SK1812022U1 - Stirling engine - Google Patents

Abstract

Cylinders (3, 4) of the engine comprise a piston (1, 2) with a recess (12) where a heat exchanger (10, 11) is situated. The heat exchanger (10) of the first cylinder (3) is connected to a heater (5)​, the heat exchanger (11) of the second cylinder (4) is connected to a cooler (6)​. From both cylinders (3, 4)​, a two-way passage (9) and a one-way outlet (13) are conducted to a regenerator (8) situated in a connecting channel (7)​. Heat exchangers (10, 11) are attached to the heads of the cylinders (3, 4)​, and are provided with a through-opening (17) through which a pin (15) formed on the piston (1, 2) passes. When the piston (1, 2) is in the top dead centre, the pin (15) closes the two-way passage (9)​, and the body of the piston (1, 2) closes the one-way outlet (13)​. The heat exchangers (10, 11) are preferably lamellar provided with a fluid circuit. Pistons (1, 2) are parallel, preferably connected to a cam mechanism of the stroke-drop-delay type.

Description

The field of technology

The technical solution refers to a new design solution for the Stirling engine of type A, enabling the achievement of higher efficiency, especially for use in the energy sector.

Current state of the art

The classical Stirling engine type a is a two-cylinder hot air engine. Its construction is described, for example, by Wikipedia. The Stirling engine is described here as an external combustion engine operating with cyclic compression and expansion of the working gas. This engine has two working pistons in separate cylinders, each with its own piston. One is a warm cylinder, also called an expansion cylinder, this cylinder is connected to a heater located on the outside of the cylinder. The second is a cold cylinder, also called a compression cylinder, it is connected to a cooler located on the outside of the cylinder. With the help of pistons, the working gas is compressed at low temperature and expanded at high temperature. The working gas is moved from the warm cylinder to the cold one and vice versa through the regenerator, which is connected between the cylinders. The connection between the cylinders is ensured by means of a connecting channel with a two-way passage into the working space of the cylinders. The regenerator is a heat exchanger that stores thermal energy in the time between expansion and compression of the working gas. The regenerator can form a filling located in the connecting channel between the cylinders, or alternatively, an individual regenerator of a suitable type is connected in the two-way connecting channel between the cylinders. In the hot cylinder, the gas expands at the high temperature of the heater. In the cold cylinder, the gas is compressed at the low temperature of the radiator. Pistons are equipped with a movement mechanism, which is usually a crankshaft. The pistons are at an angle to each other, usually 90°. It is an engine with a closed circuit, in which the transformation of thermal energy into mechanical work takes place.

An example of another design solution of a type a Stirling engine is the engine according to CZ PV 2002-2455. Two pistons are described here which are at an acute angle to each other, these pistons are connected by means of a Hook joint set at an obtuse angle greater than 120° and less than 180°. The piston cylinders are connected here by a simple connecting pipe. The regenerator and cooler are located outside the connecting pipe, on the channel formed by the so-called through the equalizing pipe, which has an inlet and outlet to the cold cylinder. Inputs and outputs to/from the connecting pipe are made through two-way passages. The heat exchanger consists of both a heating chamber, arranged as the end part of the cylinder above a cooled, cold piston, and a connecting pipe.

In all known types of Stirling engine, the pistons have the form of a simple solid body in a shape corresponding to the shape of the piston in which the piston is located, while the piston has a straight face and bottom. In the terminology of the field, the name cylinder is usually used for the piston rod of the Stirling engine, although sometimes the piston rod has a different shape, for example, as a vessel with a cross section of an oval or a regular polygon. The shape of the piston, whose body is a cylinder, prism, octahedron, etc., corresponds to this.

The alpha Stirling engine is notable for its efficiency. Currently, the possibility of using alternative and renewable energy sources is increasing its importance. The problem with these devices is the dead space of the pistons, which reduces the efficiency achieved.

