DE2342103A1 - Hot gas engine - has cycle involving isothermal, isochoric and isobaric phases and incorporates regenerative heat exchanger - Google Patents

Abstract

Heat engine utilises a cycle which has isothermal, isochoric and isobaric phases and which would yield high cycle efficiencies when used as a propulsive cycle for a motor vehicle. The engine utilises carbon dioxide as the working medium and has a burner which supplies heat to the system. Cold gas is induced from a reservoir into a water cooled cylinder through a valve. The gas is compressed in the cylinder and delivered to a higher pressure reservoir from whence it passes into a second larger cylinder via a regenerative heat exchanger. The larger cylinder passes the further compressed gas through a heat exchanger warmed by the burner before returning it the reservoir via the regenerator.

Description

"Regenerative Heat Engine"

With hot gas machines, an ideal cycle process with isothermal expansion and compression as well as isobaric heat » Intake and removal from and to the outside aimed at, as this has a good thermal efficiency and a high specific level Performances results · The exchange of heat from one isotherm to another is lossless in the ideal process carried out by a regenerator

In practice it has been shown »that the exchange is great Heat quantities per work cycle within the machine require large heat accumulators with a considerable flow length » the dead space of the machine due to its own volume and have such high flow resistances that the machine cannot be run at high speeds can and related to the construction volume, results in a correspondingly lower specific power ·. It is also at the usual oscillating gas movement in the machine is not possible, the external heat exchange only temporarily to relocate the compression and expansion phases

One is therefore forced to deal with hardly any ieoterms but predominantly adiabatic expansion and Compression, which has a lower thermal efficiency

The dead space of the machines also has a decisive influence on the way they work a better thermal efficiency, well with compression forces more gas weight into the cooler and flows through the heater during expansion, thus reducing the pressure drop here · However, the proportion of dead space is reduced the quality level to a far greater extent, so that the overall efficiency of the machine decreases

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The many influencing factors, optimized, Newer hot gas machines already have increased speeds, but if necessary, they come close to the piston speeds that are customary and controllable in internal combustion engines today, because their speed range is still higher is limited by the flow resistances of the heat exchangers, especially the regenerator

These machines have the disadvantage that the working medium is in them, which damages the work process does not revolve, but oscillates, so that during the heat exchange it is of an only theoretically existing isotherm on the other hand on the storage of heat in material mass and the later extraction of warnings from this mass are instructed, whereby the regenerative heat flow does not harmonize with the flow of heat through the machine, but one heat flow affects the other, so that either the specific power or the efficiency of the Machine is restricted.

Since the regenerative heat flow lags behind the piston strokes, it does not occur exactly in the isochoric phases, but rather during the actually isothermal compression and expansion, which is thereby falsified, and here diminishes the Work-generating heat flow through the machine to and from the outside

The oscillating mode of operation also has the disadvantage that part of the working gas remains in the harmful dead space of the heat exchanger, i.e. it only oscillates within its channels, but does not participate in the work performance.

Stirling engines are particularly uncomfortable from the fact that it was not possible to ensure the complete gas transport in the correct phase to the correct zone of the To realize the working area by means of a crank drive · The result is that these machines usually have a uncomfortably large proportion of the working medium in the wrong one Zone of the work area, i.e. not in the

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hot and not in the cold zone during compression, and thus does not participate in the change of state

All of these problems will be addressed to the machine after the Invention, however, with increased technical effort, solved by keeping the working medium in the machine not oscillated, but forced by RQdcstromeperren will circulate that the amplitudes of the expansion work by including sensors in the gas circulation of those of the compression work are made independent, that of the usual respective pressure equality in all Clearance of the circuit and that in the work process the advantage of eVies large dead space for the thermal effect is perceived without the machine with the to burden the disadvantages otherwise arising when using large dead spaces

Fig. 1 shows the scheme of the machine according to the invention.

Fig. 2 shows a P, V diagram of the machine in a performance comparison with the diagram of a diesel engine

Fig 3 shows a T, S diagram of the machine

Fig.4 shows the same diagram in comparison with those of other cycle processes

Description t

The machine according to the invention shown schematically in sketch 1 has a number of compressor cylinders 1 with external cooling 2, the working medium via automatic inlet valves 4 from a large, cold low-pressure sensor 5 suck in and it is compressed via automatic outlet valves 6 in a somewhat warmer high-pressure sensor 7 that is pushed out

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The working amplitudes of the compressor cylinders 1 overlap with a phase shift, so that the inflow of The working medium from the compressor cylinders 1 into the high pressure sensor 7 is almost uniform

The working medium flows through from the high pressure sensor 7 the passage 8 a of a countercurrent heat exchanger 8 and an adjoining heater 9 with an outer Heating 10 and a heat-conducting and heat-storing heat storage 11 inserted between the heating 10 and the heater 9 in the hot distributor 12 of small volume

It occurs via positively controlled inlet valves 13 in the hot working cylinder 14 · Open the inlet valves 13 against the direction of flow and are actuated by a camshaft 18 fitted with inclined cams 17, which is axially displaceable and by their displacement the opening time of the inlet valves 13 can be changed.

