CN110761874B

CN110761874B - Vehicle exhaust gas treatment system and exhaust gas treatment method

Info

Publication number: CN110761874B
Application number: CN201810832521.1A
Authority: CN
Inventors: 严明
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2018-07-26
Filing date: 2018-07-26
Publication date: 2023-01-17
Anticipated expiration: 2038-07-26
Also published as: CN110761874A

Abstract

The application relates to an exhaust gas treatment system for a vehicle comprising a first stage catalyst (110) having an oxidation capability, a particulate trap (120), and a vanadium-based selective catalytic reduction device, wherein the exhaust gas treatment system further comprises an intake air temperature feedback control unit for the vanadium-based selective catalytic reduction device (130), the intake air temperature feedback control unit comprising a first intake air temperature detector (130I) for measuring a first actual intake air temperature (T3) of exhaust gas entering the vanadium-based selective catalytic reduction device (130), and a controller (130K) for changing an injection parameter for post-injection of a vehicle engine when the actual intake air temperature (T3) does not meet a predetermined intake air temperature threshold or threshold range for the vanadium-based selective catalytic reduction device (130). The application also relates to a method for exhaust gas treatment by using the exhaust gas treatment system, and a vehicle comprising the exhaust gas treatment system.

Description

Vehicle exhaust gas treatment system and exhaust gas treatment method

Technical Field

The application relates to the field of vehicle exhaust treatment, and particularly provides a vehicle exhaust treatment system comprising a particle collector (hereinafter, abbreviated as 'DPF') and a vanadium-based selective catalytic reduction (hereinafter, abbreviated as 'V-SCR') device, and a method for treating vehicle exhaust by using the exhaust treatment system.

Background

The selective catalytic reduction post-treatment technology adopting the vanadium-based selective catalytic reduction device is an important technology for enabling medium and heavy diesel vehicles to reach the Euro IV/Euro V emission level. The V-SCR device has been widely used in euro IV/euro V vehicles, especially due to its significant advantages in cost and performance. To meet the exhaust emission standards of Euro IV/Euro V alone, many vehicles are equipped with exhaust treatment systems that have only V-SCR devices, and no DPF.

However, as the national regulations on exhaust emission standards of vehicles become more stringent, improvements in exhaust treatment systems equipped with only a V-SCR device but no DPF have been required to add a DPF in order to meet higher exhaust emission standards.

The problem that the V-SCR device is low in working efficiency and even cannot work due to overhigh inlet air temperature of the V-SCR device caused by regenerating the DPF exists. Unlike the case where the DPF is used in combination with a copper-based or other type of SCR device, since the allowable intake air temperature of the copper-based or other type of SCR device is high, even in the case where the regeneration of the DPF is activated to generate much heat and the temperature of the exhaust gas flowing out of the DPF is highIn this case, the inlet temperature condition of the SCR device can also be satisfied or can be easily satisfied. The use of both a V-SCR device and a DPF may not be the case because V-SCR devices have poor high temperature performance compared to copper-based or other types of SCR devices, and vanadium-based catalysts may also release toxic vanadium-based compounds, such as V, at high temperatures (e.g., 550℃. For some V-SCR devices, or 600℃. For some other V-SCR devices) ₂ O ₅ And its toxicity affects the environment.

In addition to this, in order to control the emission of harmful exhaust emissions from a vehicle, it is common to inject a plurality of injections of fuel into the engine of the vehicle, which may include, for example, one or more pre-injections, a main injection, one or more post-injections, etc. The injection parameters of the post injection, the amount of exhaust gas in the exhaust gas conduit, etc. may also affect the intake air temperature of the V-SCR device.

Therefore, in the above-mentioned case, the allowable intake air temperature of the V-SCR device, which is much lower than the allowable intake air temperature for the normal operation of the copper-based or other type of SCR device, is difficult to satisfy, which becomes a key problem that prevents the simultaneous arrangement of the V-SCR device and the DPF from being implemented in practical use.

If the PDF device is additionally arranged, the V-SCR device is replaced by a copper-based SCR device without the problem of ultrahigh air inlet temperature, the operation steps and the related cost for calibrating the copper-based SCR device are increased, time and labor are wasted, and the price disadvantage is obvious.

Therefore, when facing an exhaust treatment system configuration with both DPF and V-SCR devices, how to solve intake air temperature control of the V-SCR device is an important technical challenge.

