MICRO-SCALE ENGINES, COMPONENTS, AND METHODS FOR GENERATING POWER
Heat engines suitable for large-scale or micro-scale fabrication supply power from a power turbine. The power turbine is driven in part by an ejector in which a working fluid is utilized as a motive flow. Fuel utilized for combustion may also be utilized as a phase-changing working fluid and as the motive flow driving the ejector. Heat exchangers particularly suitable for micro-scale implementation are also disclosed.
This application claims the benefit of U.S. Provisional Patent Application Ser. No. 61/335,087, filed Dec. 31, 2009, titled “NOVEL THERMODYNAMIC CYCLES, ENGINES IMPLEMENTING SAME, METHODS FOR FABRICATING ENGINES, AND METHODS FOR GENERATING POWER,” which is incorporated by reference herein in its entirety.
TECHNICAL FIELDThe present invention relates generally to thermodynamic cycles and engines or power plants implementing such thermodynamic cycles, including microfabricated engines or power plants.
BACKGROUNDOver the last ten years there has been an active effort to develop hydrocarbon-fueled power generation and propulsion systems on the scale of centimeters or smaller (small-scale, or micro-scale). Potential applications for micro-scale hydrocarbon-fueled power plants include those currently utilizing electrochemical batteries (e.g., lithium, lithium ion, nickel metal hydride, etc.) as energy sources. Thus, micro-scale hydrocarbon-fueled power plants are being investigated as alternatives to batteries, and more generally as energy sources for powering various kinds of micro-scale devices and systems (e.g., portable electronic devices, sensors, actuators, small vehicles and satellites, etc.). Generally, high power density portable systems have the potential for enabling new technologies as well as improving run times for existing systems requiring electrical power. High power density devices may enable designers to package the power plant and fuel needed to meet system requirements with minimal volume. While energy can be stored in many ways (chemical, mechanical, potential, nuclear), chemical energy densities far exceed any other modality (except for nuclear). Consequently, the heat engine continues to be considered a desirable method for transferring chemical energy potential into work. A typical heat engine includes a source of heat energy, a gas turbine for producing the work output, and one or more heat exchangers.
The power output of a gas turbine engine scales with length squared, and the volume scales with length cubed. Therefore, the power density scales with the inverse of length, resulting in increasing power densities as device size decreases. However, the realization of micro-scale engines is currently limited by existing microfabrication technology. Microfabrication may be based on many of the materials and techniques (e.g., vacuum deposition and crystal growth, etching techniques, micromachining, etc.) utilized in fields relating to MEMS (micro-electro-mechanical systems), microelectronics and microfluidics. To reduce the complexity and cost of microfabrication, there is a need for engine designs that minimize the number of moving parts. Moreover, the thermodynamic cycles implemented by conventional large-scale engines and power plants are not necessarily optimal when implemented at the micro-scale.
In view of the foregoing, there is an ongoing need for improved thermodynamic cycles as may be implemented for providing sources of power. This need exists generally for engines (or power plants) at any scale. This need exists in particular for micro-scale (e.g., microfabricated) engines. There is also a need for improved micro-scale engine designs and associated components.
There is also a need for micro-scale heat exchangers that can be implemented in a practical and effective manner. Known micro-scale heat exchanger configurations cannot be implemented without a major compromise to performance or manufacturing complexity. In the fluid passages of a heat exchanger, there exists an optimum length-to-diameter (or hydraulic diameter) ratio (or aspect ratio) that determines optimal performance. This length-to-diameter ratio is scale-independent and based solely on flow parameters and material properties, except at length scales at which viscous losses inhibit performance and require adjustment of flow parameters or length scale to decrease viscous losses. As the characteristic length scale of a heat exchanger decreases, the length-to-diameter ratio required for optimal performance may require flow passage lengths that are unable to be packaged conveniently into compact or micro-scale devices. Thus there is a need for heat exchanger configurations that are better suited for micro-scale implementations.
SUMMARYTo address the foregoing problems, in whole or in part, and/or other problems that may have been observed by persons skilled in the art, the present disclosure provides methods, processes, systems, apparatus, instruments, and/or devices, as described by way of example in implementations set forth below.
According to one implementation, a heat engine includes a combustor, a power turbine, a boiler, an ejector, a condenser, and an injector. The combustor includes a fuel inlet, an air inlet and an exhaust outlet. The power turbine communicates with the exhaust outlet, wherein the power turbine is driven to rotate by exhaust gas from the combustor. The boiler includes a high-temperature boiler circuit in thermal contact with a low-temperature boiler circuit for transferring heat thereto. The high-temperature boiler circuit communicates with the power turbine for receiving exhaust gas therefrom. The ejector includes a first ejector inlet communicating with the low-temperature boiler circuit for receiving a flow of vaporized working fluid therefrom, a second ejector inlet communicating with the high-temperature boiler circuit for receiving exhaust gas therefrom, and an ejector outlet. The ejector is configured for entraining the exhaust gas from the second ejector inlet in the flow of vaporized working fluid from the first ejector inlet, and increasing a pressure drop across the power turbine. The condenser includes a high-temperature condenser circuit in thermal contact with a low-temperature condenser circuit for transferring heat thereto. The high-temperature condenser circuit communicates with the ejector outlet. The low-temperature condenser circuit is configured for flowing a cold fluid through the condenser. The injector includes an injector liquid inlet communicating with the high-temperature condenser circuit for receiving condensed working fluid therefrom, and an injector outlet communicating with the low-temperature boiler circuit. The injector is configured for flowing liquid-phase working fluid to the boiler.
According to another implementation, the heat engine includes a turbocharger and a compressor. The turbocharger is rotatable about a spool and communicates with the exhaust outlet, wherein the turbocharger is driven to rotate by exhaust gas from the combustor. The power turbine includes a turbine inlet communicating with the turbocharger and is driven to rotate by exhaust gas from the turbocharger. The compressor is rotatable about the spool wherein the compressor is driven to rotate by the turbocharger. The compressor includes a compressor inlet for aspirating ambient air, and a compressor outlet communicating with the air inlet wherein the compressor feeds compressed air to the combustor.
According to another implementation, the heat engine includes a recuperator. The recuperator includes a high-temperature recuperator circuit in thermal contact with a low-temperature recuperator circuit for transferring heat thereto. The high-temperature recuperator circuit is interposed between the power turbine and the high-temperature boiler circuit, and the low-temperature recuperator circuit is disposed in upstream fluid communication with the air inlet, wherein the recuperator is configured for pre-heating air fed to the combustor.
According to another implementation, the heat engine includes a recuperator. The recuperator includes a high-temperature recuperator circuit in thermal contact with a low-temperature recuperator circuit for transferring heat thereto. The high-temperature recuperator circuit is interposed between the ejector outlet and the high-temperature condenser circuit, and the low-temperature recuperator circuit is interposed between the injector outlet and the low-temperature boiler circuit, wherein the recuperator is configured for pre-heating the working fluid fed to the boiler.
According to another implementation, a heat engine includes a combustor, a turbocharger, a compressor, a power turbine, a recuperator, a boiler, an ejector, a condenser, and an injector. The combustor includes a fuel inlet, an air inlet and an exhaust outlet. The turbocharger is rotatable about a spool and communicates with the air inlet wherein the turbocharger feeds air to the combustor. The compressor is rotatable about the spool wherein the compressor is driven to rotate by the turbocharger. The compressor includes a compressor inlet for aspirating ambient air. The power turbine is rotatable about a turbine axis and comprises a turbine inlet communicating with the compressor wherein the power turbine is driven to rotate by compressed air from the compressor. The recuperator includes a high-temperature recuperator circuit in thermal contact with a low-temperature recuperator circuit for transferring heat thereto. The high-temperature recuperator circuit communicates with the exhaust outlet. The low-temperature recuperator circuit is interposed between the power turbine and the turbocharger, wherein the turbocharger is driven to rotate by heated air from the recuperator. The boiler includes a high-temperature boiler circuit in thermal contact with a low-temperature boiler circuit for transferring heat thereto. The high-temperature boiler circuit communicates with the high-temperature recuperator circuit for receiving exhaust gas therefrom. The ejector includes a first ejector inlet communicating with the low-temperature boiler circuit for receiving a flow of vaporized working fluid therefrom, a second ejector inlet communicating with the high-temperature boiler circuit for receiving exhaust gas therefrom, and an ejector outlet. The ejector is configured for entraining the exhaust gas from the second ejector inlet in the flow of vaporized working fluid from the first ejector inlet and increasing a pressure drop across the power turbine. The condenser includes a high-temperature condenser circuit in thermal contact with a low-temperature condenser circuit for transferring heat thereto. The high-temperature condenser circuit communicates with the ejector outlet. The low-temperature condenser circuit is configured for flowing a cold fluid through the condenser. The injector includes an injector liquid inlet communicating with the high-temperature condenser circuit for receiving condensed working fluid therefrom, and an injector outlet communicating with the low-temperature boiler circuit. The injector is configured for flowing liquid-phase working fluid to the boiler.
