Emission control system having a heating element

Abstract

The invention relates to an emission control system (1) for exhaust gas of an engine (6), having a main exhaust line (1.1), an exhaust turbine (1.2) and a main 3-way catalytic converter (3) downstream of the exhaust turbine. At least one heating element is provided. The at least one heating element is provided in a bypass (1.3) for the exhaust turbine (1.2), the bypass branching off from the main exhaust line (1.1) upstream of the exhaust turbine (1.2) at a bypass branch (1.4) and leading into the main exhaust line (1.1) downstream of the exhaust turbine (1.2) but upstream of the main 3-way catalytic converted (3), or is provided upstream of the exhaust turbine. It is also possible to provide one or two heating elements both upstream of the exhaust turbine without bypass, and also in a bypass (1.3).

Description

[0001] Exhaust gas purification system with heating element

[0002] Area

[0003] The invention also relates to an exhaust gas purification system for exhaust gases from an engine having a main exhaust system and an exhaust turbine. A bypass for the exhaust turbine is provided, which branches off at a bypass branch on the main exhaust system upstream of the exhaust turbine and opens into the main exhaust system downstream of the exhaust turbine.

[0004] background

[0005] An exhaust system for a gasoline engine is already known from DE 10 2008 032 604 A1, which includes a turbocharger in an exhaust system. The system also includes a burner arranged downstream of the turbocharger to introduce fresh air heated by the burner into the exhaust system to heat the exhaust gas flow.

[0006] US 2013 / 0255230 A1 discloses an exhaust gas purification system for a gasoline engine with two turbochargers and two turbo bypasses. A burner with a downstream oxidation catalyst is provided in the main exhaust stream downstream of the turbocharger and upstream of the second bypass.

[0007] The invention is based on the object of designing and arranging an exhaust gas purification system for the exhaust gas of a gasoline engine in such a way that improved exhaust gas purification is possible.

[0008] Summary

[0009] The object is achieved according to the invention by the features of the appended claims.

[0010] According to one embodiment, in an exhaust gas purification system for exhaust gas of an engine with a main exhaust line, an exhaust gas turbine and a bypass for the exhaust gas turbine, which is connected upstream of the exhaust gas turbine to a bypass outlet

[0011] REVISED SHEET (RULE 91) ISA / EP branch branches off from the main exhaust line and flows into the main exhaust line downstream of the exhaust turbine, a heating element is provided in the bypass, and a main 3-way catalytic converter is provided downstream of the bypass in the main exhaust line. It is known that 3-way catalytic converters can provide good exhaust gas purification. However, for good operation, an appropriate operating temperature is required, which is achieved via the exhaust gas flow during normal operation. However, there are situations where the exhaust gas flow cannot adjust to the operating temperature or cannot adjust it quickly enough. According to the invention, it is now possible to supply the main 3-way catalytic converter with additional heat during bypass operation via the heating element in the bypass of the exhaust turbine. This makes it possible to maintain its operating temperature or to reach it as quickly as possible.

[0012] This is particularly the case for driving situations where a high load is required after the engine has started, which is accompanied by high exhaust gas mass flows. For example, even on long downhill journeys, the exhaust flow may be so low that the operating temperature of the 3-way catalytic converter cannot be maintained. By supplying additional heat, the temperature can be adjusted accordingly. In this case, it is advantageous if the main 3-way catalytic converter in the main exhaust system is as fully operational across its entire volume as possible in order to comply with emissions regulations. The so-called light-off temperature should be reached as quickly as possible for its entire volume. This is also beneficial for the efficiency of the 3-way catalytic converter.

[0013] The heating element can be operated independently of the combustion engine. This allows the heat supply to be optimized depending on the exhaust system's requirements. It is even possible to operate the heating element before the engine starts. Without exhaust gas flowing through the heating element, heated air is directed via the bypass into the main exhaust system and through the three-way catalytic converter to preheat it, ensuring that a ready-to-use catalytic converter is available as soon as the engine starts.

