TECHNICAL FIELD [0001] The present disclosure relates to internal combustion engines.

BACKGROUND

[0002] Waste heat is energy produced by some useful device and carried by a byproduct or otherwise discarded or unused medium. In operation, significant amounts of energy produced from engines are lost in the form of waste heat, for example as exhaust gas heat. Some waste heat recovery systems convert exhaust heat energy into usable shaft work through an Organic Rankine Cycle ("ORC"). An ORC is similar to a steam cycle, except that the working fluid is an organic fluid (i.e., instead of water). Typical working fluids for ORC include fiuorinated carbons (referred to as refrigerants) and hydrocarbons (e.g., n-pentane). Using extracted waste heat energy, working fluids can be used to drive expansion machines (e.g., turbo-expanders, piston expanders, scrolls, etc.) to generate a mechanical force, thereby recapturing energy that would have otherwise been lost.

[0003] One challenge in using an expander is that the working fluid environment is not completely sealed from other aspects of a given ORC system. As such, working fluid may leak through the expander and into other associated components. For example, working fluid may "blow by" the expander and into an associated transmission, contaminating lubricants therein. When the working fluid is a solvent like toluene, the working fluid causes the lubricant to become progressively thinner, eventually losing its lubricating properties. As another example, the lubricant may also work its way through the expander and thereby contaminate the working fluid.

SUMMARY

[0004] One embodiment relates to a waste heat recovery system. The system includes a source of waste heat energy, a working fluid circuit, and a lubrication circuit. The working fluid circuit includes a boiler containing a working fluid in heat receiving communication with the source of waste heat energy. The working fluid circuit further includes a conversion assembly in working fluid receiving communication with the boiler and in rotational force providing communication with a device, wherein the working fluid is received from the boiler in a gaseous state. The lubrication circuit includes at least one moving part of the conversion assembly. The lubrication circuit further includes a lubricant reservoir containing at least one of a perfluoro polyether lubricant and a fluorosilicone lubricant, the lubricant reservoir in lubricant receiving communication with the at least one moving part of the conversion assembly.

[0005] Another embodiment also relates to a waste heat recovery system. The system includes an engine generating an exhaust gas, an exhaust system, a working fluid circuit, and a lubrication circuit. The exhaust system is coupled to the engine and routes exhaust gas from the engine to the atmosphere. The working fluid circuit includes a boiler coupled to the exhaust system, the boiler containing a working fluid in heat receiving communication with the exhaust gas. The working fluid circuit further includes a conversion assembly in working fluid receiving communication with the boiler and in rotational force providing communication with at least one of the engine and a device other than the engine, wherein the working fluid is received from the boiler in a gaseous state. The lubrication circuit includes at least one moving part of the conversion assembly. The lubrication circuit further includes a lubricant reservoir containing at least one of a perfluoro polyether lubricant and a fluorosilicone lubricant, the lubricant reservoir in lubricant receiving communication with the at least one moving part of the conversion assembly.

[0006] Yet another embodiment relates to a method of manufacturing a waste heat recovery system. The method includes coupling a conversion assembly to a device. The method further includes coupling a boiler to a source of waste heat energy, wherein the boiler is in heat receiving communication with the source of waste heat energy. The method includes assembling a working fluid circuit comprising the conversion assembly and the boiler. The method further includes assembling a lubrication circuit comprising a lubricant reservoir in fluid receiving communication with the conversion assembly and a lubricant pump in fluid providing communication with the conversion assembly. The method includes filling the working fluid circuit with a working fluid. The method further includes filling the lubrication circuit with at least one of a perfluoro polyether lubricant and a fluorosilicone lubricant. The method includes operating the internal combustion engine. [0007] It should be appreciated that all combinations of the foregoing concept and additional concepts discussed in greater detail below (provided such concepts are not mutually inconsistent) are contemplated as being part of the inventive subject matter disclosed herein. In particular, all combinations of claimed subject matter appearing at the end of this disclosure are contemplated as being part of the inventive subject matter disclosed herein.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] The skilled artisan will understand that the drawings primarily are for illustrative purposes and are not intended to limit the scope of the subject matter described herein. The drawings are not necessarily to scale; in some instances, various aspects of the subject matter disclosed herein may be shown exaggerated or enlarged in the drawings to facilitate an understanding of different features. In the drawings, like reference characters generally refer to like features (e.g., functionally similar and/or structurally similar elements).