Disclosure of Invention

The V-SCR device can still keep the air inlet temperature thereof to meet the preset air inlet temperature critical value or critical range when being arranged at the downstream of the DPF by arranging the air inlet temperature feedback control unit for providing the air inlet temperature feedback control function of the V-SCR device, so that the V-SCR device can normally and efficiently work.

According to a first aspect of the present application, there is provided an exhaust gas treatment system for a vehicle, comprising, sequentially arranged in an exhaust gas flow direction in an exhaust gas conduit of exhaust gas emitted from an engine of the vehicle:

a first-stage catalyst having an oxidizing ability in which an oxidation reaction can occur to reduce the content of at least one of carbon monoxide and hydrocarbons and nitrogen oxides in exhaust gas discharged from the engine; a particulate trap disposed downstream of the first stage catalyst and configured to trap particulate matter in exhaust gas in an exhaust conduit; and a vanadium-based selective catalytic reduction device disposed downstream of the particulate trap and configured to reduce a NOx content in the exhaust gas through a reduction reaction under catalysis of a vanadium-based catalyst, wherein the exhaust gas treatment system further includes an intake air temperature feedback control unit for the vanadium-based selective catalytic reduction device, the intake air temperature feedback control unit including a first intake air temperature detector configured to measure a first actual intake air temperature of the exhaust gas entering the vanadium-based selective catalytic reduction device, and a controller configured to change an injection parameter of a post-injection of the vehicle engine when the actual intake air temperature does not satisfy a predetermined intake air temperature threshold value or threshold range for the vanadium-based selective catalytic reduction device.

According to another aspect of the present application, a vehicle is provided that includes the exhaust treatment system described above.

According to a third aspect of the present application, there is provided a method of vehicle exhaust treatment using the above exhaust treatment system, the method comprising the steps of measuring a first actual intake air temperature for vanadium-based selective catalytic reduction using a first intake air temperature detector; the method includes the steps of comparing, with a controller, the measured first actual intake air temperature with a preset intake air temperature threshold value or threshold range for the vanadium-based selective catalytic reduction device, and changing an injection parameter of a post-injection of the vehicle engine in a case where the first actual intake air temperature does not satisfy the preset intake air temperature threshold value or threshold range.

According to the vehicle exhaust gas treatment system, the intake temperature of the V-SCR device can be controlled to a preset intake temperature critical value or critical range by changing the injection parameter of the remote post injection through the setting of the intake temperature feedback control unit for the V-SCR device, so that the V-SCR device arranged at the downstream of the DPF can work normally and efficiently.

By adopting the vehicle exhaust gas treatment system, the intake air temperature of the V-SCR device can meet the allowable preset intake air temperature when the V-SCR device is arranged at the downstream of the DPF, and the V-SCR device can work normally and efficiently. This makes it possible to realize a vehicle exhaust gas treatment system and method using a technical solution in which a DPF and a V-SCR device are provided simultaneously, and the V-SCR device is provided downstream of the DPF. Especially for vehicles originally equipped with only a V-SCR device, provides a most economical and efficient way to meet more stringent exhaust emission standards.

Drawings

The above-mentioned and other features and advantages of this application will become more fully apparent to those skilled in the art upon reading the following description with reference to the accompanying drawings, in which:

FIG. 1 is a schematic block diagram of a portion of a vehicle exhaust treatment system according to the principles of the present application;

FIGS. 2a-2c are experimental curves of effectiveness of intake temperature feedback control methods for the V-SCR device of the present application under ETC, ESC, and WHTC engine cycling test conditions, respectively.

Detailed Description

The present application is directed to a vehicle exhaust treatment system including a particulate trap (DPF) and a vanadium-based selective catalytic reduction (V-SCR) device disposed downstream of the DPF.

Fig. 1 illustrates a preferred embodiment according to the principles of the present application. In the embodiment of fig. 1, after fuel is combusted in engine 100, exhaust gas resulting from the combustion is discharged into exhaust conduit 102. The direction D in which the exhaust gas flows in the exhaust gas duct after being discharged from the engine 100 is referred to as an exhaust gas flow direction. Along the exhaust gas flow direction D, the exhaust gas treatment system includes, in order, a first-stage catalyst 110 having oxidation capability disposed in an exhaust gas conduit 102 of the engine 100, closest to the engine 100 compared to other exhaust gas treatment devices, a particulate trap (DPF) 120 located downstream of the first-stage catalyst 110, and a V-SCR device 130 located downstream of the DPF 120. In accordance with the principles of the present application, the first stage catalyst 110 may be an oxidation catalyst (DOC) or a nitrogen oxide storage catalyst (NSC), or other type of catalyst having oxidation capabilities.

