US20110047996A1

US20110047996A1 - Exhaust gas treatment apparatus with improved pressure pulse damping

Info

Publication number: US20110047996A1
Application number: US12/921,863
Authority: US
Inventors: Ignacio Garcia-Lorenzana Merino; Marco Baccalaro; Volker Reusing; Stefan Stein
Original assignee: Individual
Current assignee: Robert Bosch GmbH
Priority date: 2008-03-10
Filing date: 2009-01-21
Publication date: 2011-03-03
Also published as: EP2265804A1; DE102008013406A1; WO2009112294A1

Abstract

The invention relates to an apparatus for metering at least one medium for reducing pollutant levels in an exhaust system, in particular for the introduction of fuel into an exhaust tract for regenerating an element for reducing pollutant levels in the exhaust tract. The apparatus includes at least one injection valve, in particular, a pressure-regulated injection valve and at least one supply line for supplying the pollutant-reducing medium to the injection valve. At least one pressure damper is provided in the supply line upstream of the injection valve.

Description

PRIOR ART

The invention is based on known methods and apparatuses for posttreatment of exhaust gases, in particular exhaust gases of internal combustion engines, for instance in the automotive field, in energy generation, or in similar fields in natural science and technology. From such fields, techniques are known in which various pollutant-reducing media, especially fluid media (such as liquids or gases) are metered, for instance injected into the exhaust gas. Various techniques and various types of pollutant-reducing media are employed. Examples of such pollutant-reducing media are urea-water solutions, which as a reducing agent reduce nitrogen oxides selectively. Such methods are often also called SCR methods (SCR: selective catalytic reduction).
Other methods are based on the injection of hydrocarbons, as pollutant-reducing media, into exhaust gases. Such methods, which are often also called HCI methods (HCI: hydrocarbon injection), can serve various purposes. For one, an injection of fuel, such as diesel fuel, as a reducing agent can be for instance serve to reduce nitrogen oxides. Other methods are based on a reaction of the injected fuel in an oxidation catalytic converter, which for instance leads to a brief temperature increase in the exhaust tract. This temperature increase can be employed for instance for regenerating an exhaust gas posttreatment apparatus, for instance for regenerating a diesel particle filter by burning off soot.
Without limiting the further possibilities for embodying the pollutant-reducing medium, reference will be made hereinafter essentially to HCI systems. However, it will be pointed out that other types of pollutant-reducing media, especially liquids, can also be employed.
Various apparatuses for introducing the pollutant-reducing medium into the exhaust gas are known from the prior art. For instance, German Patent Disclosure DE 10 2005 040 918 A1 describes a system in which fuel is diverted from a low-pressure part of a reservoir-type injection system and metered into the exhaust gas. The low-pressure part has a pressure maintenance valve, for maintaining a minimum pressure in the low-pressure part.
In the system shown in DE 10 2005 040 918 A1, the low-pressure reservoir, with its liquid volume, ensures a certain calming of pressure fluctuations. Nevertheless, pressure fluctuations in the low-pressure circuit of an injection system of that kind can only seldom be avoided. In other types of furnishing the pollutant-reducing medium as well, such pressure fluctuations occur. Pressure fluctuations can also, depending on the injection system, also be generated by the return from the injectors in the fuel injection system or as a result of pumping.
To avoid these problems of pressure fluctuations, German Patent Disclosure DE 10 2005 034 704 A1 discloses an apparatus and a method for regenerating particle filters. In the apparatus proposed there as well, a calming volume of fuel is employed in order to ensure a certain compensation for pressure fluctuations. It is also proposed that a pressure control valve, which opens and dissipates the pressure if the supplied fuel exceeds a certain value, be disposed in a branch line from the calming volume.
Despite these calming provisions known from the prior art, it has been demonstrated that under some circumstances, there can nevertheless be a potential for improvement. For instance, pressure peaks can still occur and influence the injection of the pollutant-reducing medium. Moreover, cavitation in the supply line of the pollutant-reducing medium, for instance in the low-pressure circuit, can also occur. Such pressure peaks and cavitation can even lead to damage of the components of the system, such as the HCI components, and the hydraulic behavior can be adversely affected.