The disadvantage of currently known alpha type Stirling engines is that they do not allow achieving an ideal cycle in terms of efficiency. A temporary dead space is formed above the pistons, causing a reduced compression ratio of the pistons. Some types of regenerators with a relatively low heat exchange surface are used. The path of the working gas is relatively long. The heat exchange surfaces on which the working gas is heated or cooled are relatively small. Another disadvantage is that the heat source cannot be far from the engine. The motor can only be connected to one heat source. It is not possible to regulate by means of cyclical closing of the expansion and compression space, or unidirectional flow of the working gas.

The essence of the technical solution

The above-mentioned disadvantages are largely eliminated by the technical solution. The technical solution significantly improves and modifies the design of the Stirling engine of the alpha type, including two movable pistons each in one cylinder, a regenerator, a heater as a source of thermal energy outside the cylinder and a cooler as a place of absorption of thermal energy outside the cylinder. Both the heater and the cooler are located outside the cylinders and the regenerator is located in the connecting channel that connects the working space of the first cylinder with the working space of the second cylinder, the connecting channel being connected to the working space of the cylinders through two-way passages. The essence of the new solution is that both pistons are equipped with at least one recess, while k

SK 181-2022 U1 the first heat exchanger is connected to the heater and the second heat exchanger is connected to the cooler, where these heat exchangers, or their heat exchange surfaces are located in the working space of the cylinders and their shape and dimensions, as well as their location, correspond to the recess so that they at least partially fit into the recess of the pistons. The first heat exchanger fits into the piston recess in the first cylinder and the second heat exchanger fits into the piston recess in the second cylinder.

Advantageously, a one-way outlet to the regenerator is led from the working area of each cylinder. One-way outlets are taken out of the working space of the cylinders, always in a different place than the two-way passage that opens into the working space.

The one-way outlet is preferably equipped with a one-way cap at the point of exit from the cylinder.

Advantageously, the piston body includes a mandrel which closes a two-way passage from the cylinder of this piston to the connecting channel at the position of the piston in which the piston is at top dead center. In that case, the two-way passage is located above the thorn. The dimensions, shape and position of the mandrel are chosen in such a way that when the piston is in the top dead center position, the mandrel fits tightly against the two-way passage and closes the two-way passage.

Advantageously, the mandrel extends from the bottom of the recess.

Advantageously, the first and second heat exchangers are equipped with an opening for the movement of the mandrel and the medium. Through this opening, the mandrel passes through the heat exchanger during its movement, while it passes through the entire heat exchanger at least at the top dead center of the piston.

Advantageously, heat exchangers with their upper part fit tightly on the front of the cylinders, in a different place than where the two-way channel opens into the working space. The shapes, dimensions and location of the elements correspond to each other in such a way that in the position of the top dead center of the piston, the entire heat exchangers are stored in the recess of the pistons and fit into it only with a gap necessary for the movement of the medium. The size of the gap can be calculated and determined as the size required for the flow of the working gas. In that case, the one-way outlets from the cylinders are advantageously located above the piston, in such a place that the one-way outlet is closed by the piston in the top dead center position.

Advantageously, lamellar heat exchangers are chosen for the cylinders. In this case, there is a lamellar heat exchanger with a liquid circuit in both cylinders.

The pistons are preferably in a position where their axes are parallel, and in this position they are equipped with a lift-decrease-delay cam mechanism.

The cams of the lift-decrease-delay cam mechanism are advantageously mechanically connected for rotary movement in the same direction and with the same number of revolutions. This makes it possible, for example, to choose a mechanism with disc cams on the shaft, or a mechanism with drum cams mechanically connected via gearing.

The proposed new solution of the Stirling engine type alpha has an increased power compared to the current state and is usable mainly for generators for the production of electricity. It makes it possible to efficiently use the waste heat of exhaust gases from combustion. It is also suitable for solar heat sources. When using thermal energy from solar radiation, up to 40% of heat can be converted into electrical energy. The proposed Stirling engine can be used to produce electricity in cogeneration units, in construction objects, for example for general objects, households or business operations. It can also enable the use of waste heat from industrial processes, such as the operations of bakeries, roasters, etc., which can be used for the production of electricity with the help of this engine. The main advantage of this engine is the high efficiency of the engine, higher than in the current state. An almost ideal Stirling cycle is achieved. The proposed solution achieves a reduction of the dead space in the cylinders and an increase in their compression ratio. By choosing the regenerator forming the filling in the connecting pipeline, a large heat exchange surface of the engine regeneration element is created. The minimum path of the working gas is achieved with a large usable heat exchange surface of the heat exchangers. The heat source can be remote from the engine. Another advantage is that the designed motor can be connected to several heat sources at the same time. The designed engine enables cyclic closing of the expansion and compression spaces as well as unidirectional flow of the working gas.

