WO2019206355A1

WO2019206355A1 - Method for operating a gas expansion engine by means of a gas

Info

Publication number: WO2019206355A1
Application number: PCT/DE2019/000112
Authority: WO
Inventors: Franklin Schmidt
Original assignee: MCCLENAGHAN, Kerstin
Priority date: 2018-04-28
Filing date: 2019-04-24
Publication date: 2019-10-31
Also published as: EP3788238B1; EP3788238A1

Abstract

The main feature of the invention is an energy method for using low-grade thermal heat sources, preferably from natural ambient temperatures, such as in air, water or the ground, to generate, by heat exchange, usable environmental energy for carrying out useful mechanical or hydraulic work and to transform said energy in an environmentally friendly manner using a non-critical CO2 working cycle process in gas expansion engines with integrated condensation work, for mobile and static drive systems.

Description

DESCRIPTION

Method for operating a gas expansion engine by a gas

The invention relates to a method for operating a gas expansion engine by a gas, which is preferably conducted in a closed circuit, according to claim 1.

In the context of the invention, carbon dioxide (CO 2), which can transport a large amount of heat energy and can be changed in volume by pressure and / or temperature change with mass transfer phases, from gaseous to liquid and solid and vice versa, is used as gas to be preferred. In addition, C02 is neither explosive nor flammable in the event of damage and environmentally neutral in recycling.

The C02 two-phase range below the critical point spans the temperature of about plus 31 ° C and pressure of 73.8 bar at the critical point to the triple point at about minus 56.6 ° C and 5.2 bar. At the triple point there are 3 material transitions from gaseous to liquid or in solid form, with further fluid supercooling and pressure reduction only as "dry ice". Above 32 ° C and above 74bar, the critical point to the transcritical CO 2 fluid is exceeded and the CO 2 remains gaseous in the state of aggregation.

It is well known to operate gas expansion engines with CO 2 gas from pressure cylinders. The mechanical work delivered by a gas expansion engine originates in the adiabatic expansion case from the enthalpy stored in the C02 gas. However, the disadvantage here is the loss of CO 2 as an emission gas into the atmosphere.

Single-stage or multi-stage gas expansion engines that operate in a closed working process with reciprocating expander or on the free piston principle in the right of running critical point cooling processes and instead of expansion valve gas relaxation processes mechanical work for the subsequent

confirmation copy Transcritical compaction work to generate, are also state of the art and described for example in DE 199 55 554 A1.

A disadvantage of the transcritical process management with mechanical use of the gas relaxation is the subsequent high compressor work for gas compression, which reduces the injected useful work and provides no significant useful energy for other fuel consumption systems and heat exchange over the critical punk with at least 32 ° C, largely the thermal energy utilization low thermal conversion. exclude world temperatures.

Proceeding from this, the object of the invention is to avoid the disadvantages described above.

Disclosure of the invention

The invention provides a regenerative (closed) circuit for the gas below the critical point of the gas, which is formed in particular by CO 2. By means of the two-phase fluid with gas and liquid, the heat exchange should take place with low-thermal environmental energies and be usable as environmentally neutral drive energies in gas expansion motors with integrated condensation work.

Here, a method for operating a, for example, two-stroke gas expansion engine by a gas, preferably proposed by C02, which comprises a at least one inlet valve and an exhaust valve having working cylinder and between a first piston reversal point and a second piston reversal point in the working cylinder in reciprocating motion Piston strokes executing reciprocating piston which limits an expansion space and the size of the expansion space changed by its reciprocating motion, the method comprises at least one cycle of at least the following steps: It is a power stroke by introducing an inlet volume of the gas in a saturated state via the open inlet valve in the expansion space and caused by an expansion of the inlet volume resulting movement of the reciprocating piston, which moves under enlargement of the expansion space in the direction of the first piston reversal point, wherein before the first piston reversal point through the Reciprocating piston is reached, the gas is introduced in the liquefied state in the expansion space, and then a compression stroke is carried out by a movement of the reciprocating piston in the direction of the second piston reversal point (OT, reducing the expansion space and compressing the inlet volume and the gas in the liquefied state If the gas inlet volume liquefies before the second piston reversal point is reached by the reciprocating piston, at least a portion of the gas in the expansion space is displaced from the expansion space via the outlet valve into a depot in the liquefied state by the movement of the reciprocating piston toward the second piston reversal point and then, via a heat exchanger, an isobaric transfer of heat to gas discharged from the depot is carried out in a liquefied state until it is vaporized and available as a gas in a saturated state.