According to another implementation, the recuperator communicating with the turbocharger is a first recuperator, and the heat engine further includes a second recuperator. The second recuperator comprises a high-temperature second recuperator circuit in thermal contact with a low-temperature second recuperator circuit for transferring heat thereto. The high-temperature second recuperator circuit is interposed between the ejector outlet and the high-temperature condenser circuit, and the low-temperature second recuperator circuit interposed between the injector outlet and the low-temperature boiler circuit, wherein the second recuperator is configured for pre-heating the working fluid fed to the boiler.
According to another implementation, a method is provided for generating power. An exhaust gas including combustion products is flowed from a power turbine to a boiler. A working fluid is vaporized by flowing the working fluid through the boiler while flowing the exhaust gas through the boiler, wherein heat is transferred from the exhaust gas to the working fluid. The vaporized working fluid is flowed through an ejector. The exhaust gas is entrained in the vaporized working fluid as the vaporized working fluid flows through the ejector by flowing the exhaust gas from the boiler into the ejector. Entrainment of the exhaust gas creates suction downstream of the power turbine. The working fluid discharged from the ejector is condensed and returned to the boiler for vaporization by the exhaust gas flowing through the boiler. The power turbine is driven to rotate by flowing the exhaust gas to the turbine from a combustor disposed upstream of the power turbine, and by creating the suction in the exhaust gas downstream of the power turbine.
According to another implementation, a turbocharger is interposed between the combustor and the power turbine and a compressor is rotatable on a common spool with the turbocharger. The turbocharger and the compressor are driven to rotate by flowing the exhaust gas from the combustor to the turbocharger, wherein the power turbine is driven by exhaust gas discharged from the turbocharger. Compressed air from the compressor is fed to the combustor for combustion with a fuel.
According to another implementation, a method is provided for generating power. An exhaust gas including combustion products is flowed from a combustor to a recuperator. While flowing the exhaust gas through the recuperator, air discharged from a power turbine is flowed through the recuperator wherein heat is transferred from the exhaust gas to the air. The exhaust gas is flowed from the recuperator to a boiler. A working fluid is vaporized by flowing the working fluid through the boiler while flowing the exhaust gas through the boiler, wherein heat is transferred from the exhaust gas to the working fluid. The vaporized working fluid is flowed through an ejector. The exhaust gas is entrained in the vaporized working fluid as the vaporized working fluid flows through the ejector by flowing the exhaust gas from the boiler into the ejector, wherein entrainment of the exhaust gas creates suction downstream of the power turbine. The working fluid discharged from the ejector is condensed and returned to the boiler for vaporization by the exhaust gas flowing through the boiler. A turbocharger and a compressor are driven to rotate by flowing the heated air from the recuperator to the turbocharger, wherein the compressor rotates on a common spool with the turbocharger. The power turbine is driven to rotate by flowing compressed air from the compressor to the power turbine.
In any of the implementations disclosed herein, the working fluid may be a hydrocarbon fuel. In some implementations, vaporized working fluid is flowed from the boiler to the combustor to supply the combustor with fuel for combustion with air.
According to another implementation, a heat exchanger includes a plurality of hot fluid plates stacked in series along a longitudinal direction, and a cold fluid circuit. Each hot fluid plate has a thickness in the longitudinal direction and a planar area in a transverse plane orthogonal to the longitudinal direction. Each hot fluid plate includes a central hole, a hot fluid inlet hole and a hot fluid outlet hole formed through the thickness. The hot fluid inlet hole and the hot fluid outlet hole are located at respective radial distances from the central hole. Each hot fluid plate further includes a transverse channel running in the transverse plane from the hot fluid inlet hole, around the central hole and to the hot fluid outlet hole. The cold fluid circuit runs from a cold fluid inlet to a cold fluid outlet in thermal contact with the transverse channels. The central holes are aligned with each other along the longitudinal direction. The hot fluid inlet holes are aligned with each other along the longitudinal direction, forming a hot fluid inlet plenum. The hot fluid outlet holes are aligned with each other along the longitudinal direction, forming a hot fluid outlet plenum. The transverse channels establish a plurality of transverse flow paths from the hot fluid inlet plenum to the hot fluid outlet plenum.
In some implementations, the hot fluid plates each have a thickness on the order of micrometers.
According to another implementation, a heat exchanger includes a plurality of hot fluid plates and a plurality of cold fluid plates. Each hot fluid plate has a thickness in a longitudinal direction and a planar area in a transverse plane orthogonal to the longitudinal direction. Each hot fluid plate includes a central hole, a hot fluid outlet hole, a cold fluid inlet hole and a cold fluid outlet hole formed through the thickness. The hot fluid outlet hole, the cold fluid inlet hole and the cold fluid outlet hole are located at respective radial distances from the central hole. Each hot fluid plate further includes a hot fluid transverse channel running in the transverse plane from the central hole and radially outward therefrom, around the central hole and to the hot fluid outlet hole. Each cold fluid plate has a thickness in the longitudinal direction and a planar area in the transverse plane. Each cold fluid plate includes a central hole, a hot fluid outlet hole, a cold fluid inlet hole and a cold fluid outlet hole formed through the thickness. Each cold fluid plate further includes a cold fluid transverse channel running in the transverse plane from the cold fluid inlet hole, around the central hole and to the cold fluid outlet hole. The hot fluid plates and the cold fluid plates are stacked along the longitudinal direction in alternating series with each other such that each hot fluid plate is adjacent to at least one of the cold fluid plates and each hot fluid transverse channel is in thermal contact with at least one of the cold fluid transverse channels. The central holes of the hot fluid plates and the cold fluid plates are aligned with each other along the longitudinal direction, forming a hot fluid inlet plenum. The hot fluid outlet holes of the hot fluid plates and the cold fluid plates are aligned with each other along the longitudinal direction, forming a hot fluid outlet plenum. The cold fluid inlet holes of the hot fluid plates and the cold fluid plates are aligned with each other along the longitudinal direction, forming a cold fluid inlet plenum. The cold fluid outlet holes of the hot fluid plates and the cold fluid plates are aligned with each other along the longitudinal direction, forming a cold fluid outlet plenum. The hot fluid transverse channels establish a plurality of transverse flow paths from the hot fluid inlet plenum to the hot fluid outlet plenum. The cold fluid transverse channels establish a plurality of transverse flow paths from the cold fluid inlet plenum to the cold fluid outlet plenum.
In some implementations, the hot fluid plates and the cold fluid plates each have a thickness on the order of micrometers.
Other devices, apparatus, systems, methods, features and advantages of the invention will be or will become apparent to one with skill in the art upon examination of the following figures and detailed description. It is intended that all such additional systems, methods, features and advantages be included within this description, be within the scope of the invention, and be protected by the accompanying claims.
The invention can be better understood by referring to the following figures. The components in the figures are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention. In the figures, like reference numerals designate corresponding parts throughout the different views.
As used herein, the term “micro-scale” generally applies to engines in which at least some of the structural features of the operative components (e.g., turbine, pump or compressor, heat exchanger, etc.) have dimensions on the order of microns (micrometers). One or more overall dimensions (e.g., total length, width, height, diameter, thickness, etc.) of the operative components, however, may be on the order of millimeters or centimeters. Such engines may be referred to as micro-scale engines or microengines. A microengine may be utilized as a power supply for a wide variety of small devices, including for example small vehicles and portable electronic devices.
As used herein, the term “macro-scale” or “large-scale” generally applies to engines larger than microengines, including engines of an industrial scale such as may be implemented as a power plant for powering large devices, vehicles, etc., supplying power to a building, supplying power to a power grid that distributes power over a geographical area, etc.
As used herein, the term “fluid” encompasses a liquid (liquid-phase material), a gas (gas-phase material or vapor), a supercritical fluid, or a mixture of two or more of the foregoing, unless a particular fluid is specifically indicated as being a liquid, gas (or vapor), or supercritical fluid. Depending on the context, a liquid may also be referred to as a condensate. A liquid may or may not contain a gas component (e.g., vapor or bubbles). A gas may or may not contain a liquid component. A supercritical fluid may, at least temporarily, fall below its critical point (with respect to temperature and/or pressure) such that the supercritical fluid at least partially includes a liquid-phase or gas-phase component.
In
The combustor 102 may be of any type suitable for initiating and maintaining a fuel-air combustion reaction and outputting the resulting exhaust gases containing the combustion products. The combustor 102 includes a fuel inlet 132, an air inlet 134 and an exhaust outlet 136. Also shown is an input of heat energy Q to the combustor 102 utilized for ignition such as, for example, a spark plug or glow plug, a resistive wire, filament, needle, plate, electrode, etc. The combustor 102 generally includes a combustion chamber having a volume appropriate for the size of the heat engine 100 (i.e., macro-scale or micro-scale). In some implementations, a catalyst may be provided in the combustion chamber to promote the combustion reaction. Non-limiting examples of catalysts include noble metals such as, for example, platinum and palladium. The catalyst may be supported by any suitable substrate such, for example, a nickel foam.