Overview of images on drawings

The technical solution is explained with the help of drawings where they show

fig. 1 diagram of an exemplary Stirling engine according to the technical solution, looking at a vertical section through the pistons and connecting channel.

fig. 2 is a top view of a cross-section of one cylinder with a piston and a heat exchanger, at the location indicated as A-A in fig. 1

fig. 3 A, B, C and fig. 4 D, E different phases of work of the designed engine according to the position and direction of movement of the pistons, p

SK 181-2022 U1 by indicating the direction of movement of media and cams.

fig. 5 detail of the heat exchanger, indicated in the previous images for simplicity only in block form, in a three-dimensional view from the front of a vertical section through the center of the heat exchanger.

fig. 6 spatial view obliquely from below of the entire heat exchanger from fig. 5

Implementation examples

An example of the best implementation of a technical solution is the Stirling engine according to Figures 1 to 6.

It is a Stirling engine of the basic alpha type, which is structurally modified according to the technical solution. It contains two pistons 1, 2, each movable in one cylinder 3, 4, a heater 5 forming a source of heat energy and a cooler 6, as a heat energy receiver. The cylinders 3, 4 have a working space above the pistons 1, 2, while the working space of the first, expansion cylinder 3 is connected to the working space of the second, compression cylinder 4 by a connecting channel 7. A regenerator 8 is built into the connecting channel 7, formed by an accumulation material capable of absorbing and accumulate heat from the flowing medium. Accumulation materials are known, for example glass balls, or crumb based on particles of porous ceramic material, or a system of sheet metal plates can be used. Gas is used as the working medium. Both the heater 5 and the cooler 6 are located outside the cylinders 3, 4. The connecting channel 7 is connected to the working space of the cylinders 3, 4 via two-way passages 9. The first heat exchanger 10 is connected to the heater 5 and the second heat exchanger 11 is connected to the cooler 6. Both pistons 1, 2 are equipped with a recess 12. The first heat exchanger 10 is located in the working space of the first, expansion cylinder 3, the second heat exchanger 11 is located in the working space of the second, compression cylinder 4. In both cylinders, the heat exchanger 10, 11 is stored in selected 12. In this exemplary embodiment of the ideal engine, for reasons of comprehensibility and illustration, such a specific shape of the elements is chosen to correspond to the established nomenclature in the given field. That's why the cylinders 3, 4 here really have a cylindrical shape, that is, they have the form of a hollow body with a cross section in the shape of a circle. Adequately, the exemplary pistons 1, 2 here have the form of solid bodies, the peripheral wall of which is also in the shape of a circle. In practice, but as cylinders 3, 4 according to the technical solution, they can be used, and therefore understood as cylinders in the sense of the technical solution, all shapes used and called as engine cylinders in the given field, i.e. also bodies with an elliptical cross-section, or as polyhedrons and so on .

From the working space of each cylinder 3, 4, a one-way outlet 13 is led to the regenerator 8 in a place other than the two-way passage 9. These one-way outlets 13 are equipped with a one-way valve 14, for example a simple shut-off valve, at the point of exit from the cylinders 3, 4 .

The body of the pistons 1, 2 contains a mandrel 15, which allows to temporarily close the two-way passage 9 into the connecting channel 7. This possibility is achieved by the shape and mutual suitable location of the mandrel 15 and the two-way passage 9. The two-way passage 9 is situated above the mandrel 15, and the dimensions are chosen so that that at the top dead center of the piston 1, 2, the mandrel 15 fits tightly against the two-way passage 9 of the corresponding piston 1, 2 and the given two-way passage 9 is closed by the mandrel 15.

