Patent Application
20190003359
This application claims priority to German Patent Application No. 10 2017 006 152.1, filed Jun. 29, 2017, which is incorporated herein by reference in its entirety.
The present disclosure pertains to particulate filters which are used to remove particulate matter from the exhaust gases of an internal combustion engine, and more particularly pertains to a particulate filter for gasoline engines, for example gasoline engines with direct injection (GDI).
A particulate filter generally includes a core body made from porous ceramic material having a plurality of longitudinal channels with rectangular cross section which extend parallel to each other from an inlet side to an outlet side of the core body. Some of these longitudinal channels (which are usually referred to as inlet channels) are closed in the proximity of the outlet side, while the other longitudinal channels (which are usually referred to as outlet channels) are closed in the proximity of the inlet side. In order to reach the outlet channels, the exhaust gases are forced to flow from the inlet channels through the porous material of the core body, which traps the particulate matter which are carried in the gas stream.
One well-known side-effect of particulate filters is that a counter-pressure is built up, which reduces the output of the internal combustion engine and increases gradually as the quantity of the particulate matter trapped in the particulate filter increases. For this reason, the particulate filter periodically undergoes a regeneration process, the object of which is to remove the trapped particulate matter and return the filters to their original efficiency. The regeneration process is generally carried out by raising the temperature in the interior of the particulate filter to a value which causes the combustion of the soot retained therein.
However, soot is not the only particulate matter that is removed from the exhaust gases and collected in the interior of the particulate filter. In fact, the particulate matter also contain ashes which are produced by the combustion of the fuel and/or the lubricating oil which has seeped into the engine combustion chambers from the crankcase, and ashes from other sources, for example due to flaking, chipping or erosion of the engine components. These ashes cannot be combusted during the regeneration process and continue to accumulate inside the particulate filter.
Consequently, these ashes result in a continuous rise in the counter-pressure created by a particulate filter over the lifetime of the internal combustion engine even though regeneration processes are carried out periodically. In particular, it was found that the level of the counter-pressure created by these ashes is determined not solely by the quantity (e.g., the weight) of the ashes collected inside the particulate filter, but also by the distribution thereof. If one considers a given weight of accumulated ashes, the counter-pressure is generally higher if these ashes are deposited on the side walls of the particulate filter inlet channels instead of collecting in the region close to the closed ends of the inlet channels.
It was also found that the distribution of the ashes along the inlet channels of the particulate filter is affected by the quantity of soot contained in the exhaust gases. In exhaust gases with high quantities of soot, such as are produced by diesel engines, for example, the ashes form relatively large agglomerates, which tend to accumulated close to the closed ends of the inlet channels. On the other hand, in exhaust gases with smaller amounts of soot, such as are produced by gasoline engines for example, the ashes consist of relative small particles, which tend to be deposited along the side walls of the inlet channels, thereby forming an even layer. Consequently, the counter-pressure caused by a gasoline particulate filter (GPF) increases more rapidly in the lifetime of the engine than the counter-pressure resulting from a diesel particulate filter (DPF).
In accordance with the present disclosure, a gasoline particulate filter is provided which lowers the counter-pressure created by the ashes trapped therein, which is able to remain effective for the entire service life of the engine without causing an unacceptable level of counter-pressure, and which may have smaller dimensions than the existing particulate filters while still providing the same level of counter-pressure for the service life of the engine.
In view of the preceding summary, one embodiment of the disclosure provides a particulate filter for internal combustion engines having a core body with a longitudinal axis and a plurality of longitudinal channels extending parallel to the longitudinal axis of the particulate filter. Each of these longitudinal channels has a cross section whose periphery has a concave shape. A shape is concave if at least one line segment which is located outside of the figure can be drawn between two points on the shape in such manner as to create at least one region of the periphery that defines an indentation. By virtue of this configuration of the circumferential cross section, the side walls of the longitudinal channels have one or more ridge which protrudes towards the interior of the channel.
The effect of these ridges is to increase the turbulence of the exhaust gases flowing in the longitudinal channels, so that the ashes carried with them, including those with very small dimensions, tend to collect at the closed end of the longitudinal channels and are not deposited along the side walls. Moreover, the combined effect of the turbulence and the ridges promotes the agglomeration of the small particles to form particles with larger dimensions, which also tend to accumulate at the closed ends of the longitudinal channels instead of along the side wall. In this way, for a given quantity (e.g., mass) of trapped ashes, the disclosed particulate filter results in lower counter-pressure values while being able to trap a larger quantity of ashes than conventional particulate filters for a given maximum permissible counter-pressure value. With the formation of longitudinal channels having the suggested shape, it is thus truly possible to produce a particulate filter which remains effective for the entire service life of the internal combustion engine even though they have relatively small dimensions.