The exhaust gas treatment system according to the present application may further include a first intake air temperature detector 110I, a second intake air temperature detector 120I, and a third intake air temperature detector 130I that detect actual intake air temperatures T1, T2, and T3 of the first stage catalyst 110, the DPF 120, and the V-SCR device 130, respectively, in real time.

In the embodiment of fig. 1, the fuel injection to the engine 100 of the vehicle includes a pre-injection PiI, a main injection MI, and post-injections PI1 and PI2, according to the demand of the engine 100 and the purpose of changing the output pressure of the engine.

The small oil quantity pilot injection PiI is firstly carried out before the main injection, and the fuel of the pilot injection PiI generates a cold flame reaction in an engine cylinder so that the temperature and the pressure in the cylinder are increased in advance before the main injection. The pre-injection occurs when the engine cylinder piston is still advanced a significant amount from top dead center. The pre-injection step is optional and may be performed one or more times.

After that, the main injection MI is performed to the vehicle engine 100. The main injection MI serves as a source of engine power, and a large amount of fuel is injected into the cylinder upon start-up. After the fuel of the main injection MI is injected into the cylinder, the fuel of the main injection can be combusted in a short ignition delay period due to the pilot action of the pilot injection, the stagnation period is shortened, and the combustion temperature is lowered. Herein, the fuel may be natural gas or other gaseous fuel, but also liquid fuel, such as fuel oil.

The main injection MI is immediately followed by a first post-fuel injection, also referred to as a near-post injection PI2, to the engine 100. A second post fuel injection, referred to herein as far post injection PI1, is performed into the cylinder of engine 100 after a time interval from the end of the near post injection, at which the piston of the cylinder is farthest from top dead center.

Wherein a part of the fuel injected in the near-post injection PI2 is combusted in the engine cylinder, and another part of the fuel enters the exhaust gas duct together with the exhaust gas and is then combusted in the exhaust gas duct. This combustion directly affects the temperature T1 of the exhaust gas entering the first-stage catalyst 110, as measured by the first intake air temperature detector 110I.

The heat generated by the combustion of the near post injection PI2 increases the temperature of the exhaust gas entering and exiting the first stage catalyst 110, and thus the temperature of the exhaust gas entering the DPF 120. Meanwhile, during the process of the exhaust gas passing through the first-stage catalyst 110, the carbon monoxide and hydrocarbons and/or a part of the nitrogen oxides in the exhaust gas are converted into harmless water and carbon dioxide or nitrogen. Further, the fuel injected by the far after injection PI1 operation is combusted in the first-stage catalyst 110.

The exhaust gas exiting the first stage catalyst 110 enters the DPF 120. The DPF 120, which is a particulate filter, is capable of trapping a substantial portion, e.g., 90% or more, of particulate emissions, e.g., particulates, in the exhaust gas. On the other hand, as described above, since the exhaust gas entering the DPF 120 is relatively high in temperature due to the heat generated by the combustion of the fuel injected far after the PI1 in the first-stage catalyst 110, the deposited particulates trapped at the DPF 120 are subjected to oxidation combustion, which enables the filtering performance of the DPF 120 to be recovered. The process of the oxidation combustion of the particulates to restore the filtering performance of the DPF 120, referred to as regeneration of the DPF 120, causes the temperature within the DPF 120, and therefore the exhaust gas exiting the DPF 120 into the V-SCR device 130, to also be relatively high.

The exhaust gas exiting the DPF 120 continues to enter the V-SCR device 130 to convert nitrogen oxides in the exhaust gas to harmless nitrogen and water using the reductant under the catalysis of a vanadium-based catalyst. However, the V-SCR device 130 has an intake air temperature threshold or range for ensuring efficient operation and efficient driving functionality thereof. For example, the allowable intake air temperature threshold of the V-SCR device 130 may be 550 degrees, and if the intake air temperature is higher than this temperature, the V-SCR device 130 may fail.

