US3775970A - Pressure translating apparatus and process - Google Patents

Abstract

An apparatus and process for conversion of thermal energy into mechanical energy wherein the working fluid of a heat engine is in contact with one side of a pressure sensitive means such as a piston or diaphragm, the other side of the pressure sensitive means being in contact with an incompressible fluid which in turn is in contact with the first ends of a pair of opposing pistons, the pistons being linked by mechanical linkage, the second end of one piston being in contact with a fluid to be pumped and the second end of the second piston being in contact with a cushion chamber, providing a quiet running thermal engine without dynamically unbalanced forces, with substantially reduced influence on the performance and smooth running of the dynamic instability inherent to free-piston systems generally, and with a positive control of the piston travel. The apparatus is particularly advantageously used in connection with a refrigeration system wherein the backside of the second end of each piston is in contact with the refrigeration fluid at evaporator pressure and the face of the second end of each piston is in contact with the refrigeration fluid at condenser pressure.

Description

Wurm

[111 3,775,970 [4 11 Dec.4, 1973 PRESSURE TRANSLATING APPARATUS AND PROCESS Inventor:

Assignee:

Filed:

Appl. No:

Jaroslav Wurm, Cicero, 111.

The Institute of Gas Technology,

Chicago, 111.

June 14, 1972 Int. Cl. F25b 27/00, F02g 1/04 Field of Search /6, 24; 62/467,

References Cited 7 UNITED STATES PATENTS Primary Examiner-Martin P. Schwadron Assistant Examiner-Allen M. Ostrager Att0rney-Richard E. Alexander et a1.

couocu ev ABSTRACT An apparatus and process for conversion of thermal energy into mechanical energy wherein the working fluid of a heat engine is in contact with one side of a pressure sensitive means such as a piston or diaphragm, the other side of the pressure sensitive means being in contact with an incompressible fluid which in turn is in contact with the first ends of a pair of opposing pistons, the pistons being linked by mechanical linkage, the second end of one piston being in contact with a fluid to be pumped and the second end of the second piston being in contact with a cushion chamber, providing a quiet running thermal engine without dynamically unbalanced forces, with substantially reduced influence on the performance and smooth running of the dynamic instability inherent to free-piston systems generally, and with a positive control of the piston travelsThe apparatus is particularly advantageously used in connection with a refrigeration system wherein the backside of the second end of each piston is in contact with the refrigeration fluid at evaporator pressure and the face of the second end of each piston is in contact with the refrigeration fluid at condenser pressure.

5 Claims, 4 Drawing Figures PEVAPORATOR Poouoeuselt HEAT OUT

. PRESSURE TRANSLATING APPARATUS AND PROCESS Heretofore, heat actuated regenerative compressors have been used to power refrigerating systems as described in US. Pat. Nos. 3,474,641 and 3,491,554. Other types of external combustion thermal engines have been well known in the art for many years to function as prime movers and to provide for conversion of thermal energy into mechanical energy- Heat actuated regenerative compressor-cooling systems wherein the refrigerant is also a working fluid of such compressor using carbon dioxide and sulfer dioxide have been de scribed in US. Pat. No. 3,400,555. Internal combustion thermal engines used to power refrigeration systems have been described in U.S. Pat. applications, Ser. No. 91,833, Internal Combustion Heat Engine and Process, now U.S. Pat. No. 3,677,027 and Ser. No. 91,355, Internal Combustion Heat Engine and Process, now U.S. Pat. No. 3,677,026 both filed Nov. 23, 1970.

In the operation of the thermal engine for purposes such as air conditioning, *it is highly desirable that the engine and associated apparatus be as quiet and vibration free as possible.

Therefore, it is an object of my invention to provide an improved pressure translating apparatus having dynamic balanced forces.

It is another object of my invention to provide an improved pressure translating apparatus aifording positive piston motion.

It is another object of my invention to provide an improved pressure translating apparatus with reduced dynamic instability of the free-piston motion by means of the additional damping effect of the acceleratingdecelerating mass of an incompressible fluid.

