WO2018011693A1

WO2018011693A1 - Magnetic switch heat engine

Info

Publication number: WO2018011693A1
Application number: PCT/IB2017/054134
Authority: WO
Inventors: Shahid Khan; Divyanand GUPTA
Original assignee: Individual
Current assignee: Individual
Priority date: 2016-07-11
Filing date: 2017-07-10
Publication date: 2018-01-18
Anticipated expiration: 2019-01-11

Abstract

The present disclosure relates to a piston less Stirling heat engine that incorporates a magnetic switch. The disclosed heat engine is formed of an enclosed space holding a working fluid, and divided between a hot chamber to heat a working fluid and a cold chamber to cool the working fluid such that cyclic displacement of the working fluid from hot chamber to the cold chamber and back results in cyclic expansion and contraction of the working fluid. One end of the enclosed space incorporates a bellow that cyclically expands and contracts due to cyclic expansion and contraction of the working fluid thereby providing a reciprocating linear motion. A displacer positioned within the enclosed space is shuttled between the hot chamber and the cold chamber by means of a magnetic switch to displace the working fluid from one chamber to the other.

Description

MAGNETIC SWITCH HEAT ENGINE

FIELD OF DISCLOSURE

[0001] The present disclosure relates to heat engines. In particular, it pertains to apiston less Stirling engine.

BACKGROUND

[0002] The background description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.

[0003] Stirling engines are well-known. Originally conceived in 1816 it was meant to make an engine that was safer and more efficient than the steam engines that had been developed about a century before. However, rise of internal-combustion saw Stirling engines sidelined. However, they have become popular recently in solar power plants and other forms of renewable energy, where their higher efficiency is prized.

[0004] A Stirling engine operates by cyclic compression and expansion of a gaseous media (the working fluid) at different temperatures, such that there is a net conversion of heat energy to mechanical work. More specifically, the Stirling engine is a closed-cycle regenerative heat engine with a permanently gaseous working fluid. Closed-cycle, in this context, means a thermodynamic system in which the working fluid is permanently contained within the system, and regenerative describes the use of a specific type of internal heat exchanger and thermal store, known as the regenerator. The inclusion of a regenerator differentiates the Stirling engine from other closed cycle hot air engines.

[0005] Stirling engines provide benefits of quiet and efficient operation with option to use with clean fuels so that there is no harmful emission. Further, while an internal combustion engine, since it burns petroleum or some other fuel with air to produce the working fluid, which is then vented in the exhaust cycle, requires continuous working fluid replenishment. Stirling engines essentially operate on a fixed volume of working fluid or gas.

[0006] There are three major types of Stirling engines that are distinguished by the way they move the working fluid between the hot and cold areas. The alpha configuration has two power pistons, one in a hot cylinder, one in a cold cylinder, and the gas is driven between the two by the pistons; the pistons are typically placed in a V-formation with connecting rods joined at the same point on a crankshaft. The hot cylinder is situated inside a high temperature heat exchanger while the cold cylinder is situated inside a low temperature heat exchanger. This type of engine has a high power-to-volume ratio but usage of piston, crankshaft etc. leads to high friction losses.

[0007] The beta configuration has a single cylinder with a hot end and a cold end, containing a power piston and a 'displacer'. The displacer drives the working fluid between the hot and cold ends and a single power piston is arranged within the same cylinder on the same shaft as the displacer piston. It is typically used with a rhombic drive to achieve the phase difference between the displacer and power piston, usually joined 90 degrees out of phase on a crankshaft. The displacer piston is a loose fit and serves to shuttle the fluid between the hot and cold heat exchangers. When the fluid is pushed to the hot end of the cylinder it expands and pushes the power piston. When it is pushed to the cold end of the cylinder it contracts and the momentum of the machine, usually enhanced by a flywheel pushes the power piston the other way to compress the fluid. Unlike the alpha type, the beta type avoids the technical problems of hot moving seals. The rhombic drive is, however, of high complexity and tight tolerances, causing a high cost of manufacture. So heat engines with such a configuration have not found wide use.

[0008] The gamma configuration has two cylinders: one containing a displacer, with a hot and a cold end, and one for the power piston; they are joined to form a single space with the same pressure in both cylinders; the pistons are typically in parallel and joined 90 degrees out of phase on a crankshaft. Essentially, it is like a beta Stirling engine in which the power piston is mounted in a separate cylinder alongside the displacer piston cylinder, but is still connected to the same crankshaft and flywheel. The gas in the two cylinders can flow freely between them and remains a single body. While this leads to a mechanically simpler construction, it produces a lower compression ratio because of the volume of connection between the two cylinders.

[0009] Configurations as elaborated above suffer from limitations of using piston, flywheel and linkages etc. with attended complexity, wear and tear and friction losses. Beta and gamma configurations use same cylinder for hot and cold sections and so, a high temperature difference between the two (and corresponding high thermal efficiency) is not possible. Further, their output has to be used inside engines themselves otherwise leakage occurs and generally they require expensive high pressure helium as working fluid.

[00010] There is therefore, a need in the art for a Stirling heat engine that overcomes deficiencies of the known configurations so that potential of the Stirling engine could be fully utilized.

