WO2008022705A1

WO2008022705A1 - Method and apparatus for conversion of combustion heat energy to mechanical energy

Info

Publication number: WO2008022705A1
Application number: PCT/EP2007/006890
Authority: WO
Inventors: Peter Kreuter
Original assignee: Meta Motoren- Und Energie-Technik Gmbh
Priority date: 2006-08-25
Filing date: 2007-08-03
Publication date: 2008-02-28
Also published as: DE102006039924A1; DE102006039924B4; EP2054607A1

Abstract

In an apparatus for conversion of combustion heat energy to mechanical energy, having a compressor cylinder (16) with a compressor piston (12), an inlet valve (54) and an outlet overflow valve (56), a working cylinder (18) with a working piston (14), an inlet overflow valve (58) and an outlet valve (60), a primary heat exchanger (22), which is arranged between the overflow valves and supplies heat contained in the combustion gases of a burner (38) to the primary heat exchanger from the compressed air supplied to the compressor cylinder, a secondary heat exchanger (44) for heating air emerging from the working cylinder (18), by means of the exhaust gas leaving the primary heat exchanger (22), which heated air is supplied to the burner, with the pistons (12, 14) being connected to one another such that the compressor piston is moved by the working piston and at least a portion of the compressed hot air, which is not consumed during this process and is supplied to the working piston by at least largely adiabetic expansion of the compressed hot air which is supplied to the working cylinder from the primary heat exchanger, can be tapped off as mechanical energy, a line which originates from the outlet valve (60) of the working cylinder (18) leads directly to an inlet of the secondary heat exchanger (44), and an exhaust-gas outlet from the primary heat exchanger (22) is connected directly via an exhaust-gas line to an exhaust-gas inlet of the secondary heat exchanger (44).

Description

Method and apparatus for converting combustion heat energy into mechanical energy

The invention relates to a method and apparatus for converting combustion heat energy into mechanical energy.

Internal combustion piston internal combustion engines, i. Combustion within a working space bounded by the reciprocating piston and cylinder has, among other things, the following characteristics:

- Due to the cyclical combustion, the combustion process must be started and stopped at short intervals, whereby it runs essentially unsteady, is difficult to control, leads to increased pollutant formation in the exhaust gas and the efficiency is impaired.

- The fuels must be in liquid or gaseous form.

In order to meet the aforementioned difficulties, it is known to continuously combust fuel outside a cylinder in a combustion chamber and to convert the heat generated in the cylinder by means of the piston into mechanical work.

From DE 41 20 167 C2 a method and a device according to the preambles of the appended independent claims are known. According to the cited document, the combustion gas of the burner or its exhaust gas, after flowing through the primary heat exchanger, is guided along the wall of the working cylinder and only subsequently supplied to an exhaust gas inlet of the secondary heat exchanger. The exiting the working cylinder air is supplied downstream of the secondary heat exchanger fresh air, which has flowed through the secondary heat exchanger. In this way, a portion of the combustion heat produced in the burner for external heating of the working in the working cylinder compressed and hot gas is used and is not available for heating the combustion air, which is thermodynamically unfavorable. Furthermore, in a pressure accumulator downstream of the loading cylinder stored compressed fresh air under high pressure by brief Opening a primary heat exchanger upstream valve are injected into this, resulting in flow losses, which reduce the efficiency.

In DE 40 42 305 Al an internal combustion engine is described which has a respective provided with an inlet valve and an exhaust valve compression cylinder and expansion cylinder, in which work on a common crankshaft piston. The outlet of the compression cylinder is connected via a connecting line to the inlet of the expansion cylinder, the outlet of which is connected via a return line to the inlet of the compression cylinder. The connecting line passes through a heat exchanger in which fluid flowing from the compression cylinder to the expansion cylinder is heated by means of a burner arranged in the heat exchanger, to which fresh air and fuel are supplied. The fresh air supplied to the burner and the fuel are heated by the exhaust gas leaving the heat exchanger.

From US 4,120,161 an open-cycle external combustion reciprocating engine is known having compression cylinders separated by larger power and expansion cylinders, respectively. The heat of the compressed air is supplied to an air heater, wherein compressed air does not mix with the hot gases. For recovering the heat contained in the combustion gases, a heat exchanger is provided.

