Use of special engine cylinders for the production of reducing agents

Abstract

A system (500; 600) for use with an engine (510; 610) having a first cylinder (514; 614) and a second cylinder (518; 618), the system comprising: a first inlet (502; 602) configured to receive air; an intake manifold (507; 607) configured to receive the air from the first intake (502; 602) and supply the air to the first cylinder and the second cylinder; an exhaust manifold (532; 632) configured to receive exhaust gases from the first cylinder and the second cylinder, the exhaust manifold comprising: a first exhaust outlet conduit (526; 626) configured to receive the exhaust gas from the first cylinder; and a second exhaust outlet conduit (528; 628) configured to receive the exhaust gas from the second cylinder; a first catalyst (522; 622) disposed along the second exhaust outlet conduit (528; 628) and configured to receive the exhaust gas from the second cylinder and produce ammonia; a first exhaust gas recirculation line (570; 670) connected to the first exhaust outlet line (526; 626) and the intake manifold (507; 607) and configured to selectively supply the exhaust gas from the first exhaust outlet line to the intake manifold; a first compressor (244; 644) configured to receive the air from the first inlet and compress the air before supplying the air to the intake manifold (507; 607); and a turbine (246; 646) configured to receive the exhaust gas from the first exhaust outlet conduit (526; 626) and the exhaust gas from the second exhaust outlet conduit (528; 628); a second inlet (603) coupled to the first inlet (602) upstream of the first compressor (644) and configured to receive the air; and a second compressor (643) configured to receive the air from the second inlet and compress the air before supplying the air to the intake manifold (507; 607), the second compressor being operatively connected to the first compressor; wherein the second exhaust outlet conduit (528; 628) is isolated from the first exhaust outlet conduit upstream of the first catalyst (522; 622) and is connected to the first exhaust outlet conduit downstream of the first catalyst; wherein the intake manifold (507; 607) comprises: a first intake manifold conduit (506; 606) configured to receive the air from the first compressor and supply the air to the first cylinder; and a second intake manifold conduit (508; 608) configured to receive the air from the second compressor and supply the air to the second cylinder; and wherein the first exhaust gas recirculation line (570; 670) is connected to the first intake manifold line (506; 606).

Description

TECHNICAL FIELD

[0001] The present disclosure generally relates to systems and methods for use with internal combustion (IC) engines and aftertreatment systems for use with IC engines. BACKGROUND

[0002] Exhaust aftertreatment systems are used to capture and treat the exhaust gases produced by IC engines. Exhaust gases produced by internal combustion engines using fuels such as gasoline, diesel, liquefied petroleum gas (LPG), ethanol, natural gas, and / or dual-fuel variants contain NOx gases, carbon monoxide (CO), and / or unburned hydrocarbons, which must be neutralized before the exhaust gases are released into the environment. Aftertreatment systems used to treat the exhaust gases produced by IC engines operating under stoichiometric conditions often include a three-way catalyst configured to efficiently decompose NOx gases, CO, and unburned hydrocarbons contained in the exhaust. However, lean-burn engines cannot effectively decompose NOx gases with a three-way catalyst.A selective catalytic reduction (SCR) device, usually in conjunction with a reductant injection system (e.g., urea water (HWL)), is generally used to efficiently decompose NOx emissions in a lean environment.

[0003] Three-way catalysts are effective when the engine operates at a narrow air / fuel ratio (A / F) close to the stoichiometric point, so that the exhaust gas composition fluctuates between rich (excess fuel) and lean (excess oxygen) conditions. Conversion efficiency drops very rapidly when the engine operates outside this range. In lean engine operation, the exhaust gas contains excess oxygen, and NOx reduction is not favored. Under rich conditions, the excess fuel consumes all available oxygen upstream of the catalyst, resulting in poor reduction of CO and unburned hydrocarbons and the formation of ammonia from NOx. From a fuel efficiency perspective, it is advantageous to operate the engine under lean conditions to minimize fuel consumption and maximize fuel efficiency.However, the limitation imposed by the three-way catalyst to operate within the tight air / fuel ratio prevents this from being a viable option. HWL injection is used in conjunction with SKR technology in some lean-burn engine configurations. However, HWL-SKR technology imposes significant cost and control requirements.

[0004] Another exhaust gas aftertreatment system is known from US Pat. No. 7,464,540 B2. US Pat. No. 5,974,793 A describes another known exhaust gas aftertreatment system. A method for operating an internal combustion engine and an internal combustion engine are known from DE 103 57 402 A1. An internal combustion engine with multiple throttles in the intake manifold arrangement is described in DE 38 10 750 C2. SUMMARY

[0005] Embodiments described herein generally relate to systems and methods for operating internal combustion engines to increase engine fuel efficiency without compromising aftertreatment system performance, and more particularly to operating a first set of cylinders of an internal combustion engine under lean conditions and a second set of cylinders of an internal combustion engine under rich conditions and passing exhaust gas produced by the second set of cylinders through an ammonia-producing catalyst.

[0006] A system for use with an engine according to the present invention is set out in claim 1. A method of operating an engine having a plurality of cylinders is set out in claim 13. A controller for operating an engine having a plurality of cylinders is set out in claim 17. Further preferred embodiments are set out in the dependent claims.

[0007] In a first set of embodiments, a system comprises an engine including a plurality of cylinders. A first intake valve is disposed upstream of the first cylinder set of a plurality of cylinders. The first intake valve provides air to the first cylinder set at a first flow rate to create a combustible lean air / fuel mixture in the first cylinder set of a plurality of cylinders. A second intake valve is disposed downstream of a second cylinder set of a plurality of cylinders and parallel to the first intake valve. The second intake valve provides air to the second cylinder set at a second flow rate to create a combustible lean air / fuel mixture in the second cylinder set of a plurality of cylinders.

[0008] In another set of embodiments, a system includes an engine having a plurality of cylinders and a first set of cylinders configured to combust an air / fuel mixture at a first equivalence ratio. The first set of cylinders produces a first exhaust portion. A second set of cylinders is configured to combust an air / fuel mixture at a second equivalence ratio different from the first equivalence ratio. The second set of cylinders produces a second exhaust portion. An ammonia-producing catalyst is disposed downstream of and in fluid communication with the second set of cylinders. The ammonia-producing catalyst receives only the second exhaust portion and converts NOx gases contained in the second exhaust portion into ammonia. A selective catalytic reduction device is disposed downstream of the plurality of cylinders.The selective catalytic reduction device absorbs the first exhaust gas portion and the second exhaust gas portion with the ammonia contained therein.

[0009] In yet another set of embodiments, a method of operating an engine including a plurality of cylinders comprises providing a lean air / fuel mixture to a first set of cylinders of the plurality of cylinders. The first set of cylinders is operated at a first compression ratio. A rich air / fuel mixture is provided to a second set of cylinders of the plurality of cylinders. The second set of cylinders is operated at a second compression ratio different from the first compression ratio. A second exhaust portion produced by the second set of cylinders is passed through an ammonia-producing catalyst of an aftertreatment system. The second exhaust portion is passed through at least one downstream aftertreatment component of the aftertreatment system.A first exhaust gas portion produced by the first set of cylinders is directed through at least one downstream aftertreatment component such that the first exhaust gas portion bypasses the ammonia-producing catalyst.

[0010] In yet another set of embodiments, a system comprises an engine including a plurality of cylinders. A first intake door is disposed upstream of the first cylinder set of a plurality of cylinders. A second intake door is disposed upstream of the second cylinder set of a plurality of cylinders. An ammonia-generating catalyst is disposed downstream of the second cylinder set. A controller is communicatively coupled to each of the first intake door and the second intake door. The controller includes a first intake door circuit configured to command the first intake door to direct air into the first cylinder set at a first flow rate. The first air flow rate creates a lean air / fuel mixture in the first cylinder set. A second intake door circuit is configured to command the second intake door to direct air into the second cylinder set at a second flow rate.The second air flow rate creates a rich air / fuel mixture in the second cylinder set. An ammonia determination circuit is configured to determine the molar flow rate of ammonia produced by the ammonia-generating catalyst. A NOx determination circuit is configured to determine the molar NOx flow rate produced by the first cylinder set. Further, a NOx / ammonia ratio control circuit is configured to control the molar NOx flow rate in the first cylinder set and the molar ammonia flow rate in the second cylinder set such that the NOx to ammonia ratio is 1.

[0011] It should be understood that all combinations of the foregoing concepts and other concepts discussed in more detail below (provided these concepts are not mutually incompatible) are intended to be part of the inventive subject matter disclosed herein. In particular, all combinations of the claimed subject matter listed at the end of this disclosure are intended to be part of the inventive subject matter disclosed herein. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The foregoing and other features of the present disclosure will become more apparent from the following description and appended claims, which should be read in conjunction with the accompanying drawings. While these drawings merely illustrate several embodiments in accordance with the disclosure and are therefore not to be considered limiting of its scope, the disclosure will be described in greater detail and particularity using the accompanying drawings. Fig. 1 is a schematic representation of a system including an internal combustion engine fluidly coupled to an aftertreatment system according to one embodiment. Fig. Figure 2 shows a schematic block diagram of an embodiment of a control circuit including a controller incorporated into the system of Fig. 1 can be recorded. Fig. 3 is a schematic representation of another embodiment of a system including an internal combustion engine fluidly coupled to an aftertreatment system including numerous aftertreatment components. Fig. 4 is a schematic representation of another embodiment of a system including an internal combustion engine fluidly coupled to an aftertreatment system. Fig. 5 is a schematic representation of another embodiment of a system including an internal combustion engine fluidly coupled to an aftertreatment system. Fig. 6 is a schematic flow diagram of one embodiment of a method for operating a plurality of cylinders of an internal combustion engine. Fig. Figure 7 is a schematic block diagram of a computer device used as a controller of Fig. 1 and / or Fig. 2 can be used.

