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CN-117846748-B - Exhaust gas heating apparatus with optimized fuel-air ratio distribution

CN117846748BCN 117846748 BCN117846748 BCN 117846748BCN-117846748-B

Abstract

The application relates to an exhaust gas heating apparatus with optimized fuel-air ratio distribution. The application relates to an exhaust gas line for guiding exhaust gases of an internal combustion engine, which exhaust gas line has a main flow line, a bypass and an adjustable throttle flap in the main flow line, which throttle flap is pivotable from an open position in which the main flow line is released and a closed position in which the main flow line is blocked, the bypass leading into an exhaust gas heating device with a pyrolysis reactor, at least part of the mass flow of the exhaust gases of the internal combustion engine being led into the pyrolysis reactor via the bypass, a nonwoven fabric being connected upstream of the pyrolysis reactor, the nonwoven fabric being fueled, the fuel being vaporized and at least partly reacting exothermically in the pyrolysis reactor with the oxygen component of the mass flow of the exhaust gases led into it by oxidation to provide a sufficiently high pyrolysis temperature, the exhaust gases heated by means of the device being led into the main flow line downstream of the exhaust gas heating device, the bypass leading into an inlet chamber, the inlet chamber downstream connecting two pyrolysis reactors, the pyrolysis reactors being arranged symmetrically with respect to the exhaust gas line.

Inventors

  • W. Overhoff
  • D.LEICHINGER

Assignees

  • 欧博耐尔有限公司

Dates

Publication Date
20260505
Application Date
20230914
Priority Date
20221007

Claims (14)

  1. 1. An exhaust gas line (1) for guiding exhaust gas of an internal combustion engine, wherein the exhaust gas line (1) has at least a main flow line (11) and a bypass (12) and an adjustable throttle flap (3) in the main flow line (11), wherein the throttle flap (3) is pivotable from an open position, in which the main flow line (11) is released, and a closed position, in which the main flow line (11) is blocked, wherein the bypass (12) opens into a device (2) for exhaust gas heating having at least one pyrolysis reactor (26), at least part of the mass flow of exhaust gas of the internal combustion engine is introduced into the pyrolysis reactor via the bypass (12), wherein at least one non-woven fabric (22) is connected upstream of the pyrolysis reactor (26), wherein fuel is supplied by means of the non-woven fabric (22), and the non-woven fabric (22) is applied with fuel, wherein the fuel evaporates and at least partially in the pyrolysis reactor (26) with the exhaust gas is introduced into the pyrolysis reactor (26) by means of the device (2), wherein the heat release flow of exhaust gas is provided by means of the pyrolysis reactor (26), the heat release flow of the exhaust gas is high enough to be introduced into the pyrolysis reactor (2) by means of the pyrolysis reactor, It is characterized in that the method comprises the steps of, The bypass (12) is formed by a flow duct which in cross section forms a subsection of the exhaust gas duct (1) and opens into an inlet chamber (21) of the device (2), wherein two pyrolysis reactors (26) are connected downstream of the inlet chamber (21).
  2. 2. The exhaust gas conduit (1) according to claim 1, characterized in that the two pyrolysis reactors (26) are arranged symmetrically with respect to the exhaust gas conduit (1).
  3. 3. The exhaust gas conduit (1) according to claim 1, characterized in that the device (2) for exhaust gas heating has at least one heating source by means of which the nonwoven fabric (22) can be heated and the fuel introduced into the nonwoven fabric (22) can be at least partially locally evaporated and/or can be heated to a temperature above the ignition temperature of the fuel and/or by means of which the exhaust gas introduced into the intake chamber (21) can be heated to a temperature above the evaporation temperature and/or the ignition temperature of the fuel.
  4. 4. An exhaust gas conduit (1) according to claim 3, characterized in that a flame pilot plug is arranged.
  5. 5. The exhaust gas conduit (1) according to any one of claims 1 to 4, characterized in that each pyrolysis reactor (26) has a baffle plate (25) with a plurality of through holes (24) downstream of the inlet chamber (21) through which a fuel-exhaust gas mixture is introduced into the pyrolysis reactor (26) in an evenly distributed manner.
  6. 6. The exhaust gas conduit (1) according to any one of claims 1 to 4, characterized in that the device (2) for exhaust gas heating has two metering pumps for metering fuel, wherein fuel is fed to the nonwoven fabric (22) and metered by means of a first metering pump, and wherein fuel is fed to a flame ignitor and metered by means of a second metering pump.
  7. 7. Exhaust gas conduit (1) according to any one of claims 1-4, characterized in that a bypass flap (31) is kinematically connected with the throttle flap (3) such that the throttle flap (3) is in its open position when the bypass (12) is closed and the throttle flap (3) is in its closed position when the bypass (12) is fully released.
  8. 8. The exhaust gas conduit (1) according to claim 7, characterized in that the throttle flap (3) and the bypass flap (31) are formed from a single component.
  9. 9. Exhaust gas conduit (1) according to claim 8, characterized in that the throttle flap (3) and the bypass flap (31) are formed from castings or injection-molded parts of the same material.
  10. 10. Exhaust gas conduit (1) according to claim 7, characterized in that the throttle flap (3) and the bypass flap (31) are synchronously pivotable about a common rotation axis (32) in a non-rotatable manner relative to each other.
  11. 11. Exhaust gas conduit (1) according to claim 8 or 9, characterized in that the throttle flap (3) and the bypass flap (31) are synchronously pivotable about a common rotation axis (32) in a non-rotatable manner relative to each other.
  12. 12. Exhaust gas conduit (1) according to claim 7, characterized in that a servomotor (4) is arranged, by means of which the throttle flap (3) and the bypass flap (31) are pivoted.
  13. 13. An exhaust gas conduit (1) according to any one of claims 1-4, characterized in that the bypass (12) is formed by an integral part of the main flow conduit (11).
  14. 14. An exhaust gas conduit (1) according to any one of claims 1-4, characterized in that the bypass (12) is formed by a circular portion of the exhaust gas conduit (1) having a circular cross-section.

