JPH01125513A - Soot grain removing filter for exhaust gas - Google Patents

Abstract

PURPOSE: To remove soot particles in exhaust gas and combust deposited soot particles automatically by constituting a filter with a filter medium wrapped around the outer periphery of a pipe having a plurality of apertures in a container. CONSTITUTION: A filter 1 interposed in an exhaust system in a diesel engine comprises a container 4 concentrically surrounding a meshed pipe 5. The pipe 5 is connected to an inlet support portion 3 and an outlet support portion 6. A filter medium 7 wrapped around the pipe 5 completely fills the space between the container 4 and the outer surface of the pipe 5. During engine operation, the soot in the exhaust gas exhausted by the engine enters the filter medium 7 through meshes 8 of the meshed pipe 5 and is deposited there. The deposited soot is combusted automatically in the filter medium 7.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a filter for removing soot particles from the exhaust gas of a diesel engine and a method for reducing the emission of soot particles.

[Prior art]

It is well known to use mechanical filters to filter exhaust gas streams to reduce the emission of soot particles, which are highly harmful and environmentally troublesome. The soot particles deposited on the filter are incinerated by the heat of the exhaust gas, producing harmless carbon dioxide (CO2).
) can be changed to Mechanical filters generally result in permanent pressure and efficiency losses due to interruption of exhaust gas flow. It not only results in efficiency loss but also leads to engine stalling. To compensate for this drawback, additional fuel is supplied to increase the exhaust gas temperature (see: Diesel Engines - Reducing Automotive Exhaust Gas Emissions Report of the German Society of Engineers (VDI) 559° VDI-Publisher, Düsseldorf, 139- 156 pages).

Gravity separation is particularly known for reducing soot emissions.

This presupposes an increase in the number of electrostatically charged soot particles. The electrostatic field then acts to agglomerate the soot particles, and the rounded soot particles are collected in a container. The collected soot is finally channeled into the engine's combustion chamber where it is burned. Effective reduction of soot in the flue gas requires a corresponding capacity to take into account the amount of soot that falls into the collection vessel,
Due to lack of space and free space, diesel cars
The installation of collection containers is often very expensive and unrealized.

German Patent Application DE-O8 3324886 discloses that an exhaust gas stream containing harmful substances contained in the exhaust gas stream, such as soot particles, in particular, is guided through a container configured as a ground electrode, the container being The cleft representing the coaxial second electrode may be shown to contain a hollow conductor with eyes. A first electrode in the form of a conductive wire extends through the hollow conductor. The voltage potential charged to the first electrode is higher than that of the hollow conductor. very small, contained in a gas stream
The finely dispersed soot particles are rolled into large agglomerates under the influence of the electrostatic field between the container and the hollow conductor, the agglomerates move in the direction of the hollow conductor, and the fissures inside the hollow conductor appear above the eyes. Get into it. The movement and penetration of soot particles in the hollow conductor is increased by the 111th pole, which has a large potential with respect to the hollow conductor.

In the hollow conductor, a second simultaneously outwardly directed electric field mainly occurs, whose spacing is also high and the strength of tJI dominates the center of the hollow conductor, that is, the surface of the wire-shaped first electrode,
The first electrode attracts charged soot particles. The gas stream facing the exhaust gas stream flows through the hollow conductor, carrying the agglomerates concentrated therein and sent for later combustion in the combustion chamber of the diesel engine. An auxiliary soot collection vessel is not required in this known exhaust gas purification system. Moreover, there is still a great danger that, in addition to the soot particles, rust particles, which are separated at the same time, will arrive at the exhaust outlet in the combustion chamber of the engine. This ultimately shortens the life of the engine,
Leads to engine destruction.

The object of the present invention is, inter alia, to provide a method and a filter for the removal of soot particles from the exhaust gas stream of diesel engines, moving or stationary, without the aforementioned disadvantages and with substantially improved efficiency.

