Patent Application
20060117743
The invention relates to a particle filter, especially for exhaust gases of diesel-fuelled internal-combustion engines, with a plurality of filter walls to be flowed through by the fluid for separating particles from a fluid stream, where the filter displays an inflow side and an outflow side and can be flowed through by the fluid in one direction of flow.
Particle filters of this kind are known in a wide variety of embodiments. The regeneration of particle filters of this kind, especially when used as soot filters in the automotive sector, is relatively complex and requires the vehicle to spend a period of time in a workshop. For regeneration, the filter is initially burnt out in order to preferably incinerate all constituents, one area of the filter first being heated to the necessary temperature so that the glowing area then spreads independently through the filter, ultimately encompassing the entire filter volume. The ash is subsequently blown out of the filter in the direction opposite to that of the fluid to be cleaned. In this context, regeneration of the filter must be carried out on a separate regeneration bench in order to perform process control, to generate the high pressure for the purging gas, which is forced through the filter on the exhaust side, and to collect the remaining ash.
The object of the invention is to create a particle filter in which regeneration can be performed more simply and, possibly, more quickly.
This object is solved by providing a particle filter in which the purging fluid stream is passed in a direction transverse to the direction of flow of the fluid to be cleaned, to which end flow ducts for the purging fluid are provided that extend over part, or essentially all, of the width of the filter body. The filter body can, for example, be constructed of filter walls stacked in a preferred direction, as a result of which cubic or prismatic filter bodies, in particular, can be constructed, or also of filter walls arranged radially about an axis, as a result of which cylindrical or semi-cylindrical filter bodies can be created.
Owing to the purging fluid being passed in a stream transverse to the fluid to be cleaned, regeneration can be performed with a relatively low purging fluid pressure and, where appropriate, also during continuing operation of the device or system generating the particle-laden exhaust-gas stream, since the purging fluid no longer has to work against the pressure of the fluid to be cleaned, or the device or system does not have to be shut down beforehand. As a result of this, regeneration can, for example, be performed on the respective motor vehicle independently of a workshop. Further, the purging fluid stream can preferably enter into laterally open flow ducts or filter pockets for the fluid to be cleaned, this avoiding a pressure loss of the purging fluid, at least on the inflow side, since it no longer has to flow into the filter body through a particle-tight filter wall. Further, the purging process can be performed particularly effectively owing to the fact that the purging fluid is passed through flow ducts extending virtually over the entire width of the filter body. Further, owing to the assistance of the purging fluid stream transverse to the direction of flow of the fluid to be cleaned, the heating phase for incinerating the filter residue can be carried out particularly easily, since burning out is now no longer impeded by filter walls. This greatly facilitates regeneration of the particle filter as a whole.
The purging fluid flow ducts are preferably designed to extend continuously through the filter body.
Particularly preferably, slit-like ducts are provided for the fluid to be cleaned, extending over essentially the full length of the filter body in the direction of flow and/or its width, this also permitting particularly effective regeneration.
The mean slit height of the purging fluid ducts transverse to the direction of flow of the fluid to be cleaned can be ≧10%, preferably ≧25% to 50%, particularly preferably ≧75% or approx. 100% of the mean or maximum spacing of the filter walls in their stacking direction. In this context, the term “stacking direction” refers merely to the succession of filter walls, and is independent of the manufacturing process, meaning that it also encompasses cylindrical filter bodies in which the filter walls follow on from each other in the circumferential direction. In the case of cylindrical filter bodies, the mean or maximum filter wall spacing at the level of half the filter diameter can be used accordingly.
It goes without saying that the duct or slit height of the filter pockets, which are formed by adjacent filter walls and through which the fluid to be cleaned flows into the filter body, can be constant in the direction of flow, or can increase or decrease towards the outflow end.
Especially if they are of slit-like design, the flow ducts for the fluid to be cleaned preferably display a height a >0 at the outflow end, for example ≧10%, preferably ≧25% to 50%, particularly preferably ≧75% of the mean or maximum height of the flow ducts or filter pockets in the direction of flow.
A particularly simple design of a filter body is obtained if the latter consists of a strip of filter material deposited in meandering fashion, as a result of which the filter can be manufactured not only inexpensively, but also with great tightness and high stability, especially also when exposed to varying thermal and/or mechanical loads. Therefore, the deflection areas preferably display a certain web height in order to already create a certain slit height in the deflection areas. The above data for height a of the flow ducts or filter pockets on the outflow side can apply accordingly to the web height.