The invention has the object of developing a generic method or a generic device such that combustion heat energy can be converted into mechanical energy with high efficiency.

The method of the invention part of the invention is solved by a method according to claim 1.

The dependent claims back to claim 1 indicate advantageous embodiments and refinements of the method according to the invention.

The device-directed part of the invention problem is solved by the independent device claim. The claims referring back to this independent device claim characterize advantageous embodiments and further developments of the device according to the invention.

The invention is explained below with reference to schematic drawings, for example, and with further details.

In the figures represent:

1 shows a schematic view of an entire device according to the invention, FIG. 2 shows a side view of a primary heat exchanger with cylinder units,

3 is a plan view of the arrangement of FIG. 2,

4 shows a schematic view of the basic structure of a heat exchanger according to the invention,

5 shows an arrangement of an overflow valve, FIG. 6 shows a further arrangement of an overflow valve,

7: the enlarged section Z of Fig. 6,

8 shows another possible arrangement of a spill valve,

9 shows a modified embodiment of an overflow valve,

10 shows a further possibility of forming overflow valves, and FIG. 11 shows the cutout designated Z in FIG.

According to FIG. 1, a crankshaft 10 of a reciprocating engine is connected via a connecting rod to a compressor piston 12 and a working piston 14. The compressor piston 12 operates in a compressor cylinder 16, the working piston operates in a working cylinder 18. The crankshaft 10 serves to drive a working machine 20, such as a generator, a pump, etc. The two cylinders are advantageously separated, the wall of the compressor cylinder 16 advantageously cooled is and the wall of the working cylinder 18 is thermally insulating. Also, the working piston 14 is advantageously designed such that little heat from the working space of the working cylinder 18 in the connecting rod of the working piston reached. Immediately above the reciprocating engine, a primary heat exchanger 22 is arranged, which has an exhaust gas inlet 24 and an exhaust gas outlet 26 and further comprises an air inlet 28 and an air outlet 30, whose function will be explained later.

A burner device 32 includes an air supply port 34, a fuel supply port 36, a burner 38, and a combustion gas exhaust port 40 connected to the exhaust gas inlet 24 of the primary heat exchanger 22.

The exhaust gas outlet 26 of the primary heat exchanger 22 is connected to an exhaust gas inlet 42 of a secondary heat exchanger 44 whose exhaust gas outlet 46 is connected to an exhaust gas turbine 48 which drives a compressor turbine 50 which is connected to an air inlet 52 of the compressor cylinder 16.

As can be seen from FIGS. 2 and 3, an inlet valve 54 operates in the air inlet 52 of the compressor cylinder 16. The connection to the primary heat exchanger 22 or its air inlet 28 takes place via an outlet or outlet overflow valve 56. The connection from the air outlet 30 of the primary heat exchanger 22 to the Working cylinder 18 takes place via an inlet valve or inlet overflow valve 58. An outlet valve 60 operates in the air outlet 30 of the working cylinder 18.

The function of the described arrangement is as follows:

Fresh air pre-compressed by the compressor turbine 50 is drawn in by the compressor piston 12 during its downward movement and open inlet valve 54 and, after closing the inlet valve, is underdiaphragm-compressed until the outlet overflow valve 56 is opened. This compression occurs because of the preferably existing cooling of the wall of the compressor cylinder 16 with high compressor efficiency.

Upon opening the outlet spill valve 56, the compressor piston 12 pushes and compresses the compressed fresh air into the primary heat exchanger 22 until the exhaust spill valve 56 closes. In order for the compression to continue with the outlet spill valve 56 open, the volume available for the compressed air is in the primary heat exchanger 22 (Inlet overflow valve 58 closed) advantageously smaller or significantly smaller than the stroke volume of the compressor cylinder 16th

After closing the Auslassüberströmventils 56, the interior of the primary heat exchanger 22 and the compression space of the compressor cylinder 16 are separated from each other.

The primary heat exchanger 22 is continuously heated by the combustion gas or exhaust gas of the burner 38. The burner 38 is advantageously arranged as close as possible to the primary heat exchanger 22 or integrated in this. Due to the continuous heating pressure and temperature of the air in the primary heat exchanger 22 isochoric increased.

