US 3861146 A
A hot-gas reciprocating engine in which at least the part of the cylinder which bounds the hot expansion space and at least the regenerator housing part which encloses the regenerator part of higher temperature have inner walls which are provided with a heat-insulating layer; cooling members maintain these parts of cylinder and regenerator housing at a lower temperature.
Claims available in
Description (OCR text may contain errors)
United States Patent [191 Lynch et al.
[ Jan. 21, 1975 HOT-GAS RECIPROCATING ENGINE  Inventors: Brian Lynch; Roeli Jan Meijer, both of Emmasingel, Eindhoven, Netherlands  Assignee: U.S. Philips Corporation, New
 Filed: Dec. 12, 1973  Appl. No.: 424,114
 Foreign Application Priority Data Jan. 2, 1973 Netherlands 7300002  US. Cl. 60/524, 60/526  Int. Cl. F02g 1/04  Field of Search 60/516, 517, 524, 526
 References Cited UNITED STATES PATENTS Meijer et al. 60/524 FOREIGN PATENTS OR APPLICATIONS 87,805 4/1958 Netherlands 60/524 Primary ExaminerMartin P. Schwadron Assistant Examiner-Allen M. Ostrager Attorney, Agent, or Firm-Frank R. Trifari [5 7] ABSTRACT A hot-gas reciprocating engine in which at least the 7 part of the cylinder which bounds the hot expansion space and at least the regenerator housing part which encloses the regenerator part of higher temperature have inner walls which are provided with a heatinsulating layer; cooling members maintain these parts of cylinder and regenerator housing at a lower temperature.
9 Claims, 4 Drawing Figures PATENIED JAN 21 I975 SHEET 2 BF 4 HOT-GAS RECIPROCATING ENGINE BACKGROUND OF THE INVENTION The invention relates to a known type of hot-gas reciprocating engine, comprising at least one cylinder with an expansion space of variable volume and higher mean temperature during operation, the said expansion space communicating, via a regenerator which is incorporated in a housing, with a compression space of variable volume and of lower mean temperature during operation. The compression and expansion spaces which together constitute a working space can be present in the same cylinder (British patent specifications Nos. 857,758 and 898,270) or in two different cylinders (British patent specifications Nos. 695,014 and 708,199). 1
During operation of such a hot-gas reciprocating engine, heat is applied to the working medium in the engine, for example, helium or hydrogen, via a heat exchanger: the heater which usually consists of a number of pipes. A medium, such as the combustion gases which flow along the pipes, gives off heat through the pipe walls to the working medium flowing through these pipes.
In the efforts to achieve a higher specific power (shaft horse power per litre of cylinder capacity) by increasing the working medium pressure in the engine and to increase the thermal efficiency by increasing the heater temperature, a problem is encountered in that the commonly used and comparatively inexpensive construction materials for cylinders and regenerator housings can no longer be used.
For example, the commonly used stainless steel types have an intolerable creepage rate at working medium pressures in excess of approximately 100 atmospheres absolute and temperatures in excess of approximately 650C. High-quality metal alloys can be used which are capable of withstanding high working medium pressures and temperatures, however, a major drawback is that these metal alloys contain rather rare elements such as cobalt and nickel, which is one of the main reasons, if not the major reason, why they are expensive. The high cost of these metal alloys and the dependency on rather rare metals make the application of such alloys unattractive in the bulk manufacture of hot-gas reciprocating engines. In addition, alloys of this kind can be less readily machined than materials such as stainless steel.
SUMMARY OF THE INVENTION The present invention has for its object to mitigate these drawbacks by providing a hot-gas reciprocating engine which can be operated at high working medium pressures (up to approximately 250 ata) and at high heater temperatures, without expensive construction materials which contain rare metals and which are difficult to machine being required for cylinders and regenerator housings.
So as to achieve this object, the ht-gas reciprocating engine according to the invention is characterized in that at least the part of the cylinder which bounds the expansion space and at least the part of the regenerator housing which envelops the regenerator part of higher temperature during operation facing the expansion space, have inner walls which are each provided with at least one layer of a heat-insulating material; this layer acts as a partition between the cylinder part and the expansion space and between the regenerator housing part and the regenerator part, respectively, cooling members being provided for maintaining a lower mean temperature of the said parts of cylinder and regenerator housing during operationv Due to the provision of the heat-insulating layer on the inner walls of cylinder and regenerator housing, the cylinder and the housing are no longer in direct thermal and mechanical contact with the working medium. At high temperatures and high pressures of the working medium, the thermal and the mechanical loading of the cylinder wall and the regenerator housing wall then remain low. The cylinders and regeneratorhousings of such high-load hot-gas reciprocating engines can thus be manufactured of conventional, inexpensive construction materials such as nodular cast iron or lowalloy steel types which can also be readily machined.
