EP3329110B1 - Hydrostirling-maschine - Google Patents

Description

Technical field of the invention

The invention relates to a hydrostirling machine according to the preamble of claim 1.

Stirling engines have been known for a long time and, despite their fundamental simplicity and despite the theoretically high achievable efficiency, have so far barely found their way into practice.

A "classic" Stirling engine has at least one cylinder filled with gas, for example air, an axially displaceable piston (also called a regenerator) held in this cylinder and a so-called working piston, which is likewise held axially movable in this cylinder. Here, displacement piston and piston are coupled together via a crankshaft, so that they perform an opposite movement, the phase angle is normally 180 degrees. In other embodiments of the Stirling engine, working pistons and displacers may also be arranged in separate but interconnected cylinders.

Such mechanical Stirling engines usually run relatively quickly, which also causes the problems that have hitherto prevented their breakthrough in practice: due to the relatively fast movements, the actual Stirling process deviates relatively strongly from the theoretically achievable Stirling process, which naturally leads to a deterioration of the Stirling process theoretically achievable efficiency leads. Furthermore, in particular, the working piston is subject to a high seal wear, which makes existing mechanical Stirling engines very expensive to maintain or greatly reduces their service life.

State of the art

From the generic DE 10 2006 028 561 B3 has become known as a so-called hydrostirling machine with a hydraulic motor and two hydrostirling units. Each hydrostirling unit here has a cylinder and a displacer axially movable in this cylinder. Here, the axial position of the displacer is actively controlled. In the hydrostirling machine described there, the working piston is replaced by an incompressible fluid which flows back and forth between the cylinders of the hydrostirling units, thereby driving the hydraulic motor serving as the energy converter unit. The hydrostirling machine shown has the advantage over "classic" Stirling engines with working piston that the working piston is replaced by a liquid, so that no sealing problems on the working piston occur at this point, and that the machine can basically run slower.

A disadvantage of in the DE 10 2006 028 561 B1 described machine is that the hydraulic motor between two half-cycles must change direction.

Subject of the invention

On this basis, the present object of the invention to improve a generic hydro-Stirling engine.

This object is achieved by a hydro-Stirling machine with the features of claim 1.

According to the invention, the energy converter unit is designed as a turbine unit with a turbine tank and a turbine wheel arranged in this turbine tank, in particular a Pelton turbine wheel. The use However, another constant pressure turbine would also be possible. The working fluid circuit has a plurality of lines, wherein in each case at least one working fluid line between a hydraulic Stirling unit and the turbine unit extend such that working fluid, which flows from a Hydrostirling unit to the turbine unit, first meets the turbine wheel and then into a range of Turbine tank falls below the turbine wheel. Furthermore, the working fluid circuit has at least two working fluid return lines, wherein in each case at least one working fluid return line connects the turbine container with a hydrostirling unit.

This makes it possible that the serving as an energy converter turbine wheel can always rotate in the same direction, which is very advantageous for driving a power generator. Furthermore, the two hydrostirling units are hydraulically decoupled. This has the advantage that they are not coupled exactly phase-locked. On the other hand, the high efficiency of a Pelton turbine can be used over a wide load range.

In order to achieve a seal between displacer piston and container inner wall in a simple, maintenance-free and friction-free manner, the displacement pistons are each part of a displacer piston unit which, except the displacer piston, has a cylinder jacket extending downwards from the displacer piston whose outer surface is substantially flush with the outer surface of the displacer piston, having.

To simplify the control of the displacers, they are preferably dimensioned to float. As a result, only one control, no control is necessary. The buoyancy can be achieved in particular by connecting each displacement piston to a buoyancy body.

Advantageous embodiments of the invention will become apparent from the dependent claims.