[00011] All publications herein are incorporated by reference to the same extent as if each individual publication or patent application were specifically and individually indicated to be incorporated by reference. Where a definition or use of a term in an incorporated reference is inconsistent or contrary to the definition of that term provided herein, the definition of that term provided herein applies and the definition of that term in the reference does not apply.

[00012] In some embodiments, the numbers expressing quantities of ingredients, properties such as concentration, reaction conditions, and so forth, used to describe and claim certain embodiments of the invention are to be understood as being modified in some instances by the term "about." Accordingly, in some embodiments, the numerical parameters set forth in the written description and attached claims are approximations that can vary depending upon the desired properties sought to be obtained by a particular embodiment. In some embodiments, the numerical parameters should be construed in light of the number of reported significant digits and by applying ordinary rounding techniques. Notwithstanding that the numerical ranges and parameters setting forth the broad scope of some embodiments of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as practicable. The numerical values presented in some embodiments of the invention may contain certain errors necessarily resulting from the standard deviation found in their respective testing measurements.

[00013] As used in the description herein and throughout the claims that follow, the meaning of "a," "an," and "the" includes plural reference unless the context clearly dictates otherwise. Also, as used in the description herein, the meaning of "in" includes "in" and "on" unless the context clearly dictates otherwise.

[00014] The recitation of ranges of values herein is merely intended to serve as a shorthand method of referring individually to each separate value falling within the range. Unless otherwise indicated herein, each individual value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g. "such as") provided with respect to certain embodiments herein is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention otherwise claimed. No language in the specification should be construed as indicating any non-claimed element essential to the practice of the invention.

[00015] Groupings of alternative elements or embodiments of the invention disclosed herein are not to be construed as limitations. Each group member can be referred to and claimed individually or in any combination with other members of the group or other elements found herein. One or more members of a group can be included in, or deleted from, a group for reasons of convenience and/or patentability. When any such inclusion or deletion occurs, the specification is herein deemed to contain the group as modified thus fulfilling the written description of all Markush groups used in the appended claims.

OBJECTS OF THE INVENTION

[00016] It is an object of the present disclosure to provide a Stirling heat engine that overcomes deficiencies of the known configurations.

[00017] It is an object of the present disclosure to provide a Stirling heat engine that does not use moving parts that are subject to wear and tear with high friction losses and result in lowering efficiency of the engine.

[00018] It is another object of the present disclosure to provide a heat engine with high thermal efficiency.

[00019] It is yet another object of the present disclosure to provide a heat engine that is not prone to leakages.

[00020] It is yet another object of the present disclosure to provide a heat engine that uses inexpensive and readily available materials as working fluids.

[00021] It is yet another object of the present disclosure to provide a heat engine that is simple in construction yet is highly efficient. SUMMARY

[00022] Aspects of the present disclosure generally relate to a heat engine. The disclosed heat engine is a heat to linear motion converter through magnetic switching. In particular, the present disclosure provides a piston-less Stirling heat engine that can convert heat energy into mechanical work with minimum frictional losses and, therefore, enables tapping potential of Stirling engine as an efficient heat to mechanical power conversion mechanism.

[00023] In an aspect, heat engine of the present disclosure contains working fluid (also referred to as fluid and the terms used interchangeably hereinafter) in a tube shaped container (also referred hereinafter as enclosed space or tube and the terms used interchangeably hereinafter) that is sealed at one end and has a bellow attached to the other end. Thus the tube sealed at one end and having the bellow at its other end forms a sealed and closed working space for the working fluid to expand and contract without any exchange/transfer from outside. In an aspect, the bellow attached to the tube enables expansion of the working fluid contained within the tube and also contraction of the working fluid when cooled. In an embodiment, the bellow can be an elastic metal bellow or high temperature rubber diaphragm.

[00024] In an embodiment, the bellow can also convert the increase and decrease in volume of the fluid into mechanical work by transferring linear displacement and associated force to a suitably configured part so that mechanical energy developed by the engine can be drawn for gainful utilization. Thus the bellow replaces a piston which is employed in known Stirling engines, by taking over its role. As can be seen, replacement of a piston by bellow eliminates frictional losses that take place during reciprocating motion of the piston in conventional Stirling engines making it more efficient.

[00025] In an aspect, the enclosed space (or the container or the tube) is divided in two sections -a hot section or chamber and a cold chamber. The hot chamber can be on the sealed side of the tube. In an aspect, the enclosed space/container/tube and its two chambers can be formed by joining two blocks such that each block defines one of the two chambers i.e. hot chamber and the cold chamber.

[00026] In an aspect, the two blocks can be insulated to each other through copper welded ceramic ring such that the ceramic ring prevents transfer and consequent loss of heat energy by conduction from the block forming hot chamber to the block forming the cold chamber. [00027] In an aspect, the block forming the hot chamber can be configured to receive a hot media so as to heat the working fluid contained within the hot chamber. Alternatively, the hot chamber can be heated by means of a heat source attached to external surface of the hot chamber Likewise the block forming the hot chamber can be configured with a heat sink attached to its external surface of the cold chamber so that the fluid in the cold chamber can be cooled.