The cooling members ensure that a high temperature gradient in the radial direction across the heat-.
insulating layer is maintained under all circumstances. Temperature equalization in the radial direction after a given period of operation, which might cause an excessively high temperature level of cylinder and regenerator housing, is thus prevented. The quantity of heat to be discharged from the cylinders and regenerator housings remains limited due to the heat-insulating layer, with the result that the thermal efficiency of the engine is high. If the heat-insulating layer were not provided, the cooling would cause a catastrophical loss of thermal efficiency.
In a preferred embodiment of the hot-gas reciprocating engine according to the invention, the heatinsulating layer is made of a ceramic material. Notably given glass ceramic materials offer the advantage that they have a very low heat conductivity and expansion coefficient, favourable thermal impact resistance and proper mechanical strength.
The low heat conductivity coefficient makes it possible to maintain, in the case of a small wall thickness of the heat-insulating layer (for example, 5 mm) and a comparatively low cooling capacity, comparatively low temperatures (for example C) at the area of the interface between the heat-insulating layer and the cylinder or the regenerator housing, respectively. The low expansion coefficient ensures that there is no risk of chipping of the glass ceramic material in the case of working medium temperature fluctuations. The favorable thermal shock-resistance makes it possible to maintain a very steep temperature gradient permanently over a very thin glass ceramic layer. The favorable mechanical strength, finally, renders the heatinsulating layer capable of withstanding the variable mechanical loads which are caused by the variable working medium pressures in the engine. The heatinsulating glass ceramic layer can be deposited directly on the inner wall of cylinder and regenerator housing. It is alternatively possible to make use of glass ceramic jackets as inserts which are fastened after insertion in the cylinder and regenerator housing.
A preferred embodiment of the hot-gas reciprocating engine according to the invention is characterized in that the part of the cylinder which bounds the expansion space and the part of the regenerator housing which envelops the regenerator part of higher temperature which faces the expansion space are enveloped by a heat pipe which serves as a cooling member. This heat pipe contains a heat transport medium which completes an evaporation-condensation cycle during operation, evaporation taking place by taking up heat from the cylinder or the regenerator housing, respectively, and condensation taking place elsewhere on a heattransmitting heat pipe wall while giving off heat thereto.
A heat pipe is to be understood to mean herein a heat transport device which is formed by a reservoir in which a small quantity of heat transport medium, for example water, is present which, on the one side, evaporates from a wall by taking up heat from a heat source and which, on the other side, gives off heat to another wall while changing over from the vapor to the liquid phase.
Using a heat pipe of this kind, very large quantities of heat can be transported without a pumping device or other moving parts being required. Condensed heat transport medium can be returned to the wall where evaporation takes place under the influence of gravity. However, the heat pipe often comprises a capillary structure which connects the condensation wall to the evaporation wall and through which condensate is returned under all circumstances to the evaporation wall by capillary action.
Heat pipes provided with a capillary structure for returning condensate are known per se, for example, from United States patent specification Nos. 3,299,795 and 3,402,767. 767. The heat pipe can serve as a converter from high to low heat flow density in that the heat taken up from the cylinder or regenerator housing wall as the evaporation wall can be spread over a heat pipe condensation wall of larger surface area.
In a further preferred embodiment of the hot-gas reciprocating engine according to the invention, the said parts of cylinder and regenerator housing are provided with a cooling jacket which comprises one or more ducts through which cooling liquid can flow. According to the invention, it is advantageous to incorporate one or both cooling jackets in a closed duct system in which the cooling liquid can circulate, the said duct system elsewhere containing a heat exchanger in which the liquid can give off heat to the surroundings.
If a hot-gas engine of this kind is used as a traction engine, it can at the same time provide the heating of the passenger compartment. In the known hot-gas engine comprising a cooler for discharging the compression heat of the working medium, the cooling water temperature is normally too low for realizing proper heating of the passenger compartment.
The invention will be described in detail hereinafter with reference to the drawing in which a few embodiments of the hot-gas reciprocating engine are diagrammatically shown (not to scale) by way of example.
BRIEF DESCRIPTION OF THE DRAWINGS F IG. 1 is a longitudinal sectional view of a hot-gas reciprocating engine,
FIG. 2 is a plan view of a 4-cylinder double-acting hot-gas reciprocating engine,
FIG. 3 is a sectional view taken along the line IIIIII of FIG. 2, and
FIG. 4 is a longitudinal sectional view of an indirectly heated hot-gas reciprocating engine.
