber. The outer wall of the power piston is evenly provided with jet holes five connected to its high-pressure air chamber along the circumferential direction. The outer wall of the power piston is also provided with an annular confluence groove two, and the annular confluence groove two is evenly provided with air inlet holes two connected to the low-pressure air chamber of the power piston. The side wall of the cooling middle column and the partition column that form the gas chamber is evenly provided with upper pump holes and lower pressure relief holes along the circumferential direction. The inner wall of the power piston is also evenly provided with air inlet holes three and air vent holes four along the circumferential direction. The air inlet hole three cooperates with the upper pump hole to connect the high-pressure air chamber and the back-pressure chamber, and the air vent hole four cooperates with the lower pressure relief hole to connect the low-pressure air chamber and the back-pressure chamber. When the jet hole five is throttled for jetting, an air flotation effect is formed in the moving air gap between the outer wall of the power piston and the inner wall of the main cylinder sleeve, providing radial support for the reciprocating motion of the power piston.

9. The Stirling generator according to claim 8, characterized in that: The distance between the upper pump air hole and the air inlet hole three is smaller than the single-sided stroke of the power piston, the distance between the lower pressure relief hole and the air vent hole four is smaller than the single-sided stroke of the power piston, the air inlet hole three is closer to the T-shaped center column than the upper pump air hole, and the lower pressure relief hole is closer to the T-shaped center column than the air vent hole four.

10. The Stirling generator according to claim 1, characterized in that: The T-shaped center column and the No. 1 cylinder are provided with a pressure equalizing hole 1 for instantaneously connecting the gas spring chamber 1 and the gas spring chamber 2.

11. The Stirling generator according to claim 1, characterized in that: The power piston and the main cylinder sleeve are provided with a second pressure equalizing hole for instantaneously connecting the compression chamber and the back pressure chamber.

12. The Stirling generator according to claim 1, characterized in that: A magnetic suspension base is fixed at the bottom of the outer shell, and No. 1 magnets that cooperate with each other are evenly fixed on the magnetic steel base and the magnetic suspension base along the circumferential direction.

13. The Stirling generator according to claim 1, characterized in that: The T-shaped center column and the inner wall of the ejector are respectively and evenly fixed with No. 2 magnets that cooperate with each other along the circumferential direction.

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