[00028] In an aspect, during working of the engine, volume of the working fluid is increased on account of heating in the hot chamber resulting in expansion of the bellow. The hot fluid is then transferred to the cold chamber where it is cooled resulting in decreases in volume causing the bellow to contract. After the contraction the fluid is moved back to the hot chamber for repetition of the heating - cooling cycle and resultant expansion - contraction cycle of the bellow. This expansion and contraction of the bellow is used for converting heat energy into mechanical work.

[00029] In an aspect, transfer of the fluid from the hot chamber to the cold chamber and vice versa is facilitated by a displacer. In an embodiment, a ceramic displacer of length equal to the cold chamber is placed in the tube and is loosely fitted in the center through a center rod so as to provide an annular gap between the inner surface of the tube and the displacer. The annular gap between the inner surface of the tube and the displacer can work as passage for the working fluid to move from one chamber to the other chamber.

[00030] In another aspect, the displacer can be shuttled between the hot chamber and the cold chamber for the fluid to get transferred from one chamber to the other through gap between the displacer and the chambers.

[00031] In an aspect, means to shuttle the displacer between the hot chamber and the cold chamber to move the fluid from one to other can be a magnetic switch. The magnetic switch can comprise of a round disc shaped magnet attached at the bottom of the displacer and an annular magnet attached at the top of the diaphragm/bellow. Inner diameter of the annular magnet can be greater than the disc magnet to enable the disc magnet to pass through the annular magnet. The magnets can be arranged to repel each other i.e. same poles of the two magnets face each other irrespective whether the disc magnet is above or below the annular magnet. During working the disc magnet and the annular magnet move along with displacer and the bellow respectively - moving closer to each other against the repulsive forces under force of the expanding/contracting working fluid acting on the bellow. At one stage the disc magnet crosses the annular magnet and the direction of the repulsive forces changes which causes the displacer to shuttle resulting in a fast transfer of the fluid from one chamber to the other.

[00032] Thus the disclosed piston-less configuration of the heat engine incorporating magnetic switching and thermal separation of the hot chamber and the cold chamber leads to manifold advantages such as high mechanical efficiency on account of frictionless working, no wear and tear as there being no piston moving parts do not come in contact with one another, high thermal efficiency, no leakage of the fluid and possibility of using economical fluid.

[00033] Various objects, features, aspects and advantages of the present disclosure will become more apparent from the following detailed description of preferred embodiments, along with the accompanying drawing figures in which like numerals represent like features.

BRIEF DESCRIPTION OF THE DRAWINGS

[00034] The accompanying drawings are included to provide a further understanding of the present disclosure, and are incorporated in and constitute a part of this specification. The drawings illustrate exemplary embodiments of the present disclosure and, together with the description, serve to explain the principles of the present disclosure.

[00035] The diagrams are for illustration only, which thus is not a limitation of the present disclosure, and wherein:

[00036] FIG. 1 illustrates an exemplary sectional view of the piston less heat engine in accordance with an exemplary embodiment of the present disclosure.

[00037] FIG. 2A to FIG. 2E illustrate exemplary sectional views elaborating working of the disclosed heat engine in accordance with an exemplary embodiment of the present disclosure.

[00038] FIG. 3 illustrates an exemplary sectional view of magnetic switch in accordance to an exemplary embodiment of the present disclosure.

[00039] FIG. 4 illustrates an exemplary arrangement of magnetic switch with the Stirling engine in accordance with an embodiment of the present disclosure.

[00040] FIG. 5 illustrates an exemplary arrangement of Hall Effect sensor inside the magnetic switch designed in accordance with an embodiment of the present disclosure.

[00041] FIG. 6 illustrates an exemplary arrangement of LVDT with a metal foundation inside the bellow in accordance with an embodiment of the present disclosure. DETAILED DESCRIPTION

[00042] The following is a detailed description of embodiments of the disclosure depicted in the accompanying drawings. The embodiments are in such detail as to clearly communicate the disclosure. However, the amount of detail offered is not intended to limit the anticipated variations of embodiments; on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present disclosure as defined by the appended claims.

[00043] Each of the appended claims defines a separate invention, which for infringement purposes is recognized as including equivalents to the various elements or limitations specified in the claims. Depending on the context, all references below to the "invention" may in some cases refer to certain specific embodiments only. In other cases it will be recognized that references to the "invention" will refer to subject matter recited in one or more, but not necessarily all, of the claims.

[00044] Various terms as used herein are shown below. To the extent a term used in a claim is not defined below, it should be given the broadest definition persons in the pertinent art have given that term as reflected in printed publications and issued patents at the time of filing.

[00045] Embodiments of the present disclosure relate to a piston less heat engine that uses magnetic switching to convert heat to linear motion convertor. In particularly the present disclosure provides a piston-less Stirling heat engine that can convert heat energy into mechanical work with minimum frictional losses.

[00046] In an embodiment, the disclosed heat engine uses a tube shaped closed container to accommodate a working fluid to cyclically expand and contract the fluid by heating and cooling. The cyclic expansion and contraction of the fluid drives an elastic metal bellow or high temperature rubber diaphragm attached to one end of the closed container to provide cyclic linear to and fro motion which can be converted to mechanical energy using suitable means.