Saturated gas, which is produced by the isobaric transfer of heat to the gas in the liquefied state in the heat exchanger, is preferably used for the inlet volume of saturated gas which is introduced into the expansion space via the inlet valve.

According to a further development, gas in the liquefied state, which is introduced into the expansion space, is used in the liquefied state from the depot for the gas.

For example, the gas in the liquefied state is injected into the expansion space under pressure.

Further preferably, after a closing of the inlet valve, the expansion of the inlet volume begins.

According to a further measure, the displacement of the at least part of the gas in the liquefied state from the expansion space can take place by means of the pressure built up during the compression stroke in the expansion space.

In particular, the exhaust valve is controlled by the pressure in the expansion space. Preferably, the outlet valve is designed such that it can be brought by the pressure in the expansion space from a closed position to an open position or spent.

According to a development, the expansion of the inlet volume of the gas in a saturated state with reduction of pressure and / or temperature of the gas to the triple point of the gas takes place when the first piston reversal point is reached.

Also, the liquefied gas can be introduced from the depot into the expansion space essentially under the conditions prevailing in the triple point of the gas and cooled down to the boiling point during the working cycle under a two-phase change as an isobaric wet gas / liquid fluid.

According to a further measure, in the course of the compression stroke, an isothermal and isobaric wet gas compression by the reciprocating piston in the gas-liquid equilibrium with condensation above the boiling line may end before the second piston reversal point is reached by the reciprocating piston.

Also, the reciprocating drive a crank drive or a linear drive.

Also, the thermodynamic state of the gas can always be kept below the critical point of the gas in a subcritical state.

The gas used is preferably exclusively CO 2 and the gas in the liquid state is formed by liquid CO 2.

In other words, the invention preferably proposes an energetic C02 two-phase work process process below the critical CO 2 point with gas and liquid phases which preferably generate regenerative environmental energies from air, water or ground temperatures and into mobile or static C02 gas expansion engines With integrated condensation as environmentally neutral drive energy, transform directly into mechanical or hydraulic work.

An embodiment will be described in the accompanying drawings.

Figures 1 to 3 show an example of a C02 gas expansion engine, in which the inventive method is carried out in a preferred embodiment. The method is used to operate the C02 gas expansion engine preferably in a two-stroke process, below the critical CO 2 point with external heat absorption and preferably in a cycle.

The C02 gas expansion engine of FIG. 1 includes a power cylinder 1 in which a reciprocating piston 2 reciprocates along a piston stroke 10 between a lower piston reversal point or bottom dead center 14, BDC and a second or top piston reversal point or top dead center 17, OT is. As a result, an expansion space 13 within the working cylinder 1 is increased or decreased. The working cylinder 1 has an inlet valve 7 and an outlet valve 6. The depot 3 is provided for receiving gas in the liquefied state 4, which may also be referred to as saturated or liquid condensate, and is in the direction of circulation of the C02 gas expansion engine via a depot 3 and a downstream Circulation guided in the heat exchanger 5. After preferably isobaric absorption of heat in the heat exchanger 5, the CO 2 leaves the outlet of the heat exchanger 5 in a saturated state, which then the expansion space 13 is provided with a partial filling 9 of CO 2 in a saturated gas state.

The inlet valve 7 is controlled, for example, as a function of pressure and / or temperature, and initiates an expansive working cycle of the CO 2 gas expansion motor as far as the lower piston reversal point 14, UT, essentially up to the triple point of the CO 2.

Fig. 2 shows the expansion in the expansion chamber 13 in descending reciprocating piston 2, shortly before reaching the lower piston reversal point 14, wherein by means of an example pressure-controlled injection valve 1 1 an injection of CO 2 in the liquefied state 12 from the beispielswesie pressure-loading depot 3 substantially below triple point temperature in the expansion room 13.

3 shows the CO 2 gas expansion engine during an isothermal wet gas compression stroke of the CO 2 up to the upper piston reversal point 17, OT upward reciprocating piston 2 with condensate precipitation and condensate displacement via the outlet valve 6 under condensate outlet 16 into the depot 3 and absorption of heat in the heat exchanger. 5 FIG. 4 shows a diagram, not to scale, for the CO 2 in which the entropy s is plotted on the X axis and the temperature T of the CO 2 in Kelvin is plotted on the Y axis. The diagram exemplifies the states which the CO 2 occupies in the course of the process, whereby the states of the CO 2 are always below the critical point (KP) to before the triple point line (TK) in the subcritical region.

