Patent Grant
12158121
The present disclosure relates generally to emissions mitigation in an internal combustion engine system, and more particularly to collecting exhaust containing unburned hydrocarbons from an exhaust port in an engine.
Internal combustion engines are used globally for diverse purposes ranging from electric power generation to vehicle propulsion, operation of pumps and compressor, and in still other applications. In a typical arrangement, a fuel is admitted with air into cylinders in the engine and ignited to cause a controlled combustion reaction that drives pistons in the cylinders coupled to a crankshaft. A wide range of fuel types have been used in internal combustion engines over the years, ranging from gasoline, diesel, to various gaseous fuels such as natural gas or other gaseous hydrocarbon fuels and blends thereof.
Gaseous fuels continue to attract engineering resources, given the lower levels of certain emissions that tend to be produced. Gaseous fuels, for example, tend to produce few emissions of particulate matter. More recently, increased interest has been given to exploitation of gaseous hydrogen fuels such as gaseous molecular hydrogen.
It is generally desirable to burn as high a proportion of a fuel admitted into in an engine as is practicable. Where less than all of the fuel is burned, efficiency penalties are observed if otherwise utilizable fuel is discharged in exhaust from the engine. Moreover, the discharge of the unburned fuel can be considered objectionable given that certain unburned fuels are considered to be so-called greenhouse gases or “GHG.” Unburned hydrocarbon emissions can be observed in any engine but may be especially undesirable in gaseous fuel engines where the fuel includes at least some methane.
Various strategies are known for mitigating unburned hydrocarbon emissions, including by way of conventional exhaust gas recirculation where exhaust containing unburned hydrocarbons is recirculated to an intake system for the engine. Other efforts attempt to minimize unburned hydrocarbons by way of the conditions of the combustion itself. One known strategy apparently associated with reduced amounts of unburned hydrocarbons in-cylinder is set forth in United States Patent Application Publication No. 20120227387 to Willi. The art provides ample room for improvement and development of alternative strategies.
In one aspect, an engine system includes an engine having a cylinder block with a plurality of cylinders formed therein, a cylinder head attached to the cylinder block and having a plurality of intake ports and a plurality of exhaust ports, and an intake manifold and an exhaust manifold each attached to the cylinder block. The cylinder head further has formed therein a plurality of exhaust collection passages each fluidly connected to one of the plurality of exhaust ports at an unburned hydrocarbon (UHC) collection location. The engine system further includes an exhaust conduit fluidly connected to the exhaust manifold, and a UHC emissions mitigation conduit fluidly connected to the plurality of exhaust collection passages.
In another aspect, a cylinder head for an engine includes a cylinder head casting having formed therein a coolant cavity extending between an upper deck having an upper deck surface, and a lower deck having a lower deck surface. The cylinder head casting further includes an intake port extending through the coolant cavity to an intake opening in the lower deck forming an intake valve seat, and an exhaust port extending through the coolant cavity from an exhaust opening in the lower deck forming an exhaust valve seat to an exhaust manifold feed opening. The cylinder head casting further has formed therein an exhaust collection passage fluidly connected to the exhaust port at an unburned hydrocarbon (UHC) collection location vertically between the upper deck and the lower deck, and fluidly between the exhaust valve seat and manifold feed opening.
In still another aspect, a method of operating an engine system includes combusting a gaseous fuel containing gaseous hydrocarbon (HC) and air in a cylinder in an engine, and moving a piston in an exhaust stroke toward a top dead center position in the cylinder. The method further includes conveying exhaust expelled from the cylinder via the moving of the piston through an exhaust port to an exhaust manifold while an exhaust valve of the engine is open, and collecting exhaust directly from the exhaust port while the exhaust valve is closed via an exhaust collection passage extending through a cylinder head forming the exhaust port. The method further includes oxidizing unburned hydrocarbon (UHC) in the collected exhaust.
Referring to
Engine system 10 also includes a fuel supply 36. Fuel supply 36 may include a line gas supply receiving a feed of a gaseous fuel from a gas field or a stored gaseous fuel supply, for example. Gaseous fuels used in engine system 10 may include natural gas (NG), methane, ethane, various blends of gaseous hydrocarbon fuel (HC), or still others. In some embodiments engine system 10 can be operated on a blend of HC and a gaseous hydrogen fuel such as gaseous molecular hydrogen. Engine system 10 could also be a dual fuel engine utilizing pilot injections of a liquid fuel such as a compression-ignition diesel fuel that ignite a larger charge of a gaseous fuel in a cylinder. In an implementation engine 12 is spark-ignited and each of cylinders 16 equipped with a spark ignition device, such as a prechamber sparkplug.
A filter 38 or other processing equipment receives a flow of gaseous fuel from fuel supply 36, which is conveyed to a fuel admission valve 50. Fuel admission valve 50 admits gaseous fuel to an intake conduit 40 receiving a feed of intake air from a filtered air inlet 42. Engine system 10 also includes a turbocharger 58 including a turbine 62 within intake conduit 40. A mixture of air and fuel is pressurized by way of compressor 62 and conveyed through intake conduit 40 to an intake manifold 24 attached to a cylinder head 18, typically passing through an aftercooler 44. Engine 12 also includes an exhaust manifold 26 attached to cylinder head 18, and an engine exhaust conduit 46 fluidly connected to exhaust manifold 26 and to an exhaust outlet 48. A turbine 60 of turbocharger 58 is within exhaust conduit 46 and rotated by way of a flow of exhaust to operate compressor 62. In the illustrated embodiment, fuel is delivered to engine 12 by way of fumigation. In other embodiments fuel could be port-injected, direct-injected, delivered by a combination of direct injection or port injection and fumigation, or by still another strategy such as intake manifold injection.
