GB2396664A - Extended cycle reciprocating Ericsson cycle engine - Google Patents
Extended cycle reciprocating Ericsson cycle engine Download PDFInfo
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- GB2396664A GB2396664A GB0302342A GB0302342A GB2396664A GB 2396664 A GB2396664 A GB 2396664A GB 0302342 A GB0302342 A GB 0302342A GB 0302342 A GB0302342 A GB 0302342A GB 2396664 A GB2396664 A GB 2396664A
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- gas
- expander
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- engine
- heat transfer
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02G—HOT GAS OR COMBUSTION-PRODUCT POSITIVE-DISPLACEMENT ENGINE PLANTS; USE OF WASTE HEAT OF COMBUSTION ENGINES; NOT OTHERWISE PROVIDED FOR
- F02G1/00—Hot gas positive-displacement engine plants
- F02G1/04—Hot gas positive-displacement engine plants of closed-cycle type
- F02G1/043—Hot gas positive-displacement engine plants of closed-cycle type the engine being operated by expansion and contraction of a mass of working gas which is heated and cooled in one of a plurality of constantly communicating expansible chambers, e.g. Stirling cycle type engines
- F02G1/053—Component parts or details
- F02G1/057—Regenerators
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02G—HOT GAS OR COMBUSTION-PRODUCT POSITIVE-DISPLACEMENT ENGINE PLANTS; USE OF WASTE HEAT OF COMBUSTION ENGINES; NOT OTHERWISE PROVIDED FOR
- F02G1/00—Hot gas positive-displacement engine plants
- F02G1/04—Hot gas positive-displacement engine plants of closed-cycle type
- F02G1/043—Hot gas positive-displacement engine plants of closed-cycle type the engine being operated by expansion and contraction of a mass of working gas which is heated and cooled in one of a plurality of constantly communicating expansible chambers, e.g. Stirling cycle type engines
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
- F04B39/00—Component parts, details, or accessories, of pumps or pumping systems specially adapted for elastic fluids, not otherwise provided for in, or of interest apart from, groups F04B25/00 - F04B37/00
- F04B39/06—Cooling; Heating; Prevention of freezing
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02G—HOT GAS OR COMBUSTION-PRODUCT POSITIVE-DISPLACEMENT ENGINE PLANTS; USE OF WASTE HEAT OF COMBUSTION ENGINES; NOT OTHERWISE PROVIDED FOR
- F02G2242/00—Ericsson-type engines having open regenerative cycles controlled by valves
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02G—HOT GAS OR COMBUSTION-PRODUCT POSITIVE-DISPLACEMENT ENGINE PLANTS; USE OF WASTE HEAT OF COMBUSTION ENGINES; NOT OTHERWISE PROVIDED FOR
- F02G2242/00—Ericsson-type engines having open regenerative cycles controlled by valves
- F02G2242/02—Displacer-type engines
- F02G2242/30—Displacer-type engines having variable working volume
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02G—HOT GAS OR COMBUSTION-PRODUCT POSITIVE-DISPLACEMENT ENGINE PLANTS; USE OF WASTE HEAT OF COMBUSTION ENGINES; NOT OTHERWISE PROVIDED FOR
- F02G2243/00—Stirling type engines having closed regenerative thermodynamic cycles with flow controlled by volume changes
- F02G2243/30—Stirling type engines having closed regenerative thermodynamic cycles with flow controlled by volume changes having their pistons and displacers each in separate cylinders
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02G—HOT GAS OR COMBUSTION-PRODUCT POSITIVE-DISPLACEMENT ENGINE PLANTS; USE OF WASTE HEAT OF COMBUSTION ENGINES; NOT OTHERWISE PROVIDED FOR
- F02G2270/00—Constructional features
- F02G2270/85—Crankshafts
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
- F05C—INDEXING SCHEME RELATING TO MATERIALS, MATERIAL PROPERTIES OR MATERIAL CHARACTERISTICS FOR MACHINES, ENGINES OR PUMPS OTHER THAN NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES
- F05C2201/00—Metals
- F05C2201/04—Heavy metals
- F05C2201/0403—Refractory metals, e.g. V, W
- F05C2201/0412—Titanium
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
- F05C—INDEXING SCHEME RELATING TO MATERIALS, MATERIAL PROPERTIES OR MATERIAL CHARACTERISTICS FOR MACHINES, ENGINES OR PUMPS OTHER THAN NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES
- F05C2203/00—Non-metallic inorganic materials
- F05C2203/08—Ceramics; Oxides
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- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Combustion & Propulsion (AREA)
- Compressors, Vaccum Pumps And Other Relevant Systems (AREA)
Abstract
A modified Ericsson cycle engine comprises an extended cycle reciprocating gas compressor 100,120, having a heat regenerator 140, which supplies compressed gas by near-isothermal compression to an extended cycle reciprocating gas expander 10,12, also having a heat regenerator 14, which expands the compressed gas by near-isothermal expansion to produce work, characterised in that more gas is used as heat transfer fluid in both the compressor and expander during the extra strokes of the respective extended cycles of the compressor and expander, and that during engine operation, heat addition to the engine is achieved by heating the heat transfer fluid entering the gas expander, the heat transfer fluid transferring heat to the heat regenerator in the gas expander for heating the compressed gas working fluid in the gas expander. The Ericsson engine of the invention has higher efficiency, fewer periphery components and less complicated start-up procedure than conventional Ericsson engines.