[0014] It may also be advantageous if a bypass 3-way catalyst is also provided in the bypass, wherein the bypass 3-way catalyst is located upstream or

[0015] REVISED SHEET (RULE 91) ISA / EP is located downstream of the heating element. The bypass 3-way catalyst is significantly smaller than the main 3-way catalyst. This allows rapid heating of the bypass 3-way catalyst, so that the required catalyst effect can be quickly achieved, at least at lower exhaust flows in bypass operation. Even if the bypass 3-way catalyst is located upstream of the heating element in the bypass, it can be quickly heated by the exhaust gas in bypass operation. Additional heat is then provided for the significantly larger main 3-way catalyst via the heating element.

[0016] The bypass 3-way catalyst can preferably also be positioned downstream of the heating element, especially if it is somewhat larger (but still smaller than the main 3-way catalyst). In this case, the bypass 3-way catalyst would also be heated via the heating element. In both cases, the bypass 3-way catalyst can be heated quickly, so that a corresponding catalytic effect is achieved early on. Once a sufficient exhaust gas temperature has been reached in the bypass, the heating element can be deactivated. The bypass 3-way catalyst then has a sufficient operating temperature to ensure its function. In both cases, the main 3-way catalyst is also heated, so that when switching to normal turbocharger operation (bypass is deactivated), the main 3-way catalyst is preheated to such an extent that it can enable the required emissions conversion without the bypass 3-way catalyst.The bypass eliminates the need for an additional heat source in the main flow. This avoids the associated pressure loss and installation space in the main flow, which could result from installing an additional heating element. This additional pressure loss would be disadvantageous, especially at high mass flows.

[0017] Furthermore, it may be advantageous if a first electrical heating element is placed upstream of the bypass 3-way catalyst and a second electrical heating element is placed downstream of the bypass 3-way catalyst. This allows for maximum rapid heating of the purification components (e.g., catalysts).

[0018] REVISED SHEET (RULE 91) ISA / EP possible in the bypass and main flue system. Both heating elements can be activated and deactivated independently, allowing the required energy consumption to be optimized.

[0019] The heating element can, for example, be designed as a fuel-driven burner that operates with fresh air (and / or exhaust gas) and a fuel. However, the heating element can also be designed as an electric heating element positioned in the bypass / main exhaust system such that exhaust gas flows through it and is heated by one or more heating elements. For operation before an engine start, fresh air could also be passed through the electric heating element. Thus, both heating element types can be used independently of engine operation and the presence of exhaust gas.

[0020] Depending on the type of energy source available, one or the other embodiment may be advantageous. An electric heating element, like a burner, provides simple preheating even before engine start-up but may place a strain on the vehicle battery. The use of a burner requires additional fuel. Using a burner increases the overall gas mass flow through the main three-way catalytic converter, thus achieving maximum rapid heating evenly distributed across the length of the catalytic converter. Combined burners and heating elements can also be used.

[0021] It may be advantageous for the bypass 3-way catalyst to have a metal or ceramic monolith, particularly a metal-ceramic monolith, which serves as a support for the catalyst coatings. This can ensure a compact design with rapid heat-up capacity.

[0022] It may also be advantageous if at least one further cleaning module is provided in the main exhaust gas line downstream of the exhaust gas turbine, with the bypass upstream of the at least one further cleaning module being integrated into the main

[0023] REVISED SHEET (RULE 91) ISA / EP exhaust system to supply it with warm exhaust gas. A discharge downstream of at least one additional purification module is also possible, for example, if the latter does not require a particular operating temperature. Advantageously, a particulate filter, for example, can be provided as an additional purification module.

[0024] A turbo bypass with a heating element can be used in both spark-ignition and compression-ignition combustion engines. Depending on requirements, the bypass can be re-introduced into the main exhaust system before the first or another downstream exhaust gas purification component.

[0025] When using a burner, it can be advantageous if the combustion chamber is integrated directly into the bypass or if the bypass itself acts as a combustion chamber. It is also possible to inject fuel into the bypass, which is oxidized in a downstream bypass 3-way catalyst, releasing exothermic heat.

