The present disclosure relates generally to internal combustion engines, and more particularly, to injection and emissions treatment systems and methods for such internal combustion engines.
Split cycle engines typically include a combustion cylinder and an expansion cylinder, with pistons in the cylinders driving the rotation of a crankshaft. Operation of the engine generates combustion products, which may require one or more treatment procedures in order to reduce potential harmful and/or dangerous gases. Moreover, one or more treatment procedures may require additional engine components and/or reduce engine operating efficiency. For example, split cycle engines may be powered by injecting and combusting hydrogen, which may generate nitrogen oxide gases (i.e., NO and NO2 gases), commonly referred to as NOx. The generation and corresponding management of NOx may limit the power generation, efficiency, performance, etc. of the split cycle engine.
U.S. Pat. No. 8,469,009, issued on Jun. 25, 2013 (“the '009 patent”), describes a gaseous-fueled internal combustion split cycle engine that is powered by a mixture of hydrogen and natural gas. The '009 patent discloses controlling respective concentrations of the mixture of hydrogen and natural gas and controlling the injection timing. Controlling the respective concentrations and the injection timing helps to improve combustion stability and reduce emissions of nitrogen oxide gas, exhaust particulate matter, and unburned hydrocarbons. However, the engine and methods disclosed by the '009 patent require a mixture of hydrogen and natural gas, which may result in the combustion generating soot and other harmful exhaust products, which may require additional treatment and/or impair the overall efficiency and power of the engine.
The systems and methods of the present disclosure may address or solve one or more of the problems set forth above and/or other problems in the art. The scope of the current disclosure, however, is defined by the attached claims, and not by the ability to solve any specific problem.
In one aspect, an engine system may include a first cylinder including a first piston, a second cylinder including a second piston, and a fuel injector fluidly connected to the first cylinder. The first cylinder may be a combustion cylinder, and the second cylinder may be an expansion cylinder. The second cylinder may be fluidly connected to the first cylinder when the first piston is in at least one position in the first cylinder. The fuel injector may be configured to deliver hydrogen gas to the first cylinder.
In another aspect, a hydrogen powered engine system may include a crankshaft, a first cylinder, a second cylinder, a fuel source, and a fuel injector. The first cylinder may include a first piston coupled to the crankshaft, and the first cylinder may be a combustion cylinder. The second cylinder may include a second piston coupled to the crankshaft, and the second cylinder may be an expansion cylinder. The second cylinder may be fluidly connected to the first cylinder via a gas crossover passage that allows combustion products to pass from the first cylinder to the second cylinder when the first piston is in at least one position in the first cylinder. The fuel source may contain a supply of hydrogen gas. The fuel injector may be fluidly connected to the fuel source and to the first cylinder. The fuel injector may be configured to deliver the hydrogen gas to the first cylinder.
In yet another aspect, a hydrogen powered engine system may include a first cylinder, a second cylinder, a fuel source, and a fuel injector. The first cylinder may include a first piston, and the first cylinder may be a combustion cylinder. The second cylinder may include a second piston, and the second cylinder may be an expansion cylinder. The second cylinder may be fluidly connected to the first cylinder. The fuel source may contain a supply of hydrogen gas. The fuel injector may be fluidly connected to the fuel source and to the first cylinder. The fuel injector may be configured to deliver the hydrogen gas to the first cylinder for a duration between approximately 15° crank angle and approximately 25° crank angle.
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate various exemplary embodiments and together with the description, serve to explain the principles of the disclosure.
Both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the features, as claimed. As used herein, the terms “comprises,” “comprising,” “having,” “including,” or other variations thereof, are intended to cover a non-exclusive inclusion such that a process, method, article, system, or apparatus that comprises a list of elements does not include only those elements, but may include other elements not expressly listed or inherent to such a process, method, article, or apparatus. Further, relative terms, such as, for example, “about,” “substantially,” “generally,” and “approximately” are used to indicate a possible variation of ±10% in a stated value.