In the case where the temperature activating regeneration of the DPF 120 may be higher than the intake air temperature threshold value or threshold range of the V-SCR device 130, in order to ensure that the temperature of the exhaust gas entering the V-SCR device 130 is not higher than the intake air temperature threshold value or meets the intake air temperature threshold value or threshold range, the exhaust gas treatment system of the present application includes an intake air temperature feedback control unit for the V-SCR device 130. The intake air temperature feedback control unit according to the present application mainly includes an intake air temperature detector 130I and a controller 130K.

In accordance with the principles of the present application, the controller 130K obtains a measured actual intake air temperature T3 of the V-SCR device 130 from the intake air temperature detector 130I via a communication connection with the intake air temperature detector 130I, compares the actual intake air temperature T3 to a preset intake air temperature threshold or critical range, and changes an injection parameter of the near or far post injection of the engine to directly or indirectly affect the actual intake air temperature T3 of the V-SCR device 130 if the actual intake air temperature T3 does not meet the intake air temperature threshold or critical range until the actual intake air temperature T3 meets the intake air temperature threshold or critical range.

In a preferred embodiment of the present application, the controller 130K does not change the injection parameter of the far post injection PI1 when the actual temperature T3 measured by the intake air temperature detector 130I satisfies the predetermined intake air temperature threshold value or threshold range, and the controller 130K controls the amount of fuel injected into the engine through the far post injection PI1 to be manipulated, specifically, the current amount of injected fuel to be multiplied by a control factor, when the actual intake air temperature T3 of the V-SCR device 130I does not satisfy the intake air temperature threshold value or threshold range. Experiments prove that the control factor is between 0 and 1. Changing the amount of fuel injected into the engine by the far after injection PI1 changes the combustion of the fuel in the first stage catalyst 110, affects the temperature of the exhaust gas discharged from the first stage catalyst 110 into the DPF 120, for example, the intake air temperature T2 measured by the second intake air temperature detector 120I, and further affects the regeneration process of the DPF 120, and finally changes the temperature of the exhaust gas discharged from the DPF 120 into the V-SCR device 130, that is, the actual intake air temperature T3 measured by the third intake air temperature detector 130I. In this manner, the intake air temperature T3 of the V-SCR device 130 is ensured to meet the intake air temperature threshold or range.

In addition, as described above, the combustion of the fuel injected by the near-after injection PI2 operation directly affects the temperature T1 of the exhaust gas entering the first-stage catalyst 110, which is measured by the first intake air temperature detector 110I. Thus, in the embodiment of FIG. 1, the exhaust treatment system of the present invention may include an intake air temperature feedback control unit for the first stage catalyst 110. This intake air temperature feedback control unit for the first stage catalyst 110 includes the above-described first intake air temperature detector 110I and the first controller 110K, wherein the first controller 110K is configured to change the injection parameter of the near-after injection PI2 as needed to change or control the intake air temperature T1 of the first stage catalyst 110 to a desired value or range. Changing the injection parameter of the near-post injection PI2 includes multiplying the fuel injection quantity of the near-post injection PI2 by a control factor, which is obtained through experimentation.

Finally, the combustion of the injected fuel in the first stage catalyst 110 by the far post injection PI1 operation directly affects the temperature T2 of the exhaust gas entering the DPF 120 measured by the second intake air temperature detector 120I. Thus, in the embodiment of FIG. 1, the exhaust treatment system of the present invention may further include an intake air temperature feedback control unit for the DPF 120. This intake air temperature feedback control unit for the DPF 120 includes the above-described second intake air temperature detector 120I and second controller 120K, wherein the second controller 120K is configured to change the injection parameter of the after-farad injection PI1 as needed to change or control the intake air temperature T2 of the DPF 120 to a desired value or range. Changing the injection parameter of the far after injection PI1 includes multiplying the fuel injection quantity of the far after injection PI1 by a control factor, which is also obtained through experimentation.

In accordance with the principles of the present application, the

controllers

110K,120K, and 130K may be the same controller, may be separate controllers, or alternatively, any two may be integrated together.

In correspondence with the above waste disposal system, the present application provides a method of operating the above waste disposal system, the method including the steps of measuring an actual intake air temperature T3 of the V-SCR device 130 using the third intake air temperature detector 130I; comparing the measured actual intake air temperature T3 with a preset intake air temperature threshold or range of the V-SCR device 130 by the controller 130K; and a step in which the controller 130K changes an injection parameter of the near or far after injection of the vehicle engine in a case where the actual intake air temperature T3 does not satisfy a preset intake air temperature threshold value or a threshold range of the V-SCR device 130. Further, the step of changing the injection parameter of the near or far post injection of the vehicle engine includes multiplying the fuel injection quantity of the near or far post injection by a control factor, wherein the control factor is obtained empirically.