The invention will now be described in more detail by means of embodiments with reference to the figures. Hereby show:

Brief description of the figures

FIG. 1

A schematic representation of a first embodiment of the hydrostirling machine according to the invention, wherein the containers are not yet filled with working fluid,

FIG. 2

a more detailed representation of the first hydrostirling unit,

FIG. 2a

the detail D off FIG. 2 ,

FIG. 3

this in FIG. 2 Shown in a working state, wherein the displacer is lowered,

FIG. 4

this in FIG. 3 Shown, with the working piston raised,

FIG. 5

the hydrostirling machine FIG. 1 in a first working condition,

FIG. 5a

a pV diagram in which the the FIG. 2 corresponding states of the two hydrostirling units are shown,

FIG. 6

this in FIG. 5 Shown in a subsequent working condition,

FIG. 6a

the pV diagram with accordingly FIG. 6 marked states of the hydrostirling units,

FIG. 7

this in FIG. 6 Shown in a subsequent working condition,

Figure 7a

the pV diagram with accordingly FIG. 7 marked states of the hydrostirling units,

FIG. 8

this in FIG. 7 Shown in a subsequent working condition,

FIG. 8a

the pV diagram with accordingly FIG. 8 marked states of the hydrostirling units,

FIG. 9

This in FIG. 8 Shown in a subsequent working condition,

FIG. 9a

the pV diagram with accordingly FIG. 9 marked states of the hydrostirling units,

FIG. 10

a second embodiment in one of FIG. 1 appropriate representation,

FIG. 10a

the pV diagram with accordingly FIG. 10 marked states of the hydrostirling units,

FIG. 11

a third embodiment in one of FIG. 1 corresponding representation and

FIG. 12

a part of a hydrostirling unit with improved thermal separation.

Detailed description of preferred embodiments

First, with FIG. 1 a first embodiment of the invention Hydrostirling machine described, the illustration is schematic and without details.

The hydrostirling machine has three main elements, namely two similar hydrostirling units (first hydrostirling unit 10 and second hydrostirling unit 20), and a turbine unit 30, on. The hydrostirling units 10, 20 are, as mentioned, constructed identically and each have a container 11, 21, a heating head 12, 22 for heating the respective upper part of a container 11, 21, a displacer 13, 23 and a lifting device 16, 26 for lifting the respective displacement piston 13, 23. On a specific embodiment of the lifting devices 16, 26 will be discussed later. The lateral surfaces of the containers 11, 21 are each preferably constructed in two parts (in FIG. 1 not shown), so that a thermal separation of the upper, hot end, from the lower, cold region of the container takes place.

Each displacer piston 13, 23 has an annular insulation 13a, 23a and a regenerator 13b, 23b enclosed by this insulation 13a, 23a and at least partially gas-permeable. Here, it is preferable that the insulation 13a, 23a is flush with the regenerator 13b, 23b at the top but extends beyond its lower end (only in Figs FIGS. 2 to 4 ) Shown. The regenerators 13b, 23b may be made of wire mesh, for example. For sealing in each case extends a hollow cylinder open at the bottom, that is, a cylinder jacket 14, 24 from the outer edge of the displacer piston 13, 23. About bolts 91, 111, the lower edge of the cylinder jacket 14, 24 is connected to a buoyant body 90, 110. This will be later again with reference to the FIGS. 2 to 4 discussed in more detail. Displacement piston, cylinder jacket and buoyancy each form a displacement piston unit.

A turbine unit 30 is provided, via which the two hydrostirling units 10, 20 are connected to one another, which will be discussed in more detail later. The turbine unit 30 has a pressure vessel, referred to as a turbine tank 32, inside which a turbine wheel 34, which is preferably the turbine wheel of a Pelton turbine, is disposed. The turbine wheel 34 is connected by means of a guided through a pressure-tight bearing through the container wall of the turbine tank 32 shaft or by means of a magnetic coupling with a generator 36 for generating electricity. The generator 36 downstream electric units are not shown, since they are not relevant to the present invention.

As a rule, it is preferable to operate the hydrostirling machine under increased admission pressure of, for example, 10 to 50 bar, for which purpose a compressor or compressed gas cylinder 40 is provided, which is connected to the interior of the turbine tank 32 by a compressed gas line 42. The turbine tank 32 forms, as do the lower portions of the tanks 11, 21, the cold end of the hydrostirling engine. This is symbolized by the indicated cooling fins.

