US3466867A

US3466867A - Hot gas engine with gas pressure control means

Info

Publication number: US3466867A
Application number: US690144A
Authority: US
Inventors: Roy H Brandes
Original assignee: Motors Liquidation Co
Current assignee: Motors Liquidation Co
Priority date: 1967-12-13
Filing date: 1967-12-13
Publication date: 1969-09-16
Anticipated expiration: 1986-09-16

Description

P 16, 1969 R. H. BRANDES 3,466,867 v HOT GAS ENGINE WITH GAS PRESSURE CONTROL MEANS Filed Dec. 13, 1967 HEATER STORAGE TAN K GAS 5:1 OMPRESSOR INVENTOR.

BY (30; A. Bram/es AT TOR N EY United States Patent O 3,466,867 HOT GAS ENGINE WITH GAS PRESSURE CONTROL MEANS Roy H. Brandes, Utica, Mich assignor to General Motors Corporation, Detroit, Mich, a corporation of Delaware Filed Dec. 13, 1967, Ser. No. 690,144 Int. Cl. F02g 1/04, 3/02 US. Cl. 60-24 11 Claims ABSTRACT OF THE DISCLOSURE BACKGROUND OF THE INVENTION This invention relates generally to external combustion hot gas engines and more specifically to means for controlling the gas pressure in such an engine.

It is known in the art relating to closed cycle hot gas engines operating, for example, on the Stirling cycle, to control the power output of such engines by varying the quantity of gas in the engine working space. It is also known, for efficiency purposes, to use as a working gas, a light gas such as hydrogen, and to provide pressure control means including a storage tank from which gas is supplied to the engine working space and to which gas is returned when it is exhausted from the engine working space. A compressor is used to return the gas from the engine working space to the storage tank.

One such gas pressure control arrangement is shown in United States patent application Ser. No. 522,553, Brandes. This arrangement, while being an improvement over certain prior arrangements, is similar to some of them in that its utilizes a single fill valve connecting the storage tank to both the engine working and butter spaces in combination with a pair of check valves which are used to prevent undesired bypassing of gas between the spaces.

While such an arrangement may operate satisfactorily, it has been found in practice that the pressure fluctuations in the working and buffer spaces have a deleterious efiect on the durability of the check valves so that they may begin to leak. This results in undesired bypassing of the working gas and a loss of engine efiiciency.

An additional characteristic of the above noted system is that the storage tank can never be exhausted below the lowest cyclic pressure found in the engine working and buffer spaces. As a result, it is not possible to use all the gas contained in a storage tank before it must be refilled or replaced.

SUMMARY OF THE INVENTION The invention also provides for a supply tank separate from the storage tank and means to transfer gas from the 3,456,867 Patented Sept. 16, 1969 "Ice supply tank to the storage tank so as to maintain the storage tank pressure above the desired minimum. The arrangement provides that this transfer is made by admitting gas from the supply tank to the inlet of the storage tank gas compressor so that the supply tank may be completely exhausted before it is replaced by a full tank of gas.

These and other advantages of the invention will be more readily apparent from the following description of a preferred embodiment of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS FIGURE 1 of the drawings illustrates a hot gas engine having gas pressure control means according to the present invention;

FIGURE 2 shows a portion of the gas pressure control means of FIGURE 1 showing the actuating means in position to exhaust gas from the engine working and buffer spaces for return to the storage tank; and

FIGURE 3 shows a portion of the gas pressure control means of FIGURE 1 showing the actuating means in position to transfer gas from the storage tank to the engine working and buffer spaces.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring more specifically to the drawing, numeral 10 generally indicates a hot gas engine having a cylinder 12 which is enclosed at its upper and lower ends. A power piston 14 and a displacer piston 16 are coaxially arranged to reciprocate in the cylinder in out of phase relationship as determined by the connection of coaxial connecting rods 18 and 20 with suitable mechanism (not shown). Power piston 14 divides the space within cylinder 12 into a working space 22 above the power piston and a buffer space 24 below the power piston. The displacer piston reciprocates completely Within the working space and separates it into two portions which are interconnected externally of the cylinder through a cooler 26, one or more regenerators 28 and a heater 30 all of which comprise portions of the working space and arranged in a conventional manner.