The turbocharger 104 includes a turbine structure rotatable about a turbine axis, a housing (not shown) enclosing the turbine structure, a turbocharger inlet 142 and a turbocharger outlet 144. In the present example, the turbine axis is schematically depicted as a shaft or spool 146 but may alternatively be configured as a disk. The turbine structure may include a rotor of any suitable design that is connected to (or integrated with) the spool 146 and supports turbine vanes or blades. The housing may include or serve as a stator and may or may not include stationary vanes. Generally, the turbine and housing cooperatively define fluid flow paths through the turbine structure from the turbocharger inlet 142 to the turbocharger outlet 144. The implementations described herein are not limited to any particular design of the turbocharger 104. Various designs of gas turbines at both the macro-scale and micro-scale level are known to persons skilled in the art. In the present implementation, the exhaust outlet 136 of the combustor 102 communicates with the turbocharger inlet 142 over an exhaust gas line. Accordingly, the turbocharger 104 is driven to rotate by the flow of hot exhaust gas produced by the combustor 102.
The compressor 106 includes a compressor structure rotatable about a compressor axis, a housing (not shown) enclosing the compressor structure, a compressor inlet 152 and a compressor outlet 154. In the present example, the compressor axis is collinear with the turbine axis, i.e., the schematically depicted spool 146 is common to both the turbocharger 104 and the compressor 106. Accordingly, the compressor 106 in this example is driven to rotate by the torque transferred from the rotating turbocharger 104 via the spool 146. The compressor structure may include a rotor of any suitable design that is connected to (or integrated with) the spool 146 and supporting compressor vanes or fan-type blades. For example, the spool 146 may be provided in the form of a compressor rotor and a turbocharger rotor interconnected by a bearing-supported shaft or hub, or the spool 146 may be a bearing supported disk-type structure of which one side serves as the compressor rotor and the opposite side serves as the turbocharger rotor. In some implementations, the compressor 106 may have an axial-flow or rotary vane type of design. The housing may include or serve as a stator and may or may not include stationary vanes. Depending on design, an integral housing may be structured to enclose both the compressor 106 and the turbocharger 104. Generally, the compressor 106 and housing cooperatively define fluid flow paths through the compressor structure from the compressor inlet 152 to the compressor outlet 154. The implementations described herein are not limited to any particular design of the compressor 106. Various designs of gas compressors at both the macro-scale and micro-scale level are known to persons skilled in the art. The compressor inlet 152 is configured to receive (aspirate) air from the ambient environment in which the heat engine 100 operates. The compressor outlet 154 is in fluid communication with the air inlet 134 to feed compressed air to the combustor 102, either directly or after pre-heating as described below.
The power turbine 108 includes a turbine structure rotatable about a power turbine axis, a housing (not shown) enclosing the turbine structure, a power turbine inlet 158 and a power turbine outlet 160. The power turbine axis may be a shaft, spool, disk or other rotating element (not shown). The power turbine axis may or may not be in-line with the turbocharger axis. In the present implementation, the power turbine 108 is not mechanically referenced to either the turbocharger 104 or the compressor 106. The turbine structure of the power turbine 108 may include a rotor and vanes or blades and generally may be similar to that of the turbocharger 104. The housing may include or serve as a stator and may or may not include stationary vanes. Generally, the turbine and housing cooperatively define fluid flow paths through the turbine structure from the power turbine inlet 158 to the power turbine outlet 160. In the present implementation, the turbocharger outlet 144 is in fluid communication with the power turbine inlet 158 over a turbocharger exhaust gas line. Accordingly, the power turbine 108 is driven to rotate by the flow of hot exhaust gas outputted from the turbocharger 104. Also shown schematically is a work output W produced by the power turbine 108. In a typical implementation, the work output W is torque produced by a rotating component of the power turbine 108 such as the shaft that rotates about the turbine axis. Depending on the use of the heat engine 100, the work output W may be coupled to any device via any appropriate transmission or transducer to supply power to that device.
Additional examples of turbines, compressors, pumps and other rotatable components that may generally be suitable for use in micro-scale versions of the heat engines described herein are described in U.S. Pat. Nos. 5,932,540; 6,392,313; and 7,074,016; each of which is incorporated by reference herein in its entirety.
In the present implementation, the heat engine 100 may further include a recuperator 118. The recuperator 118 includes a heat exchanger structure that generally includes a high-temperature recuperator circuit 164 and a low-temperature recuperator circuit 166. In the present context, “high temperature” generally means that a hot fluid flows through the high-temperature recuperator circuit 164 and “low temperature” generally means that a cold fluid (“cold” being relative to the hot fluid) flows through the low-temperature recuperator circuit 166, and that heat is transferred from the hot fluid to the cold fluid via the heat exchanger structure due to the temperature differential between the hot fluid and the cold fluid. The high-temperature recuperator circuit 164 runs from a hot fluid recuperator inlet 168 to a hot fluid recuperator outlet 170, and the low-temperature recuperator circuit 166 runs from a cold fluid recuperator inlet 172 to a cold fluid recuperator outlet 174. The circuits 164, 166 are configured as any suitable type of passages through which fluids flow. The fluid flow path(s) running through the high-temperature recuperator circuit 164 is physically separate from the fluid flow path(s) running through the low-temperature recuperator circuit 166. The heat exchanger structure is configured such that the high-temperature recuperator circuit 164 is in thermal contact with the low-temperature recuperator circuit 166, whereby heat is transferred from the fluid flowing in the high-temperature recuperator circuit 164 to the fluid flowing in the low-temperature recuperator circuit 166 in the direction(s) of temperature gradients resulting from the configuration. For this purpose, the heat exchanger structure may have any suitable configuration such as, for example, tube-shell, stack of thin-walled plates, etc.
As appreciated by persons skilled in the art, the fluid passages provided by the high-temperature recuperator circuit 164 and/or the low-temperature recuperator circuit 166 may be multi-directional (e.g., serpentine, labyrinthine, helical, etc.) as desired for maximizing heat transfer. As also appreciated by persons skilled in the art, while the high-temperature recuperator circuit 164 is illustrated as being in a counterflow relation with the low-temperature recuperator circuit 166, alternative configurations such as concurrent flow, cross-flow, combinations of different types of flow arrangements, and variations of such flow arrangements may be suitable.
In the present implementation, the hot fluid recuperator inlet 168 is in fluid communication with the power turbine outlet 160 over a power turbine exhaust gas line. The hot fluid recuperator outlet 170 is in fluid communication with the boiler 110 over a recuperator exhaust gas line. The cold fluid recuperator inlet 172 is in fluid communication with the compressor outlet 154 and thus receives the compressed air from the compressor 106. The cold fluid recuperator outlet 174 is in fluid communication with the air inlet 134 of the combustor 102. By this configuration, the hot exhaust gas received from the power turbine 108 flows through the high-temperature recuperator circuit 164, while the air received from the compressor 106 flows through the low-temperature recuperator circuit 166. While these flows occur, heat is transferred from the hot exhaust gas to the air and the resulting pre-heated air is fed to the combustor 102.
In the present context of heat exchangers, it will be appreciated that the terms “hot” and “cold,” and “high-temperature” and “low-temperature,” are being used in a relative sense to distinguish between different circuits of a given heat exchanger and the flow paths associated with the different circuits, and also to indicate which circuit gives up heat and which circuit receives heat during operation. It will be noted that in the high-temperature recuperator circuit 164, the temperature of the exhaust gas at the hot fluid recuperator inlet 168 is “high” relative to the temperature of the exhaust gas at the hot fluid recuperator outlet 170 due to the loss of heat to the low-temperature recuperator circuit 166. In the low-temperature recuperator circuit 166, the temperature of the air at the cold fluid recuperator outlet 174 is “high” relative to the temperature of the air at the cold fluid recuperator inlet 172 due to the deposition of heat from the high-temperature recuperator circuit 164. These labeling conventions also apply to other heat exchangers of the heat engine 100 such as the boiler 110 and condenser 114.
The boiler 110 includes a heat exchanger structure that generally includes a high-temperature boiler circuit 178 and a low-temperature boiler circuit 180. The high-temperature boiler circuit 178 runs from a hot fluid boiler inlet 182 to a hot fluid boiler outlet 184, and the low-temperature boiler circuit 180 runs from a cold fluid boiler inlet 186 to a cold fluid boiler outlet 188. The fluid flow path(s) running through the high-temperature boiler circuit 178 is physically separate from the fluid flow path(s) running through the low-temperature boiler circuit 180. The heat exchanger structure is configured such that the high-temperature boiler circuit 178 is in thermal contact with the low-temperature boiler circuit 180, whereby heat is transferred from the fluid flowing in the high-temperature boiler circuit 178 to the fluid flowing in the low-temperature boiler circuit 180. As in the case of the recuperator 118, the heat exchanger structure of the boiler 110 may have any suitable configuration (tube-shell, stack of thin-walled plates, etc.), one or more of the fluid passages may be multi-directional, and the flow arrangement may be a counterflow or other arrangement.
The hot fluid boiler inlet 182 is in fluid communication with the hot fluid recuperator outlet 170 over the recuperator exhaust gas line. The hot fluid boiler outlet 184 is in fluid communication with the ejector 112 over a boiler exhaust gas line. The cold fluid boiler inlet 186 is in fluid communication with the injector 116 over a liquid working fluid line to receive a liquid-phase (or a mixture of liquid-phase and gas-phase) working fluid to be heated and vaporized by the boiler 110. The cold fluid boiler outlet 188 is in fluid communication with the ejector 112 over a working fluid gas (or vapor) line. By this configuration, the hot exhaust gas received from the recuperator 118 flows through the high-temperature boiler circuit 178, while the working fluid received from the injector 116 flows through the low-temperature boiler circuit 180. While these flows occur, heat is transferred from the hot exhaust gas to the working fluid and the resulting pressurized and boiled (or vaporized) working fluid is fed to the ejector 112.
