Patent Application
20070033929
The present disclosure relates generally to exhaust systems and fuel reformers.
Fuel reformers may be used for a variety of purposes. In some cases, for example, fuel reformers are used in the process of regenerating emission abatement devices such as NOx traps and particulate traps. In other cases, fuel reformers are used to provide hydrogen (H2) to an internal combustion engine to enhance the fuel combustion process.
According to a first aspect of the present disclosure, there is provided an apparatus having parallel and coaxial first and second exhaust gas passageways. A fuel reformer is positioned in the first exhaust gas passageway and configured to partially combust fuel supplied to the first exhaust gas passageway with oxygen from exhaust gas present in the first exhaust gas passageway to generate partial combustion product. Placement of the fuel reformer in the first exhaust gas passageway facilitates control of the air-to-fuel ratio of the flow delivered to the fuel reformer and thus facilitates generation of the partial combustion product.
A component is fluidly coupled to the first and second exhaust gas passageways to receive the partial combustion product from the first exhaust gas passageway and exhaust gas from the second exhaust gas passageway. The component may be, for example, an emission abatement device (e.g., a NOx trap, a particulate abatement device, a selective catalytic reduction device, or any combination thereof) or an internal combustion engine.
According to a second aspect of the disclosure, the fuel reformer is a catalyst. The catalyst is activated by the heat of the exhaust gas in the first exhaust gas passageway and catalyzes a chemical reaction to partially combust the fuel into hydrogen (H2) and carbon monoxide (CO) which are useful in the regeneration of NOx traps and particulate abatement devices and may also be useful with selective catalytic reduction devices. The hydrogen (H2) is also useful for enhancement of combustion of an internal engine.
The above and other features of the present disclosure will become apparent from the following description and the attached drawings.
a is a diagrammatic view showing a second coaxial parallel flow arrangement for use with the first and second apparatus; and
While the concepts of the present disclosure are susceptible to various modifications and alternative forms, specific exemplary embodiments thereof have been shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that there is no intent to limit the disclosure to the particular forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives following within the spirit and scope of the invention as defined by the appended claims.
Referring to
Such an arrangement facilitates control of the air-to-fuel ratio of the flow delivered to the fuel reformer 16 and thus facilitates generation of the partial combustion product. Further, since oxygen of the exhaust gas is used, it avoids the need for a supplemental source of oxygen. In addition, an ignition source is not needed because the heat of the exhaust gas is sufficient for the partial combustion reaction.
The system 10 includes an internal combustion engine 20 (e.g., a diesel engine), a parallel flow arrangement 22, and the emission abatement device 12. The engine 20 produces the exhaust gas which flows through an exhaust gas supply passageway 24. The parallel flow arrangement 22 then divides the exhaust gas stream to flow into the parallel passageways 14, 18. A portion of the exhaust gas flows into the passageway 14 containing the fuel reformer 16. The other portion of the exhaust gas flows into the passageway 18. The passageways 14, 18 recombine downstream from the fuel reformer 16 into a downstream exhaust gas passageway 25 which delivers the H2 and/or CO produced by the fuel reformer 16 and the exhaust gas from the passageway 18 to the emission abatement device 12.
The emission abatement device 12 may be, for example, a NOx trap, a selective catalytic reduction (SCR) device, or a particulate abatement device. A NOx trap is used to remove NOx from the exhaust gas. It does so by trapping NOx present in the exhaust gas under lean conditions (as is normally the case in diesel exhaust) and reducing the trapped NOx to nitrogen under rich conditions when the fuel reformer 16 is operated to produce the partial combustion product. The partial combustion product (e.g., H2, CO) is thus useful as a NOx-reducing agent. If the fuel reformer 16 is operated to produce the partial combustion product for a longer time, the partial combustion product can be used to desulphate the NOx trap 16.
An SCR device operates in conjunction with the partial combustion product to convert NOx into nitrogen without the need to first trap the NOx and then release and reduce the NOx. The SCR device is “selective” in the sense that it catalyzes a reaction between the partial combustion product (e.g., H2, CO) generated by the fuel reformer 16 and NOx present in the exhaust gas. The NOx is thereby removed from the exhaust gas.
A particulate abatement device is used to remove particulates from the exhaust gas. It may take the form of a particulate trap (catalyzed or uncatalyzed) alone or in combination with an upstream oxidation catalyst (e.g., diesel oxidation catalyst). The partial combustion product (e.g., H2, CO) may be oxidized in the presence of the catalyst of a catalyzed particulate trap or in the presence of an upstream oxidation catalyst to generate heat useful for burning off particulate matter trapped by the particulate trap so as to regenerate the particulate trap.
It is within the scope of this disclosure for the emission abatement device 12 to include any combination of a NOx trap, an SCR device, and a particulate abatement device. One such combination example is an SCR device and a particulate trap.
Fuel is supplied to the passageway 14 by a fuel supplier 26. A fuel line 28 of the fuel supplier 26 is coupled to the passageway 14 to supply fuel to passageway 14 upstream from the fuel reformer 16. The fuel may be, for example, diesel fuel in liquid form or as a vapor. The fuel supplier 26 is not coupled to the passageway 18.
The system 10 may be used with or without an exhaust gas valve 30 to control flow of the exhaust gas between passageways 14, 18. In the case in which the system 10 has the valve 30, the valve 30 may be located in either passageway 14, 18 or at the upstream junction of the two passageways 14, 18.