[00047] In an embodiment, the closed container can be tube shaped sealed at one end and having the bellow at its other end thus forming a sealed and closed working space for the working fluid to expand and contract without any exchange/transfer from outside. In an aspect, the bellow attached to the tube enables expansion of the working fluid contained within the tube and also contraction of the working fluid when cooled. Thus the bellow replaces a piston which is employed in known Stirling engines, by taking over its role. As can be seen, replacement of a piston by bellow eliminates frictional losses that take place during reciprocating motion of the piston in conventional Stirling engines making it more efficient.

[00048] In an aspect, the sealed container holding the working fluid can be divided in two sections. A hot section or chamber and a cold chamber; and the hot chamber can be on the sealed side of the tube. In an aspect, the container and its two chambers can be formed by joining two suitably shaped blocks, and the two blocks can be insulated to each other through copper welded ceramic ring such that the ceramic ring can prevent transfer and consequent loss of heat energy by conduction from the block forming hot chamber to the block forming the cold chamber.

[00049] In an aspect, the block forming the hot chamber can be configured to receive and circulate a hot media so as to heat the working fluid contained within the hot chamber. Alternatively, the hot chamber can be heated by means of a heat source attached to external surface of the hot chamber Likewise the block forming the hot chamber can be configured with a heat sink attached to its external surface of the cold chamber so that the fluid in the cold chamber can be cooled.

[00050] In an aspect, during working of the engine volume of the working fluid is increased on account of heating in the hot chamber resulting in expansion of the bellow. The hot fluid is then quickly transferred to the cold chamber where it is cooled resulting in decreases in volume causing the bellow to contract. After the contraction the fluid is quickly moved back to the hot chamber for repetition of the heating - cooling cycle and resultant expansion - contraction cycle of the bellow. This expansion and contraction of the bellow is used for converting heat energy into mechanical work.

[00051] In an aspect, transfer of the fluid from the hot chamber to the cold chamber and vice versa is facilitated by a displacer of length equal to the cold chamber. The displacer is placed in the chambers and is concentrically but loosely fitted in the center through a center rod such that an annular gap remains between the displacer and inner walls of the chambers. In an embodiment, the displacer is shuttled between the hot chamber and the cold chamber to facilitate quick transfer of the fluid from one chamber to other through the annular gap between the displacer and the chambers.

[00052] In an aspect, means to shuttle the displacer between the hot chamber and the cold chamber to move the fluid from one to other is a magnetic switch. The magnetic switch can comprise of a round disc shaped magnet attached at the bottom of the displacer and an annular magnet attached at the top of the diaphragm. Inner diameter of the annular magnet can be greater than the disc magnet to enable the disc magnet to pass through the annular magnet. The magnets are arranged to repel each other. During working the disc magnet and the annular magnet move along with displacer and the bellow - moving closer to each other against the repulsive forces under forces acting on the bellow. At one stage the disc magnet crosses the annular magnet and the direction of the repulsive forces changes which causes the displacer to quickly shuttle from one chamber to other resulting in a quick and fast transfer of the working fluid from one chamber to the other.

[00053] Thus the disclosed piston-less configuration of the heat engine incorporating magnetic switching and thermal separation of the hot chamber and the cold chamber leads to manifold advantages such as high mechanical efficiency on account of frictionless working, no wear and tear as there being no piston moving parts do not come in contact with one another, high thermal efficiency, no leakage of the fluid and possibility of using economical fluid.

[00054] Referring now to FIG. 1 wherein an exemplary sectional view of the disclosed piston less heat engine 100 is disclosed. As shown the heat enginelOO can be configured around a tubular enclosed space 102(also referred to as tube 102 or container 102 and both the terms used interchangeably hereinafter) that can be closed at its top end and can have a bellow 104 at its lower end thus providing a sealed enclosed space for holding a working fluid and allowing the fluid to expand and contract by heating and cooling.

[00055] In an embodiment, the bellow 104 can be an elastic metal bellow or high temperature rubber diaphragm. In an aspect, the bellow 104 can serve as a friction free displacement device as replacement of a piston in conventional Stirling heat engines so that there is no friction loss as there is no contact between the expanding device and the inside walls of the enclosed space holding the expanding-contracting fluid. This aspect makes the present heat engine more efficient as compared to known Stirling heat engines.

[00056] In an aspect, the working fluid contained within the tube 102 can be any suitable fluid that increases in volume when heated and decreases in volume when cooled. In exemplary embodiments, the working fluid can be one selected from a group comprising air, steam and helium.

[00057] In an embodiment, the tube 102 can be divided into a hot chamber 108 and a cold chamber 110. The two chambers 108 and 110 can be formed by joining two blocks and the two blocks can be insulated to each other through an isolator 112. Isolator 112 can keep the blocks forming hot chamber 108 and cold chamber 110 thermally isolated from one another. The isolator 112can, in an exemplary embodiment, be a copper welded ceramic ring.

[00058] In an embodiment, the hot chamber 108 can be configured to enable its heating by a suitable heat source. The means to heat the hot chamber 108 can be attached to its external surface. Alternatively, the hot chamber 108 can be surrounded by a hot fluid circulator 132 into which any suitable hot matter that can be a liquid or gas can circulate via inletl l2a and outletl 12b as shown in FIG. 1.