In this case, in FIG. 4

- The dashed line between the points 1 and 2 a hydraulic pressure build-up in the condensate;

- the dashed line between points 2 and 3, a supply of heat of the CO 2 in the liquid region with gas in a saturated state to the dew line;

the dashed line between points 3 and 4 is an isenthalpic expansion of the CO 2 up to, for example, 5.6 bar in the wet gas region;

the dashed line between points 4 and 0 indicates the state of the CO 2 as a wet gas / liquid medium with the reciprocating piston 2 at the first piston reversal point 14, UT;

the dashed line between points 0 and 1 is an isobaric wet-steam compression stroke and condensate precipitation.

5 does not show to scale a diagram in which the temperature T in Kelvin is plotted on the X-axis and the pressure of the CO 2 is plotted on the Y-axis. The diagram illustrates, by way of example, the thermodynamic pressure and temperature profile during the injection of condensate from the depot 3 with two-phase transition into a wet gas expanded in the working cylinder 1 close to the triple point.

Here, in FIG. 5

- point 1 the injection pressure of the CO 2 (about 60 bar) and the temperature of the CO 2 (about 220 K);

the course between points 1 and 2 the pressure reduction and the lowering of the injection temperature with phase transition; the course between points 2 and 3 a two-phase heat exchange with the CO 2 in the liquid state;

Point 3 is the final temperature of the C02 at the Siedeline

The process is conducted in a closed CO 2 working group with integrated heat exchanger 5. With the opening of the inlet valve 7, a pressurized, saturated CO 2 gas, via pressure and / or temperature control, flows into the working cylinder 1 as a limited inflow volume 8 via the descending reciprocating piston 2. After closing the inlet valve 7, the inflow volume expands 8 of the C02 working on the reciprocating piston 2 to the first or lower piston reversal point 14, UT to near C02 triple point in the wet gas area (Fig. 4, pt. 2 -3).

Before reaching the lower piston reversal point 14, UT by the reciprocating piston 2, the injection of the CO 2 in the liquefied state 12 takes place at substantially triple point temperature from the pressure-loading depot 3 into the relaxed wet gas environment (FIG. 2). At a high rate of entry into the expanded wet gas, thermodynamically the pressure and temperature are lowered (FIG. 5, sections 1-2) in the injected CO 2 12. The changing transition of the injection of CO 2 into liquefied state 12 with two-phase heat exchange (FIG. Pkte 2-3) over the solid area into the wet gas, space filling in the working cylinder 1 and in the expansion space 10 subtle aerosols, which cause a heterogeneous two-phase environment of aerosols and wet gas at the Siedeline (Fig. 4, Pkte 0-1).

With increasing compression in the working cylinder 1 by the reciprocating piston 2, countercurrent to neutralizing microcavitations with isothermal wet gas condensation continuously occur in the aerosol wet gas environment, the CO 2 forming a hydraulic fluid or liquefied CO 2 before the upper or second piston reversal point 17,.

With further piston stroke to the upper or second piston reversal point 17, TDC and hydraulic pressure build-up takes place via the counter-pressure from the depot 3 acted upon and opening exhaust valve 6 a condensate displacement 15 and thus a hydraulic condensate outlet 16 in the depot 3. via a gas side Pressure compensation with phase transition of the CO 2 in the heat exchanger 5 for a New cycle of the process or work process, pressure surges and external process losses are compensated without further pressure levels to the inlet valve.

The advantage of the invention is that the energetic utilization of low thermal heat energy via two-phase gas expansion motors, preferably from ambient temperatures in air, water and / or earth, by means of subcritical work process management new environmentally neutral and regenerative energy potentials for mobile and static propulsion systems almost anywhere and at all Makes time available independently.

