Internal combustion engine

An internal combustion engine comprises a compressor disposed in an intake system configured to compress combustion air and deliver it to cylinders of the engine. A compressor inlet assembly has a combustion air inlet, in fluid communication with, and configured to receive combustion air from the intake system. A combustion air passage extends through the assembly to an outlet located downstream of the inlet and is configured for fluid communication with the compressor. An EGR mixing conduit is disposed within the compressor inlet assembly and has an EGR inlet configured for fluid communication with, and receipt of EGR from, an EGR supply conduit. An EGR passage extends from the EGR inlet to an EGR supply annulus disposed about the combustion air inlet opening and a plurality of EGR ports extend between the EGR supply annulus and the combustion air passage for delivery of EGR thereto.

FIELD OF THE INVENTION

Exemplary embodiments of the invention relate to internal combustion engines having exhaust gas recirculation systems and, more particularly to an internal combustion engine having an engine cylinder dedicated to the production and supply of recirculated exhaust gas to another cylinder of the engine and apparatus for delivery thereto.

BACKGROUND

With increased focus on vehicle economy, automotive manufacturers are turning to smaller, lighter vehicles and unique vehicle powertrains to boost efficiency. Recirculated exhaust gas (“EGR”) is utilized in most conventional internal combustion engines to assist in the reduction of throttling losses at low loads, and to improve knock tolerance and reduce the level of oxides of nitrogen (“NOx”) in the exhaust gas. EGR is especially important as an emissions reducer in internal combustion engines that run lean of stoichiometry and are, as such, prone to emitting higher levels of NOxemissions.

One proposition that has been considered in the construction of internal combustion engine systems is to utilize one, or a plurality of cylinders as a dedicated EGR source. Specifically, in a four cylinder engine for instance, two or three of the four cylinders will run at normal air, fuel and EGR mixtures (working cylinders). The exhaust gas produced by these cylinders will exit the internal combustion engine as exhaust gas and be treated in an exhaust gas treatment system prior to its release to the atmosphere. One or two of the four cylinders is operated at customized levels of air and fuel (EGR cylinders); as may be determined by an engine controller that is in signal communication with various engine, vehicle and exhaust system sensors. The exhaust gas produced in these cylinders is transferred to the intake ports of the other cylinders to provide EGR. Such a configuration allows for richer EGR, which contains higher levels of Hydrogen, thereby improving knock resistance, fuel consumption and combustion stability while still allowing stoichiometrically combusted exhaust gas to be maintained in the exhaust gas treatment system for compatibility with the catalytic treatment devices.

A challenge is to deliver uniform volumes of EGR to the intake manifold upstream of a compressor, such as an engine driven supercharger or an exhaust driven turbocharger, to thereby promote an even distribution and mixing of the exhaust gas with combustion air for delivery of a homogeneous combustion charge to the working cylinders over a broad range of operating conditions.

SUMMARY

In an exemplary embodiment an internal combustion engine comprises a working cylinder, an EGR cylinder, an intake system for supplying combustion air to the cylinders, a first exhaust system for removing exhaust gas from the working cylinder and to the atmosphere, a second exhaust system for removing exhaust from the EGR cylinder and supplying the exhaust gas through an EGR supply conduit to the intake system, a compressor disposed in the intake system and configured to compress the combustion air and deliver it to the working cylinder and the EGR cylinder, a compressor inlet assembly having a combustion air inlet opening, in fluid communication with, and configured to receive combustion air from the intake system, a combustion air passage extending through the compressor inlet assembly to a combustion air outlet located downstream of the combustion air inlet opening and configured for fluid communication with the compressor, an EGR mixing conduit disposed within the compressor inlet assembly and having an EGR inlet configured for fluid communication with, and receipt of EGR from, the EGR supply conduit, an EGR passage extending from the EGR inlet to an EGR supply annulus disposed about the combustion air inlet opening and a plurality of EGR ports extending between the EGR supply annulus and the combustion air passage to thereby fluidly connect the EGR supply annulus therewith for delivery of EGR thereto, wherein the combustion air charge delivered to the cylinders is a combination of combustion air and EGR.

DESCRIPTION OF THE EMBODIMENTS

The invention described in various embodiments herein comprises a novel apparatus and method for the supply of exhaust gas to the cylinders of an internal combustion engine (i.e. regenerated exhaust gas “EGR”). As discussed above, EGR is useful in maintaining several performance parameters of the internal combustion engine including maintaining reduced levels of oxides of nitrogen (“NOx”) which is a regulated exhaust constituent and is more prevalent in engines that are operated on the lean side (i.e. excess oxygen) of stoichiometry. The basic premise of the invention is to provide an internal combustion engine with two configurations of cylinders; a first “working type” and a second “EGR type”. While all cylinders are operated in a manner that provides work output from the engine, the first, working type is operated at normal air/fuel ratios that deliver optimum power and appropriate exhaust emissions to an exhaust treatment system. The second, EGR type is operated in a manner that may not necessarily deliver optimum power and appropriate exhaust emissions but, instead delivers optimal EGR directly to the intake ports of the first, working type of cylinders. Mechanically, the exhaust ports of the second, EGR type of cylinders are fluidly connected to the intake system of the internal combustion engine and not directly to the exhaust treatment system. The path for the exhaust from these cylinders to the exhaust treatment system is by recirculation through the intake system and through the first, working type cylinders.