[00059] In an embodiment, the cold chamber 110 can be configured to quickly cool hot fluid which it receives from hot chamber 108. For this purpose, in an exemplary embodiment and as illustrated in FIG. 1, cold chamber 110 can have a heat sink 126 that can be in form a plurality of heat conducting fins attached to external surface of cold chamber 110.

[00060] In an embodiment, the disclosed heat engine can further incorporate adisplacerl 18 positioned concentrically but loosely within the tube 102 in such a fashion that it can move freely between the cold chamber 110 and the hot chamber 108. In an exemplary embodiment, displacer 118 can be of length equal to that of cold chamber 110. Smooth movement of the displacer 118 between the chambers can be facilitated by a center rod 120 suitably placed within the tube 102 such as through a plate 128 and a flexure bearing 122. The center rod 120 also helps in positioning the displacer 118 concentrically within the tube 102 leaving an annular gap between the displacer 118 and the inner walls of the tube 102. The annular gap can provide passage for the working fluid to move from one chamber to other during shuttling of the displacer 118 or during expansion/contraction of the fluid during heating/cooling.

[00061] In an embodiment, movement of the displacer 118 from the hot chamber 108 to cold chamber 110 and vice versa can result in displacement of the working fluid and its consequent movement from the cold chamber to the hot or vice versa as the case may be through the annular gap between the displacer and the wall of the chambers.

[00062] In an embodiment, the disclosed heat engine 100 can further incorporate means to shuttle the displacer between the hot chamber 108 and the cold chamber 110 to move the fluid from one to other at appropriate time during the heating-cooling cycle. And the shuttling of the displacer from one chamber to other can take place at the end of corresponding heating or cooling cycle. For example the displacer 118 can shuttle from the hot chamber 108 to the cold chamber 110 when the working fluid is fully heated and accordingly the bellow 104 has reached extreme position of linear motion. Likewise, the displacer 118 can shuttle from the cold chamber 110 to the hot chamber 108 when the working fluid is fully cooled and accordingly the bellow 104 has reached other extreme position of its linear motion

[00063] In an embodiment, the means to shuttle the displacer 118 between the hot chamber 108 and the cold chamber 110 can be a magnetic switch. The magnetic switch can comprise a round disc shaped magnet 124 attached at the bottom of the displacer 118 and an annular magnet 116 attached at the top of the bellow 104. The two magnets can be appropriately positioned to ensure shuttling action of the displacer 118 at the appropriate time of the heating/cooling cycle as explained above.

[00064] To facilitate fitment of the annular magnet 116 at the top of the bellow 104, the bellow 104 can have a platform 106 at its end away from bottom end of tube 102 and two extensions such as 114a and 114b can extend from the platform to hold the annular magnet 116 such that it is coaxial to tube 102 and extends some distance into cold chamber 110 as shown in FIG. 1. In the exemplary embodiment shown in FIG. 1, the extensions 114 can be configured to pass through slots 130 configured in the plate 128 attached to lower end of tube 102 to enable positioning of the annular magnet 116 in the desired position.

[00065] Inner diameter of the annular magnet 116 can be greater than the disc magnet 124 to enable the disc magnet 124 to pass through the annular magnet 116. The magnets can be arranged to repel each other. During working the disc magnet 124 and the annular magnet 116 move along with displacer 118 and the bellow 104 - moving closer to each other against the repulsive forces under forces due to expanding or contracting working fluid acting on the bellow 104. At one stage the disc magnet ^λ 124 crosses the annular magnet 116 and the direction of the repulsive forces changes which causes the displacer 118 to shuttle and resulting in a fast transfer of the fluid from one chamber to the other. As can be appreciated by those skilled in art, the point where the disc magnet ' 124 crosses the annular magnet 116 is crucial from the point of controlling shuttling of the displacer 118 at appropriate time in the cycle, and it is controlled by positioning of the two magnets relative to the bellow 104 and the displacer 118. In exemplary implementations, based on capacity heat source heating the hot chamber, speed of displacer and size of displace can be configured. [00066] In an aspect, various components of heat engine disclosed can be made of any materials suitable. In exemplary embodiments, the extensions 114a and 114 b and the hot fluid circulator 132 can be but not limited to Stainless Steel 304, hot chamber 108 can be of copper, the isolator 112 of ceramic, the heat sink 126 of aluminum fins, the displacer 118 of ceramic, the center rod 120 of Stainless Steel 304, the blocks forming tube 102 of Stainless Steel 304, annular magnet 116 and disc magnet 124 of NdFeB (alloy of neodymium, iron and boron that is used to make strongest type of permanent magnets presently available ), expansion bellow 104 of metal welded ring type and platform 106 of SS 304. However, the suggested materials are only exemplary and any other material meeting the desired requirements can be used without any limitations.