A controller 32 is electrically coupled to the fuel supplier 26 via an electrical line 34 and, when the valve 30 is included, it is electrically coupled to the valve 30 via an electrical line 36 to control operation of the fuel supplier 26 and the valve 30. The controller 32 is thus able to vary the injection rate of fuel into passageway 14 and/or vary admission of exhaust gas and thus oxygen into passageway 14. In so doing, the controller 32 is able to control the air-to-fuel ratio of the flow delivered to the fuel reformer 16 to facilitate generation of the partial combustion product by the fuel reformer 16. Exemplarily, in the case where the emission abatement device 12 is a NOx trap, the controller 32 may cycle operation of the fuel supplier 26 so as to provide fuel to the passageway 14 for a predetermined period of time (e.g., three seconds) followed by a predetermined period of time (e.g., 60 seconds) in which fuel is not supplied to passageway 14.
To further facilitate the control of the air-to-fuel ratio, the system 10 may employ a sensor 38 and/or engine mapping to provide input(s) to the controller 32 for control of the fuel supplier 26 and/or the valve 30. The sensor 38 may be, for example, a lambda sensor coupled to the passageway 14 upstream from the fuel reformer 16 for sensing the air-to-fuel ratio of the flow in the passageway 14. In such a case, the sensor 38 is electrically coupled to the controller 32 via an electrical line 40 to provide its sensor output to controller 32. The controller 32 may also have stored therein engine mapping information for control of the fuel supplier 26 and/or the valve 30 based on operational parameters associated with the engine 20 (e.g., engine rpm, temperature, throttle position).
The fuel reformer 16 is configured, for example, as a catalyst in the form of a catalyzed substrate. The catalyst is, for example, a metallic catalyst. In the case where the fuel reformer 16 is a catalyst, the temperature of the catalyst is elevated to its activation temperature by the heat of the exhaust gas. Moreover, use of a catalyst obviates the need for an ignition source with its own power supply to ignite the combustible mixture in the passageway 14.
The apparatus 10 is thus able to generate partial combustion product through the use of relatively “fine” control of the air-to-fuel ratio of the flow delivered to the fuel reformer 16. Moreover, it does so by use of the oxygen and heat content of the exhaust gas so that there is no need for supplemental oxygen or an ignition source. It is within the scope of this disclosure, however, to include such supplemental oxygen and an ignition source.
Referring to
Referring to
An annular outer exhaust gas passageway 214 corresponding to the first exhaust gas passageway 14 of the systems 10, 110 is defined between the housing 224 and the inner tube 226. The passageway 214 contains the fuel reformer 16 which has an annular shape to fit in the passageway 214 around the inner tube 226 and an inner exhaust gas passageway 218 defined therein. A fuel dispenser ring 231 is secured to the housing 224 to dispense fuel received from the fuel line 28 into the passageway 214.
The inner tube 226 defines the inner exhaust gas passageway 218 which corresponds to the second exhaust gas passageway 18 of the systems 10, 110 to conduct exhaust gas so as to bypass the fuel reformer 16. The passageways 214, 218 are parallel and have a common axis 233 such that the passageways 214, 218 are coaxial. The optional valve 30 may be configured, for example, as a butterfly valve positioned in the inner exhaust gas passageway 218.
Referring to
Referring to both
In addition, the coaxial feature promotes transfer of exhaust gas heat to the reformer 16 to facilitate operation of the reformer 16. More specifically, in the arrangement 222, heat of exhaust gas in the passageway 218 may be transferred to the surrounding reformer 16 and, in the arrangement 222a, heat of exhaust gas in the passageway 214 may be transferred to the reformer 16 surrounded by the passageway 214. Indeed, more heat may be transferred to the reformer 16 in the arrangement 222a than in the arrangement 222 since, in the arrangement 222a, the reformer 16 is spaced apart from the housing 224 which may be exposed to atmosphere. Such heat transfer to the reformer 16 may be especially useful when the reformer 16 is a catalyst having an activation temperature at which the catalyst becomes operational. Production of the partial combustion product is thus enhanced.
Referring to
Exhaust gas is divided at the upstream junction to flow into a first exhaust gas passageway 314 corresponding to the passageway 14 of the systems 10, 110 and a second exhaust gas passageway 318 corresponding to the passageway 18 of the systems 10, 110. The passageways 314, 318 are parallel but not co-axial. A fuel dispenser 331 is secured to the first conduit 324 to dispense fuel from the fuel line 28 into the passageway 314. The reformer 16 is configured, for example, as a catalyst positioned in the first exhaust gas passageway 314 to partially combust the fuel with oxygen from the exhaust gas present in the passageway 314 into H2 and/or CO. The passageways 314, 318 recombine at the downstream junction between the conduits 324, 326 for delivery of the H2 and/or CO to the downstream exhaust gas passageway 25.
The optional valve 30 may be configured, for example, as a butterfly valve positioned in either passageway 314, 318 to control flow of exhaust into passageways 314, 318. Illustratively, the valve 30 is located in the passageway 318.
While the concepts of the present disclosure have been illustrated and described in detail in the drawings and foregoing description, such an illustration and description is to be considered as exemplary and not restrictive in character, it being understood that only the illustrative embodiments have been shown and described and that all changes and modifications that come within the spirit of the disclosure are desired to be protected.
There are a plurality of advantages of the concepts of the present disclosure arising from the various features of the systems described herein. It will be noted that alternative embodiments of each of the systems of the present disclosure may not include all of the features described yet still benefit from at least some of the advantages of such features. Those of ordinary skill in the art may readily devise their own implementations of a system that incorporate one or more of the features of the present disclosure and fall within the spirit and scope of the invention as defined by the appended claims.