After opening the inlet overflow valve 58, the isochorically heated and compressed air flows into the working space of the working piston 14 and performs work on the working piston 14 by adiabatic expansion (thermal isolation of the working cylinder 18), whereby the compressor piston 12 and the working machine 20 are driven.

During all or at least a substantial part of the adiabatic expansion there is no spatial connection between the compressed and heated air expanding out of the primary heat exchanger and the compressor chamber of the compressor cylinder 16.

After closing the inlet overflow valve 58, the primary heat exchanger 22 and the working space of the working cylinder 18 are separated from each other. The working piston 14 carries out a further prolonged adiabatic expansion. Advantageously, the stroke volume of the working cylinder 18 is greater than that of the compressor cylinder 16th

Then, the power piston 14 pushes the air with the exhaust valve 60 open to the secondary heat exchanger 44, where the air is heated by the exhaust gas of the burner 38 and from which the heated air of the air supply port 34 of the burner device 32 is supplied. In the continuous Brennereinrichrung 32 any fuel can be burned, which can be burned with air, if necessary under suitable turbulence or otherwise, such as solid fuels, such as coal; Liquid fuels, such as fuel oil, or gaseous fuels, such as propane, natural gas, etc. The energy still contained in the exhaust gas after flowing through the secondary heat exchanger 44 is used in the exhaust gas turbine 48 and can be used in further downstream units with a lower process energy requirement.

Typical timing of the valves, based on the TDC of the compressor piston 12 are the following:

Inlet valve opens: Inlet valve closes: Outlet spill valve opens: Outlet spill valve closes: Inlet spill valve opens: Inlet spill valve closes: Outlet valve opens: Exhaust valve closes

The valve actuations can be done in any known manner, for example mechanically via the crankshaft with phaser in the valve train; electromagnetically, hydraulically, etc.

To extend the residence time of the compressed air in the primary heat exchanger 22 this is advantageously, as shown in FIG. 3, constructed with two columns and contains two heat exchanger units 22], 22 ₂ , each with its own overflow 56j, 56 ₂ and 58), 58 _second are connected to the compressor cylinder or the working cylinder. By alternately opening the overflow valves, the heat exchanger units 22 ₁ and 22 ₂ alternately filled and emptied, so that for an effective heat exchange or for an effective heating long residence times are achieved even at high speeds. It can also be provided more than two heat exchanger units. The loading or emptying of the heat exchanger units is advantageously carried out directly by the fact that a plurality of overflow valves are provided. Alternatively, an overflow valve can also be provided in each case and the compressed air flowing out of the compressor cylinder can be divided by a distributor valve onto the various heat exchanger units and be discharged from the heat exchanger units to the inlet overflow valve 58 via a further distributor valve.

It is understood that the reciprocating engine may be provided with a plurality of intake valves 54 and exhaust valves 60 per cylinder. Furthermore, it is understood that a plurality of working cylinders / compressor cylinder units can be provided, the heat exchanger is continuously heated by a common burner device 32 and the exhaust gas heat is used continuously in a common secondary heat exchanger 44.

Figure 4 shows a possibility for improving the efficiency of a heat exchanger, especially the primary heat exchanger, which is shown by way of example. Via the inlet 28 to be heated fluid is supplied, which flows through the outlet. Through the inlet 24 hot medium, for example, exhaust gas is supplied, whose energy is used to heat the medium flowing through the inlet and outlet 30 and flows through the outlet 26. From the outlet 26 to the inlet 24 performs a return line 62, in which a pump 64 operates whose flow rate determines the amount of recycled heating medium. The return rate may additionally be determined by means of throttle valves 66 and 68, which are arranged at the inlet 24 and outlet 26, respectively upstream and downstream of the return line 62. The efficiency of the heat exchanger can be improved in this way due to the longer residence time of the heating medium. The increased average flow rate as well as a reduction in the temperature difference between the inlet and outlet, whereby the average process temperature can be increased, cause a further improvement in the efficiency of the heat exchanger. The exhaust gas temperature of the burner can be increased because only by the mixture before the heat exchanger, the inlet temperature of the heating medium, which is limited on the material side, is set. A similar technique can be used to increase the residence time of the medium to be heated.

