Exhaust gas purification system

Abstract

Otto or diesel engine (4) comprising the following: a charge air line (8.1); a charge air compressor (8.2); at least one three-way valve (8.5) in the charge air line (8.1) downstream of the charge air compressor (8.2); and an exhaust gas purification system (1) for exhaust gas of the Otto or diesel engine (4), wherein the exhaust gas purification system (1) comprises the following: an exhaust manifold arrangement (1.1), a main exhaust pipe (1.2) adjoining the manifold assembly (1.1), and a secondary air supply line (3.1) in addition to the main exhaust gas line (1.2) and with an integrated heating element (3.3), wherein the secondary air supply line (3.1) opens upstream of the outlet manifold assembly (1.1), wherein an entire exhaust gas path is preheated without a running Otto or diesel engine (4), wherein secondary air branches off upstream of the inlet system (8) by means of the at least one three-way valve (8.5) from the charge air line (8.1); wherein, in addition to the charge air compressor (8.2), an electrically operated boost compressor (8.3) is provided, which is connected to the charge air line (8.1) and serves as a secondary air pump (3.4); and wherein a further three-way valve (8.4) is provided, via which a source for the secondary air to be drawn in is switched.

Description

[0001] The invention relates to an exhaust gas purification system for exhaust gas of a gasoline or diesel engine with an exhaust manifold arrangement, with a main exhaust gas line adjoining the manifold arrangement, wherein a secondary air supply line with an integrated heating element is provided.

[0002] A device for heating an exhaust gas cleaning system of an internal combustion engine using secondary air is already known from DE 10 2017 222 235 A1. The secondary air system has an electric secondary air heating device by means of which the secondary air is heated before being introduced into the exhaust gas stream. The introduction into the exhaust gas stream takes place downstream of an exhaust gas turbine.

[0003] Furthermore, DE 10 2021 128 599 A1 discloses systems and methods for injecting hot air into exhaust ports, in particular for reducing emissions during a cold engine start. The method involves injecting heated air into an exhaust manifold pipe of each cylinder of the engine during an exhaust stroke of the corresponding cylinder following an exhaust pre-exhaust pulse, while an emission control device is being heated.

[0004] DE 10 2016 116 995 A1 discloses an exhaust system for removing exhaust gas from one or more combustion chambers of an internal combustion engine, comprising an exhaust pipe, at least one exhaust gas outlet and inlet, a compressed air source with a suction air inlet and outlet, and a 3-way valve controllable by means of a control system downstream of an intercooler.

[0005] DE 10 2018 218 665 A1 shows a secondary air injection system comprising an engine with a plurality of cylinders which generates a driving torque of a vehicle by combustion of a fuel, a main line which is connected to an exhaust manifold or exhaust pipe which is connected to the plurality of cylinders, a return line which branches off from the main line and is then connected to an intake manifold, an air injection line which branches off from the main line and is then connected to the intake line, and an electric compressor in the intake line.

[0006] DE 10 2015 015 794 A1 discloses a method for heating at least one exhaust aftertreatment device arranged in the exhaust tract of a motor vehicle comprising an internal combustion engine and powered by it. While combustion of fuel in the internal combustion engine is suspended, an airflow is generated that flows through at least the exhaust aftertreatment device and is heated by means of at least one electric heating element.

[0007] BEER, Johannes et al.: Electrically assisted charging for performance and consumption concepts; In: MTZ 12 / 2016, also teaches combustion engines with a combination of turbocharger and electrically driven compressor.

[0008] The invention is based on the objective of overcoming one or more of the problems or disadvantages associated with the prior art, and in particular of designing and arranging an exhaust gas purification system in such a way that optimal exhaust gas purification is ensured during cold engine starts.

[0009] The object of the present invention is achieved by an Otto or diesel engine and by a method for operating an Otto or diesel engine according to the main claims. The dependent claims relate to preferred embodiments of the invention.

[0010] According to the invention, the secondary air supply line terminates in the exhaust manifold assembly. This allows the entire exhaust gas path, starting from a cylinder or combustion chamber, to be preheated without the combustion engine running. This enables the warm gas start of the engine described below. Because of their relatively large mass, the exhaust manifold assembly and any turbocharger installed cause a significant cooling of the warm exhaust gas during a cold start before the exhaust gas can reach the first cleaning component in the exhaust system. This can be prevented by preheating before the engine start, as described above. The exhaust outlet or a cylinder head of the gasoline or diesel engine is also located upstream of the exhaust manifold assembly. The exhaust turbine is also located upstream of the exhaust manifold assembly.

[0011] According to the present invention, a method for operating a gasoline or diesel engine is further provided in which the heating element is activated and heated before being supplied with secondary air or exhaust gas. After the engine starts, the secondary air flows through a previously heated catalyst. This ensures that highly heated secondary air is available even in the first few seconds after a cold engine start. The secondary combustion in the manifold can thus be intensified and / or carried out more robustly.

[0012] For this purpose, it is advantageous if the secondary air pump is only activated after the engine has started. This avoids noise from the air pump before the engine starts.