[0013] Throughout the following detailed description, reference is made to the accompanying drawings. In the drawings, like symbols normally identify like components unless the context dictates otherwise. The illustrative embodiments described in the detailed description, drawings, and claims are not intended to be limiting. Other embodiments may be utilized, and other changes may be made, without departing from the spirit or scope of the subject matter presented herein. It is contemplated that the aspects of the present disclosure, as generally described herein and illustrated in the drawings, may be arranged, substituted, combined, and designed in many different configurations, all of which are expressly contemplated and constitute a part of this disclosure. DETAILED DESCRIPTION OF VARIOUS EMBODIMENTS

[0014] Embodiments described herein generally relate to systems and methods for operating internal combustion engines to increase engine fuel efficiency without compromising aftertreatment system performance, and more particularly to operating a first set of cylinders of an internal combustion engine under lean conditions and a second set of cylinders of an internal combustion engine under rich conditions and passing exhaust gas produced by the second set of cylinders through an ammonia-producing catalyst.

[0015] As described herein, the term "lean air / fuel mixture" refers to an air / fuel mixture with a fuel / air equivalence ratio (φ) of less than 1.0. As described herein, the term "rich air / fuel mixture" refers to an air / fuel mixture with a fuel / air equivalence ratio (φ) of greater than 1.0.

[0016] As described here, the term "combustion phasing" refers to the location of combustion relative to the piston at top dead center (TDC), typically measured in crank angle degrees (CAD). A change in combustion phasing causes a change in piston position during the maximum apparent heat release rate, which directly affects peak combustion temperatures.

[0017] Operating internal combustion engines, such as gasoline, ethanol, liquefied petroleum gas, or natural gas engines, under lean conditions is advantageous because it improves fuel efficiency and extends the operating range of engines, such as the range of a vehicle including the engine. Lean operation also allows for increasing the compression ratio of engine cylinders due to improved resistance to auto-ignition. The increased compression ratio improves combustion stability and increases brake thermal efficiency.However, the three-way catalyst generally used in an aftertreatment system associated with such engines cannot efficiently decompose NOx gases contained in the exhaust gas with the higher amount of oxygen in the exhaust gas emitted by the engines operating on a lean air / fuel mixture.

[0018] Various embodiments of the systems and methods for operating one set of cylinders of an engine with a lean air / fuel mixture and a second set of cylinders of the engine with a rich air / fuel mixture may provide advantages including, for example, (1) operating the first set of cylinders under lean conditions at all times, even at high engine loads, thereby enabling higher engine efficiency and a higher compression ratio due to greater resistance to auto-ignition; (2) increasing engine efficiency and operating range; (3) enabling lower combustion temperatures and better heat transfer; (4) generating a reductant in situ using an ammonia-generating catalyst that takes a portion of an exhaust gas from a second set of cylinders operating under rich conditions;(5) increasing the average specific heat ratio of the first cylinder set, thereby allowing more useful work to be extracted during expansion; (6) reducing pumping losses of the first cylinder set during part-load engine operation; (7) enabling the second cylinder set to operate under rich conditions regardless of engine load; and (8) providing a proportional ratio of ammonia to NOx gases, thereby maintaining the efficiency of the aftertreatment system in decomposing NOx gases contained in the exhaust fraction produced by the first cylinder set.

[0019] Fig. 1 is a schematic representation of a system 100 including an internal combustion engine 110 fluidly coupled to an aftertreatment system 150 and optionally a controller 170. The internal combustion engine 110 includes an engine cylinder block 112 having a plurality of cylinders including a first cylinder 114a, a second cylinder 114b, a third cylinder 114c (collectively referred to herein as a “first cylinder set 114”), and a fourth cylinder 118. The system 100 includes a first intake valve 104, a second intake valve 109. The aftertreatment system 150 includes an SKR system 152, and optionally an oxidation catalyst 160. Each of the plurality of cylinders includes a piston (not shown) for compressing an air / fuel mixture introduced therein to a predetermined compression ratio, as described herein.

[0020] An intake manifold 107 is disposed upstream of the first cylinder set 114. The intake manifold 107 defines an inlet 102 for receiving intake air directed into the intake manifold 107. In various embodiments, an intercooler (e.g., the intercooler 242 used in the system 200 of Fig. 3) may be disposed upstream of the intake 102 and configured to lower the temperature of the intake air to reduce, for example, knock or auto-ignition. The intake manifold 107 splits into a plurality of intake conduits. The intake conduits include a first intake conduit 106a, a second intake conduit 106b, and a third intake conduit 106c (collectively referred to herein as the "first set of intake conduits 106") that feed the first cylinder 114a, the second cylinder 114b, and the third cylinder 114c. A fourth intake conduit 108 feeds the fourth cylinder 118. The fourth intake conduit 108 is separate from the intake 102, and the conduit 107 is disposed in parallel with the intake 102 and the intake manifold 107.

[0021] The first intake valve 104 is disposed upstream of the first cylinder set 114. The first intake valve 104 may include a valve (e.g., a throttle valve), variable valve timing, or other delivery mechanism configured to meter airflow to the cylinders 114. A first set of fuel metering devices 141 is operatively coupled to the first cylinder set 114 to introduce fuel therein. Furthermore, a fourth fuel metering device 144 is operatively coupled to the fourth cylinder set 118 to introduce fuel therein. The first set of fuel metering devices 141 or the fourth fuel metering device 144 may include a carburetor, a port injector, a directional fuel injector, or other delivery mechanism configured to meter fuel (e.g., gasoline or an air / fuel mixture) to the first cylinder set 114 and the fourth cylinder 118.

[0022] Additionally, a first set of ignition devices 146 may be operatively connected to the first set of cylinders 114, and a fourth fuel ignition device 148 is operatively coupled to the fourth cylinder 118 and configured to selectively ignite the air / fuel mixture introduced therein. The first set of ignition devices 146 or the fourth fuel ignition device 148 may include spark ignition, laser ignition, or various forms of compression ignition to initiate combustion in the cylinders 114 and the fourth cylinder 118. In various embodiments, a physical ignition device may not be present, for example, in compression-ignited combustion configurations.

[0023] More specifically, the first intake valve 104 meters the air to the extent that a combustible mixture for ultra-lean part-load conditions can be achieved for the first cylinder set 114. For example, the first intake valve provides air to the first cylinder set 114 at a first flow rate to create a combustible lean air / fuel mixture in the first set of cylinders 114 of a plurality of cylinders. The air flowing into the first cylinder set 114 at the first flow rate mixes with the fuel contained therein or upstream of the first cylinder set 114 to create a lean air / fuel mixture therein. In certain embodiments, the lean air / fuel mixture has an equivalence ratio that has an upper limit defined by the reductant that can be created in the fourth cylinder 118.Further, the first cylinder set 114 operates at a first compression ratio, which may be higher than a second compression ratio of the fourth cylinder 118 (or otherwise, a second cylinder set, as described herein). For example, the first compression ratio may be in the range of 12 to 15, and the second compression ratio may be in the range of 8 to 11. However, the ranges for the first and second compression ratios may vary.

[0024] The first intake valve 104 controls the first air flow rate metered into the first cylinder set 114 to prevent ultra-lean part-load conditions in the first cylinder set 114, which can result in an uncombustible air / fuel mixture. The first cylinder set 114 operates constantly under lean conditions regardless of the engine load 110.

[0025] The second intake valve 109 is disposed upstream of the fourth cylinder 118 and parallel to the first intake valve 104, for example, in the fourth intake passage 108, and meters air to provide a rich air / fuel mixture to the fourth cylinder 118 regardless of the engine load 110. For example, the second intake valve 109 provides air to the fourth cylinder 118 at a second flow rate to create a combustible rich air / fuel mixture in the fourth cylinder 118.

[0026] Fig. 1 shows the second intake valve 109 arranged parallel to the first intake valve 104, however, in other embodiments, the second intake valve 109 may be arranged downstream of the first intake valve 104. In such embodiments, the fourth intake conduit 108 may be fluidly coupled to the intake manifold 107 to receive a portion of the intake air introduced into the intake manifold 107. For example, in various embodiments, the first intake valve 104 may be omitted when a stratified air / fuel mixture is introduced directly into the first cylinder set 114. For example, the first intake valve 104 may be omitted to meter air into the first cylinder set 114 through optimized downstream injection, conventional diesel combustion, variable valve lift, or another combustion system capable of operating at extremely lean, unthrottled conditions or mechanisms other than a throttle.

[0027] The second intake valve 109 may also include a valve (e.g., a throttle valve), variable valve timing, or other delivery mechanism configured to meter airflow to the cylinders 118. The fuel metering device 144 may include a carburetor, a port fuel injector, a direct fuel injector, or other delivery mechanism configured to supply fuel (e.g., gasoline, diesel, compressed natural gas (CNG), ethanol, liquefied petroleum gas (LPG), or mixtures thereof) or an air / fuel mixture to supply the fourth cylinder 118 with a predetermined amount of fuel.

[0028] In some embodiments, the same fuel (e.g., gasoline, diesel, compressed natural gas (CNG), ethanol, liquefied natural gas (LPG), or mixtures thereof) is provided to the first cylinder set 114 and the fourth cylinder 118. In other embodiments, the first cylinder set 114 is supplied with a first fuel (e.g., diesel) and the fourth cylinder 118 is supplied with a second fuel (e.g., gasoline, diesel, compressed natural gas (CNG), ethanol, liquefied natural gas (LPG), or mixtures thereof) to produce a desired ratio between the NOx produced in the first cylinder set 114 and the ammonia produced in the ammonia-producing catalyst 122 as described herein (e.g., NOx / ammonia ratio of 1).

[0029] In particular, the second intake valve 109 provides a second air flow rate into the fourth cylinder 118 such that the fourth cylinder 118 has a rich air / fuel mixture, i.e., an air / fuel mixture with a fuel / air equivalence ratio greater than 1.0. In certain embodiments, the rich air / fuel mixture has an equivalence ratio in the range of 1.0 to 1.1 (e.g., 1.03). Further, the fourth cylinder 118 is operated at a second compression ratio that is different from the first compression ratio and, for example, in the range of 8 to 11. This enables improved combustion phasing relative to the baseline scenario, which increases engine NOx and therefore ammonia produced by the ammonia-generating catalyst 122.The second intake valve 109 always delivers a rich air / fuel mixture to the fourth cylinder 118, so that the fourth cylinder 118 always operates under rich conditions regardless of the engine load 110. The use of the first intake valve 104 and the second intake valve 109 decouples the mass flow rate of the first cylinder set 114 from that of the fourth cylinder 118, or otherwise from that of the second cylinder set.