DESCRIPTION OF THE PREFERRED EMBODIMENT The reference numeral 1 in FIG. 1 denotes a cylinder in which a piston 2 and a displacer 3 can move at a phase difference. The piston and the displacer are connected to a drive system not shown, by means of a piston rod 4 and a displacer rod 5, respectively. Present between the piston 2 and the displacer 3 is a compression space 6 which is in open communication with an expansion space 10 above the displacer via a coller 7 for discharging the compression heat, a regenerator 8 and a heater 9.
The heater 9 consists of a plurality of bent pipes which are arranged in a ring about the space 11 for combustion gases and which each communicate on the one side with regenerator 8 and on the other side with expansion space 10. The arrangement is such that an inner pipe row 9 and an outer pipe row 9" are provided, the latter row being concentric with the former. Present between the pipes of each row are gaps which serve as passages for combustion gases. The pipes of outer row 9' are provided on their lower ends with fins 12 so as to increase the heat-transfer surface at this area. The hot-gas reciprocating engine comprises a burner device 13 with a burner 14 and an inlet 15 for combustion air. Also provided is an outlet 16 for combustion gases.
During operation of the hot-gas engine, the hot combustion gases (temperature, for example, 2,200C) originating from the burner device 13 flow along the pipes of the inner row 9' while giving off heat thereto, subsequently along the pipes of the outer row 9" while giving off heat thereto and after that, after having given off heat also to fins 12, they leave the engine via outlet 16.
The inner wall of the upper higher temperature part of cylinder 1 is provided with a heat-insulating layer of a glass ceramic material 17. Arranged about this cylinder part is a cooling jacket 18 comprising cooling ducts 19 through which a cooling liquid can flow.
Cooling jacket 18 is thermally shielded from the combustion gas space 1 l by heat-insulating material 20 and shield 21. By a suitable choice of the thermal leakage of the heat-insulating material, additional heat which originates from the combustion gases can be given off to the cooling liquid so that a higher cooling liquid temperature (for heating purposes) is achieved.
Regenerator 8 is accommodated in a housing 22, the inner wall of which is also provided with a layer of heatinsulating glass ceramic material, denoted by the reference numeral 23. A cooling jacket 24 comprising cooling ducts 25 is arranged about housing 22. The glass ceramic layers 17 and 23 shield the cooled cylinder wall and the cooled regenerator housing wall, respectively, from hot working medium under high pressure. Consequently, the operating temperature of cylinder 1 and regenerator housing 22 is low so that conventional materials can be used. The cooling jackets l8 and 24 ensure that the steep temperature gradient over the layers 17 and 23, viewed in the radial direction, is maintained and that no temperature equalization occurs in this direction in the course of time.
The hot-gas engine of FIG. 2 comprises four cylinders, 31, 32, 33 and 34, for four thermodynamic cycles. The regenerator and cooler associated with a given cycle are both situated in a common space, i.e., in the spaces 35, 36, 37 and 38, respectively. The four cylinders as well as the spaces for regenerator and cooler are arranged in a ring. Present in the space 37 of FIG. 3 is a regenerator 39 and a cooler 40. The spaces 35, 36
and 38 also accommodate a regenerator and a cooler which are not shown in the Figure.
The piston 41 reciprocates in cylinder 33. Present above the piston is an expansion space 42 which communicates with heater pipes 43, the other ends of which open into a duct 44. Present below piston 41 is a compression space 45 which communicates with a duct 46. Regenerator 39 has connected thereto heater pipes 47, the other end of which opens into duct 44. A duct 48 communicates with cooler 40.
In a double-acting engine, the expansion space of one cylinder communicates, via a heater, regenerator and cooler, with the compression space of another cylinder, the expansion space of said other cylinder communicating, again via a heater, regenerator and cooler, with the compression space of a next cylinder.
In the present case, expansion space 42 in cylinder 33 is in open communication, via heater pipes 43, duct 44, heater pipes 47, regenerator 39, cooler 40 and duct 48, with the compression space (not shown) in cylinder 34. Compression space 45 in cylinder 33 communicates, via duct 46, the cooler and regenerator (not shown) in space 36, and heater pipes (not shown), with the expansion space (not shown) in cylinder 32.
The heater pipes associated with the four thermodynamic cycles are arranged in a ring about a space 50 for combustion gases. The hot combustion gases originate from one central burner device 51, provided with an inlet for combustion air 52 and an inlet for fuel 53. An outlet 54 for combustion gases communicates with space 50. The inner walls of the cylinders 31 to 34 are covered with a layer of glass ceramic material, denoted by the reference numeral 55 for cylinder 33 in FIG. 3. Arranged about each cylinder is a cooling jacket 56 comprising an inlet and an outlet, 57 and 58, respectively, for cooling liquid.