Description
- 1 - EXTENDED CYCLE RECIPROCATING ERICSSON ENGINE
Field of the invention
5 The present invention relates to modified Ericsson cycle engine.
Background of the invention
lo The ideal Ericsson cycle comprises ideal processes including isothermal compression, constant pressure heat addition, isothermal expansion and constant pressure heat rejection. The thermal efficiency of this cycle is the same as that of the Carnot cycle.
Various attempts have been made to devise a reciprocating Ericsson engine incorporating processes which approach the above ideal cycle as closely as possible, particularly isothermal compression and isothermal 20 expansion. The major problem arose from the combination of the engine cylinder and reciprocating piston requiring a smooth internal cylinder surface for the piston to move freely through the strokes. The smooth surface has poor heat transfer capability and this prevents heat from being 2s transferred efficiently between the cylinder and the working fluid inside the cylinder which is area-limited and rate-
limited because of poor internal mixing. Thus despite efforts to increase the heat transfer for cooling or heating the cylinder from the outside of the cylinder using fins, 30 fans, burners and heat exchange jackets etc. the heat flow is unavoidably hindered on the inside of the cylinder at the smooth internal surface before reaching the working fluid, making it inefficient and inadequate to support near-
isothermal compression or near-isothermal expansion.
In two co-pending British Patent Applications by the same applicant, GB 0300136.9 and GB 0300112.0, an extended
- 2 - cycle reciprocating gas compressor and an extended cycle reciprocating gas motor or expander are described capable of nearisothermal compression and near-isothermal expansion respectively. Both inventions operate according to a 5 reciprocating extended cycle of 4, 6 or more strokes, wherein the first two strokes are the working strokes of a conventional compressor or expander applied to a working fluid, and the remaining strokes are pairs of filling and emptying strokes using another heat transfer fluid for lo transferring heat out of or into the cylinder of the compressor or expander respectively. The compressor or expander also contains respective heat regenerators for absorbing or releasing heat directly from or to the working fluid while exchanging heat with the heat transfer fluid 5 during the extra strokes of the respective extended cycles.
The application of the extended cycles in the compressor and expander using the heat transfer fluid overcomes the heat transfer problem mentioned earlier by communicating directly between the inside and the outside of the cylinder in 20 alternate sequence and not relying on the heat transfer path across the smooth internal walls of the cylinder.
The present invention is aimed at achieving a practical reciprocating Ericsson cycle engine using the extended cycle 25 reciprocating compressor and expander in order to carry out the cycle processes as close as possible to the ideal Ericsson cycle.
Summary of the invention
According to the present invention, there is provided a modified Ericsson cycle engine comprising an extended cycle reciprocating gas compressor having a heat regenerator and supplying compressed gas working fluid by near-isothermal 35 compression to an extended cycle reciprocating gas expander also having a heat regenerator and expanding the compressed gas working fluid by near-isothermal expansion to produce
- 3 - work, characterized in that more gas is used as heat transfer fluid in both said gas compressor and gas expander during the extra strokes of the respective extended cycles of the compressor and expander, and that during engine 5 operation, heat addition to the engine is achieved by heating the heat transfer fluid entering the gas expander, and the heat transfer fluid transferring heat to the heat regenerator in the gas expander for heating the compressed gas working fluid in the gas expander.
The heat addition to the engine may be provided by an inlet heat exchanger heating the heat transfer fluid entering the gas expander. The heat exchanger may be heated by a fuel burning heater, a solar heating panel, an electric 5 heater, or other external heat source. Alternatively, the heat addition to the engine may be provided by burning fuel directly in the heat transfer fluid entering the gas expander, in the case where the heat transfer fluid is air.
20 In the invention, the heated heat transfer fluid heats the heat regenerator in the gas expander and brings the heat regenerator to a high temperature in the order of 1000 K.
The heat regenerator in turn heats the compressed gas working fluid in the gas expander to substantially the same 25 temperature which sets the upper temperature limit of the thermodynamic cycle.
After transferring heat to the heat regenerator inside the gas expander cylinder, the hot heat transfer fluid 30 discharged from the gas expander may be connected to a heating jacket surrounding the cylinder of the gas expander for heating the walls of the cylinder. It may further be connected to a heat exchanger for preheating the compressed gas working fluid from the gas compressor (recuperative 35 heating) before the compressed gas is admitted into the cylinder of the gas expander. Alternatively, the discharged heat transfer fluid may be connected directly to the
- 4 preheating heat exchanger without passing through the heating jacket.
Finally, the used heat transfer fluid leaving the s preheating heat exchanger after heating the compressed gas from the gas compressor could still be hot and may be connected back to transfer its remaining heat to the inlet heat exchanger or preheat the combustion air to the fuel burner. In this way, all additional heat is conserved lo within the extended cycle Ericsson engine.
The reciprocating engine of the present invention could achieve a nearideal Ericsson cycle by virtue of the near-
isothermal compression and near-isothermal expansion strokes 5 coupled with internal and recuperative heating of the working fluid brought about by the heat transfer fluid managing the heat during the extra strokes of the respective extended cycles of the gas compressor and gas expander.
Hence the invention may be called an extended cycle 20 reciprocating Ericsson engine.
Preferably, the engine comprises at least one gas compressor cylinder and at least one gas expander cylinder with their respective pistons connected to the same 25 crankshaft, and phased such that the start of the compression stroke of the gas compressor leads the start of the expansion stroke of the gas expander by at least two complete strokes of the gas expander. This allows sufficient residence time (i.e. at least one complete stroke 30 after the end of compression) for the working fluid compressed gas from the gas compressor to wait before entry to the gas expander thus picking up more pre-heat more thoroughly from the heat transfer fluid before entering the gas expander.
