WO2009112294A1

WO2009112294A1 - Exhaust gas treatment device with improved pressure pulse damping

Info

Publication number: WO2009112294A1
Application number: PCT/EP2009/050653
Authority: WO
Inventors: Ignacio Garcia-Lorenzana Merino; Marco Baccalaro; Volker Reusing; Stefan Stein
Original assignee: Robert Bosch Gmbh
Priority date: 2008-03-10
Filing date: 2009-01-21
Publication date: 2009-09-17
Also published as: DE102008013406A1; EP2265804A1; US20110047996A1

Abstract

The invention relates to a device (140) for metering at least one medium (136) for reducing pollutant levels in an exhaust system, in particular for the introduction of fuel into an exhaust line (116) for regenerating an element (130) for reducing pollutant levels in the exhaust line (116). The device (140) comprises at least one injection valve (132), in particular, a pressure-regulated injection valve (132) and at least one supply line (134) for supplying The pollutant-reducing medium (136) to The injection valve (132). At least one pressure damper (168) is provided in The supply line (134) upstream of The injection valve (132).

Description

title

Exhaust after-treatment device with improved pressure pulse damping

State of the art

The invention is based on known methods and devices for the aftertreatment of exhaust gases, in particular of exhaust gases of internal combustion engines, for example in the automotive sector, in power generation or in similar fields of science and technology. From such areas, techniques are known in which various pollutant-reducing media, in particular fluid media (for example, liquids or gases) metered into the exhaust gas, for example, sprayed become. Different techniques and different types of pollutant-reducing media are used. Examples of such pollutant-reducing media are urea-water solutions which selectively reduce nitrogen oxides as reducing agents. Such processes are often referred to as SCR (Selective Catalytic Reduction) processes.

Other processes rely on the injection of hydrocarbons as pollutant-reducing media in exhaust gases. Such processes, which are often also referred to as HCl (hydrocarbon injection) processes, can serve different purposes. On the one hand, an injection of fuel, for example diesel fuel, can serve as a reducing agent, for example for the reduction of nitrogen oxides. Other methods are based on an implementation of the injected fuel in an oxidation catalyst, which leads, for example, to a short-term increase in temperature in the exhaust system. This temperature increase can be used for example for the regeneration of an exhaust aftertreatment device, for example for the regeneration of a diesel particulate filter by Rußabbrand.

Without restricting the further possibilities of designing the pollutant-reducing medium, reference will be made below to HCI systems in the following. It should be noted, however, that other types of pollutant-reducing media, in particular liquids, can be used. Various devices for introducing the pollutant-reducing medium into the exhaust gas are known from the prior art. For example, DE 10 2005 040 918 A1 describes a system in which fuel is branched off from a low-pressure part of a storage injection system and metered into the exhaust gas. The low-pressure part has a pressure-maintaining valve in order to maintain a minimum pressure in the low-pressure part.

In the system shown in DE 10 2005 040 918 A1, the low-pressure accumulator with its fluid volume ensures a certain calming of pressure oscillations. Nevertheless, pressure oscillations in the low pressure circuit of such an injection system can rarely be avoided. Also in other ways of providing the pollutant reducing medium occur such pressure oscillations. Depending on the injection system, pressure oscillations can also be generated, for example, by the return of the injectors of the fuel injection system or by pumps.

In order to reduce this problem of pressure oscillations, DE 10 2005 034 704 A1 discloses a device and a method for the regeneration of particle filters. In the device proposed there, too, a calming volume of the fuel is used in order to provide for a certain compensation of pressure fluctuations. It is also proposed to arrange a pressure control valve in a branch line from the settling volume, which, when the supplied fuel exceeds a certain value, opens and discharges the pressure.

Despite these calming measures known from the prior art, it has been found that under certain circumstances there may still be room for improvement. Pressure peaks can still occur and influence the injection of the pollutant-reducing medium. Furthermore, cavitation may also occur in the supply line of the pollutant-reducing medium, for example in the low-pressure circuit. Such pressure peaks and cavitations can even lead to damage to the components of the system, for example the HCI components, and the hydraulic behavior can be adversely affected.