It is still another object of my invention to provide an improved pressure translating apparatus wherein the operating pressure of the associated apparatus driven by such translating means may be different from the pressure of the thermal 'engine driving the pressure translating apparatus.

It is a further object of my invention to provide an improved, quiet and trouble-free cooling system powered by a thermal engine coupled to the improved pressure translating apparatus which is assisted by the pressure of the refrigerant in a separate refrigeration system.

These and other important objects will become ap parent from the following description taken in conjunction with the drawings showing preferred embodiments wherein:

FIG. 1 is a cross section view of one embodiment of a thermal engine having a pressure sensitive means useful in conjunction with the pressure translating apparatus of this invention;

FIG. 2 is a cross section view of the pressure translating apparatus of this invention in conjunction with a cooling system;

FIG. 2a shows enlargement of the flywheel interconnecting system of the apparatus shown in FIG. 2; and

FIG. 3 graphically illustrates the pressure volume relationship of the power cycle and the compression cycle using an apparatus according to this invention.

Referring specifically to FIG. 1, the heat-actuated regenerative compressor 1 comprises outer shell casing 2, insulation 4, and inner shell casing 5 defining gas chamber 6, which is generally cylindrical in shape. Shaft 14' is disposed through chamber 6, and retained in suitable source (not shown) which causes shaft 14 to undergo an oscillating movement. Secured to shaft 14 is an insu lating hub 18 having vane 20con'structed of suitably supported thermal insulating material extending to and congruent with inner shell casing 5. Vane 20 divides chamber 6 into cold section 19 and hot section 21. P0- sitioned within chamber 6 from inner shell casing toward the center of the chamber 6 to hub 18 extend ing substantially the entire length of the chamber 6 separating cold section 19 from hot section 21 are cooling means 22, heat regenerative means 23, and heating means 24. The sizes of such'heat transfer components shown in FIG. 1 are based upon current heat transfer materials, designs and techniques. However, it would be apparent to one skilled in the art that if moreefiicient heat transfer units become available, the size, proportions and shapes of the heat transfer units could readily be changed accordingly. The large hub 18 and insulator 25 provide a long travel distance insulating cold section .19 from hot section 21 at the heat exchangers. However, insulator 25 is not essential for all operating conditions.

Briefly, operation of the compressor is achieved by vane 20 moving gas from cold section 19 in order through the cooler-ragenerator-heater into hot section 21 at an average higher temperature-pressure relationship and then returning the gas from hot section 21 in order back through the heater-regenerator-cooler to cold section 19 at an average lower temperaturepressure relationship. Vane frequencies of from about 15 to 500 cycles per minute are suitable for the operation of such a compressor, preferred frequencies being from about to 300 cycles per minute.

The heat actuated compressor is operated by use of gases having high thermal-conductivity and specific heat ratio. Preferred gases includle hydrogen and monatomic inert gases such as helium. Either a single gas or mixtures of different gases may be used. Helium is especially preferred. The heat actuated regenerative compressor is described in more detail in U.S. Pat. Nos. 3,474,641 and 3,491,554.

Any power unit affording cycles of high and low pressures is suitable for use in conjunction with the improved pressure translating apparatus of this invention. Especially suitable power means include external combustion heat engines as described above and internal combustion heat engines as described in U.S. Pat. applications Ser. Nos. 91,355 and 91,833 referred to above. 7

The pressure translating device of my invention receives its energy through a pressure responsive means in contact with the active volume of the heat engine. FIG. 1 shows pressure sensitive means in contact with the active volume of the heat engine. Pressure sensitive means 10 comprises piston. 32 adapted for reciprocating motion within cylinder 31 and having face 33 in communication with cold section 19 of said heat actuated regenerative compressor and face 34 in communication with the incompressible fluid in the pressure translating apparatus. Piston 32 reciprocates with substantially gas-tight relationship between cylinder 31 and cold section 19 maintained by bellows 35, attached to one end of inner shell casing 5 and at the other end to piston 32.

