Exhaust system

Abstract

To provide a ventilation system capable of efficiently decomposing particulate substances collected by a gasoline particulate filter while suppressing an emission of particulate substances right after start of an engine.SOLUTION: An exhaust system 1 for exhausting air from an engine 101 is provided with: a plasma reactor 4; and a gasoline particulate filter 5 arranged on the downstream side of the plasma reactor 4 in a flow direction of exhaust gas.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an exhaust system.

Background Art

[0002] Conventionally, an exhaust gas treatment apparatus including a three-way catalyst and a gasoline particulate filter disposed on the downstream side of the three-way catalyst is known. The gasoline particulate filter removes particulate matter in the exhaust gas that has passed through the three-way catalyst (for example, refer to Patent Document 1 below).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problem to be Solved by the Invention

[0004] In the exhaust gas treatment apparatus as described in Patent Document 1, the collected particulate matter may be excessively deposited on the gasoline particulate filter.

[0005] In that case, in order to burn the collected particulate matter to regenerate the gasoline particulate filter, for example, at a predetermined timing, a process of consuming gasoline to heat the gasoline particulate filter to a temperature at which the particulate matter can be burned is required.

[0006] Accordingly, an object of the present invention is to provide an exhaust system capable of efficiently decomposing the particulate matter collected by the gasoline particulate filter while suppressing the discharge amount of particulate matter immediately after engine startup.

Means for Solving the Problem

[0007] The present invention [1] includes an exhaust system for exhausting gas from an engine, comprising a plasma reactor and a gasoline particulate filter positioned downstream of the plasma reactor in the direction of exhaust gas flow.

[0008] With this configuration, the plasma reactor suppresses the emission of particulate matter immediately after engine startup, while the particulate matter collected in the gasoline particulate filter can be oxidized and decomposed using ozone, nitrogen dioxide, and reactive oxygen species generated by the plasma reactor.

[0009] Therefore, particulate matter collected by the gasoline particulate filter can be efficiently decomposed without consuming fuel to heat the gasoline particulate filter.

[0010] The present invention [2] includes the exhaust system described in [1], further comprising an adsorption member positioned upstream of the plasma reactor in the direction of exhaust gas flow and capable of adsorbing hydrocarbons in the exhaust gas.

[0011] With this configuration, hydrocarbons in the exhaust gas can be adsorbed by the adsorption material immediately after the engine starts.

[0012] Furthermore, by positioning the plasma reactor downstream of the adsorption member, hydrocarbons detached from the adsorption member can be decomposed by the plasma reactor.

[0013] The present invention [3] includes the exhaust system described in [1] above, wherein the gasoline particulate filter has a passage through which exhaust gas passes, and on the inner surface of the passage is a first adsorption layer capable of adsorbing nitrogen oxides in the exhaust gas and a second adsorption layer capable of adsorbing hydrocarbons in the exhaust gas.

[0014] With this configuration, the gasoline particulate filter can remove not only particulate matter but also nitrogen oxides and hydrocarbons. [Effects of the Invention]

[0015] According to the exhaust system of the present invention, it is possible to efficiently decompose the particulate matter collected by the gasoline particulate filter while suppressing the emission amount of particulate matter immediately after engine startup. [Brief Description of the Drawings]

[0016] [Figure 1] Figure 1 is a schematic configuration diagram of a vehicle equipped with an embodiment of the exhaust system of the present invention. [Figure 2] Figure 2A is a cross-sectional view of the gasoline particulate filter shown in Figure 1. Figure 2B is an enlarged view of the porous wall shown in Figure 2A. [Figure 3] Figure 3 is an explanatory diagram for describing a modified example (1). [Modes for Carrying Out the Invention]

[0017] 1. Configuration of Exhaust System As shown in Figure 1, the exhaust system 1 is mounted on, for example, a vehicle 100.

[0018] The vehicle 100 includes an engine 101, an electrical system including a battery 102, an unillustrated intake system for taking intake air into the engine 101, an unillustrated fuel injection system for supplying fuel to the engine 101, and an exhaust system 1 for discharging exhaust gas from the engine 101. The engine is a gasoline engine.