Disclosure of the invention

A device is therefore proposed for metering at least one pollutant-reducing medium into an exhaust gas system, which at least largely avoids the disadvantages of known devices and systems described above and is suitable for uniformity of the injection of the pollutant-reducing medium provides. With regard to the design of the pollutant-reducing medium, reference may be made, for example, to the above descriptions of known systems, in particular to HCI systems. Particularly preferably, the device can be used for the regeneration of a diesel particulate filter, wherein the device is used such that diesel fuel is injected, for example, in front of an oxidation catalyst in an exhaust tract and catalytically burned. As a result, the temperature in the exhaust system is actively raised until the combustion temperature for the soot stored in the diesel particulate filter is reached.

The proposed device comprises at least one injection valve, in particular a pressure-controlled injection valve, for injecting the pollutant-reducing medium into the exhaust system. For example, this may be a pressure-controlled injection valve, for example pressure-controlled injection valves, which are already used as standard for the injection of fuels into combustion chambers of internal combustion engines and / or modifications of such valves.

Furthermore, the device comprises at least one supply line for supplying the pollutant-reducing medium to the injection valve.

In this respect, the system can, for example, to a large extent correspond to the systems described in DE 10 2005 040 918 A1 and / or in DE 10 2005 034 704 A1. However, other embodiments are possible. In contrast to the systems known from the prior art, however, at least one pressure damper is accommodated in the proposed system in the supply line upstream of the injection valve. Under a "pressure damper" here is a device to understand which pressure peaks in the pollutant reducing medium in the supply line attenuates that the excess energy of these pressure peaks to one of the pollutant reducing medium and conventional upstream measures, such as pressure control valves or simple throttle bores, various Element as an energy absorber and at least partially absorbed by said element, said additional energy absorbing element may, as described below, comprise for example a solid, a porous or an elastic or also (which is less preferred) a plastic element Possibilities are outlined below as examples.

By inventively provided at least one pressure damper so an equalization of the pressure and thus an improvement of the injection process of the pollutant reducing medium is brought about in an efficient manner. On a discharge of excess pressure by an additional pressure control valve can be omitted -A- which can result in cost savings and simplification. However, such pressure control valves can, as explained below, be provided as additional security measures or measures of equalization. Also, a calming volume, as provided in DE 10 2005 034 704 Al or as also for example in DE 10 2005 040 918 Al in the form of low-pressure accumulator, can also be dispensed with, or it may be such a sedation volume provided as an additional damping measure.

It is particularly preferred if the pressure damper has at least one porous element received in the supply line. For example, the porous element may comprise a highly porous material with open porosity, ie a material in which the pores form continuous pore channels. In particular, such a porous element can be integrated in front of components of the device which do not withstand high pressure peaks. The pressure damper may comprise, for example, a ceramic material, a metallic material, a metal alloy or combinations of these and / or other materials as a porous element. In particular, it is possible to use sintered metals, sintered metal alloys or sintered ceramics, if appropriate also in combination.

The pressure damper and / or the porous element can have different geometries. The porous element can be solidified, for example, by compression or molding and subsequent drying and sintering of ceramic and / or metal slips. The damping characteristics can be adapted to the most common operating conditions, i. For example, frequently occurring in operation fluid properties, pressures, temperatures and / or the like, to be adjusted. An adaptation of the component geometry, for example, to spatial installation conditions, can be targeted. By a specific choice of the porosity, the pore size or similar parameters of the porous element and / or a web thickness of the porous element and / or a length of the porous element or the pressure damper, the reduction of the pressure level can be optimized.

Alternatively or in addition to the porous element, the pressure damper may also comprise at least one hydraulic pressure damper. This hydraulic pressure damper should preferably be set up such that it comprises at least one hydraulic volume of the pollutant-reducing medium. For example, this hydraulic volume can be a closed hydraulic volume which is accommodated in an extension (for example a pressure vessel). This pressure vessel may, for example, be in communication with or integrated into the supply line via an inlet and an outlet. Furthermore, the hydraulic pressure damper comprises at least one different from the hydraulic volume and in operative connection with the hydraulic volume energy storage. While in the case of the use of the porous element, the porous element itself acts as an additional, the excess energy or the excess pressure at pressure peaks receiving element acts in the case of hydraulic pressure damper, the energy storage as an additional element for receiving the excess energy contained in the pressure peaks and thus to equalize the pressure.