Optimization of the internal combustion engine preferably will result in a consistent, reliable supply of EGR to each working cylinder at the appropriate time for optimal performance of that working cylinder. In addition, the combustion charge entering the cylinders should be a homogeneous mixture of combustion air and recirculated exhaust gas. As should be apparent, it is contemplated that the invention is applicable to many configurations of internal combustion engines without deviating from the scope thereof. For example, a 2-cylinder engine may comprise one working cylinder and one EGR cylinder, a 3-cylinder engine may comprise two working cylinders and one EGR cylinder operating on a two stroke cycle, a 4-cylinder engine may comprise two or three working cylinders and one or two EGR cylinders, a 6-cylinder engine may comprise three working cylinders and three EGR cylinders, an 8-cylinder engine may comprise four working cylinders and four EGR cylinders, etc.

Referring now toFIG. 1, and for purposes of description only, an exemplary embodiment of the invention is directed to an in-line 4-cylinder internal combustion engine system10comprising a plurality of engine cylinders12In the embodiment illustrated, the internal combustion engine system10is an in-line internal combustion engine including four engine cylinders12, however the configuration may also include any number of cylinders as well as other configurations such as V-configured, horizontally opposed and the like, without affecting the application of the invention thereto.

Referring to the engine cylinders12in the embodiment shown, the individual cylinders are numbered cylinder #1,12A (working cylinder), cylinder #2,12B (EGR cylinder), cylinder #312C (EGR cylinder), and cylinder #4,12D (working cylinder). Combustion air18enters an intake system24through inlet26and is metered by a throttle body28in a known manner. The metered combustion air18is mixed with an exhaust gas diluent referred to generally as recirculated exhaust gas or EGR30to form a combustion charge32comprising a mixture of combustion air18and EGR30.

The combustion charge32is compressed by a compressor20,20′ which, in the exemplary embodiment shown inFIGS. 1-5is an engine driven supercharger20and inFIGS. 6-8is an exhaust driven turbocharger20′, is delivered to each of the engine cylinders12through an intake manifold34comprising a plurality of intake runners34A,34B,34C and34D corresponding to engine cylinders12A-12D, respectively. The combustion charge32is mixed with fuel in the cylinders12and is combusted therein. One or more ignition devices such as spark plugs36may be located in communication with the cylinders12and operate to ignite the fuel/air mixture therein.

In an exemplary embodiment, exhaust gas38from the combustion of fuel and combustion charge32in the working cylinders12A and12D (cylinders #1and #4) exits the cylinders through the exhaust passages40of a first exhaust manifold42. The exhaust manifold42is in fluid communication with an exhaust treatment system44that may include one or more exhaust treatment devices (ex. oxidation catalyst device, selective catalyst reduction device, particulate trap, or a combination thereof)46for the oxidation, reduction or filtering of exhaust constituents prior to the release of the exhaust gas to the atmosphere. Exhaust gas48from the combustion of fuel and combustion charge32in the EGR cylinders12B and12C (cylinders #2and #3) exits the cylinders through the exhaust passages50of a second exhaust manifold52. The exhaust manifold52is in fluid communication with EGR supply conduit54which delivers the exhaust gas as EGR30to the intake system24. An EGR cooler56may be disposed within the EGR supply conduit54to cool the exhaust gas48prior to its reintroduction into the intake system as EGR30and mixing with the combustion air18.

Referring toFIGS. 1-4, the EGR supply conduit54is configured to deliver EGR30to the intake system24adjacent to the inlet22of the compressor20. Delivery of the EGR at this location allows for maximum EGR delivery due to the low pressure conditions created at the inlet of the compressor. It is desirable to deliver the EGR30in a manner that promotes thorough mixing of the EGR with the combustion air18as the combustion charge (a mixture of EGR and combustion air) passes through and is compressed by the compressor20. To facilitate such delivery and mixing of the EGR30, a compressor inlet assembly70comprises a combustion air inlet opening72that is in fluid communication with, and receives combustion air from the intake system24. A flange member74surrounds the inlet opening72and includes means such as through-holes75for receiving bolts (not shown) or other suitable fasteners, for sealing attachment of the compressor inlet assembly70to the intake system24. A combustion charge passage73extends through the compressor inlet assembly to a combustion charge outlet76that is located downstream of the combustion air inlet opening72and is configured for fluid communication with the compressor20for delivery of the combustion charge thereto. The charge outlet76opens through a sealing face78for sealing attachment of the compressor inlet assembly70to the compressor20.