[0026] Preferably, the bypass can be switched on and off using appropriate control elements, such as valves, or controlled so that only a portion of the exhaust gas is applied to it. This can be advantageous, for example, when driving downhill, when turbine operation is actually desired, but additional heating may be beneficial.

[0027] In another embodiment, in an exhaust gas purification system for exhaust gases from an engine having an exhaust system and an exhaust turbine, a heating element is provided upstream of the exhaust turbine, with a main three-way catalyst being provided downstream of the exhaust turbine. Here, too, the advantages of an additional heat supply to the main three-way catalyst can be achieved so that it can maintain its operating temperature, if this is not controlled solely by the exhaust gas flow, or reach it as quickly as possible.

[0028] The heating element can again be designed as a fuel-driven burner, which is operated, for example, with fresh air and a fuel. However, the heating element can also be designed as an electrical heating element that is arranged in the exhaust system in such a way that exhaust gas flows through and is discharged via one or more

[0029] REVISED SHEET (RULE 91) ISA / EP several heating elements are heated. For operation before an engine start, fresh air could also be passed through the electric heating element. However, for the design without a bypass, the burner variant is preferred, as it prevents excessive pressure loss in the exhaust system.

[0030] In the case of a burner and in the design without a bypass, the burner gas is introduced upstream of the turbine. This can occur in the exhaust duct of the cylinder head, in the exhaust manifold, or in the turbine inlet. The combustion air for the burner can be lean engine exhaust gas or fresh air via an external air supply. With an electric heating element, these two variants are also possible: fresh hot air is supplied and / or the exhaust flow flows directly through the electric heating element. In the design without a bypass, the turbine housing is also heated, reducing its effect as a thermal sink for the engine exhaust gas.

[0031] In this embodiment, it is possible to provide a first heating element upstream of the exhaust turbine and a second heating element downstream of the exhaust turbine. This allows the turbine and the catalyst to be heated separately as needed.

[0032] While the bypass variant is preferred because it eliminates the need to heat the turbine housing, even if it can temporarily act as a thermal sink after switching to turbine operation, the other variant also has its advantages. However, it is also possible to combine both variants and install both a bypass with a heating element and a heating element in the main exhaust system upstream of the turbine, with one or the other heating element being operated as needed.

[0033] Short the

[0034] Further advantages and details of the invention are explained in the claims and the description and illustrated in the figures. They show:

[0035] CORRECTED SHEET (RULE 91) ISA / EP Figure 1 is a schematic diagram of an exhaust gas purification system with bypass according to a first embodiment;

[0036] Figure 1 a is a schematic diagram of an exhaust gas purification system without bypass according to a second embodiment;

[0037] Figure 2 is a schematic diagram of an exhaust gas purification system with bypass according to a third embodiment;

[0038] Figure 3 is a schematic diagram of an exhaust gas purification system with bypass according to a fourth embodiment;

[0039] Figure 4 is a schematic diagram of an exhaust gas purification system with bypass according to a fourth embodiment; and

[0040] Figure 5 shows a schematic diagram of a catalyst.

[0041] Detailed description

[0042] The same reference numerals are used in the following figures where identical or similar components are described.

[0043] Figure 1 shows an exhaust gas purification system 1 which is assigned to an engine 6, in particular a petrol or diesel engine, with combustion air inlet line 6.1.

[0044] The exhaust gas purification system 1 has a main exhaust line 1.1 with an exhaust turbine 1.2, as well as a bypass 1.3 for the exhaust turbine 1.2. The bypass 1.3 branches off upstream of the exhaust turbine 1.2 at a bypass branch 1.4 on the main exhaust line 1.1 and flows downstream of the exhaust turbine 1.2 at a bypass opening 1.5 into the main exhaust line 1.1. Downstream of the bypass opening 1.5, a main 3-way catalytic converter 3 is provided in the main exhaust line 1.1. In addition, an optional particulate filter 5 is provided in the main exhaust line 1.1, which is arranged downstream of the main 3-way catalytic converter 3. It is thus also arranged downstream of the bypass opening 1.5. However, it is also possible for the optional particulate filter 5 to be arranged upstream of the main 3-way catalytic converter 3 and possibly even upstream of the bypass opening 1.5.