The purging fluid inlet opening is preferably located on a side of the filter body other than the inflow and outflow side of the filter, preferably on a side surface of the filter. Further, the purging fluid outlet opening is preferably located on an outer surface of the filter other than the inflow and outflow side of the filter for the fluid to be cleaned. In particular, the purging fluid inlet opening and purging fluid outlet opening can be located on opposite sides of the filter, particularly each on a lateral side surface of the filter, without being limited to this. Where appropriate, either the purging fluid inlet opening or the purging fluid outlet opening can also be located on the inflow side of the filter body, or identical to the inflow opening for the fluid to be cleaned.
The purging fluid duct preferably extends through the filter in such a way that it covers the entire filter over the shortest possible flow path in a direction transverse to the direction of flow of the fluid to be cleaned.
Preferably, each of the filter pockets, which are open on the inflow side relative to the fluid to be cleaned and are formed by opposite filter walls, is assigned a purging fluid flow duct, in which the purging fluid can pass through the filter transverse to the direction of flow of the fluid to be cleaned.
The purging fluid is preferably fed into laterally open areas of the flow ducts or filter pockets for the fluid to be cleaned, which can, in particular, be of slit-like design in the area of the purging fluid inflow and/or outflow opening. The inflow and/or outflow areas for the purging fluid can also display a lower flow resistance than the filter walls, meaning that, for example, wide-meshed structures with only little flow resistance can be provided in the specified areas, e.g. in order to stabilize the filter walls. The purging fluid inlet into the filter body can thus also be fully permeable to particles—at least during purging with purging fluid.
The transverse direction in which the purging fluid is passed relative to the direction of flow of the fluid to be cleaned can, in particular, be essentially orthogonal to the latter. It goes without saying that the purging fluid flow ducts can also display a different orientation and, for example, be arranged at an angle to the flow ducts for the fluid to be cleaned. The purging fluid inlets and outlets can be located opposite each other on the filter body, although they can also be offset relative to each other in the longitudinal direction of the latter.
The purging fluid flow ducts can also display certain ramifications. Thus, if the filter body is constructed of structured filter walls arranged inversely to each other, for example, such that the crests and valleys of adjacent filter walls face each other, purging fluid flow ducts can be provided in this way, or can display a greater height if the crests and/or valleys each display indentations, enlarging the distance between them. This also makes it possible to create ramified purging fluid flow ducts.
Particularly preferably, the purging fluid flow ducts cross slit-like areas of the flow ducts for fluid the to be cleaned that extend at least essentially over the entire width of the filter body, i.e. the fluid is passed through slit-like ducts of this kind, transversely to the direction of flow of the fluid to be cleaned. In this context, the purging fluid can be fed to and discharged from the filter body at the same slit-like flow ducts on opposite sides of the filter body, to which end appropriately designed feed lines/discharge lines are provided.
The width of the purging fluid inlets and outlets can extend over only a relatively small extension of the filter body, e.g. only over less than ⅕ or 1/10 of its length, although the width of the purging fluid flow ducts can nevertheless extend over the full extension of the filter body, e.g. essentially over its full length.
Preferably, the flow ducts or filter pockets for the fluid to be cleaned that are open towards the outflow side of the filter body are at least partially, or completely, isolated from the purging fluid flow ducts, i.e. the purging fluid stream is passed through the filter body in such a way that it does not escape (or as little as possible) on the outflow side of the filter. To this end, the purging fluid stream is not passed through the filter pockets open towards the outflow end, or suitable flow-deflecting means or shut-off means are provided. Preferably, the pressure loss of the purging fluid between the purging fluid inlet and outlet is lower when performing regeneration, or when the filter is not laden with particles, than in the event of outflow through the filter outlet side.
To isolate the outflow-side flow ducts from the purging fluid flow ducts, the side walls of the filter body can be provided with corresponding recesses at appropriate points. Where appropriate, a perforated plate or slide valve can also be mounted on the respective side wall of the filter for this purpose, in order to provide inlet openings for the purging fluid on the required ducts and to seal the outflow-side ducts.