DISCLOSURE OF THE INVENTION

An apparatus for metering at least one pollutant-reducing medium into an exhaust system is therefore proposed which at least largely avoids the above-described disadvantages of known apparatuses and systems and which ensures that the injection of the pollutant-reducing medium is made uniform. With regard to the embodiment of the pollutant-reducing medium, the above descriptions of known systems can for instance be referred to, especially HCI systems. Especially preferably, the apparatus can be used for regenerating a diesel particle filter, the apparatus being used such that diesel fuel is injected and catalytically combusted into an exhaust tract, for instance upstream of an oxidation catalytic converter. As a result, the temperature in the exhaust system is actively raised, until the burnoff temperature for the soot deposited in the diesel particle filter has been reached.
The proposed apparatus includes at least one injection valve, in particular a pressure-regulated injection valve, for injecting the pollutant-reducing medium into the exhaust system. This can for instance involve a pressure-regulated injection valve, for instance pressure-regulated injection valves, which is already being used on a mass production basis for injecting fuels into combustion chambers of internal combustion engines, and/or for modifying such valves.
The apparatus furthermore includes at least one supply line for supplying the pollutant-reducing medium to the injection valve.
To this extent, the system can largely correspond for instance to the systems described in DE 10 2005 040 918 A1 and/or DE 10 2005 034 704 A1. However, still other designs are also possible. In contrast to the systems known from the prior art, however, in the proposed system at least one pressure damper is received in the supply line, upstream of the injection valve. The term “pressure damper” is to be understood here to mean a device, which damps pressure peaks in the pollutant-reducing medium in the supply line by providing that the excess energy from these pressure peaks is dissipated to and at least partly absorbed by an element, acting as an energy absorber, that is different from the pollutant-reducing medium and that differs from conventional provisions on the inlet side, such as pressure control valves or simple throttle bores. This additional element that receives the excess energy can, as described below, for instance include a solid, porous, or elastic, or (although this is less preferable) a plastic element. Various possibilities are discussed below as examples.
By means of the at least one pressure damper provided according to the invention, the pressure is accordingly efficiently made uniform, and thus an improvement is brought about in the process of injecting the pollutant-reducing medium. Dissipating excess pressure through an additional pressure control valve can be dispensed with, which can bring about a cost saving as well as simplification. Such pressure control valves, however, can, as described below, be provided as additional safety provisions, or provisions for making the pressure uniform. It is also possible to dispense with a calming volume of the kind provided in DE 10 2005 034 704 A1 or also, in the form of the low-pressure reservoir, for instance in DE 10 2005 040 918 A1, or else such a calming volume may be provided as an additional damping measure.
It is especially preferred if the pressure damper has at least one porous element received in the supply line. The porous element can for instance include a highly porous material of open porosity, that is, a material in which the pores form continuously open pore ducts. In particular, a porous element of this kind can be integrated upstream of components of the apparatus that do not resist high pressure peaks. The pressure damper can for instance include a ceramic material, a metal material, a metal alloy, or a combination of that and/or other materials as the porous element. In particular, sintered metals, sintered metal alloys, or sintered ceramics can be used, optionally also in combination.
The pressure damper and/or the porous element may have various geometries. The porous element can for instance be solidified by compaction or molding and ensuing drying and sintering of ceramic slips and/or metal slurries. The damping properties can be adapted to the various most frequently occurring operating conditions, that is, for instance liquid properties, pressures, temperatures, and/or the like that frequently occur during operation. An adaptation to the component geometry, for instance to spatial installation conditions, can also be purposefully made. By means of a purposeful choice of porosity, pore size, or similar parameters of the porous element and/or of a rib thickness of the porous element and/or a length of the porous element or of the pressure damper, the lowering of the pressure level can be optimized in a purposeful way.