According to one aspect of the disclosure, the circumferential cross section of the longitudinal channels may have the form of a concave polygon. The significance of a polygonal shape is that it is easier to manufacture than other concave shapes. For example, the circumferential cross section of the longitudinal channels may have the shape of an equiangular concave polygon or an equilateral concave polygon or a regular concave polygon. These solutions make it possible to optimize the distribution of the longitudinal channels in the interior of the core body.
According to another aspect of the present disclosure, the circumferential cross section of the longitudinal channels may have the shape of a concave polygon having ten or more sides, for example twenty-four sides. With this solution, the side walls of the longitudinal channels are provided with a plurality of ridges, which do not block the flow of exhaust gases but effectively prevent the ashes transported thereby from being deposited along the longitudinal channels. In particular, the circumferential cross section of the longitudinal channels may have the shape of a stellate concave polygon. In this way, the filtering efficiency of the particulate filter is more uniform along the longitudinal channels, and it is more difficult for the ashes to be deposited along the side walls.
According to another aspect of the disclosure, the circumferential cross sections of all the longitudinal channels may be the same shape. In this way, it is possible to simplify production of the particulate filter while keeping its holding capacity in the interior of the core body uniform. Essentially for the same reasons, other aspects of the present disclosure provide that all longitudinal channels have the same values in terms of cross sectional area and/or the same value in terms of the hydraulic diameter.
According to a further aspect of the disclosure, the core body of the particulate filter may be manufactured from a porous ceramic material, for example a ceramic material with high porosity or standard porosity. In this way, it is possible to increase the ability of the particulate filter to retain particulate matter and ashes. In particular, the porous ceramic material of the core body may be cordierite.
By virtue of this solution, the particulate filter can be used in conjunction with a gasoline engine, thereby creating a “gasoline particulate filter (GPF). In addition, other objects, desirable features and characteristics will become apparent from the subsequent summary and detailed description, and the appended claims, taken in conjunction with the accompanying drawings and this background.
The present disclosure will hereinafter be described in conjunction with the following drawing figures, wherein like numerals denote like elements.
The following detailed description is merely exemplary in nature and is not intended to limit the invention or the application and uses of the invention. Furthermore, there is no intention to be bound by any theory presented in the preceding background of the invention or the following detailed description.
Some embodiments may include a motor vehicle system 100, which is shown in
The air may be fed to the air inlet 210 via an intake manifold 200. An air inlet duct 205 directs ambient air to the intake manifold 200. In other embodiments, a throttle valve 330 may be selected to regulate the stream of air to intake manifold 200. In further embodiments, a system for compressed air, such as a turbocharger 230 with a compressor 240 that rotates together with a turbine 250 is used. The rotation of compressor 240 increases the pressure and temperature of the air in line 205 and in intake manifold 200. An intercooler 260 contained in line 205 may reduce the air temperature. Turbine 250 rotates with the inflow of the exhaust gases coming from an exhaust manifold 225 which passes exhaust gas from outlet 220 through a series of guide vanes before it is expanded by the turbine 250. This example shows a variable geometry turbine (VGT) with a VGT actuator 290 which is designed to move the guide vanes or blades so that the blades alter the flow of the exhaust gas through the turbine 250. In other embodiments, turbocharger 230 may have a fixed geometry and/or a wastegate.
The exhaust gases exit the turbine 250 and are passed to an exhaust system 270. Exhaust system 270 may include an exhaust pipe 275 which is equipped with one or more exhaust gas post-treatment devices. Some embodiments may include an exhaust gas recirculation system (EGR) 300, which is connected to the exhaust manifold 225 and the intake manifold 200. The EGR system 300 may include an EGR cooler 310 to reduce the temperature of the exhaust gases in the EGR system 300. An EGR valve 320 controls the flow of the exhaust gases in the EGR system 300.
The post-treatment devices may particularly include the following but without necessarily being limited thereto: a catalytic converter 280, for example a three-way catalytic converter (TWC), and at least one particulate filter 400, in this case a gasoline particulate filter (GPF), which is arranged downstream of the catalytic converter 280 to collect the particulate matter contained in the exhaust gases.