Numerous different embodiments of the filter body according to the invention are possible, where the filter walls can, for example, consist of a fabric that can be structured by deformation, such as a wire mesh or the like, this particularly being in the form of an endless strip, or also individual filter plates. The permeable carrier material can be coated with sinterable particles, such as metal or ceramic particles, where the pore structure of the filter can be provided by the sintered material. The filter body can, however, also be a sintered body made of metal, ceramic materials, including silicon carbide, or other materials.
If the filter body is constructed from individual layers of filter walls, which can be achieved both by depositing a strip of filter material in meandering fashion and by arranging and connecting separate filter wall segments, particle-tight side walls can be produced by folding and particle-tight joining of lateral areas of the strip or the respective filter walls. With this design, lateral areas of the filter can then be folded over, e.g. by approx. 180°, in order to produce purging fluid inlets into flow ducts for fluid to be cleaned that are open on the inlet side, and to at least partially, or completely, seal flow ducts that are open on the outflow side for the purging fluid.
The purging fluid inlet and/or purging fluid outlet on the filter body can be reinforced by stiffening elements. To this end, side wall areas of the respective filter walls that overlap each other can be laterally folded over, as a result of which the tabs formed in this way can be fixed on a housing or the like, where tabs of this kind can also be provided for fixing other stiffening elements, such as wires or strips, and can extend over the full extension of the filter body in the respective direction, e.g. its height.
The purging fluid inlet and/or outlet are preferably located in the region of, or directly at, the outflow-side end of the filter body or the flow ducts or filter pockets.
A particle accumulator is preferably provided, which is connected to the fluid stream outlet of the filter body in fluid-conducting fashion, so that the particles discharged from the filter body by the purging fluid stream can be collected in the particle accumulator. In this context, the particles can be separated from the purging fluid stream in the particle accumulator or, where appropriate, also in a separate device located upstream. The particle accumulator can, for example, display fleece or felt-like material for separating and retaining the particles. The filter material of the particle accumulator can be inexpensive, disposable material, so that the particle accumulator does not require regeneration. The capacity of the particle accumulator for separated particles can be several times greater than the capacity of the filter before the latter requires regeneration, e.g. 2 to 5 times, up to 10 times, or more, this permitting a substantial increase in the regeneration intervals of the filter system as a whole.
It goes without saying that suitable valves or shut-off devices can be provided on the respective flow ducts of the filter system, in order to be able to perform regeneration effectively. For example, the flow inlet and/or outlet of the filter for fluid to be cleaned can be shut off by corresponding valves when purging fluid is passed through the filter body to regenerate it. The purging fluid inlet and/or purging fluid outlet can be provided with corresponding valves when the filter is in normal operating state. Further, devices such as slide valves can be provided, for example, in order to seal the filter body in particle-tight fashion towards the purging fluid inlet and outlet and prevent uncontrolled escape of particles from the filter body. Accordingly, valves can be assigned to the particle accumulator, so that it can be sealed in particle-tight or fluid-tight fashion when regeneration is completed, in order to prevent the escape of particles.
Further, a heating device can be provided for heating the purging fluid fed to the purging fluid inflow opening. As a result of this heating, regeneration of the filter can be greatly accelerated during thermal treatment of the filter residues, such as incineration thereof. It goes without saying that heating of the purging fluid can be provided in addition or alternatively to heating of the filter residues by a heating device designed to heat the filter walls directly, by means of which spontaneous ignition of the deposited particles is achieved. The heat supplied to the filter by the heating of the purging fluid can constitute ≧approx. 50%, ≧approx. 75%, or essentially the entire quantity of heat required for thermal treatment of the filter residues.
Further, a temperature sensor can be provided for measuring the temperature of the filter walls and/or a fluid flowing through the filter body, in which context the temperature of cleaned fluid flowing out of the filter body is preferably measured. The purging fluid supply and/or the temperature of the purging fluid stream can be controlled by means of a purging fluid supply device as a function of this temperature. This makes it possible to prevent overheating of the filter body during thermal treatment of the filter residues during regeneration, since the burning-off of the deposited particles is exothermic, and excessive temperatures can damage the filter body.