[0019] The exhaust system 1 includes an exhaust pipe 2, an adsorbing member 3, a plasma reactor 4, a power supply device 5, a control device 6, and a gasoline particulate filter (GPF) 7.

[0020] (1) Exhaust Pipe The exhaust pipe 2 is connected to the engine 101 via an exhaust manifold. Exhaust gas discharged from the engine 101 passes through the exhaust pipe 2 and is discharged outside the vehicle. The exhaust gas flows in the direction in which the exhaust pipe 2 extends.

[0021] (2) Adsorption member The adsorption member 3 is disposed inside the exhaust pipe 2. The adsorption member 3 is preferably located in the upstream end portion of the exhaust pipe 2 in the flow direction of exhaust gas. The adsorption member 3 is arranged on the upstream side of the plasma reactor 4 in the flow direction of exhaust gas. The adsorption member 3 is capable of adsorbing hydrocarbons in the exhaust gas.

[0022] Specifically, the adsorption member 3 has a cylindrical shape. The adsorption member 3 extends in the flow direction of exhaust gas. The adsorption member 3 has a carrier and an adsorption layer inside. The carrier extends in the flow direction of exhaust gas. The carrier supports the adsorption layer. The carrier is in a mesh form or a honeycomb form, and has a plurality of passages through which exhaust gas passes. The adsorption layer covers the inner surfaces of the passages of the carrier. The adsorption layer is made of, for example, BEA-type zeolite or the like. When exhaust gas passes through the passages of the carrier, the adsorption layer adsorbs hydrocarbons in the exhaust gas.

[0023] (3) Plasma reactor The plasma reactor 4 is disposed inside the exhaust pipe 2. The plasma reactor 4 is arranged on the downstream side of the adsorption member 3 in the flow direction of exhaust gas. The plasma reactor 4 is capable of decomposing particulate matter, hydrocarbons and nitrogen oxides contained in the exhaust gas that has passed through the adsorption member 3. The plasma reactor 4 is a dielectric barrier discharge type plasma reactor.

[0024] Specifically, the plasma reactor 4 has a plurality of electrode panels 41. The plurality of electrode panels 41 are arranged side by side at intervals from each other in the direction orthogonal to the flow direction of exhaust gas. Each electrode panel 41 extends in the flow direction of exhaust gas. Each electrode panel 41 has a flat plate shape. Exhaust gas passes between the respective electrode panels 41.

[0025] Each electrode panel 41 has a conductor layer and a dielectric layer covering the conductor layer. The conductor layer is made of, for example, a metal (conductor) such as tungsten. The dielectric layer is made of, for example, ceramics (dielectric) such as aluminum oxide.

[0026] When power is supplied to each electrode panel 41, a discharge (dielectric barrier discharge) occurs between each electrode panel 41. As a result, the gas between each electrode panel 41 becomes a plasma state. In other words, plasma is generated within the plasma reactor 4.

[0027] (4)Power supply device The power supply unit 5 can supply power from the battery 102 to each electrode panel 41 of the plasma reactor 4. The power supply unit 5 is electrically connected to the battery 102. The power supply unit 5 is also electrically connected to each electrode panel 41. The power supply unit 5 can be switched on or off. When the power supply unit 5 is on, it can supply power to the electrode panels 41. When the power supply unit 5 is off, it does not supply power to the electrode panels 41.

[0028] (5) Control device The control unit 6 is an ECU (Electronic Control Unit) that performs electrical control of the vehicle 100, and includes a CPU (Central Processing Unit), ROM (Read Only Memory), and RAM (Random Access Memory). The control unit 6 is electrically connected to the battery 102. The control unit 6 starts up when power is supplied from the battery 102 when the ignition switch of the vehicle 100 is turned on.

[0029] The control device 6 is electrically connected to the power supply unit 5. The control device 6 switches the power supply unit 5 to an ON state or an OFF state by sending a predetermined electrical signal to the power supply unit 5. In other words, the control device 6 controls the power supply unit 5. To put it another way, the control device 6 controls the plasma reactor 4 via the power supply unit 5.