Bellows 35 must be constructed of suitable material and of suitable design to permit the required flexing and expansion while at the same time maintaining gas tight relationship between cold section 19 and the incompressible fluid in the pressure translating apparatus. Metal bellows are most satisfactory using copper, nickel and various stainless steel alloys or mixtures of copper and nickel. It is also apparent that other flexible materials such as certain rubber or synthetic materials such as butyl rubber, a laminated structure embodying saran, and Dacron fabric impreganted with polymeric elastomer may be used if they do not permit diffusion of the gases or liquids used. Suitable bellows are available commercially.

FIG. 2 shows the pressure translating apparatus of my invention in cross section with another embodiment of the pressuresensitive means in communication with cold section 19 of heat actuated regenerative compressor 1. Diaphragm 36 is supported by diaphragm support block 37. The diaphragm may be of any suitable impermeable material such as stainless steel or plastic such as Dacron fabric impregnated with polymeric elastomer. Diaphragm 36 is in direct communication with cold portion 19 of heat engine 1 on one side and in direct communication with fluid 39 on the opposite side. Diaphragm support block 37 is mounted in exterior fluid tight relationship to cylinder 31 and fluid vessel 38, but in internal communication with cold section 19 of heat actuated regenerative compressor 1 and an incompressible fluid 39 such as oil. Any incompressible fluid is satisfactory for use in the pressure translating apparatus of my invention. Particularly preferred is an oil having lubricating properties. Fluid vessel 38 is attached in external fluid tight relationship to cylinder 40, but in internal communication with pistons 43 and 46 Cylinder 40 defines compression chamber 41 at one end and cushion chamber 42 at the opposite end. Compression piston 43 has one end 44 in contact with the above-described incompressible fluid and the opposite end 45 in contact with compression chamber 41. Cushion piston 46 has one end 47 in contact with the above described incompressible fluid and the opposite end 48 in contact with cushion chamber 42. Compression piston 43 has seal 60 near end 45 and seal 61 near end 44. Cushion piston 46 has seal 63 near end 48 and seal 62 near end 47. These seals may be of any suitable material permitting free movement of the pistons within the cylinder while maintaining fluid separation. For her metically sealed units, when lubricating oil is used as fluid 39, it is feasible, by methods known in the art, to have returns to fluid vessel 38 for oil which may have found its way into chambers 41 and 42. Compression piston 43 and compression chamber 41 have the configuration of a Uniflow compressor. Piston 43 has oneway valves 58 through its face for communication with compression chamber 41 on both sides of end 45 of compression piston 43. Compression chamber 41 has end 65 with one-way valves 59 for communication between compression chamber 41 and condenser 70 of a cooling system. Valves 58 and 59 operate solely by pressure differential in the same manner as in well known Uniflow compressors.

The piston interconnecting system is shown in FIG. 1 with piston 43 and piston 46 near their closest position of their cycle representing near the lowest pressure in the heat engine cycle. FIG. 2a is an enlarged portion of the piston interconnecting system showing pistons 43 and 46 in the extreme separated portion of their cycle representing the highest pressure in the heat engine cycle. Reference to FIG. 2 a is made to describe the piston interconnecting system. The pistons may be interconnected by any suitable mechanical linkage providing simultaneous opposite movement of the pistons. Any internal rotably mounted member on a shaft having rotably mounted connecting links attached at one end to the member at 180 to each other, one link rotably attached to the compression piston on the other end and the other link rotably attached to the cushion piston on the other end is suitable. A preferred internal linkage is shown in FIG. 20 wherein internal wheel 50 of the same apparatus as shown in section in FIG. 2 oscillates on shaft 51. Connecting rod 53 is rotatably attached to wheel 50 by pin 52 at one end at the other end rotatably attached by pin 54 to piston 43. Likewise, connecting rod 56 is rotatably connected at one end to wheel 50 by pin 57 and at the other end rotatably connected to piston 46 by pin 55. The interconnecting mechanical linkage through oscillating wheel 50 thus provides positive simultaneous opposite movement of pistons 43 and 46. The wheel may be connected in saddle fashion by pins 54 and going through the piston and having identical linkages corresponding to 53 and 56 on the opposite side and connected to the wheel on the opposite side, or the wheel and pistons may be connected on one side as shown in FIG. 2a. The oscillating wheel connecting apparatus is completely within cylinder 40 affording hermetically sealed operation.