Further, a device can be provided for controlling the regeneration of the filter by purging with purging fluid, said device controlling regeneration as a function of state and/or operating parameters of the filter and/or of a machine assigned to the filter that generates the particles to be separated. Regeneration of the filter can thus be performed on the respective machine, independently of other devices, such as a regeneration bench of a workshop. This is of eminent importance for motor vehicles, in particular, since the time spent in the workshop is drastically reduced as a result. The control device can, in particular, be configured in such a way that the purging process takes place while the machine or the internal-combustion engine continues to operate. Regeneration can, of course, also be performed at intervals, where, owing to the risk of overheating of the filter, regeneration can be performed during part-load operation, during idling of the internal-combustion engine, or in any other suitable operating state.
Preferably, one, several, or all components of the regeneration device are permanently located on the device or system generating the particle-laden exhaust gases, such as a motor vehicle, an internal-combustion engine or an industrial plant, meaning that regeneration independent of other devices can be performed, or at least essential components of the regeneration device are already provided on the device or system generating the exhaust gases. Components of this kind can include, in particular, the particle accumulator, the heating device for heating the purging fluid and/or the regeneration control device, and possibly also sensors, such as temperature and pressure sensors for monitoring the pressure of the purging fluid stream or the stream of exhaust gases to be cleaned. In the case of mobile devices, these are thus taken along. Further, a pressure-generating device for generating the necessary purging fluid pressure can be permanently located on the respective device or system, in which context the pressure-generating device can display a compressor and, where appropriate, also a pressure accumulator. In this context, the compressor can already be provided on the device or system for other purposes, e.g. it may be a compressor already present in a motor vehicle. Apart from the pressure-generating device, all components of the regeneration device can, where appropriate, already be provided on the device or system, also including, where appropriate, a pressure accumulator, by means of which the pressure generated by a compressor can be temporarily maintained.
The device or system assigned to the particle filter can, in particular, be a diesel engine of a motor vehicle, a marine engine or another internal-combustion engine, a power plant or another technical plant that generates particles or dust.
An example of the invention is described and explained below on the basis of the drawings. The figures show the following:
Particle filter 1 with regeneration system according to the invention comprises a plurality of filter walls 2 for separating particles, such as soot particles, from the exhaust-gas stream of an internal-combustion engine, e.g. a diesel engine. In this case, the filter walls consist of an open carrier material, such as wire mesh with sintered-on filter material. The filter can, however, also be a sintered body made of metal, ceramic materials, such as silicon carbide, or the like. In this context, filter walls 2 form filter body 3, which is located in housing 4, provided with inlet nozzle 5 and outlet nozzle 6, thus defining inflow side 7 and outflow side 8 of the filter.
In this case, filter walls 2 are produced from profiled, continuous strip 9 (
It goes without saying that, if the filter walls are deposited or profiled appropriately, the slit-like areas can also extend only over part of the filter length. Further, the profiles can also display ribs of wave-like shape or running transversely to the longitudinal axis of the filter, or they can be of a different design.
The filter body can be stabilized by additional stiffening elements, e.g. in the form of externally arranged wires 14, tab-like notches 15, which can be fixed to fastening areas 16 on the housing in load-transmitting fashion, elongated stiffening elements (not shown) extending parallel to the filter walls, or the like. The stiffening elements can in each case be fastened to the filter housing by frictional engagement, or also by positive engagement, or in some other manner. The stiffening elements are, in particular, located in each case on the inflow and outflow sides, or also in the inflow and outflow areas of the purging fluid.
To facilitate inflow of the fluid to be cleaned (see arrows,
For regeneration of the particle filter according to the invention, the side areas, which are located between the inflow and outflow side of the filter, are provided with purging fluid inlet opening 20 and purging fluid outlet opening 21, which, possibly with the provision of flow-deflecting means, are arranged in such a way that the filter pockets are pressurized with purging fluid as uniformly as possible over the full filter height. To this end, the purging fluid is supplied to the filter body via feed line 20a and discharged via discharge line 21a. Further, according to the practical example, purging fluid feed line 20a and discharge line 21a are located at different heights relative to each other, where a baffle plate or another kind of flow deflector can further be located upstream of the purging fluid inlet and also extend over a relatively large part of the filter height. Moreover, distributors 22, 23 are provided at purging fluid inlet and outlet 20, 21, distributing the fluid stream over the full height of the filter, preferably uniformly. The terms “height” and “width” of the filter refer in this instance to the representation in the Figures. It goes without saying that the expressions must be changed accordingly in the event of a different spatial orientation of the filter.