In the operation of the engine, working gas, such as hydrogen, is retained within the working space under a substantial pressure. The action of the power and displacer pistons provide for a cycle of operation in the working gas including compression, heating, expansion and cooling phases which result in a net work output to the power piston. In order to reduce mechanical loads on the operating mechanism, the buffer space 24 is also filled with compressed gas approximately equal to the working pressure but which varies in pressure in a cycle opposite to that of the gas in the working space.

In order to change the power output of the engine, means are provided for varying the quantity of gas in the working space by supplying gas thereto or exhausting gas therefrom. Since this variation changes the average working pressure level in the working space, the control means are arranged to transfer gas to and from the working and buffer spaces at the same time. In this way the desired relationship between the pressures in the two spaces is maintained.

As shown in the figure, the control system comprises a supporting member 32 which carries a working space fill valve 34, a buffer space fill valve 36, a buffer dump and bypass 38 and a dump valve 40. All the valves are illustrated as being spring biased ball elements actuated by rod-like actuators 42 although it should be understood that any suitable valve construction could be used. An actuating lever 44 pivotally mounted on support 32 engages the valve actuators 42 and is movable by the upward bias of a spring 46 opposed by a fluid actuated piston 48 reciprocably carried in a cylinder 50.

Fill valve 34 connects through a fill line 52 with the engine working space 22 while fill valve 36 connects through fill line 54 with the engine bulfer space 24. Both valves are joined by a line 56 and are supplied with gas through a line 58 connecting them with a fill limiting valve 60.

Valve 60 is illustrated as including a spring biased ball element 62 operable by a pressure actuated piston member 64. Of course, as in the case of the fill valves, any other suitable valve construction could be used. Valve 60 is arranged when open to connect line 58 with a supply line 66 leading from a Working gas supply tank 68. Tank 68 is connected to a gas compressor 70 through a line 72 and the gas compressor is, in turn, connected through lines 74 and 76 with a supply valve 78. The supply valve could be of any suitable type, but it is illustrated as being constructed similarly to the fill limiting valve 60 in that it contains a spring biased ball element 62 operable by a pressure actuated piston 64. When open, supply valve 78 connects line 76 with a supply tank 80 through a supply line 82. Coupling means 83 in the line provides for replacement of an empty supply tank with a full one. A pressure line 84 is also provided to connect the pressure in storage tank 68 to one side of the piston 64 of supply valve 78.

Lines 74 and 76 also connect the gas compressor with dump valve 40. The other side of this valve connects through lines 84 and 86 to the engine working space 22. Line 84 also connects with dump and bypass valve 38, the other side of which connects through line 88 with the engine buffer space 24.

Engine working pressure is transmitted to one side of piston 64 of the fill limiting valve 60 through a line 90 connecting the limiter valve 60 with the working pressure side of dump valve 40.

The operation of the above described system is as follows. When the engine working space contains the proper quantity of gas to maintain the working pressure at that for which the control is set, the system remains in a neutral position as shown in FIGURE 1 wherein all the fill, dump and bypass valves are closed.

If, however, it is desired to reduce the working pressure, and along with it the buffer pressure, a control m mber (not shown) increases the fluid pressure on piston 48 causing lever 44 to be pivoted downwardly as shown in FIGURE 2. This action opens valves 38 and 40, cansing the working and buffer spaces to be connected through valve 38 and

lines

86, 84 and 88 and permitting gas to fiow therefrom through valve 40 and lines 76 and 74 to the gas compressor 70. This gas is then pumped through line 72 to the working storage tank 68 until a sufiicient reduction in the working and buffer spaces is obtained at which time the control mechanism is returned to the neutral position of FIGURE 1 by action of the external control means (not shown). During the time the pressure reduction is taking place, engine power is reduced by the bypassing of gas through valve 38 between the working and butter spaces of the engine.

