EP0178348B1 - Gas compressor directly driven by a heat supply - Google Patents

Description

The invention relates to a gas compressor operated by supplying heat with the features of the preamble of patent claim 1.

Such a gas compressor is known from DE-A 3246633. Here, two working cylinders are used, in which displacement pistons are moved back and forth by an auxiliary drive. A heater, half the exchange surface of a common heat exchanger and a cooler are arranged in the primary circuit assigned to each working cylinder. The cold part of each working cylinder is connected to a double-acting fluid separator at opposite chambers, in which a sliding double-acting free piston is arranged. This is e.g. B. formed as a symmetrical differential piston that forms with the housing of the fluid separator both the pressure chambers connected to the cold chambers of the working cylinder, and also closes two pump chambers with a smaller cross section, which are filled with a flowable working medium. The pump chambers are connected via check valve pairs with different flow directions to two pressure vessels into which the working medium is pumped and kept under pressure by a gas cushion. A work machine can be connected to the two pressure vessels. This known gas compressor requires two working cylinders, since the countercurrent heat exchanger contained in the external thermal circuit is necessary in order to supply both working cylinders with energy as thermal compressors. This structure is unnecessarily complex and therefore expensive. In addition, the pump piston of the double-acting fluid separator which is positively coupled to the pressure changes in the cold chambers of the working cylinders does not allow an optimal conversion of the pressure changes into pressure energy in a wide frequency range.

US-A 4215548 describes in FIG. 7 a gas compressor with a single working cylinder, the thermal outer circuit of which has a heater, a regenerator and a cooler. The working piston is a type of free piston. A membrane arranged in the working area serves as the end of a double container filled with liquid, which has a thin connecting line. The “piston” containing the membrane acts here as a resonant piston for decoupling mechanical work. This structure enables pressure energy to be obtained only in a narrow frequency range, in which the required phase lag of 90 ° is guaranteed.

The invention has for its object to provide a gas compressor that is compact and simple, therefore cheaper to build and which allows the production of pressure energy in a wide frequency range.

The invention solves this problem with the characterizing features of claim 1.

The gas compressor according to the invention can be made more compact and simple, and therefore inexpensive, by using only a single working cylinder. On the other hand, pressure energy is obtained over a wide frequency range, the single-acting fluid separator used allowing the automatic adaptation between the pressure conditions in the secondary circuit having an expansion machine and the changing pressure in the cold chamber of the working cylinder. In addition, by using a fluid separator for the compressor formed by the working cylinder and the secondary circuit with the expansion machine, different working media can be used. Helium gas of high pressure is preferably used in the compressor and a gas / oil mixture is used in the working group, which allows an oil-lubricated and pressure-tight expansion machine to be used.

Further configurations of the invention result from the subclaims.

• Fig. 1 eine schematische Ansicht des Gasverdichters;
• Fig. 2 ein Diagramm des Druckverlaufs des Arbeitsgases;
• Fig. 3 ein Diagramm des Volumendurchsatzes des thermomechanischen Konverters;
• Fig. 4 eine Teilansicht einer geänderten Ausführungsform;
• Fig. 5 eine Teilansicht einer weiteren Ausführungsform.

The invention is explained in more detail with reference to exemplary embodiments shown in the drawing. The drawing shows:

• Figure 1 is a schematic view of the gas compressor.
• 2 shows a diagram of the pressure profile of the working gas;
• 3 shows a diagram of the volume throughput of the thermomechanical converter;
• Fig. 4 is a partial view of a modified embodiment;
• Fig. 5 is a partial view of a further embodiment.

The gas compressor consists of the working cylinder 1, in which the poorly heat-conducting displacement piston 2, which is attached to the piston rod 3, which is pressure-tightly guided through the cylinder base, is moved approximately sinusoidally between the top and bottom dead center by the crankshaft 5 and the connecting rod 4. The heat output required for operation is fed to the working cylinder 1 via the fin heat exchanger 6 inside the combustion chamber 7. The cylinder head and the lower cylinder chamber 8 are connected via the thermal regenerator 9, the cooler 10 and the said fin heat exchanger 6, so that only the pressure difference, which is caused by the flow losses in the heat exchangers 6, 10 and in the regenerator 9, is loaded on the displacement piston 2. The thermal insulation of the parts located at high temperature (400 to 800 ° C.) is only indicated in FIG. 1; however, it is partly responsible for the efficiency achieved in converting heating energy into pressure energy.