Because the purging fluid is passed through the filter pockets transversely or, more precisely, orthogonally to the direction of flow of the fluid to be cleaned, particles deposited in the filter pockets can be removed particularly easily through the purging fluid outlet, and the filter thus regenerated. In this context, the purging fluid stream is fed to the individual filter pockets transversely to the direction of flow of the fluid to be cleaned. In this context, the purging fluid inlet and outlet are located at the outflow end of the filter, although it goes without saying that, where appropriate, they can also be located at different positions in the longitudinal direction of the filter or the direction of flow, where, in particular, the purging fluid inlet can be located upstream of the purging fluid outlet in relation to the direction of flow. In this context, the purging fluid stream is fed to each of the individual filter pockets open on the inflow side, in each case preferably at the level of the slit-like, laterally open areas of the same, where the slits extend over the full width of the filter body or the full flow path of the purging fluid through the filter body. In this context, the slit height is reduced by preferably no more than 50% of the maximum or mean slit height along the purging fluid flow path, remaining essentially constant according to the practical example. The purging fluid inlet and, independently thereof, also the purging fluid outlet according to the practical example, are located in the outflow-side area of the filter, since particles to be separated, such as soot, are deposited to a greater extent here. Because the purging fluid stream is in this case located transversely, especially perpendicularly, to the longitudinal direction of the filter material strip deposited in meandering fashion, a stable filter of great tightness can be provided that is easy to regenerate. Generally speaking, the purging fluid inlet and outlet, or the purging fluid flow ducts, can be located in the areas of the filter body where elevated particle deposits are to be expected.
Regeneration of the filter is further facilitated by the fact that, in the area of the flow path of the purging fluid, or of purging fluid inlet and/or outlet 20, 21, the ducts or filter pockets, open on the inflow side, for the passage of fluid to be cleaned display a slit height amounting to ≧25% (or ≧50% or 75%) and, according to the practical example, approx. 100% of the mean, or also the maximum, height of the flow ducts for the fluid to be cleaned in the direction of flow. Filter walls 2 are thus vertically separated from each other in the area of the purging fluid flow paths or in the area of the outflow-side connecting areas of the filter walls. According to the practical example, these areas are provided by web-like areas 13 or the deflection areas of the strip of filter material deposited in meandering fashion. It goes without saying that the same also applies if separate filter walls are connected to each other in particle-tight fashion by corresponding joints, or if the filter body is constructed in some other way. However, this avoids acutely converging filter walls in the area of the outflow-side end of the filter body, which would result in narrow slits and thus in high pressure losses in the event of transverse flow of a purging fluid.
Very effective purging of the filter is possible because, although this can also apply to only one of them, where appropriate, the two purging fluid distributors 22, 23 extend over an area of the longitudinal axis of the filter, or the direction of flow of the fluid to be cleaned, that is greater than the width of the purging fluid inlet or outlet 20, 21.
Since the purging fluid only has to be fed to the filter pockets open on the inlet side, in which particles have collected, the filter pockets open on the outlet side are more or less completely isolated from the purging fluid ducts in order to enable effective regeneration of the filter. To isolate the purging fluid ducts from the filter outlet, edge areas 25 of the filter material strip are folded over and beaded in order to form particle-tight side walls of the filter pockets open on the outflow side. It goes without saying that, where appropriate, only partial lateral sealing of the respective filter pockets, and thus partial isolation, may also be sufficient. In order to form fluid-tight edge or side wall areas, the sintered-on filter material can, for example, be applied to the carrier in a greater layer thickness. For example, at the level of the inflow and outflow side of the purging fluid ducts, the side walls of the filter can also be designed with corresponding perforated plates having suitable, particularly slit-like, inlet openings for the purging fluid. Corresponding, separate flow-deflecting plates can easily be located laterally on the filter.
Further, mounted on the filter body in the area of purging fluid inlet and outlet 20, 21 are stiffening elements, designed in this case in the form of laterally angled tabs that are integrally molded on the filter walls or the areas of the filter strip forming the particle-tight side walls. These tabs are further fixed on fastening areas 16 on the housing in force-absorbing fashion. This results in stabilization of the purging fluid inlet and outlet areas, and particularly also of the filter walls in these areas.