[0030] (6) Gasoline Particulate Filter (GPF) The GPF7 is positioned downstream of the plasma reactor 4 in the direction of exhaust gas flow. The GPF7 is capable of capturing particulate matter (PM) contained in the exhaust gas. In addition, the GPF7 is capable of adsorbing hydrocarbons (HC) and nitrogen oxides (NOx) contained in the exhaust gas.

[0031] More specifically, the GPF7 has a cylindrical shape. The GPF7 extends in the direction of exhaust gas flow. As shown in Figure 2A, the GPF7 has passages 71A and 71B.

[0032] The passage 71A extends in the direction of exhaust gas flow. The upstream end of the passage 71A in the direction of exhaust gas flow is open. The downstream end of the passage 71A in the direction of exhaust gas flow is closed.

[0033] Passage 71B runs parallel to passage 71A in a direction perpendicular to the exhaust gas flow direction. Passage 71B extends in the direction of exhaust gas flow. The upstream end of passage 71B in the direction of exhaust gas flow is closed. The downstream end of passage 71B in the direction of exhaust gas flow is open.

[0034] The GPF7 has multiple passages 71A and multiple passages 71B. The multiple passages 71A and multiple passages 71B are arranged alternately in a direction perpendicular to the exhaust gas flow direction.

[0035] The GPF7 has a porous wall 72 that separates passage 71A and passage 71B. Exhaust gas enters the GPF through passage 71A, passes through the porous wall 72, and exits the GPF through passage 71B. In other words, the exhaust gas passes through passages 71A and 71B. As the exhaust gas passes through the porous wall 72, particulate matter, hydrocarbons, and nitrogen oxides are collected or adsorbed by the porous wall 72 and removed from the exhaust gas.

[0036] As shown in Figure 2B, the porous wall 72 has a porous carrier 721, a first adsorption layer 722A, a second adsorption layer 722B, and a ternary catalyst layer 722C. In other words, GPF7 has a porous carrier 721, a first adsorption layer 722A, a second adsorption layer 722B, and a ternary catalyst layer 722C.

[0037] The porous carrier 721 is made of, for example, ceramics. The porous carrier 721 extends in the direction of exhaust gas flow. The porous carrier 721 has a predetermined thickness in a direction perpendicular to the direction of exhaust gas flow.

[0038] The first adsorption layer 722A, the second adsorption layer 722B, and the ternary catalyst layer 722C are arranged on the surface of the porous support 721. In other words, the first adsorption layer 722A, the second adsorption layer 722B, and the ternary catalyst layer 722C are arranged on the inner surface of the passage 71A or passage 71B.

[0039] More specifically, the first adsorption layer 722A is placed on the porous carrier 721. The first adsorption layer 722A is capable of adsorbing nitrogen oxides in the exhaust gas. The first adsorption layer 722A consists of an adsorbent capable of adsorbing nitrogen oxides. Examples of adsorbents capable of adsorbing nitrogen oxides include CHA-type zeolite and alkaline earth metals. Examples of alkaline earth metals include barium and calcium.

[0040] The second adsorption layer 722B is placed on top of the first adsorption layer 722A. In other words, the first adsorption layer 722A and the second adsorption layer 722B are capable of adsorbing hydrocarbons in the exhaust gas. The second adsorption layer 722B consists of an adsorbent capable of adsorbing hydrocarbons. An example of an adsorbent capable of adsorbing hydrocarbons is BEA-type zeolite.

[0041] The three-way catalyst layer 722C is placed on top of the second adsorption layer 722B. The three-way catalyst layer 722C consists of a three-way catalyst. The three-way catalyst layer 722C is capable of decomposing hydrocarbons and nitrogen oxides. When the second adsorption layer 722B is placed on top of the first adsorption layer 722A, and the three-way catalyst layer 722C is placed on top of the second adsorption layer 722B, hydrocarbons desorbed from the first adsorption layer 722A and nitrogen oxides desorbed from the second adsorption layer 722B can be purified by the three-way catalyst layer 722C.

[0042] 2. Exhaust gas purification in exhaust systems Next, we will explain the purification of exhaust gases in the exhaust system.