The hydraulic fluid circuit of the hydrostirling machine has the following components: Each of the two hydrostirling units 10, 20 is connected to the turbine unit 30 by means of a working fluid line 50, 60, which in each case in the region of the bottom of the container 11, 21 of the respective Hydrostirling- Unit begins and ends in a directed to the turbine wheel 34, controllable nozzle 56, 66 ends. Each of these working fluid line 50, 60 further includes a check valve 52, 62. These working fluid lines serve to ensure that working fluid, which preferably consists of water or predominantly of water, can flow from the respective container 11, 21 of a hydrostirling unit 10, 20 to the turbine unit 30 in order to drive the turbine wheel 34 there under pressure-to-speed conversion ,

Furthermore, each container 11, 21 of a hydraulic Stirling unit is connected by means of a working fluid return line 70, 74 with the turbine tank 32, in which in each case a driven in both directions pump 73, 76 is arranged. These working fluid return lines 70, 74 each extend from the container bottom to the container bottom (or near the container bottom) and each have a check valve 72, 78.

An exchange of working gas, such as nitrogen, between the containers does not take place, or only via solution of the working gas in the working fluid, so that the amount of gas in each cylinder is constant over time. The working fluid is preferably water.

It is preferable that - as shown - all containers have the same diameter.

Well, now with respect to the FIG. 2 a concrete preferred embodiment of a lifting device described, wherein for linguistic simplification only one lifting device, namely the lifting device of the first Hydrostirling unit 10 will be described. Of course, the lifting device of the second hydrostirling unit 20 is constructed exactly the same. The particular advantage of the lifting device now described is that it takes on a further function, namely the supply of working fluid flowing back from the turbine unit into the container of the hydrostirling unit, such that a good heat transfer between working fluid and working gas takes place.

It is, as already mentioned, a buoyancy body 90, for example in the form of a hollow ball, which is connected via connecting elements, such as bolts 91 with the cylinder jacket 14. The hollow body has a completely sheathed through hole through which a static riser 92 extends, the lower end is rigidly and tightly connected to the container 11 and into which the first working fluid return line 70 opens. Between the static riser 92 and the wall of the hole at least one bearing, for example in the form of a ball bearing, is provided. Marked in the FIG. 2 two such bearings 96. In the interior of the static riser 92, a movable riser 94 is mounted axially movable in the manner of a piston. Furthermore, the displacer 13 carries on its underside a deflector 98th

At the lower end of the movable riser 94, a backflow check valve, for example in the form of a preloaded ball valve, through which working fluid can pass from the static riser 92 into the movable riser 94 when a predetermined differential pressure is exceeded. In the region of the lower end, the outer wall of the movable riser pipe 94 carries piston sealing rings, which are shown symbolically. The piston seals are completely within the working fluid circuit. These details are in FIG. 2a symbolically represented. The upper end of the movable riser 94 has an upward opening 95. In the illustrated embodiment, the movable riser at the top is completely open, which is not mandatory.

The operation of the lifting device 16 will now be described with reference to Figures 3 and 4 explained in more detail. The buoyancy of the buoyant body 90 with respect to the working fluid (typically water) is such that the lower surface of the regenerator 13b is floating on the working fluid (as in FIG FIG. 3 shown), wherein a lower portion of the insulation 13a is immersed in the working fluid. In the passive state, that is, when no water flows through the riser pipes, this turns into FIG. 3 Shown one. If water returning from the turbine unit 30 then flows through the static riser 92, the return flow check valve opens, working fluid flows through the riser tubes, exits from the opening 95 at the upper end of the moveable riser and thus pushes the displacer upwards. Since working fluid can escape only between the upper end of the movable riser and the deflector, escapes working fluid at this point in the form of a film (hydrodynamic paradox). This is in FIG. 4 shown. In order for the movable riser 94 to sink into the static riser 92 when the displacer piston is descending, the deflector 98 must not tightly close the upper end of the moveable riser (ie the opening 95).

The required working fluid pressure is provided predominantly by the turbine unit, however, it is additionally provided in both directions a drivable pump 73 in the working fluid return line ( Fig. 1 ).