As shown in FIG. 2 the membrane 36 is in the position obtained by the minimum pressure condition of the heat engine. In this position pistons 43 and 46 are at their closest position to each other. As membrane 36 is forced downward by increasing pressure in the heat engine, incompressible fluid 39 is likewise forced downward and applies a greater pressure to face 44 of piston 43 and face 47 of piston 46. The pistons are then forced away from each other, piston 43 compressing the refrigerant in chamber 41.

The apparatus of my invention may be used to convert thermal energy into mechanical energy which may be used, for instance, as a pump. As specifically illustrated in FIG. 2 the pressure translating apparatus of my invention may be utilized as a pump to obtain the condenser pressure in any standard compressioncondensationexpansion-evaporation cooling cycle. In FIG. 2 piston 43 compresses the refrigerant in chamber 41 and the high pressure refrigerant gas flows through condenser removing heat from the refrigerant to the ambient atmosphere. The refrigerant flows from condenser 70 as a liquid through expansion throttle 71 reducing the pressure to evaporation pressure, and through evaporator 72 wherein heat is taken up from the exterior confined atmosphere. The heat so taken up represents the cooling of confined room air in the case of room air conditioning. The refrigerant flows from evaporation 72 to the portion of chamber 41 behind piston 43. As piston 43 returns from the compression stroke the refrigerant flows through valves 58 in piston 43 to the compression portion of chamber 41. The piston then moves in the compression stroke, valves 58 in piston 43 being closed, and the refrigerant is compressed to condenser pressure flowing through valves 59 to the condenser. Valves 59 close while piston 43 returns from the compression stroke. During the cycle of compression piston 43, cushion piston 46 is operating against constant pressures in cushion chamber .42. As shown in FIG. 2, conduit 74 places the portion of chamber 42 behind piston 46 in contact with the evaporator of the cooling system and conduit 76 places the portion of chamber 42 ahead of piston 46 in contact with the condenser of the cooling system wherein the refrigerant is compressed by piston 43. Thus chamber 42 acts as a cushion chamber balancing the pressure forces of the compression portion of my apparatus. The pressure translation apparatus of my invention together with a suitable heat engine and standard air conditioning equipment provides a quiet vibration-free apparatus suitable for hermetically sealed operation.

The pressure translating apparatus of my invention provides for differing pressure ratios of the working gas of the heat engine and the refrigerant in the cooling cycle. Suitable differences in such pressure ratios may readily be obtained by varying the sizes of the opposite ends of each piston 43 and 46. Thus, the apparatus of my invention provides a suitable pressure translating apparatus where the pressure ration in heattactuated regenerative compressors is from about 1.3 to 1.8 while the pressure ratio in desired cooling cycles is from 3.0 to about 4.5. a i

Referring to FIG. 3, the pressure-volume relationships of the apparatus shown in FIGS. 1 and 2 are shown using helium as the working gas of the power unit and Freon 22 as the refrigerant in the cooling unit. This is onepreferred combination of gases suitable. Thepoints A on the refrigerant compression cycle and A on the power cycle correspond to the position of the translating apparatus shown in FIG. 2, while points C and C correspond tothe position shown in FIG. 2a. It is also seen from FIG. 3 that the power cycle of the heat engine is not modified by the pressure translating apparatus of my invention in an ideal case with the moving masses equal to zero. e

The apparatus of my invention may be used in association with conventional cooling systems. Refrigerants suitable for use in the cooling apparatus of my invention include those refrigerants suitable for compression-refrigeration cycles. Preferred refrigerants include halogenatedhydrocarbons and S0 Particularly preferred refrigeratns are those selected from the group consisting of Freon l2, Freon 22. Freon designates a group of halogenated hydrocarbons containing one or more fluorine atoms which are widely used as refrigerants. The operating conditions and particular refrigerant used determine the pressure and temperature relationships of the closed refrigerating cycle.

