DE3310933A1 - Device for removing solids from the exhaust gases of internal combustion engines - Google Patents

Abstract

A description is given of a device for removing solid constituents from the exhaust gases of internal combustion engines, in which large formations of solid constituents are produced with the aid of a coagulator (5) and these are separated from the exhaust gas in a downstream separating device (6) and discharged into a storage container (8), from where the solid constituents are fed back to the suction side of the internal combustion engine by carrier media during selected operating conditions of the internal combustion engine. It is advantageously possible by virtue of this device to continue to separate solid constituents from the exhaust gas even in full-load operation without feeding these constituents back directly to the suction side during exhaust-gas recirculation and there impairing combustion or the performance of the internal combustion engine. If fresh air or a liquid or gaseous medium participating in the combustion in the combustion space of the internal combustion engine is used as the carrier medium for the particulates, the particulates can also be fed to the engine for combustion at full load. …<IMAGE>…

Description

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16.3.19Ö3 Bö / Yes

Robert Bosch GmbH, TOOO Stuttgart 1

Device for removing solid components from the exhaust gases of internal combustion engines

State of the art

The invention is based on a device according to the preamble of the main claim. DE-OS 30 U1 070 is a such facility known. The subject of this application is based on the principle that the exhaust gas from the internal combustion engine is divided into two substreams, one of which is enriched with the solid components or the soot and the other is largely freed from the solid components and the soot. The one enriched with soot Partial exhaust gas flow is returned to combustion as part of the exhaust gas recirculation of the internal combustion engine fed. A vortex separator from durch is used as a separating device for the division into two exhaust gas flows DE-PS 21 60 U15 known design used. These However, the device disclosed has the disadvantage that no exhaust gas recirculation is possible at full load. To this Purpose is suggested there, with full load operation through the exhaust gas partial flow enriched with soot for cleaning instead of sending a solids filter to the suction side of the internal combustion engine.

DE-PS 28 33 U81 a device is similar Design known, but in which the exhaust gas is passed into a cyclone in which the solid components or the

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Soot of the exhaust gas is to be deposited. In this known device, the funnel end of the cyclone is provided with a metering device and is connected to an exhaust gas recirculation line. According to the exhaust gas opacity, the metering valve is controlled by the known device so that the exhaust gas recirculation amount with which the separated soot is transported is between 2 % at full load and a maximum of 50 % at part load. When using such a cyclone, however, its functionality is no longer guaranteed if exhaust gas recirculation is to be completely interrupted when the internal combustion engine is operating at full load. With such devices, the soot then escapes with the exhaust gas.

Advantages of the invention

The device according to the invention with the characteristic Features of the main claim has the advantage that cleaning is also carried out during long periods of full-load operation of the exhaust gas can be made and the soot emissions in the environment is reduced. The soot becomes advantageous buffered during these operating times and can then be disposed of during partial load operation fed back to the internal combustion engine together with exhaust gas as an exhaust gas recirculation quantity for post-combustion will.

It is also particularly advantageous that according to the one Embodiment of the invention, the excreted soot or the excreted solid constituents with fresh air are supplied as a carrier medium of the internal combustion engine. The exhaust gas load on the engine's operating mixture is kept very low, see above that even when operating at full load, soot of the combustion

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engine are fed back for post-combustion can without this having significant disadvantages on the combustion process of the internal combustion engine.

The device is particularly effective when a separating device according to claim 6 is used as the separating device and the soot content in the exhaust gas is formed into large particles by coagulation in a device according to claim 7 «

The measures characterized in the other subclaims result in advantageous developments of the im Main claim given solution claimed.

drawing

Three exemplary embodiments of the invention are shown in the drawing and are explained in more detail in the description below. 1 shows a first embodiment with disposal of the reservoir via an exhaust gas recirculation line, Figure 2 shows a section in a first plane by a separation device of the type used in the embodiment according to Figure 1, Figure 3 k a second section through the separating device according to Figure 2, Figure a Embodiment of a device for the coagulation of soot components upstream of the separating device according to FIG. 1, FIG. 5 a second exemplary embodiment with disposal of the storage container of the separating device by fresh air flowing through and FIG the separated solid constituents to be discharged, even a gas connection between the line carrying the carrier medium and the separating device is prevented.