[0045] REVISED SHEET (RULE 91) ISA / EP Both the main three-way catalyst 3 and the optional particulate filter 5 can generally be referred to as exhaust gas purification modules. Additional purification modules are not shown in this embodiment, but are not excluded either.

[0046] According to the exemplary embodiment shown in Fig. 1, a heating element 2 is provided in bypass 1.3. The heating element 2 can be designed as an electric heating element or as a burner. Other forms are also conceivable. An electric heating element 2 can, for example, be designed as a flow-through heating element arranged in the exhaust system such that exhaust gas flows through and is heated by one or more heating elements. For operation of the electric heating element without engine operation, an optional fresh air supply could also be provided upstream of the electric heating element.

[0047] In the burner embodiment, the heating element 2 has a supply line 2.1 for fuel and / or additional combustion air. Depending on whether the exhaust gas fed into the bypass is a lean or rich exhaust gas mixture, fuel and / or additional combustion air is required. The burner can be located externally on the bypass or internally in the bypass. For optional operation of the burner without engine operation, both a fuel and a combustion air supply or a combined supply are preferably provided.

[0048] The bypass 1.3 can be controlled via control elements (not shown), such as one or more valves, to allow or disallow exhaust gas from the main exhaust system 1.1 during engine operation. A corresponding control element can, for example, be such that it allows all exhaust gas, no exhaust gas, or a portion of the exhaust gas to pass through the bypass 1.3 during engine operation. In particular, a corresponding control element, such as a valve, can be provided upstream of the heating element 2.

[0049] In the embodiment shown in Fig. 1a, no bypass is provided. Here, a heating element 2 is provided directly in the main exhaust line 1.1 upstream of the exhaust turbine 1.2. This can be designed either as a burner or as an electric heating element, although a burner is preferred here.

[0050] REVISED SHEET (RULE 91) ISA / EP It is also possible to combine the two embodiments, i.e., to provide a bypass with heating element 2 and an additional heating element 2 directly in the main exhaust line 1.1 upstream of the exhaust turbine 1.2, preferably but not necessarily downstream of the bypass branch 1.4. The heating elements can be of the same or different types.

[0051] The embodiment according to Fig. 2 again has a bypass with heating element 2 similar to the embodiment according to Fig. 1. Identical elements are therefore not explained again. In this embodiment, the order of the main 3-way catalytic converter 3 and the particulate filter 5 is shown reversed. Furthermore, a bypass 3-way catalytic converter 4 is provided upstream of the heating element 2 in the bypass 1.3. This preferably has a significantly smaller volume than the main 3-way catalytic converter 3 and forms a further purification module for the exhaust gas if it is routed via the bypass. Further purification modules are not shown in this embodiment, but are not excluded either. The heating element 2 can again be designed as an electric heating element or as a burner.

[0052] The embodiment according to Fig. 3 again has a bypass with heating element 2 as in the embodiment according to Fig. 1. Identical elements are therefore not explained again. However, as an additional element, a bypass 3-way catalytic converter 4 is provided downstream of the heating element 2 in the bypass 1.3. This preferably has a significantly smaller volume than the main 3-way catalytic converter 3 and forms an additional purification component for the exhaust gas when it is routed via the bypass. Further purification components are not shown in this embodiment, but are not excluded either. The heating element 2 can again be designed as an electric heating element or as a burner.

[0053] The embodiment according to Fig. 3 again has a bypass with heating element 2 as in the embodiment according to Fig. 1. The same elements are therefore not explained again. In this embodiment, two heating elements 2a, 2b are provided, the heating element 2a upstream of the bypass 3-way

[0054] REVISED SHEET (RULE 91) ISA / EP catalyst 4 and heating element 2b downstream of the bypass 3-way catalyst 4. Both heating element 2a and heating element 2b can be a burner or, alternatively, an electric heating element. In particular, different types can also be provided.