[0009] FIG. 1 is a schematic block diagram illustrating a working fluid circuit, according to an example embodiment.

[0010] FIG. 2 is a schematic block diagram illustrating a lubrication circuit, according to an example embodiment.

[0011] FIG. 3 is a block flow diagram illustrating a method of recovering waste heat, according to an example embodiment.

The features and advantages of the inventive concepts disclosed herein will become more apparent from the detailed description set forth below when taken in conjunction with the drawings.

DETAILED DESCRIPTION

[0012] Following below are more detailed descriptions of various concepts related to, and embodiments of, recovering waste heat from internal combustion engines. It should be appreciated that various concepts introduced above and discussed in greater detail below may be implemented in any of numerous ways, as the disclosed concepts are not limited to any particular manner of implementation. Examples of specific implementations and applications are provided primarily for illustrative purposes.

[0013] Referring now to FIG. 1, an ORC system 100 includes a working fluid circuit configured to recover waste heat resulting from the operation of a waste heat source (e.g., an internal combustion engine). The system 100 includes an internal combustion engine 102 serving as a waste heat source, a boiler 106, a conversion assembly 108, a condenser 114, and a working fluid pump 116. The engine 102 is a powerplant configured to cyclically collect and ignite volumes of air and fuel to generate a mechanical force. As a result of each ignition cycle, an exhaust gas 104 and heat are produced as a byproduct. Heated exhaust gas is commonly routed through an accompanying exhaust aftertreatment system and out to the atmosphere. In some arrangements, the system 100 includes an exhaust gas recirculation system ("EGR") 105 (including one or more conduits, etc.), which redirects a portion of the exhaust gas 104 back to the engine 102 (i.e., instead of the atmosphere). As such, for example, the EGR 105 may provide exhaust gas 104 back to the engine 102 where intake gas volumes are reduced (e.g., where an associated throttle reduces an intake gas flow, or is closed altogether) and/or to reduce regulated emissions. As one of skill in the art would recognize, other sources of waste heat may be used in lieu of the internal combustion engine 102.

[0014] The exhaust gas 104 is routed through or adjacent to the boiler 106, sufficient to allow heat energy of the exhaust gas 104 to pass to a working fluid in a liquid state disposed in the boiler 106. Working fluid is the primary energy exchange medium in the system 100, allowing waste heat to be converted to a mechanical force to supplement the operation of the engine 102. Working fluid may be selected for having a low boiling point and/or vapor pressure, thereby allowing for changes in states of matter throughout the course of operation of the system 100. For example, a working fluid may be selected such that heat provided by the exhaust gas 104 is sufficient to convert the working fluid from a liquid to a gas (e.g., gaseous working fluid or dry vapor). As such, when exhaust gas 104 passes by or through the boiler 106, the working fluid in liquid state is converted to a gaseous state. In some arrangements, the exhaust gas 104 superheats working fluid in a liquid state to convert the working fluid into a dry vapor. Common embodiments of the working fluid include fluorinated carbons (i.e., refrigerants) and hydrocarbons (e.g., n-pentane). In some arrangements, the working fluid is toluene.

[0015] One or more conduits and/or chambers routes working fluid dry vapor from the boiler 106 to the conversion assembly 108. The conversion assembly 108 is a device configured to translate a fluid flow into a rotational force. In some arrangements, the conversion assembly includes an expander 110 and a transmission 112. The expander 110, in some arrangements, is a high speed turbomachine, converting the flow of working fluid in a dry vapor state into mechanical work. In other arrangements, the expander 110 is a piston- based expander. In yet other arrangements, the expander 110 is a scroll-based expander. For example, the expander 110 may include one or more turbines configured to receive a passage of a flow of working fluid dry vapor, and correspondingly rotate an associated turbine shaft. The turbine shaft may be communicatively engaged to the transmission 112, which may in turn be communicatively engaged to the engine 102. The transmission 112 is configured to convert a high-speed rotational input from the turbine shaft to a comparatively lower speed output (e.g., a few hundred or a few thousand RPMs) that may be usable by the engine 102 or some other useful device (e.g., a pump, a generator, a secondary engine, fans, etc.). In some arrangements, the transmission 112 includes a planetary gearset. The transmission 112 mechanically communicates the output to the engine 102.