Cylinder head 18 is attached to cylinder block 14 and includes a plurality of intake ports 20 and a plurality of exhaust ports 22 each connected to a respective one of cylinders 16 to convey intake air and fuel, and exhaust, respectively, in a generally known manner. Cylinder head 18 further has formed therein a plurality of exhaust collection passages 54 each fluidly connected to one of the plurality of exhaust ports 22 at an unburned hydrocarbon (UHC) collection location. Collecting exhaust at locations where the exhaust is relatively rich in UHC compared to exhaust collected at other locations, as further discussed therein, can assist in mitigating UHC emissions according to a number of different strategies.
To this end, engine system further includes a UHC emissions mitigation conduit 56 fluidly connected to the plurality of exhaust collection passages 54. In the illustrated embodiment, UHC emissions mitigation conduit 56 fluidly connects to intake conduit 40 at a location fluidly upstream of compressor 62. Upstream means away from engine 12 and toward filtered air inlet 42. In some embodiments engine system 10 may also include an electrically actuated valve 64 within UHC emissions mitigation conduit 56 and movable between an open position, and a closed position. Engine system 10 may also include an electronic control unit 66 in control communication with valve 64, and also in control communication with fuel admission valve 50.
Valve 64 can enable selective recirculation of exhaust rich in UHC to compressor 62 for returning to engine 12 to be combusted in cylinders 16. In some embodiments, an electrically actuated valve may not be used, and instead fluid connection between exhaust collection passages and an intake conduit, or an exhaust conduit as described in connection with other embodiments, may be continuous. Some back pressure of outgoing exhaust may be continuously present while engine 12 is running, thus enabling collected exhaust to flow more or less continuously. Moreover, embodiments are contemplated where collected exhaust is returned at a different location than that specifically illustrated, such as at a location fluidly between aftercooler 44 and intake manifold 24, or otherwise admitted or injected at still other locations in engine system 10.
Focusing now on
Engine system 110 also includes a UHC emissions mitigation conduit 156 fluidly connected to exhaust collection passages 54. In the illustrated embodiment, UHC emissions mitigation conduit 156 fluidly connects to engine exhaust conduit 146 at a location fluidly downstream of turbine 160. Engine system 110 may also include an oxidation catalyst 161 within UHC emissions mitigation conduit 156. Oxidation catalyst 161 may be any suitable precious metal or non-precious metal oxidation catalyst, including those generally commercially available and known as a diesel oxidation catalyst or DOC. As illustrated, collected exhaust can be conveyed by way of passages 154 to a location downstream of turbine 160, and the oxidized products discharged via an exhaust stack, tailpipe, etc.
Returning to the embodiment of
Also depicted in
In a natural gas gaseous fuel engine approximately 1-2% of methane admitted to a cylinder for combustion may remain unburned resulting in so-called “methane slip” that can otherwise be discharged to atmosphere or require an expensive full-size oxidation catalyst. According to the present disclosure, approximately 5% of the engine exhaust may be collected in some embodiments. It has been discovered that by selecting the UHC collection location strategically, relatively close to the cylinder, the portion of exhaust relatively richest in UHC can be collected, and the UHC oxidized efficiently using a relatively small and inexpensive oxidation catalyst apparatus. Moreover, as the exhaust tends to be quite hot near the cylinder the oxidation of the UHC can be expected to be robust as compared to what might occur with cooler exhaust collected and/or treated further away from the engine, such as downstream of a turbocharger.
Focusing now on
It can also be noted from
Referring now to
Referring to the drawings generally, but focusing for description on the embodiment of
As noted above, a concentration of UHC in the bulk of the exhaust will tend to be relatively leaner. Accordingly, during a majority of the exhaust stroke the exhaust conveyed to the exhaust manifold is relatively leaner in UHC. Just prior to the end of an exhaust stroke, however, crevice volume exhaust containing some residual UHC can be expelled from the cylinder just before the exhaust valve closes. According to the present disclosure, this final amount of expelled exhaust can be relatively richer in UHC, and will tend to become trapped in the exhaust port until the next exhaust stroke absent mitigation. In a conventional strategy, the next time the exhaust valve opens this small amount of exhaust relatively rich in UHC will be conveyed on to the exhaust manifold and potentially be discharged untreated. The present disclosure, however, proposes collecting exhaust directly from the exhaust port while the exhaust valve is closed via exhaust collection passages extending through the cylinder head. According to the present disclosure, the collected exhaust can then be conveyed back into the engine by way of recirculation for combustion, oxidized in an oxidation catalyst, or treated by still another strategy.
Referring now to
The present description is for illustrative purposes only, and should not be construed to narrow the breadth of the present disclosure in any way. Thus, those skilled in the art will appreciate that various modifications might be made to the presently disclosed embodiments without departing from the full and fair scope and spirit of the present disclosure. Other aspects, features and advantages will be apparent upon an examination of the attached drawings and appended claims. As used herein, the articles “a” and “an” are intended to include one or more items, and may be used interchangeably with “one or more.” Where only one item is intended, the term “one” or similar language is used. Also, as used herein, the terms “has,” “have,” “having,” or the like are intended to be open-ended terms. Further, the phrase “based on” is intended to mean “based, at least in part, on” unless explicitly stated otherwise.
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| Number | Date | Country | |
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| 20240068425 A1 | Feb 2024 | US |