[00067] To work the disclosed heat engine 100, hot chamber 108 can be heated by circulating hot fluid through hot fluid circulator 132. On heating, the fluid in the hot chamber 108 can expand due which bellow 104 can expand downward to accommodate this increased volume. As bellow 104 expands, platform 106 can move away from hot chamber 108 in a downward direction, thereby moving and the annular magnet 116 also down. As a result of which annular magnet 116 can come closer to disc magnet 124. Annular magnet 116 and disc magnet 124 can be so configured on the extensions 114 and rod 120 that at a predefined length of downward stroke of bellow 104, annular magnet 116 aligns with disc magnet 124, annular magnet 116 moving in downward direction. This point can be termed as "breaking" of 'magnetic switch' formed by the two ring magnets. As soon as annular magnet 116 moves further down, disc magnet 124 can now be on upper side of annular magnet 116 and outside extensions 114. As soon as that happens, the ring magnets being configured to repel each other, disc magnet 124 can move upwards, pushing displacer 118 very quickly from cold chamber 110 into hot chamber 108, displacer 118 being held loosely by flexure bearing 122. The process of using ring magnets as elaborated herein to produce such an upward movement of displacer 118 can be called magnetic switching.

[00068] In another aspect, as soon as displacer 118 moves up and into hot chamber 108, it displaces hot fluid from the hot chamber 108 to the cold chamber 110. As hot fluid enters cold chamber 110 it can quickly cool and contract. Accordingly, bellowl04 can contract upwards. As bellow 104 contracts upwards, platform 106 and annular magnet 116 can move up towards disc magnet 124. [00069] The annular magnet 116 and disc magnet 124 can be so configured on extensionsl l4 and rod 120 that after a predefined length of upward stroke of bellow 104 the annular magnet 116 moving in upward direction aligns with disc magnet 124. This point can be termed as "breaking" of the 'magnetic switch'. As soon as annular magnet 116 moves further up, the disc magnet 124 can now be on lower side of annular magnet 116. As soon as that happens, the magnets being configured to repel each other, the disc magnet 124 can move downward, pulling displacer 118 very quickly downward from hot chamber 108 into cold chamber 110 moving the fluid from the cold chamber 110 to the hot chamber 108. Thus the magnetic switch enables to shuttle the displacer between the hot chamber 108 and the cold chamber 110 at precise moment in the cycle of heating and cooling of the fluid and thereby transfers the fluid from one chamber to other as required.

[00070] As displacer 118 comes back to its original position, the consequent movement of the fluid form the cold chamber 110 to the hot chamber 108 can result in repetition of the heating-cooling cycle and attended expansion and contraction of the bellow 104. The expansion and contraction results in a linear reciprocating motion of the bellow 104 which can be tapped for any mechanical work or conversion to other forms of energy.

[00071] FIG. 2 A to FIG. 2E illustrate exemplary sectional views elaborating working of the disclosed heat engine 100 in accordance with an exemplary embodiment of the present disclosure. A complete cycle of working of heat engine 100 is elaborated through FIG. 2A to FIG. 2E. FIG. 2A illustrates a position wherein the displacer is in cold chamber HOwith the working fluid filling the hot chamber 108. The disc magnet 124 is below the annular magnet 116.

[00072] Starting from the position illustrated in FIG. 2A if the hot chamber 108 is heated, the fluid can start expanding resulting in the bellow 104 expanding downwards under pressure of the expanding working fluid pushing platform 106 away from cold chamber 110 and bringing disc magnet 124 closer to annular magnet 116. As explained earlier, the annular magnet 116 and disc magnet 124 can be so configured on extensions 114 and rod 120 respectively that at a predefined length of downward stroke of the bellow 104, annular magnet 116 aligns with disc magnetl24 as shown in FIG. 2B. At this point the two magnets are at the point of crossing each other, that is, the magnetic switch is at the point of being broken. A further movement of the bellow 104 beyond this point shall result in reversal of repulsive forces between the two magnets i.e. repulsive forces which were so far tending to move the displacer 118 in the same direction as of bellow 104, shall after the breaking point make the displacer 118 to move in opposite direction i.e. upwards of the illustrated position. Thus the displacer 118 shall now shuttle to the hot chamber 108.

[00073] FIG.2C illustrates the position soon after the displacer 118 has shuttled to the hot chamber 108 and shows the bellow 104 in fully expanded condition, the disc magnet 124 is now on upper side of annular magnet 116. The working fluid has been displaced by the displacer 118 from the hot chamber 108 to the cold chamber 110. The two ring magnets being configured to repel each other, disc magnet 124 is pushing displacer 118 very quickly from cold chamber 110 into hot chamber 108. As displacer 118 moves up and into hot chamber 108, it can displace hot fluid from the hot chamber 108 to the cold chamber 110. FIG. 2C also illustrates how upward movement of displacer 118 is being handled by flexure bearing 122.

[00074] FIG. 2D illustrates position as the hot fluid after entering the cold chamber 110 starts getting cooled. The working fluid gets quickly cooled in the cold chamber HOand its volume decreases. Accordingly, bellow 104 contracts upwards moving the platform 106 and along with it the annular magnet 116 upwards closer to the disc magnet 124. The annular magnet 116 and the disc magnet 124 can be so configured on the extensions 114 and the rod 120 that at a predefined length of upward stroke of the bellow 104, the annular magnet 116 aligns with the disc magnetl24.FIG. 2D illustrates this position when the two magnets are at the point of crossing each other, that is, the magnetic switch is at the point of being broken.