[0043] As shown in Figure 1, when the ignition switch of the vehicle 100 is turned on, the control device 6 is activated. Furthermore, when the starter motor turns, the engine 101 starts. When the engine 101 starts, the control device 6 switches the power supply unit 5 from the off state to the on state. This causes plasma to be generated in the plasma reactor 4.

[0044] Furthermore, when engine 101 is started, exhaust gas from engine 101 flows into exhaust pipe 2. The exhaust gas from engine 101 contains particulate matter, hydrocarbons, and nitrogen oxides.

[0045] The exhaust gas from engine 101 first passes through the adsorption member 3. At this time, hydrocarbons in the exhaust gas are adsorbed by the adsorption member 3. This suppresses the emission of hydrocarbons immediately after engine 101 starts up. "Immediately after engine 101 starts up" refers to the period from when engine 101 starts up until the three-way catalyst layer 722C in GPF7 reaches the activation temperature of the three-way catalyst.

[0046] Next, the exhaust gas that has passed through the adsorption member 3 passes through the plasma reactor 4. At this time, particulate matter in the exhaust gas is decomposed by the plasma. Hydrocarbons that were not adsorbed by the adsorption member 3 are also decomposed by the plasma. This suppresses the emission of particulate matter and hydrocarbons immediately after the engine 101 starts up. In the plasma reactor 4, the plasma acts on the exhaust gas, generating nitrogen dioxide, ozone, and reactive oxygen species from components in the exhaust gas (e.g., nitrogen oxides, oxygen).

[0047] Next, the exhaust gas that has passed through the plasma reactor 4 passes through the GPF 7. At this time, as shown in Figure 2A, particulate matter that has not been decomposed in the plasma reactor 4 is collected by the porous wall 72 of the GPF 7.

[0048] Here, GPF7 is positioned downstream of the plasma reactor 4 in the direction of exhaust gas flow. Therefore, nitrogen dioxide, ozone, and reactive oxygen species generated in the plasma reactor 4 flow to GPF7 along with the exhaust gas. Particulate matter collected on the porous wall 72 is oxidatively decomposed by the nitrogen dioxide, ozone, and reactive oxygen species from the plasma reactor 4. This allows for efficient regeneration of GPF7 without consuming fuel to heat it.

[0049] Furthermore, as shown in Figure 2B, hydrocarbons that are not adsorbed by the adsorption member 3 and are not decomposed by the plasma reactor 4 are adsorbed by the second adsorption layer 722B of the GPF7. In addition, nitrogen oxides in the exhaust gas are adsorbed by the first adsorption layer 722A of the GPF7.

[0050] This makes it possible to suppress the emission of particulate matter, hydrocarbons, and nitrogen oxides immediately after the engine 101 is started.

[0051] Then, as shown in Figure 1, when the temperature of the adsorption member 3 reaches, for example, 300°C or higher, the hydrocarbons adsorbed on the adsorption member 3 are detached from the adsorption member 3. The hydrocarbons detached from the adsorption member 3 enter the plasma reactor 4 along with the exhaust gas and are decomposed by the plasma. As shown in Figure 2B, hydrocarbons that are not decomposed in the plasma reactor 4 are adsorbed by the second adsorption layer 722B of the GPF7.

[0052] Furthermore, when the temperature of GPF7 exceeds the temperature at which the three-way catalyst is activated (for example, 300°C), the hydrocarbons desorbed from the second adsorption layer 722B and the nitrogen oxides desorbed from the first adsorption layer 722A are purified in the three-way catalyst layer 722C. Specifically, the hydrocarbons are oxidized and the nitrogen oxides are reduced, converting the hydrocarbons and nitrogen oxides into water, carbon dioxide, and nitrogen.

[0053] 3. Effects (1) According to the exhaust system 1, as shown in Figure 1, the GPF 7 is positioned downstream of the plasma reactor 4 in the direction of exhaust gas flow.

[0054] Therefore, the plasma reactor 4 suppresses the emission of particulate matter immediately after engine startup, while the particulate matter collected in the GPF7 can be oxidatively decomposed using nitrogen dioxide, ozone, and reactive oxygen species generated in the plasma reactor 4.