[0030] Fig. 1 shows the engine 110 with four cylinders such that the first set of cylinders 114 operates under lean conditions, while the remaining fourth cylinder 118 operates under rich conditions. It should be noted that the engine 110 may include any number of cylinders, for example, 6, 8, 10, 12, or even more. Any number of cylinders may be configured to run with a lean air / fuel mixture and a rich air / fuel mixture. For example, in other embodiments, the system 100 may include six cylinders. Four of the six cylinders may be configured to operate with the lean air / fuel ratio and comprise the first set of cylinders. A fifth and a sixth cylinder may be configured to operate with the rich air / fuel mixture and comprise a second set of cylinders.In such embodiments, each cylinder of the second cylinder set may have a separate, dedicated second intake valve or a shared second intake valve. In certain embodiments, the number of cylinders included in the first cylinder set operating with the lean air / fuel mixture may be higher than the number of cylinders included in the second cylinder set operating with the rich air / fuel mixture.

[0031] In some embodiments, the engine 110 may comprise a low-temperature, dual-fuel internal combustion engine. The first cylinder set 114 operates at low combustion temperature with high efficiency and low NOx, for example, high-efficiency homogenous charge compression ignition (HCCI), gasoline compression ignition (GCI), reactivity-controlled compression ignition (RCCI), or premixed charge compression ignition (PCCI). In contrast, the fourth cylinder 118 or the second cylinder set operates using any fuel, for example, CNG, gasoline, and ethanol, or under rich conditions, LPG for reductant generation.The lower compression ratio of the fourth cylinder 118 relative to the first set of cylinders 114 allows the fourth cylinder 118 to optimize combustion phasing, which increases combustion temperature and increases NOx production.

[0032] Furthermore, the different compression ratios of the first cylinder set 114 relative to the fourth cylinder 118 enable improved efficiency, mitigating an indicated mean effective pressure (IMEP) imbalance. IMEP imbalance can occur when different cylinders of an engine operate at different compression ratios or equivalence ratios. By using the higher first compression ratio of the first cylinder set 114 relative to the second compression of the fourth cylinder 118, it is possible to limit the IMEP imbalance as well as the power density imbalance due to the inherent equivalence ratio difference.

[0033] The first cylinder 114a, the second cylinder 114b, and the third cylinder 114c together produce a first exhaust portion that is directed into the exhaust manifold 132 via a first exhaust conduit 126a, a second exhaust conduit 126b, and a third exhaust conduit 126c (collectively referred to herein as the "first set of exhaust conduits 126"). The first exhaust portion may include NOx gases, CO, and / or unburned hydrocarbons. The fourth cylinder 118 (or the second set of cylinders) produces a second exhaust portion that is directed into the exhaust manifold 132 via a fourth exhaust conduit 128. In various embodiments, a first oxidation catalyst (not shown) may be disposed downstream of the first set of cylinders 114 and configured to decompose constituents, for example, CO and unburned hydrocarbons, contained in the first exhaust portion.In other embodiments, a first oxidation catalyst (not shown) may be disposed downstream of the first cylinder set 114 and configured to convert NO to NO2 such that the NO2:NO ratio reaches a value of 1.0, enabling “fast” operation of the SKR system 152.

[0034] Because the first cylinder set 114 always operates under lean conditions, the engine 110 exhibits improved resistance to auto-ignition. This allows a higher compression ratio to be used in the first cylinder set 114 for knock-limited combustion strategies. Furthermore, the first oxidation catalyst or SKR system 152 operates under the same lean operating conditions, so improved thermal stability for stoichiometric conditions, such as the SKR catalyst included in the SKR system 152, is not necessary.

[0035] An ammonia-generating catalyst 122 or other reductant-generating catalyst is disposed downstream of the fourth cylinder 118 (or the second set of cylinders) such that the second exhaust portion is passed through the ammonia-generating catalyst 122. The ammonia-generating catalyst 122 may, for example, be disposed in the fourth exhaust conduit 128. The ammonia-generating catalyst 122 may include a three-way catalyst configured to partially decompose CO (e.g., CO to carbon dioxide), unburned hydrocarbons (e.g., partially decomposing unburned hydrocarbons into carbon dioxide and water), and completely decomposing the NOx gases contained in the second exhaust portion with high selectivity to ammonia.

[0036] Because the fourth fluid conduit 128 is fluidly isolated from the first set of exhaust conduits 126, the first exhaust portion bypasses the ammonia-generating catalyst 122. In other words, only the second exhaust portion flows through the ammonia-generating catalyst 122 to produce ammonia, while the first exhaust portion does not flow through the ammonia-generating catalyst 122, so that the rich exhaust gas in the fourth fluid conduit 128 converts the engine NOx to ammonia, and an overall lean exhaust mixture is expelled from the exhaust manifold 132. The first exhaust portion and the second exhaust portion, which includes ammonia produced as the second exhaust portion flows through the ammonia-generating catalyst 122, are combined in the exhaust manifold 132. In various embodiments, the ratio of an amount of NOx gases contained in the first exhaust portion and the amount of ammonia in the second exhaust portion is 1 or approximately 1 (e.g.in the range of 0.9 to 1.1). This balanced ratio of NOx gases from the NOx amount to the ammonia amount enables efficient decomposition of the NOx gases contained in the exhaust gas using the SKR system 152 described herein.

[0037] The SCR system 152 is fluidly coupled to the exhaust manifold 132 after the first set of exhaust conduits 126 and the fourth exhaust conduit 128. The SCR system 152 includes at least one catalyst disposed within the internal volume formed by the housing of the SCR system 152. The catalyst is formulated to selectively reduce exhaust gas components, such as NOx trapped in the exhaust, in the presence of an exhaust reductant. The ammonia contained in the second exhaust portion serves as a reductant for the NOx gases contained in the first exhaust portion, thereby avoiding the use of a separate reductant. Furthermore, the balanced ratio (e.g., in the range of 0.9 to 1.1) of the amount of NOx gas to the amount of ammonia contained in the exhaust entering the SCR system 152 improves the efficiency of the SCR system 152.

[0038] Any suitable catalyst may be used, such as platinum, palladium, rhodium, cerium, iron, manganese, copper, or vanadium-based catalysts (including combinations thereof). The catalyst may be disposed on a suitable substrate, such as a ceramic (e.g., cordierite) or metallic (e.g., kanthal) monolith core, which may, for example, have a honeycomb structure. A washcoat (intermediate layer) may also be used as a support material for the catalyst. Such washcoat materials may include, for example, alumina, titania, silica, any other suitable washcoat material, or a combination thereof. The exhaust gas may flow over and around the catalyst in such a way that, if ammonia is present, any NOx gases trapped in the exhaust gas are further reduced, resulting in an exhaust gas substantially free of carbon monoxide and NOx gases.

[0039] Thus, the system 100 enables the first cylinder set 114 to operate at a constant lean air / fuel ratio regardless of the operating conditions of the engine 110. Since the first cylinder set 114 never operates with a rich air / fuel mixture, this allows the compression ratio to be increased due to greater resistance to auto-ignition. This improves engine power and also expands the operating range of the engine 110. Operating the dedicated fourth cylinder 118 (or a second cylinder set, which may be fewer in number than the first cylinder set 114) during rich conditions supplies ammonia via the ammonia-generating catalyst 122 to facilitate the reduction of the NOx gases contributed by the first exhaust portion produced by the first cylinder set 114. The balanced ratio of the amount of NOx gases to the amount of ammonia gas (e.g.,1) facilitates efficient reduction of NOx gases by the SKR system 152, enabling the system 100 to meet stringent emissions requirements.

[0040] The oxidation catalyst 160 (e.g., a second oxidation catalyst) may be disposed downstream of the SCR system 152. In some embodiments, the oxidation catalyst 160 is configured to reduce the CO contained in the exhaust and / or unburned hydrocarbons remaining after the SCR. In other embodiments, the oxidation catalyst 160 may be configured to decompose any residual ammonia contained in the exhaust after it has passed through the SCR system 152 (e.g., by including an ammonia slip catalyst).

[0041] The controller 170 may be communicatively coupled to each of the first intake doors 104 and the second intake doors 109, the first set of fuel metering devices 141, and the fourth fuel metering device 144 and configured to control the operation thereof. In some embodiments, a first set of igniters 146 may be operatively connected to each of the first cylinder sets 114, and a fourth fuel igniter 148 is operatively coupled to the fourth cylinder 118 and configured to selectively ignite the air / fuel mixture introduced therein. In such embodiments, the controller 170 may also be communicatively coupled to the fuel igniters 146 and 148 to selectively activate them and combust the air / fuel mixture within the first cylinder set 114 and the fourth cylinder 118.

[0042] The controller 170 is communicatively coupled to each of the first intake valves 104 and the second intake valves 109, the first set of fuel metering devices 141 and the fourth fuel metering device 144, the first set of fuel igniters 146, and the fourth fuel igniter 148. The controller 170 is further communicatively coupled to an ammonia sensor 121 and an oxygen sensor 123 located downstream of the fourth cylinder 118 and a NOx sensor 127 located downstream of the first cylinder set 114.

[0043] The controller 170 is configured to command the first intake valve 104 to meter airflow to the first cylinder set 114 under ultra-lean conditions to achieve improved combustion stability. In some embodiments, the first intake valve 104 may be omitted when incorporating advanced technologies, such as stratified spray-guided direct injection, to enable stable combustion of ultra-lean mixtures. For example, the first intake valve 104 may be replaced with variable valve actuation or other technology that can meter relative airflow and / or improve combustion stability under ultra-lean conditions. The first intake valve 104 may also be omitted when employing combustion strategies that have inherent stability under ultra-lean conditions (e.g., when conventional diesel combustion is employed).