Preferably, one compressor cylinder is arranged to supply one expander cylinder as a discrete working pair with
at least one compressed gas pipe connecting in between uniquely provided for the working pair. The volume of the compressed gas pipe is sufficiently small for it to be included with the expansion cylinder volume of the gas 5 expander during the expansion stroke of the gas expander, such that the compressed gas expanding from the pipe directly into the gas expander cylinder during the full expansion stroke of the gas expander achieves a high expansion ratio relative to and including the volume of the 0 pipe. This has the advantage that the compressed gas expands immediately from the time the gas expander inlet valve is open, and the valve can stay open during the entire expansion stroke or longer, with the pipe still connected with the cylinder. On the other hand, this arrangement 15 would only work with one compressed gas pipe provided specifically for one working pair of compressor and expander, and precludes any manifold arrangement for the compressed gas pipe in a multicylinder engine shared between two or more sets of compressor and expander 20 cylinders.
The small volume of the said compressed gas pipe provided uniquely for each working pair of compressor and expander also has other parallel functions before the 25 compressed gas is finally expanded through the gas expander.
Firstly, this small volume pipe is the compressed gas reservoir receiving gas directly from the gas compressor for one compression stroke of the compressor so that this pipe volume effectively sets the pressure ratio of the 30 compressor. When taking into account the clearance volumes inside the compressor cylinder and the gas expander cylinder joining up with the pipe volume for each compression stroke and each expansion stroke respectively, the engine cycle will effectively have a larger expansion ratio than the 35 compression ratio making it even more efficient in extracting useful work from the working gas. Secondly, the compressed gas pipe also forms part of the heat exchanger
- 6 - for recuperative heating so that during the expansion stroke, the expanding gas within the pipe would continue to absorb heat from the heat exchanger while expanding into the cylinder. This is additional to the heat absorbed within 5 the cylinder from the heat regenerator thus achieving in the gas an expansion process which is near-isothermal. Thirdly, the recuperative heating of this fixed volume of pipe before the expansion stroke would result in heat addition to the compressed gas inside the pipe taking place at constant lo volume. This makes the present cycle in this case having attributes from both the Stirling cycle and the Ericsson cycle, the former having heat addition and heat rejection taking place at constant volume, the latter having heat addition and heat rejection taking place at constant 5 pressure, while the present cycle having heat addition at constant volume and heat rejection at constant pressure.
Finally because the small volume in the connecting pipe corresponds to the compressed gas volume from one 20 compression stroke of the gas compressor to be used in one expansion stroke of the gas expander within the same extended cycle of the engine, the dynamic response of the engine to changes in speed and load will be very fast. Also the start-up procedure of the engine will be quick and 25 simple.
The above arrangement of individual set of working pair of compressor and expander each with its own connecting compressed gas pipe also significantly relaxes the actuation 30 design specification of the gas expander inlet valve which
could have more than 180 crank angle opening period. This is to be contrasted with a conventional reciprocating gas expander where the gas expander inlet valve must be open and closed very quickly while the piston is still near TDC in 35 order that the compressed gas can enter the cylinder and expand with a high expansion ratio after the inlet valve is
- 7 closed. Such short valve opening period however poses severe problems to the design of the valve actuation system.
Finally, in a multi-cylinder engine of the present s invention with two or more sets of working pair of compressor and expander together with their respective connecting compressed gas pipes, it is possible to provide flow manifolds for collecting and distributing the working fluid and heat transfer fluid to various common components lo in the engine such as gas filter, fuel burning heater, heat addition heat exchanger and recuperative heat exchanger.
The present invention of the extended cycle Ericsson engine and the preferred embodiments not only have superior 5 performance compared with the previously known Ericsson cycle engines, but also eliminates a lot of the ancillary components necessary to make the previous engine operate efficiently, such as fins, fans, fan drives, afterburner etc disposed around the outside of the compression and expansion 20 cylinders in order to facilitate heat exchange through the walls of the cylinders with the gas inside. This gives the extended cycle Ericsson engine of the present invention very significant advantages over the conventional Ericsson cycle engine by virtue of higher efficiency, fewer periphery 25 components and less complicated start-up procedure, suitable for automotive, stationary and portable applications.
The extended cycle reciprocating Ericsson engine of the present invention also has advantages over the reciprocating 30 internal combustion engine, including very clean combustion giving very low exhaust emissions, higher efficiency, lower operating temperature and fewer ancillary parts such as valves and actuators, coolant circuit, coolant pump, thermostat, radiator, fuel injection equipment and ignition 35 system for internal combustion, catalytic converter etc. hence lower cost and better reliability.
- 8 The Ericsson engine of the present invention is suitable for application as an auxiliary power unit in an internal combustion engine driven vehicle using exhaust heat from the internal combustion engine to drive the Ericsson 5 engine for generating electricity to power some of the peripheral equipment on-board the vehicle.
The extended cycle reciprocating Ericsson engine of the present invention is also suitable for application as a heat lo and power system using the heat transfer fluid from the Ericsson engine to heat an environmental heating system while generating electricity to power lights and appliances.