At the area where they form the regenerator housing, the inner walls of spaces 35, 36, 37 and 38 (FIG. 2) are also covered with a layer of glass ceramic material 59. Provided about each of the regenerator housings is a cooling jacket 60 comprising an inlet and an outlet, 61 and 62, respectively, for cooling liquid.
The hot-gas reciprocating engine shown in FIG. 4 comprises two cylinders 70 and 71. Present in cylinder 70 is a displacer 72 which is provided with a heatinsulating displacer cap 73 of glass ceramic material. Via displacer rod 74, displacer 72 is connected to a crank shaft 75. Present in cylinder 71 is a piston 76 which is connected to crank shaft 75 via piston rod 77. Present above displacer 72 is the expansion space 78 86 to the heat-transmitting wall 84 where it evaporates again. The part of cylinder 70 which bounds expansion space 78 is again covered on the inner side with a layer of heat-insulating glass ceramic material, denoted by the reference 87. Similarly, the upper part of cylinder. 71, forming the housing for regenerator 80, is provided.
heat from these cylinder parts and the water vapour which communicates, via heater pipes 79, regenerator 80 and cooler 81, with compression space 82 above piston 76.
Heater pipes 79 are situated inside a heat pipe 83 which has a heat-transmitting wall 84 and which for the remainder is thermally insulated from the surroundings by means of a heat-insulating jacket 85. The inner wall of heat pipe 83 is covered with a capillary structure 86 which is formed, for example, by a gauze layer. Furthermore, the heat pipe 83 contains a quantity of sodium as the heat transport medium.
During operation, heat is given off to the sodium in the heat pipe via heattransmitting wall 84, with the result that the sodium evaporates. Sodium vapor subsequently flows to the heater pipes 79 and condenses thereon while giving off heat. Sodium condensate is returned by capillary action through capillary structure formed condenses on heat-transmitting wall 92 while giving off heat through this wall to the surroundings.
What is claimed is: 1. A hot-gas reciprocating engine, comprising at least one cylinder with an expansion space of variable volume and higher mean temperature during operation,
the said expansion space communicating, via a regenerator which is incorporated in a housing, with a compression space of variable volume and lower mean temperature during operation, characterized in that at least the part of the cylinder which bounds the expansion space and at least the part of the regenerator housing which envelops the regenerator part of higher temperature during operation facing the expansion space have inner walls which are each provided with at least one layer of a heat-insulating material which acts as a partition between the cylinder part and the expansion space and between the regenerator housing part and the regenerator part, respectively, cooling members being provided for maintaining a lower mean temperature of the said parts of cylinder and regenerator housing during operation.
2. A hot-gas reciprocating engine as claimed in claim 1, characterized in that the heat-insulating layer is made of a ceramic material, particularly a glass ceramic material.
3. a hot-gas reciprocating engine as claimed in claim 1, characterized in that the said parts of cylinder and regenerator housing are enveloped by a heat pipe as a cooling member, the said heat pipe containing a heat transport medium which completes an evaporationcondensation cycle during operation, evaporating taking place by taking up heat from the cylinder or the regenerator housing, whilst condensation takes place elsewhere on a heat-transmitting heat pipe wall while giving off heat to this wall.
4. A hot-gas reciprocating engine as claimed in claim 1, characterized in that the said parts of cylinder and regenerator housing are provided with a cooling jacket which comprises one or more ducts through which a cooling liquid can flow.
5. A hot-gas reciprocating engine as claimed in claim 4, characterized in that one or both cooling jackets are incorporated in a closed duct system in which the cooling liquid can circulate, the said duct system elsewhere comprising a heat exchanger in which the liquid can give off heat to the surroundings.
6. In a hot gas engine including a housing whose walls define variable volume expansion and compression cooling means for maintaining a mean temperature ofsaid first and second wall parts during operation of said apparatus lower than said higher mean temperature of said expansion space, whereby conventional materials may be used for said housing first and second wall parts.
7. Apparatus according to claim 6 wherein said heat insulating layer comprises a ceramic material such as glass. 7
8. Apparatus according to claim 6 wherein said first and second wall parts comprise heat pipes, each heat pipe containing a heat transport medium which completes an evaporation-condensation cycle during operation, with evaporation occurring when heat is transferred from said expansion space or regenerator to said heat pipe and condensation occurs when heat is transferred from said heat pipe outward thereof.
9. Apparatus according to claim 6 and operable with a source of cooling liquid, wherein said first and second wall parts comprise ducts therethrough, said apparatus further comprising means for flowing said cooling liquid through said ducts to cool said wall parts.