After the expansion has taken place in the working cylinders 14, the working medium also inevitably passes through controlled exhaust valves 19 from the working cylinders 14 from, and then flows through the passage 8 b of the regenerative countercurrent heat exchanger 8 and on the cooler 21 in the cold low pressure sensor 5, from from which the work game starts again

Dae Gee at the t-displacement of the hot cylinders in the working cylinders 14 working piston 23 sliding on heat-resistant seals 22 is larger than that of the working piston 23 in the compressor cylinders 1 running compression piston 24

The engine 25 of the compressor piston 24 can have a Gearbox 26 with variable ratio from the engine

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the working piston 23 are driven. At the automatic inlet valves 4 of the compression cylinders 1 Hold-down devices 28 are provided with which they can be prevented from closing individually or as a whole

By storing working gas in a regulating tank and withdrawing it back, the mean pressure of the machine be lowered or raised again · All that is needed is a two-way valve 32 · The operating gas is taken from the high-pressure vessel 7, stored, or fed to the low-pressure sensor 5.

The pressure difference between the outlet and expansion pressure can still be determined by relieving or loading an am High pressure boiler 7 attached pressure relief valve 33 lower or increase again, which is a selectable The level of the working pressure opens and a more or less large proportion of the working gas passes through the bypass line 34 returned to the low-pressure boiler 5.

Function"

The diagrams of the pressure-volume diagram and the temperature-entropy diagram, in Fig. 3 and 4, below labeled with PV and TS diagrams illustrate the Processes in the machine

The working gas enters the compression cylinder 1 isothermally and when cold one. The compressor pistons 24 first compress it isentropically and, as the temperature increases, by releasing heat to the cylinder wall 1-politropically. she start the compression work at an outlet pressure P. from 36 to 50 atu, which in the course of compaction, each according to the design of the machine, increases to a minimum of 85 to a maximum of 160 atmospheres · You will only be towards the end their compression stroke, when they begin, the compressed working gas isobaric through the automatic exhaust valves

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to push out into the high pressure transducer 7, fully loaded are below the final pressure Pm.

In the PV diagram, Fig. 2, curve 1-2 shows the pressure increase above the stroke of the compressor piston 24 for the machine, since the stroke volume of the compressor 1 of the proposed If the machine is only about a third of that of the working cylinder 14, the pressure is reduced when the pressure is equal Mechanical compression work to be expended during the isobar extension phase to a third of the expansion work and includes the negative working area A-1-2, where A denotes the outlet pressure * this first politrope, then isobaric compression is in the T, s-Diagrajnm - Fig. 3 - as isentropes b-n and as isobars n-c ^, recognizable. In practice, when the working gas passes through the regenerator 8, it simultaneously passes through a locally parallel one isochoric phase, which is shown as a curve in the T, S diagram according to Fig. 4 n-n * is inserted · which results from the volume difference resulting larger swallowing amount of the expansion cylinder 14 must by non-mechanical heat supply Q via the Heinzer to be balanced

In the P, V diagram - Fig; 2 - the height A-Pm gives the maximum indicated pressure Pi max · In comparison with the drawn P, V diagram of a diesel engine, the Working surface of the machine according to the invention appear double because it works in two-stroke · The effective The comparison area is supplemented with dotted lines in Fig. 2

Several working pistons 23 of the working cylinders 14 move simultaneously during their expansion stroke with multiple; Working medium from the compressor cylinders 1 extending compressor piston 24 · The between the Pistons 23 and 24 enclosed volume increases several times over while it is removed from the high-pressure vessel 7 and the working cylinders 14 are fed through the regenerator 8 and the heater 9 and heated vigorously in the process.