The operation of the machine just described will now be described with reference to a half cycle with respect to FIG FIGS. 5 to 9a described in more detail, wherein in the described embodiment, a pre-pressure of 12 bar prevails. The FIG. 5 shows the starting point of a cycle, whereby the starting time of a cycle can of course be determined arbitrarily. The FIG. 5a shows the pV diagram for FIG. 5 , wherein the states of the working gases of the two Hydrostirling units 10, 20 are shown. For (as already mentioned arbitrary) start time of the cycle, the displacer 13 of the first Hydrostirling unit 10 is in its top dead center, where it can abut the better heat transfer to the upper container wall. Furthermore, the container 11 has its maximum working fluid level and thus its minimum gas volume. The gas is located between the surface of the working fluid and the underside of the displacer 13, so it is relatively cold. The pressure in the container 11 of the first Hydrostirling unit 10 is the form, ie 12 bar.

The working fluid level in the turbine tank 32 is maximum and the pressure in the turbine tank is also the form, ie 12 bar. The instantaneous gas volume in the turbine tank corresponds to the gas volume in the tank 11 of the first hydrostirling unit 10.

The working fluid level of the second hydrostirling unit 20 is minimal and the underside of the displacer 23 rests on the surface of the working fluid. Also in the container 21 of the second Hydrostirling unit 20 prevails the form, ie 12 bar, the working gas is relatively hot.

Now, as in FIG. 6 shown, the first pump 73 is briefly driven in the return direction, so that the first displacer 13 is lowered until it hits the surface of the working fluid. Here, the relatively cold gas flows through the regenerator 13b of the displacer 13, wherein it is heated. As a result, the gas is isochoric compressed, in the illustrated embodiment to about 33 bar. The state of the second hydrostirling unit 20 does not change here.

Now, as in FIG. 7 shown, the second pump 76 is driven at a short open check valve 78 and thus the displacer 23 of the second Hydrostirling unit 20 is raised. As a result, the hot gas flows through the regenerator, cools and is thus isochorically decompressed, in the embodiment shown to about 4.3 bar.

Next, the check valve 78 is opened again, so that working fluid from the turbine tank 30 flows into the tank 21 of the second hydrostirling unit and in this case a pressure equalization takes place between the turbine tank and the tank 21 of the first hydrostirling unit ( Fig. 8 ). In the described embodiment prevails after completion of the pressure equalization in the turbine tank 30 and in the container 21, a pressure of about 8 bar. The working gas volume in these two containers is now the same. The turbine tank 30 has reached its minimum working fluid level and minimum pressure. Thus, there is the maximum pressure difference between the first stirling tank 10 and the turbine tank 30. This condition is in FIG. 8 shown.

Now the check valve 52 of the first working fluid line 50, the check valve 78 of the second working fluid return line 74 and the control nozzle 56 is opened, so that a pressure equalization between the container 11 of the first Hydrostirling unit 10, the turbine tank 30 and the container 21 of the second Stirling unit 20 can take place. The hot gas in the container 11 expands substantially isothermally and forces the working fluid out of the container 11. The displacer continues to float on the working fluid. Working fluid flows from the container 11 of the first Hydrostirling unit 10 through the first working fluid line 50, impinges on the turbine wheel 34 and thus enters the turbine tank 32. The control nozzle 56 is in this case only partially open and opens with increasing pressure equalization more and more. Here, work is done so that the generator 36 generates electrical energy. By the open shut-off valve 76 of the second working fluid return line 74 not only increases the working fluid level in the turbine tank 30 but also in the container 21 of the second Hydrostirling unit 20 until the state of FIG. 9 is reached, in which the two hydrostirling units opposite to your states FIG. 5 have exchanged. Now begins the second half-cycle with the isochoric compression in the container 21 of the second hydrostirling unit.

The FIG. 10 shows a second embodiment of the invention in a representation corresponding to Figure 1 representations. Basically, the hydrostirling machine of the second embodiment is constructed like the hydrostirling machine of the first embodiment, but the two hydrostirling units 10 and 20 additionally have a steam generating unit 17, 27, each consisting of a steam generator 17b, 27b, a reservoir 17c, 27c and a return 17d, 27d exists. The steam generators receive their heat entirely or predominantly from the outer wall of the container below the separation point between the hot and cold part of the container and thus contribute to the desired cooling. The generated steam is - preferably as superheated steam (for which an unillustrated additional superheater may be provided) - injected into the turbine tank (reference numeral 100). In this case, instead of a pressure equalization between the turbine tank and the tank of the second hydrostirling unit, the turbine tank is pressed with steam such that the In FIG. 10 shown state instead of in FIG. 8 shown state is achieved. If cold water then flows from the first hydrostirling unit into the turbine tank, the superheated steam condenses immediately and an even higher pressure gradient is available.