Description of the exemplary embodiments

In Figure 1, an internal combustion engine 1 with a suction ' pipe 2 and an exhaust pipe 3 shown schematically. In the exhaust pipe 3 there is a coagulator 5 of the following described in more detail design and function arranged. A separating device is also connected downstream of this in the exhaust pipe 6, from which the exhaust pipe opens out into the open via a silencer, if necessary. the Embodiment of the separating device is in one embodiment shown in Figures 2 and 3 and will be described in more detail below. The in Figure 1 The separating device 6 shown schematically has a storage container 8 for the deposition of separated solid components of the exhaust gas. At a suitable point, in particular at the lowest point of the storage container, an emptying opening 9 is provided, the a valve 10 is connected immediately downstream. This valve 10 can preferably be controlled electrically by an electrical control device 12. An exhaust gas recirculation line 1U connects to the valve, which for Intake pipe 2 of the internal combustion engine leads. In the design According to Figure 1, exhaust gas is emitted by the internal combustion engine 1, especially if it is a self-igniting internal combustion engine is, has solid impurities such. B. Soot particles. These soot particles are usually very finely distributed in the exhaust gas, which leads to the elimination of the soot components would make fine filters necessary. Such filters then clog very quickly and increase the flow resistance in the exhaust system and thus the proportion of internal exhaust gas recirculation and are very quickly unusable. In particular such filters have to be serviced very frequently

are and are accordingly complex and susceptible. With the still to be described coagulator 5, however, it is possible to combine the fine soot constituents to form larger soot flakes, which are thus easier to separate out. Instead of filters, in the embodiment according to FIG. 1, a separating device is used according to the invention, which works essentially as a centrifugal separator. There the large soot flakes are collected in the storage container 8 and can then be fed back to the suction side of the internal combustion engine via the exhaust gas recirculation line 1 k. These soot particles are burned in the combustion chambers of the internal combustion engine. However, since exhaust gas recirculation is not possible in all operating areas of the internal combustion engine, valve 10 is provided in exhaust gas recirculation line lh , through which the exhaust gas recirculation line can be blocked, but which can also be used to control the proportion of the recirculated exhaust gas in the total intake volume of the internal combustion engine. In particular when operating at full load, the internal combustion engine should provide full power and, for this purpose, is often already supplied with a fuel-enriched operating mixture. Exhaust gas recirculation in this operating range must therefore be prevented. However, it is precisely in this operating range that the risk of increased soot formation is great, particularly in the case of compression-ignition internal combustion engines, so that solid constituents or soot are increasingly separated out by the separating device. According to the invention, this precipitated amount is temporarily stored in the storage container 8 and can be discharged again via the exhaust gas recirculation amount when the internal combustion engine changes to partial load operation.

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By the control device, the valve 10 is opened or closed on the one hand depending on the load and it is the amount of recirculated exhaust gas is also metered depending on other operating parameters. For the Opening and closing of the valve can also be used with additional parameters, such as: B. the operating temperature the internal combustion engine or the idle mode of the internal combustion engine, where there is too high a Exhaust gas recirculation rate can also have a negative impact.

Figures 2 and 3 show a cross section and a longitudinal section through the separating device 6, which is also shown schematically here. A circular cylinder 17 is arranged in a housing 16, with a smaller longitudinal extension than the housing (FIG. 3). Coaxially to the axis of the cylinder 17, dip tubes 18 and 19 protrude symmetrically into the cylinder from both sides, which penetrate the wall of the housing 16 after leaving the cylinder and, optionally after being merged as an exhaust pipe, open out into the open or in an exhaust silencer. Instead of the end face of the cylinder, a closing disk 20 and 21 are provided in this plane, which are carried by the immersion tubes 18 and 19 and which are circular and concentric to the cylinder 17 and leave an annular gap 23, 2h towards the outer surface of the cylinder , via which the interior of the cylinder 17 is connected to the interior of the housing 16. Furthermore, a channel 25 with a rectangular cross section opens into the housing 16 and is connected to the exhaust pipe downstream of the coagulator. The rectangular channel extends over the entire length of the cylinder 17 and opens into it tangentially. At the entrance of the channel 25, the radial

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inner leading edge formed as an inflow lip 26, which slightly reduces the cross section of the rectangular channel 25 at the entrance to the circular cylinder 17. The bottom 28 of the housing 16 below the cylinder is funnel-shaped and at its lowest point has the drain opening 9, which is followed by the valve 10. Such a separating device is already known from DE-OS 28 32 097.