[00075] FIG.2E illustrates position after the magnetic switch has broken causing the displacer 118 to move out of the hot chamber 108 and shuttling to the cold chamber 110 with resultant displacement of the cooled working fluid from the cold chamber 110 to the hot chamber 108. The disc magnet 124 is now on lower side of the annular magnet 116. This completes one working cycle of heat engine 100 and this cycle can repeat itself, as long as hot chamber 108 is heated and cold chamber 110 cooled.

[00076] Further improvement in the efficiency of the Stirling engine can be achieved with alternative design changes. FIG. 3 illustrates an exemplary sectional view of magnetic switch in accordance to an exemplary embodiment of the present disclosure. As shown in FIG. 3, the magnetic switch can include a first plate 302 that can be attached to the displacer through screw holes, a second plate 304 that can be attached to expiation bellow bottom which is movable, and an outer cage 306 of switch that can be attached to top platform of the engine which is unmovable. In an exemplary implementation, hot chamber of the enclosure can also include pair of magnets, magnet 308a and magnet 308b arranged with opposite polarity.

[00077] FIG. 4 illustrates an exemplary arrangement of magnetic switch with the Stirling engine in accordance with an embodiment of the present disclosure. In an exemplary implementation, magnetic switch 402 (same as magnetic switch 300) can be arranged to enabled movement of the displacer. Cold chamber of the enclosure can be fixed with a stationary platform 404 so as to hold the enclosure while the displacer inside the enclosure moves with due to expansion/contraction and magnetic switch 402.

[00078] In an exemplary implementation, in order to enable adjustment of stoke length, which generally cannot be obtained using permanent ring magnet as earlier that generate fixed magnetic field, electromagnetic coil can be used, whose magnetic field can be adjusted by controlling current through a MOSFET or PWM. Use of electromagnetic coil also enables controlling of stroke power as the displacer moves. In an exemplary implementation, current to electromagnetic coil can be controlled through a programmable microcontroller, which can enable the engine to achieve a variable magnetic field, variable power stroke, variable stroke length, smooth and sudden stroke control, cog free operation. Use of electromagnetic coil can also overall cost of engine as cost of electromagnetic coil in comparison to permanent magnet is low.

[00079] In an exemplary implementation, to achieve highly precise, efficient and controlled Stirling engine, the engine can be configured with an electronic control system. The Stirling engine can include a coil cylinder with Hall Effect sensor, cylindrical magnet with central hole attached coaxially with displacer, an linear variable differential transformer(LVDT) attached to the bellow or diaphragm for position and speed measurement, MOSFET based power stage controller for controlling electromagnetic effect and a wireless communication interface (for example GPRS, or WiFi) for monitoring data received from Hall Effect sensors and LVDT and for monitoring functioning of the system from a remote location. In an exemplary implementation, Hall Effect sensor, for example OH090U, can be used to detect magnets edge in order to detect precise high speed magnet movement (literal or rotary). Any other circuit/sensor (such as Maxim-Board Mounted Hall Effect Integrated Circuit) can also be configured to enable the function of Hall Effect. [00080] FIG. 5 illustrates an exemplary arrangement of Hall Effect sensor inside the magnetic switch designed in accordance with an embodiment of the present disclosure. As shown in FIG. 5, one or more Hall Effect sensor, for example sensor 502a and sensor 502b, can be arranged in particular interval to detect position of circular magnet driving the displacer. The Hall effect sensor can provide TTL latch type output that can be received from the electronic control system.

[00081] FIG. 6 illustrates an exemplary arrangement of LVDT with a metal foundation inside the bellow in accordance with an embodiment of the present disclosure. As shown in FIG. 6, LVDT 602 can be attached inside the bellow over a metallic foundation 604. As one may appreciate, the linear variable differential transformer (LVDT) (also called just a differential transformer, linear variable displacement transformer, or linear variable displacement transducer) is a type of electrical transformer used for measuring linear displacement (position). The ability to achieve a high-frequency response combined with a long mechanical cycle life cannot be provided by other types of displacement sensors; those operating on digital principles may not be able to meet the response rate, while potentiometer types have a limited life. LVDTs, especially unguided types, are said to have an effectively infinite life, as well as the ability to respond to mechanical oscillations at up to 1 kHz. In order to provide digital sampling of an LVDT that is performing at its highest frequency, digital sampling rates of 100,000 per second would be considered appropriate.

[00082] In an exemplary implementation, the metal-oxide-semiconductor field-effect transistor (MOSFET, MOS-FET, or MOS FET) based power stage controller can be a type of transistor used for amplifying or switching electronic signals. As one may appreciate, MOSFET is very low power consuming unit and provides high speed switching with variable resistance controlled by the control system.

[00083] In an exemplary implementation, the electronic control system, which can be a ATMEGA 128 microcontroller, of Stirling engine can receive reading of diaphragm position through LVDT. The electronic control system/Microcontroller waits until the diaphragm expands and keep the MOSFET bus in tri - state. As soon as diaphragm expands up to a predefined level, then microcontroller start the MOSFET bus alternately in pair and through the centre magnet (which is connected to the displacer via a hollow pipe) to the top position. Microcontroller detects the top position of the magnet through Hall Effect sensor and can apply electromagnetic break by controlling the magnetic field of the electromagnet through MOSFETs.