Furthermore, the first cylinder 14 and second cylinder 16 and any additional cylinders added to this set can be treated as a module. Based on the target power requirements, there may be multiple copies or sets of these modules that could be connected to the crankshaft. For example, although not shown, there could be two sets of the cylinder arrangement that forms engine 10 shown in
First cylinder 14 and second cylinder 16 each define internal bearing surfaces. First cylinder 14 receives a first piston 24, which may be a combustion or power piston. Second cylinder 16 receives a second piston 26, which may be an expansion piston. First cylinder 14, cylinder head 22, and first piston 24 define a variable volume combustion chamber 25 in first cylinder 14. Second cylinder 16, cylinder head 22, and second piston 26 define a variable volume expansion or exhaust chamber 27 in second cylinder 16. Movement of first piston 24 in first cylinder 14 and/or movement of second piston 26 in second cylinder 16 may rotate crankshaft 18.
Crankshaft 18 includes a first crank throw 28 and a second crank throw 30. First crank throw 28 and second crank throw 30 may be axially displaced and angularly offset from each other, for example, having a phase angle 31 between first crank throw and second crank throw. First crank throw 28 may be pivotally coupled to first piston 24 by a first connecting rod 32, and second crank throw 30 may be pivotally coupled to second piston 26 by a second connecting rod 34. In these aspects, rotation of crankshaft 18, for example, in a clockwise direction, shown as arrow A, may reciprocate first piston 24 within first cylinder 14, and may also reciprocate second piston 26 within second cylinder 16. In this aspect, as first piston 24 is moving down toward its bottom dead center (BDC) position (as shown by arrow B) to increase the size of variable volume combustion chamber 25, second piston 26 is moving up away from its bottom dead center (BDC) (as shown by arrow C) to reduce the size of variable volume expansion or exhaust chamber 27.
Additionally, the angular offset (i.e., phase angle 31) between first crank throw 28 and second crank throw 30 may affect a timed relation between the reciprocation of first piston 24 and second piston 26. Geometric relationships of first cylinder 14, second cylinder 16, first piston 24, second piston 26, first crank throw 28, second crank throw 30, etc. may also affect the timed relation between the reciprocation of first piston 24 and second piston 26. Although not shown, one or more alternative mechanisms for relating the motion and timing of first piston 24 and second piston 26 may be utilized.
Cylinder head 22 and/or engine block 12 may include various conduits, passages, ports, valves, etc. that are suitable for split-cycle engine 10. As shown in
First cylinder 14 is fluidly connected to an air inlet port 42, which may be connected to a compressor 44. Compressor 44 may deliver air from an air intake and/or from second cylinder 16 to first cylinder 14, for example, via air inlet port 42. As discussed below, compressor 44 may be coupled to an exhaust conduit 45 that extends through a portion of engine block 12 to second cylinder 16, and may combine and/or mix exhaust from second cylinder 16 with fresh air before delivering the exhaust-air combination to first cylinder 14.
First cylinder 14 also is fluidly connected to an injection port 46, which may be connected to a fuel injector 48. As shown in
Furthermore, in one or more aspects, first cylinder 14 may be connected to a water injector 52. For example, water injector 52 may be fluidly connected to a water source (not shown). Alternatively or additionally, as shown in
Second cylinder 16 also fluidly connects to an exhaust port 56, for example, to discharge exhaust into the atmosphere. Moreover, second cylinder 16 may fluidly connect with a treatment passage 58. Treatment passage 58 may be fluidly connected to a treatment injector 60. For example, treatment injector 60 may deliver one or more treatment (e.g., aftertreatment) chemicals to second cylinder 16, which may help to reduce and/or modify the properties of the exhaust gas in second cylinder 16. In one or more aspects, treatment injector 60 may deliver urea to second cylinder 16. Alternatively or additionally, treatment injector 60 may deliver additional hydrogen gas (H2) to second cylinder 16.
