Patent Application
20110203270
The present invention relates to an internal combustion engine system comprising an exhaust gas recirculation assembly and to a particulate filter unit for such an internal combustion engine system.
Internal combustion engines produce hazardous products which are carried by the exhaust gases released into the atmosphere. Such hazardous products usually comprise some nitrogen oxides known as NOx, e.g. nitrogen monoxide, carbon monoxide (CO), hydrocarbons (HC) and, especially within a Diesel engine, various particulate products. It is known to use an exhaust gas recirculation (EGR) assembly in order to reduce the amount of nitrogen oxides produced by internal combustion engine.
In the case of turbocharged internal combustion engines, the EGR assembly may be arranged in various manners with respect to a turbocharger of the internal combustion engine system. In a so-called long-route EGR assembly, also called low-pressure loop EGR assembly, e.g. the one described in WO-A-2007/140148, the EGR assembly inlet is connected downstream of a turbine outlet of the turbocharger and a recirculation outlet of the assembly is connected upstream of a compressor inlet of the turbocharger to allow recirculation of a portion of the turbine exhaust gases towards the compressor. A flow divider is normally arranged at the EGR assembly inlet, in order to divert a portion of the exhaust gases away from the exhaust outlet and guide it towards the recirculation outlet, while another portion goes straight to the exhaust outlet to be released into the atmosphere.
As in many Diesel engine systems, the system of WO-A-2007/140148 also comprises a particulate filter unit, like a Diesel particulate filter (DPF), intended to decrease the amount of particulate products, for instance soot and other organic residues. The DPF is here installed so as to remove the particles both for the exhaust gases which are recirculated and for the exhaust gases which flow to the atmosphere.
Besides, Diesel engine systems now usually comprise a converter unit intended to decrease the amount of some environmentally hazardous gases, like nitrogen monoxide (NO) in the exhaust gases. Such a converter unit is may comprise a nitrogen oxides (NOx) trap and/or a catalyst, like a selective catalyst reduction (SCR) system. It is known that a converter unit is more efficient when operating at a specified range of temperatures. Therefore, in a long-route EGR assembly, it may be preferable to place the converter unit upstream of the particulate filter unit. Moreover, where the converter unit consists of an SCR system, liquid urea is injected upstream of the SCR system, in particular for reduction of nitrogen monoxide (NO) into neutral nitrogen (N2). In WO-A-2007/140148, a mobile flap is provided downstream of the EGR assembly inlet to increase the pressure at said inlet, in order to increase the part or portion of the exhaust gases flowing into the recirculation outlet.
It is desirable to provide an internal combustion engine system, comprising a turbocharged internal combustion engine, an intake line, an exhaust line, a turbocharger having a turbine located in said exhaust line and a compressor located in said intake line, and an exhaust gas recirculation assembly, for recirculating towards said intake line a part of the exhaust gases which flow out of said turbine, said exhaust gas recirculation assembly comprising: an exhaust gas recirculation assembly inlet connected to said exhaust line downstream of said turbine , so as to collect said part of the exhaust gases, an exhaust gas recirculation assembly outlet connected to said intake line upstream of said compressor so as to allow said part of the exhaust gases towards said intake line and said compressor, a particulate filter unit, for decreasing the amount of particulate products within said exhaust gases.
Said internal combustion engine system further comprises a converter unit, for decreasing at least the amount of nitrogen oxides within said exhaust gases, said converter unit being fluidically arranged in said exhaust line downstream of said turbine.
Said particulate filter unit comprises a first particulate filter component fluidically arranged in said exhaust line downstream of said converter unit, said first particulate filter component defining a first flow path. Said particulate filter unit comprises a second particulate filter component fluidically arranged in said exhaust gas recirculation assembly, downstream of said exhaust gas recirculation assembly inlet and upstream of said exhaust gas recirculation assembly outlet, said second particulate filter component defining a second flow path. Said first particulate filter component and said second particulate filter component are thermally connected, and said first flow path and said second flow path are separate.
