GB1581749A

GB1581749A - Stirling cycle heat engines

Info

Publication number: GB1581749A
Application number: GB239077A
Authority: GB
Original assignee: UK Atomic Energy Authority
Current assignee: UK Atomic Energy Authority
Priority date: 1977-01-20
Filing date: 1977-01-20
Publication date: 1980-12-17

Description

(54) IMPROVEMENTS IN OR RELATING TO STIRLING CYCLE HEAT ENGINES (71) We, UNITED KINGDOM ATO MIC ENERGY AUTHORITY of 11 Charles II Street, London, SW1Y 4QP, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to a Stirling cycle heat engine having hot and cold variable volume chambers intercommunicating through a regenerator and adapted to contain a working gas, a liquid system in which liquid in at least one of the chambers is displaceable for varying the gas volume in the chambers, and means to derive an output from displacement of the liquid. An example of such a Stirling cycle engine is described in co-pending application No.

14911/76 (Serial No. 1581748) which in Claim 1 describes a Stirling cycle engine comprising hot and cold variable volume chambers intercommunicating through a regenerator and adapted to contain a working gas, a liquid system in which liquid in at least one of the chambers is displaceable for varying the gas volume in the chambers, and means to derive an output from the engine, wherein the hot and cold variable volume chambers are arranged one within the other and are thermally insulated from one another.

According to one aspect of the present invention, in a Stirling cycle heat engine having hot and cold variable volume chambers intercommunicating through a regenerator and adapted to contain a working gas a liquid system in which liquid in at least one of the chambers is displaceable for varying the gas volume in the chambers, and means to derive an output from displacement of the liquid, the output means is resiliently biased in a manner to resist said displacement so as to enable the engine to operate at a predetermined mean pressure of the working gas.

According to another aspect of the present invention, in a Stirling cycle heat engine having hot and cold variable volume chambers intercommunicating through a regenerator and adapted to contain a working gas, a liquid system in which liquid in, at least one of the chambers is displaceable for varying the gas volume in the chambers, and means to derive an output from displacement of the liquid, the output means is resiliently biased in a manner to assist said displacement and enable the engine to operate at a predetermined mean pressure of the working gas.

Preferably, the output means comprises a flexible obturator means, and the resilient bias is provided by gas pressure. The obturator means may be adapted to provide a portion of a wall of a variable volume pumping chamber of a pumping means.

The resiliently biased output means enables the engine to be pressurised by use of a higher mean gas pressure with a consequent higher output head from the engine compared with that of a similar but unpressurised engine.

The invention will now be described by way of example only with reference to the accompanying drawings in which: Figure 1 shows in median section a diagrammatic representation of a Stirling cycle heat engine; Figure 2 shows to an enlarged scale that portion of Figure 1 within the circle 'it'; and Figure 3 shows in fragmentary median section. and to an enlarged scale, an alternative output means incorporated in the engine of Figure 1.

Referring now to Figure 1, the single Fluidyne (Registered Trade Mark) Stirling cycle heat engine of Figure 1 is similar to the engine of Figure 1 of the afore-mentioned co-pending application No. 14911/76 (Serial No. 1581748), to which reference is directed. The engine is of circular form in section, and comprises an aluminium cylindrical closed tank 1 having a chamber la, partially filled with a liquid such as mineral oil, and having a flow barrier 2 of hollow cylindrical form disposed substantially concentrically therein, the flow barrier 2 being formed by a thermal insulating core 2a of magnesia supported by an aluminium liner 2b.

The flow barrier is made shorter than the inside height of the tank 1 so as to provide a space for a regenerator 3 between the top of the barrier 2 and the top of the tank 1, and leave a port for liquid in the form of a flow space 5 between the bottom of the barrier 2 and the base 6 of the tank 1.

The flow barrier 2 divides the tank 1 into an outer annular chamber 10 and an inner cylindrical chamber 11 communicating through the regenerator 3 and the flow space 5. The space above the liquid is filled with a working gas such as air, hydrogen or helium at a predetermined mean pressure, and provides a cold chamber 12 in the annular chamber 10 and a hot chamber 13 in the inner chamber 11 of the engine.

An outlet 15 is connected at one end to the base of the tank 1 and is U-shaped so as to extend upwardly parallel to the chambers 10 and 11 respectively. The other end 15a of the output tube 15 is closed and of reduced diameter, and means are provided at the closed end l5a for deriving an output from the displacement of the liquid in the tank 1 and shown in greater detail in Figure 2 to which reference is now made.