Brief description of the drawing
The invention will now be described further, by way of example, with reference to the accompany drawings in which Figure 1 shows a schematic view of a modified 20 Ericsson cycle engine of the present invention with air as working fluid and heat transfer fluid, operating in an open cycle, Figure 2 shows a schematic view similar to Figure 1 of an alternative embodiment of a modified Ericsson 25 cycle engine of the present invention, with another gas as working fluid and heat transfer fluid, operating in a closed cycle, and Figure 3 shows a schematic view similar to Figure 1 of a further alternative embodiment of a modified 30 Ericsson cycle engine of the present invention, with air as the working fluid and heat transfer fluid, heated by burning fuel directly in the heat transfer fluid.
Detailed description of the preferred embodiment
In Figure 1, The left hand side of the drawing shows a reciprocating air compressor comprising at least one
- 9 - cylinder 100 having a variable volume defined by a reciprocating piston 120 which draws ambient air into the cylinder 100 during the induction stroke and compresses the air to a high pressure before releasing it through a non 5 return valve 160 to a compressed air pipe 30 during the compression stroke. The reciprocating air compressor is further equipped to operate according to an extended cycle comprising after the said induction and compression strokes, at least one pair of extra strokes each pair consisting of a lo filling stroke in which more ambient air serving as heat transfer fluid is drawn by the piston 120 (as shown by the solid line arrow) into the cylinder 100 to fill the cylinder 100 followed immediately by an emptying stroke in which the filled air is expelled by the piston 120 (as shown by the 5 chain-dashed arrow) out of the cylinder 100. In use, the filled air cools the cylinder 100 and piston 120 and lowers the air compressor temperature close to the temperature of the ambient air during the extra strokes, before the extended cycle is repeated with the working fluid of fresh 20 ambient air inducted into the cylinder 100 and compressed during the next compression stroke.
An open matrix heat regenerator 140 constructed in fine mesh or thin wall cell structure of high heat capacity material is also provided occupying the clearance space in the cylinder 100 and in intimate thermal contact with the air inside the cylinder 100. The heat regenerator 140 serves efficiently to absorb and store heat from the compressed air during the compression stroke, and to release 30 the stored heat to the filled air during the extra filling and emptying strokes of the extended cycle.
The compressor drawing shows the piston position during a filling stroke of the extended cycle of the compressor 35 when ambient air is drawn into the cylinder 100 through a one-way valve 220 along a filling port 200 controlled by an opened filling valve 180. The filling air passes through
- 10 the open matrix of the heat regenerator 140 and rapidly attains equilibrium temperature with the heat regenerator 140. 5 The function of the heat regenerator 140 is to absorb or release heat to the air passing through it depending on the initial temperature of the air being hotter or colder than the heat regenerator 140. Because the heat regenerator 140 has a high heat capacity, it can maintain a stable mean lo temperature with only a small temperature variation up or down depending on the direction of heat transfer with the air passing through it, and because it has a very large heat transfer surface area, it can rapidly bring the air temperature close to the matrix mean temperature as the air 5 exchanges heat with the matrix whatever is the initial temperature of the air.
In the compressor drawing, ambient air is used as heat transfer fluid to transfer heat away from the cylinder 100 20 and piston 120 and the heat regenerator 140 and lower the temperature of the cylinder 100 and heat regenerator 140 close to the temperature of the ambient air during the extra filling and emptying strokes of the extended cycle. This sets the lower temperature limit of the thermodynamic cycle.
5 In the subsequent compression stroke of the cycle, the air working fluid is cooled progressively by the heat regenerator 140 while being compressed, and stays at substantially the same temperature as the heat regenerator 140, thus achieving a compression process which is near 30 isothermal.
The air flows in and out of the cylinder 100 during the various strokes of the extended cycle may be programmed by appropriate timed valves driven by mechanical, electrical or 35 hydraulic actuators and controlling the flows through corresponding ports in the cylinder 100.
I - 11
In the compressor drawing, the same intake valve 180 and port 200 for the induction stroke is used as the filling and emptying valve 180 and port 200 for the extra strokes, thus bringing the air in and out of the cylinder 100 along a 5 common passage 200 with the intake valve 180 timed to remain open during the extra and induction strokes, and to close only during the compression stroke. In this case, the intake valve 180 may conveniently be actuated by a cam (not shown) driven at 1/2 compressor speed if the extended cycle lo is 4 strokes, or 1/3 compressor speed if the extended cycle is 6 strokes.
In the compressor drawing, additional respective one-
way valves 220, 240 are provided in the inlet and outlet 5 openings of the common passage 200 to the outside of the compressor, arranged such that fresh ambient air is drawn into the passage 200 only through the inlet one-way valve 220 and hot heat transfer air is expelled out of the passage 200 only through the outlet one-way valve 240. This 20 expelled heat transfer air is then passed to the air expander to be used as heat transfer fluid for the air expander. Moving to the right hand side of the drawing in Figure 25 1, it shows a reciprocating air expander comprising a cylinder 10 having a variable volume defined by a reciprocating piston 12 which produces work when a predetermined quantity of compressed air supplied from the compressed air pipe 30 is admitted into the cylinder 10 and 30 allowed to expand against the piston 12 to produce power during the expansion stroke, and the expanded air is subsequently expelled from the cylinder 10 displaced by the piston 12 during the exhaust stroke. The reciprocating air expander is further equipped to operate according to an 35 extended cycle comprising after the said expansion and exhaust strokes, at least one pair of extra strokes each pair consisting of a filling stroke in which the hot heat
transfer air expelled through the outlet one-way valve 240 of the compressor is drawn by the piston 12 (as shown by the chain-dashed arrows) into the cylinder 10 at substantially ambient pressure to fill the cylinder 10 followed 5 immediately by an emptying stroke in which the filled air is expelled by the piston 12 at substantially ambient pressure out of the cylinder 10. In use, the hot heat transfer air heats the cylinder 10 and piston 12 and raises the air expander temperature close to the temperature of the filled lo air during the extra strokes, before the extended cycle is repeated with the working fluid of fresh compressed air admitted into the cylinder 10 during the next expansion stroke. An open matrix heat regenerator 14 constructed in fine mesh or thin wall cell structure of high heat capacity material is also provided occupying the clearance space in the cylinder 10 and in intimate thermal contact with the air inside the cylinder 10. The heat regenerator 14 serves 20 efficiently to absorb and store heat from the filled hot air (heat transfer fluid) during the extra filling and emptying strokes of the extended cycle, and to release the stored heat to the expanding air (working fluid) during the next expansion stroke.