According to other advantageous but optional features of the present invention, considered on their own or in any technically possible combinations:
said internal combustion engine system further comprises a recirculation valve, for controlling the recirculation flow flowing into said exhaust gas recirculation assembly;
said first particulate filter component and said second particulate filter component are adjacent;
a gas-tight partition is arranged between said first particulate filter component and said second particulate filter component, so as to allow heat transfer between said first particulate filter component and said second particulate filter component;
one of said first and second particulate filter components encases the other one of said first and second particulate filter components;
said first particulate filter component laterally encases at least part of said second particulate filter component;
said first and second particulate filter components are arranged in a coaxial manner;
said gas-tight partition is of a general cylindrical form and wherein said particulate filter unit comprises an outer cylindrical wall, said first particulate filter component extending between said gas-tight partition and said outer cylindrical wall, and said second particulate filter component extending within said gas-tight partition;
said first particulate filter component fully laterally encases said second particulate filter component;
said gas-tight partition is made of a material having a thermal conductivity higher than 25 W·m−1·K−1;
at least one heating device is arranged either near or within said first particulate filter component, for promoting the regeneration of said first particulate filter component;
said heating device comprises a fuel injector for injecting fuel in said exhaust line downstream of said converter unit;
a supply duct is arranged to supply a deoxidizing agent to said converter unit, said supply duct being connected to said exhaust line upstream of said converter unit; and
said internal combustion engine system further comprises an oxidation catalyst located in said exhaust line upstream of said first particulate filter component.
It is also desirable to provide a particulate filter unit adapted to be mountable on such an internal combustion engine system. According to an aspect of the present invention, a particulate filter unit for an internal combustion engine system comprises at least a first particulate filter component defining a first flow path, a second particulate filter component defining a second flow path, said first particulate filter component and said second particulate filter component being thermally connected, and said first flow path and said second flow path being separate.
The present invention and its advantages will be well understood on the basis of the following description, which is given as an illustrated example, without restricting the scope of the invention, in relation with the annexed drawings, among which:
Internal combustion engine system 1 is equipped with a turbocharger 3, which comprises a compressor 31 and a turbine 32 joined together by a driving shaft 33. An inlet 321 of turbine 32 is connected to exhaust manifold 22. The turbine 32 is located in the exhaust line 15, whereas the compressor 31 is located in the intake line 11. Internal combustion engine system 1 may further comprise a charge air cooler 4, located in the intake line 11 downstream of an outlet 312 of compressor 32 and upstream of intake manifold 21. Charge air cooler 4 is adapted to cool intake gases before they enter internal combustion engine 2. Thus, intake gases flow out of compressor 31 from compressor outlet 312, through charge air cooler 4 and into intake manifold 21.
Internal combustion engine system 1 also comprises an exhaust gas recirculation assembly 5. EGR assembly 5 comprises an assembly inlet 50 which is connected downstream of an outlet 322 of turbine 32. On
EGR assembly 5 comprises a recirculation flow path 52 which is separated from a release exhaust flow path 51 by a flow divider, that can be made of a recirculation valve 8, which is arranged at the EGR assembly inlet 50 in order to divide the turbine exhaust flow FO of exhaust gases in two distinct parts of exhaust gases, i.e. a release exhaust flow Fl of exhaust gases and a recirculation flow F2 Of exhaust gases. The recirculation flow F2 is a part of the turbine exhaust gases F0 which flow into said exhaust line 15. The recirculation flow F2 is collected by the EGR assembly inlet 50 located downstream of the turbine 32. The portion of the turbine exhaust flow F0 of exhaust gases that flows into release exhaust flow path 51 forms the release exhaust flow F1, whereas the portion of the turbine exhaust flow F0 that flows into recirculation flow path 52 forms the recirculation flow F2.
The release exhaust flow path 51 ends up to the atmosphere through a release outlet 53, whereas recirculation flow path 52 ends up to the intake line 11 with a recirculation outlet 54. Thus, release exhaust flow path 51 extends downstream of recirculation valve 8 and upstream of release outlet 53, whereas recirculation flow path 52 extends downstream of recirculation valve 8 and upstream of recirculation outlet 54. The recirculation outlet 54 is connected, upstream of the compressor 31, to intake line 11 so as to allow the recirculation flow F2 towards the intake line 11 and towards the compressor 31.
Release exhaust flow path 51 is intended to release into the atmosphere the assembly exhaust flow F1 after its cleansing as will be discussed below. A controllable mobile flap 10 may be arranged downstream of the flow divider in order to further control the rate of release exhaust flow F1.
On the other hand, recirculation flow path 52 drives recirculation flow F2 towards recirculation outlet 54.
An EGR mixer 12 is connected to recirculation outlet 54 and to a fresh air inlet 13. EGR mixer 12 mixes the recirculation flow F2 with a flow FA of fresh air. The resulting mixture forms the intake gases flow Fl that flows in the intake line 11 towards an inlet 311 of compressor 31 through an intake flow path 14. Turbocharger 3 is hence arranged to have its turbine outlet 322 connected to EGR assembly inlet 50 and its compressor inlet 311 connected to the EGR mixer 12. The flow divider may be a three-way valve 8, preferably a three-way proportional valve, often called recirculation valve or EGR valve. Recirculation valve 8 controls the ratio F1/F0 of release exhaust flow F1 over turbine exhaust flow F0 and the ratio F2/F0 of recirculation flow F2 over turbine exhaust flow F0. In other words, recirculation valve 8 controls the portion of exhaust gases flowing into release exhaust flow path 51 and the portion of exhaust gases that flows into recirculation flow path 52. For instance, recirculation valve 8 may allow 50% of exhaust gases into release exhaust flow path 51 and the other 50% into recirculation flow path 52 or 80% and 20% respectively, etc.