[0055] Fig. 5 shows a schematic diagram of a catalyst 4 comprising a monolith 4.1, preferably made of ceramic or metal (metallite) or metal-ceramic. The monolith 4.1 is mounted in a housing 4.3 via a support mat 4.2 and coated with a catalyst coating.

[0056] In all embodiments, suitable control units can be provided to control the operation of the exhaust gas purification system, and in particular the heating element(s). Control can be dependent on sensor signals, such as a signal from a temperature sensor that allows inference about the temperature of a catalyst.

[0057] applicability

[0058] Below, various exemplary applications of the exhaust gas purification system are explained, which are essentially the same across the embodiments—with the exception of the embodiment shown in Figure 1a. As a basis, a first basic application is explained with reference to the first embodiment with reference to Figure 1.

[0059] A first application relates to an engine start-up process in which the temperature of the main 3-way catalytic converter 3 is initially determined. If this temperature is below a first predetermined value, e.g. the light-off temperature, gas is directed through the bypass 1,3 and the activated heating element 2 to the main 3-way catalytic converter 3. This can be fresh air if the engine has not yet been started and / or exhaust gas if the engine is already running. The heating element 2 heats the gas / exhaust gas above its inlet temperature in the bypass 1.3 in order to quickly bring the downstream main 3-way catalytic converter 3 to its operating temperature. Once this temperature is reached, the bypass can be closed and either the engine can be started or, if it is already running, the exhaust gas can be directed via the turbine.

[0060] REVISED SHEET (RULE 91) ISA / EP A second application relates to operation of the engine 6 during which it is determined that the temperature of the main three-way catalyst 3 is below a predetermined value. This may indicate that the exhaust gas from the engine 6 is not sufficient to keep the temperature of the main three-way catalyst 3 above the predetermined value, so that a drop below the light-off temperature also appears possible. This may occur, for example, during long downhill journeys, during start-stop operation of the engine 6 or in hybrid vehicles when the electric drive takes over in phases. In such situations, switching the engine 6 on and off is to be regarded as a normal operating mode and not to be compared with a restart as described above.

[0061] When the temperature of the exhaust aftertreatment device is below the predetermined value, exhaust gas is passed through the bypass 1 .3 and the heating element 2 is activated to provide additional heat to heat the main 3-way catalyst 3.

[0062] Of course, further applications are possible, but the above show the underlying idea for the provision of bypass 1.3 with heating element 2.

[0063] The embodiments with a bypass 3-way catalyst 4 operate in the same way, although the bypass 3-way catalyst 4 can be heated more quickly, thus enabling earlier catalytic treatment of exhaust gases. The arrangement of the heating element 2 or the heating elements 2a, 2b, as will be apparent to those skilled in the art, results in different adjustment options for achieving the respective operating temperatures for the catalysts.

[0064] The design without a bypass also enables similar applications, although in this case, no gas is selectively passed through a bypass, but only the heating element is activated or to achieve appropriate heating of the catalyst. A mixed design with a bypass and heating element in the main exhaust system upstream of the exhaust turbine also enables similar applications. In particular, the mixed design, for example,

[0065] REVISED SHEET (RULE 91) ISA / EP For example, the bypass with associated heating element can be used for engine start-up operation and the heating element in the main exhaust system for ongoing operation.

[0066] In summary, an exhaust gas purification system for engine exhaust gas is provided, comprising a main exhaust system, an exhaust turbine, and a main three-way catalytic converter downstream of the exhaust system. Furthermore, the exhaust gas purification system has at least one heating element, wherein the at least one heating element is provided in a bypass for the exhaust gas turbine, which branches off upstream of the exhaust system at a bypass branch on the main exhaust system and opens into the main exhaust system downstream of the exhaust system but upstream of the main three-way catalytic converter, or upstream of the exhaust system turbine. It is also possible to provide heating elements both upstream of the exhaust system turbine and in a bypass, or to combine the different embodiments. In a combination, the bypass can branch off upstream or downstream of the heating element in the main exhaust system.