The energy store may, for example, comprise a mechanical energy store, for example an at least partially elastically deformable plastic or another elastic element, for example a spring element. Alternatively or additionally, the energy store may also contain at least one compressible closed fluid volume, in particular a gas volume, in particular air. Other types of energy storage are conceivable. The energy storage device can also be designed such that it absorbs short-term pressure peaks, but the excess energy of these pressure peaks is fed back to the pollutant-reducing medium after the pressure peak subsides. In this way, for example, in addition to pressure peaks and pressure drops can be reduced. If appropriate, the pressure damping properties can be matched with throttle elements accommodated in the supply line (for example inlet throttles, outlet throttles), the respectively prevailing pressure level and optionally an overflow valve or a pressure control valve and / or an overpressure valve.

As illustrated above, it is particularly preferred if the supply line connects a low-pressure system of a fuel system, in particular a storage injection system (for example, a diesel common rail system), with the injection valve.

Furthermore, at least one metering unit can be accommodated in the supply line in front of the injection valve, which has at least one valve for controlling an injection process of the pollutant-reducing medium. This metering unit can be controlled, for example, by a separate controller and / or by a controller integrated in a motor control unit.

The metering unit may comprise, for example, a shut-off valve which as a whole switches the operation of the injection on or off. Alternatively or additionally, the metering unit may comprise a metering valve, which is operated, for example, clocked and wel- Ches clocked the injection valve pressurized, so that the injection process is clocked.

Furthermore, the metering unit may comprise one or more pressure measuring devices. For example, a pressure measuring device may be provided for determining a metered quantity, for example between a shut-off valve and a metering valve. Alternatively or additionally, a pressure measuring device may be provided between a metering valve and the injection valve, for example as a pressure sensor for leakage detections. If at least one such pressure measuring device is provided, then the pressure damper can be arranged in particular upstream of this at least one pressure measuring device, for example upstream of a pressure measuring device for a metered quantity. In particular, the pressure damper can be completely or partially integrated in the metering unit or also be provided wholly or partly upstream of the metering unit.

As described above, in addition to the pressure damper, other devices may optionally be provided to equalize the pressure in the device. Thus, in particular, at least one pressure relief valve can be provided, which is accommodated in a branch line branching off from the supply line upstream of the pressure damper. Alternatively or additionally, a damping reserve of the pollutant-reducing medium may also be accommodated in front of the pressure damper in the supply line, for example in an extension of the supply line and / or a vessel connected to the supply line, for example a pressure vessel. In this respect, the device can be supplemented, for example, by the additional measures described in DE 10 2005 034 704 A1.

Brief description of the drawings

Embodiments of the invention are illustrated in the drawings and explained in more detail in the following description.

Show it:

Figure 1 shows a schematic structure of an internal combustion engine with an exhaust aftertreatment;

Figure 2 is a schematic detail of the exhaust aftertreatment according to Figure 1; FIG. 3 shows a first exemplary embodiment of a pressure damper with a porous element; and

4 shows a second embodiment of a pressure damper with a Energiespei- rather.

FIG. 1 shows in highly schematic form an internal combustion engine 110. The internal combustion engine comprises an internal combustion engine 112 with an intake tract for air 114 and an exhaust line 116. The internal combustion engine 112 is designed, for example, as a turbo diesel engine and comprises a turbocharger 118 coupled to the intake tract 114 and the exhaust line 116. Furthermore, a charge air system is provided in the intake tract 114. Cooling device 120 and a throttle valve 122 is provided. The internal combustion engine 110 also has an exhaust gas recirculation system 124, which branches off from the exhaust gas line 116 between the internal combustion engine 112 and the turbocharger 118 and opens into the intake tract 114 between the throttle valve 122 and the internal combustion engine 112. In the exhaust gas recirculation 124 valves 126 and other cooling devices 120 may be provided.

Downstream of the turbocharger 118, in this exemplary embodiment, an oxidation catalytic converter 128 is arranged in the exhaust line 116, which is symbolically denoted "DOC" in FIGURE 1. This oxidation catalytic converter 128 is in turn followed by a particulate filter 130, for example a diesel particulate filter, which is shown symbolically in FIG "DPF" is designated.