A converter unit 6 is fluidically arranged onto release exhaust flow path 51, in the exhaust line 15 and downstream of the turbine 32. Converter unit 6 is adapted to decrease at least the amount of nitrogen oxides (NOx) in release exhaust flow F1. Converter unit 6 may comprise an oxidation catalyst 61 coupled with a reduction catalyst 62. Oxidation catalyst 61 is located in the exhaust line 15, upstream of the first particulate filter component 71. Such an oxidation catalyst 61 may also be located upstream of recirculation valve 8, to help further cleansing of exhaust gases. Like the terms “connect” and “connection”, the term “fluidically” refers to a link that enables a fluid to flow between two or more points or parts.
Such an oxidation catalyst, like a Diesel oxidation catalyst (DOC), is able to convert for instance carbon monoxide (CO) into carbon dioxide (CO2), nitrogen monoxide (NO) into nitrogen dioxide (NO2) and remaining hydrocarbons (HC) into less hazardous products. Such a reduction catalyst, like a selective catalyst reduction (SCR) system, is able to reduce nitrogen monoxide (NO) into neutral nitrogen (N2). Converter unit may also consist of or comprise a lean Nox trap (LNT) catalyst, a three-way catalyst or any other known engine after treatment system (EATS) able to treat nitrogen oxides (NOx). The internal combustion engine system 1 also comprises a particulate filter unit 7, in order to decrease the amount of particulate products, like soot or other organic residues, within the exhaust gases. Particulates filter unit 7 can comprise a Diesel particulate filter unit, which is more specifically adapted to Diesel engine systems. As shown at
Indeed, first particulate filter component 71 is fluidically arranged in release exhaust flow path 51, whereas second particulate filter component 72 is fluidically arranged in recirculation flow path 52. First particulate filter component 71 is fluidically arranged in the EGR assembly 5 downstream of the EGR assembly inlet 50 and upstream of recirculation outlet 54. Release exhaust flow F1 flows into first particulate filter component 71, while recirculation flow F2 flows into second particulate filter component 72. First particulate filter component 71 is fluidically located downstream of converter unit 6. Like converter unit 6, first and/or second particulate filter components 71 and/or 72 may comprise an oxidation catalyst.
An EGR cooler 9 may be arranged onto recirculation flow path 52, downstream of second particulate filter component 72 and upstream of recirculation outlet 54, in order to cool the recirculation portion of exhaust gases.
Gas-tight partition 73 is of a general cylindrical shape along an axial direction. Particulate filter unit 7 comprises an outer cylindrical wall 74 which is arranged in a coaxial manner with gas-tight partition 73. The term cylindrical herein refers to cylinder with a circular basis, but other kinds of cylinders may also be suitable to form the particulate filter unit, for instance an elliptic cylinder. Moreover, the gas-tight partition can have the shape of a prism. First particulate filter component 71 extends between gas-tight partition 73 and outer cylindrical wall 74 of unit 7, whereas second particulate filter component 72 is fully laterally embedded or encased into gas-tight partition 73, hence into first particulate filter component 71.
The main exhaust flow F1 flows along the axial direction through first particulate filter component 71. On the other hand, the recirculation flow F2 flows along the axial direction through second particulate filter component 72, without mixing with the main exhaust flow F I because of separation by gas- tight partition 73.
In release exhaust flow path 51, both converter unit 6 and first particulate filter component 71 result in pressure drops, whereas in recirculation flow path 52 only second particulate filter component 72 results in a significant pressure drop, because EGR cooler 9 will usually induce a lesser pressure drop.
In other words, recirculation flow path 52 avoids converter unit 6, thus limiting the pressure drop. Inversely, converter unit 6 helps increasing pressure at the upstream point of release exhaust flow path 51, i.e. at recirculation valve 8. This provides the advantage that mobile flap 10 can be more opened, sometimes even fully opened, than the mobile flap of a prior art long-route EGR assembly. The pressure drop due to converter unit 6 indeed compensates for the pressure drop due to the connection of recirculation flow path 52 onto EGR mixer 12, without requiring the exhaust gases flow rate to be lessened by mobile flap 10. Eventually, this results in lower pressure at turbine outlet 322. Such a lower pressure improves the efficiency of turbine 32, hence the fuel consumption of internal combustion engine system 1.