In Figure 2, flexible obturators in the form of two Philips Rollsock seals 101 and 102 respectively are disposed axially in series within the output tube 15 in opposed relationship to define a pumping space 106 therebetween, and are rigidly connected together by a rod 103 arranged to slide in a guide 104 held by spider arms 105 extending from the wall of the output tube 15. A gas such as air is trapped in the end space 107 defined between the closed end l5a of the output tube 15 and the adjacent Rollsock seal 102.

Each Rollsock seal 101 or 102 respectively comprises a flexible Neoprene or VITON (Registered Trade Mark) gaiter 101a or 1()2a respectively attached at one end to a piston portion lOIb or 1()2b respectively and at the other end thereof to the inside of the output tube 15 or closed end 15a respectively. Because of the difference in swept volume between the piston portion 101b and 102b during displacement thereof a change in volume is effected in the pumping space 106.

A branch tube 110 joined to the output tube 15 to connect with the pumping space 106, is connectable to a pump (not shown).

The pumping space 106 and branch tube 110 may contain either a gas, such as air, or a liquid, to operate the pump from volume changes in the pumping space 106 caused by displacement of the liquid from the tank 1, in operation of the engine, displacing the Rollsock seals 101 and 102.

The pressures of the liquid and gas acting on the Rollsock seals 101 and 102 respectively are not equal, the larger Rollsock seal 101 having a lower liquid pressure acting on it, but the forces (i.e. the pressure x the effective area of the Rollsock seals 101 and 102) acting on them are arranged to be equal as shown in Figure 2 in an equilibrium position of the engine so that two equal but opposite forces are acting on the rod 103.

Any change in pressure of the liquid acting on the larger Rollsock seal 101 from pressure changes in the working gas in the tank 1 during operation of the engine, creates a difference in the forces acting across the Rollsock seals 101 and 102 and therefore, causes displacement thereof.

In operation of the engine as explained more fully in British Patent Specification No. 1329567, and co-pending application No. 14911/76 (Serial No. 1581748), on heat being applied to the hot chamber 13 by a heat source (not shown) the gas therein expands causing oscillation of the liquid and oscillation of the gas betwen the cold and hot chambers 12 and 13 respetively through the regenerator 3, heat being extracted from the gas by the regenerator 3 when the gas flows towards the cold chamber 12 and absorbed from the regenerator 3 by the gas when it flows towards the hot chamber 13.

Displacement of the liquid in the tank 1 as a result of the pressure changes in the gas above the liquid causes corresponding displacement of the liquid in the output tube 15 and, therefore, upward displacement of the lower Rollsock seal 101 and the upper Rollsock seal 102. Because of the difference in cross-sectional area swept by the two Rollsock seals 101 and 102, the change in volume of the pumping space 106 causes displacement of liquid or gas from the pumping space 106 through the branch tube 110 to operate the pump.

Instead of being coupled to a pump, the gas or liquid in the pumping space 106 may be arranged, for example, to displace a diaphragm, another Rollsock seal, or a similar pressure sensitive device (not shown) to derive a direct mechanical output therefrom.

It will be understood that the Rollsock seals 101 and 102 may be replaced by devices capable of performing a similar function, and that alternative materials may be used in the construction of the engine as suggested in co-pending application No.

14911/76 (Serial No. 1581748).

The predetermined mean pressure of the gas in the space above the liquid in the tank 1 is selected to provide a desired output head from the engine, a mean gas pressure in the range 1 - 3 atmospheres being preferred, the pressure of the gas in the closed end 15a of the output tube 15 being correspondingly selected so as to balance the displacement of the Rollsock seals 101 and 102 against the aforesaid predetermined pressure.

The invention has been described in relation to the use of an output means at the end of the output tube 15 remote from the tank 1 since in this position it is more accessible for servicing, but if desired it can be incorporated elsewhere, for example, as shown in Figure 3 which also shows an alternative form of output means according to the invention.