The Applicant reserves the right to claim protection for the above-described subject matter regardless of its use in the described machine.

It is advantageous to actuate overflow valves in such a way that no pressure difference is effective at the opening of the outlet overflow valve 56, ie the same pressure prevails at the time of opening in the primary heat exchanger 22 as in the compressor chamber of the compressor cylinder 16. It is also advantageous to supply the inlet overflow valve 58 at one time open, to which there is no pressure difference. With the opening times described is achieved that no unnecessarily high proportion of heat energy is converted into flow energy. For a high efficiency of the described conversion of combustion heat energy into mechanical energy not only a high efficiency of heat transfer in the primary heat exchanger is necessary, but also a high compression of the funded from the compressor piston in the primary heat exchanger gas and the best possible use of the contained in the high-pressure and heated gas Energy for moving the working piston. The connection volumes between the compressor cylinder and the primary heat exchanger and the primary heat exchanger and the working cylinder in this regard are dead spaces whose volumes should be as small as possible, which makes particular special designs of the overflow valves advantageous.

Due to the pressure gradient between the cylinders and the primary heat exchanger, the overflow valves to and from the heat exchanger are opposite to conventional valve trains, in which the valves open in the direction of the cylinder chamber, from the primary heat exchanger to the respective cylinder. The high operating temperatures that occur make demands on the valves and their seals, which are met by special materials and / or cooling of the valves or seat rings.

In the following, advantageous overflow valve constructions will be explained using the example of the outlet overflow valve 56.

According to FIG. 5, the overflow valve 56, which is opened in the direction of the arrow when in tension, is arranged at an angle to the cylinder axis. As can be seen, the volume of the connecting channel from the working cylinder 18 to the primary heat exchanger 22 is very small. For improved compression of the working piston 14 has a dome 70, so that at the top dead center of the piston, the compression space is almost completely filled by the piston. The compressor piston may be similarly provided with a dome. If the spill valve 56 were opened into the cylinder, the piston could not be moved to a correspondingly high top dead center, thereby increasing the dead space between the compressor cylinder 16 and the primary heat exchanger 22.

FIG. 6 shows a modified embodiment in comparison to FIG. 5, in which the overflow valve 56 is likewise opened upwards, but is arranged parallel to the inlet valve 54. There at In this embodiment, the cylinder head or the inside of the top wall of the cylinder is flat, the compressor piston 12 is provided with no dome. FIG. 7 shows an enlarged view of the detail marked Z in FIG.

In the embodiment according to FIG. 8, the overflow valve 56 is arranged horizontally; in this embodiment, the piston 12 again has a dome 70.

In the embodiment according to FIG. 9, the overflow valve 56 opens directly into the heat exchanger 22. The overflow valve 56 may be formed as a pressure valve. The piston 12 may be provided with a dome, not shown, which dips into the outlet channel.

In the embodiment according to FIG. 10, a plurality of overflow valves 56 are arranged horizontally and designed as pressure valves. In order to keep the damaged volume as small as possible, many small valves with short valve lift can be used, which can be designed as a series and / or parallel connection. The piston 12 may have a dome with projections which protrude into the channels associated with the individual overflow valves.

FIG. 11 shows a plan view of an embodiment of FIG. 12 in which two independently operable groups of outlet spill valves 56 are provided, such as are useful when the primary heat exchanger 22 is divided into two units 22 ₁ and 22 ₂ . In the illustrated example, two inlet valves 54 are provided, the openings of which are visible in FIG. It is understood that the intake valves can be operated in unison while the spill valves are alternately actuated to increase the residence times of the gas in the primary heat exchanger.

The method according to the invention and the device according to the invention operated according to the method can be used for a wide variety of uses, for example for stationary power plants, for large machines that are stationary or, for example, operated in ships, for combined heat and power plants or for truck engines. The achievable efficiencies far exceed those of conventional internal combustion engines or machines with continuous external external combustion. As a working medium not only air can be used, but any gas that can be burned in the burner device 32, for example, hydrogen, methane, etc. In this case, oxygen or air is supplied via the Brennstoffzutuhröffnung 36.