The ejector 112 includes an ejector structure, a first ejector inlet 194, a second ejector inlet 196, and an ejector outlet 198. The first ejector inlet 194 is in fluid communication with the high temperature boiler outlet 188 via the working fluid gas line, whereby the vaporized working fluid is flowed through the ejector structure as a motive flow. The second ejector inlet 196 is in fluid communication with the hot fluid boiler outlet 184 for feeding the exhaust gas to the ejector 112. The ejector structure may include a nozzle 202 into which the first ejector inlet 194 leads, whereby these components operate as a gas jet. The ejector structure may also include an exhaust gas inlet plenum 204 (or smoke box) into which the second ejector inlet 196 leads. The second ejector inlet 196 may be oriented at an angle relative to the first ejector inlet 194 such that the exhaust gas flow into the ejector 112 from the second ejector inlet 196 is at an angle (in some advantageous implementations, a ninety-degree angle) to the vaporized working fluid flow from the first ejector inlet 194. By this configuration, the motive flow of the vaporized working fluid reduces the pressure in the exhaust gas inlet plenum 204, thereby inducing flow of the exhaust gas toward the motive flow such that the exhaust gas becomes entrained in the motive flow by viscous effects. Consequently, the operation of the ejector 112 creates suction on the outlet side of the power turbine 108 that increases the pressure drop across the power turbine 108. In this manner, the power turbine 108 is driven in part by the fluid flow through the ejector 112. The resulting hot ejector gas (i.e., the mixture of vaporized working fluid and exhaust gas) is ejected from the ejector outlet 198 and into a hot ejector gas outlet line. The ejector structure may include a diffuser 206 leading to the ejector outlet 198. As appreciated by persons skilled in the art, the nozzle 202, the diffuser 206 or both may have converging and/or diverging sections.
In the present implementation the heat engine 100 may further include another recuperator 120, which is between the ejector 112 and the condenser 114. The recuperator 120 includes a heat exchanger structure that generally includes a high-temperature recuperator circuit 212 and a low-temperature recuperator circuit 214. The high-temperature recuperator circuit 212 runs from a hot fluid recuperator inlet 216 to a hot fluid recuperator outlet 218, and the low-temperature recuperator circuit 214 runs from a cold fluid recuperator inlet 220 to a cold fluid recuperator outlet 222. The fluid flow path(s) running through the high-temperature recuperator circuit 212 is physically separate from the fluid flow path(s) running through the low-temperature recuperator circuit 214. The heat exchanger structure is configured such that the high-temperature recuperator circuit 212 is in thermal contact with the low-temperature recuperator circuit 214, whereby heat is transferred from the fluid flowing in the high-temperature recuperator circuit 212 to the fluid flowing in the low-temperature recuperator circuit 214. As in the case of the other recuperator 118, the heat exchanger structure of this recuperator 120 may have any suitable configuration (tube-shell, stack of thin-walled plates, etc.), one or more of the fluid passages may be multi-directional, and the flow arrangement may be a counterflow or other arrangement.
The hot fluid recuperator inlet 216 is in fluid communication with the ejector outlet 198 over the hot ejector gas outlet line. The hot fluid recuperator outlet 218 is in fluid communication with the condenser 114 over a hot gas condenser inlet line. The cold fluid recuperator inlet 220 is in fluid communication with the injector 116 and thus receives working fluid from the injector 116. The cold fluid recuperator outlet 222 is in fluid communication with the boiler 110. By this configuration, the hot ejector gas (mixture of vaporized working fluid and exhaust gas) received from the ejector 112 flows through the high-temperature recuperator circuit 212, while the working fluid received from the injector 116 flows through the low-temperature recuperator circuit 214. While these flows occur, heat is transferred from the hot gas to the working fluid and the resulting pre-heated working fluid is fed to the boiler 110 to assist in vaporizing the working fluid. Moreover, the ejector gas is pre-cooled prior to being fed to the condenser 114.
In implementations where the heat engine 100 provides both recuperators 118 and 120, the recuperator 118 between the power turbine 108 and the boiler 110 may be referred to as the first recuperator, and the recuperator 120 between the ejector 112 and the condenser 114 may be referred to as the second recuperator.
The condenser 114 includes a heat exchanger structure that generally includes a high-temperature condenser circuit 226 and a low-temperature condenser circuit 228. The high-temperature condenser circuit 226 runs from a hot fluid condenser inlet 230 to a hot fluid condenser outlet 232, and the low-temperature condenser circuit 228 runs from a cold fluid condenser inlet 234 to a cold fluid condenser outlet 236. The fluid flow path(s) running through the high-temperature condenser circuit 226 is physically separate from the fluid flow path(s) running through the low-temperature condenser circuit 228. The heat exchanger structure is configured such that the high-temperature condenser circuit 226 is in thermal contact with the low-temperature condenser circuit 228, whereby heat is transferred from the fluid flowing in the high-temperature condenser circuit 226 to the fluid flowing in the low-temperature condenser circuit 228. As in the case of the other heat exchangers described above, the heat exchanger structure of the condenser 114 may have any suitable configuration (tube-shell, stack of thin-walled plates, cooling fins, etc.), one or more of the fluid passages may be multi-directional, and the flow arrangement may be a counterflow or other arrangement.
The hot fluid condenser inlet 230 is in fluid communication with the hot fluid recuperator outlet 218 over the hot gas condenser inlet line. The hot fluid condenser outlet 232 is in fluid communication with the injector 116. The cold fluid condenser inlet 234 and the cold fluid condenser outlet 236 are in fluid communication with the ambient environment whereby ambient air flows through the low-temperature condenser circuit 228. By this configuration, the hot ejector gas received from the recuperator 120 flows through the high-temperature condenser circuit 226 while cool air is flowed through the low-temperature condenser circuit 228. While these flows occur, heat is transferred from the hot ejector gas to the air by an amount sufficient to condense the vaporized working fluid and any condensable components of the exhaust gas. The resulting condensate, including liquid-phase working fluid, is fed to the injector 116 for injection into the boiler 110.
Alternatively, a heat exchanging medium other than air (e.g., water, etc.) may be flowed through the low-temperature condenser circuit 228. The use of ambient air, however, is relatively simple to implement and ambient air serves as an effective heat exchanging medium for many implementations of the heat engine 100.
The heat engine 100 may include a tank 240 between the condenser 114 and the injector 116. The tank 240 includes a tank volume, a tank inlet 244 in fluid communication with the hot fluid condenser outlet 232 over a condensate line, and a tank outlet 246 in fluid communication with the injector 116 over a working fluid liquid line. The tank volume may serve as a reservoir for condensate received from the condenser 114. The tank volume may also include a liquid-gas separation device (liquid-gas separator) interposed between the tank inlet 244 and the tank outlet 246. The liquid-gas separation device may be of any suitable known design that functions to separate any non-condensible portion of the fluid received from the condenser from the condensed portion. In some implementations, the liquid-gas separation device may simply be a vent to atmosphere. Also shown is an outlet line 248 for removal or discharge of the non-condensible fluid from the tank 240.
The injector 116 includes an injector structure, one or more injector liquid inlets 254, 256, and an injector outlet 258. The injector 116 may have any suitable configuration for injecting liquid-phase working fluid to the boiler 110. In some implementations, a reservoir is in fluid communication with the injector 116 to provide a supply of working fluid thereto. For example, the tank 240 may serve as the reservoir in which case the tank 240 communicates with the injector liquid inlet 256 over the working fluid liquid line. In some implementations, the injector structure is configured similar to the ejector structure, and thus may include an inlet plenum between a nozzle and a diffuser, either or both of which may include converging and diverging sections. The injector structure may further include a combining (or mixing) cone between the nozzle and the diffuser. The injector structure may be configured as a Giffard-type injector. In these latter cases, the injector may include another injector gas inlet 254 communicating with the nozzle oriented so as to flow gas at an angle to the liquid working fluid received from the tank 240. The vaporized working fluid outputted from the boiler 110 may be utilized as the motive flow through the injector 116 in the same manner as the ejector 112. Accordingly, the injector gas inlet 254 may be in fluid communication with the high temperature boiler outlet 188 via another working fluid gas line, whereby the vaporized working fluid is flowed through the injector structure and draws in the liquid working fluid. The injector 116 injects the liquid working fluid (or mixture of liquid working fluid and vaporized working fluid) into the boiler 110 from the injector outlet 258 (which may be done via a diffuser). In implementations providing the recuperator 120, the working fluid is first fed to the cold fluid recuperator inlet 220 via a recuperator inlet line, is pre-heated by the recuperator 120, and then is fed to the boiler 110 from the cold fluid recuperator outlet 222 via a boiler inlet line.