The lower working space 8 of the cylinder 1 is connected to the fluid separator, which is shown in FIG. 1 as a divided, flat pressure vessel, which consists of two spherical caps 11 a, 11 b, which are separated gas-tight by the elastic membrane 12. The calotte 11b is connected via the check valves 13, 14 with different flow directions to the pressure vessel 15 or to the pressure-tight crankcase 16, in which the electric motor 17 for driving the displacement piston is arranged. The expansion motor 18 is connected between the high-pressure tank 15 and the crankcase 16 functioning as a low-pressure tank, the flow rate of which can be adjusted by the control valve 19.

Since the amount of gas contained in the working cylinder 1 and connected partial volume 11 of the fluid separator is constant, the gas pressure set therein will change periodically when the displacement piston 2 is pushed back and forth between the dead center positions.

2 shows the pressure curve in the working gas in the event that the pressure in the pressure vessel 15 is higher than the maximum value in the working cylinder and the valve 19 is closed. The components 15, 16 and 18 connected to the chamber volume 11b b of the fluid separator are filled with a gas-oil mixture; In addition to helium or hydrogen, nitrogen or carbon dioxide are also suitable as pressurized gas, since their kinematic toughness is noticeably greater and the adiabatic exponent is smaller than that of helium. The latter brings about a lower temperature drop in the working medium during expansion in the expansion motor 18.

If the displacement piston 2 is at the bottom dead center and thus the main amount of the working gas in the upper cylinder section, the gas pressure reaches its maximum value and the chamber volume 11b is compressed until the gas pressure in the cylinder 1 matches the pressure P _h in the container 15, the check valve 14 remains closed during this time. When the displacer 2 moves upward, the gas pressure decreases and, after the pressure P _n prevailing in the crankcase 16 is reached, the valve is opened and the gas-oil mixture is sucked into the chamber 11b; in extreme cases the membrane 12 lies against the inner wall of 11 a.

wenn dieser das Druckgefälle ΔP=P_h-P_n verarbeitet.When the valve 19 is open, the expansion motor 18 is supplied with the gas-oil mixture at the pressure P _h and leaves it at the pressure P _n . If you designate the volume flow with V (m ³ / s), the mechanical power generated in the expander is

if the latter processes the pressure drop ΔP = P _h -P _n .

With a large volume throughput, the pressure drop in the converter will decrease, as can be seen from the dashed pressure curve in FIG. 2, which is plotted over the crank angle Φ. At the crank angle Φ _h , the valve 13 opens and the chamber volume 11 b of the fluid separator is pumped into the high-pressure container 15 during the phase Φ _h <behälter <2 Π. During the upward movement of the displacer 2 decreases, the gas pressure, and reaches at the phase angle Φ _n prevailing in the crankcase 16 pressure P _n. Between Φ _n <Φ <Π the valve 14 remains open and the gas-oil mixture is sucked into the chamber 11 b. With increasing volume flow V, ie with increasing speed n of the expander 18, the pressure difference (P _n -P _n ) decreases, since the opening angles Φ _n or Φ _h shift towards smaller crank angles.

The relationship between Ap and V results from: For V = 0, i.e. H. when the expansion motor is at a standstill, Δp and thus the torque generated will reach its maximum value. If the speed proportional to V increases, then Ap decreases, but the product Δp.V = P (power) reaches a maximum value, which decreases again at high speeds. 3, torque D and power P are plotted over the volume throughput V of the thermomechanical converter or over the speed of the expander 18. The performance characteristics of the machine, which consists of a converter and expansion motor, correspond to that of a main-circuit electric motor; in the application for driving a vehicle, the coupling device and a manual transmission are therefore unnecessary.

In the primary circuit, ie in the working cylinder 1 with connected heat exchangers 7, 9 and regenerator 8, instead of helium or hydrogen gas, the superheated steam of a condensable substance, eg. B. propylene, fluorinated hydrocarbons, application. The advantage of these substances, which deviate greatly from the ideal gas behavior in the area of saturated steam conditions, for the primary circuit is that a lower heating temperature T _{2 can be used} for the heat exchanger 6 (FIG. 1) for the same pressure ratio P _h / P _n , and thereby heat conduction and Radiation losses of the cylinder 1 can be reduced.

- Any working medium can be used in the secondary circuit of the fluid separator, which contains the expansion motor or a heating machine in addition to the pressure buffers. As such, a mixture of nitrogen or carbon dioxide and mineral oil has the advantage that a relatively high operating frequency can be used in the converter and separator and the essential lubrication and sealing of the expansion motor is guaranteed for the secondary circuit. At the same time, with a multi-atomic working medium in the secondary circuit, because of the smaller adiabatic exponent, the temperature increase that occurs in the separator during the compression cycle and the temperature decrease that occurs in the engine during work relaxation is reduced. The latter can be used to reduce the heat output to be dissipated in the cooler 10 with the aid of an additional heat exchanger.