One or more valves may control one or more of the above-discussed fluid flows. For example, engine 10 may include an intake valve 62, for example, including a camshaft 64 with a cam lobe 66. Intake valve 62 may help to control the flow of compressed air (either alone or mixed with exhaust) into first cylinder 14. Alternatively or additionally, intake valve 62 may help to prevent combusted air from flowing back out of first cylinder 14 and into air inlet port 42 and/or toward compressor 44. Engine 10 may also include an outlet valve 68, for example, including a camshaft 70 and a cam lobe 72. Outlet valve 68 may help to control the flow of combustion products and other resulting gases and/or materials from second cylinder 16, for example, to release combustion products, gases, materials, etc. into the atmosphere. Additionally, although not shown, engine 10 may include one or more check valves, pressure relief valves, etc.
Furthermore, a spark plug 74 may be mounted in or otherwise be coupled to engine block 12 and/or cylinder head 22. Spark plug 74 may include one or more electrodes extending into first cylinder 14 and variable volume combustion chamber 25 for igniting air-fuel charges. The ignition may be controlled by an ignition control (not shown), for example, with the ignition being executed at precise times relative to the operating cycle of engine 10, for example, including first piston 24. Alternatively, engine 10 may include one or more additional or separate heating elements, for example, a heating dome within first cylinder 14 for ignition, and the one or more heating elements also may be controlled by an ignition control (not shown).
As discussed above, engine 10 may include compressor 44, which may receive and direct air and exhaust gas into first cylinder 14. For example, compressor 44 may include a source or an intake of fresh air 82, for example, fluidly connected to an exterior of engine 10, for example, an exterior of a vehicle or machine that is powered by engine 10. Compressor 44 may also be fluidly connected to second cylinder 16, for example, to receive exhaust gases from second cylinder 16. In this aspect, compressor 44 may direct exhaust gases from second cylinder 16 for exhaust gas recirculation (EGR), for example, via exhaust conduit 45. Compressor 44 may combine and/or mix the received fresh air from the source or intake of fresh air 82 and the exhaust gases received from second cylinder 16, and compressor 44 may direct a combination of fresh air and exhaust gas into first cylinder 14. For example, compressor 44 may compress the combination of fresh air (i.e., from the source or intake of fresh air 82) and exhaust gas (i.e., from second cylinder 16) before directing the combination of fresh air and exhaust gas into first cylinder 14. In one or more aspects, the combination of fresh air and exhaust gas may include a concentration of greater than or equal to approximately 40% exhaust gas. In this aspect, fresh air may comprise the remainder of the fluid delivered by compressor 44 to first cylinder 14. In these aspects, a method of operating engine 10 may include recirculating exhaust gases from the second cylinder 16, through compressor 44, and into first cylinder 14, according to one or more of the above parameters.
Additionally, engine 10 may include fuel injector 48, which may receive and direct fuel into first cylinder 14. As discussed above, fuel injector 48 may receive and direct hydrogen gas (e.g., H2) into first cylinder 14, for example, for hydrogen direct injection. For example, fuel injector 48 may be fluidly connected to fuel source 50, and fuel source 50 may contain a supply of hydrogen gas (e.g., H2). In one or more aspects, fuel injector 48 may include tip 49, which may be a domed tip, to direct the hydrogen gas into first cylinder 14. Fuel injector 48 may inject the hydrogen gas into first cylinder 14 at an injection pressure that is less than or equal to approximately 600 bar, for example, less than or equal to approximately 400 bar. In one or more aspects, fuel injector 48 may direct hydrogen gas into first cylinder 14 at a start of injection (SOI) in a range between approximately 30° before top dead center (bTDC) and approximately 0° before top dead center, for example, at top dead center. For example, fuel injector 48 may direct hydrogen gas into first cylinder 14 at a start of injection (SOI) in a range between approximately 10° before top dead center (bTDC) and approximately 0° before top dead center, for example, at top dead center. Furthermore, in one or more aspects, fuel injector 48 may inject fuel for a duration between 5° crank angle to 30° crank angle from the time of start of injection, for example for an injection duration of 15 crank angle degrees. In one aspect, fuel injector 48 may inject fuel for a duration between approximately 15° crank angle and up to approximately 25° crank angle, for example, for a duration of approximately 20 crank angle degrees. In these aspects, a method of operating engine 10 may include injecting the hydrogen into first cylinder 14, according to one or more of the above parameters.