[0013] The problem is also solved by an Otto or diesel engine with an exhaust outlet and an exhaust gas purification system according to the invention, wherein the secondary air supply line terminates in the exhaust outlet.

[0014] A conventional secondary air supply line is routed through the engine's intake system. Air is drawn from the air mass meter. This allows the engine management system to know the air mass flow rate through the secondary air system. The engine management system can then calculate the appropriate fuel injection quantity required for a precise air / fuel mixture in the catalytic converter.

[0015] If the secondary air supply is independent of the engine's intake system, then the exact air mass flow rate is generally unknown, meaning the secondary air system can only be operated when the engine is off. If the secondary air is drawn from the intake system downstream of the mass airflow sensor, the proposed secondary air system can operate with the engine both off and running.

[0016] When the engine is running after a cold start, the preheated secondary air enables a more robust and faster secondary air combustion and thus a faster heating of exhaust aftertreatment components to shorten the time until a catalyst reaction (Cat Light-off) is achieved.

[0017] Warming up exhaust system components before starting the engine leads to a faster achievement of the catalytic converter's light-off temperature and a faster catalytic reaction during a subsequent cold start. This time advantage is achieved not only by increasing the catalytic converter's component temperature but also by expelling liquid water from the catalytic converter structure.

[0018] It can also be advantageous to have an exhaust gas turbine in the main exhaust pipe, with a bypass for the turbine that connects to the main exhaust pipe downstream of the turbine. After the engine has warmed up, the exhaust gas can be further heated by combustion of fuel via the secondary air supply line. This ensures efficient operation of the exhaust gas purification system. The bypass is an external bypass and is not an integral part of the exhaust gas turbine housing. An additional secondary air supply line may be provided, which connects to the bypass.

[0019] Furthermore, it can be advantageous to have a catalyst in the main exhaust line downstream of the exhaust turbine. The catalyst is a three-way catalyst for gasoline engines or a DOC or SCR catalyst for diesel engines. The secondary air supply line terminates upstream of the catalyst.

[0020] It can also be advantageous to have a particulate filter in the main exhaust pipe, positioned either upstream or downstream of the catalytic converter. Upstream, the particulate filter prevents the catalytic converter from becoming fouled. However, it contributes to cooling the exhaust gas. The pre-start warm-up process according to the invention must therefore be designed accordingly. Downstream, the particulate filter does not contribute to cooling the exhaust gas. The pre-start warm-up process according to the invention can therefore be less intensive. However, faster fouling of the catalytic converter must be expected.

[0021] It can be advantageous for the heating element to be electrically powered. Without a running combustion engine, heating through the combustion of excess fuel in the exhaust gas cannot occur due to the lack of hot exhaust gas. Therefore, an electric heating element is advantageous.

[0022] Additionally, it can be advantageous if the secondary air supply line is operatively connected to a secondary air pump, with the secondary air pump being connected to the secondary air supply line. The secondary air pump allows for optimal supply of secondary air to the exhaust system.

[0023] In connection with the design and arrangement of the Otto or diesel engine according to the invention, it can be advantageous to provide an intake system for supplying the engine with a fuel-combustion air mixture, wherein the secondary air supply line is independent of the intake system. Thus, the warm air can be supplied to the exhaust system independently of the operation of the engine or the combustion air compressor.

[0024] In addition to the charge air compressor, an electrically driven boost compressor is provided, which is connected to the charge air line and serves as a secondary air pump. A so-called e-booster is present in the engine's intake system for some engine applications. This e-booster can also be operated without the combustion engine running, allowing parts of the exhaust system or the catalytic converter to be heated before the engine starts. This avoids the additional costs for a separate secondary air pump and expands the application range of the e-booster.

[0025] Further advantages and details of the invention are explained in the claims and the description and illustrated in the figures. These show: Fig. 1. A schematic diagram of an exhaust gas purification system; Fig. 2 a schematic diagram of another exhaust gas purification system; Fig. 3 a schematic diagram of an alternative exhaust gas purification system and Fig. 4. A schematic diagram of an alternative exhaust gas purification system.

[0026] Fig. Figure 1 shows an exhaust gas purification system 1 for a gasoline engine 4 with a main exhaust line 1.2. The main exhaust line 1.2 is connected to the gasoline engine 4 via an exhaust manifold assembly 1.1. The main exhaust line 1.2 also includes a turbine 5, a main exhaust catalyst or three-way catalyst 6, and a main exhaust particulate filter 7. The fuel-air mixture is supplied via an intake system 8, which is not shown.

[0027] The gasoline engine 4 also has an exhaust outlet 4.1, to which the exhaust manifold assembly 1.1 is connected. A secondary air supply line 3.1, equipped with a heating element 3.3, opens into the exhaust outlet 4.1. The secondary air supply line 3.1 also has a secondary air pump or compressor 3.4, which ensures the necessary overpressure for supplying ambient air to the exhaust outlet 4.1. The exhaust outlet 4.1 can thus be supplied with warm air independently of the operation of the gasoline engine 4 or independently of the turbocharger compressor.