[0016] One or more conduits and/or chambers route working fluid dry vapor from the expander 110 to the condenser 114. The condenser 114 is configured to return the working fluid dry vapor to a liquid state. In some arrangements, the condenser 114 cools the working fluid dry vapor (e.g., allowing heat carried in the working fluid dry vapor to pass to the atmosphere, for example through a network of working fluid dry vapor conduits exposed to an airflow from the atmosphere) sufficient to cause the working fluid dry vapor to return to a liquid state.

[0017] In some arrangements, the ORC system 100 includes a recuperation circuit. The recuperation circuit includes a heat exchanger 118. The heat exchanger 118 includes one or more conduits, chambers, or other fluid-carrying vessels configured to transfer residual heat from vaporous working fluid from the expander 110 to working fluid in a liquid state traveling to the boiler 106. As such, the heat exchanger 118 is in fluid receiving communication with the expander 110 and in fluid providing communication with the condenser 114. In turn, the heat exchanger 118 is further in heat providing communication with one or more conduits coupling the working fluid pump 116 to the boiler 106. In operation, vaporous working fluid travels from the expander 110 to the exchanger 118. In the exchanger 118, at least some of the heat of the vaporous working fluid is passed to working fluid in a liquid state flowing from the working fluid pump 116. The working fluid— which may or may not be in a vapor state after passing through the exchanger 118— then flows to the condenser 114, where it is returned to a liquid state.

[0018] One or more conduits and/or chambers route working fluid in a liquid state from the condenser 114 to the working fluid pump 116. The working fluid pump 116 draws working fluid in a liquid state from the condenser 114 and provides the working fluid to the boiler 106. As such, the working fluid completes a full loop of the working fluid circuit, thereby capturing heat in the exhaust gas 104 produced by the engine 102, and converting it into a supplemental mechanical force.

[0019] Referring now to FIG. 2, a lubricating system 200 includes a lubrication circuit configured to reduce frictional effects and parasitic losses resulting from the operation of the system 100. The lubricating system 200 includes bearings 202 and the transmission 112 at the conversion assembly 108, along with a lubricant reservoir 204 and a lubricant pump 206. The bearings 202 are configured to facilitate the operation of the expander 110 (e.g., facilitating the rotation of an associated turbine shaft). In some arrangements, the bearings 202 are angular contact ball bearings associated with a rotating aspect of the expander 110. One or more bearings may be disposed at the transmission 112 as well, which may comprise one or more rotating gears or gearsets. In some arrangements, the transmission 1 12 houses a planetary gearset.

[0020] The bearings 202 and the transmission 112 are in fluid providing communication with the reservoir 204, where a lubricating medium is collected. The lubricating medium includes at least one of perfluoro poly ether (PFPE) and fluorosilicone lubricants. PFPEs are similar to hydrocarbon oils; however instead of a Carbon-Hydrogen-Oxygen molecule, the hydrogen atom is replaced by a Fluorine atom (i.e., includes C-F-0 molecules). Similarly, fluorosilicone oil (e.g., Dow Corning DS-1265) is constituted from fluorine and silicon atoms instead of carbon and hydrogen, (i.e., includes Si-F-0 molecules).

[0021] PFPE oils are colorless and odorless fluids that are chemically inert and have high thermal stability. PFPE oils are insoluble in most solvents including toluene, but are soluble in f uorinated solvents such as trichlorotrifluoroethane and supercritical C0 ₂ . PFPE oils have a very low vapor pressure characteristic, which is ideal in a toluene-based ORC system as PFPE oils condense at very low pressures (e.g., when the system 100 is at idle, the system pressure may only be 0.2 bar). The low volatility of PFPE oils mean that outgassing cannot occur under such low pressure conditions. Also, PFPEs tend to be chemically inert, even when exposed to acids and solvents.

[0022] Fluorosilicone oils combine the properties of fluorinated polymers and silicone oils. Fluorosilicone oils have good chemical inertness to a wide variety of harsh, corrosive chemicals. They are very similar to PFPEs in terms of oxidative and inert properties and insolubility in many solvents. However, fluorosilicone oils tend to be limited to lower operating temperatures compared to PFPE oils (e.g., fluorosilicone oils are currently limited to 210°C whereas PFPEs has thermal stability up to 450°C). Dow Corning DS-1265 is an example of fluorosilicone oil and is widely used for high speed bearing lubrication in reactive environments.