In the demonstrated ideal embodiment of the technical solution, the pistons 1, 2 have a peripheral wall in the shape of a cylindrical shell, and the mandrel 15 has the shape of a cylinder with a beveled upper edge. The recess 12 has a peripheral wall also in the shape of a cylindrical shell, and the mandrel 15 extends in the middle from the bottom 16 of the recess 12, so that the recess 12 creates an annulus-shaped cavity in the body of the pistons 1, 2 between the mandrel 15 and the cylindrical wall of the recess 12. The existence of the mandrel 15 in the recess 12 both heat exchangers 10, 11 are adapted by their shape and type. Lamellar heat exchangers 10, 11 are used, with heat exchange surfaces formed by a set of lamellae, and both of these lamellar heat exchangers 10, 11 are equipped with an opening 17, forming a through tunnel for the movement of the mandrel 15. The opening 17 in each of the heat exchangers 10, 11, in this particular example the central one, together with the recess 12, enables more efficient pushing of the working medium around the heat exchange surfaces of the heat exchangers 10, 11 during the movement of the pistons 1, 2. The mandrel is inserted and extended into this opening 17 when moving pistons 1, 2. When moving piston 1, 2 up, the mandrel 15 moves gradually from the bottom up and pushes the medium around the respective heat exchanger 10, 11, up into the two-way passage 9 and one-way outlet 13. When moving piston 1, 2 down the medium flows into the cylinder 3 only through the two-way passage 9, and in the cylinder 3, 4 it flows down around the heat exchange surfaces of the respective heat exchanger 10, 11 and below it. Depending on which cylinder 3, 4 is concerned, the working medium is heated and expanded, or the working medium is cooled and reduced in volume. As a working medium, hydrogen, helium, nitrogen or air are particularly suitable.

In the position when the piston 1, 2 is at the top dead center, its mandrel 15 passes through the corresponding heat exchanger 10, 11 in the entire height dimension of the heat exchanger 10, 11, while the mandrel 15 closes the two-way passage 9. It is not a condition that the mandrel be 15 in the middle of the recess 12 or the cylinder 3, 4 or to be as high as the edge of the piston 1, 2 depends on the choice of shapes and the location of the engine elements, for example it can be higher, as well

SK 181-2022 U1 show pictures in this exemplary embodiment.

In the optimal implementation of the technical solution as shown in the exemplary embodiment in the pictures, the heat exchangers 10, 11 in the working space of the cylinders 3, 4 are placed in such a way that their upper part rests closely on the face of the cylinders 3, 4 and at the top dead center position of the pistons 1, 2 heat exchangers 10, 11 completely fit into the recess 12 in the piston 1, 2, with a circumferential gap 18 necessary for the flow of the working medium when the pistons 1, 2 move. to the regenerator 8 are located above the piston 1, 2, and the pistons 1, 2 have such dimensions and shape that at the top dead center position of the relevant piston 1, 2, the one-way outlet 13 at this piston 1, 2 is closed. Thus, at the upper position of the first piston 1 in the expansion cylinder 3, the one-way outlet 13 from the expansion cylinder 3 is closed, and at the upper position of the second piston 2 in the compression cylinder 4, the one-way outlet 13 from the compression cylinder 4 is closed. In the example shown, the faces of the cylinders 3, 4 and the upper sides of the pistons 1, 2 are straight, but this is not a condition, they can be, for example, convex, convex or otherwise shaped, but corresponding to each other in shape.

For the engine according to the technical solution, it is optimal to choose lamellar heat exchangers 10, 11 with a liquid circuit for the cylinders 3, 4, structurally adapted to the shape and dimensions of the recess 12 in the pistons 1, 2 and the shape and location of the pins 15, as shown in figures 5 and 6. Technical the solution also solves ensuring the optimal movement of pistons 1, 2. According to the technical solution, pistons 1, 2 have parallel axes, unlike the classic Stirling engine of the alpha type. In order to achieve the desired movement, they are preferably equipped with a lift-drop-delay cam mechanism. The cams 19, 20 of the cam mechanism are mechanically connected for rotary movement in the same direction and with the same number of revolutions, for example by coupling on a shaft or, as in the example shown, by means of two shafts 21, 22 and a belt 23. The pistons 1, 2 are connected to the cam mechanism, for example via pulleys 24, 25.