The separating device works as follows: The exhaust gas enriched with large, flaky soot parts enters the circular cylinder 17 through the rectangular duct 25 and generates a rotating vortex in it, the vortex rotation being accelerated by the inflow lip 26. The exhaust gas in the circular cylinder 17 is thus brought into high rotation so that the soot constituents are carried outwards to the radial wall of the cylinder 17 under the action of centrifugal force. In the depression of the vortex, the purer exhaust gas is discharged to the outside via the dip tubes 18 and 19. The solid components rotating along the radial wall of the cylinder 17, the large flaky soot parts, can exit the cylinder 17 via the slots 23, 2k and sink in the calmed gas medium to the funnel-shaped bottom 28 of the housing. This collecting space is the storage container denoted by 8 in FIG.

The function of this device is advantageously independent of whether it is now via the emptying opening 9 Soot is discharged or not. Due to the soot components flowing in again and again, they are in the Soot parts located near the radial wall of the cylinder 17 are constantly pushed outwards in the axial direction regardless of the pressure inside the housing 16.

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Excretion is all the more effective the greater the the exhaust gas transported "solid ingredients. A coagulator to increase the solid components, the embodiment according to have FIG k. The coagulator there is schematically shown" consists of a first hollow cylinder 29 made of electrically conductive material and a coaxially to the first hollow cylinder 29 in this arranged second hollow cylinder 30 of smaller diameter and also made of electrically conductive material. The end faces of the first hollow cylinder are closed by disks 31 and 32 made of insulating material and also serve to hold the second hollow cylinder 30. The exhaust pipe 3 opens at one end of the first hollow cylinder 29, which exits again at the opposite end of the first hollow cylinder 29 and becomes the separating device 6 leads. The first hollow cylinder 29 serves as a first electrode and is connected to ground and the second hollow cylinder 30 serves as a second electrode and is connected to the positive pole of a high voltage source. An electric field thus arises between the two hollow cylinders, but this field is not so strong that a corona discharge occurs between the two electrodes or that the exhaust gas flowing in the annular space between the two electrodes is ionized. Due to a high field strength, however, a charge shift occurs on electrically conductive particles as a result of influence, as a result of which the soot particles become dielectric or are converted into electrical dipoles 33. The electric field also aligns the now dielectric soot components along the field lines and polarizes them uniformly, with the result that individual soot particles can attach themselves to one another under the effect of their electrical attractive forces and can form into larger soot flakes. The influence or polarization phenomenon on the soot particles 33 is stronger the larger

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the dielectric constant or the better the conductivity of the soot particles and the higher the applied Field strength E is. Such a coagulator has the advantage that almost no current flows between the electrodes and the device is thus almost without power consumption is working.

In addition, the electric field can be superimposed with a sound field that can be generated with a sound generator 3h. This sound field also causes the soot particles to oscillate, which can increase the extent of the coagulation processes. The effectiveness of the coagulator 5 can furthermore be increased in that part of the exhaust gas quantity leaving the coagulator is returned to the inlet of the exhaust gas pipe 3 in the hollow cylinder 29 via a return line 35. To generate a flow, the exhaust pipe at the inlet of the return line 35 is advantageously designed as a Venturi pipe 36.

The embodiment according to FIG. 5 shows schematically a modified version compared to the embodiment according to FIG Execution. While in the embodiment according to Figure 1, the soot precipitated from a carrier medium in the form of exhaust gas recirculation was transported to the suction side of the internal combustion engine 1, advantageously the exhaust gas recirculation amount was removed from the separating device, according to the embodiment according to FIG Separating device β are traversed by fresh air and the soot is fed to the suction side by fresh air quantities For this purpose, branch off from a fresh air duct 38 from an air bypass line 39 which opens on one side into the storage container 8 and over it its emptying opening 9 leaves again. After leaving

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A valve 10 is also arranged from the reservoir 8 in the bypass line 39, which is operated by an electrical Control device 12 'is controlled. To generate a flow in the bypass line 39 is the Fresh air line 38 preferably in the area of the confluence the bypass line 39 designed as a Venturi tube ^ O .. The valve 10 can be controlled as a function of the load by the electrical control device 12 ′ be, in contrast to the embodiment according to Figure 1 with an exhaust gas recirculation also in full load operation with Soot-laden fresh air can be supplied to the engine, since only insignificant amounts due to the additional combustion of the soot Amounts of oxygen are required and therefore the combustion process is not impaired.