The working fluid generally may be any suitable heat transfer medium that is readily evaporated in the boiler 110 and condensable in the condenser 114. For instance, the working fluid may be water. In some advantageous implementations, the working fluid is a hydrocarbon fuel such as, for example, ethanol, methanol, kerosene, jet fuel, or RP-8 (kerosene-based rocket fuel, military specification). At the present time, ethanol in particular has been found suitable for the heat engine 100, particularly in micro-scale implementations. In addition to being utilized as a phase-changing working fluid and as a motive flow for the ejector 112 (and also the injector 116 in some implementations), the ethanol or other hydrocarbon fuel may be utilized as the fuel for combustion. For this purpose, in the illustrated implementation the cold fluid boiler outlet 188 is shown as also being in fluid communication with the fuel inlet 132 of the combustor 102 over a fuel supply line, whereby vaporized fuel is supplied to the combustor 102. In this manner, the injector 116 is utilized to recycle the unburned fuel that condenses out from the exhaust gas condensibles by running the unburned fuel through the boiler 110 for vaporization and for downstream use as a motive flow, and as the fuel for combustion. Alternatively or additionally, the combustor 102 may also receive a fresh supply of fuel from a reservoir (not shown).
In some implementations, the ethanol or other hydrocarbon fuel may additionally be utilized as a gas for maintaining gas journal bearings for any of the rotating components (turbocharger 104, power turbine 108, or compressor 106). As an example, bleed lines (not shown) may run from the vaporized working fluid line to gas bearing circuits (not shown) provided in one or more of the rotating components. The design and implementation of gas bearing circuits are generally known to persons skilled in the art. Some examples of gas bearings are described in above-referenced U.S. Pat. No. 6,392,313.
According to another implementation, a turbocharged locomotive-type heat engine is provided that is similar to that described above and illustrated in
According to another implementation, a turbocharged locomotive-type heat engine is provided that is similar to that described above and illustrated in
According to another implementation, a turbocharged locomotive-type heat engine is provided that is similar to that described above and illustrated in
One advantage provided by the heat engine 300 is that the power turbine 108 is not in fluid communication or direct structural contact with the turbocharger 104 or any other high-temperature components. That is, the power turbine 108 is thermally isolated from the high-temperature components and high-temperature fluid circuits. Thus, for example, in an implementation where generator magnets are housed in the same rotor as the power turbine 108 for generating electricity, the generator magnets will not experience the high temperatures experienced by the turbocharger 104 that drives the compressor 106. Thus, higher temperatures may be achieved without a detrimental effect on the generator magnets or other heat-sensitive components. Moreover, a shaft or other mechanical means is not required for transmitting power to the generator rotor from the hot working fluid or combustion gases. The heat engine 300 may also present advantages with system packaging.
Each of the heat engines described above provides the advantage that the ejector 112 will always cause a pressure drop across the power turbine 108, even when the turbocharger 104 or other rotating component is stopped or only slowly rotating. This ensures that the cycle will close and produce power even if the individual components have poor efficiency. Moreover, there is always a ready supply of secondary air or other type of gas for bearing pressurization and other such uses, even at zero speed. It will be noted that this advantage also applies to the heat engine 300 depicted in
Additionally, as with a steam locomotive each heat engine described above is self starting, requiring only that ignition occur in the combustion chamber and/or that vaporization occur in the boiler 110. The starting sequence does not require an electric motor to spin the rotors of the rotating components. Instead, in one example of a starting sequence, the boiler 110 is first heated such as by use of a resistive heating element. The resulting vapor produced by the boiler 110 then passes through the ejector 112 and motivates air flow through the combustor 102 and rotating components. By the operation of the ejector 112, the rotating components begin to function and the combustor 102 begins to operate normally as well. Initiation of fluid flow also initiates the operation of the injector 116.
Each of the heat engines described above features mechanical simplicity and a limited number of moving parts. Consequently, the above-described implementations are very attractive at small scales, where fabrication is always the most serious challenge. Generally, any suitable microfabrication techniques (e.g., MEMS, micromachining, etc.) may be utilized to fabricate the various components of the microengine. Various structural materials may be utilized and generally will be suitable for withstanding the pressures and temperatures associated with the operation of the microengine and compatible with microfabrication techniques. A few non-limiting examples of structural materials include metals (e.g., copper, stainless steel, silver, etc.), including transition metals such as zirconium and rhenium, silicon, oxides (e.g., silicon oxide, etc.), nitrides (e.g., silicon nitride, etc.), graphite, carbides (e.g., silicon carbide), ceramics (e.g., quartz, various glasses, etc.), etc.
For reference purposes,
In alternative implementations, the core section 406 and/or the flange section 408 may have a rectilinear shape or some other shape, and the boiler plates 404 may have a circular or cylindrical shape or some other shape. Accordingly, it will be understood that terms such as “length,” “width,” “diameter” and the like are utilized by way of example only and not as a limitation on the shape of a particular component or structural feature. Any component or structural feature may be considered in more general terms as having a characteristic dimension—i.e., a dominant dimension indicative of the size of the component or structural feature—which, depending on the shape may be appropriately termed a “length,” “width,” “diameter” or the like.
In operation, exhaust gas enters the transverse channel 502 from the inlet hole 606, passes through the transverse channel 502 along the curved flow path 610, exits the outlet hole 608, and flows through the outlet hole 608 of the next boiler plate 404. The exhaust gas continues to pass through the outlet holes 608 of additional boiler plates 404, eventually reaching an exhaust gas outlet 414 (or hot fluid hole,
An arrow 504 in
Referring to
Thus, in the present implementation the high-temperature boiler circuit and associated exhaust gas (hot fluid) flow path include a three-dimensional network of passages in which multiple turns may be taken. Specifically, the high-temperature boiler circuit and associated exhaust gas flow path run from the exhaust gas inlet (inlet hole 606 of the lowermost boiler plate 404) and through the exhaust gas inlet plenum 906 along the longitudinal direction A, through one or more of the multiple curved transverse channels 502 along the transverse plane B-C, and through the exhaust gas outlet plenum 506 and the exhaust gas outlet 414 along the longitudinal direction A. There is a net flow of exhaust gas from the exhaust gas inlet (inlet hole 606 of the lowermost boiler plate 404) to the exhaust gas outlet 414. In a typical implementation, the net direction of the exhaust gas flow is driven by a pressure differential across the high-temperature boiler circuit, but in other implementations may be additionally or alternatively due to pumping.
Referring to
In one non-limiting example, the overall height of the boiler 400 along the longitudinal axis A (e.g., from the bottom side 410 to the top side 412 ranges from 5 to 10 mm, and the maximum characteristic dimension of the boiler 400 in the transverse plane B-C (e.g., the diameter of the flange section 408) ranges from 20 to 40 mm. The thickness (in the longitudinal direction) of each boiler plate 404 is generally on the order of micrometers (i.e., ranges from 1 to 999 μm, or 0.001 to 0.999 mm) In one non-limiting example, the thickness of each boiler plate 404 may range from 0.1 to 0.8 mm.
In the implementation described above, the net axial flow of working fluid through the boiler chamber 520 is illustrated as being in the same direction as the net axial flow of exhaust gas through the exhaust gas inlet plenum 908 and outlet plenum 508, with the exhaust gas outlet 414 and the working fluid outlet 420 being on the same side of the boiler 400. It will be appreciated that the net flow of the working fluid through the boiler 400 may alternatively be counter to the net flow of exhaust gas through the boiler 400. This alternative may be realized, for example, by reversing the roles of the above-referenced “inlet” and “outlet” of either the high-temperature or low-temperature boiler circuit, such as by reversing the direction of fluid flow through either the high-temperature or low-temperature boiler circuit. Thus, in
It will also be appreciated that the terms “exhaust gas” and “working fluid” are used in the present context by way of example only. More generally, the boiler 400 is configured for flowing a “hot fluid” through the high-temperature boiler circuit and a “cold fluid” through the low-temperature boiler circuit. The hot fluid may be any fluid that is flowed through the boiler 400 at a temperature and pressure (relative to the temperature and pressure of a cold fluid that is simultaneously flowed through the boiler 400) sufficient for vaporizing or evaporating the cold fluid by heat transferring mechanisms enabled by the boiler structure. Accordingly, exhaust gas is one example of a hot fluid and working fluid is one example of a cold fluid.
In the present example, the uppermost plate is a lid or cover 1108 that includes a hot fluid outlet 1114. The hot fluid outlet 1114 is part of the high-temperature recuperator circuit and may, for example, correspond to the hot fluid recuperator outlet 170 or 218 shown in
The hot plates 1102 (and certain holes of the intervening cold plates 1104) collectively form a high-temperature recuperator circuit through the recuperator 1100. The cold plates 1104 (and certain holes of the intervening hot plates 1102) collectively form a low-temperature recuperator circuit through the recuperator 1100. Each hot plate 1102 provides a flow path for flowing a hot fluid, and each cold plate 1104 provides a flow path for flowing a cold fluid. The hot fluid may be any fluid that is flowed through the recuperator 1100 at a temperature and pressure (relative to the temperature and pressure of a cold fluid that is simultaneously flowed through the recuperator 1100) effective for transferring heat to the cold fluid by an amount and rate suitable for the heat exchanging function intended for the recuperator 1100 in an associated heat engine. Thus, for example, the hot fluid may be exhaust gas from a combustor or turbine or steam from a boiler, while the cold fluid may be air, fuel, or another type of working fluid. In a typical implementation, the structure of the hot plates 1102 (e.g., position of holes relative to transverse channels, described below) is different from the structure of the cold plates 1104.