Alternatively or in addition to the porous element, the pressure damper can also include at least one hydraulic pressure damper. This hydraulic pressure damper should preferably be arranged in such a way that it includes at least one hydraulic volume of the pollutant-reducing medium. For instance, this hydraulic volume can be a closed-off hydraulic volume, which is received in a widened portion (for instance a pressure vessel). This pressure vessel can be in communication with the supply line via an inlet and an outlet, for instance, or integrated with the supply line.
The hydraulic pressure damper further includes at least one energy reservoir that is different from the hydraulic volume and is in operative communication with the hydraulic volume. While in the case of the use of the porous element, the porous element itself acts as an additional element absorbing the excess energy or excess pressure in the case of pressure peaks, in the case of the hydraulic pressure damper, the energy reservoir acts as an additional element for absorbing the excess energy contained in the pressure peaks and thus for making the pressure uniform.
The energy reservoir may for instance include a mechanical energy reservoir, such as an at least partly elastically deformable plastic or some other elastic element, for instance a spring element. Alternatively or in addition, the energy reservoir can also contain at least one compressible closed-off fluid volume, in particular a gas volume, in particular air. Still other kinds of energy reservoirs are conceivable. The energy reservoir may also be designed such that while it absorbs brief pressure peaks, nevertheless the excess energy of these pressure peaks is returned to the pollutant-reducing medium again once the pressure peak has faded. In this way, besides pressure peaks, pressure incursions, for instance, can also be reduced. The pressure damping properties can optionally be adapted using throttle elements (such as inflow throttles and outflow throttles) received in the supply line, with the pressure level prevailing at the time, and optionally with an overflow valve or a pressure control valve and/or an overpressure valve.
As discussed above, it is especially preferred if the supply line connects a low-pressure system of a fuel system, in particular a reservoir-type injection system (such as a diesel common rail system) with the injection valve.
Furthermore, upstream of the injection valve in the supply line, at least one metering unit can also be received, and the metering unit has at least one valve for controlling a procedure of injection of the pollutant-reducing medium. This metering unit can for instance be controlled by a separate controller and/or by a controller integrated with an engine control unit.
The metering unit can for instance include a shutoff valve, which as a whole turns the injection operation on or off. Alternatively or in addition, the metering unit can include a metering valve which is operated for instance in clocked fashion and subjects the injection valve to pressure in clocked fashion, so that the injection procedure takes place in clocked fashion as well.
Moreover, the metering unit can include one or more pressure measuring devices. For instance, one pressure measuring device can be provided for determining a metering quantity, for instance between a shutoff valve and a metering valve. Alternatively or in addition, one pressure measuring device can be provided between the metering valve and the injection valve, for instance in the form of a pressure sensor for detecting leaks. If at least one such pressure measuring device is provided, then the pressure damper can in particular be disposed upstream of this at least one pressure measuring device, for instance upstream of a pressure measuring device for a metering quantity. In particular, the pressure damper can be integrated entirely or in part in the metering unit, or it may also be provided entirely or in part upstream of the metering unit.
As described above, in addition to the pressure damper, further devices can optionally be provided for making the pressure in the apparatus uniform. In particular, at least one overpressure valve may for instance be provided, which is received in a branch line branching off from the supply line upstream of the pressure damper. Alternatively or in addition, a damping supply of the pollutant-reducing medium can also be received upstream of the pressure damper in the supply line, for instance in a widened part of the supply line and/or in a vessel communicating with the supply line, such as a pressure vessel. To this extent, the apparatus can for instance be supplemented with the additional provisions described in DE 10 2005 034 704 A1.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments of the invention are shown in the drawings and described in further detail in the ensuing description.