Between the turbocharger 118 and the oxidation catalyst 128, an injection valve 132 is provided. By means of this injection valve, which is acted upon via a supply line 134 with pollutant-reducing medium, for example diesel fuel, pollutant-reducing medium 136, ie in the HCl process, for example diesel fuel, injected into the exhaust line 116. The diesel fuel is catalytically combusted by the oxidation catalytic converter 128, as a result of which the temperature in the exhaust gas train 116 is actively raised until the burnup temperature for the soot stored in the diesel particle filler 130 has been reached. In this way, regeneration of the diesel particulate filter 130 may be effected.

Furthermore, a metering unit 138 is arranged in the supply line 134. This metering unit 138 is, like the supply line 134 and the injection valve 132, part of a device 140 for metering the pollutant reducing medium 136. This device 140 is shown schematically in Figure 2 in more detail and will be explained further below. Furthermore, in the exemplary embodiment shown in FIG. 1, the device 140 optionally includes a controller 142, which, for example, can be completely or partially integrated in an engine control module (ECM) of the internal combustion engine 110. As shown in FIG. 1, this control 142 can be acted upon, for example, by various sensor signals, such as, for example, pressure and / or temperature signals from measurements at various locations of the exhaust gas line 116. Signals from various pressure sensors 146, 148 integrated in the metering unit 138 can also be fed to the controller 142. The controller 142 generates a first control signal 150 for a shut-off valve 152 (symbolically denoted "SV" in FIG. 1) .Furthermore, the controller 142 generates a second control signal 154 for controlling a metering valve 156 downstream of the shut-off valve 152 in the supply line 134 (in FIG Figures 1 and 2 symbolically denoted by "DV") in the metering unit 138. The control signal 154 is shown schematically in Figure 1 left.

FIG. 2 shows in highly schematic form the device 140 for metering the pollutant-reducing medium 136 according to a modification according to the invention. It can initially be seen that the supply line 134 connects the injection valve 132 symbolically labeled "IV" with a low-pressure part 158 of a fuel system (symbolically referred to in FIG. 2 as "LPC"). For possible details of this optional connection with the low-pressure part 158, reference may be made, for example, to DE 10 2005 040 918 A1. The fuel as a pollution-reducing medium 132 flows via the supply line 134 via an optional throttling element 160 to the metering unit 138, which is symbolically labeled "MU" in Figure 2. In addition, for example, for example, to the embodiment in DE 10 2005 034 704 A1, optionally optional between the throttle element 160 and the metering unit 138 may be provided a pressure damping volume, which is not shown in Figure 2.

Within the metering unit 138, the shut-off valve 152 first interrupts the inflow of the pollutant-reducing medium 136 during regeneration pauses. If necessary, a pressure relief valve 162 can be accommodated in a branch line 164, similar to the configuration in DE 10 2005 034 704 A1, for example, which includes the supply line 134 Tank 166 connects. In this way, a pressure level can be reduced, and it can be compensated to a limited extent, pressure fluctuations.

In the metering unit 138, downstream of the shut-off valve 152, the first pressure sensor 146 is arranged, the signal of which is used, for example, for calculating the timing of the metering valve 156, and thus for increasing the metering quantity accuracy can. This metered amount is then made available via the metering valve 156 and conveyed to the injection valve 132. Optionally, a second pressure sensor 148 may be arranged between the injection valve 132 and the metering valve 156 as a pressure measuring device, for example for detecting leaks.

The injection valve 132 may, for example, be a structurally adapted fuel injection valve which opens at a certain supply pressure and injects pollutant-reducing medium 136 into the exhaust gas tract. For example, a structurally adapted "K-Jetronic" valve can be used for this purpose.

The device 140 shown in FIG. 2 is modified according to the invention in that at least one pressure damper 168 is provided upstream of the injection valve 132. For example, such a pressure damper 168 may be disposed at one of the locations indicated by A, B or C in FIG. 2 or at several or all of these locations. Alternatively or additionally, an arrangement of such pressure damper 168 is also possible at other locations in the supply line 134.

Embodiments of pressure damper 168 according to the invention, which can be provided for example in a device 140 according to FIG. 2, are shown in FIGS. 3 and 4.