The expander drawing shows the piston position during a filling stroke of the extended cycle of the gas expander when hot heat transfer air from the outlet one-way valve 240 of the compressor is drawn into the cylinder 10 of the air 30 expander through a one-way valve 22 along a filling port 20 controlled by an opened filling valve 18. The filling air passes through the open matrix of the heat regenerator 14 and rapidly attains equilibrium temperature with the heat regenerator 14.
The function of the heat regenerator 14 is to absorb or release heat to the air passing through it depending on the
- 13 initial temperature of the air being hotter or colder than the heat regenerator 14. Because the heat regenerator 14 has a high heat capacity, it can maintain a stable mean temperature with only a small temperature variation up or 5 down depending on the direction of heat transfer with the air passing through it, and because it has a very large heat transfer surface area, it can rapidly bring the air temperature close to the matrix mean temperature as the air exchanges heat with the matrix whatever is the initial lo temperature of the air.
In the expander drawing, the hot air from the compressor is used as heat transfer fluid in the expander to transfer external heat to the cylinder 10 and piston 12 and the heat regenerator 14 and raise the temperature of the cylinder 10 and heat regenerator 14 close to the temperature of the hot air during the extra filling and emptying strokes of the extended cycle. In the following expansion stroke of the cycle, the working fluid compressed air from the pipe 30 20 is admitted into the cylinder 10 and allowed to expand (and potentially cool) while producing work, but the expanding air will be heated progressively by the heat regenerator 14 and stay at substantially the same temperature as the heat regenerator 14, thus achieving an expansion process which is 25 near-isothermal.
The air flows in and out of the cylinder 10 during the various strokes of the extended cycle may be programmed by appropriate timed valves driven by mechanical, electrical or 30 hydraulic actuators and controlling the flows through corresponding ports in the cylinder 10.
In the expander drawing, the same exhaust valve 18 and port 20 for the exhaust stroke is used as the filling and 3s emptying valve 18 and port 20 for the extra strokes, thus bringing the heat transfer air and expanded air in and out of the cylinder 10 along a common passage 20 with the
- 14 -
! exhaust valve 18 timed to remain open during the exhaust and extra strokes, and to close only during the expansion stroke. In this case, the exhaust valve 18 may conveniently be actuated by a cam (not shown) driven at 1/2 expander 5 speed if the extended cycle is 4 strokes, or 1/3 expander speed if the extended cycle is 6 strokes.
In the expander drawing, additional respective one-way valves 22, 24 are provided in the inlet and outlet openings 0 of the common passage 20 to the outside of the expander, arranged such that hot heat transfer air from the compressor is drawn into the passage 20 only through the inlet one-way valve 22 and the expanded working fluid air and used heat transfer air are expelled out of the passage 20 only through 15 the outlet one-way valve 24.
In so far described, the working temperature of the air expander and the heat regenerator 14 inside it are at substantially ambient temperature which will be insufficient 20 to sustain the thermodynamic cycle. In Figure 1, a fuel burning heater 40 heats the heat transfer air entering the cylinder 10 through an inlet heat exchanger 34 during the extra filling stroke of the extended cycle. This constitutes the external heat addition to the Ericsson cycle 25 engine of the present invention which is achieved by heating the heat transfer fluid entering the air expander, and the heat transfer fluid transferring heat to the heat regenerator 14 in the air expander for heating the compressed air working fluid in the air expander.
In Figure 1, the heated heat transfer fluid heats the heat regenerator 14 in the air expander and brings the heat regenerator 14 to a high temperature in the order of 1000 K.
The heat regenerator 14 in turn heats the compressed air 35 working fluid in the air expander to substantially the same temperature which sets the upper temperature limit of the thermodynamic cycle. Obviously, the heat regenerator 14,
- 15 the exhaust valve 18 and the inlet and outlet one-way valves 22, 24 should be made of suitable material such as ceramic or titanium, capable of withstanding the high operating temperature. In Figure 1, after transferring heat to the heat regenerator 14 inside the expander cylinder 10, the expelled heat transfer air from the outlet one-way valve 24 is still hot and is connected to a heating jacket 36 surrounding the lo cylinder of the air expander for heating the walls of the cylinder 10. From there the expelled air is further connected to a heat exchanger 38 for preheating the compressed air working fluid in the compressed air pipe 30 (recuperative heating) before the compressed air is admitted 5 into the cylinder 10.