Referring now to Figure 3, the base 6 of the tank 1 is provided with an internal standpipe 20 having an upper end 21 provided with a plurality of holes 22. A flexible obturator in the form of a diaphragm 23, for Neoprene or VITON (R.T.M.) reinforced with a rayon fabric, is clamped to the upper end 21 by an aluminium annular plate 24 using studs (not shown) welded to the upper end 21. A shouldered boss 28 of aluminium is bonded to the underside of the diaphragm 23 to provide an anchorage for one end of a compression spring 29 having a required resilience to urge the diaphragm 23 against the end 21. An outlet tube 30 containing a liquid such as water and having a flange 31 is secured to the outside of the base 6 of the tank 1 using studs (not shown) welded to the base 6, and a sealing gasket 32.The flange 31 extends across the end of the outlet tube 30 and is shaped to provide a central boss 35, for locating the other end of the spring 29 and has a plurality of holes 36 for fluid flow therethrough. The outlet tube 30 has an elbow portion 37 having an unequal outlet 38 which continues in the same manner as the outlet tube 15 on Figure 1 but does not have the arrangement of Rollsock seals as shown in Figure 2.

In operation, the diaphragm 23 is deflected downwardly when the force exerted by the pressure of the liquid in the tank l on the diaphragm 23 exceeds the predetermined pressure on it exerted by the spring 29, and causes a corresponding displacement of the liquid in the outlet tube 30 from which an output from the engine may be derived.

The position of the diaphragm 23 permits the use of two liquids having different properties, each selected for the function it has to perform. for example oil in the tank 1 and water in the output tube 30. or alternatively the diaphragm 23 may be directly coupled to a mechanical member (not shown) of a mechanical device for deriving an output.

The diaphragm 23 may be made from suitable alternative materials such as plastics or a metal, and alternative springs 29 may be used, for example, a flat spring bonded to the underside of the diaphragm 23.

The invention may be incorporated in alternative forms Stirling cycle heat engines, for example, the engines described in British Patent Specification No. 1,329,567 and co-pending applications Nos. 46797/75 (Serial No. 1568057) and 14911/76 (Serial No.

1581748).

It will be understood that although the invention has been described in relation to the use of an output means which is resiliently biased to resist the displacement of the liquid in the liquid system, the direction of the resilient bias may be reversed so that the bias assists the liquid displacement, for example, to enable a predetermined mean pressure of the working gas below atmospheric pressure to be used.

WHAT WE CLAIM IS: 1. A Stirling cycle heat engine having hot and cold variable chambers intercommuncating through a regenerator and adapted to contain a working gas, a liquid system in which liquid in at least one of the chambers is displaceable for varying the gas volume in the chambers, and means to derive an output from displacement of the liquid, wherein the output means is resiliently biased in a manner to resist said displacement so as to enable the engine to operate at a predetermined mean pressure of the working gas.

2. A Stirling cycle heat engine having hot and cold variable volume chambers intercommunicating through a regenerator and adapted to contain a working gas, a liquid system in which liquid in at least one of the chambers is displaceable for varying the gas volume in the chambers, and means to derive an output from displacement of the liquid, wherein the output means is resiliently biased in a manner to assist said displacement and enable the engine to operate at a predetermined mean pressure of the working gas.

3. An engine as claimed in Claim 1, wherein the predetermined mean pressure is 1 to 3 atmospheres.

4. An engine as claimed in Claim 2, wherein the predetermined mean pressure is below atmospheric pressure.

5. An engine as claimed in any one of the preceding Claims, wherein the output means comprises a flexible obturator means.

6. An engine as claimed in any one of the preceding Claims, wherein the resilient bias is provided by gas pressure.

7. An engine as claimed in any one of

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Claims

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The predetermined mean pressure of the gas in the space above the liquid in the tank 1 is selected to provide a desired output head from the engine, a mean gas pressure in the range 1 - 3 atmospheres being preferred, the pressure of the gas in the closed end 15a of the output tube 15 being correspondingly selected so as to balance the displacement of the Rollsock seals 101 and 102 against the aforesaid predetermined pressure.

The invention has been described in relation to the use of an output means at the end of the output tube 15 remote from the tank 1 since in this position it is more accessible for servicing, but if desired it can be incorporated elsewhere, for example, as shown in Figure 3 which also shows an alternative form of output means according to the invention.