The particulate matter include impure carbon particles which result from the incomplete combustion of the fuel (soot), together with ashes which are produced by combustion of the fuel and/or lubricating oil that have infiltrated the engine combustion chambers 150 from the crankcase, and ashes from other sources, for example due to flaking, chipping or erosion of the engine parts. The soot may generally be removed from the particulate filter 400 by “regeneration processes”, but the ashes cannot be removed by these processes and continue to accumulate in the interior of the particulate filter 400 for the entire lifetime of the internal combustion engine 110, leading to a constant increase in the counter-pressure.
With reference now to
Core body 420 may be made from a porous ceramic material. For example, the core body 420 of the embodiment under consideration may be made from cordierite, particularly cordierite with high porosity or cordierite with standard porosity. In diesel applications, the core body 420 may be produced from silicon carbide. The core body 420 has a honeycomb structure, and includes a plurality of hollow longitudinal channels 435 which extend side by side and parallel to longitudinal axis A and with a constant cross section from the inlet side 425 to the outlet side 430. These longitudinal channels 435 include “inlet” channels 435A and “outlet” channels 435B. The inlet channels 435A (the number of which is usually equal to half the total number of longitudinal channels 435) are closed off in the proximity of the outlet side 430 by a ceramic plug. The outlet channels 435B (which usually make up the rest of the longitudinal channels 435) are closed off in the proximity of the inlet side 425 by a ceramic plug. In this way, the exhaust gases coming from the inlet 410 in outer housing 405 are guided into the inlet channels 435A, and in order to reach the outlet 415 of outer housing 405 they are forced to flow through the side walls of the inlet channels 435A into the outlet channels 435B. The side walls of the inlet channels 435A are made from the porous ceramic material of the core body 420, so that they are able to trap the particulate matter carried in the gases.
According to the present embodiment, the circumference of the cross section of each inlet channel 435A has a concave shape. The cross section is understood to be the cross section of inlet channel 435A which is created by intersecting the inlet channel 435A with a plane that is perpendicular to the longitudinal axis A of core body 420 (as represented in
One skilled in the art will recognize that from the theoretical point of view a “polygon” has straight sides and pointed vertices; however in context of the present disclosure the vertices of the circumferential cross sections of inlet channels 435A may be slightly rounded by design or due to production in-accuracies and tolerances, and/or the sides may be slightly curved, uneven or irregular without departing from the scope of protection of the present disclosure.
This shape of the circumferential cross section causes the formation of one or more ridges 440 on the side walls of inlet channels 435A, which protruded towards the interior of the channel and extend over the entire length thereof. The effect of these ridges 440 is to increase the turbulence in the exhaust gases flowing in the inlet channels 435A, so that the ashes carried with the gases, including those with very small dimensions, tend to collect at the closed end, near to the outlet side 430 of the core body 420, and are not deposited along the side walls. Moreover, the combined effect of the turbulence and the ridges 440 promotes the agglomeration of the smaller particles to form particles with larger dimensions, which also tend to accumulate at the closed ends instead of along the side wall.
The effect of this distribution of ash is that for a given quantity (e.g., mass) of trapped ashes, the core body 420 generates lower counter-pressure values than the core bodies in conventional particulate filters, and conversely the core body 420 is able to trap a larger quantity of ashes than the core bodies of conventional particulate filters for a given maximum permissible counter-pressure value. With the suggested shape of the longitudinal channels 435A, the particulate filter 400 is thus able to remain effective for the entire service life of the internal combustion engine 110.
It should be noted that all circumferential cross sections of the inlet channels 435A may be the same shape. In addition, all inlet channels 435A may also have the same cross sectional area value, i.e. the area of the cross sections is the same, and/or the same value in terms of hydraulic diameter, wherein the hydraulic diameter DH of the channel may be defined as follows:
D
H=4A/P
wherein A is the value of the cross sectional area and P is the length of the circumference of the cross section.
It should also be noted that not only the inlet channels 435A, but also the outlet channels 435B may have a circumferential cross section with a concave shape and particularly the shape of a concave polygon, as was explained previously.
While at least one exemplary embodiment has been presented in the foregoing detailed description, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration of the invention in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing an exemplary embodiment as contemplated herein. It should be understood that various changes may be made in the function and arrangement of elements described in an exemplary embodiment without departing from the scope of the invention as set forth in the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 102017006152.1 | Jun 2017 | DE | national |