This object is achieved according to the invention by providing in a container a tube with a perforated jacket surface and surrounded by a filter material through which the exhaust gas flows. The perforated tube is preferably constructed as a mesh tube. The present invention is characterized by the fact that the soot particles are accelerated radially outward in the exhaust gas system together with the exhaust gas stream by pulsations, and by means of a jacket tube with very large holes that are almost completely open. A mesh tube with a mesh width of wire diameter 0.6jem extends over the entire circumferential area of the tube and directly surrounds the mesh tube. This is based on the confirmation that it does not prevent soot particles from penetrating the filter media present in the tube jacket surface and does not prevent them from being deposited there. Examples of filter media include steel wire,
Compressed porous materials such as ceramics and mineral foams are suitable. The invention is based on the consideration that the exhaust gas flowing out of the combustion chamber of a diesel engine contains ionized soot particles which accelerate their penetration into the filter media directly adjacent to the pipes. The kinetic energy of the soot particles supports the combustion of the soot particles that are deposited in the filter media or stored intermediately when they collide with the filter media and on the already deposited particles. The automatic regeneration of the filter is facilitated by the combustion of soot particles in the intermediate section, especially by the heat present in the exhaust gas.

The combustion temperature of the deposited soot is advantageously lowered by the catalytically coated filter material.

The removal of soot particles and thus the reduction of soot emissions is achieved by means of the filter according to the invention without forced flow through the filter medium and without pressure losses, since the flowing exhaust gas encounters little resistance in the pipes. Due to the automatic combustion of the soot deposited on the filter media out of the exhaust gas stream, it does not create blockages that particularly affect the efficiency of the engine. The filter material surrounding the mesh tube exhibits significant deposition capacity when there is no immediate soot combustion and does not impede the flow cross-section for the exhaust gas flow in the tube. Although exhaust gas back pressure reduces efficiency, it does not constitute an exhaust gas back pressure here.

It has been shown that it is particularly advantageous to wrap the filter material with three times the mesh tube.

A diesel engine with an exhaust system that has a small structure is prepared with a filter.

In the case of a corona discharge electrode that is led through a grounded vessel and tube, the electrode is advantageously formed as a metal conductor stretched between insulators placed at the inlet and outlet of the tube, so that the static i ! With the aid of field-based separation, the degree of release is optimized, and with the energy supply from the electrostatic field, the charging and combustion of the soot particles is facilitated by the branching surrounding area of the soot particles, in that way acting on the tube envelope surface. occurs. The filter container of an intermittent engine is earthed, for example by means of a ground connection. Experimental confirmation has shown that electrostatic separation increases the efficiency of self-regenerating filters by up to 90%. For safety reasons, the movement of the soot particles separated during the installation of a pulsating DC voltage on the corona discharge electrode is preferably supported in the direction of the jacket surface of the mesh tube, which serves as collector electrode. From there, the soot particles of the exhaust gas flowing through the mesh tube and the jacket surface migrate into the enclosed filter material and are deposited there. In a filter with an electrostatic field, the diameter of the area surrounded by the filter material is smaller than in a filter performed without electrostatic separation on a perforated tube.

It is recommended that the voltage charged to the corona discharge electrode be negative. A negative voltage may produce a substantially larger corona in the multi-wire corona discharge electrode than a positive voltage. The pulsating DC voltage is supplied using a transformer and is supplied along with the current from the car battery. The required current strength is very small, about 4 to 5 μm, and is a negligible load on the motor vehicle's electrical equipment. High voltages do not have to exceed about 10 KV and can be achieved without problems and without danger, and the ozone produced in high voltage fields particularly affects the chemical reaction of ionized soot particles, thus reducing the amount of deposited soot to harmless carbon dioxide. Promote combustion.

The invention proposes that a spring be applied to the metal conductor. A tension or compression spring holds down the metal conductor,
It is strung with conductive wire, the diameter of which does not exceed 0.3 m. That is, the spring adjusts the elongation of the conductor, which may be caused by the heat of the exhaust gas. For example, the spring is placed between the insulator and the end of the conductor, or acts on the movable insulator socket of the movable filter container. Since the insulator socket is placed out of the hot gas stream, the spring is not retracted.

The insulators that fix the metal conductors are arranged both vertically and horizontally. The insulator has a length in each case such that the walls of the filter vessel avoid breakdown due to leakage of the corona discharge electrode.

The container can support and connect the inlet and outlet tubes in a right-handed eccentric arrangement. The mesh tube may for example be attached to or interlocked with the end. Eccentric positioning is particularly suitable for horizontally disposed insulators. It is easy to assemble and disassemble for horizontal insulators, and in eccentric positions, ie outside the exhaust gas, the mesh tube and the inlet and outlet tubes are not aligned.