Liquid circulation in the liquid circuit of the heat exchangers 10,11 is ensured in the usual way, using the pump 26.

A concrete example of motor operation is shown in the motor phase diagram in Figures 3 and 4 and is as follows.

fig. 3 A shows the state of the engine at the extreme positions of pistons 1, 2. The first piston 1, hot, is up, in the top dead center position, the second piston 2, cold, is down. Cam mechanism, specifically cam 20 in fig. 3 And to the right, ensures a short stay of the pistons 1, 2 in this position. In the position when the first piston 1 is at the top dead center, its mandrel 15 passes through the first heat exchanger 10 in the entire height dimension of the first heat exchanger 10 and closes the two-way passage 9 from the expansion cylinder 3. The two-way passage 9 from the compression cylinder 4, situated above the second by piston 2, is open. The one-way outlet 13 from the expansion cylinder 3 to the regenerator 8 closed the upper edge of the first piston 1. The one-way valve 14 closes the one-way outlet 13 from the compression cylinder 4. The flow of the working medium stops.

In fig. 3 B the first piston 1, hot, remains at the top dead center and closes the connecting channel 7 on the side of the expansion cylinder 3, while the second piston 2 moves up. During this movement, the second piston 2 compresses the cooled working medium contained in the compression cylinder 4 and pushes them further through the two-way passage 9 and the one-way outlet 13 into the connecting channel 7 and here into the regenerator 8. When the second piston 2 rises to the top dead center, its mandrel 15 closes the two-way passage 9 from the compression cylinder 4 and the edge of the second piston 2 close the one-way outlet 13 from the compression cylinder 3. The engine goes to the next phase according to fig. 3 C.

In the next phase according to fig. 3 C moves the first piston 1 down, from top dead center to bottom dead center. The second piston 2 remains up, in the top dead center position, and at the same time closes the connecting channel 7 on the side of the compression cylinder 4. The compressed working medium is pushed out of the connecting channel 7 by the pressure of compression and by suction as a result of the movement of the first piston 1, and flows only through the two-way passage 9 into the expansion cylinder 3. The one-way outlet 13 from the expansion cylinder 3 is closed by means of a one-way valve 14, for example in the form of a check valve. The working medium in the expansion cylinder 3 flows into the opening 17 in the first heat exchanger 10 and around its heat exchange surfaces, i.e. between its lamellae and through the gap 18. The working medium is heated by the heat exchange surfaces of the first heat exchanger 10, expands, and gradually fills the working space of the expansion cylinder 3 and presses the first piston 1 down to its limit lower position. The motor goes into the phase shown in fig. 4 D.

Figure 4 D shows the state of the engine at the extreme positions of the pistons 1, 2, where the first piston 1, hot, is at the bottom and the second piston 2, cold, is at the top dead center position. Cam mechanism, specifically cam 19 in fig. 4 D to the left, ensures a short stay of the pistons 1, 2 in this position. In the position when the second piston 2 is at top dead center, its mandrel 15 passes through the second heat exchanger 11 in the entire height dimension of the second heat exchanger 11 and closes the two-way passage 9 from the compression cylinder 4. The two-way passage 9 from the expansion cylinder 3, located above the first by piston 1, is open. The one-way outlet 13 from the compression cylinder 4 to the regenerator 8 closed the upper edge of the second piston 2. The one-way valve 14 closes

SK 181-2022 U1 one-way outlet 13 from the expansion cylinder 4. The flow of the working medium stops.

Subsequently, the first piston 1 moves up, and at the same time the second piston 2 moves down, as shown in fig. 4 E. In the expansion cylinder 3, when the first piston 1 moves up, the mandrel 15 slides gradually through the opening 17 from below and pushes the working medium up. The medium heated by the first heat exchanger 10 flows from the expansion cylinder 3 through the one-way outlet 13 and the two-way passage 9 into the connecting channel 7 and into the regenerator 8 in it.

The phase according to fig. 3 A. The above stages 3A to 4E are repeated in that order.