[0044] The controller 170 is configured to receive a NOx output signal from the first NOx sensor 127 (e.g., a physical sensor or a virtual NOx sensor) indicative of the amount of NOx, for example, a molar NOx flow rate, flowing into the first set of cylinders 114. The NOx output signal is used to control the fuel metering devices 141 / 144 and / or the igniters 146 / 148, for example, to control the NOx exhaust levels (e.g., the molar NOx flow rate) in the first set of exhaust conduits 126.

[0045] The controller 170 is also configured to receive an ammonia output signal from the ammonia sensor 121 (e.g., a physical sensor or a virtual ammonia sensor) and command the second intake valve 109 to meter airflow to the fourth cylinder 118 to control the molar ammonia flow rate from the ammonia-generating catalyst 122. For example, the ammonia sensor 121 is used as an input to the fuel metering device 144 in the fourth cylinder 118. The fuel metering device 144 and / or the fuel igniter 148 are used in conjunction with the intake valve 109 and an oxygen sensor 123 to achieve the optimal combustion phasing, mass air flow, and air / fuel ratio to produce the NOx to be converted via the ammonia-generating catalyst 122.Further, the controller 170 may use an output signal from the oxygen sensor 123 to control the equivalence ratio of the fourth cylinder 118. Furthermore, the torque output for the first set of cylinders 114 is controlled based on a fuel demand to operate under lean conditions, and the torque output of the fourth cylinder 118 is controlled based on an air flow rate, as is common for stoichiometric engines, to operate the fourth cylinder 118 under rich conditions.

[0046] Further, based on the output NOx signal and the ammonia output signal, the controller 170 regulates the relative air mass flow rate through the first intake door 104 and the second intake door 109 such that the molar flow rate of ammonia produced in the ammonia-generating catalyst 122 matches the molar NOx flow rate in the first set of exhaust conduits 126. For example, the controller 170 may control the air flow rate through the first intake door 104 and the second intake door 109 such that the ratio between the molar NOx flow rate and the molar ammonia flow rate is 1.

[0047] In various embodiments, the controller 170 may be included in a control circuit. For example, Fig. 2 is a schematic block diagram of a control circuit 171 including the controller 170, according to one embodiment. The controller 170 may include a processor 172, a memory element 174 or other computer-readable medium, a transceiver 178, and optionally a sensor 176. It should be understood that the controller 170 illustrates only one embodiment of the controller 170, and any other controller capable of performing the tasks described herein may be used.

[0048] Processor 172 may comprise a microprocessor, a programmable logic controller (PLC), an ASIC, or other suitable processor. Processor 172 communicates with memory 174 and is configured to execute instructions, algorithms, commands, or other programs stored in memory 174.

[0049] Memory 174 includes all of the memory or storage components discussed herein. For example, memory 174 may include the RAM and / or cache of processor 172. Memory 174 may also include one or more storage devices (e.g., hard drives, flash drives, computer-readable media, etc.) located either locally or remotely from device controller 170. Memory 174 is configured to store mapping tables, algorithms, or instructions.

[0050] For example, accumulator 174 includes a first intake valve circuit 174a configured to command first intake valve 104 to direct an air / fuel mixture at a first equivalence ratio to a first cylinder set 114 of the plurality of cylinders. Accumulator 174 also includes a second intake valve circuit 174b configured to command second intake valve 109 to direct an air / fuel mixture at a second equivalence ratio to fourth cylinder 118 (or a second cylinder set, as described herein).

[0051] The memory 174 includes a fuel metering circuit 174f configured to selectively command the fuel metering devices 141 / 144 to deliver the fuel or another air / fuel mixture to the first cylinder set 114 and the fourth cylinder 118. Furthermore, the memory 174 includes a fuel metering circuit 174g configured to selectively command the fuel metering devices 146 / 148 to deliver the fuel or another air / fuel mixture to the first cylinder set 114 and the fourth cylinder 118.

[0052] The memory 174 also includes an ammonia determination circuit 174c. The ammonia determination circuit 174c is configured to determine the molar flow rate of ammonia produced by the ammonia-producing catalyst 122, for example, using the ammonia output signal generated by the ammonia sensor 121. In addition, the memory 174 also includes a NOx determination circuit 174d configured to determine the molar flow rate of NOx produced by the first cylinder set 114, for example, using the NOx output signal generated by the NOx sensor 127.

[0053] The controller includes a NOx / ammonia ratio control circuit 174e configured to control the molar NOx flow rate produced by the first cylinder set 114 and the molar ammonia flow rate produced by the fourth cylinder 118 or, as applicable, the second cylinder set, to result in a ratio of 1. For example, the NOx / ammonia ratio control circuit 174e may interpret an existing ammonia and NOx flow rate. The NOx / ammonia ratio control circuit 174e may include lookup tables, algorithms, equations, or maps to determine air flow rates provided by the first intake door 104 and the second intake door 109, which corresponds to a NOx to ammonia molar flow rate ratio of 1.The NOx / ammonia ratio control circuit 174e instructs the first intake door circuit 174a and the second intake door circuit 174b to control the air flow to the first cylinder set 114 and the fourth cylinder 118, respectively.

[0054] The NOx / ammonia ratio control circuit 174e may also determine a fuel intake timing, a fuel quantity to be introduced, and / or an ignition timing for the first cylinder set 114 and the fourth cylinder 118, or the second cylinder set, as appropriate, that corresponds to a NOx to ammonia molar flow rate ratio of 1. For example, the NOx / ammonia ratio control circuit 174e may instruct the first dosing circuit 174f and the fuel ignition circuit 174g to control the fuel flow rate and / or quantity and ignition timing of the first cylinder set 114 and the fourth cylinder 118 accordingly.

[0055] In some embodiments, the memory 174 also includes an equivalence ratio determination circuit 174h. The equivalence ratio determination circuit 174h may be used to determine the first equivalence ratio of the first cylinder set 114 and / or the second equivalence ratio of the fourth cylinder 118 or, if applicable, the second cylinder set, for example, using an oxygen output signal generated by the oxygen sensor 123. The NOx / ammonia ratio control circuit 174e may also be configured to control the first equivalence ratio of the first cylinder set 114 such that the first equivalence ratio in the first cylinder set 114 is limited to a maximum level. This allows NOx emissions from the first cylinder set 114 to be limited so that the ammonia produced by the ammonia-generating catalyst 122 is able to fully reduce the NOx via the SKR system 152.The predetermined maximum equivalence ratio may also be used to protect the engine for knock reduction. Furthermore, the NOx / ammonia ratio control circuit 174e may also be configured to control the second equivalence ratio of the fourth cylinder 118, so that the equivalence ratio can be limited in a stoichiometric to rich range for the fourth cylinder 118 at any time. For example, the NOx / ammonia ratio control circuit 174e may be configured to interpret and use an output signal from the oxygen sensor 123 to control the equivalence ratio of the fourth cylinder 118.

[0056] The controller 170 also includes a transceiver 178 configured to generate a first activation signal for activating the first intake flap 104 and a second activation signal for activating the second intake flap 109, the fuel metering signals for activating the fuel metering devices 141 / 144, and a fuel ignition signal for activating the fuel igniters 146 / 148. The first activation signal, the second activation signal, the fuel metering signals, and / or the fuel ignition signals may comprise a voltage, current, or other electrical signal and are transmitted to the intake flap 104 and the second intake flap 109, respectively, for activation.In various embodiments, the controller 170 may also include one of a variety of sensors to replace the NOx / ammonia ratio determination circuit 174e, the NOx determination circuit 174d, and / or the ammonia determination circuit 174c to provide feedback to the intake valve 104 and 109 in addition to the fuel metering devices 141 and 144 and to the igniters 146 and 148.

[0057] Although in Fig. 1, the aftertreatment system 100 may include other sensors, such as temperature sensors, pressure sensors, and / or other sensors. The controller 170 may be communicatively coupled to one or more such sensors to receive and interpret signals from one or more of these sensors, for example, to determine the molar NOx flow rate in the first set of exhaust conduits 126 and the ammonia produced by the ammonia-generating catalyst 122.

[0058] Fig. 3 is a schematic illustration of another embodiment of a system 200 including an internal combustion engine 210 fluidly coupled to an aftertreatment system 250. The internal combustion engine 210 includes an engine cylinder block 212 having a plurality of cylinders including a first cylinder 214a, a second cylinder 214b, a third cylinder 214c (collectively referred to herein as the "first cylinder set 214"), and a fourth cylinder 218. The system 200 includes a first intake valve 204, a second intake valve 209. The aftertreatment system 250 includes an ammonia-producing catalyst 222, a first oxidation catalyst 230, an SKR system 252, and a second oxidation catalyst 260. Each of the plurality of cylinders includes a piston (not shown) for compressing an air / fuel mixture introduced therein to a predetermined compression ratio, as described herein.

[0059] An intake manifold 207 is disposed upstream of the first set of a plurality of cylinders 214. Intake air flows through an inlet 202 fluidly coupled to the intake manifold 207. A compressor 244 (e.g., included in a turbocharger subsystem) is disposed upstream of the intake manifold 207. The compressor 244 is configured to compress the intake air and provide pressurized air to the engine 210 so that power output may be increased. The compressor 244 is operatively coupled to a turbine 246 (e.g., included in the turbocharger subsystem) disposed in the flow path of an exhaust stream produced by the engine 210, as described herein. The exhaust gas flowing through the turbine 246 drives the turbine 246, which in turn drives the compressor 244. An intercooler 242 is arranged upstream of the intake manifold 207 and downstream of the compressor 244.Compressing the intake air by compressor 244 increases the temperature of the intake air, which can lead to knocking or auto-ignition. Intercooler 242 serves to reduce the temperature of the air before the intake air enters engine 210, for example, to reduce knocking or auto-ignition. In various embodiments, intercooler 242 may be excluded from system 200. Further, compressor 244 and turbine 246 may also be excluded from aftertreatment system 250.