Engine 10 may also include pump 54 to direct water from second cylinder 16 into first cylinder 14. For example, pump 54 may be fluidly connected to an outlet of second cylinder 16 (e.g., water conduit 55) and to an inlet (e.g., water injector 52) in first cylinder 14. Pump 54 may help to remove exhaust water (e.g., in a liquid state or in a gaseous state) from second cylinder 16. Additionally, pump 54 may direct water into first cylinder 14, for example, via water injector 52 (
Moreover, in one or more aspects, engine 10 may include one or more treatment injectors 60, for example, on or within second cylinder 16. Treatment injector 60 may be positioned on or within second cylinder 16, and may deliver a treatment chemical, to within second cylinder 16, to help reduce the amount of NOx within second cylinder 16. In one example, treatment injector 60 may deliver and/or inject urea (CO(NH2)2) to within second cylinder 16. In another example, treatment injector 60 may deliver and/or inject of hydrogen gas (i.e., H2 gas) to within second cylinder 16. In these aspects, a method of operating engine 10 may include injecting one or more treatment chemicals into second cylinder 16, according to one or more of the above parameters. Additionally, portions of the second cylinder 16 maybe coated with a catalytic compound to accelerate the NOx reduction 84. The NOx reduction process 84 converts NOx to nitrogen gas (N2) and water (H2O). The water may be directed to first cylinder 14, for example, via pump 54 and water injector 52. Additionally, the nitrogen gas may be directed to first cylinder 14, for example, via compressor 44. In these aspects, a method of operating engine 10 may include one or more NOx reduction 84 techniques in second cylinder 16, according to one or more of the above parameters.
It is noted that while
The disclosed engine 10, including one or more of the aspects discussed herein, may be used to power any vehicle or machine. Additionally, various aspects of engine 10 may help to improve engine efficiency and/or performance, while also reducing the production and/or emission of harmful exhaust products (i.e., nitrogen gases). In some examples, various aspects of engine 10 may help to increase an efficiency of engine 10, for example, by approximately 5%, by approximately 10%, by approximately 20%, etc. Various aspects of engine 10 may help to reduce emissions, for example, by emitting only water as a byproduct and/or by emitting a reduced level of nitrogen oxide gases. Additionally, various aspects of engine 10 may also help to reduce overall costs of engine 10, for example, compared to diesel-powered engines with similar performance characteristics.
As discussed above, engine 10 may be a split-cycle engine, and may operate by combusting hydrogen gas (e.g., H2 gas). In this aspect, engine 10 may divide four strokes between two paired cylinders, with one cylinder for intake and compression, and another cylinder for power and exhaust. For example, first cylinder 14 may be used for intake and compression of injected hydrogen, and second cylinder 16 may be used for power and exhaust. The hydrogen gas may combust at relatively high temperatures (approximately 3000 K or greater) relative to other combustion engines (i.e., diesel combusts at approximately 2700 K) for similar loads. Because hydrogen gas does not contain any carbon, the combustion of the hydrogen gas does not generate any soot or carbon dioxide (CO2). Moreover, combusting hydrogen gas may generate little or no particulate matter or other emissions associated with other internal combustion engines. Combusting hydrogen gas may generate nitrogen oxide gases (NOx), which may limit the performance of engine 10. Nevertheless, because there is no carbon combusted or soot generated, engine 10 may include one or more features and/or components that may help to reduce the amount of nitrogen oxide gases that is generated during the combustion of hydrogen gas (H2).