In the expansion cylinder 3, the working medium is heated through the first heat exchanger 10 by heat supplied from an external source, here designated as a heater 5, for example in the form of a combustion engine 10, a furnace or a solar heat source. The heat is accumulated in the regenerator 8, through which the working medium flows alternately from one side and the other. In the compression cylinder 4, heat is transferred from the heat-carrying medium to the second heat exchanger 11, and from there the heat is removed to the external outlet via the cooler 6. The largest heat supply for the external outlet occurs when the second piston 2 moves down.

SK 181-2022 U1

List of relationship tags

1 first piston 2 second piston 3 expansion cylinder 4 compression cylinder 5 heater 6 cooler 7 connecting channel 8 regenerator 9 two-way passage 10 the first heat exchanger 11 second heat exchanger 12 selection 13 one-way outlet 14 one-way closure 15 thorn

bottom hole gap

19, 20 cam

21, 22 shaft belt

24, 25 pulley pump

Claims (10)

1. A Stirling engine including two pistons (1, 2) movable each in one cylinder (3, 4), a regenerator (8), a heater (5) as a source of thermal energy and a cooler (6) as a place of absorption of thermal energy, where the heater ( 5) and the cooler (6) are located outside the cylinders (3, 4) and the regenerator (8) is located in the connecting channel (7), which connects the working space of the first cylinder (3) with the working space of the second cylinder (4), while the connecting the channel (7) is connected to the working space of the cylinders (3, 4) through two-way passages (9), characterized by the fact that both pistons (1, 2) are each equipped with at least one recess (12) and in the working space of each cylinder (3 , 4) there is at least one heat exchanger (10, 11) stored at least partially in this recess (12) in at least some working position of the piston (1, 2), while the heat exchanger (10) stored in the recess (12) of the first piston ( 1) is connected to the heater (5) and the heat exchanger (11) located in the recess (12) of the second piston (2) is connected to the cooler (6). 2. Stirling engine according to claim 1, characterized by the fact that from the working space of each cylinder (3, 4) there is a one-way outlet (13) to the regenerator (8), in a different place than the two-way passage (9) . 3. The Stirling engine according to claim 2, characterized in that each DC outlet (13) from the cylinder (3, 4) is equipped with a DC cap (14) at the point of exit from the cylinder (3, 4). 4. Stirling engine according to claims 2 and 3, characterized in that the body of the pistons (1, 2) includes a mandrel (15), while the two-way passage (9) from the respective cylinder (3, 4) to the connecting channel (7) is located above this mandrel (15), and while at the position of the top dead center of the piston (1, 2) the mandrel (15) closely abuts the two-way passage (9) so that at the given position of the piston (1, 2) the two-way passage (9) is a mandrel (15) closed. 5. Stirling engine according to claim 4, characterized in that the mandrel (15) extends from the bottom (16) of the recess (12). 6. Stirling engine according to claim 5, characterized in that the heat exchangers (10, 11) of each cylinder (3, 4) are equipped with an opening (17) for the movement of the mandrel (15) and when the piston (1, 2) is in the upper dead center, the mandrel (15) is located in this hole (17) and passes through the heat exchanger (10, 11) in the height direction. 7. Stirling engine according to claim 6, characterized by the fact that the heat exchangers (10, 11) fit tightly with their upper part on the front of the cylinders (3, 4) and fit into the recess of the piston (1) at the top dead center position of the pistons (1, 2) , 2) all these heat exchangers (10, 11) and all around there is a circumferential gap (18) for the flow of the working medium, while the one-way outlets (13) to the regenerator (8) are located above the pistons (1, 2) and at the position of the upper dead center of the piston (1, 2), the one-way outlet (13) of the piston (1, 2) is closed by this piston (1, 2) in the indicated position. 8. Stirling engine according to claims 1 to 7, characterized by the fact that in both cylinders (3, 4) there is a heat exchanger (10, 11) of the lamellar type with a liquid circuit. 9. Stirling engine according to claims 1 to 8, characterized in that the pistons (1, 2) have parallel axes and are equipped with a cam mechanism of the lift-fall-delay type. 10. The Stirling engine according to claim 9, characterized in that the cams (19, 20) of the cam mechanism are mechanically connected for rotational movement in the same direction and with the same number of revolutions.