Description

Exhaust gas heating apparatus with optimized fuel-air ratio distribution The invention relates to an exhaust gas line (Abgaskanal) for guiding exhaust gas of an internal combustion engine, wherein the exhaust gas line has at least a main flow line and a bypass, and an adjustable throttle flap (Klappe) in the main flow line, wherein the throttle flap is pivotable from an open position, in which the main flow line is released (freigegeben), and a closed position, in which the main flow line is blocked (blockiert), wherein the bypass opens into an exhaust gas heating device having at least one pyrolysis reactor, at least part of the mass flow of exhaust gas of the internal combustion engine is introduced into the at least one pyrolysis reactor via the bypass, wherein at least one nonwoven fabric (Vlies) is connected upstream of the pyrolysis reactor, which nonwoven fabric is fuelled, wherein the fuel evaporates and at least part of the oxygen components in the pyrolysis reactor that react exothermically with the mass flow of exhaust gas introduced into the pyrolysis reactor by oxidation, in particular in order to provide a sufficiently high pyrolysis temperature, wherein the exhaust gas heated by means of the device is introduced into the main flow line downstream of the exhaust gas heating device. Exhaust gas pipelines of this type are known from the prior art. DE 10 2010 049 957 A1 discloses a device by means of which the fuel can be decomposed into shorter carbon chains by pyrolysis and the exhaust gas can be heated by subsequent oxidation of the carbon chains in order to provide the exhaust gas temperature level required for effective nitrogen oxide reduction at cold start of the internal combustion engine. Such devices are usually arranged in a bypass parallel to the exhaust gas tract of the internal combustion engine and a part of the mass flow of the exhaust gas is led through the device. A catalyst for Selective Catalytic Reduction (SCR) is used for reducing nitrogen oxide emissions of diesel engines, combustion plants, garbage incineration plants, industrial plants, etc. (so-called SCR catalyst). For this purpose, a reducing agent is injected into the exhaust gas system using a metering device. Ammonia or ammonia solution or other reducing agent is used as the reducing agent. Since the carrying of ammonia in vehicles is of critical importance in terms of safety, urea is used, in particular in accordance with DIN 70070, in the form of an aqueous solution with a urea content of typically 32.5%. In the exhaust gas, urea decomposes into gaseous ammonia and CO 2 at temperatures above 150 degrees celsius. The parameters of urea decomposition are mainly time (evaporation time and reaction time), temperature and droplet size of the injected urea solution. In these SCR catalysts, the emission of nitrogen oxides is reduced by about 90% by selective catalytic reduction. The term reducing agent solution or reducing agent includes any reducing agent suitable for selective catalytic reduction, for which purpose urea solutions according to DIN 70070 are preferably used. In known exhaust gas aftertreatment systems for selective catalytic reduction, the relatively low temperature of the exhaust gas (e.g., at cold start of the internal combustion engine, i.e., before the operating temperature of the internal combustion engine is reached) may adversely affect the function of the SCR catalyst. After urea in the form of an aqueous solution is injected into the exhaust tract, ammonia (NH 3) must first be formed to enable the SCR reaction. Here, the reduced ammonia is released by thermomechanical decomposition (thermal decomposition) of urea and hydrolysis of the isocyanate formed. In the first reaction (thermal decomposition), urea is converted into ammonia (NH 3) and isocyanic acid (HNCO) due to the influence of temperature. In the second step, the hydrolysis is carried out in the presence of water, during which the isocyanate is likewise converted into ammonia, with the formation of carbon dioxide (CO 2). Relatively low temperatures (e.g., at cold start of the internal combustion engine) may slow the progress of these reactions. Therefore, in order to ensure the effect of selective catalytic reduction in the exhaust gas tract, the temperature level of the exhaust gas must be raised to a certain temperature level (about 200 ℃) as quickly as possible at the time of cold start. A disadvantage of the known apparatus is that the entire reaction chamber is first electrically heated in order to heat the pyrolysis reactor therein to a temperature level at which the introduced fuel can be automatically oxidized. For evaporation, the nonwoven has to be heated by radiant heat provided by the pyrolysis reactor. This requires very high temperatures in the pyrolysis reactor. Very high electrical power is required for this. Because the intensity of the current flowing through the pyrolysis reactor honeycomb is very high, damage may be