A further embodiment is roughly shown schematically in FIG. 6 Here the emptying opening 9 ′ of the storage container 8 opens directly into a fresh air line kl , which, as in the exemplary embodiment according to FIG. 5, leads to the suction side of the internal combustion engine 1. In the fresh air line kl , a valve k2 is arranged, which is controlled in a manner comparable to that in the exemplary embodiment according to FIG. 5 by an electrical switching device 12 ″. The emptying opening 9 'is designed as an injector sluice in the exemplary embodiment according to FIG. 6, in such a way that the soot is discharged from the storage container 8 by the amount of air flowing past the opening. The soot collects at the lowest point of the storage container 8 and closes the emptying opening 9 'so that an outflow of exhaust gas into the fresh air line kl is largely prevented. The connection between storage container 8 and fresh air line it-1 can also be through other known locks, such as. B. cell wheel sluices take place.

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Instead of disposing of the storage container by discharging the precipitated solid components in fresh air or recirculating exhaust gas as a carrier medium, it is also possible as a carrier medium also a liquid that takes part in the combustion in the combustion chamber of the internal combustion engine or to use gaseous medium. This can e.g. B. be a liquid or gaseous fuel in which the Soot components are transported dissolved and according to the operating requirements of the internal combustion engine is allocated.

Claims (11)

1 6.3.1983 Bö / Jä Robert Bosch GmbH, 7000 Stuttgart 1 Expectations Iy device for removing solid constituents, in particular soot constituents, from the exhaust gases of internal combustion engines with a separating device through which the exhaust gas flows through which the solid components contained in the exhaust gas are separated and can be returned to the suction side of the internal combustion engine for disposal, characterized in that the separating device (6) has a storage container (8) for receiving the separated solid components and the device has a control device (12, TO) through which an emptying opening (9) of the storage container (8 ) can be connected to a line (1t, 39, 38, kl) leading to the suction side (2) of the internal combustion engine and additionally conducting a carrier medium. 2. Device according to claim 1, characterized in that the storage container (8) in a fresh air line (39) is arranged, the outlet of which on the storage container is designed as its emptying opening (9) and which can be shut off by a valve (1O) controlled by the control device (12) and to the suction side of the internal combustion engine leads. 3. Device according to claim J, characterized in that the storage container (8) can be emptied via a sluice serving as an emptying opening, in which a gas connection between the storage container and line k 1 can be prevented by the amount of solid constituents to be discharged in the storage container (8) and the line, as a carrier medium, leads fresh air to the intake side of the internal combustion engine. k. Device according to Claim 1, characterized in that exhaust gas can be fed to the suction side of the internal combustion engine as the carrier medium through the line (1U). 5. Device according to claim 1, characterized in that one in the combustion chamber of the internal combustion engine through the line is liquid participating in the combustion process. 6. Device according to one of the preceding claims, characterized in that the separating device (6) a known device is used, which works on the principle of centrifugal separation. 7. Device according to claim 6, characterized in that that the separating device has a circular cylinder (17) into which the exhaust gas stream opens tangentially and on the end faces of which dip tubes (18, 19) immersing coaxially into the circular cylinder are provided for the Outlet of purified exhaust gas and that in the area of the circumferential radius of the circular cylinder outlet openings (23, 2U) for discharging soot parts in a storage container (8) are provided. 1846 - 3 - ■ 8. Device according to one of the preceding claims, characterized in that the separating device (6) a device (5) to enlarge the solid constituents (coagulator) carried in the exhaust gas is connected upstream is " 9. Device according to claim 8, characterized in that the coagulator consists of an exhaust gas guide device (29 _S 30) with an electric field, the field strength of which is below the ionization field strength and that through the electric field the solid components carried out through the exhaust gas guide device become electrical by influence Dipoles are polarizable. 10. Device according to claim 9 _S, characterized in that a return line (35) is arranged from the outlet of the exhaust gas guiding device (29, 30) to the inlet thereof. 11. Device according to claim 9 or 10, characterized in that the electric field is a sound generator (3 * 0 is assigned by the one in the exhaust gas control device effective sound field can be generated.