[0023] PFPEs and fluorosilicone oils can be excellent lubricants under normal and severe operating conditions. Such lubricants are effective under heavy loads (e.g., when applied to gears), at high speeds (e.g., when applied to expander bearings), and at elevated temperatures. PFPEs and fluorosilicone oils form thicker oil films due to their high densities and high pressure-viscosity coefficients. Due to their excellent oxidation stability, PFPEs may be reclaimed even if contaminated with particles or other fluids (e.g., toluene blowing by the expander 110).

[0024] In one arrangement, in operation, the lubricant pump 206 is in fluid receiving communication with the reservoir 204 and in fluid providing communication with each of the bearings 202 and the transmission 112. The lubricant pump 206 creates a fluid pressure differential such that a lubricating medium is drawn from the reservoir 204 and delivered to the bearings 202 and the transmission 112. Over the course of operation of the system 100, the lubricating medium travels from the bearings 202 and the transmission 112 back to the reservoir 204, where it is again circulated through the rest of the lubrication circuit of the lubricating system 200.

[0025] Referring now to FIG. 3, a method 300 of manufacturing a waste heat recovery system is shown. The method 300 is performed using aspects of the ORC system 100 and the lubrication system 200 described with respect to FIGS. 1 and 2, above.

[0026] At 302, a conversion assembly (e.g., the conversion assembly 108) is coupled to an engine (e.g., the engine 102). The conversion assembly includes both an expander (e.g., the expander 110) and a transmission (e.g., the transmission 112). The expander includes one or more turbines disposed in line with an anticipated flow of working fluid in a gaseous state (e.g., in a gaseous state of matter, or as a dry vapor) and is configured to drive a rotation of a shaft. The shaft is communicatively engaged to the transmission, which includes one or more gearsets configured to receive a high speed shaft rotational input (i.e., from the expander) and provide a comparatively low speed rotational output (i.e., to the engine). The transmission is coupled to the engine in manner sufficient to supplement a mechanical force produced by the engine.

[0027] At 304, a boiler (e.g., the boiler 106) is coupled to an exhaust system. The exhaust system includes a system of conduits and chambers configured to route an exhaust gas (e.g., the exhaust gas 104) from the engine to the atmosphere. The boiler is coupled to the exhaust system in a manner sufficient for heat carried by the exhaust gas to be communicated to fluid within the boiler. For example, the boiler may include one or more fluid chambers annularly disposed about an outer circumference of one or more lengths of the exhaust. As another example, the boiler may include one or more fluid conduits disposed within one or more sections of the exhaust system itself. Other arrangements where fluid chambers or conduits are in heat exchanging communication with the exhaust system are possible.

[0028] At 306, a working fluid circuit is assembled. The working fluid circuit is assembled to provide a path of fluid travel that includes the conversion assembly and the boiler. In one arrangement, the working fluid circuit is assembled to include conduits and chambers configured to communicatively engage the boiler to the conversion assembly. Additional conduits and/or chambers may communicatively engage the conversion assembly to a condenser (e.g., the condenser 114), which may in turn be communicatively engaged to a working fluid pump (e.g., the working fluid pump 116). Finally, fluid conduits and/or chambers may connect the working fluid pump to the boiler 106. As such, in operation, the working fluid pump may provide pressure sufficient to cause a liquid from the condenser to flow into the boiler. Liquid in the boiler may then be converted into a gas, which may flow into the conversion assembly. The gas may then flow into the condenser, where it is converted back into a liquid and then pumped to the boiler via the working fluid pump 116.

[0029] At 308, a lubrication circuit is assembled. The lubrication circuit is assembled to provide a path of lubricant travel that includes moving components of the conversion assembly. In one arrangement, the lubrication circuit is assembled to include a lubricant reservoir (e.g., the lubricant reservoir 204) and a lubricant pump (e.g., the lubricant pump 206). Fluid conduits and/or chambers may be assembled such that the lubricant pump draws a lubricant from the lubricant reservoir and provides the lubricant to moving parts of the conversion assembly (e.g., the bearings 202 and the transmission 112). Lubricant from the moving parts of the conversion assembly may be collected and routed back to the lubricant reservoir.