FIG. 3 shows an exemplary embodiment of a pressure damper 168, which acts passively and comprises at least one porous element 170 with open porosity. This porous element 170, which, for example, as described above, may comprise a ceramic, a metal, a metal alloy or a combination of these or other materials, is accommodated, for example, in a pressure housing 172. This pressure housing 172 is integrated into the supply line 134 via an inlet 174 and an outlet 176.

For example, the porous member 170 may have non-linear permeability properties for the polluting medium 136 such that there is a disproportionate ratio between the pressure difference at the inlet 174 and the outlet 176 and the delivered amount of polluting medium 136, for example. This means that pressure peaks can be absorbed by the pressure damper 168 in a particularly effective manner. For example, the excess energy contained in the pressure may be absorbed by the porous member 170.

FIG. 4 shows a second possible exemplary embodiment of a pressure damper 168. In this case, the pressure damper in turn comprises a pressure housing 172, with a Inlet 174 and an outlet 176, via which the pressure damper 168 is integrated into the supply line 134. Inside the pressure housing 172, a hydraulic volume 178 of the pollutant-reducing medium 136 is received, which is connected via a plunger 180 in operative connection with a spring element 182 shown in simplified form as energy storage 184. Instead of a spring element 182, as stated above, for example, other types be used by energy storage. A spring chamber 186, in which the spring element 182 is accommodated, can be depressurized, for example, via a bore, not shown in FIG. Overall, the hydraulic pressure damper 168 shown in FIG. 4 represents an example of a piston-spring accumulator. However, other types of energy accumulators can also be used.

Claims

claims

Claims 1. A device (140) for metering at least one pollutant-reducing medium (136) into an exhaust system, in particular for introducing fuel into an exhaust gas strut (116) for the regeneration of a pollutant-reducing element (130) in the exhaust gas

Exhaust line (116), comprising at least one injection valve (132), in particular a pressure-controlled injection valve (132), and at least one supply line (134) for supplying the pollutant-reducing medium (136) to the injection valve (132), wherein in the supply line (134) upstream of the injection valve (132) at least one pressure damper (168) is provided.

2. Device (140) according to the preceding claim, wherein the pressure damper (168) has at least one in the supply line (134) received porous element (170).

The apparatus (140) of the preceding claim, wherein the porous member (170) comprises at least one of: a ceramic material; a metal, in particular a sintered metal; a metal alloy, in particular a sintered metal alloy; a composite material.

The apparatus (140) of any one of the preceding claims, wherein the pressure damper (168) comprises at least one hydraulic pressure damper (168), the hydraulic damper (168) comprising at least one hydraulic volume (178) of the pollutant reducing medium (136) and at least one from the hydraulic volume (178) different and with the hydraulic volume (178) in operative connection energy storage (184).

5. Device (140) according to the preceding claim, wherein the energy store (184) comprises at least one of the following energy store (184): an at least partially elastically deformable plastic; a spring element (182); a compressible closed fluid volume, in particular a gas volume, in particular air.

6. Device (140) according to any one of the preceding claims, wherein the supply line (134) connects a low-pressure system (158) of a fuel system, in particular a memory injection system, with the injection valve (132).

7. Device (140) according to one of the preceding claims, wherein in the supply line (134) further in front of the injection valve (132) at least one metering unit (138), the metering unit (138) having at least one valve (152, 156) for controlling an injection process of the pollutant reducing medium (136).

The apparatus (140) of the preceding claim, wherein the metering unit (138) further comprises at least one pressure measuring device (146, 148), wherein the pressure damper (168) is disposed upstream of the pressure measuring device (146, 148).

9. Device (140) according to one of the two preceding claims, wherein the pressure damper (168) is fully or partially integrated in the metering unit (138) and / or wholly or partially upstream of the pressure measuring device (146, 148) is arranged.

10. Device (140) according to one of the preceding claims, further comprising at least one pressure relief valve (162), wherein the pressure relief valve (162) in a before the pressure damper (168) from the supply line (134) branching branch line (164) is received.

The apparatus (140) of any one of the preceding claims, further comprising at least one damping volume received in the supply conduit (134) in front of the pressure damper (168), comprising a damping reservoir of the pollutant reducing medium (136).