In order to ensure that the working fluid quantity, that is to say the amount of water in the hydrostirling machine, remains constant, water must be withdrawn continuously or at intervals over the return line 17d. Since the amount of injected superheated steam can be very small, it is sufficient to remove water at certain intervals.

The FIG. 11 shows a fourth embodiment in one of FIG. 1 corresponding representation. No steam injection is shown, but it may be present.

The difference from the embodiments shown so far is that in addition to the working fluid return lines 70, 74 bypass lines 71, 75 are provided, which the turbine tank 32 and the containers 11, 21 of the hydrostirling units 20, 30, bypassing the pump 73, 76 and the Connect lifting equipment together. In each bypass line, a check valve is provided. One could also call these bypass lines as second working fluid return lines. As long as the machine is operated at a low frequency (for example, one cycle per minute) and thus at maximum efficiency, the bypass lines can usually remain inoperative. However, if the machine with higher power and thus with a larger throughput of working fluid to be operated, it may be useful that a portion of the turbine container 32 in the respective container 11, 21 of the respective Hydrostirling unit 10, 20 returning working fluid to the pump and the lifting device bypasses. This is the purpose of the bypass lines 71, 75.

Finally, it should be noted that in the FIGS. 5 to 11 the lifting devices are not shown in detail, but it is preferable that these as with respect to the FIGS. 2 to 4 are formed described. In principle, however, it is also conceivable to use lifting devices which are independent of the working fluid circuit.

The FIG. 12 shows one way in which the thermal separation between the upper tank area and the lower tank area during the phase in which the displacer 13 is in its upper end position, can be improved. For this purpose, the inner wall of the shell of the container 11 has a downwardly facing step and the cylinder jacket 14 a stop. Furthermore, a, preferably carried by the stage, seal 11c may be provided. As illustrated, the step is preferably formed by the container 11 consisting of an upper container part 11a and a lower container part 11b flanged to the upper container part 11a, the upper container part 11a having a smaller inner diameter than the lower container part. The stop of the cylinder jacket 14 is preferably formed as a bead 14a. Step and stop are arranged so that the stop abuts the step or the seal 14a when the displacer piston 13 is in its upper end position (see, for example FIG. 10 ). This ensures that no cold water in the gap between the cylinder jacket 14 and the inside of the upper container part 11a can rise to the top, when the Displacer is in its upper end position, whereby the thermal decoupling is improved. Of course, the described measure can be provided in both hydrostirling units 10, 20.

LIST OF REFERENCE NUMBERS

10

first hydrostirling unit

11

container

11a

upper container part

11b

lower container part

11c

poetry

12

heating head

13

displacer

13a

insulation

13b

regenerator

14

cylinder surface

14a

Beading

16

lifter

17

Steam generation unit

17b

steam generator

17c

reservoir

17d

returns

20

second hydrostirling unit

21

container

22

heating head

23

displacer

23a

insulation

23b

regenerator

24

cylinder surface

26

lifter

27

Steam generating unit

27b

steam generator

37c

reservoir

37d

returns

30

turbine unit

32

turbine container

34

turbine

36

generator

40

Pressure cylinder

42

Pressure gas line

50

first working fluid line

52

check valve

56

control nozzle

60

second working fluid line

62

check valve

66

control nozzle

70

first working fluid return

71

first bypass line

72

check valve

73

pump

74

second working fluid return

75

second bypass line

76

pump

78

check valve

90

Buoyancy of the first hydrostirling unit

91

bolt

92

static riser

94

movable riser

95

opening

96

camp

98

deflector

100

steam injection

110

Buoyancy of the second hydrostirling unit

111

bolt

Claims (15)