Referring now to Figure 3, the base 6 of the tank 1 is provided with an internal standpipe 20 having an upper end 21 provided with a plurality of holes 22. A flexible obturator in the form of a diaphragm 23, for Neoprene or VITON (R.T.M.) reinforced with a rayon fabric, is clamped to the upper end 21 by an aluminium annular plate 24 using studs (not shown) welded to the upper end 21. A shouldered boss 28 of aluminium is bonded to the underside of the diaphragm 23 to provide an anchorage for one end of a compression spring 29 having a required resilience to urge the diaphragm 23 against the end 21. An outlet tube 30 containing a liquid such as water and having a flange 31 is secured to the outside of the base 6 of the tank 1 using studs (not shown) welded to the base 6, and a sealing gasket 32.The flange 31 extends across the end of the outlet tube 30 and is shaped to provide a central boss 35, for locating the other end of the spring 29 and has a plurality of holes 36 for fluid flow therethrough. The outlet tube 30 has an elbow portion 37 having an unequal outlet 38 which continues in the same manner as the outlet tube 15 on Figure 1 but does not have the arrangement of Rollsock seals as shown in Figure 2.

In operation, the diaphragm 23 is deflected downwardly when the force exerted by the pressure of the liquid in the tank l on the diaphragm 23 exceeds the predetermined pressure on it exerted by the spring 29, and causes a corresponding displacement of the liquid in the outlet tube 30 from which an output from the engine may be derived.

The position of the diaphragm 23 permits the use of two liquids having different properties, each selected for the function it has to perform. for example oil in the tank 1 and water in the output tube 30. or alternatively the diaphragm 23 may be directly coupled to a mechanical member (not shown) of a mechanical device for deriving an output.

The diaphragm 23 may be made from suitable alternative materials such as plastics or a metal, and alternative springs 29 may be used, for example, a flat spring bonded to the underside of the diaphragm 23.

The invention may be incorporated in alternative forms Stirling cycle heat engines, for example, the engines described in British Patent Specification No. 1,329,567 and co-pending applications Nos. 46797/75 (Serial No. 1568057) and 14911/76 (Serial No.

1581748).

It will be understood that although the invention has been described in relation to the use of an output means which is resiliently biased to resist the displacement of the liquid in the liquid system, the direction of the resilient bias may be reversed so that the bias assists the liquid displacement, for example, to enable a predetermined mean pressure of the working gas below atmospheric pressure to be used.

WHAT WE CLAIM IS: 1. A Stirling cycle heat engine having hot and cold variable chambers intercommuncating through a regenerator and adapted to contain a working gas, a liquid system in which liquid in at least one of the chambers is displaceable for varying the gas volume in the chambers, and means to derive an output from displacement of the liquid, wherein the output means is resiliently biased in a manner to resist said displacement so as to enable the engine to operate at a predetermined mean pressure of the working gas.
2. A Stirling cycle heat engine having hot and cold variable volume chambers intercommunicating through a regenerator and adapted to contain a working gas, a liquid system in which liquid in at least one of the chambers is displaceable for varying the gas volume in the chambers, and means to derive an output from displacement of the liquid, wherein the output means is resiliently biased in a manner to assist said displacement and enable the engine to operate at a predetermined mean pressure of the working gas.
3. An engine as claimed in Claim 1, wherein the predetermined mean pressure is 1 to 3 atmospheres.
4. An engine as claimed in Claim 2, wherein the predetermined mean pressure is below atmospheric pressure.
5. An engine as claimed in any one of the preceding Claims, wherein the output means comprises a flexible obturator means.
6. An engine as claimed in any one of the preceding Claims, wherein the resilient bias is provided by gas pressure.
7. An engine as claimed in any one of

Claims 1 to 5, wherein the resilient bias is provided by spring means.
8. An engine as claimed in Claim 5, wherein the obturator means is adapted to provide a portion of a wall of a variable volume pumping chamber of a pumping means.
9. An engine as claimed in Claim 8, wherein the obturator means comprises two flexible obturators of differing crosssectional areas disposed in series relationship and secured axially together so as to have the same axial displacement but differ ing swept volumes, and the variable volume pumping chamber is provided by the space between the obturators.
10. An engine as claimed in Claim 5, wherein the flexible obturator means is adapted on the output side thereof for connection to a mechanical member for driving a mechanical device from displacement of the obturator means.
11. An engine as claimed Claim 5, wherein the flexible obturator means is disposed in a duct and has the liquid system on one side thereof and another liquid on the output side thereof so as to provide an output from displacement of the another liquid.
12. An engine substantially as hereinbefore described with reference to Figures 1 and 2 of the accompanying drawings.
13. An engine substantially as hereinbefore described with reference to Figure 1 of the accompanying drawings as modified by Figure 3.

Reference has been directed in pursuance of section 9, subsection (1) of the Patents Act 1949, to patent No. 1329567