Engine 10 may include a delayed and/or retarded combustion phasing using late injection timings and/or extended durations. As mentioned above, fuel injector 48 may direct hydrogen gas (e.g., pure hydrogen gas) into first cylinder 14 at an injection pressure that is less than or equal to approximately 600 bar, for example, less than or equal to approximately 400 bar. For example, fuel injector 48 may direct hydrogen gas into first cylinder 14 at a start of injection (SOI) in a range between approximately 30° before top dead center (bTDC) and approximately 0° before top dead center, for example, at top dead center. In another aspect, fuel injector 48 may direct hydrogen gas into first cylinder 14 at a start of injection (SOI) in a range between approximately 10° before top dead center (bTDC) and approximately 0° before top dead center, for example, at top dead center. Furthermore, in one or more aspects, fuel injector 48 may inject fuel for a duration between approximately 5° crank angle to approximately 30° crank angle from the time of start of injection, for example for an injection duration of approximately 15 crank angle degrees. For example, fuel injector 48 may inject fuel for a duration between approximately 15° crank angle up to approximately 25° crank angle, for example, for a duration of approximately 20 crank angle degrees. These injection details (e.g., late injection timings and/or extended injection durations) may help to reduce the overall formation and/or emission of nitrogen oxide gases, which may help to improve the overall fluid consumption by allowing for an amount of hydrogen gas to generate a greater power from engine 10.
Furthermore, as discussed above, engine 10 may include water injector 52, which may direct water from second cylinder 16 into first cylinder 14, for example, via water conduit 55 and pump 54. Injecting water into first cylinder 14 may help to control (e.g., limit and/or reduce) the formation of nitrogen oxide and/or to control (e.g., limit and/or reduce) the temperatures within first cylinder 14. Engine 10 operates on hydrogen gas (H2), and thus produces water, for example, as combustion products 80 cool and/or expand in second cylinder 16 and/or upon exiting second cylinder 16. The water may cool (i.e., condense) in second cylinder 16 and/or upon exiting second cylinder 16, for example, through expansion in second cylinder 16 and/or via heat transfer (e.g., with water conduit 55 and/or exhaust port 56) upon exiting second cylinder 16. Cooling the water in second cylinder 16, and/or via heat transfer after exiting second cylinder 16, does not require a separate active cooling system. Alternatively, one or more heat exchangers may be used to cool the water upon exiting second cylinder 16, for example, positioned between second cylinder 16 and pump 54. The water that condenses in second cylinder 16 and/or after exiting second cylinder 16 may be recirculated by pump 54 and injected into first cylinder 14 via water injector 52. The water may be injected into first cylinder before the injection of the hydrogen gas for combustion. Alternatively or additionally, the water may be injected into first cylinder 14 and/or second cylinder 16 during the transfer of gases (i.e., combustion products 80) from first cylinder 14 to second cylinder 16. As such, water may be injected into first cylinder 14 and/or second cylinder 16, without a need for a separate water supply. The water injection may help to control (e.g., limit and/or reduce) the in-cylinder temperatures, reduce the transfer of heat between first cylinder 14 and second cylinder 16, and, as a result, reduce the generation and/or emission of nitrogen oxide gases (NOx).
Additionally, engine 10 may include treatment injector 60, which may inject urea (CO(NH2)2) into second cylinder 16. As mentioned above, hydrogen gas combusts at a high temperature relative to other combustible gases, so second cylinder 16 experiences high temperatures during its cycle, for example, as combustion products 80 expand to ambient temperature. Additionally, second cylinder 16 may have a relatively large closed controlled volume during the expansion process. The high temperatures and expansion in second cylinder 16 may provide a suitable environment for urea to be directly injected into second cylinder 16 and treat combustion products 80 in second cylinder 16 to reduce the amount of nitrogen oxide gases (NOx). In one or more aspects, injecting urea into second cylinder 16 may reduce the formation and/or emission of nitrogen oxide gases (NOx) without a need for a separate selective catalyst reduction system. Alternatively or additionally, treatment injector 60 may deliver hydrogen gas (H2) to second cylinder 16, which may also reduce the formation and/or emission of nitrogen oxide gases (NOx) without a separate selective catalyst reduction system.
Various aspects of this disclosure may help to improve the overall performance of a hydrogen engine. For example, various aspects of this disclosure may help to increase the power generated by engine 10 and/or improving the performance efficiency of engine 10. Moreover, as discussed above, various aspects of this disclosure may help to reduce the formation and/or emission of nitrogen oxide gases (NOx).
It will be apparent to those skilled in the art that various modifications and variations can be made to the disclosed system without departing from the scope of the disclosure. Other embodiments of the disclosure will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the invention being indicated by the following claims.
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