The mesh tube advantageously forms a narrow longitudinal joint projecting radially outward. A technologically advantageous manufacturing method for the mesh tubes is to manufacture them from commercially available mesh mats. The outwardly directed longitudinal seams allow the interior of the tube to achieve a smooth internal jacket surface in the corner areas of the mat seams forming the tube. Voltages and transitions due to spark discharges are not relevant and do not occur at the corners of overlapping seams.

A method for reducing soot emissions in the exhaust gas stream of a diesel engine is proposed. The pulsating flow of exhaust gas through the filter is subjected to an electrostatic field along with the soot particles it contains, which charge the soot particles and accelerate them radially outward, depositing soot into the filter layer. It has been proposed to deposit particles and also periodically auto-combust them.

The soot particles are therefore deposited centrally in the encased filter medium, guiding the exhaust gas flow by means of pulsations matched to the gas flow together with the action of an electrostatic field. The energy supply from the electrostatic field, the heat of the exhaust gas, the ozone generated by the high voltage and the oxidized substances present in the gas stream effect the automatic combustion of the deposited soot. The voltage in the electrostatic field can advantageously be varied depending on the engine drive. The full consumption load of the engine is 4 degrees higher than the partial load drive. With favorable combustion conditions therefor, the energy supply from the electrostatic field and therefore the low electrical efficiency of about 50 W can be further reduced considerably.

Next, the present invention will be explained in more detail with reference to embodiments shown in the drawings.

FIG. 1 is a vertical joint view of the filter. Exhaust gases emerging from an internal combustion engine, not shown here, are led in the direction of the arrow 2 via an inlet support to a filter.

The filter 1 is a container 4 that is concentrically wrapped around a mesh tube 5.
It consists of A tube 5 extends throughout the container and connects to an inlet support 3 and an outlet support 6 placed opposite it. The tube 5 is encased in a filter medium 7, so that the space between the container 4 and the jacket surface of the tube 5 is completely filled with the filter medium. In this method, the filter 1 of the inlet and outlet supports 3, 6 provides a restricted flow of exhaust gas to the filter medium 7 due to the pulsations produced by the exhaust device. In this case, the soot particles present in the exhaust gas pass through the mesh 8 of the mesh pipe 5 and enter the filter medium, where they are deposited. The deposited soot particles are automatically combusted in the filter medium, so that the exhaust gas leaving the filter via the outlet support 6 is free of soot particles.

In the filter 101 shown in FIGS. 2 to 4, exhaust gas is introduced into the filter 101 from the direction of the arrow 102 through the inlet support 103 and is assisted by an electrostatic field to deposit soot particles on the filter medium 107. Filter 101 is grounded for this purpose. In other words, metal conductor wire 1
It has a container 9 to which two terminals 10, 11 are connected in order to equip the corona discharge electrode in the form of 2 with a pulsating DC voltage.

The metal conductor 12 extends longitudinally through the mesh tube 105 and is fixed to an insulator 13 arranged perpendicularly to the outlet of the inlet support 103 or the outlet support 106 . The corona emitting mW pole 12 is stretched between the intermediate socket 14 and the insulator 13 fixed to the container 9. Stretching of the corona discharge electrode 12 caused by the hot exhaust gas flow is compensated for in the embodiment according to FIG. 2 by a spring 15 arranged in the region of the inlet support 103. Do not apply a shock to the insulator 13 to which the current is connected. The insulator 13 is rotatably supported on the semicircular cap-shaped base of the socket 14.

When the corona discharge electrode 12 expands, the cap 18 of the insulator 13 is supported, and the spring 15 presses the insulator 13 to a position that balances the expansion. Due to the electrostatic field limited by the voltage charging the corona discharge electrode 12, the soot particles guided along with the exhaust gas stream 102 through the inlet support 103 to the filter 101 are strengthened to move in the direction of the mesh 108 of the tube 105, and the mesh 108 is Penetrate filtration 4110
7 and the soot particles deposited on the filter are deposited until they are burned and regenerated.

Deposited soot burns into harmless carbon dioxide gas.

The automatic regeneration filter 101 shown in FIG. 3 has an electrostatic internal division 111i function, and the filter 101 according to FIG.
is the insulator 113 into which the corona emission electrode 12 is fitted.
It is advantageous in that it is arranged horizontally. Insulator 113
are arranged in the kill tube 16 and are joined to the front surface of each container 9 via flanges with bolts 17. Ki 1
? The tube 16 is provided with an inlet support 103, an outlet support 106 and an inlet tube 19 and an outlet tube 20 arranged eccentrically opposite each other in each support 103,106.