Bezuqszahlenliste

1 working cylinder

2 reciprocating pistons

3 depot

4 condensate, gas in liquefied state

5 heat exchangers

6 exhaust valve

7 inlet valve

8 entry volumes

9 partial filling

10 piston stroke

1 1 injection valve

12 injected condensate, injected gas in liquefied state

13 first piston reversal point (TDC)

14 first piston reversal point (UT)

15 Condensate displacement

16 condensate outlet

17 expansion space

Claims

1. A method for operating a gas expansion engine by a gas, preferably by CO 2, which at least one inlet valve (7) and an outlet valve (6) having working cylinder (1) and one between a first piston reversal point (UT, 14) and a second Piston reversal point (OT, 17) in the working cylinder (1) in reciprocating motion piston strokes (10) performing reciprocating piston (2), which limits an expansion space (13) and the size of the expansion space (13) by its back and altered movement, wherein the method comprises at least one cycle of at least the following steps:

a) A working cycle is performed by introducing an inlet volume (8) from the gas in a saturated state via the open inlet valve (7) into the expansion space (13) and by an expansion of the inlet volume (8) resulting movement of the reciprocating piston (2), which moves under magnification of the expansion space (13) in the direction of the first piston reversal point (14, UT), where b) before the first piston reversal point (14, UT) is reached by the reciprocating piston (2), the gas (12) in the liquefied state introduced into the expansion space (13), and then

c) is performed a compression stroke by a movement of the reciprocating piston (2) in the direction of the second piston reversal point (OT, 17) with reduction of the expansion space (13) and under compression of the inlet volume (8) and the gas in the liquefied state (12) liquefies the inlet volume (8) of the gas,

d) before the second piston reversal point (OT, 17) is reached by the reciprocating piston (2), at least part of the gas in the expansion chamber (13) is liquefied by the movement of the reciprocating piston (2) towards the second piston reversal point (FIG. OT, 17) from the expansion space (13) via the outlet valve (6) in a depot (3) displaced, and then e) is carried out via a heat exchanger (5) an isobaric transfer of heat from the depot (3) guided gas (4) in the liquefied state until it is evaporated and available as a gas in a saturated state.

2. The method according to claim 1, characterized in that for the inlet volume (8) of saturated gas, which is introduced via the inlet valve (7) into the expansion space (13), saturated gas is used, which by the isobaric heat transfer the gas has formed in the liquefied state in the heat exchanger (5).

3. The method according to claim 1 or 2, characterized in that for the gas (12) in the liquefied state, which is introduced into the expansion space (13), gas (12) is used in liquefied state from the depot (3).

4. The method according to claim 3, characterized in that the gas (12) is injected in the liquefied state in the expansion space (13) under pressure.

5. The method according to any one of the preceding claims, characterized in that after a closing of the inlet valve (7), the expansion of the inlet volume (8) begins.

6. The method according to any one of the preceding claims, characterized in that the displacement of the at least part of the gas in the liquefied state from the expansion space (13) by means of the pressure built up during the compression stroke in the expansion space (13).

7. The method according to claim 6, characterized in that the

Outlet valve (6) is controlled by the pressure in the expansion space (17).

8. The method according to claim 7, characterized in that the

Exhaust valve (6) is designed to be characterized by by the pressure in the Expansion space (17) can be moved from a closed position to an open position.

9. The method according to any one of the preceding claims, characterized in that the expansion of the inlet volume (8) of the gas in a saturated state with reduction of pressure and / or temperature of the gas to the triple point (TP) of the gas takes place when the first piston reversal point (14, UT) is reached.

10. The method according to any one of the preceding claims, characterized in that the gas is introduced in the liquefied state (12) substantially under the conditions prevailing in the triple point (TP) of the gas conditions from the depot (3) in the expansion space (10) and in the course of the working cycle under a two-phase change (FIGS. 5, 2-3) as isobaric wet gas / liquid fluid (14) is cooled to the boiling point.

1 1. Method according to one of the preceding claims, characterized in that in the course of the compression stroke an isothermal and isobaric wet gas compression by the reciprocating piston (2) in gas-liquid equilibrium with condensation above the boiling line before reaching the second piston reversal point (OT, 17) through the reciprocating piston (2) ends.

12. The method according to any one of the preceding claims, characterized in that the lifting piston (2) drives a crank drive or a linear drive.

13. The method according to any one of the preceding claims, characterized in that the thermodynamic state of the gas is always kept below the critical point (KP) of the gas in a subcritical state.

14. The method according to any one of the preceding claims, characterized in that C02 is used exclusively as the gas and the gas is formed in the liquid state by liquid CO 2.