Each hot plate 1102 also includes a curved transverse channel 1212 (or groove, recess, depression, etc.) formed into the thickness of the hot plate 1102 from the top side such that the transverse channel 1212 is in fluid communication with the hot fluid inlet hole 1206 and the hot fluid outlet hole 1208 and runs coaxially about the central hole 1204. Accordingly, the transverse channel 1212 may be characterized as being generally C-shaped or at least including a C-shaped section. When the hot plates 1102 and cold plates 1104 are stacked together in alternating series, the bottom side of a cold plate 1104 defines the upper boundary of the transverse channel 1212 and hot fluid inlet hole 1206 of the underlying hot plate 1102. The hot fluid inlet hole 1206 is oriented generally orthogonal to the central hole 1204 and provides an inlet for hot fluid from the central hole 1204 into the transverse channel 1212. Each transverse channel 1212 provides a curved flow path 1210 in the transverse plane B-C for hot fluid. Thus, the flow path 1210 through each transverse channel 1212 may be characterized as two-dimensional, multi-directional or circumferential in that it has a flow component along the first transverse axis B and a flow component along the second transverse axis C. The flow path 1210 may also be characterized as being generally spiral-shaped in that the hot fluid enters the transverse channel 1212 from the central hole 1204 via the hot fluid inlet hole 1206, runs radially outward and then follows a curved path to the hot fluid outlet hole 1208 located at a radial distance from the central hole 1204.
In operation, the hot fluid exiting the hot fluid outlet hole 1208 flows passes through a hot fluid outlet hole 1408 (
In operation, cold fluid enters the transverse channel 1412 from the cold fluid inlet hole 1416 and follows the curved flow path 1410 through the transverse channel 1412 to the cold fluid outlet hole 1418. Cold fluid exiting the cold fluid outlet hole 1418 passes through the cold fluid outlet hole 1218 (
Thus, in the present implementation the high-temperature recuperator circuit and associated hot fluid flow path include a three-dimensional network of passages in which multiple turns may be taken. Specifically, the high-temperature recuperator circuit and associated hot fluid flow path run from the hot fluid inlet (hot fluid inlet hole 1204 or 1404 of the lowermost hot plate 1102 or cold plate 1104) and through the hot fluid inlet plenum 1606 along the longitudinal direction A, through one or more of the multiple curved transverse channels 1212 along the transverse plane B-C, and through the hot fluid outlet plenum 1706 and the hot fluid outlet 1114 (or, alternatively, the hot fluid outlet hole 1208 or 1408 of the uppermost hot plate 1102 or cold plate 1104 if the lid 1108 is not provided) along the longitudinal direction A. There is a net flow of hot fluid from the hot fluid inlet to the hot fluid outlet 1114 of the recuperator 1100. In a typical implementation, the net direction of the hot fluid flow is driven by a pressure differential across the high-temperature recuperator circuit, but in other implementations may be additionally or alternatively due to pumping.
Referring back to
Thus, like the high-temperature recuperator circuit, in the present implementation the low-temperature recuperator circuit and associated cold fluid flow path include a three-dimensional network of passages in which multiple turns may be taken. Specifically, the low-temperature recuperator circuit and associated cold fluid flow path run from the cold fluid inlet (cold fluid inlet hole 1216 or 1416 of the lowermost hot plate 1102 or cold plate 1104) and through the cold fluid inlet plenum 1806 along the longitudinal direction A, through one or more of the multiple curved transverse channels 1412 along the transverse plane B-C, and through the cold fluid outlet plenum 1716 and the cold fluid outlet along the longitudinal direction A. As noted above, the cold fluid outlet may be the cold fluid outlet hole 1218 or 1418 of the lowermost hot plate 1102 or cold plate 1104 if a lid is not provided. There is a net flow of cold fluid from the cold fluid inlet to the cold fluid outlet of the recuperator 1100. In a typical implementation, the net direction of the cold fluid flow is driven by a pressure differential across the low-temperature recuperator circuit, but in other implementations may be additionally or alternatively due to pumping.
In one non-limiting example, the overall height of the recuperator 1100 along the longitudinal axis A (e.g., from the bottom side 1110 to the top side 1112 ranges from 20 to 25 mm, and the maximum characteristic dimension (e.g., length or width) of the recuperator 1100 in the transverse plane B-C ranges from 20 to 25 mm. The thickness (in the longitudinal direction) of each hot plate 1102 and/or cold plate 1104 is generally on the order of micrometers (i.e., ranges from 1 to 999 μm, or 0.001 to 0.999 mm). In one non-limiting example, the thickness of each hot plate 1102 and/or cold plate 1104 may range from 0.05 to 0.25 mm.
In the implementation described above, the net axial flow of cold fluid through the cold fluid inlet plenum 1806 is illustrated as being in the opposite direction as the net axial flow of cold fluid through the cold fluid outlet plenum 1716, with the cold fluid inlet and the cold fluid outlet being on the same side of the recuperator 1100. It will be appreciated that the net flow of the cold fluid through the cold fluid inlet plenum 1806 may alternatively be in the same direction as the net flow of cold fluid through the cold fluid outlet plenum 1716. This alternative may be realized, for example, by appropriately relocating the cold fluid inlet and cold fluid outlet to opposite sides of the recuperator 1100 and modifying any upper or lower lids provided. Thus, in
Heat exchangers such as described by example above (boiler 400 and recuperator 1100) are well-suited for micro-scale implementation. These heat exchangers are configured so as to allow a designer to control the dimensions of the plenums or headers and to control the length-to-diameter (or hydraulic diameter) ratio (or aspect ratio) of the transverse channels 1212, 1412. These heat exchangers thus allow the designer to package the required dimensions and length-to-diameter ratio within a given volume constraint. For example, if the heat exchanger (or its associated engine or system) is specified to have a maximum external diameter and length, the designer may control the length of the circumferential flow paths by adjustment of the dimensions of the associated plenums. Moreover, by controlling the length-to-diameter ratio and the quantity of the transverse channels 1212, 1412, the designer can allow the flow of fluid via the inlet plenums into any tier of the heat exchanger stack.
In the present implementation, the diffuser 2130 includes a converging section 2132 followed by a diverging section 2134. The nozzle 2122 includes a nozzle bore 2138 that may also include a converging section and a diverging section (not shown). In operation the vaporized working fluid flows as a jet through the centerline of the ejector 2110, serving as the high-velocity primary flow (or motive flow) through the ejector 2110. The exhaust gas introduced into the inlet plenum 2126 flows radially inward toward the flow of vaporized working fluid, serving as a quiescent or low-velocity flow. The motive jet of vaporized working fluid entrains the surrounding exhaust gas by viscous interaction and exchanges momentum with the exhaust gas. Mixing of the two fluids proceeds in the converging section 2132 of the diffuser 2130, and the resulting mixed fluid flow expands in the diverging section 2134.
In general, terms such as “communicate” and “in . . . communication with” (for example, a first component “communicates with” or “is in communication with” a second component) are used herein to indicate a structural, functional, mechanical, electrical, signal, optical, magnetic, electromagnetic, ionic or fluidic relationship between two or more components or elements. As such, the fact that one component is said to communicate with a second component is not intended to exclude the possibility that additional components may be present between, and/or operatively associated or engaged with, the first and second components.
For purposes of the present disclosure, it will be understood that when a layer (or film, region, substrate, component, device, or the like) is referred to as being “on” or “over” another layer, that layer may be directly or actually on (or over) the other layer or, alternatively, intervening layers (e.g., buffer layers, transition layers, interlayers, sacrificial layers, etch-stop layers, masks, electrodes, interconnects, contacts, or the like) may also be present. A layer that is “directly on” another layer means that no intervening layer is present, unless otherwise indicated. It will also be understood that when a layer is referred to as being “on” (or “over”) another layer, that layer may cover the entire surface of the other layer or only a portion of the other layer. It will be further understood that terms such as “formed on” or “disposed on” are not intended to introduce any limitations relating to particular methods of material transport, deposition, fabrication, surface treatment, or physical, chemical, or ionic bonding or interaction. The term “interposed” is interpreted in a similar manner.
It will be understood that various aspects or details of the invention may be changed without departing from the scope of the invention. Furthermore, the foregoing description is for the purpose of illustration only, and not for the purpose of limitation—the invention being defined by the claims.
Claims
1. A heat engine, comprising:
- a combustor comprising a fuel inlet, an air inlet and an exhaust outlet;
- a power turbine communicating with the exhaust outlet, wherein the power turbine is driven to rotate by exhaust gas from the combustor;
- a boiler comprising a high-temperature boiler circuit in thermal contact with a low-temperature boiler circuit for transferring heat thereto, the high-temperature boiler circuit communicating with the power turbine for receiving exhaust gas therefrom;
- an ejector comprising a first ejector inlet communicating with the low-temperature boiler circuit for receiving a flow of vaporized working fluid therefrom, a second ejector inlet communicating with the high-temperature boiler circuit for receiving exhaust gas therefrom, and an ejector outlet, wherein the ejector is configured for entraining the exhaust gas from the second ejector inlet in the flow of vaporized working fluid from the first ejector inlet and increasing a pressure drop across the power turbine;
- a condenser comprising a high-temperature condenser circuit in thermal contact with a low-temperature condenser circuit for transferring heat thereto, the high-temperature condenser circuit communicating with the ejector outlet, wherein the low-temperature condenser circuit is configured for flowing a cold fluid through the condenser; and
- an injector comprising an injector liquid inlet communicating with the high-temperature condenser circuit for receiving condensed working fluid therefrom, and an injector outlet communicating with the low-temperature boiler circuit, wherein the injector is configured for flowing liquid-phase working fluid to the boiler.