[0055] Therefore, particulate matter collected by the GPF7 can be efficiently decomposed without consuming fuel to heat the GPF7.

[0056] (2) According to the exhaust system 1, as shown in Figure 1, the adsorption member 3 is positioned upstream of the plasma reactor 4 in the direction of exhaust gas flow.

[0057] Therefore, immediately after engine startup, hydrocarbons in the exhaust gas can be adsorbed by the adsorption member 3.

[0058] Furthermore, because the plasma reactor 4 is located downstream of the adsorption member 3, hydrocarbons detached from the adsorption member 3 can be decomposed by the plasma reactor 4.

[0059] (3) According to the exhaust system 1, as shown in Figures 2A and 2B, the GPF 7 has a passage 71A through which exhaust gas passes, and on the inner surface of the passage 71A, there is a first adsorption layer 722A capable of adsorbing nitrogen oxides in the exhaust gas and a second adsorption layer 722B capable of adsorbing hydrocarbons in the exhaust gas.

[0060] Therefore, GPF7 can remove not only particulate matter but also nitrogen oxides and hydrocarbons.

[0061] 4. Variations Next, a modified example will be described. In the modified example, the same reference numerals are used for components similar to those in the above-described embodiment, and their descriptions are omitted.

[0062] (1) The arrangement of the first adsorption layer 722A, the second adsorption layer 722B, and the three-way catalyst layer 722C is not limited, as long as the nitrogen oxides desorbed from the first adsorption layer 722A and the hydrocarbons desorbed from the second adsorption layer 722B act on the three-way catalyst layer 722C. For example, as shown in Figure 3, the three-way catalyst layer 722C may be arranged downstream of the first adsorption layer 722A and the second adsorption layer 722B in the direction of exhaust gas flow. In this case, the nitrogen oxides desorbed from the first adsorption layer 722A and the hydrocarbons desorbed from the second adsorption layer 722B act on the three-way catalyst layer 722C together with the exhaust gas. Alternatively, the first adsorption layer 722A, the second adsorption layer 722B, and the three-way catalyst layer 722C may be arranged in the order of first adsorption layer 722A, second adsorption layer 722B, and three-way catalyst layer 722C in the direction of exhaust gas flow.

[0063] (2) If it is desired to adsorb nitrogen oxides intensively, the first adsorption layer 722A may be placed on top of the second adsorption layer 722B. [Explanation of Symbols]

[0064] 1. Exhaust System 3. Adsorption member 4 Plasma Reactor 7. Gasoline Particulate Filter 722A 1st adsorption layer 722B 2nd adsorption layer 101 Engine

Claims

1. An exhaust system for exhausting gases from an engine, An adsorption member capable of adsorbing hydrocarbons in exhaust gas, A plasma reactor is positioned downstream of the adsorption member in the direction of exhaust gas flow, A gasoline particulate filter having a three-way catalytic converter layer is positioned downstream of the plasma reactor in the exhaust gas flow direction. Equipped with, An exhaust system wherein, after the three-way catalytic converter layer of the gasoline particulate filter reaches the activation temperature of the three-way catalyst, the plasma reactor and the three-way catalytic converter layer decompose the hydrocarbons desorbed from the adsorbent member.

2. The exhaust system according to claim 1, wherein the gasoline particulate filter has a passage through which exhaust gas passes, and on the inner surface of the passage, there is a first adsorption layer capable of adsorbing nitrogen oxides in the exhaust gas and a second adsorption layer capable of adsorbing hydrocarbons in the exhaust gas.

3. An engine exhaust system, An adsorption member capable of adsorbing hydrocarbons in exhaust gas, A plasma reactor is positioned downstream of the adsorption member in the direction of exhaust gas flow, A gasoline particulate filter having a three-way catalytic converter layer is positioned downstream of the plasma reactor in the exhaust gas flow direction. Equipped with, An exhaust system wherein, after the three-way catalyst layer of the gasoline particulate filter reaches the activation temperature of the three-way catalyst, the plasma reactor and the three-way catalyst layer decompose the hydrocarbons desorbed from the adsorbent member.

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