The compressor turbine 50 used for pre-compression of the gas may be replaced by a supercharger driven by the crankshaft or in addition to such a supercharger.

To optimize the combustion air ratio in the burner device 32 may optionally be a fresh air or fresh gas supply via a dotted recorded bypass line, which branches off between the compressor turbine 50 and the air inlet 52 and leads into the line connecting the outlet 30 of the working cylinder 18 with the secondary heat exchanger 44 , About this bypass line 72, in which a throttle valve may be arranged, the fresh air supply to the burner 38 can be increased. Additionally or alternatively, via a further, preferably likewise controllable bypass line 74, which branches off upstream of the gas inlet of the secondary heat exchanger 44 and opens into the exhaust pipe downstream of the secondary heat exchanger 44, the air supplied to the burner 38 is reduced. This allows the enthalpy of the process gas to be fed either completely to combustion or partly to the exhaust turbine.

It is understood that the pre-compression of the air supplied to the compressor cylinder is not mandatory.

LIST OF REFERENCE NUMBERS

10 crankshaft

12 compressor pistons

14 working pistons

16 compressor cylinders

18 working cylinders

20 work machine

22 primary heat exchanger

24 exhaust inlet

26 exhaust outlet

28 gas inlet

30 gas outlet

32 burner device

34 air supply opening

36 fuel supply port

38 burners

40 combustion gas outlet

42 exhaust inlet

44 Secondary heat exchanger

46 exhaust outlet

48 exhaust gas turbine

50 compressor turbine

52 air intake

54 inlet valve

56 outlet spill valve

58 inlet overflow valve

60 outlet valve

62 return line

64 pump

66 throttle valve

68 throttle valve Dom bypass line Bypass line

Claims

claims

A method of converting combustion heat energy to mechanical energy, comprising the steps of: passing fresh gas into a compressor (16) for compressing the fresh air;

Passing the compressed air through a primary heat exchanger (22), directing the heated and further compressed gas in a working cylinder (18) in which the hot and compressed gas with a largely adiabatic expansion mechanical energy e-energy to a working cylinder working piston (14) emits - passing the gas leaving the working cylinder to a burner (38), in which the gas is burnt possibly with the addition of fuel with the release of combustion heat energy,

Passing the combustion gas through the primary heat exchanger (22) and passing the exhaust gas leaving the primary heat exchanger through a secondary heat exchanger (44), in which the gas supplied to the burner (38) is heated, wherein the operating piston working in the working cylinder drives the compressor and excess Energy of the working piston is removable as mechanical work, characterized in that a from the outlet valve (60) of the working cylinder (18) outgoing line leads directly to an inlet of the secondary heat exchanger (44) and a Abgasaus- outlet of the primary heat exchanger (22) via an exhaust pipe immediately is connected to an exhaust inlet of the secondary heat exchanger (44).

2. The method according to claim 1, characterized in that - in the connection from the primary heat exchanger (22) to the working cylinder (18) an inlet overflow valve (58) is arranged, which is opened in each case at a time to which there is essentially no pressure difference effective is.

3. The method according to claim 1 or 2, characterized in that the compressor includes a compressor cylinder (16) with therein working compressor piston (12), wherein in the connection from the compressor cylinder to the primary heat exchanger (22) an outlet spill valve (56) is arranged, which is opened in each case at a time at which substantially no pressure difference is effective on it.

4. The method according to claim 3, characterized in that from the compressor cylinder (16) in the primary heat exchanger (22) flowing gas is at least partially compressed with open connection between the compressor cylinder and primary heat exchanger and closed connection between the primary heat exchanger and cylinder.

5. The method according to any one of claims 1 to 4, characterized in that the working piston (14) from the primary heat exchanger (22) exiting gas at the compressor cylinder (16) closed towards primary heat exchanger is moved.

6. The method according to any one of claims 1 to 5, characterized in that the compressor (16) precompressed fresh gas is supplied, wherein the energy required for the pre-compression of the combustion heat energy comes from.

7. The method according to any one of claims 1 to 6, characterized in that a plurality of primary heat exchanger units (22 ₁ , 22 ₂ ) are provided, so that the residence time of the primary heat exchanger supplied gas in the primary heat exchanger can be extended.