1. Hydro Stirling engine comprising:

   at least two hydro Stirling units (10, 20), which in each case comprise a container (11, 21) configured as a standing cylinder, wherein for each container (11, 21) a heating device for heating an upper region or an upper end region is provided, and wherein an axially movable and controllable displacement piston unit with a displacement piston (13, 23) comprising a regenerator (13b, 23b) is arranged in the interior of each container (11, 21),

   an energy converter unit, and

   a common working fluid circuit, which has, for each hydro Stirling unit, at least one working fluid line (50, 60), which connects the hydro Stirling unit to the energy converter unit,

   characterised in

   that the energy converter unit is a turbine unit (30), which has a turbine vessel (32) and a turbine wheel (34) arranged in this turbine vessel (32),

   that the working fluid lines (50, 60) extend between the hydro Stirling units (10, 20) and the turbine unit (30) in such a way that working fluid, which flows from a hydro Stirling unit (10, 20) to the turbine unit (30), firstly impinges on the turbine wheel (34) and then falls into a region of the turbine vessel (32) below the turbine wheel (34),

   that the working fluid circuit comprises for each hydro Stirling unit (10, 20) at least one working fluid return line (70, 74), which connects the turbine unit (30) to the hydro Stirling unit (10, 20), and

   that each displacement piston unit comprises a cylinder shell (14, 24) extending downwardly from the displacement piston (13, 23), wherein the outer surface of the cylinder shell is substantially aligned with the outer surface of the displacement piston (13, 23).
2. Hydro Stirling engine according to claim 1, characterised in that the lifting force of the displacement piston unit is in each case greater than its force due to weight, in such a way that the regenerator (13b, 23b) floats on the working fluid.
3. Hydro Stirling engine according to claim 2, characterised in that each displacement piston comprises insulation (13a, 23a) surrounding the regenerator (13b, 23b), the specific weight of which is less than the specific weight of the working fluid, and wherein the insulation extends over the lower end of the regenerator (13b, 23b) such that a lower section of the insulation (13a, 23a) is immersed into the working fluid.
4. Hydro Stirling engine according to any one of the preceding claims, characterised in that each displacement piston unit comprises a lifting body (90, 110) connected to the displacement piston (13, 23).
5. Hydro Stirling engine according to claim 4, characterised in that the cylinder shell (14, 24) forms at least a part of the connection between the displacement piston (13, 23) and the lifting body (90, 110).
6. Hydro Stirling engine according to any one of the preceding claims, characterised in that the containers (11, 21) comprise on their inner side in each case a downwards facing step (11a), and the cylinder shells (13, 23) in each case comprise a stop for engaging in contact with this step (11a).
7. Hydro Stirling engine according to any one of the preceding claims, characterised in that, in order to control the displacement pistons (13, 23), a static riser pipe (92) connected to the working fluid return line (70, 74), and a movable riser pipe (94) arranged in the static riser pipe (92) in the form of a piston, are provided in the interior of the container (11, 21) of each hydro Stirling unit.
8. Hydro Stirling engine according to claim 7, characterised in that the static riser pipe (92) extends through the lifting body (90).
9. Hydro Stirling engine according to any one of claims 7 or 8, characterised in that the movable riser pipe (94) exhibits an upwards pointing opening (95) at its upper end.
10. Hydro Stirling engine according to any one of claims 7 or 9, characterised in that the displacement piston (13) is not securely connected to the movable riser pipe (94).
11. Hydro Stirling engine according to claim 9 and claim 10, characterised in that the displacement piston (13) comprises a deflector (98) pointing towards the opening (95).
12. Hydro Stirling engine according to any one of the preceding claims, characterised in that the turbine vessel (32) comprises a steam injector (100).
13. Hydro Stirling engine according to claim 12, characterised in that the steam generators (17b, 27b) assigned to the steam injector (100) are in contact in each case with the outer wall of a container (11, 21) of a hydro Stirling unit (10, 20).
14. Hydro Stirling engine according to any one of the preceding claims, characterised in that exactly two hydro Stirling units (10, 20) are provided, in which in each case a Stirling circuit process runs.
15. Hydro Stirling engine according to any one of the preceding claims, characterised in that the turbine wheel (34) is a Pelton turbine wheel.

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