The regeneration system further comprises particle accumulator 30, which can be connected to purging fluid outlet 21 in fluid-conducting fashion in order to accumulate particles washed out of the filter by the purging fluid. In this context, the storage capacity of the particle accumulator is several times greater than that of the filter. The particle accumulator can display an inexpensive storage medium, such as fleece or felt, glass or rock wool or the like, in order to retain the particles. In this context, the storage medium of the particle accumulator is a disposable material. The particles can be separated from the fluid in the particle accumulator, or also in a separate, upstream separating device, where appropriate. When necessary, the particle accumulator can be connected in fluid-conducting fashion to the purging fluid outlet, or coupled to the regeneration system, by means of valves, quick-disconnect coupling 32 or the like. The particle accumulator can be permanently mounted on the respective machine, motor vehicle or the like, or, where appropriate, it can be part of a separate, machine-independent regeneration device, e.g. of a workshop.
According to the practical example, the purging fluid stream is circulated, to which end return line 34 is provided, although the system can also be of open design, where appropriate, such that cleaned purging fluid is discharged into the environment.
The regeneration system further displays a purging fluid pressurizing device, consisting of compressor 35 and pressure accumulator 36 in this instance. The compressor and, where appropriate, also the pressure accumulator can in this case likewise be permanently mounted on the respective machine or, where appropriate, part of a machine-independent system. The purging fluid pressurizing device or the pressure accumulator can be isolated from the filter or the particle accumulator by means of valves.
Further, heating device 37 is provided, so that heated purging fluid can be fed to the filter for regeneration. As a result, the deposited particles can be at least partly, or completely, thermally decomposed or incinerated in the filter in order to reduce the quantity of waste. It goes without saying that an additional heating device can be provided that directly heats the filter walls, an adjacent area of the housing or the like, in order to assist thermal decomposition or incineration. According to the practical example, however, more than half, or all, of the heat necessary for thermal regeneration of the filter is supplied by purging fluid heating device 37.
Since the thermal decomposition or incineration of the particles in the filter is an exothermic process, temperature sensor 38 is provided, being coupled to heating device 37 via control device 39 in such a way that the output of heating device 37 can be reduced in the event of spontaneous ignition of the particles, for example. Further, the valve and the compressor are operated by control device 39.
Furthermore, pressure sensors 40 are provided, being located on the inflow side and the outflow side in this instance, in order to determine pressure losses across the filter and thereby indicate the need for regeneration and/or sufficient regeneration of the filter. The fluid stream required for this purpose can be a possibly particle-laden exhaust-gas stream of the machine, a partial purging fluid stream, or any other suitable fluid stream.
Further, the regeneration system can display a device for metering an additive from additive storage tank 45, said additive being fed into the stream of fluid to be cleaned by means of conveying device 46 and metering device 47. As a result, the thermal regeneration of the filter by decomposition or incineration of the particles can be artificially influenced by the additive. Accordingly, instead of, or in addition to, an additive supplied during the regeneration process or in other operating states of the filter, it is also possible to supply other auxiliaries for catalytic conversion of fluid components or the like. It goes without saying that suitable additives can also be fed to the purging fluid via a corresponding metering device. The individual components of the additive feed device can likewise be controlled via control device 39.
One special advantage of the filter system according to the invention is that regeneration can, where appropriate, also be performed while the respective machine continues to operate. Further, additional valves can be provided on the inlet side and/or the outlet side of the filter, in order to isolate the fluid flow ducts and prevent the outflow of purging fluid from the filter.
The purging fluid can be air, exhaust gases from the respective device or machine, or any other suitable fluid.
Regeneration of the filter can, of course, also be performed at certain intervals, where a need for regeneration can, for example, be indicated by the control device, e.g. on the basis of a pressure loss in the direction of flow, determined by pressure sensors 40.
The filter material strip doubled in this way is deposited in meandering fashion according to
In this instance, purging fluid feed line 50 with purging fluid inlet 51 is provided in the area of axis 100a, to which end the filter walls display corresponding recesses. Through opposite purging fluid outlets 53 in the filter pockets, the particle-laden purging fluid can be passed to a collector 52. In all other respects, the structure of the regeneration device corresponds to that in