In the secondary circuit instead of the crank housing 16, a second pressure vessel is connected to the check valve 14, into which the expanded working medium from the expander 18 flows from the pressure p _" . Since the conventional expansion motors act as a pump when the direction of rotation is reversed, this property can be used together with the said pressure accumulators to to store the braking energy generated during the braking process in a vehicle driven by such an expansion engine, for this purpose the gas lines leading to the expander are exchanged with the aid of a special changeover valve.

In a further design, which is shown in simplified form in FIG. 4, the expansion motor 18 is also located in the crankcase 16. Its output axis 20 is led out of it in a gas-tight manner. The expansion motor 18 is coupled to the electric motor generator 17 and, after starting, not only drives the crankshaft 5 or the displacer 2, but can also alternatively and controllably generate electrical energy which can be stored.

The expansion motor 18 is not tied to the location of the thermomechanical converter, but can be connected to the control valve 19 or to the crankcase 16 by means of flexible high-pressure hoses via the releasable couplings 21, 22. It is also possible to operate several expanders of the same type in parallel, the speed of which is automatically set in accordance with the torque output. There are many possible applications in the areas of vehicle drives, mobile and stationary hoists, conveyor systems, etc.

The performance and dimensions of this new type of heat engine can be derived from theoretical considerations and practical results: With a stroke volume of 1 dm ³ , a heating temperature T ₂ = 500 ° C, a maximum pressure P _h = 100 bar at a speed of 1500 rpm the theoretical mechanical power is about 25 kW; In practice, this value is only reached by about 65% by the efficiency of the converter and the expansion motor.

Larger performances are carried out as multi-cylinder machines; the mutual alignment of the cylinders and the phase position of the displacement pistons are expediently chosen such that a) the free mass forces are compensated for, b) the lower working spaces 8 of the cylinders are connected to displacement side pistons with the gas side 11 of a common fluid separator, and c) the high-temperature heat exchanger 6 of all working cylinders are arranged in a common combustion chamber. A special construction of the fluid separator, which advantageously replaces the one shown in FIG. 1 when the mean working pressures in the primary and secondary circuits are to be different, is shown in FIG. 5. In this embodiment, the differential piston 24, 25 can be freely moved between the end bearings in the pressure-resistant housing 23 with the check valves 13, 14. The volume enclosed by the rear of the piston 24 and the housing 23 is, for. B. filled with the fluid of the secondary circuit and is connected to the pressure vessel 26, in which the constant, adjustable compensation pressure _Pe prevails. The extreme pressures _Ph and p _" in the secondary circuit are translated in comparison to those in the primary circuit in the ratio of the corresponding piston cross sections. By choosing the appropriate compensation pressure P _c , the pressures shown in FIG. 1 can be shifted downward and the minimum pressure P _min can be compensated for approximately zero will.

• 1) Die beschriebene Wärmekraftmaschine wird durch äussere Zufuhr von thermischer Energie betrieben, wobei als Primärenergieträger flüssige, gasförmige und feste Brennstoffe genutzt werden können. Die bei ihrer Verbrennung auftretenden relativ niedrigen Betriebstemperaturen von maximal 800°C ergeben im Vergleich zum herkömmlichen Otto- oder Dieselmotor nur etwa ein Zehntel der Schadstoffemission an Stickoxiden und Kohlenmonoxid.
• 2) Der in der beschriebenen Wärmekraftmaschine ablaufende Arbeitsprozess spielt sich in einem kleinen Druckverhältnis von etwa 1:2 ab, wobei die wenigen beweglichen Teile, wie Verdrängerkolben, nur gegen geringe dynamische Druckdifferenzen abgedichtet zu werden brauchen, was sich in einer langen Lebensdauer und hoher Betriebssicherheit niederschlägt.
• 3) Während im Primärkreis vorzugsweise inertes Helium unter hohem Druck angewandt wird, werden im angekoppelten Sekundärkreis für den Betrieb des oder der Expansionsmotoren passende Gas-Ölgemische als Arbeitsmedium benutzt, welche eine zusätzliche Dicht- und Schmierfunktion erfüllen.
• 4) Bei der Anwendung auf den Fahrzeugantrieb lässt sich auf einfachste Art der Einzelradantrieb realisieren, da die Expansionsmotoren über flexible Druckschläuche an die gemeinsamen Druckbehälter angeschlossen werden. Durch Vertauschen von Zu- und Rückleitung der einzelnen Motoren mit Hilfe herkömmlicher Umschaltventile kann die Bremsenergie als Druckenergie in den Druckbehältern gespeichert werden.