Shown are:

FIG. 1, a schematic structure of an internal combustion engine having exhaust gas posttreatment;

FIG. 2, a schematic detailed view of the exhaust gas posttreatment of FIG. 1;

FIG. 3, a first exemplary embodiment of a pressure damper with a porous element; and

FIG. 4, a second exemplary embodiment of a pressure damper with an energy reservoir.

In FIG. 1, highly schematically, an internal combustion engine 110 is shown. The internal combustion engine includes a combustion motor 112, with an air intake tract 114 and an exhaust tract 116. The combustion motor 112 is designed for instance as a turbo diesel motor and includes a turbocharger 118 coupled with the intake tract 114 and the exhaust tract 116. Also provided in the intake tract 114 are a charge air cooler 120 and a throttle valve 122. The internal combustion engine 110 further has an exhaust gas recirculation 124, which branches off from the exhaust tract 116 between the combustion motor 112 and the turbocharger 118 and discharges into the intake tract 114 before the throttle valve 122 and the combustion motor 112. Valves 126 and further coolers 120 can be provided in the exhaust gas recirculation 124.
In this exemplary embodiment, an oxidation catalytic converter 128, symbolically represented in FIG. 1 by “DOC”, is disposed downstream of the turbocharger 118 in the exhaust tract 116. Downstream of this oxidation catalytic converter 128 is in turn a particle filter 130, for instance a diesel particle filter, which is symbolically indicated in FIG. 1 by “DPF”.
An injection valve 132 is provided between the turbocharger 118 and the oxidation catalytic converter 128. By means of this injection valve, which is subjected to pollutant-reducing medium, such as diesel fuel, via a supply line 134, pollutant-reducing medium 136, which in the HCI process is for instance diesel fuel, is injected into the exhaust tract 116. The diesel fuel is catalytically combusted by the oxidation catalytic converter 128, as a result of which the temperature in the exhaust tract 116 is actively raised until the burnoff temperature for the soot deposited in the diesel particle filter 130 is reached. In this way, regeneration of the diesel particle filter 130 can be accomplished.
A metering unit 138 is also disposed in the supply line 134. This metering unit 138, like the supply line 134 and the injection valve 132, is a component of an apparatus 140 for metering the pollutant-reducing medium 136. This apparatus 140 is shown schematically in further detail in FIG. 2 and will be described in further detail below.
Furthermore, in the exemplary embodiment shown in FIG. 1, the apparatus 140 optionally includes a controller 142, which can for instance be integrated entirely or in part with an engine controller (or engine control module, ECM) of the internal combustion engine 110. As shown in FIG. 1, this controller 142 can for instance be subjected to various sensor signals, such as pressure and/or temperature signals, from measurements of various points in the exhaust tract 116. Signals from various pressure sensors 146, 148 integrated with the metering unit 138 can also be sent to the controller 142. The controller 142 generates a first control signal 150 for a shutoff valve 152 (symbolically represented in FIG. 1 by “SV”). The controller 142 also generates a second control signal 154 for triggering a metering valve 156 (symbolically represented by “DV” in FIGS. 1 and 2), downstream of the shutoff valve 152 in the supply line 134, in the metering unit 138. The control signal 154 is also shown schematically in FIG. 1, on the left.
In FIG. 2, highly schematically, the apparatus 140 for metering the pollutant-reducing medium 136 is shown in a modification according to the invention. It can be seen, first, that the supply line 134 connects the injection valve 132, symbolically represented by “IV”, with a low-pressure part 158 of a fuel system (symbolically represented in FIG. 2 by “LPC”). For possible details of this optional communication with the low-pressure part 158, DE 10 2005 040 918 A1 can for instance be consulted. The fuel, as the pollutant-reducing medium 132 flows via the supply line 134, via an optional throttle element 160, to the metering unit 138, which is symbolically represented in FIG. 2 by “MU”. In addition, analogously to the embodiment in DE 10 2005 034 704 A1, for instance, it is optionally possible for a pressure damper volume, not shown in FIG. 2, to be disposed for instance between the throttle element 160 and the metering unit 138.
Inside the metering unit 138, the shutoff 152, at regeneration intervals, initially interrupts the inflow of pollutant-reducing medium 136. Optionally, an overpressure valve 162 can be received in the branch line 164, similarly to the embodiment in DE 10 2005 034 704 A1, for example, which valve connects the supply line 134 with the tank 166. In this way, a pressure level can be reduced, and pressure fluctuations can also be compensated for to a limited extent.
In the metering unit 138, downstream of the shutoff valve 152, is the first pressure sensor 146, whose signal can be used for instance for calculating the clocking of the metering valve 156 and thus for increasing the metering quantity precision. This metering quantity is then made available via the metering valve 156 and delivered to the injection valve 132. A second pressure sensor 148, as a pressure measuring device, for instance for detecting leaks, can optionally be disposed between the injection valve 132 and the metering valve 156.
The injection valve 132 may for instance be a structurally adapted fuel injection valve, which opens at a defined supply pressure and injects pollutant-reducing medium 136 into the exhaust tract. A structurally adapted “K-Jetronic” valve can for instance be used for this.
The apparatus 140 shown in FIG. 2 is modified according to the invention by providing at least one pressure damper 168 upstream of the injection valve 132. For example, a pressure damper 168 of this kind can be disposed at one of the places marked A, B, or C in FIG. 2, or at some or all of these places. Alternatively or in addition, such pressure dampers 168 can be fundamentally disposed at other points in the supply line 138 as well.
Exemplary embodiments of pressure dampers 168 according to the invention that can be provided for instance in an apparatus 140 as in FIG. 2 are shown in FIGS. 3 and 4.
FIG. 3 shows an exemplary embodiment of a pressure damper 168 which functions passively and includes at least one porous element 170 of open porosity. This porous element 170, which for instance, as shown above, can include a ceramic, a metal, a metal alloy, or a combination of these or other materials, is received for instance in a pressure housing 172. This pressure housing 172 is incorporated into the supply line 134 via an inlet 174 and an outlet 176.
The porous element 170 may for instance have nonlinear properties with regard to the permeability for the pollutant-reducing medium 136, so that there is a disproportionate ratio exists for example between the pressure difference at the inlet 174 and outlet 176 and the delivered quantity of pollutant-reducing medium 136. This means that pressure peaks can be intercepted especially effectively by the pressure damper 168. The excess energy contained in the pressure can be absorbed by the porous element 170, for instance.
In FIG. 4, a second possible exemplary embodiment of a pressure damper 168 is shown. In this case, the pressure damper again includes a pressure housing 172, with an inlet 174 and an outlet 176, by way of which inlet and outlet the pressure damper 168 is incorporated into the supply line 134. In the interior of the pressure housing 172, a hydraulic volume 178 of the pollutant-reducing medium 136 is received, which is operatively connected via a ram 180 to a spring element 182, shown in simplified form, as an energy reservoir 184. Instead of the spring element 182, other types of energy reservoirs may for instance be used, as discussed above. A spring chamber 186, in which the spring element 182 is received, can for instance be pressure-relieved via a bore, not shown in FIG. 4. All in all, the hydraulic pressure damper 168 shown in FIG. 4 represents one example of a piston spring reservoir. Still other types of energy reservoirs may be employed, however.