[0028] After Fig. 2 The main exhaust line 1.2 also has a bypass line 1.3 which branches off at a bypass connection 1.3a upstream of the turbine 5 and opens downstream of the turbine 5 and upstream of the particulate filter 6.

[0029] Fig. 3 is based on the exhaust gas purification system 1 according to Fig. 1. The secondary air supply line 3.1 opens downstream of the exhaust outlet 4.1 into the manifold assembly 1.1.

[0030] Example of implementation Fig. The Otto or diesel engine 4 has a charge air line 8.1 and a charge air compressor 8.2. In addition to the charge air compressor 8.2, an electrically operated boost compressor 8.3 is provided, which is connected to the charge air line 8.1 and serves as a secondary air pump 3.4. For this purpose, a first three-way valve 8.4 is provided, through which the source for the secondary air to be drawn in is switched. The source is either an additional ambient air line 8.6 or the charge air line 8.1. The consumer for the drawn-in secondary air is switched via a second three-way valve 8.5. The consumer can be either the intake system 8 or the secondary air supply line 3.1 or the heating element 3.3. Reference symbol list 1 Exhaust gas purification system 1.1 Exhaust manifold arrangement 1.2 Main exhaust pipe 1.3 Bypass 1.3a Bypass connection 3.1 Secondary air supply line 3.3 Heating element 3.4 Compressor, secondary air pump 4 Otto or diesel engine 4.1 Exhaust outlet 5 Exhaust gas turbine 6 Three-way catalytic converter, main exhaust catalyst 7. Particle filters, main exhaust particulate filter 8 Inlet system 8.1 Charge air duct 8.2 Charge air compressor 8.3 Boost compressor 8.4 First three-way valve 8.5 second three-way valve 8.6 Ambient air duct

Claims

[1] Petrol or diesel engine (4) having: a charge air line (8.1); a charge air compressor (8.2); at least one three-way valve (8.5) in the charge air line (8.1) behind the charge air compressor (8.2); and an exhaust gas purification system (1) for exhaust gases from the petrol or diesel engine (4), the exhaust gas purification system (1) comprising: an exhaust manifold arrangement (1.1), a main exhaust pipe (1.2) connected to the manifold arrangement (1.1), and a secondary air supply line (3.1) in addition to the main exhaust line (1.2) and with an integrated heating element (3.3), wherein the secondary air supply line (3.1) opens upstream of the exhaust manifold arrangement (1.1), wherein an entire exhaust gas line is preheated without a running petrol or diesel engine (4), wherein secondary air branches off from the charge air line (8.1) upstream of the intake system (8) by means of the at least one three-way valve (8.5); wherein, in addition to the charge air compressor (8.2), an electrically operated boost compressor (8.3) is provided, which is connected to the charge air line (8.1) and serves as a secondary air pump (3.4); and wherein a further three-way valve (8.4) is provided, via which a source for the secondary air to be sucked in is switched. [2] Otto or diesel engine (4) according to claim 1, characterized by that an exhaust gas turbine (5) is provided in the main exhaust gas line (1.2), wherein a bypass (1.3) is also provided for the exhaust gas turbine (5), which bypass has a bypass connection (1.3a) on the main exhaust gas line (1.2) and opens into the main exhaust gas line (1.2) downstream of the exhaust gas turbine (5). [3] Otto or diesel engine (4) according to claim 1 or 2, characterized bythat a catalyst (6) is provided in the main exhaust line (1.2) downstream of the exhaust turbine (5). [4] Otto or diesel engine (4) according to one of the preceding claims, characterized by that a particle filter (7) is arranged in the main exhaust line (1.2), wherein the particle filter (7) is placed upstream or downstream of the catalyst (6). [5] Otto or diesel engine (4) according to one of the preceding claims, characterized by that the heating element (3.3) is electrically designed. [6] Otto or diesel engine (4) according to one of the preceding claims, characterized by that the secondary air supply line (3.1) is in operative connection with a secondary air pump (3.4), wherein the secondary air pump (3.4) is connected to the secondary air supply line (3.1). [7] Otto or diesel engine (4) according to one of the preceding claims, which further comprises an exhaust outlet (4.1), wherein the secondary air supply line (3.1) opens into the exhaust outlet (4.1). [8] Otto or diesel engine (4) according to claim 7, characterized by that the intake system (8) is provided for supplying the engine (4) with a fuel-combustion air mixture to be sucked in, wherein the secondary air supply line (3.1) is independent of the intake system (8). [9] Otto or diesel engine (4) according to one of the preceding claims, wherein either an additional ambient air line (8.6) or the charge air line (8.1) serves as the source. [10] Method: Operation of a gasoline or diesel engine according to one of the preceding claims, characterized by that the heating element (3.3) is activated and heated before flowing through with secondary air or exhaust gas. [11] Method according to claim 10, characterized bythat the secondary air pump (3.4) is only activated after the engine has started.

Images