The mesh tube 105 has an inlet support 103 as shown in FIG. 4, with its end inserted over the support 103.106. A spring 15 is supported on the insulator 113 to compensate for the automatic extension of the corona radiation I& The spring presses against the washer 21 the end of the corona discharge 7tf pole 12 which is guided through the insulator 113. The mesh tubes 5, 105 shown in FIG. 5 project outwardly, effectively forming a narrow longitudinal seam 22, and have seam corners 23 bent laterally. With a longitudinal seam 22, the mesh tube 5.105 is fixed on the corner 23 of the seam, for example with the inlet support and the outlet support 3, 6, 103.degree. 106 fitted into the seam.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal section through a filter wrapped with a filter medium according to the invention and has a perforated exhaust gas pipe; FIG. 2 is a longitudinal section through a first structure of a filter according to the invention with combined electrostatic separation; 3 is a longitudinal sectional view of a second structure of the filter according to the invention with a horizontal arrangement of the insulators modified with respect to the structure according to FIG. 2; FIG. 4 is a detailed view of the filter according to FIG. 3; , FIG. 5 is a detailed perspective view of the m-shaped seam of the present invention. 1.101... Filter, 2,102... Exhaust gas sending direction, 3,103... Inlet support part, 4,9...
- Container, 5,105...Mesh pipe, 6.106...Outlet support part, 7. ．． 107...Filtering material, 8,108...
・Mesh, 10.11...Terminal, 12...Gold IiI conductor wire, 13,113...Insulating material, 14...Socket,
15...Spring, 16...Cap, 17...Bolt, 21...Wash p, 22...Longitudinal joint,
23...Edge of bent seam.

Claims (1)

[Claims] 1. In particular, in a filter for removing soot particles from the exhaust gas of a diesel engine, a perforated jacket wrapped in a filter material (7, 107) in one container (4, 9) A filter for removing soot particles from exhaust gas, characterized in that it has a pipe (5, 105) having a surface, through which the exhaust gas flows. 2. The filter 3 according to claim 1, characterized in that the pipe is a mesh pipe (5, 105) arranged in the container (4, 9), the filter medium is a catalyst. 3. A filter according to claim 1, characterized in that it is a filter medium (7, 107) which is coated with a coating. 4. The tube wrapped with the filter material is at least a mesh tube (5.
4. A filter according to any one of claims 1 to 3, characterized in that it has a diameter three times larger than 105). 5. Any one of claims 1 to 4, characterized in that the container is a grounded container (9) and there is a corona discharge electrode (12) led through the tube. Filter by one or more. 6. As the corona discharge electrode, a metal conductor (1
2) The filter according to claim 5, characterized in that the filter is provided with: 7. A filter according to any one of claims 5 and 6, characterized in that it is provided with a spring (15) acting on the metal conductor (12). 8. Filter according to any one of claims 1 to 4, characterized in that the insulator (13) is arranged perpendicularly to the tube. 9. Filter according to any one of claims 5 to 7, characterized in that the insulator (13) is arranged horizontally with respect to the tube. 10. Claims 1 to 9, characterized in that the inlet pipe (19) and outlet pipe (20) for flowing the exhaust gas are provided eccentrically with respect to the container (49). Filter by one of the following. 11. Claims 1 to 10, characterized in that the mesh pipe (5, 105) projects outward in the radial direction and has a narrow longitudinal joint (22). A filter according to any one of the above. 12. A filter according to any one of claims 5 to 11, characterized in that the corona discharge electrode (12) is charged with a pulsating DC voltage. 13. The filter according to claim 12, characterized in that the voltage charged to the corona discharge electrode (12) is negative. 14. In particular, in a method for reducing medium emissions in the exhaust gas stream of a diesel engine, an exhaust gas stream pulsating through a filter (101) having soot particles contained in said exhaust gas stream is guided through an electrostatic field. , radially outwardly to deposit soot particles into said filter layer (107), said soot particles being periodically and simultaneously automatically combusted. Particle reduction method. 15. Claim 4, characterized in that the voltage in the electrostatic field changes depending on the driving of the engine.
The method described in section.