Method for the artificial ashing of a particle filter

Abstract

Method for artificially ashing a particulate filter (3) downstream of an internal combustion engine in the exhaust system of a motor vehicle, wherein, to avoid depth filtration, an ash layer (A) is applied as a filter cake to the surface of the channel wall (2) of the particulate filter (3) in its new condition, characterized in that a direct coating of the wall surface or an internal coating of the particulate filter (3) is carried out with an ash former which is burned off during the operation of the motor vehicle.

Description

[0001] The invention relates to a method for the artificial ashing of a particle filter according to the preamble of claim 1.

[0002] DE 10 2009 049 624 A1 discloses the subject matter of the preamble of claim 1.

[0003] WO 2018 / 115 900 A1 teaches to apply a synthetic ash layer to the particle filter from the beginning.

[0004] From WO 2014 / 183998 A1, a method for determining the soot load of a particulate filter downstream of an internal combustion engine has become known. The determination of the recorded soot load includes taking into account predetermined soot fractions from soot-relevant events of a standardized driving cycle.

[0005] The invention is based on the objective of creating a method for the artificial ashing of a particulate filter downstream of an internal combustion engine in the exhaust stream of a motor vehicle.

[0006] This problem is solved according to the invention by the method features of claim 1. Further advantageous features of the method are included in the dependent claims.

[0007] One problem with artificial ashing is that the ongoing legal requirement to reduce fuel consumption while simultaneously tightening particulate matter limits (mass and number) poses an increasing challenge for combustion engine development. Meeting future particulate matter limits under the required conditions will hinder further fuel consumption reductions. This will lead to almost all combustion engines having to be equipped with a particulate filter in the future, as is already the case with diesel engines.

[0008] In the particulate filter, soot from combustion is separated and converted back into gaseous components through targeted filter regeneration. Ash components, originating from engine oil and / or fuel additives, also remain permanently in the filter. In particular, conventional particulate filters have two filtration functions: depth filtration and surface filtration. Depth filtration involves separating the particles within the filter wall. Surface filtration occurs on the filter surface. Over time, the particulate filter gradually transitions from a depth filter to a surface filter. Depth filtration is associated with a significant pressure increase, as this negatively impacts the permeability of the exhaust gas. Once the pores in the filter wall are largely clogged with soot, the soot subsequently accumulates on the surface.This surface filtration leads to a moderate pressure increase, which is lower than with depth filtration. When the soot in the filter is regenerated, the pressure decreases with hysteresis, meaning initially with a large pressure drop followed by a moderate pressure drop. Unlike soot, ash in the particle filter always accumulates on the wall and never within it, thus fundamentally and irreversibly preventing depth filtration of the soot, as the soot cannot penetrate the ash layer.

[0009] The main advantages achieved with the invention are that an ash layer can be selectively applied to the channel walls of the particulate filter, thus preventing deep filtration of the soot. According to the invention, this is advantageously achieved by applying an ash layer as a filter cake to the surface of the channel walls of the particulate filter when it is new, in order to prevent deep filtration. This ash layer must consist of elements that cannot be removed during subsequent operation through oxidation or general detachment. Furthermore, it must be ensured that this ash layer is only applied to the surface of the particulate filter and not embedded within it. For this purpose, suitable ash-forming elements in the particulate filter include, for example, calcium, magnesium, phosphorus, and zinc.

[0010] In another iteration of the process, the vehicle with the particulate filter is equipped with a special fuel for the initial tank fill. This fuel is designed to consume the filter cake within the particulate filter during operation until the initial fill is exhausted, thus allowing the ash layer to build up. A problem with this method is that refueling down to the reserve level must be reliably prevented to ensure the ash layer builds up in the particulate filter.

[0011] According to a further embodiment of the method, the invention provides that the internal combustion engine is filled with a special ash-forming oil for the formation of the filter cake in the particulate filter, which is replaced with normal oil after an initial service interval. In this case, it is essential to ensure that the initial fill is not supplemented or replaced with normal oil until the next service interval.

[0012] According to the invention, the wall surface or an internal coating of the particulate filter is directly coated with an ash-forming agent that burns off directly during vehicle operation. This offers the advantage that the ash is applied precisely to the surface of the particulate filter, either directly to the wall or to a coating of the particulate filter. With this method, the thickness and composition of the ash layer can be precisely controlled. This effectively prevents depth filtration and thus establishes a clear correlation between back pressure and accumulated soot. The back pressure of the components remains relatively constant over the service life of the particulate filter, and the pressure increase due to soot accumulation is linear. The filtration rate of known particulate filters only reaches the desired value after a certain period of operation.The method according to the invention allows the filtration rate to be set very precisely and achieves the required value even in its new state. The particle filter can be made extremely porous and thus exhibit extremely low back pressure because the proposed method allows the filtration rate to be set precisely.

[0013] An embodiment of the invention is shown in the drawing and the diagram and is described in more detail below.

[0014] They show: Fig. 1 a diagram of the particle filter 3 with a soot and ash layer A, Fig. 2 a diagram with soot content plotted on the x-axis and pressure Delta P on the y-axis.

[0015] In the method according to the invention, an ash layer A is applied to the surface of the channel wall 2 of the particle filter 3 in its new state, which in Fig. 1 shown and in the diagram Fig. Figure 2 shows a comparison with and without ash layer A, produced according to the invention. The diagram illustrates this. Fig. Figure 2 shows the curve with and without ash, with Delta P on the y-axis and the soot content on the x-axis.

[0016] To prevent depth filtration, an ash layer A, known as a filter cake, is applied to the surface of the channel wall 2 of the particulate filter 3 when the vehicle is new. This is achieved by filling the vehicle with a special fuel for the initial tank fill. This allows the filter cake to build up within the particulate filter 3 during operation until the initial tank fill is depleted, thereby creating the ash layer A. It is essential that refueling to the reserve level is strictly avoided to prevent any disruption to the proper formation of the ash layer A.

[0017] In a further iteration of the process, the internal combustion engine is filled with a special ash-forming oil to form the filter cake in the particulate filter 3, which is replaced with normal, common oil after a first service interval.

[0018] The wall surface or an internal coating of the particle filter 3 is directly coated with an ash-forming agent, which is burned off during the operation of the motor vehicle.

[0019] The advantages of this invention are: The ash is applied precisely to the surface, either directly onto the particle filter or onto the coating of the particle filter.

[0020] The thickness and composition of the ash layer can be precisely adjusted.

[0021] Depth filtration is deliberately prevented, thus allowing a clear correlation to be established between back pressure and accumulated soot.

[0022] The back pressure of the parts remains relatively constant over the operating time, and the pressure increase during soot deposition is linear.

[0023] The filtration rate can be set very precisely and reaches the required value even when new.

[0024] The particle filter can be extremely porous and thus have an extremely low back pressure, because the filtration rate can be precisely adjusted using the proposed method. REFERENCE MARK LIST A layer of ash 2 Channel wall 3 particle filters

Claims

[1] Method for artificially ashing a particulate filter (3) downstream of an internal combustion engine in the exhaust system of a motor vehicle, wherein, to avoid depth filtration, an ash layer (A) is applied as a filter cake to the surface of the channel wall (2) of the particulate filter (3) in its new state, characterized by , that a direct coating of the wall surface or an internal coating of the particle filter (3) is applied with an ash-forming agent which is burned off during the operation of the motor vehicle. [2] Method according to claim 1, characterized by , that the ash layer (A) on the inner surface of the particle filter (3) is adjustable with respect to its thickness and composition.

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