[0060] The intake manifold 207 divides into a plurality of intake conduits. The plurality of intake conduits includes a first intake conduit 206a, a second intake conduit 206b, and a third intake conduit 206c (collectively referred to herein as the "first set of intake conduits 206") that feed the first cylinder 214a, the second cylinder 214b, and the third cylinder 214c. A fourth intake conduit 208 feeds the fourth cylinder 218. The fourth intake conduit 208 is fluidly coupled to and arranged in parallel with the intake upstream of the intake manifold 207.

[0061] The first intake valve 204 is disposed upstream of the first cylinder set 214. The first intake valve 204 may include a valve (e.g., a throttle valve), variable valve timing, or other delivery mechanism configured to meter airflow to the cylinders 214. Fuel metering into the first cylinder set 214 is accomplished using fuel delivery devices (e.g., the first set of fuel metering devices 141), such as a carburetor, port injector, direct fuel injector, or other delivery mechanism configured to deliver fuel (e.g., gasoline) to the first cylinder set 214. In particular, the first intake valve 204 provides air metering for the first cylinder set 214 so that a combustible mixture for ultra-lean conditions can be achieved.In various embodiments, the first intake valve 204 may be omitted by employing variable valve actuation or advanced combustion strategies, such as stratified spray direct injection, high-energy ignition systems, or optimized combustion systems for lean environments (e.g., conventional diesel combustion). A lean air / fuel mixture is introduced into the first set of cylinders 214, i.e., an air / fuel mixture with a fuel / air equivalence ratio of less than 1.0. In certain embodiments, the lean air / fuel mixture has an equivalence ratio equal to or less than the required equivalence ratio to produce a molar NOx flow rate from the cylinders 214 equal to the molar ammonia flow rate from the ammonia-generating catalyst 222.Furthermore, the first cylinder set 214 is operated at a first compression ratio, which may be higher than that of the fourth cylinder 218 or possibly a second cylinder set.

[0062] The first intake valve 204 meters the air such that a lean air / fuel mixture is always supplied to the first cylinder set 214, and the first cylinder set 214 operates constantly under lean conditions regardless of the engine load 210. The second intake valve 209 is arranged upstream of the first intake valve and parallel to it. The second intake valve 209 meters the air flow to the fourth cylinder 218 independently of the first cylinder set 214.

[0063] The second intake valve 209 may also include a valve (e.g., a throttle valve), variable valve timing, or other delivery mechanism configured to meter airflow. Fuel metering into the fourth cylinder set 218 is accomplished with fuel filling devices (e.g., the fourth set of fuel metering devices), for example, a carburetor, a port injector, a direct fuel injector, or other delivery mechanism configured to introduce fuel (e.g., gasoline). In particular, the second intake valve 209 meters air so that a rich mixture is always present for the fourth cylinder 218, i.e., a fuel / air equivalence ratio greater than 1.0, regardless of the load in the fourth cylinder 218. In certain embodiments, the rich air / fuel mixture has an equivalence ratio in the range of 1.0 to 1.1 (e.g., 1.03).Further, the fourth cylinder 218 is operated at a second compression ratio less than the first compression ratio to enable optimal combustion phasing without knocking for maximum NOx production in a rich environment prior to the ammonia-generating catalyst 222. In various embodiments, a controller (e.g., controller 170 or control circuit 171) may be communicatively coupled to the first intake door 204 and / or the second intake door 209 and configured to control the operation thereof, as described with respect to controller 170 in FIG. Fig. 1 and Fig. 2 described.

[0064] The first cylinder 214a, the second cylinder 214b, and the third cylinder 214c together produce a first exhaust portion that is directed into a first branch of the exhaust manifold 225 via a first exhaust conduit 226a, a second exhaust conduit 226b, and a third exhaust conduit 226c (collectively referred to herein as the "first set of exhaust conduits 226"). The first exhaust portion may include NOx gases, CO, and / or unburned hydrocarbons. A NOx sensor 227, which may include a physical NOx sensor or a virtual (e.g., computer-determined) NOx sensor, is disposed in the first branch of the exhaust manifold 225 and configured to determine an amount of NOx gas in the first exhaust portion.In various embodiments, a first oxidation catalyst 230 may be disposed in the first branch of the exhaust manifold 225 after the first cylinder set 214 and configured to decompose constituents, such as CO and unburned hydrocarbons, contained in the first exhaust portion. The first oxidation catalyst 230 may convert a portion of the NO to NO2, allowing a NO:NO2 ratio close to 1 to be produced at the exit of the catalyst 230, enabling "fast" SKR operation. The first exhaust portion then flows into the exhaust manifold 232.

[0065] The fourth cylinder 218 (or the second set of cylinders) produces a second exhaust portion that is directed into a fourth exhaust conduit 228. An ammonia-generating catalyst 222 or other reductant-generating catalyst is disposed downstream of the fourth cylinder 218 (or the second set of cylinders) such that the second exhaust portion is directed through the ammonia-generating catalyst 222. The ammonia-generating catalyst 222 may include a three-way catalyst configured to partially decompose CO (e.g., CO into carbon dioxide) and partially decompose unburned hydrocarbons (e.g., decompose unburned hydrocarbons into carbon dioxide and water), and convert the NOx gases contained in the exhaust portion into ammonia. The second exhaust gas portion, which contains ammonia produced by the ammonia-generating catalyst 222, is directed into the intake manifold via a second branch of the exhaust manifold 229.An ammonia sensor 221 (e.g., a physical or virtual ammonia sensor) and an oxygen sensor 223 are disposed in the second branch of the exhaust manifold 229 and configured to determine an amount of ammonia and oxygen in the second exhaust portion (which may be used, for example, to determine an equivalence ratio of the fourth cylinder 218).

[0066] Since the first branch of the exhaust manifold 225 and the second branch of the exhaust manifold 229 meet at the exhaust manifold 232 downstream of the ammonia-generating catalyst 222, the first exhaust gas portion bypasses the ammonia-generating catalyst 222. In other words, only the second exhaust gas portion flows through the ammonia-generating catalyst 222 to produce ammonia, while the first exhaust gas portion does not flow through the ammonia-generating catalyst 222, so that the NOx gases contained in the first exhaust gas portion have not been decomposed upon entering the exhaust manifold 232.

[0067] The first exhaust portion and the second exhaust portion, which contains ammonia generated as the second exhaust portion passes through the ammonia-generating catalyst 222, are combined in the exhaust manifold 232. In various embodiments, the ratio of an amount of NOx gases contained in the first exhaust portion to the amount of ammonia in the second exhaust portion is 1 or approximately 1 (e.g., in the range of 0.9 to 1.1). This balanced ratio of the NOx gases from the amount of NOx to the amount of ammonia enables efficient decomposition of the NOx gases contained in the exhaust using the SKR system 252 described herein. For example, the controller 170, or any other controller described herein, may monitor the molar amount of NOx determined by the NOx sensor 227 and a molar amount of ammonia determined by the ammonia sensor 221.The controller 170 may use this information to control the activation of the first intake valve 204, the second intake valve 209, the fuel metering devices, and / or the fuel igniter devices to maintain the ratio of an amount of NOx gas contained in the first exhaust portion to the amount of ammonia contained in the second exhaust portion to a value of 1.

[0068] The turbine 246 is disposed downstream of the first branch of the exhaust manifold 225 and the second branch of the exhaust manifold 229. The exhaust gas flowing through the turbine 246 rotates the turbine 246 to drive the compressor 244 so that intake air flows into the intake manifold 207, as previously described herein. The SCR system 252 is disposed downstream of the turbine 246. The SCR system 252 includes at least one catalyst positioned within the internal volume formed by the housing of the SCR system 252. The SCR system 252 may be substantially similar to the SCR system 152 described with reference to the system 100 in Fig. 1 and is therefore not described in more detail here.

[0069] Thus, regardless of the operating conditions of the engine 210, the system 200 enables the first cylinder set 214 to operate at a constant lean air / fuel ratio. Because the first cylinder set 214 never operates with a rich air / fuel mixture, the increase in compression ratio is enabled due to greater resistance to auto-ignition. This improves engine efficiency and expands the operating range of the engine 210, as described herein with respect to the system 100. In various embodiments, operating the first cylinder set 214 with a constant lean air / fuel mixture results in an overall engine efficiency increase of greater than 10%, for example, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, or 20%, including all ranges and values ​​therebetween or greater.

[0070] Operation of the first cylinder set 214 may include, among other things, conventional diesel combustion, lean-burn gasoline combustion, gasoline compression ignition (GCI), premixed charge compression ignition (PCCI), reactivity-controlled compression ignition (RCCI), homogeneous charge compression ignition (HCCI), or another highly efficient lean and relatively low NOx combustion strategy. Lower NOx combustion strategies may result in higher overall power output because the required NOx reduction potential of the rich cylinder 218 is reduced. This may decrease the ratio of rich to lean cylinders.

[0071] The fourth cylinder 218, or the second set of cylinders, may be operated relative to the first set of cylinders 214 using a different combustion strategy or using a lean-burn fuel (e.g., gasoline may run in rich cylinders while conventional diesel runs in lean cylinders). Fuel used in the rich cylinder 218 may include compressed natural gas, gasoline, ethanol, liquefied natural gas, or another fuel and combustion strategy that may result in a rich exhaust mixture whose NOx is converted to ammonia in the ammonia-generating catalyst 222.

[0072] The compression ratio of the fourth cylinder is limited by the auto-ignition characteristics of the fuel used. The compression ratio is configured such that the combustion phasing is optimized to produce high engine NOx for the fourth cylinder 218 during rich operation so that the maximum NOx reduction potential of the fourth cylinder 218 can be achieved. A NOx sensor 253 is disposed downstream of the SCR system 252 and configured to meter the amount of NOx in the exhaust gas from the SCR system 252. The second oxidation catalyst 260 (e.g., a second oxidation catalyst) is disposed downstream of the SCR system 252. In some embodiments, the second catalyst 260 is configured to decompose the CO and / or unburned hydrocarbons contained in the exhaust gas.In other embodiments, the oxidation catalyst 260 may be configured to decompose any residual ammonia contained in the exhaust gas after it has passed through the SKR system 252 (e.g., by including an ammonia slip catalyst).