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Since compressed gas is continuously withdrawn from the high-pressure vessel 7 and supplied by the compressor piston 24 at the same time there is an iso & are towards the end of the compression stroke Compression, which takes place parallel to the isochoric heat exchange in the regenerator 8 and to the isothermal heat supply in the heater 9 The mechanical work for compression is diverted from the useful work of the expansion piston 23 and represents reactive power

During the isobaric expansion in the working cylinders 14 initially due to the volume capacity of the high-pressure vessel 7 the heat supply by the heater 9 is equal to the increase in volume due to the increasing throughput through the same the working cylinder 14 at

Coming from the high-pressure vessel 7, the compressed gas flows through the needle-tipped gas in an approximately isochoric phase Passage Sa of the regenerative heat exchanger 8 and removes heat from it, which simultaneously from the exhaust gas of the working cylinder 14 in its countercurrent phase Sb, equipped with the same needles is fed · The needles conduct the regenerative heat continuously through the partition from the passage 8b in the passage 8a.

The engine according to the invention also differs in this phase from the Stirling engine, which also works with two isochors, in which the storage of heat and its recovery oscillate in Intervals and by no means takes place in the most favorable phase.

The compressed gas flows isothermally through the heater 9 and through the open against the inflow, absorbing a lot of heat Inlet valves 13 in the working cylinder 14, the expanding working piston 23 as long as isobaric expansion work as long as the inlet valves 13 are open phase corresponding to the Ericsson process, can be carried out during reduce or shorten driving operations by using the

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Opening time of the inlet valves 13 by means of laterally displaceable Inclined cam 17 is changed. A longer isobaric expansion phase brings in more power, but requires a larger isochoric heat transfer in the heat exchanger 8 · Since these never work one hundred percent can, the isobaric expansion is always burdened with a heat dissipation to the outside via the cooler 21. This Energy loss increases when the isobaric phase is extended on and reduces the efficiency.

In the machine according to the invention, the controllable isobaric phase is limited to 30 to 60% of the expansion stroke.Then with the closing of the inlet valves 13, in contrast to the pure Ericsson process, an isentropic expansion as with Joule begins, in which the heat supply is omitted and the power drawn from the working pistons 23 acts as a pressure and temperature drop in the working gas. Therefore, compared to the original Ericsson machine, you can get away with a smaller regenerator 8, has fewer losses of thermal energy to the outside via the cooler 21 and can run the machine with a closed circuit because the expansion pressure with which the working gas is pushed out of the cylinders 14 is sufficiently deep.

The heat-storing gas passage through the passage 8b of the heat exchanger 8 corresponds to the second isochoric and the heat-extracting gas passage through the cooler 21 of the second isobaric phase of the cycle of the machine.

The relaxed and cooled working gas arrives almost continuously in the cold low-pressure sensor 5, since several working cylinders 14 are provided, their extension strokes overlap and their exhaust pipes unite before entering the heat exchanger 8.

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The isothermal filling of the compressor cylinder now follows from: the low pressure sensor 5, upon completion of which the described cycle begins again

If one looks at the diagram in Fig. 3, one recognizes one that the cycle of the machine according to the invention has more work surface than a pure Ericsson machine, whose isobars are drawn in dashed lines for the same temperature and pressure ratio and with a smaller pressure difference than an Ericsson machine with a higher pressure ratio, the assumed characteristics of which supplement the diagram in Fig.3 with dotted lines

In Fig. 4 the T, s diagrams are different Circular processes taking into account the same temperature and pressure limits compared to those enclosed by the circular process Work surfaces shown

The result of the state changes is marked here due to the constant greatness

Ericsson T P. τ P. with the corner pointsι abcd Stirling ϊ V T ν a e c f Joules S. P. S. P. a g c h diesel 8th P. S. ν agc! Otto S. ν 8th ν a k c 1 Carnot S. T S. T m g 1 h Are T ν P. T ν ρ a. * b η c. * d u

The qualitative comparison of the work surfaces confirms that in the machine according to the invention from the mass of the Medium the greatest work performance is obtained.

The initially isobaric expansion avoids pressure peaks and engine overloads, gives high specific Power, has the starting torque of a steam engine, but requires a corresponding supply of heat and when extending the isobaric expansion phase also allows greater heat dissipation to the outside.

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The internal regenerative heat flow is in the T, s diagram according to Fig. 3 as marked with arrows area · Since this heat flow Qi with flow resistance and heat flow losses is afflicted, the structural volume and the weight of the regenerative heat exchanger depend on its thickness and this energy transfer only protects against losses to the outside, but does not give up any work, one tries to to keep it as small as possible in relation to the effective heat throughput of the T, s diagram

Hit the help of this heat flow Qi and the closed off to the outside The cycle is only made possible, the machine with high output pressure and the voice of the heat flows accordingly excessive final pressure, i.e. in the steep part of the compression and expansion curve and with, despite one thing relatively low expansion ratio to let work very large pressure differences, which have a high specific Induce power per work cycle · A smaller internal heat flow allows higher speeds; a larger total— heat flow provides the basis for a higher torque of the machine

In addition to this main task in principle, the internal heat flow Qi through the countercurrent regenerator 8 fulfills nor the condition that the external heat flow into the Machine ahead so that it is only fed in when the pressure and temperature level is increased, while the Removal of heat to the outside only when the working medium is relaxed and precooled in the regenerator 8 takes place.