The following advantages can be highlighted in comparison to conventional heat engines:

• 1) The described heat engine is operated by external supply of thermal energy, whereby liquid, gaseous and solid fuels can be used as primary energy sources. The relatively low operating temperatures of a maximum of 800 ° C that occur during combustion result in only about a tenth of the pollutant emissions of nitrogen oxides and carbon monoxide compared to conventional gasoline or diesel engines.
• 2) The working process taking place in the described heat engine takes place in a small pressure ratio of approximately 1: 2, whereby the few moving parts, such as displacement pistons, only need to be sealed against small dynamic pressure differences, which results in a long service life and high operational reliability precipitates.
• 3) While inert helium under high pressure is preferably used in the primary circuit, suitable gas-oil mixtures are used as the working medium in the coupled secondary circuit for the operation of the expansion engine (s), which fulfill an additional sealing and lubricating function.
• 4) When applied to the vehicle drive, the single-wheel drive can be realized in the simplest way, since the expansion motors are connected to the common pressure vessels via flexible pressure hoses. By swapping the supply and return lines of the individual motors with the help of conventional switch valves, the braking energy can be stored as pressure energy in the pressure vessels.

Claims (8)

1. Gas Compressor operated by heat-input wherein a first gassy working medium in a working cylinder (1) is pushed back and forth, by way of a compression cylinder activated by an auxiliary drive (17), through a parallel-switched primary cycle comprising a heater (6, 7), a temperature converter and a cooler (10), and alternately brought up to a high temperature by heating inside the heater (6, 7) within the hot section of the working cylinder (1) and brought to a low temperature by the cooler within the cold section whereby a fluid separator which is divided into chambers (11 a, 11 b) by a slideable, gas-tight wall (12, 24, 25) is provided with its one chamber (11 a) communicating with the cold section (8) of the working cylinder (1) whereas another chamber (11 b) is connected through non-return valves (13, 14) of different flow directions with two pressure vessels (15,16), which are connected with a working machine (18), and a secondary cycle consisting of the other chamber (11 b) of the fluid separator, pressure vessels (15,16) and the working machine (18) and filled with a second wirking medium, characterised in that there is only one working cylinder (1) the primary cycle of which has a regenerator (9) as temperature converter; the fluid separator simply works with only two chambers (11a, 11b) fitted, one of the chambers (11 a) being connected with the cold section (8) of the working cylinder (1) and the other chamber (11 b) being connected through only two non-return valves (13, 14) of different flow directions with the two pressure vessels (15, 16); the wall of the fluid separator being formed by a membrane (12) which separates the chambers (11a, 11b) or by a free piston (24, 25); the working medium of the secondary cycle is gas, steam or a gas-oil mixture; and that the working machine is an expansion machine.

2. Gas compressor according to claim 1, characterised in that the fluid separator is composed of a divided pressure-resistant casing the halves (11 a, 11b) of which are internally in the shape of part-spherical segments the membrane (12) being of metallic or rubber-elastic material.

3. Gas compressor according to claim 1, characterised in that the fluid separator is composed of a differential piston (24, 25) in a pressure-resistant casing (23) and seals off three changeable, interdependent spaces which are connected with the cold section (8) of the working cylinder (1), with the pressure vessels (15, 16) through two non-return valves (13,14) and with a further pressure vessel (26) which contains the working medium of the primary or the secondary cycle with adjustable pressure.

4. Gas compressor according to claims 1 to 3, characterised by the pressure vessels (15, 16) being connected with several parallel working expansion machines (18).

5. Gas compressor according to claims 1 to 4, characterised by the crankcase (16) being pressure-resistant and serving as one of the pressure vessels.

6. Gas compressor according to claims 1 to 5, characterised by the crankshaft (5) for driving the suppression piston (2) being driven by an electric motor-generator (17) positioned inside the pressure-resistant crankcase (16) and itself coupled to an expansion motor (18) which is connected to the pressure vessels (15, 16) and the exit of the output-shaft (20) from the crankcase being pressure-resistant.

7. Gas compressor according to claims 1 to 6, characterised by the use of superheated vapour such as propylene or fluorinated hydrocarbon, as first working medium in its primary cycle.

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