The expelled heat transfer air leaving the preheating heat exchanger 38 after heating the compressed air could still be hot and may be connected back to transfer its 20 remaining heat to the inlet heat exchanger 34 by preheating the combustion air to the fuel burner 40 (as shown by the dashed arrows). In this way, all additional heat is conserved within the extended cycle Ericsson engine.
25 Moving to the complete drawing in Figure 1 with the air compressor, air expander and fuel burner constituting the extended cycle Ericsson engine, the engine comprises at least one air compressor cylinder 100 and at least one air expander cylinder 10 with their respective pistons 120, 12 30 connected to the same crankshaft, and phased such that the start of the compression stroke of the air compressor leads the start of the expansion stroke of the air expander by at least two complete strokes of the air expander. In the drawing, the compressor is shown leading by three complete 35 strokes of the air expander where the compressor is at its filling stroke which is one stroke behind the compression stroke, and the expander is also at its filling stroke which
- 16 is two strokes ahead of the next expansion stroke. This allows sufficient residence time (i.e. two complete strokes after the end of compression) for the compressed air from the air compressor to wait before entry to the air expander 5 thus picking up more pre-heat more thoroughlyfrom the preheating heat exchanger 38 before entering the air expander. In Figure 1, one compressor cylinder 100 is arranged to lo supply one expander cylinder 10 as a discrete working pair with at least one compressed air pipe 30 connecting in between uniquely provided for the working pair. The volume of the compressed air pipe 30 is sufficiently small for it to be included with the expansion cylinder volume of the air 5 expander during the expansion stroke of the air expander, such that the compressed air expanding from the pipe 30 directly into the air expander cylinder 10 during the full expansion stroke of the air expander achieves a high expansion ratio relative to and including the volume of the 20 pipe 30. This has the advantage that the compressed air expands immediately from the time the air expander inlet valve 28 is open, and the valve 28 can stay open during the entire expansion stroke or longer, with the pipe 30 still connected with the cylinder 10. This significantly relaxes 25 the actuation design specification of the air expander inlet
valve 28 which could have more than 180 crank angle opening period. The small volume of the compressed air pipe 30 provided 30 uniquely for each working pair of compressor and expander also has other parallel functions before the compressed air is finally expanded through the air expander. Firstly, this small volume pipe 30 is the compressed air reservoir receiving air directly from the air compressor for one 35 compression stroke of the compressor so that this pipe volume effectively sets the pressure ratio of the compressor. When taking into account the clearance volumes
- 17 inside the compressor cylinder and the expander cylinder joining up with the pipe volume for each compression stroke and each expansion stroke respectively, the engine cycle will effectively have a larger expansion ratio than the 5 compression ratio making it even more efficient in extracting useful work from the working fluid. Secondly, the compressed air pipe 30 also forms part of the heat exchanger 38 for recuperative heating so that during the expansion stroke, the expanding air within the pipe 30 would lo continue to absorb heat from the heat exchanger 38 while expanding into the cylinder 10. This is additional to the heat absorbed within the cylinder 10 from the heat regenerator 14 thus achieving in the air working fluid an expansion process which is near-isothermal. Thirdly, the 5 recuperative heating mentioned earlier of this fixed volume of pipe 30 would result in heat addition to the compressed air inside the pipe 30 taking place at constant volume.
This makes the present cycle in this case having attributes from both the Stirling cycle and the Ericsson cycle, the 20 former having heat addition and heat rejection taking place at constant volume, the latter having heat addition and heat rejection taking place at constant pressure, while the present cycle having heat addition at constant volume and heat rejection at constant pressure.
Finally because the small volume in the connecting pipe 30 corresponds to the compressed air volume from one compression stroke of the air compressor to be used in one expansion stroke of the air expander within the same 30 extended cycle of the engine, the dynamic response of the engine to changes in speed and load will be very fast. Also the start-up procedure of the engine will be quick and simple. 3s Figure 2 shows an alternative embodiment of the present invention in which the working fluid and heat transfer fluid is another gas of low density and high thermal conductivity
- 18 such as hydrogen or helium, sealed in a closed cycle system.
In this case, the expelled gas from the expander is connected back to the inlet one-way valve 220 of the compressor (as shown by the dashed arrows) via a low 5 temperature heat exchanger 280 which sets the lower temperature limit of the thermodynamic cycle.
Figure 3 shows a further alternative embodiment of the present invention in which the work fluid and heat transfer lo fluid is air similar to Figure 1, but the heat addition is provided by a fuel burner 42 burning fuel directly in the heat transfer fluid air entering the expander. The burnt heat transfer gas and the expanded working fluid air are passed through the preheating heat exchanger 38 before they 5 are finally discharged to atmosphere (as shown by the solid line arrow).
The present invention of the extended cycle Ericsson engine and the various embodiments not only have superior 20 performance compared with the previously known Ericsson cycle engines, but also eliminates a lot of the ancillary components necessary to make the previous engine operate efficiently, such as fins, fans, fan drives, afterburner etc disposed around the outside of the compression and expansion 25 cylinders in order to facilitate heat exchange through the walls of the cylinders with the air inside. This gives the extended cycle Ericsson engine of the present invention very significant advantages over the conventional Ericsson cycle engine by virtue of higher efficiency, fewer periphery 30 components and less complicated start-up procedure, suitable for automotive, stationary and portable applications.