2. The heat engine of claim 1, wherein the injector comprises an injector gas inlet communicating with the low-temperature boiler circuit for receiving a flow of vaporized working fluid therefrom, and the injector is configured for entraining condensed working fluid from the injector liquid inlet in the flow of vaporized working fluid from the injector gas inlet.
3. The heat engine of claim 1, comprising a tank interposed between the hot fluid condenser outlet and the injector liquid inlet, the tank comprising a liquid/gas separator wherein the tank is configured for separating uncondensed components from condensed working fluid received from the condenser and feeding the condensed working fluid to the injector.
4. The heat engine of claim 1, wherein the low-temperature boiler circuit communicates with the fuel inlet for feeding vaporized working fluid as a fuel to the combustor,
5. The heat engine of claim 1, comprising a recuperator comprising a high-temperature recuperator circuit in thermal contact with a low-temperature recuperator circuit for transferring heat thereto, the high-temperature recuperator circuit interposed between the power turbine and the high-temperature boiler circuit, and the low-temperature recuperator circuit disposed in upstream fluid communication with the air inlet, wherein the recuperator is configured for pre-heating air fed to the combustor.
6. The heat engine of claim 1, comprising a recuperator comprising a high-temperature recuperator circuit in thermal contact with a low-temperature recuperator circuit for transferring heat thereto, the high-temperature recuperator circuit interposed between the ejector outlet and the high-temperature condenser circuit, and the low-temperature recuperator circuit interposed between the injector outlet and the low-temperature boiler circuit, wherein the recuperator is configured for pre-heating the working fluid fed to the boiler.
7. The heat engine of claim 1, comprising:
- a first recuperator comprising a high-temperature first recuperator circuit in thermal contact with a low-temperature first recuperator circuit for transferring heat thereto, the high-temperature first recuperator circuit interposed between the power turbine and the high-temperature boiler circuit, and the low-temperature recuperator circuit disposed in upstream fluid communication with the air inlet, wherein the first recuperator is configured for pre-heating the compressed air fed to the combustor; and
- a second recuperator comprising a high-temperature second recuperator circuit in thermal contact with a low-temperature second recuperator circuit for transferring heat thereto, the high-temperature second recuperator circuit interposed between the ejector outlet and the high-temperature condenser circuit, and the low-temperature second recuperator circuit interposed between the injector outlet and the low-temperature boiler circuit, wherein the second recuperator is configured for pre-heating the working fluid fed to the boiler.
8. The heat engine of claim 1, comprising:
- a turbocharger rotatable about a spool and communicating with the exhaust outlet, wherein the turbocharger is driven to rotate by exhaust gas from the combustor, and the power turbine comprises a turbine inlet communicating with the turbocharger and is driven to rotate by exhaust gas from the turbocharger; and
- a compressor rotatable about the spool wherein the compressor is driven to rotate by the turbocharger, the compressor comprising a compressor inlet for aspirating ambient air, and a compressor outlet communicating with the air inlet wherein the compressor feeds compressed air to the combustor.
9. A heat engine, comprising:
- a combustor comprising a fuel inlet, an air inlet and an exhaust outlet;
- a turbocharger rotatable about a spool and communicating with the air inlet wherein the turbocharger feeds air to the combustor;
- a compressor rotatable about the spool wherein the compressor is driven to rotate by the turbocharger, the compressor comprising a compressor inlet for aspirating ambient air;
- a power turbine communicating with the compressor wherein the power turbine is driven to rotate by compressed air from the compressor;
- a recuperator comprising a high-temperature recuperator circuit in thermal contact with a low-temperature recuperator circuit for transferring heat thereto, the high-temperature recuperator circuit communicating with the exhaust outlet, and the low-temperature recuperator circuit interposed between the power turbine and the turbocharger, wherein the turbocharger is driven to rotate by heated air from the recuperator;
- a boiler comprising a high-temperature boiler circuit in thermal contact with a low-temperature boiler circuit for transferring heat thereto, the high-temperature boiler circuit communicating with the high-temperature recuperator circuit for receiving exhaust gas therefrom;
- an ejector comprising a first ejector inlet communicating with the low-temperature boiler circuit for receiving a flow of vaporized working fluid therefrom, a second ejector inlet communicating with the high-temperature boiler circuit for receiving exhaust gas therefrom, and an ejector outlet, wherein the ejector is configured for entraining the exhaust gas from the second ejector inlet in the flow of vaporized working fluid from the first ejector inlet and increasing a pressure drop across the power turbine;
- a condenser comprising a high-temperature condenser circuit in thermal contact with a low-temperature condenser circuit for transferring heat thereto, the high-temperature condenser circuit communicating with the ejector outlet, wherein the low-temperature condenser circuit is configured for flowing a cold fluid through the condenser; and
- an injector comprising an injector liquid inlet communicating with the high-temperature condenser circuit for receiving condensed working fluid therefrom, and an injector outlet communicating with the low-temperature boiler circuit, wherein the injector is configured for flowing liquid-phase working fluid to the boiler.
10. The heat engine of claim 9, wherein the injector comprises an injector gas inlet communicating with the low-temperature boiler circuit for receiving a flow of vaporized working fluid therefrom, and the injector is configured for entraining condensed working fluid from the injector liquid inlet in the flow of vaporized working fluid from the injector gas inlet.
11. The heat engine of claim 10, comprising a tank interposed between the hot fluid condenser outlet and the injector liquid inlet, the tank comprising a liquid/gas separator wherein the tank is configured for separating uncondensed components from condensed working fluid received from the condenser and feeding the condensed working fluid to the injector.
12. The heat engine of claim 9, wherein the low-temperature boiler circuit communicates with the fuel inlet for feeding vaporized working fluid as a fuel to the combustor.
13. The heat engine of claim 9, wherein the recuperator communicating with the turbocharger is a first recuperator, and further comprising a second recuperator, the second recuperator comprising a high-temperature second recuperator circuit in thermal contact with a low-temperature second recuperator circuit for transferring heat thereto, the high-temperature second recuperator circuit interposed between the ejector outlet and the high-temperature condenser circuit, and the low-temperature second recuperator circuit interposed between the injector outlet and the low-temperature boiler circuit, wherein the second recuperator is configured for pre-heating the working fluid fed to the boiler.
14. A method for generating power, the method comprising:
- flowing an exhaust gas comprising combustion products from a power turbine to a boiler;
- vaporizing a working fluid by flowing the working fluid through the boiler while flowing the exhaust gas through the boiler, wherein heat is transferred from the exhaust gas to the working fluid;
- flowing the vaporized working fluid through an ejector;
- entraining the exhaust gas in the vaporized working fluid as the vaporized working fluid flows through the ejector by flowing the exhaust gas from the boiler into the ejector, wherein entrainment of the exhaust gas creates suction downstream of the power turbine;
- condensing the working fluid discharged from the ejector and returning the condensed working fluid to the boiler for vaporization by the exhaust gas flowing through the boiler; and
- driving the power turbine to rotate by flowing the exhaust gas to the turbine from a combustor disposed upstream of the power turbine, and by creating the suction in the exhaust gas downstream of the power turbine.
15. The method of claim 14, comprising flowing the exhaust gas from the power turbine through a recuperator before flowing the exhaust gas to the boiler, and flowing air through the recuperator wherein heat is transferred from the exhaust gas to the air, and feeding the heated air to the combustor for combustion with a fuel.
16. The method of claim 14, comprising flowing the working fluid from the ejector through a recuperator before condensing the working fluid, and flowing the condensed working fluid through the recuperator before returning the condensed working fluid to the boiler, wherein the recuperator transfers heat from the working fluid discharged from the ejector to the condensed working fluid flowing through the recuperator, and the heated condensed working fluid is flowed to the boiler for vaporization.
17. The method of claim 14, comprising:
- flowing the exhaust gas from the power turbine through a first recuperator before flowing the exhaust gas to the boiler, and flowing air through the first recuperator wherein heat is transferred from the exhaust gas to the air, and feeding the heated air to the combustor for combustion with a fuel; and
- flowing the working fluid from the ejector through a second recuperator before condensing the working fluid, and flowing the condensed working fluid through the second recuperator before returning the condensed working fluid to the boiler, wherein the second recuperator transfers heat from the working fluid discharged from the ejector to the condensed working fluid flowing through the second recuperator, and the heated condensed working fluid is flowed to the boiler for vaporization.
18. The method of claim 14, wherein a turbocharger is interposed between the combustor and the power turbine and a compressor is rotatable on a common spool with the turbocharger, and comprising driving the turbocharger and the compressor to rotate by flowing the exhaust gas from the combustor to the turbocharger, wherein the power turbine is driven by exhaust gas discharged from the turbocharger, and feeding compressed air from the compressor to the combustor for combustion with a fuel.