If now an increase in the engine working and buffer gas pressures is desired, the pressure acting on piston 48 is reduced, permitting lever 44 to pivot upwardly and open the fill valves 34 and 36 as shown in FIGURE 3. Assuming fill limiting valve 60 is open, this permits gas to flow from storage tank 68, through line 66, valve 60 and line 58 to fill valve 36. From this point, some of the gas passes through the valve 36 and line 54 to the butter space 24 and the rest passes through line 56, valve 34 and line 52 to the working space 22. When the pressure in the working and butter spaces reaches the desired value, the mechanism is again returned to the neutral position of FIGURE 1.

Should the pressure in the working space increase to a predetermined limit, the working pressure will be transmitted through line 90 to the piston 64 of the fill limiting valve 60, closing the valve and preventing the admission of further gas to the working and buffer spaces even though the control means has not yet returned to the neutral position.

In order for satisfactory operation of the above described portion of the system, the pressure in the working storage tank 68 must always be kept at a higher level than the highest pressure reached in either the working or buffer spaces of the engine. If this were not the case, undesired bypassing of gas between the working and buffer spaces could occur when the engine is being filled due to the connection of these spaces through the fill valves 34 and 36. In order to avoid this, the pressure in the working storage tank 68 is transmitted through line 84 to one side of piston 64 of the supply valve 78. When the storage tank pressure drops to a predetermined minimum, the piston moves rightwardly, Opening the valve and permitting gas from supply tank to pass through lines 82, 76 and 74 to the inlet of the gas compressor by which it is pumped into the storage tank. Gas flow from the supply tank continues until the pressure in the storage tank rises sufiiciently to again close the supply valve 78. By this means, the replacement of gas leaking from the engine during operation is provided for. Since the supply tank discharges to the inlet side of the gas compressor, the complete supply of gas in the tank may be exhausted before the tank must be recharged or replaced by a full tank.

It should now be apparent that the gas pressure control means forming the present invention provides a system which operates without the need for check valves in the lines connecting with the engine working and buffer spaces and accordingly avoids the problems which have occurred through the use of these valves. While various specific valve and control mechanisms have been illustrated to aid in the description of the invention, it is not intended that these structures should limit the invention in any way. It is obvious that any suitable valves or mechanisms having the same functions could equally well be used where appropriate.

While the invention has been described by reference to a single embodiment, it should be apparent that numerous changes could be made without departing from the spirit and scope of the invention which is accordingly to be limited only by the language of the following claims.

I claim:

1. In combination with a hot gas engine having a plurality of gas containing enclosed spaces arranged to cyclically vary in pressure in out of phase relation to one another, gas storage means, means connecting said enclosed spaces with said gas storage means for transferring gas therebetween and control means associated with said connecting means to control the gas pressure in said spaces, said control means comprising a plurality of fill valves in said connecting means, one

intermediate each of said enclosed spaces and said gas storage means and operable to permit the transfer of gas to said spaces, actuating means adapted to contact said fill valves and operable to open all said valves concurrently, and

means to maintain said gas storage means at a minimum pressure greater than the maximum pressures of said enclosed spaces,

whereby flow through said fill valves is unidirectional and bypassing of gas between said enclosed spaces through said fill valves is prevented.

2. In combination with a hot gas engine having a cylinder, a power piston in said cylinder and, in part, defining at opposite ends of said piston a pair of enclosed variable volume gas containing spaces, gas storage means, means connecting said enclosed spaces with one another and with said gas storage means for transferring gas therebetween and control means associated with said connecting means to control gas transfer therethrough, said control means comprising a pair of fill valves, one intermediate each of said enclosed spaces and said gas storage means and operable to permit the transfer of gas to said spaces, actuating means adapted to contact said fill valves and operable to open both said valves concurrently, and means to maintain said gas storage means at a minimum pressure greater than the maximum pressures of said enclosed spaces,

3. The combination of claim 2 wherein said enclosed spaces include a working space wherein said gas goes through a heat power cycle by which heat energy input is converted to work output to the power piston, and

a bufier space wherein pressurized gas, at least in part, balances working gas pressures on the engine power piston.