[0067] From the above description of the specific embodiments, which are not intended to be limiting, various variations will become apparent to those skilled in the art, which variations fall within the scope of the invention as defined by the claims.

[0068] REVISED SHEET (RULE 91) ISA / EP List of reference symbols for exhaust gas purification system .1 Main exhaust tract .2 Exhaust turbine .3 Bypass .4 Bypass branch .5 Bypass orifice Heating element, burner, electric heating elementa Heating element, burner, electric heating elementb Heating element, burner, electric heating element.1 Fuel supply line Main 3-way catalyst, purification module Bypass 3-way catalyst .1 Monolith .2 Mounting mat for 4.1 .3 Housing Particulate filter Engine, gasoline engine, diesel engine .1 Combustion air inlet line

[0069] REVISED SHEET (RULE 91) ISA / EP

Claims

Patent claims 1. Exhaust gas purification system (1) for exhaust gas from an engine (6) with a main exhaust line (1.1) and with an exhaust gas turbine (1.2) and with a bypass (1.3) for the exhaust gas turbine (1.2), which bypass branches off upstream of the exhaust gas turbine (1.2) at a bypass branch (1.4) on the main exhaust line (1.1) and opens into the main exhaust line (1.1) downstream of the exhaust gas turbine (1.2), wherein at least one heating element (2) is provided in the bypass (1.3), wherein a main 3-way catalytic converter (3) is provided downstream of the bypass (1.3) in the main exhaust line (1.1).

2. Exhaust gas purification system (1) according to claim 1, wherein a bypass 3-way catalyst (4) is also provided in the bypass (1.3), wherein the bypass 3-way catalyst (4) is placed upstream or downstream of the heating element (2).

3. Exhaust gas purification system (1) according to one of the preceding claims, wherein a first heating element (2a) is provided upstream of the bypass 3-way catalyst (4) and a second heating element (2b) is provided downstream of the bypass 3-way catalyst (4).

4. Exhaust gas purification system (1) according to one of the preceding claims, wherein the heating element (2, 2a, 2b) is designed as an electrical heating element or as a burner.

5. Exhaust gas purification system (1) according to one of the preceding claims, wherein the bypass 3-way catalyst (4) comprises a monolith (4.1) made of metal or metallite.

6. Exhaust gas purification system (1) according to one of the preceding claims, wherein the bypass 3-way catalyst (4) comprises a ceramic monolith (4.1).

7. Exhaust gas purification system (1) according to one of the preceding claims, wherein in the main exhaust line (1.1) downstream of the exhaust gas turbine (1.2) at least one further purification module (3) is provided in addition to the main 3-way catalyst, wherein the bypass (1.3) opens upstream or downstream of the at least one further purification module (3) in the main exhaust line (1.1).

8. Exhaust gas purification system (1) according to one of the preceding claims, wherein the combustion chamber is integrated directly in the bypass (1 .3) or the bypass (1 .3) itself serves as a combustion chamber.

9. Exhaust gas purification system (1) according to one of the preceding claims, further comprising one or more control elements, such as valves, for controlling a flow of gas, in particular exhaust gas, through the bypass.

10. Exhaust gas purification system (1) for exhaust gas of an engine (6) comprising a main exhaust line (1.1) and an exhaust gas turbine (1.2), wherein a heating element (2) is provided in the main exhaust line (1.1) upstream of the exhaust gas turbine (1.2), and wherein a main 3-way catalyst (3) is provided downstream of the exhaust gas turbine (1.2).

11. Exhaust gas purification system (1) according to claim 10, wherein a first heating element (2a) is provided upstream of the exhaust gas turbine (1.2) and a second heating element (2b) is provided downstream of the exhaust gas turbine (1.2).

12. Exhaust gas purification system (1) according to claim 10 or 11, wherein the heating element (2, 2a, 2b) is designed as an electrical heating element or as a burner.

13. Exhaust gas purification system (1) according to one of claims 1 to 9 in combination with an exhaust gas purification system according to one of claims 10 to

Images