Claims

1-11. (canceled)

12. An apparatus for metering at least one pollutant-reducing medium into an exhaust system, in particular for introducing fuel into an exhaust tract for regenerating an element for reducing pollutant levels in the exhaust tract, including at least one injection valve, in particular a pressure-regulated injection valve, and at least one supply line for supplying the pollutant-reducing medium to the injection valve, wherein at least one pressure damper is provided in the supply line, downstream of the injection valve.

13. The apparatus as defined by claim 12, wherein the pressure damper has at least one porous element received in the supply line.

14. The apparatus as defined by claim 13, wherein the porous element contains at least one of the following materials: a ceramic material; a metal, in particular a sintered metal; a metal alloy, in particular a sintered metal alloy; or a composite material.

15. The apparatus as defined by claim 12, wherein the pressure damper includes at least one hydraulic pressure damper, and the hydraulic pressure damper includes at least one hydraulic volume of the pollutant-reducing medium and at least one energy reservoir that is different from the hydraulic volume and is operatively in communication with the hydraulic volume.

16. The apparatus as defined by claim 13, wherein the pressure damper includes at least one hydraulic pressure damper, and the hydraulic pressure damper includes at least one hydraulic volume of the pollutant-reducing medium and at least one energy reservoir that is different from the hydraulic volume and is operatively in communication with the hydraulic volume.

17. The apparatus as defined by claim 14, wherein the pressure damper includes at least one hydraulic pressure damper, and the hydraulic pressure damper includes at least one hydraulic volume of the pollutant-reducing medium and at least one energy reservoir that is different from the hydraulic volume and is operatively in communication with the hydraulic volume.

18. The apparatus as defined by claim 15, wherein the energy reservoir includes at least one of the following energy reservoirs: an at least partly elastically deformable plastic; a spring element; or a compressible, closed-off fluid volume, in particular a gas volume, in particular air.

19. The apparatus as defined by claim 16, wherein the energy reservoir includes at least one of the following energy reservoirs: an at least partly elastically deformable plastic; a spring element; or a compressible, closed-off fluid volume, in particular a gas volume, in particular air.

20. The apparatus as defined by claim 17, wherein the energy reservoir includes at least one of the following energy reservoirs: an at least partly elastically deformable plastic; a spring element; or a compressible, closed-off fluid volume, in particular a gas volume, in particular air.

21. The apparatus as defined by claim 12, wherein the supply line connects a low-pressure system of a fuel system, in particular a reservoir-type injection system, to the injection valve.

22. The apparatus as defined by claim 20, wherein the supply line connects a low-pressure system of a fuel system, in particular a reservoir-type injection system, to the injection valve.

23. The apparatus as defined by claim 12, wherein at least one metering unit is also received upstream of the injection valve in the supply line, and the metering unit has at least one valve for controlling a procedure of injection of the pollutant-reducing medium.

24. The apparatus as defined by claim 22, wherein at least one metering unit is also received upstream of the injection valve in the supply line, and the metering unit has at least one valve for controlling a procedure of injection of the pollutant-reducing medium.

25. The apparatus as defined by claim 23, wherein the metering unit further includes at least one pressure measuring device, and the pressure damper is disposed upstream of the pressure measuring device.

26. The apparatus as defined by claim 24, wherein the metering unit further includes at least one pressure measuring device, and the pressure damper is disposed upstream of the pressure measuring device.

27. The apparatus as defined by claim 25, wherein the pressure damper is integrated entirely or in part with the metering unit and/or is disposed entirely or in part upstream of the pressure measuring device.

28. The apparatus as defined by claim 26, wherein the pressure damper is integrated entirely or in part with the metering unit and/or is disposed entirely or in part upstream of the pressure measuring device.

29. The apparatus as defined by claim 12, further having at least one overpressure valve, and the overpressure valve is received in a branch line branching off from the supply line upstream of the pressure damper.

30. The apparatus as defined by claim 28, further having at least one overpressure valve, and the overpressure valve is received in a branch line branching off from the supply line upstream of the pressure damper.

31. The apparatus as defined by claim 12, further having at least one damping volume, received in the supply line upstream of the pressure damper, the damping volume including a damping supply of the pollutant-reducing medium.