[0073] Exhaust gas recirculation can be used in various forms and engine configurations such that EGR is introduced for the lean cylinders 214 but not for the rich cylinders 218. This method of operation may have minor effects on lean cylinder efficiency, but will significantly reduce lean cylinder engine NOx, allowing for an extended load range and / or a reduced rich-to-lean cylinder ratio.

[0074] Fig. For example, Figure 4 is a schematic representation of another embodiment of a system 500 including an internal combustion engine 510 fluidly coupled to an aftertreatment system 550. The internal combustion engine 510 includes an engine cylinder block 512 having a plurality of cylinders including a first cylinder 514a, a second cylinder 514b, a third cylinder 514c (collectively referred to herein as the "first cylinder set 514"), and a fourth cylinder 518. The engine 510, and thereby the first cylinder set 514 and the fourth cylinder 518 included therein, may be substantially similar in structure and function to the engine 210 or 110 described herein and, therefore, will not be described in further detail here.

[0075] The system 500 includes a first intake door 504 and a second intake door 509, which are substantially similar to the first intake door 104 / 204 and the second intake door 109 / 209 described above. The aftertreatment system 550 also includes an ammonia-generating catalyst 522, a first oxidation catalyst 530, an SCR system 552, and a second oxidation catalyst 560, which are substantially similar to the ammonia-generating catalyst 122 / 222, the first oxidation catalyst 230, the SCR system 152 / 252, and the second oxidation catalyst 160 / 260 previously described herein. Although not shown, in some embodiments, the system 500 may also include an intercooler (e.g., the intercooler 242), a compressor (e.g., the compressor 244), and / or the turbine (e.g., the turbine 246), as in the aftertreatment system 200 of Fig. 3 and described herein.

[0076] An intake manifold 507 is disposed upstream of the first cylinder set 541 of a plurality of cylinders. Intake air flows via an intake 502 fluidly coupled to the intake manifold 507. The intake manifold 507 divides into a plurality of intake conduits. The plurality of intake conduits includes a first intake conduit 506a, a second intake conduit 506b, and a third intake conduit 506c (collectively referred to herein as the "first set of intake conduits 506") that feed the first cylinder 514a, the second cylinder 514b, and the third cylinder 514c. A fourth intake conduit 508 feeds the fourth cylinder 518. The fourth intake conduit 508 is fluidly coupled to and arranged in parallel with the intake upstream of the intake manifold 507.

[0077] The first intake valve 504 is disposed upstream of the first cylinder set 514. The second intake valve 509 is disposed upstream of and parallel to the first intake valve 504. The second intake valve 509 meters airflow to the fourth cylinder 518 independently of the first cylinder set 514. The first cylinder 514a, the second cylinder 514b, and the third cylinder 514c together produce a first exhaust portion that is directed into a first branch of the exhaust manifold 525 via a first exhaust conduit 526a, a second exhaust conduit 526b, and a third exhaust conduit 526c (collectively referred to herein as the "first set of exhaust conduits 526"). A NOx sensor 527 is operatively coupled to the first exhaust manifold 525 to measure an amount (e.g., a molar amount of NOx gas) in the first exhaust portion.

[0078] In various embodiments, the first oxidation catalyst 530 is disposed in the first branch of the exhaust manifold 525 downstream of the first cylinder set 514. The fourth cylinder 518 (or the second cylinder set) produces a second exhaust portion that is directed into a fourth exhaust conduit 528. An ammonia-generating catalyst 522 or other reductant-generating catalyst is disposed downstream of the fourth cylinder 518 (or the second cylinder set) such that the second exhaust portion is directed through the ammonia-generating catalyst 522. An ammonia sensor 521 and an oxygen sensor 523 are disposed downstream of the ammonia-generating catalyst 522.

[0079] The aftertreatment system 500 also includes an exhaust gas recirculation (EGR) system for recirculating a portion of the first exhaust gas portion from the first branch of the exhaust manifold 525 to the intake manifold 507. The EGR system includes an EGR conduit 570 fluidly coupling the first branch of the exhaust manifold 525 to the intake manifold 507. An EGR valve 572 is disposed in the EGR conduit 570 and configured to regulate the flow of the portion of the first exhaust gas portion from the first branch of the exhaust manifold 525 to the intake manifold 507. The recirculated portion of the first exhaust gas dilutes the O2 in the intake air stream and provides inert gases to the combustion, which act as combustion heat absorbers to reduce the peak temperature in the first cylinder set 514, which operates with a lean air / fuel mixture.

[0080] In some embodiments, an aftertreatment system coupled to an engine may also include a low-pressure and high-pressure EGR loop, an intercooler, and / or a turbocharger. Fig. For example, Figure 5 is a schematic representation of another embodiment of a system 600 including an internal combustion engine 610 fluidly coupled to an aftertreatment system 650. The internal combustion engine 610 includes an engine cylinder block 612 having a plurality of cylinders including a first cylinder 614a, a second cylinder 614b, a third cylinder 614c (collectively referred to herein as the "first cylinder set 614"), and a fourth cylinder 618. The engine 610, and thereby the first cylinder set 614 and the fourth cylinder 618 included therein, may be substantially similar in structure and function to the engine 110 / 210 / 510 described herein and, therefore, will not be described in further detail here.

[0081] The system 600 includes a first intake door 604 and a second intake door 609, which are substantially similar to the first intake door 104 / 204 / 504 and the second intake door 109 / 209 / 509 described above. The aftertreatment system 650 also includes an ammonia-generating catalyst 622, a first oxidation catalyst 630, an SCR system 652, and a second oxidation catalyst 660, which are substantially similar to the ammonia-generating catalyst 122 / 222 / 522, the first oxidation catalyst 230 / 530, the SCR system 152 / 252 / 552, and the second oxidation catalyst 160 / 260 / 560 previously described herein.

[0082] An intake manifold 607 is disposed upstream of the first cylinder set 614 of a plurality of cylinders. Intake air is provided through an inlet 602, which splits into a first inlet 605 fluidly coupled to the intake manifold 607 and a second inlet 603. The intake manifold 607 splits into a plurality of intake conduits. The plurality of intake conduits includes a first intake conduit 606a, a second intake conduit 606b, and a third intake conduit 606c (collectively referred to herein as the "first set of intake conduits 606") that feed the first cylinder 614a, the second cylinder 614b, and the third cylinder 614c. The first intake valve 604 is disposed in the intake manifold 607 and configured to control a first air flow rate into the first set of intake conduits 606 and thereby into the first set of cylinders 614.

[0083] The second inlet 603 is fluidly coupled to the fourth intake conduit 608 leading to the fourth cylinder 618. The fourth intake conduit 608 is fluidly coupled to the inlet upstream of the intake manifold 607 and arranged parallel thereto. The second intake flap 609 is arranged in the fourth intake conduit 608 and configured to allow a second air flow rate to flow into the fourth intake conduit 608 and thus control the fourth cylinder 608.

[0084] An intercooler 642 is disposed upstream of the intake manifold 607 and the fourth intake conduit 608 and is fluidly coupled to the first inlet 605 and the second inlet 603. The first intake flap 604 is disposed downstream of the intercooler 642, while the second intake flap 609 is disposed upstream of the fourth cylinder 618 and downstream of the intercooler 642. A turbine 646 is disposed in an exhaust manifold 632 and operatively coupled to a first compressor 644, which is coupled to a first inlet 605, and to a second compressor 643, which is operatively coupled to a second inlet 603. A first exhaust portion from the first cylinder set 614 and a second exhaust portion from the fourth cylinder 618 combine in the exhaust manifold 632 before entering the turbine 646.The combined exhaust drives the turbine 646, which operates the first compressor 644 and the second compressor 643 to compress the intake air provided to the first cylinder set 614 and the fourth cylinder 618, as described herein.

[0085] The second intake valve 609 meters airflow to the fourth cylinder 618 independently of the first cylinder set 614. The first cylinder 614a, the second cylinder 614b, and the third cylinder 614c together produce a first exhaust portion that is directed into a first branch of the exhaust manifold 625 via a first exhaust conduit 626a, a second exhaust conduit 626b, and a third exhaust conduit 626c (collectively referred to herein as the "first set of exhaust conduits 626"). A NOx sensor 627 is operatively coupled to the first branch of the exhaust manifold 625 to measure an amount (e.g., a molar amount of NOx gas) in the first exhaust portion.

[0086] In various embodiments, the first oxidation catalyst 630 is disposed in the first branch of the exhaust manifold 625 downstream of the first cylinder set 614. The fourth cylinder 618 (or the second cylinder set) produces a second exhaust portion that is directed into a fourth exhaust conduit 628. An ammonia-generating catalyst 622 or other reductant-generating catalyst is disposed downstream of the fourth cylinder 618 (or the second cylinder set) such that the second exhaust portion is directed through the ammonia-generating catalyst 622. An ammonia sensor 621 and an oxygen sensor 623 are disposed downstream of the ammonia-generating catalyst 622.

[0087] The system 600 also includes an EGR system that includes a high-pressure loop and a low-pressure loop. The high-pressure loop includes a first EGR conduit 670 fluidly coupled to the first branch of the exhaust manifold 625, which is upstream of the oxidation catalyst 630, and to the intake manifold 607, which is downstream of the first intake valve 604, and configured to direct a portion of the first high-pressure exhaust gas portion from the first branch of the exhaust manifold 625 into the intake manifold. A first EGR valve 672 is disposed in the first EGR conduit 670 to control an amount of the first high-pressure exhaust gas portion recirculated to the intake manifold 607. A high pressure EGR cooler 675 is fluidly coupled to the first EGR line 670 and configured to cool the first exhaust portion of the high pressure exhaust gas recirculated to the intake manifold 607.