The extended cycle reciprocating Ericsson engine of the present invention also has advantages over the reciprocating 35 internal combustion engine, including very clean combustion giving very low exhaust emissions, higher efficiency, lower operating temperature and fewer ancillary parts such as
I - 19
valves and actuators, coolant circuit, coolant pump, thermostat, radiator, fuel injection equipment and ignition system for internal combustion, catalytic converter etc. hence lower cost and better reliability.
The Ericsson engine of the present invention is suitable for application as an auxiliary power unit in an internal combustion engine driven vehicle, using exhaust gas heat from the internal combustion engine to drive the lo Ericsson engine for generating electricity to power peripheral equipment on-board the vehicle.
The extended cycle reciprocating Ericsson engine of the present invention is also suitable for application as a heat 5 and power system using the heat transfer fluid from the Ericsson engine to heat an environmental heating system while generating electricity to power lights and appliances.
Claims (17)
1. A modified Ericsson cycle engine comprising an extended cycle reciprocating gas compressor having a heat 5 regenerator and supplying compressed gas working fluid by near-isothermal compression to an extended cycle reciprocating gas expander also having a heat regenerator and expanding the compressed gas working fluid by near-
isothermal expansion to produce work, characterized in that lo more gas is used as heat transfer fluid in both said gas compressor and gas expander during the extra strokes of the respective extended cycles of the compressor and expander, and that during engine operation, heat addition to the engine is achieved by heating the heat transfer fluid 5 entering the gas expander, and the heat transfer fluid transferring heat to the heat regenerator in the gas expander for heating the compressed gas working fluid in the gas expander.
20
2. A modified Ericsson cycle engine as claimed in claim 1, wherein the heat addition to the engine is provided by an inlet heat exchanger heating the heat transfer fluid entering the gas expander, the heat exchanger being heated by a fuel burning heater, a solar heating panel, an electric 25 heater, or other external heat source, which sets the upper temperature limit of the thermodynamic cycle.
3. A modified Ericsson cycle engine as claimed in claim 1 or 2, wherein the heat transfer fluid drawn into and 30 later discharged from the gas compressor during the extra strokes of the gas compressor is connected to be drawn into and later discharged from the gas expander during the extra strokes of the gas expander.
35
4. A modified Ericsson cycle engine as claimed in any one of claims 1 to 3, wherein the heated heat transfer fluid drawn into and later discharged from the gas expander is
- 21 connected to a heating jacket surrounding the cylinder of the gas expander for heating the walls of the cylinder.
5. A modified Ericsson cycle engine as claimed in any 5 preceding claim, wherein the heated heat transfer fluid drawn into and later discharged from the gas expander is connected to a preheating heat exchanger for preheating the compressed gas working fluid from the gas compressor (recuperative heating) before the compressed gas is admitted lo into the cylinder of the gas expander.
6. A modified Ericsson cycle engine as claimed in claim 5 and 2, wherein the used heat transfer fluid and working fluid leaving the gas expander and the preheating 5 heat exchanger is connected to transfer its remaining heat to the inlet heat exchanger of the gas expander before they are discharged to the atmosphere.
7. A modified Ericsson cycle engine as claimed in any 20 one of claims 1 to 5, wherein the working fluid and heat transfer fluid is a gas sealed in a closed cycle system, and wherein all the used fluid leaving the gas expander and the preheating heat exchanger is connected back to the inlet of the gas compressor via a low temperature heat exchanger 2s which sets the lower temperature limit of the thermodynamic cycle.
8. A modified Ericsson cycle engine as claimed in claim 1 and any one of claims 3 to 6, wherein the working 30 fluid and heat transfer fluid is air and the heat addition to the engine is provided by a fuel burner burning fuel directly in the heat transfer fluid entering the gas expander which sets the upper temperature limit of the thermodynamic cycle.
9. A modified Ericsson cycle engine as claimed in any preceding claim, wherein the engine comprises at least one
- 22 l i gas compressor cylinder and at least one gas expander cylinder with their respective pistons connected to the same crankshaft, and phased such that the start of the compression stroke of the gas compressor leads the start of 5 the expansion stroke of the gas expander by at least two complete strokes of the gas expander.
10. A modified Ericsson cycle engine as claimed in any preceding claim, wherein one compressor cylinder is arranged lo to supply one expander cylinder as a discrete working pair with at least one compressed gas pipe connecting in between uniquely provided for the working pair.
11. A modified Ericsson cycle engine as claimed in 5 claim 10, wherein the volume of the compressed gas pipe corresponds to the compressed gas volume from one compression stroke of the gas compressor to be used in one expansion stroke of the gas expander within the same extended cycle of the said engine.
12. A modified Ericsson cycle engine as claimed in claim 10, wherein the volume of the compressed gas pipe is sufficiently small for it to be included with the expansion cylinder volume of the gas expander during the expansion 25 stroke of the gas expander, such that the compressed gas expanding from the pipe directly into the gas expander cylinder during the full expansion stroke of the gas expander achieves a high expansion ratio relative to and including the volume of the pipe.
13. A modified Ericsson cycle engine as claimed in claims 12 and 5, wherein the compressed gas pipe forms part of the preheating heat exchanger for heating the compressed gas inside the pipe with the heat transfer fluid discharged 35 from the gas expander.
- 23
14. A modified Ericsson cycle engine as claimed in any preceding claim, operating in conjunction with an internal combustion engine and using the exhaust gas heat from the internal combustion engine to drive the said Ericsson cycle 5 engine.
15. A modified Ericsson cycle engine as claimed in claim 14, wherein the said engine operates to generate electricity for powering peripheral equipment on-board an lo internal combustion engine driven vehicle.