19. The method of claim 14, wherein returning the condensed working fluid to the boiler comprises flowing vaporized working fluid from the boiler through an injector, entraining the condensed working fluid in the vaporized working fluid as the vaporized working fluid flows through the injector by flowing the condensed working fluid into the injector, and flowing the condensed working fluid from the injector into the boiler.
20. The method of claim 14, wherein the working fluid is a hydrocarbon fuel.
21. The method of claim 20, comprising flowing vaporized working fluid from the boiler to the combustor to supply the combustor with fuel for combustion with air.
22. A method for generating power, comprising:
- flowing an exhaust gas comprising combustion products from a combustor to a recuperator;
- while flowing the exhaust gas through the recuperator, flowing air discharged from a power turbine through the recuperator wherein heat is transferred from the exhaust gas to the air;
- flowing the exhaust gas from the recuperator to a boiler;
- vaporizing a working fluid by flowing the working fluid through the boiler while flowing the exhaust gas through the boiler, wherein heat is transferred from the exhaust gas to the working fluid;
- flowing the vaporized working fluid through an ejector;
- entraining the exhaust gas in the vaporized working fluid as the vaporized working fluid flows through the ejector by flowing the exhaust gas from the boiler into the ejector, wherein entrainment of the exhaust gas creates suction downstream of the power turbine;
- condensing the working fluid discharged from the ejector and returning the condensed working fluid to the boiler for vaporization by the exhaust gas flowing through the boiler; and
- driving a turbocharger and a compressor to rotate by flowing the heated air from the recuperator to the turbocharger, wherein the compressor rotates on a common spool with the turbocharger;
- driving the power turbine to rotate by flowing compressed air from the compressor to the power turbine.
23. The method of claim 22, wherein the recuperator to which exhaust gas is flowed from the combustor is a first recuperator, and comprising flowing the working fluid from the ejector through a second recuperator before condensing the working fluid, and flowing the condensed working fluid through the second recuperator before returning the condensed working fluid to the boiler, wherein the second recuperator transfers heat from the working fluid discharged from the ejector to the condensed working fluid flowing through the second recuperator, and the heated condensed working fluid is flowed to the boiler for vaporization.
24. The method of claim 22, wherein returning the condensed working fluid to the boiler comprises flowing vaporized working fluid from the boiler through an injector, entraining the condensed working fluid in the vaporized working fluid as the vaporized working fluid flows through the injector by flowing the condensed working fluid into the injector, and flowing the condensed working fluid from the injector into the boiler.
25. The method of claim 22, wherein the working fluid is a hydrocarbon fuel.
26. The method of claim 25, comprising flowing vaporized working fluid from the boiler to the combustor to supply the combustor with fuel for combustion with air.
27. A heat exchanger, comprising:
- a plurality of hot fluid plates stacked in series along a longitudinal direction, each hot fluid plate having a thickness in the longitudinal direction and a planar area in a transverse plane orthogonal to the longitudinal direction, and each hot fluid plate comprising a central hole, a hot fluid inlet hole and a hot fluid outlet hole formed through the thickness, the hot fluid inlet hole and the hot fluid outlet hole located at respective radial distances from the central hole, and each hot fluid plate further comprising a transverse channel running in the transverse plane from the hot fluid inlet hole, around the central hole and to the hot fluid outlet hole; and
- a cold fluid circuit running from a cold fluid inlet to a cold fluid outlet in thermal contact with the transverse channels, wherein:
- the central holes are aligned with each other along the longitudinal direction;
- the hot fluid inlet holes are aligned with each other along the longitudinal direction, forming a hot fluid inlet plenum;
- the hot fluid outlet holes are aligned with each other along the longitudinal direction, forming a hot fluid outlet plenum; and
- the transverse channels establish a plurality of transverse flow paths from the hot fluid inlet plenum to the hot fluid outlet plenum.
28. The heat exchanger of claim 27, wherein the hot fluid plates each have a thickness on the order of micrometers.
29. The heat exchanger of claim 27, wherein the cold fluid circuit comprises a cold fluid plenum extending along the longitudinal direction and surrounded by the central holes.
30. The heat exchanger of claim 27, comprising a lid disposed on an outermost one of the hot fluid plates, the lid comprising a hot fluid hole communicating with the hot fluid inlet or the hot fluid outlet of the outermost hot fluid plate, and a cold fluid hole communicating with the cold fluid circuit to define the cold fluid inlet or the cold fluid outlet.
31. The heat exchanger of claim 27, comprising a lid disposed on an outermost one of the hot fluid plates, the lid comprising a hot fluid hole communicating with the hot fluid inlet or the hot fluid outlet of the outermost hot fluid plate, wherein the cold fluid outlet is a central cold fluid outlet formed through the lid, and the lid further comprising a radial channel communicating with the central cold fluid outlet and an outer cold fluid outlet communicating with the radial channel at a distance from the central cold fluid outlet.
32. The heat exchanger of claim 27, comprising a body comprising a lid disposed on an outermost one of the hot fluid plates and a cold fluid plenum extending from the lid along the longitudinal direction and surrounded by the central holes, the lid comprising a hot fluid hole communicating with the hot fluid inlet or the hot fluid outlet of the outermost hot fluid plate, wherein the cold fluid plenum is part of the cold fluid circuit.
33. The heat exchanger of claim 27, wherein each transverse channel comprises a C-shaped section.
34. A heat exchanger, comprising:
- a plurality of hot fluid plates each having a thickness in a longitudinal direction and a planar area in a transverse plane orthogonal to the longitudinal direction, each hot fluid plate comprising a central hole, a hot fluid outlet hole, a cold fluid inlet hole and a cold fluid outlet hole formed through the thickness, the hot fluid outlet hole, the cold fluid inlet hole and the cold fluid outlet hole located at respective radial distances from the central hole, and each hot fluid plate further comprising a hot fluid transverse channel running in the transverse plane from the central hole and radially outward therefrom, around the central hole and to the hot fluid outlet hole; and
- a plurality of cold fluid plates each having a thickness in the longitudinal direction and a planar area in the transverse plane, each cold fluid plate comprising a central hole, a hot fluid outlet hole, a cold fluid inlet hole and a cold fluid outlet hole formed through the thickness, and each cold fluid plate further comprising a cold fluid transverse channel running in the transverse plane from the cold fluid inlet hole, around the central hole and to the cold fluid outlet hole, wherein:
- the hot fluid plates and the cold fluid plates are stacked along the longitudinal direction in alternating series with each other such that each hot fluid plate is adjacent to at least one of the cold fluid plates and each hot fluid transverse channel is in thermal contact with at least one of the cold fluid transverse channels;
- the central holes of the hot fluid plates and the cold fluid plates are aligned with each other along the longitudinal direction, forming a hot fluid inlet plenum;
- the hot fluid outlet holes of the hot fluid plates and the cold fluid plates are aligned with each other along the longitudinal direction, forming a hot fluid outlet plenum;
- the cold fluid inlet holes of the hot fluid plates and the cold fluid plates are aligned with each other along the longitudinal direction, forming a cold fluid inlet plenum;
- the cold fluid outlet holes of the hot fluid plates and the cold fluid plates are aligned with each other along the longitudinal direction, forming a cold fluid outlet plenum;
- the hot fluid transverse channels establish a plurality of transverse flow paths from the hot fluid inlet plenum to the hot fluid outlet plenum; and
- the cold fluid transverse channels establish a plurality of transverse flow paths from the cold fluid inlet plenum to the cold fluid outlet plenum.
35. The heat exchanger of claim 34, wherein the hot fluid plates and the cold fluid plates each have a thickness on the order of micrometers.
36. The heat exchanger of claim 34, wherein the hot fluid transverse channels and the cold fluid transverse channels each comprise a C-shaped section.
37. The heat exchanger of claim 34, wherein:
- the alternating series of hot fluid plates and cold fluid plates form a series of hot fluid inlet holes axially spaced along the longitudinal direction, each hot fluid inlet hole bounded by a corresponding one of the hot fluid transverse channels and an adjacent one of the cold fluid plates, and each hot fluid inlet hole defining a transverse flow path from the hot fluid inlet plenum into the hot fluid transverse channel; and
- further comprising a cylindrical structure surrounded by the central holes of the hot fluid plates and the cold fluid plates, the cylindrical structure comprising an elongated opening extending in the longitudinal direction and communicating with the hot fluid inlet holes.
38. The heat exchanger of claim 37, wherein the cylindrical structure is a combustor housing, and the hot fluid inlet plenum is bounded by the elongated opening and defines a gas flow path from an interior of the cylindrical structure to the hot fluid inlet holes.
Type: Application
Filed: Dec 29, 2010
Publication Date: Jun 30, 2011
Inventors: Jonathan M. Protz (Durham, NC), William G. Gardner (Durham, NC), Justin W. Jaworski (Tampa, FL), Andrew P. Camacho (Miami, FL), Hardy S. Shen (Durham, NC), David J. Fields (Burke, VA), Stefan Oliver Pelekies
Application Number: 12/980,740
International Classification: F01K 19/08 (20060101); F01K 25/00 (20060101); F28D 15/00 (20060101);