[0088] The low-pressure loop includes a second EGR conduit 674 fluidly coupled to an exhaust manifold 632, located downstream of the turbine 646 and upstream of the SKR system 652, and the first inlet 605, located upstream of the first compressor 644. The second EGR conduit 674 recirculates a portion of the exhaust gas from the exhaust manifold 632, which has a lower pressure than the first exhaust portion after expansion in the turbine 646, to the first inlet 605. A second EGR valve 676 is disposed in the second EGR conduit 674 to regulate an amount of the first low-pressure exhaust portion recirculated to the first inlet 605. In addition, a low-pressure EGR cooler 677 is fluidly coupled to the second EGR conduit 674 and configured to cool an amount of the low-pressure exhaust gas recirculated to the first inlet 605.

[0089] Fig. 6 is a schematic flow diagram of an exemplary method 300 for operating an engine including a plurality of cylinders, such as engine 110, 210, 510, or 610, as described herein. The engine is fluidly coupled to an aftertreatment system, such as aftertreatment system 150, 250, 550, or 650. The acts of method 300 may be embodied in the form of instructions on a non-transitory computer-readable medium (e.g., memory 174 of controller 170 or main memory 736, read-only memory (ROM) 738, or storage device 740 embedded in computing device 730 of Fig. 7). The CRM may be encapsulated in a computing device (e.g., computing device 730) configured to execute the instructions stored on the CRM and perform the acts of method 300.

[0090] Method 300 directs a lean air / fuel mixture to a first set of a plurality of cylinders at 302. For example, limited use of the intake valve 104 / 204 / 504 / 604 in conjunction with a proper delivery strategy provides a lean air / fuel mixture for the first set of cylinders 114 / 214 / 514 / 614 of the engine 110 / 210 / 510 / 610. In various embodiments, the lean air / fuel mixture has a predetermined threshold that does not exceed the equivalence ratio such that the molar NOx flow rate of the first set of cylinders 114 / 214 / 514 / 614 does not exceed the maximum molar ammonia flow rate from the second set of cylinders 118 / 218 / 518 / 618. The first set of cylinders operates at a first compression ratio of 304 to optimize lean-burn combustion strategies such as conventional diesel, lean-burn gasoline, or other high-efficiency, low-temperature combustion strategies.

[0091] A rich air / fuel mixture is provided to a second set of cylinders 306. For example, the rich air / fuel ratio is provided to the fourth cylinder 118 / 218 / 518 / 618 or otherwise to a second set of cylinders as previously described. In various embodiments, the rich air / fuel mixture has a second equivalence ratio configured to produce a stoichiometric air / fuel mixture when NOx reduction is not needed and is adjustable to produce a rich air / fuel mixture such that ammonia production via the catalyst is maximized. The second set of cylinders is operated at a second compression ratio different from the first compression ratio at 308.The second compression ratio is limited by the fuel used in the second set of cylinders so that optimal combustion phasing for NOx production can be achieved without uncontrolled auto-ignition.

[0092] A second exhaust portion produced by the second set of cylinders is passed through an ammonia-generating catalyst of an aftertreatment system at 310. For example, the second exhaust portion produced by the fourth cylinder 118 / 218 / 518 / 618 is passed through the ammonia-generating catalyst 122 / 222 / 522 / 622 included in the aftertreatment system 150 / 250 / 550 / 650, as previously described. The ammonia-generating catalyst may include, for example, a three-way catalyst formulated to partially decompose CO and unburned hydrocarbons contained in the second exhaust portion and convert NOx gases to ammonia, as previously described herein.

[0093] The second exhaust portion is routed through at least one downstream component of the aftertreatment system at 312. For example, the second exhaust portion is routed through the SKR system 152 / 252 / 552 / 652 and / or the second oxidation catalyst 160 / 260 / 560 / 660 included in the aftertreatment system 150 / 250 / 550 / 650, as previously described. A second exhaust portion produced by the second set of cylinders is also routed through at least one component of the downstream aftertreatment system at 314. The first exhaust portion bypasses the ammonia-producing catalyst. For example, the first exhaust portion produced by the first set of cylinders 114 / 214 / 514 / 614 is routed through the first oxidation catalyst 230 / 530 / 630 or a first branch of the exhaust manifold (e.g.,the first branch of the exhaust manifold 225 / 525 / 625) to the exhaust manifold 132 / 232 / 532 / 632 and from there to the downstream SKR system 152 / 252 / 552 / 652 and / or to the second oxidation catalyst 160 / 260 / 560 / 660, as previously described. The ratio of an amount of NOx gases contained in the first exhaust portion to an amount of ammonia in the second exhaust portion may be 1 or approximately 1 (e.g., in the range of 0.9 to 1.1). The balanced ratio increases the efficiency of the SKR system 152 / 252 / 552 / 652 by reducing the NOx gases in the second exhaust portion by the ammonia, which serves as a reductant and is contained in the second exhaust portion.

[0094] In some embodiments, the controller 170, the control circuit 171, or any of the controllers or control circuits described herein may comprise a system computer of an apparatus or system that includes the aftertreatment system 100 or 200 (e.g., a vehicle, an engine, or a generator set, etc.). Fig. For example, FIG. 7 is a block diagram of a computing device 730 according to an illustrative implementation. Computing device 730 may be used to perform any of the methods or processes described herein, such as method 300. In some embodiments, controller 170 may include computing device 730. Computing device 730 includes a bus 732 or other communication component for conveying information. Computing device 730 may also include one or more processors 734 or processing circuitry coupled to the bus for processing information.

[0095] Computing device 730 also includes main memory 736, such as random access memory (RAM) or other dynamic storage device, coupled to bus 732 for storing information and instructions to be executed by processor 734. Main memory 736 may also be used to store positional information, temporary variables, or other intermediate information during instruction execution by processor 734. Computing device 730 may further include a read-only memory (ROM) 738 or other static storage device coupled to bus 732 for storing static information and instructions for processor 734. A storage device 740, such as solid-state memory, a magnetic disk, or an optical disk, is coupled to bus 732 for persistently storing information and instructions.For example, instructions for determining the first equivalence ratio and the second equivalence ratio may be stored in memory 740.

[0096] Computing device 730 may be coupled via bus 732 to a display 735, such as a liquid crystal display or an active matrix display, for displaying information to a user. An input device 742, such as a keyboard or alphanumeric keypad, may be coupled to bus 732 for communicating information and selecting commands for processor 734. In another implementation, input device 742 includes a touchscreen display 744.

[0097] According to various implementations, the processes and methods described herein may be implemented by computing device 730 in response to processor 734 executing a set of instructions contained in main memory 736 (e.g., the acts of method 300). These instructions may be read into main memory 736 from another non-transitory, computer-readable medium, such as storage device 740. Execution of the various instructions contained in main memory 736 causes computing device 730 to perform the acts described herein. One or more processors in a multiprocessor arrangement may also be employed to execute the instructions contained in main memory 736. In alternative implementations, wired circuitry may be used instead of, or in combination with, software instructions to implement the described implementations.Thus, the implementation forms are not limited to a specific combination of hardware circuitry and software.

[0098] Although an exemplary computer device in Fig. 7, the implementations described in this specification may be implemented in other types of digital electronic circuitry or in computer software, firmware, or hardware, including the structures disclosed in this specification and their structural equivalents, or in combinations of one or more elements.

[0099] Implementations described in this specification may be implemented in digital electronic circuitry or in computer software, firmware, or hardware, including the structures disclosed in this specification and their structural equivalents, or in combinations of one or more of them. The implementations described in this specification may be implemented as one or more computer programs, i.e., one or more modules of computer program instructions encoded on one or more computer storage media for execution by, or for controlling the operation of, data processing equipment. Alternatively or additionally, the program instructions may be embodied in an artificially generated propagated signal, e.g., aa machine-generated electrical, optical, or electromagnetic signal generated to encode information for transmission to a suitable receiver device for execution by a data processing apparatus. A computer storage medium may be or include any of the following: a computer-readable storage device, a computer-readable storage substrate, a serial or dynamic random access memory or device, or a combination of one or more thereof. Further, although a computer storage medium is not a transmitted signal, a computer storage medium may be a source or destination of computer program instructions encoded in a man-made propagated signal. The computer storage medium may also be or include one or more separate components or media (e.g., multiple CDs, disks, or other storage devices).Accordingly, the computer storage medium is both tangible and non-volatile.

[0100] The operations described in this specification may be performed by a data processing device with data stored on one or more computer-readable storage devices or received from other sources. The term "data processing device" or "computing device" encompasses all types of devices, apparatus, and machines for processing data, including, for example, by a programmable processor, a computer, a system on a chip, one or more of them, or combinations of the foregoing. The device may include special-purpose logic circuitry, such as an FPGA (General Purpose Integrated Circuit) or an ASIC (Application Specific Integrated Circuit). The device may also include, in addition to hardware, code that creates an execution environment for the computer program in question, such asCode representing processor firmware, a protocol stack, a database management system, an operating system, a cross-platform runtime environment, a virtual machine, or a combination of one or more of these. The device and execution environment can implement various computing model infrastructures, such as web services, distributed computing, and spatially distributed computing infrastructures.

[0101] A computer program (also known as a program, software, software application, script, or code) can be written in any form of programming language, including compiled or interpreted languages, declarative or procedural languages, and it can be deployed in any form, including as a stand-alone program or as a module, component, subroutine, object, or other unit suitable for use in a computing environment. A computer program may, but is not necessarily, equivalent to a file in a file system. A program may be stored in a section of a file containing other programs or data (e.g., one or more scripts stored in a markup language document), in a single dedicated file for the program in question, or in multiple coordinated files (e.g., files storing one or more modules, subroutines, or sections of code).A computer program may be deployed to run on one or more computers located at one location or distributed over several locations and interconnected by a data transmission network.