16. A modified Ericsson cycle engine as claimed in any one of claims 1 to 13, operating in conjunction with an environmental heating system and using the heat transfer 5 fluid from the said engine to heat the said heating system.
17. A modified Ericsson cycle engine as claimed in claim 16, wherein the said engine operates to generate electricity for powering lights and appliances.
Priority Applications (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB0302808A GB2396887A (en) | 2003-01-06 | 2003-02-07 | Extended cycle reciprocating Stirling engine |
| US10/540,055 US20060248886A1 (en) | 2002-12-24 | 2003-12-23 | Isothermal reciprocating machines |
| AU2003290370A AU2003290370A1 (en) | 2002-12-24 | 2003-12-23 | Isothermal reciprocating machines |
| PCT/GB2003/005713 WO2004059155A1 (en) | 2002-12-24 | 2003-12-23 | Isothermal reciprocating machines |
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB0230132A GB0230132D0 (en) | 2002-12-24 | 2002-12-24 | Isothermal reciprocating gas motor |
| GB0300134A GB0300134D0 (en) | 2002-12-24 | 2003-01-06 | Extended cycle reciprocating ericsson engine |
| GB0300615A GB0300615D0 (en) | 2002-12-24 | 2003-01-13 | Extended cycle reciprocating ericsson engine |
| GB0301215A GB0301215D0 (en) | 2002-12-24 | 2003-01-20 | Extended cycle reciprocating ericsson engine |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB0302342D0 GB0302342D0 (en) | 2003-03-05 |
| GB2396664A true GB2396664A (en) | 2004-06-30 |
Family
ID=27448026
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB0302342A Withdrawn GB2396664A (en) | 2002-12-24 | 2003-02-03 | Extended cycle reciprocating Ericsson cycle engine |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2396664A (en) |
Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103470397A (en) * | 2012-08-14 | 2013-12-25 | 摩尔动力(北京)技术股份有限公司 | Cold pressing unit engine |
| US9057265B2 (en) | 2010-03-01 | 2015-06-16 | Bright Energy Storage Technologies LLP. | Rotary compressor-expander systems and associated methods of use and manufacture |
| CN105508078A (en) * | 2016-01-19 | 2016-04-20 | 江苏源之翼电气有限公司 | Efficient hot air engine |
| US9551292B2 (en) | 2011-06-28 | 2017-01-24 | Bright Energy Storage Technologies, Llp | Semi-isothermal compression engines with separate combustors and expanders, and associated systems and methods |
| CN106499542A (en) * | 2016-12-16 | 2017-03-15 | 江苏源之翼电气有限公司 | The efficient thermomotor of closure door formula |
| CZ308724B6 (en) * | 2020-06-23 | 2021-03-24 | Oto Mušálek | Stirling engine |
| WO2022082839A1 (en) * | 2020-10-20 | 2022-04-28 | 朱国钧 | Engine for oil-free aerodynamic power generation |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4133172A (en) * | 1977-08-03 | 1979-01-09 | General Motors Corporation | Modified Ericsson cycle engine |
| US5894729A (en) * | 1996-10-21 | 1999-04-20 | Proeschel; Richard A. | Afterburning ericsson cycle engine |
| US6085506A (en) * | 1993-07-08 | 2000-07-11 | Megadyne Inc. | Quiet external combustion lawn mower |
-
2003
- 2003-02-03 GB GB0302342A patent/GB2396664A/en not_active Withdrawn
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4133172A (en) * | 1977-08-03 | 1979-01-09 | General Motors Corporation | Modified Ericsson cycle engine |
| US6085506A (en) * | 1993-07-08 | 2000-07-11 | Megadyne Inc. | Quiet external combustion lawn mower |
| US5894729A (en) * | 1996-10-21 | 1999-04-20 | Proeschel; Richard A. | Afterburning ericsson cycle engine |
Cited By (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US9057265B2 (en) | 2010-03-01 | 2015-06-16 | Bright Energy Storage Technologies LLP. | Rotary compressor-expander systems and associated methods of use and manufacture |
| US9062548B2 (en) | 2010-03-01 | 2015-06-23 | Bright Energy Storage Technologies, Llp | Rotary compressor-expander systems and associated methods of use and manufacture, including integral heat exchanger systems |
| US9551292B2 (en) | 2011-06-28 | 2017-01-24 | Bright Energy Storage Technologies, Llp | Semi-isothermal compression engines with separate combustors and expanders, and associated systems and methods |
| CN103470397A (en) * | 2012-08-14 | 2013-12-25 | 摩尔动力(北京)技术股份有限公司 | Cold pressing unit engine |
| CN105508078A (en) * | 2016-01-19 | 2016-04-20 | 江苏源之翼电气有限公司 | Efficient hot air engine |
| CN105508078B (en) * | 2016-01-19 | 2017-04-12 | 江苏源之翼电气有限公司 | Efficient hot air engine |
| CN106499542A (en) * | 2016-12-16 | 2017-03-15 | 江苏源之翼电气有限公司 | The efficient thermomotor of closure door formula |
| CZ308724B6 (en) * | 2020-06-23 | 2021-03-24 | Oto Mušálek | Stirling engine |
| WO2022082839A1 (en) * | 2020-10-20 | 2022-04-28 | 朱国钧 | Engine for oil-free aerodynamic power generation |
Also Published As
| Publication number | Publication date |
|---|---|
| GB0302342D0 (en) | 2003-03-05 |
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