According to another aspect of the present invention, first particulate filter component 71 and second particulate filter component 72 are thermally connected. Indeed, first particulate filter component 71 totally overlaps gas- tight partition 73, while gas-tight partition 73 totally overlaps second particulate filter component 72. Overlap″ herein means that one piece covers, at least partly, another piece. Thus, gas-tight partition 73 allows heat transfer between first particulate filter component 71 and second particulate filter component 72.
In the present application, “thermally connected” means that heat is transferred from first particulate filter component 71 to second particulate filter component 72. Such heat transfer occurs by conduction rather than by convection or radiation.
Thermal conductivity of gas-tight partition 73 should preferably be higher than 25 W·m−1·K−1. To this aim, gas-tight partition 73 can be made of metal or metal compounds. For this purpose too, the thickness t73 of gas-tight partition 73 can range between 1 mm and 10 mm. Such features of gas-tight partition 73, combined with the overlapping arrangement with first and second particulate filter components 71 and 72, enable high heat transfers between first and second particulate filter components 71 and 72. Heat conduction results from indirect contact between first and second particulate filter components 71 and 72, i.e. heat is transferred by conduction through the gas-tight partition 73.
Alternatively, other heat transferring means can be used, either solid or fluid, liquid or gaseous, for achieving heat conduction and/or forced heat convection. Moreover, heat transfer can be achieved by a combination of such heat transferring means.
Besides, heat transfer can result from conduction by direct contact between first and second particulate filter components. Purposely, according to a non shown embodiment, first and second particulate filter components can be arranged not only adjacent but also contiguously, i.e. without any intermediate part like gas-tight partition 73. First and second particulate filter components can overlap partly or totally, for instance side-by-side.
Besides, a heating device may be arranged into release exhaust flow path 51 , either near or within first particulate filter component 71, in order to promote the oxidation of the particulate products deposited in first particulate filter component 71. This oxidation process, as known from prior art, results in the so-called “regeneration” of first particulate filter component 71. Since gas- tight partition 73 transfers heat from first particulate filter component 71 to second particulate filter component 72, the regeneration of second particulate filter component 72 also occurs during such a regeneration process, without having to provide a specific heating device for the second particulate filter.
Thus, it only takes one common heating device to operate the regeneration of first and second particulate filter components 71 and 72, i.e. of the full particulate filter unit 7. Such a heating device can comprise a fuel injector 75 located just upstream of first particulate filter component 71 and arranged to inject fuel, downstream of the converter unit 6, in the exhaust line 15 and/or into the first particulate filter component 71. This injected fuel 10 burns into first particulate filter component 71 and heats up second particulate filter component 72. Alternatively, such a heating device may consist of or comprise an electric resistor embedded into first particulate filter component or of a burner located just upstream of first particulate filter component 71. The heating device is intended to promote the regeneration of first and second particulate filter components 71 and 72.
The regeneration process of particulate filter unit 7 may be started and controlled in a usual manner. To this aim, the internal combustion engine system I may also comprise sensors, e.g. pressure sensors, to start the regeneration process and control its duration and its frequency.
Alternatively, the regeneration of particle filter unit 7 can be passive, i.e. without a need for a burner or a fuel injector.
One or more supply ducts 65 are arranged just upstream of converter unit 6 in order to supply a deoxidizing agent to convert unit 6. The supply duct 65 is connected to the exhaust line 15 upstream of said converter unit 6.
For instance, where converter unit 6 consists of or comprises a selective catalyst reduction (SCR) system, supply duct 65 may bring urea in a fluidic state.
Advantageously, the supply duct may be located downstream of the EGR assembly inlet, so that no deoxydizing agent is conveyed by the recirculation gases.
Other embodiments are also contemplated to be within the scope of the present invention. For instance, the flow divider may consist of or comprise a simple three-way tee, instead of a three-way valve like recirculation valve 8 In such a case, EGR flow could be controlled by the flap 10. Alternatively, the EGR flow could be controlled by a proportional valve located in the EGR assembly, for example downstream of the EGR cooler.
According to a non shown embodiment, the heating device may be located either near or within the second particulate filter component in order to heat up the first particulate filter component. Besides, particulate filter unit, hence first and second particulate filter components can be of other suitable forms. Moreover, particulate filter unit may comprise more than two particulate filter components.
The use of an internal combustion engine system according to the present invention increases the efficiency of the converter unit, since the latter can operate at high temperatures. Furthermore, the use of such an internal combustion engine system decreases the fuel consumption of the engine, because it keeps turbine pressure relatively low.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/IB08/55637 | 11/6/2008 | WO | 00 | 5/4/2011 |