[0030] At 310, the working fluid circuit is filled. The working fluid circuit may be filled with fluids that include fluorinated carbons (i.e., refrigerants) and hydrocarbons (e.g., n- pentane). In some arrangements, the working fluid circuit is filled with toluene. The working fluid circuit may be filled at an aperture that may be selectively opened and closed (e.g., an opening at a conduit or chamber with a complementary cap), for example at the boiler or the condenser.

[0031] At 312, the lubrication circuit is filled. The lubrication circuit is filled with a lubricating medium that includes at least one of perfluoro polyether (PFPE) and fluorosilicone lubricants. The lubrication circuit may be filled at an aperture that may be selectively opened and closed, for example at the lubricant reservoir or the conversion assembly. [0032] For the purpose of this disclosure, the terms "coupled" and "engaged" means the joining of two members directly or indirectly to one another. Such joining may be stationary or moveable in nature. Such joining may be achieved with the two members or the two members and any additional intermediate members being integrally formed as a single unitary body with one another or with the two members or the two members and any additional intermediate members being attached to one another. Such joining may be permanent in nature or may be removable or releasable in nature.

[0033] It should be noted that the orientation of various elements may differ according to other exemplary embodiments, and that such variations are intended to be encompassed by the present disclosure. It is recognized that features of the disclosed embodiments can be incorporated into other disclosed embodiments.

[0034] It is important to note that the constructions and arrangements of apparatuses or the components thereof as shown in the various exemplary embodiments are illustrative only. Although only a few embodiments have been described in detail in this disclosure, those skilled in the art who review this disclosure will readily appreciate that many modifications are possible (e.g., variations in sizes, dimensions, structures, shapes and proportions of the various elements, values of parameters, mounting arrangements, use of materials, colors, orientations, etc.) without materially departing from the novel teachings and advantages of the subject matter disclosed. For example, elements shown as integrally formed may be constructed of multiple parts or elements, the position of elements may be reversed or otherwise varied, and the nature or number of discrete elements or positions may be altered or varied. The order or sequence of any process or method steps may be varied or re-sequenced according to alternative embodiments. Other substitutions, modifications, changes and omissions may also be made in the design, operating conditions and arrangement of the various exemplary embodiments without departing from the scope of the present disclosure.

[0035] While various inventive embodiments have been described and illustrated herein, those of ordinary skill in the art will readily envision a variety of other mechanisms and/or structures for performing the function and/or obtaining the results and/or one or more of the advantages described herein, and each of such variations and/or modifications is deemed to be within the scope of the inventive embodiments described herein. More generally, those skilled in the art will readily appreciate that, unless otherwise noted, any parameters, dimensions, materials, and configurations described herein are meant to be exemplary and that the actual parameters, dimensions, materials, and/or configurations will depend upon the specific application or applications for which the inventive teachings is/are used. Those skilled in the art will recognize, or be able to ascertain using no more than routine experimentation, many equivalents to the specific inventive embodiments described herein. It is, therefore, to be understood that the foregoing embodiments are presented by way of example only and that, within the scope of the appended claims and equivalents thereto, inventive embodiments may be practiced otherwise than as specifically described and claimed. Inventive embodiments of the present disclosure are directed to each individual feature, system, article, material, kit, and/or method described herein. In addition, any combination of two or more such features, systems, articles, materials, kits, and/or methods, if such features, systems, articles, materials, kits, and/or methods are not mutually inconsistent, is included within the inventive scope of the present disclosure.

[0036] Also, the technology described herein may be embodied as a method, of which at least one example has been provided. The acts performed as part of the method may be ordered in any suitable way unless otherwise specifically noted. Accordingly, embodiments may be constructed in which acts are performed in an order different than illustrated, which may include performing some acts simultaneously, even though shown as sequential acts in illustrative embodiments.

[0037] The claims should not be read as limited to the described order or elements unless stated to that effect. It should be understood that various changes in form and detail may be made by one of ordinary skill in the art without departing from the spirit and scope of the appended claims. All embodiments that come within the spirit and scope of the following claims and equivalents thereto are claimed.