4. In combination with a hot gas engine having a working space and a buifer space, gas pressure control means comprising gas storage means means including a compressor to maintain said gas storage means at a minimum pressure greater than the maximum pressures of said working and buffer spaces,

a first fill valve connecting with said storage means and with said working space to control the supply of gas to said working space,

a second fill valve connecting with said storage means and with said buffer space to control the supply of gas to said bufier space,

a bypass valve connecting with said working and buffer spaces to control the bypassing of gas therebetween,

a dump valve connecting to one of said working and bulier spaces and to said compressor to control the discharge of gas from said working and buffer spaces, said compressor being operable to receive gas from said dump valve and to deliver said gas to said gas storage means, and

means for selectively operating said valves to vary the quantity of gas in the Working and buffer spaces of the engine.

5. The combination of claim 4 wherein the valve operating means is movable to a plurality of positions including a first position wherein said fill valves are open to supply gas to the working and bufi-er spaces,

a second position wherein all said valves are closed to hold constant the quantity of gas in the working and buffer spaces, and

a third position wherein said bypass and dump valves are open to exhaust gas from the working and buffer spaces and to bypass gas between said spaces to reduce engine power.

6. The combination of claim 5 wherein said gas storage pressure maintaining means further includes a gas supply tank,

means connecting said supply tank with said compressor to supply gas therethrough to said gas storage means, and

a supply valve in said connecting means and operatively connected with said gas storage means to control the supply of gas from said supply tank so as to permit gas flow to the compressor whenever the gas pressure in said storage means reaches a predetermined minimum.

7. In combination with a hot gas engine having a working space and a buffer space, gas pressure control means comprising a gas supply tank,

a working gas storage tank,

means connecting said supply tank with said storage tank and including a compressor operable to receive gas from said supply tank and to deliver gas to said storage tank and means controlling the delivery of gas from said supply to said compressor to maintain a minimum gas pressure in said storage tank greater than the highest pressure existing in said working and buffer spaces,

a first fill valve conecting with said storage tank and with said working space and controlling the supply of gas to said working space,

a second fill valve connecting with said storage tank and with said buffer space and controlling the supply of gas to said buffer space,

a bypass valve connecting with said working and buffer spaces and controlling the bypassing of gas therebetween,

a dump valve connecting to one of said working and bufier spaces and to said compressor, said compressor being operable to receive gas from said dump valve and to deliver said gas to said storage tank, and

means for selectively operating the valves to vary the quantity of gas in the working and buffer spaces of the engine.

8. The combination of claim 7 wherein said valve operating means is movable to a plurality of positions including a first position wherein said fill valves are open to supply gas to the working and buffer spaces a second position wherein all said valves are closed to hold constant the quantity of gas in the working and buffer spaces, and

9. The combination of claim 8 wherein said means controlling the delivery of gas from said supply tank to said compressor comprise a supply valve connected between said supply tank and said compressor, and

a pressure responsive actuator connected with said storage tank and responsive to a reduction in pressure therein to a predetermined minimum to open said supply valve and permit the passage of gas from the supply tank, through the compressor to the storage tank.

10. The combination of claim 8 wherein said dump valve connects with said working space and further comprising a pressure responsive valve connected between said storage tank and said first and second fill valves and operable to cut ofi the supply of gas to said fill valves, said limit valve being connected with the engine working space and operable in response to the existence of a predetermined maximum pressure therein to cut off said gas supply.

11. The combination of claim 10 wherein valve operating means include a pressure responsive actuator operable in response to a pressure signal to move said operating means to a selected one of said plurality of positions.

References Cited UNITED STATES PATENTS 2,746,241 5/ 1956 Dros 60-24 2,794,315 6/1957 Meijer 6024 2,966,034 12/ 1960 Gifiord 62--6 3,036,427 5/1962 Meijer 62-6 3,355,881 12/1967 Brandes 6024 3,397,533 8/1968 Steiner 6024 WILLIAM J. WYE, Primary Examiner.

US. Cl. X.R.