[00084] Now as the displacer is at top position therefore all the expanded gas/fluid is at the bellow cylinder which is a cold cylinder, here gas/fluid will contract hence diaphragm will also contract. Now microcontroller read the diaphragm position through LVDT and when the diaphragm reaches to its ideal position then again microcontroller start the MOSFET BUS in opposite direction. When the centre magnet reaches to downward, its position will be send to the microcontroller via Hall Effect sensor. Now microcontroller applies electromagnetic break to stop the displacer.

[00085] As can be seen the disclosed heat enginelOO does not use any piston to convert expansion-contraction of the working fluid to a reciprocating motion and thus is devoid of frictional losses that occur in conventional engines that employ pistons. It also overcomes problem of wear, tear and leakages associated with moving parts moving relative to each other while in contact. Consequently, mechanical efficiency as well as lifetime of the heat enginelOO can superior to conventional heat engines.

[00086] Further, the heat engine 100 of the present disclosure uses magnetic switching as means to shuttle displacer between hot and cold chamber thereby quickly and swiftly moving working fluid from one chamber to other at designated point in the heating - cooling cycle. This provides for a very fast, contact less shuttling of fluid between hot chamber and cold chamber thereby leading to higher mechanical efficiency.

[00087] Furthermore the heat engine 100 of the present disclosure provides for separate hot and cold chambers that are thermally isolated using an isolator. The disclosed configuration prevents loss of heat on account of conduction from hot side to cold side of the engine thereby enhancing thermal efficiency of the engine by enabling high temperature difference between the hot and the cold zones of the engine.

[00088] In an embodiment, the mechanical output being delivered by the heat engine 100 of the present disclosure is completely outside the heat engine and therefore, can be coupled directly to rotary or linear devices such as linear alternator, rotary alternator, water pumps etc. without any leakages of fluid within.

[00089] In an embodiment, the heat engine 100 of the present disclosure can use water as working fluid and water can undergo phase change i.e. from liquid to vapor during heating and back from vapor to liquid during cooling thus providing very high ratio between expanded and contracted volumes. Further, water being a dense recyclable fuel can provide high output power. Besides, it is inexpensive.

[00090] While the foregoing describes various embodiments of the invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof. The scope of the invention is determined by the claims that follow. The invention is not limited to the described embodiments, versions or examples, which are included to enable a person having ordinary skill in the art to make and use the invention when combined with information and knowledge available to the person having ordinary skill in the art.

ADVANTAGES OF THE INVENTION

[00091] The present disclosure provides a Stirling heat engine that overcomes deficiencies of the known configurations.

[00092] The present disclosure provides a Stirling heat engine that does not use moving parts that are subject to wear and tear with high friction losses and result in lowering efficiency of the engine.

[00093] The present disclosure provides a heat engine with high thermal efficiency.

[00094] The present disclosure provides a heat engine that is not prone to leakages.

[00095] The present disclosure provides a heat engine that uses inexpensive and readily available materials as working fluids.

[00096] The present disclosure provides a heat engine that is simple in construction yet is highly efficient.

Claims

We Claim:

1. A heat engine comprising:

an enclosed space divided between a hot chamber and a cold chamber holding within it a working fluid, wherein the hot chamber is configured to heat the working fluid and the cold chamber is configured to cool the working fluid such that cyclic displacement of the working fluid from hot chamber to the cold chamber and back results in cyclic expansion and contraction of the working fluid; and

a displacer configured to shuttle between the hot chamber and the cold chamber at appropriate point of the cyclic expansion and contraction of the working fluid thereby displacing the working fluid from one chamber to the other;

wherein one side of the enclosed space is closed by a bellow that cyclically expands and contracts due to cyclic expansion and contraction of the working fluid thereby providing a reciprocating linear motion.

2. The heat engine of claim 1, wherein the shuttling of the displacer between the hot chamber and the cold chamber at appropriate point of the cyclic expansion and contraction of the working fluid is done by a magnetic switch.

3. The heat engine of claim 1, wherein the enclosed space is formed by joining two blocks; wherein each of the two blocks defines one of the hot chamber and the cold chamber.

4. The heat engine of claim 2, wherein the two blocks are thermally insulated to prevent loss of heat from the hot chamber to the cold chamber.

5. The heat engine of claim 3, wherein the thermal insulation of the two blocks is done through a copper welded ceramic ring.

6. The heat engine of claim 3, wherein the block defining the hot chamber is configured to receive and circulate a hot media to heat the working fluid contained within the hot chamber.

7. The heat engine of claim 1, wherein the working fluid in the hot chamber is heated by means of a heat source attached to external surface of the hot chamber.

8. The heat engine of claim 1, wherein the fluid in the cold chamber is cooled by means of a heat sink attached to external surface of the cold chamber.

9. The heat engine of claim 1, wherein the bellow is selected out of a group comprising of metal bellow and high temperature rubber diaphragm.

10. The heat engine of claim 1, wherein the working fluid is selected from a group comprising air, steam, water and helium.