Disposed within the inlet assembly70, between the combustion air inlet opening72and the combustion charge outlet76, is an EGR mixing conduit80. In an exemplary embodiment, the EGR mixing conduit80comprises an EGR inlet82that is configured for fluid communication with, and receipt of EGR30from, the EGR supply conduit54. A flange portion84extends about the opening and is configured for sealing engagement with the EGR supply conduit54through the use of suitable fasteners (not shown). The EGR mixing conduit80extends from the EGR inlet82to an EGR supply annulus88that is disposed about the combustion air inlet opening72. A plurality of EGR ports90extend between the EGR supply annulus88and the combustion charge passage73to thereby fluidly connect the EGR supply annulus88therewith.

In an exemplary embodiment, the cylinder firing order of the internal combustion engine10may be working cylinder #1,12A, EGR cylinder #3,12C, working cylinder #4,12D and EGR cylinder #2,12B. As a result of this firing order, the cylinders supplying EGR30to the intake system24(i.e. cylinders12B and12C) fire between the combustion events of the working cylinders12A and12D thereby providing a consistent flow of EGR30to the EGR inlet82for delivery to, and mixing with, combustion air18through the EGR ports90of the EGR supply annulus88. The distribution of the EGR ports90about the combustion charge passage73assures a consistent delivery of EGR18to the combustion air18entering the compressor inlet assembly70through the combustion air inlet opening72. As such, the combustion charge32comprises a homogeneous mixture of combustion air18and EGR30when delivered to the cylinders12during operation of the internal combustion engine10.

Referring again toFIG. 1, in an exemplary embodiment, intake runners34B and34C of the intake manifold34may include one or more electronically controlled throttle bodies58A and58B respectively. The electronically controlled throttle bodies58A and58B are in signal communication with a controller100monitors various engine and exhaust system parameters and adjusts the flow of combustion charge into the EGR cylinders12B and12C to thereby adjust the composition of the combustion charge entering the EGR cylinders12B,12cwith the result that the exhaust gas48exiting the EGR cylinders is optimized for the working cylinders12A and12B.

Referring now toFIGS. 2,3and5, in an exemplary embodiment, the compressor inlet assembly70may be a cast, one piece assembly. The EGR passage86and supply annulus88of the compressor inlet assembly70may be manufactured utilizing a casting core92that results in the formation, following the casting process, of the EGR passage and the supply annulus. The EGR ports90are subsequently through-drilled93,FIG. 3, from the exterior of the compressor inlet assembly70and into the combustion air passage72. The EGR ports90may include diameters of varying dimension in order to balance the flow of exhaust gas from the supply annulus88into the combustion air passage72. Plugs94,FIG. 2, are subsequently inserted into the external openings96of the through-drilled ports93,FIG. 3, to prevent leakage of the EGR30out of the compressor inlet assembly70. As such, a low cost manufacturing process is provided.

Referring to FIGS.1and6-8, in another exemplary embodiment, the EGR supply conduit54is configured to deliver EGR30to the intake system24adjacent to the inlet22′ of the compressor20′ (in this case an exhaust driven turbocharger). Delivery of the EGR30at this location allows for maximum EGR delivery due to the low pressure conditions created at the inlet of the compressor20′. It is desirable to deliver the EGR30in a manner that promotes thorough mixing of the EGR with the combustion air18as the combustion charge32(a mixture of EGR30and combustion air18) passes through and is compressed by the compressor20′. To facilitate such delivery and mixing of the EGR30, a compressor inlet assembly70′ comprises a combustion air inlet opening72′ that is in fluid communication with, and receives combustion air from the intake system24. A flange member74′ surrounds the inlet opening72′ and is configured for sealing attachment of the compressor inlet assembly70′ to the intake system24. A combustion charge passage73′ (shown in negative inFIG. 8) extends through the compressor inlet assembly70′ to a combustion charge outlet76′ that is located downstream of the combustion air inlet opening72′ and is configured for fluid communication with the compressor20′ for delivery of the combustion charge32thereto. The air outlet76′ is configured for sealing attachment of the compressor inlet assembly70′ to the compressor20′.

Disposed within the inlet assembly70′, between the combustion air inlet opening72′ and the combustion charge outlet76′, is an EGR mixing conduit80′. In an exemplary embodiment, the EGR mixing conduit80′ comprises an EGR inlet82′ that is configured for fluid communication with, and receipt of EGR30from, the EGR supply conduit54. A flange portion84′ extends about the opening and is configured for sealing engagement with the EGR supply conduit54through the use of suitable fasteners (not shown). The EGR mixing conduit80′ extends from the EGR inlet82′ to an EGR supply annulus88′ that is disposed about the combustion air inlet opening72′. A plurality of EGR ports90′ extend between the EGR supply annulus88′ and the combustion air passage73′ to thereby fluidly connect the EGR supply annulus therewith. The EGR ports90′ may include diameters of varying dimension in order to balance the flow of exhaust gas from the supply annulus88′ into the combustion air inlet opening72′.

The distribution of the EGR ports90′ about the combustion air passage73′ assures a consistent delivery of EGR30to the combustion air18entering the compressor inlet assembly70′ through the combustion air inlet opening72′. As such, the combustion charge32comprises a homogeneous mixture of combustion air18and EGR30when delivered to the cylinders12during operation of the internal combustion engine10.