8. The method according to any one of claims 1 to 7, characterized in that at least a portion of a respective gas flowing through a heat exchanger flows through this multiple times.

9. The method according to any one of claims 1 to 8, characterized in that at least a portion of the working cylinder (18) to the secondary heat exchanger (44) flowing gas is introduced into the exhaust gas leaving the secondary heat exchanger.

10. The method according to any one of claims 1 to 8, characterized in that at least part of the compressor (16) supplied fresh gas in the from the working cylinder (18) to the secondary heat exchanger (44) flowing gas is introduced.

11. The method according to any one of claims 1 to 10, characterized in that the compressor cylinder air is supplied.

12. An apparatus for converting combustion heat energy to mechanical energy, comprising: a compressor cylinder (16) having a compressor piston (12), an inlet valve (54) and an outlet spill valve (56); a power cylinder (18) having a power piston (14); Inlet overflow valve (58) and an outlet valve (60), - a primary heat exchanger (22) arranged between the overflow valves for

Supplying heat contained in combustion gases of a burner (38) to the primary heat exchanger from the compressor cylinder supplied compressed air, a secondary heat exchanger (44) for heating from the working cylinder (18) exiting air by means of the primary heat exchanger (22) leaving the exhaust gas, which heated air the Burner is supplied, wherein the pistons (12, 14) are interconnected such that the compressor piston is moved by the working piston and at least a portion of the thereby not consumed, the working piston by at least largely adiabatic expansion of the working cylinder from the primary heat exchanger supplied compressed hot Air as mechanical energy can be tapped off, characterized in that one of the exhaust valve (60) of the working cylinder (18) outgoing line leads directly to an inlet of the secondary heat exchanger (44) and an exhaust outlet of the primary heat exchanger (22) via an exhaust pipe un is indirectly connected to an exhaust inlet of the secondary heat exchanger (44).

13. The apparatus according to claim 10, characterized in that the available volume for the compressed air of the primary heat exchanger (22) is smaller than the stroke volume of the compressor cylinder (16).

14. The apparatus of claim 12 or 13, characterized in that upstream of the compressor cylinder (16) is arranged a pre-compressor (50) for pre-compressing the fresh air, is driven by the working piston (14) and / or a downstream of the exhaust gas heat exchanger (44) arranged turbine (48).

15. Device according to one of claims 12 to 14, characterized in that the stroke volume of the compressor cylinder (16) is smaller than that of the working cylinder (18).

16. Device according to one of claims 12 to 15, characterized in that a controllable fresh air bypass line (72) a point upstream of the inlet of the compressor cylinder (16) with a from the outlet of the working cylinder (18) to an air inlet of the secondary därwärmetauschers (44) leading line connects.

17. Device according to one of claims 12 to 16, characterized in that a bypass line (74) connects an air inlet of the secondary heat exchanger (44) with an exhaust gas outlet of the secondary heat exchanger.

18. Device according to one of claims 12 to 17, characterized in that the primary heat exchanger (22) a plurality of heat exchanger units (22 _1; 22 ₂ ), which are selectively connectable to the overflow valves (56, 58).

19. Device according to one of claims 12 to 18, characterized in that at least one of the heat exchangers (22) has a leading from an outlet to an inlet return line (62) in which a pump (64) is arranged, so that at least one Part of the fluid flowing between the inlet and the outlet flows through the heat exchanger several times.

20. Device according to one of claims 12 to 19, characterized in that the volumes of the connections from the primary heat exchanger (22) to the compressor cylinder (16) and to the working cylinder (18) are minimized.

21. Device according to one of claims 12 to 20, characterized in that at least one of the overflow valves (56, 58) is formed by a poppet valve, which opens to the primary heat exchanger (22) out.

22. Device according to one of claims 12 to 21, characterized in that the contour of the piston (12, 14) is adapted to the cylinder heads.

23. Device according to one of claims 12 to 22, characterized in that the working cylinder (18) heat-insulated and / or the compressor cylinder (16) is cooled.

24. Device according to one of claims 12 to 23, characterized by a valve actuating device which opens the overflow valves (56, 58) at times to which applied to the overflow substantially no pressure difference.