If this condition is met, the machine receives T 2 - T 1 in accordance with the basic thermodynamic equation

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even at a temperature difference of 30 ⁰ C to 850 ⁰ C a theoretical efficiency of over 73%, which at

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the practically feasible increase in the maximum temperature to HOO ⁰ C to over 78%. A lowering of the lower temperature limit per C is about four times more favorable than an increase in the upper temperature limit. Known hot gas machines therefore always require an oversized cooler.Since in the machine according to the invention, as the T, s diagram - Fig.3 - shows, a larger proportion of the heat supplied is converted into useful mechanical work, it only requires a cooler of medium capacity and a reasonable fan performance

The most favorable mode of operation of the machine takes place accordingly according to the diagram - Fig · 4 - in eight phases « Namely two isochoric changes of state that neither work generate still - theoretically - consume, two isotherms with heat input at high pressure and elevated temperature and heat dissipation at low pressure and reduced temperature, as well as expansion in two phases and compression, where the expansion is first isobaric, then isentropic, and compression is first adiabatic, then isobaric runs. There are hardly any losses if the isothermal and isobars, with mechanical piston movement connected phases are not separated from each other, but run into each other, since smoothing transducers 5.7 of sufficient Volume are turned on in the circuit.

The power control of the machine for lower workload is initially carried out by shortening the isobars Expansion phase by means of the control of the inlet valves 13, in which efficiency is gained because the Heat outflow to the outside through the cooler 21 is reduced.

Subsequently, the performance is achieved by extracting compressed gas from the high-pressure boiler 7 and storing it in a Control accumulator 32 lowered, the mean pressure falling and the efficiency - as with Stirling - increasing.

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The further decrease in performance until idling or The machine comes to a standstill by relieving the pressure relief valve 33 to a greater or lesser extent, by means of which the pressure difference between the high pressure 7 and low pressure boiler 5 is reduced to zero leaves.

Here, a more or less large part of the Working gas blindly, goes through the cooler 21, but does not take part in the heating 8, 9 and the expansion 24.

The range between the output and working pressure of the machine can be reduced when using several compressor cylinders 1 also in another way, namely by a misfire control 28 for some of these cylinders Carry out · The more compressor cylinders 1 by keeping them open their inlets 4 are put out of operation, the lower the pressure difference of the working gas, wherein the expansion ratio is greater because the larger displacement of the expansion cylinder 14 is not changes·

Not afflicted with reactive power or additional flow resistance, but the design is much more complex is a relative to the speed of the engine shaft 25 of the working piston 23 variable speed of the engine shaft 27 of the compressor piston 24 with the help of a continuously variable transmission 26 feasible, which can achieve the same control effect «Such a Gearbox has to transmit high torques and is correspondingly expensive

Since the heater 9 via a heat accumulator 11 on the compressed gas acts, a readjustment of the heating 10 does not need in the case of brief fluctuations in the power consumption to be done. The heat accumulator 11, which includes the heater 9, acts as a buffer in this case Energy accumulator that insulates against the environment, a spontaneous one even after the machine has been idle for several hours Starting at full load is possible.

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In city traffic, high acceleration powers are only required at intervals and for a short time, while when the vehicle rolls evenly at a moderate speed, only a small amount and when the vehicle is at a standstill At the intersections dominated by traffic lights, apart from the effort for mechanical engine friction, no power must be applied · A continuous feed of about 6 KW or 8 HP into the heat storage 11 is likely fully enough to drive a heavy car very lively in city traffic. This energy requirement is likely Consume less than 2 liters of simple fuel per hour · This is what you get in city traffic Consumption of almost 6 liters of fuel for 100 km of urban distance and meets all environmental protection requirements.