Under most operating condtions the evaporating temperature is from about 35 to 50F. and the condensing ts l nq atursfr tn about to 150 F. oth under an: stant pressure. Particularly preferred condensing temperatures are from about 105 to 140F. In conventional air-conditioning systems the pressure ratio, defined as the ratio of the absolute pressure in the condenser and the absolute pressure in the evaporator, is from about 3 to 4-%.

My invention relates to a cooling apparatus comprising a heat engine having pressure sensitive means of varying displacemnt in accordance with the working fluid of the heat engine having alternate cycles of higher and lower pressures and cooling apparatus comprising compression means, condenser'means, expansion means, evaporation means and a contained refrigerant, wherein the improvement comprises the compression means having a cylinder defining a compression chamber at one end, a cushion chamber at the other end and a central portion in communication with the pressure sensitive means of the heat engine, opposs .sion chamber and the cushion chamber, respectively, and a smaller end reciprocating in the central portion of the cylinder, the larger end of the compression piston having one way valves therethrough in communication with the compression chamber on both sides of the larger end of thecompression piston, the compression chamber having the end nearest the larger end of the compression chamber when fully moved into the compression chamber with one way valves in communication with the portion of the compression chamber between the piston and that end and the pressurized output, the combination of the compression piston and the compression chamber forming a Uniflow type pump, the compression and cushion pistons being interconnected by mechanical interconnecting means providing positive opposite reciprocation of the pistons, and a fluid vessel containing an incompressible fluid in fluid tight relationship and in internallcommunication with the pressure sensitive means on one end and the smaller ends of the opposing pistons on the other end. Thus, the fluid is in direct communication with the pressure sensitive means andthe smaller ends of the pistons and forces the pistons to reciprocate by the pressure of the fluid obtained by theqvarying displacement of the pressure sensitive means in response to the working fluid of the heat engine. In a preferred cooling apparatus, according to this invention, the evaporator of the cooling system is in communication with the backside of the larger end of both the compression and cushion pistons, thereby applying the evaporator pressure to the backsides of thepistons, and the condenser of the cooling system is in communication with the forward side of the larger end of the cushion piston thereby applyingthe condenser pressure to the forward side of the piston. Such an air cooling apparatus provides statically and dynamically balanced forces and is suitable for use as a residential or commercial air con ditioning unit. 1

In the process for cooling contained exterior atmosphere by compression, condensation, expansion, evaporation cooling cycle, my invention is the improvement comprising the steps of compressing contained gaseous refrigerant by t a reciprocating compression piston driven by an incompressible fluid in communication with the pressure sensitive means of a heat engine having alternate cycles of higher and lower pressure conditions, the compression piston being in interconnecting mechanical linkage with an opposing cushion piston so that the pistons move oppositely to provide dynamic and pressure force balance, and damp the dynamic instabilities of the system. In a preferred process the evaporator of the cooling system is in communication iwth the backside of the largerend of the compression piston and the cushion piston thereby applying evaporator pressure to the backsides of both pistons and the condenser of the cooling system is in communication with the forward side of the larger end of the cushion piston thereby applying the condenser pressure to the forward side.

While in the foregoing specification this invention bodiments thereof, and many details have been set forth for purpose of illustration, it will be apparent to those skilled in the art that the invention is susceptible to additional embodiments and that certain of the details described herein can be varied considerably without departing from the basic principles of the invention.

I claim:

. l. A dynamically balanced pressure translating apparatus for conversion of thermal energy into mechanical energy for use in combination with a heat engine having pressure sensitive means of varying displacement in accordance with the working fluid of the heat engine having alternate cycles of higher and lower pressures, comprising; a cylinder defining a compression chamber at one end, a cushion chamber at the other end and a centralportion in communication with said pressure sensitive means, opposing reciprocating compression and cushion pistons each having a larger end reciprocating in said compression chamber and said cushion chamber respectively and a smaller end reciprocating in the central portion of said cylinder, said larger end of said compression piston having one way valves therethrough in communication with said compression chamber on both sides of said larger end of the compression piston, said compression chamber having an end nearest said larger end of the compression piston when fully moved into said compression chamber with one way valves in communication with the portion of said compression chamber between said piston and said end and the pressurized output, said pistons being interconnected by mechanical interconnecting means providing positive opposite reciprocation of said pistons, and a fluid vessel containing an incompressible fluid in fluid-tight relationship and in internal communication with said pressure sensitive means on one end and said smaller ends of said opposing pistons on the other end, whereby said fluid being in direct communication with said pressure sensitive means and said maller ends of said pistons force said pistons to reciprocate by the pressure of said fluid obtained by the varying displacement of the pressure sensitive means in response to the working fluid of said heat engine.

2. The apparatus of claim 1 wherein said interconnecting means comprises, an internal rotably mounted member on a shaft within said cylinder, a first connecting link rotably fastened to said member at one end and rotably fastened to said compression piston on the other end, and a second connecting link rotably mounted to said member at from the fastening of said first connecting link and the other end rotably fastened to said cushion piston.

3. The apparatus of claim 2 wherein said rotably mounted member is wheel-shaped and said connecting links are fastened at the rim thereof.

4. The apparatus of claim 1 wherein said fluid is lubricating oil.

5. A process for conversion of thermal energy of a heat engine having working fluid of alternate cycles of higher and lower temperature-pressure conditions thereby varying the displacement of a pressure sensitive means into mechanical energy comprising; the steps of moving a reciprocating compression piston by an incompressible fluid in communication with said pressure sensitive means and moving an opposing cushion piston oppositely by providing inter-connecting mechanical linkage to provide dynamic and pressure force balance, and damping of the dynamic instabilities of the system.

Claims (5)

1. A dynamically balanced pressure translating apparatus for conversion of thermal energy into mechanical energy for use in combination with a heat engine having pressure sensitive means of varying displacement in accordance with the working fluid of the heat engine having alternate cycles of higher and lower pressures, comprising; a cylinder defining a compression chamber at one end, a cushion chamber at the other end and a central portion in communication with said pressure sensitive means, opposing reciprocating compression and cushion pistons each having a larger end reciprocating in said compression chamber and said cushion chamber respectively and a smaller end reciprocating in the central portion of said cylinder, said larger end of said compression piston having one way valves therethrough in communication with said coMpression chamber on both sides of said larger end of the compression piston, said compression chamber having an end nearest said larger end of the compression piston when fully moved into said compression chamber with one way valves in communication with the portion of said compression chamber between said piston and said end and the pressurized output, said pistons being interconnected by mechanical interconnecting means providing positive opposite reciprocation of said pistons, and a fluid vessel containing an incompressible fluid in fluid-tight relationship and in internal communication with said pressure sensitive means on one end and said smaller ends of said opposing pistons on the other end, whereby said fluid being in direct communication with said pressure sensitive means and said maller ends of said pistons force said pistons to reciprocate by the pressure of said fluid obtained by the varying displacement of the pressure sensitive means in response to the working fluid of said heat engine.

2. The apparatus of claim 1 wherein said interconnecting means comprises, an internal rotably mounted member on a shaft within said cylinder, a first connecting link rotably fastened to said member at one end and rotably fastened to said compression piston on the other end, and a second connecting link rotably mounted to said member at 180* from the fastening of said first connecting link and the other end rotably fastened to said cushion piston.

3. The apparatus of claim 2 wherein said rotably mounted member is wheel-shaped and said connecting links are fastened at the rim thereof.

4. The apparatus of claim 1 wherein said fluid is lubricating oil.

5. A process for conversion of thermal energy of a heat engine having working fluid of alternate cycles of higher and lower temperature-pressure conditions thereby varying the displacement of a pressure sensitive means into mechanical energy comprising; the steps of moving a reciprocating compression piston by an incompressible fluid in communication with said pressure sensitive means and moving an opposing cushion piston oppositely by providing inter-connecting mechanical linkage to provide dynamic and pressure force balance, and damping of the dynamic instabilities of the system.

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