[0102] Processors suitable for executing a computer program include, for example, both general-purpose and special-purpose microprocessors, and one or more processors of any type of digital computer. Generally, a processor receives instructions and data from read-only memory or random-access memory, or both. The essential elements of a computer are a processor for performing operations according to instructions and one or more memory devices for storing instructions and data. Generally, a computer also includes one or more mass storage devices for storing data, or is operatively coupled to receive or transmit data, or both, such as magnetic, magneto-optical disks, or optical disks. However, a computer is not required to include these devices.Devices suitable for storing computer program instructions and data include all forms of non-volatile memory, media, and storage devices, including, for example, semiconductor memory devices, e.g., EPROM, EEPROM, and flash memory devices; magnetic disks, e.g., internal hard disks or removable disks; magneto-optical disks; and CD-ROM and DVD-ROM disks. The processor and memory may be supplemented by, or integrated with, special-purpose logic circuitry.

[0103] It should be noted that the term "example" as used herein to describe various embodiments is intended to indicate that such embodiments are possible examples, representations, and / or illustrations of possible embodiments (and that such a term is not necessarily intended to imply that such embodiments are exceptional or excellent examples).

[0104] As used herein, the term "coupled" and similar terms means the direct or indirect connection of two elements to one another. This connection may be stationary (e.g., permanent) or movable (e.g., removable or detachable). This connection may be achieved by the two elements, or the two elements and any other intermediate elements, being integrally formed as a unitary body, or by the two elements, or the two elements and any other intermediate elements, being fastened to one another.

[0105] It should be understood that the structure and arrangement of the various exemplary embodiments are for illustrative purposes only. Although only a few embodiments have been described in detail in this disclosure, those skilled in the art will readily appreciate upon reading this disclosure that many modifications are possible (e.g., variations in sizes, dimensions, structures, shapes, and portions 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 described herein. In addition, it is understood that features from one embodiment disclosed herein may be combined with features from other embodiments disclosed herein, as would be known to one skilled in the art.Further substitutions, modifications, changes and omissions may also be made in the construction, operating conditions and arrangement of the various exemplary embodiments without departing from the scope of the present invention.

[0106] Although this specification contains many specific implementation details, these should not be considered limitations on the scope of all inventions or the claims, but rather as descriptions of features specific to particular embodiments of particular inventions. Certain features described in this specification in the context of separate implementations may also be implemented in combination in a single implementation. Conversely, various features described in the context of a single implementation may also be implemented in multiple implementations, separately or in any suitable subcombination.In addition, although the foregoing features may be described as functioning in certain combinations and may also be initially claimed as such, in some cases one or more features from a claimed combination may be singled out from the combination, and the claimed combination may be directed to a subcombination or variation of a subcombination.

Claims

[1] A system (500; 600) for use with an engine (510; 610) having a first cylinder (514; 614) and a second cylinder (518; 618), the system comprising: a first inlet (502; 602) configured to receive air; an intake manifold (507; 607) configured to receive the air from the first intake (502; 602) and supply the air to the first cylinder and the second cylinder; an exhaust manifold (532; 632) configured to receive exhaust gases from the first cylinder and the second cylinder, the exhaust manifold comprising: a first exhaust outlet conduit (526; 626) configured to receive the exhaust gas from the first cylinder; and a second exhaust outlet conduit (528; 628) configured to receive the exhaust gas from the second cylinder; a first catalyst (522; 622) disposed along the second exhaust outlet conduit (528; 628) and configured to receive the exhaust gas from the second cylinder and produce ammonia; a first exhaust gas recirculation line (570; 670) connected to the first exhaust outlet line (526; 626) and the intake manifold (507; 607) and configured to selectively supply the exhaust gas from the first exhaust outlet line to the intake manifold; a first compressor (244; 644) configured to receive the air from the first inlet and compress the air before supplying the air to the intake manifold (507; 607); and a turbine (246; 646) configured to receive the exhaust gas from the first exhaust outlet conduit (526; 626) and the exhaust gas from the second exhaust outlet conduit (528; 628); a second inlet (603) coupled to the first inlet (602) upstream of the first compressor (644) and configured to receive the air; and a second compressor (643) configured to receive the air from the second inlet and compress the air before supplying the air to the intake manifold (507; 607), the second compressor being operatively connected to the first compressor; wherein the second exhaust outlet conduit (528; 628) is isolated from the first exhaust outlet conduit upstream of the first catalyst (522; 622) and is connected to the first exhaust outlet conduit downstream of the first catalyst; wherein the intake manifold (507; 607) comprises: a first intake manifold conduit (506; 606) configured to receive the air from the first compressor and supply the air to the first cylinder; and a second intake manifold conduit (508; 608) configured to receive the air from the second compressor and supply the air to the second cylinder; and wherein the first exhaust gas recirculation line (570; 670) is connected to the first intake manifold line (506; 606). [2] The system of claim 1, further comprising: a second catalyst (560) disposed along the first exhaust outlet conduit (526) and configured to receive the exhaust gas from the first cylinder and oxidize the exhaust gas; wherein the first exhaust outlet conduit (526) is isolated from the second exhaust outlet conduit (528) upstream of the second catalyst and is connected to the second exhaust outlet conduit downstream of the second catalyst. [3] The system of claim 1 or 2, wherein the engine is configured such that during operation of the engine, the first cylinder is operated at a first compression ratio and the second cylinder is operated at a second compression ratio different from the first compression ratio. [4] The system of any one of claims 1 to 3, further comprising a first intake flap (504); wherein the first intake flap (504) is coupled to the first intake manifold conduit (506); and wherein the first intake manifold conduit is coupled to the second intake manifold conduit upstream of the first intake valve and is isolated from the second intake manifold conduit downstream of the first intake valve [5] The system of claim 4, further comprising a second intake valve (509), the second intake valve being connected to the second intake manifold conduit (508); wherein the second intake manifold conduit (508) is coupled to the first intake manifold conduit upstream of the second intake valve and is isolated from the first intake manifold conduit downstream of the second intake valve. [6] System according to claim 5, wherein the first intake valve (504) is configured to supply the air to the first cylinder (514) at a first flow rate to produce a combustible lean air / fuel mixture in the first cylinder; and the second intake valve (509) is configured to supply the air to the second cylinder (518) at a second flow rate to produce a rich air / fuel mixture in the second cylinder. [7] The system of claim 5, further comprising: an intercooler disposed upstream of the intake manifold (507) and configured to receive the air from the first inlet (502) at a first temperature and supply the air to the intake manifold (507) at a second temperature lower than the first temperature; a selective catalytic reduction (SCR) system (552) disposed downstream of the exhaust manifold (532) and configured to receive the exhaust gas from the exhaust manifold; a second catalyst (530) disposed along the first exhaust outlet conduit and configured to receive the exhaust gas from the first cylinder and oxidize the exhaust gas; and a third catalyst (560) disposed downstream of the SKR system and configured to receive the exhaust gas from the SKR system and oxidize the exhaust gas; wherein the first exhaust outlet conduit (526) is isolated from the second exhaust outlet conduit (528) upstream of the second catalyst (530) and is connected to the second exhaust outlet conduit downstream of the second catalyst. [8] The system of claim 1, further comprising a recirculation valve (572) coupled to the first recirculation conduit (570) and configured to cause the first recirculation conduit to deliver the exhaust gas to the intake manifold (507). [9] The system of claim 8, further comprising a cooler (675) disposed along the first recirculation conduit (670) upstream of the recirculation valve (672) and configured to receive the exhaust gas from the exhaust manifold at a first temperature and to supply the exhaust gas to the recirculation valve at a second temperature that is lower than the first temperature. [10] System according to claim 1, wherein the first intake manifold conduit is connected to the second intake manifold conduit; and the first return line is connected to the first intake manifold line downstream of the second intake manifold line. [11] The system of claim 10, further comprising a first intake valve (504) connected to the first intake manifold conduit (506) downstream of the second intake manifold conduit (508) and upstream of the first return conduit; wherein the first intake valve (504) is configured to supply the air to the first cylinder at a first flow rate to produce a combustible lean air / fuel mixture in the first cylinder. [12] The system of claim 1, further comprising: a second recirculation conduit (674) disposed downstream of the turbine and configured to selectively supply the exhaust gas from the turbine to the first inlet. [13] A method of operating an engine having a plurality of cylinders, the method comprising: Providing a lean air / fuel mixture to a first set of cylinders from a plurality of cylinders; Operating the first set of cylinders at a first compression ratio; Providing a rich air / fuel mixture to a second set of cylinders from a plurality of cylinders; Operating the second set of cylinders at a second compression ratio that is less than the first compression ratio; passing a portion of exhaust gas produced by the second set of cylinders through an ammonia-producing catalyst of an aftertreatment system; Passing a second exhaust gas portion through at least one component of the downstream aftertreatment system; and Passing a first exhaust portion produced by the first set of cylinders through at least one downstream aftertreatment component, wherein the first exhaust portion bypasses the ammonia-producing catalyst. [14] The method of claim 13, wherein the lean air / fuel mixture has a first equivalence ratio, the first equivalence ratio having an upper limit determined by NOx emissions from the lean air / fuel mixture, and the rich air / fuel mixture has a second equivalence ratio ranging from 1.0 to 1.

1. [15] The method of claim 13 or 14, wherein the first compression ratio is configured to provide high thermal braking efficiency of the first set of cylinders operating with the lean air / fuel mixture. [16] A method according to any one of claims 13 to 15, wherein the second compression ratio is configured to enable optimal combustion phasing of the rich air / fuel mixture used in the second set of cylinders while avoiding uncontrolled auto-ignition. [17] A controller (170) for operating an engine having a plurality of cylinders, the controller being programmed to perform the following steps: causing a lean air / fuel mixture to be supplied to a first set of cylinders of the plurality of cylinders; causing the first set of cylinders to operate at a first compression ratio; causing a rich air / fuel mixture to be supplied to a second set of cylinders of the plurality of cylinders; causing the second set of cylinders to operate at a second compression ratio that is less than the first compression ratio; causing a second portion of the exhaust gas produced by the second set of cylinders to be passed through an ammonia-producing catalyst of an aftertreatment system; Causing the second portion of the exhaust gas to be passed through at least one downstream aftertreatment component of the aftertreatment system; and Causing a first portion of the exhaust gas produced by the first group of cylinders to be passed through the at least one downstream aftertreatment component, wherein the first portion of the exhaust gas bypasses the ammonia-producing catalyst.

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