Since the machine according to the invention works with direct current of the medium and has intermittent locks in the circuit, it is largely insensitive to Beaug on the dimensioning of more flow-efficient further line, Regenerator and heater cross-sections · You are therefore not on the use of hydrogen with this machine or helium, but can use cheap, easy-to-obtain and easy-to-use media

If you drive the machine with carbon dioxide, you can, if necessary, compensate for a possible leakage loss through gas extraction from the burner's own exhaust gas or raise the mean pressure of the machine to the strength limit of the machine When the output pressure in the low pressure sensor 5 falls below an adjustable level, the CO ₂ gas sucked in via the line 36 is cooled in the cooler 21, cleaned in the filter 37 and in a small catalytic converter 38 to remove any sulfur impurities freed before it gets into the machine This compensation of leakage losses makes a hermetic seal by rolling diaphragms and their hydrostatic support unnecessary

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The machine according to the invention can be implemented in many variations. For example, the expansion cylinders 14 and the compressor cylinders can also have the same bore and stroke dimensions if the total cubic capacity is in a favorable ratio.For example, two cylinders of an 8-cylinder machine would work as a compressor and six cylinders as an expansion motor.

Compared to the Stirling system, the advantages of the machine according to the invention often outweigh the additional technical effort that arises from the operation with hot expansion pistons and the valve control .

12 claims follow

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Claims (1)

Patent claims » (1 ^ heat engine, characterized by the arrangement ^ - "^ nung oines multi-cylinder compressor with automatic Inlet and outlet valves, one acting on the working medium during and before the compression work Cooling device, a high pressure sensor, a primary passage of a counterflow heat exchanger, a heat exchanger with external heating, a group of working cylinders with positively controlled Inlet and outlet valves, a heating device that acts on the working medium during expansion, a secondary passage of said countercurrent heat exchanger, a cooler and a low pressure sensor in the named sequence, which the working medium with greatly increased output pressure in a closed Flow through the cycle during each work cycle Heat engine according to Claim 1, characterized by a displaceable mounting of the camshaft the inlet valve control of the working cylinders, the inlet valves of which open against the flow and Equipping the camshaft with inclined cams, the valve lift curves of which extend over different Opening times extend. Heat engine according to claim 1, characterized in that that the displacement of the group of working cylinders per work cycle is greater than the sum of the volume of the compressor cylinder and that this volume during normal operation of the machine have a size ratio of approximately 3: 1. Heat engine according to claim 3, characterized in that that between the engine of the working piston and dom of the compressor piston one in their translation variable power transmission is provided with - 16 bO981 2/0044 whose circuit changes the volume ratio of the working cylinder to that of the compressor cylinder can be changed while the machine is running Heat engine according to Claim 2, characterized by the division of the working stroke of the working pistons into an isobaric, an isochoric and an isentropic phase by means of the valve control and the heating of the working medium as it flows into the working cylinder, these phases in the same sequence also, less exactly separated from one another, merging into one another or one of the phases in the other operating state can be temporarily omitted. Heat engine according to Claim 1, characterized by misfiring devices on the inlet valves the compressor cylinder, the confirmation of which prevents the inlet valves from closing, and one or several compressor cylinders are brought to a stop or connected to and through a row of couplings Uncoupling of individual compressor cylinders from the driving engine. Heat engine according to claim 1, characterized by an inserted between the heater and the heat source, heat-transferring and heat-storing Hasse · Heat engine according to claim 2, characterized by cold, with working medium at medium pressure chambers filled with the machine, in which the control elements of the machine, for example the valve control, work. Heat engine according to Claim 1, characterized by or directly mounted on the working pistons with these articulated plungers of oil pumps. - 17 - bO9812 / 0044 which is the useful work of the machine, bypassing the Directly take from the engine, so that this only the comprassion work and the drive work of the control in addition to mechanical losses Heat engine according to Claim 1, characterized by means known per se, memory, control valve etc to regulate the circulating weight of the working medium, whereby the gas extraction according to the invention from the High pressure boiler and the return to the low pressure sensor takes place. Heat engine according to claim 1, characterized in that that the pressurized gas storage tank serving as a pick-up for the compressor cylinder is loaded with one is equipped with an adjustable pressure relief valve, which at full pressure operation by means of a voltage adjustable The spring is so heavily loaded that it remains closed, but in idle or in the partial load states is less or only very little loaded, so that a more or less large proportion of the compacted Medium with this power control through the cooler into the cold storage in the circuit upstream of the compressor flows back and goes blind Heat engine according to claim 1, characterized by the use of CO ₂ gas as the working medium, which is taken from the exhaust gases of the heating of the machine, filtered, cooled and, in passage through a catalyst, freed from admixtures, for example sulfur components, and added and Decoupling small compressor is compressed, the introduction of the medium takes place in the low pressure sensor, on which a safety pressure relief valve and a pressure indicator is provided. 509812/0044 Empty soap