The effectiveness of the exhaust treatment systems and methods of the present application has been experimentally verified. Fig. 2a-2c are tests performed by the inventors on ETC, ESC and WHTC engine emission test cycles, respectively. The maximum value of T6 was experimentally measured to be 513 ℃ in the ETC test cycle condition of fig. 2a, 540 ℃ in the ETC test cycle condition of fig. 2a, and 525 ℃ in the ETC test cycle condition of fig. 2 a. From experimental data, the feedback control scheme of the present application effectively controls the intake air temperature of the V-SCR device 130 to be less than the intake air temperature threshold of 550 ℃, so that the V-SCR device 130 can effectively remove nitrogen oxides in exhaust gas through a reduction reaction.

Since the combustion of the near-post injection PI2 injected fuel within the first stage catalyst 110 can directly affect its intake air temperature T1, it also indirectly affects the intake air temperatures T2 and T3 of the DPF 120 and the V-SCR device 130. Thus, in an embodiment not shown in this application, the controller 130K may also vary the intake temperatures T2 and T3 of the DPF 120 and the V-SCR device 130 to meet the operating requirements by controlling or varying the injection parameters of the near post injection PI2, similar to the way the controller 130K controls the injection parameters of the far post injection PI1.

According to the vehicle exhaust gas treatment system, the intake air temperature of the V-SCR device can be controlled to a preset intake air temperature critical value or critical range by changing the injection parameter of the remote post injection through the arrangement of the intake air temperature feedback control unit for the V-SCR device. This ensures that the intake air temperature of the V-SCR device, when disposed downstream of the DPF, also meets its allowable predetermined intake air temperature, and the V-SCR device also operates normally and efficiently. This makes it practical to have a vehicle exhaust treatment system and method that employs a solution in which both a DPF and a V-SCR device are provided simultaneously, and the V-SCR device is provided downstream of the DPF. Particularly for vehicles originally equipped with only a V-SCR device, provides a most economical and efficient way to meet more stringent exhaust emission standards.

Furthermore, an exhaust treatment system suitable for use with the principles of the present application may include other exhaust treatment devices, such as particulate matter catalytic oxidizers (POCs) or exhaust gas recirculation devices (EGR), in addition to the first stage catalyst, DPF, and V-SCR devices.

The foregoing provides descriptions of specific embodiments of the present application. It will be understood by those skilled in the art that the present application is not limited to the specific details described above and shown in the accompanying drawings. Numerous modifications and alterations may be made to the details by those skilled in the art without departing from the principles of the present application and the scope of the claims which follow.

Claims

1. An exhaust gas treatment system for a vehicle, comprising, arranged sequentially in an exhaust gas flow direction (D) in an exhaust gas conduit (102) of exhaust gas emitted from an engine (100) of the vehicle:

a first stage catalyst (110) having an oxidizing ability in which an oxidation reaction can occur to reduce the content of at least one of carbon monoxide and hydrocarbons and nitrogen oxides in exhaust gas discharged from the engine;

a particulate trap (120) disposed downstream of the first stage catalyst (110) and configured to trap particulate matter in exhaust gas in an exhaust conduit; and

a vanadium-based selective catalytic reduction device arranged downstream of the particulate trap (120) and serving to reduce the NOx content of the exhaust gas by a reduction reaction under the catalytic action of a vanadium-based catalyst,

wherein the exhaust gas treatment system further comprises an intake air temperature feedback control unit for the vanadium-based selective catalytic reduction device (130), the intake air temperature feedback control unit comprising a third intake air temperature detector (130I) for measuring a third actual intake air temperature (T3) of exhaust gas entering the vanadium-based selective catalytic reduction device (130), and a third controller (130K) for changing an injection parameter of a post-injection of fuel to the vehicle engine when the third actual intake air temperature (T3) does not satisfy a third predetermined intake air temperature threshold or threshold range for the vanadium-based selective catalytic reduction device (130) such that the third actual intake air temperature (T3) satisfies the third predetermined intake air temperature threshold or threshold range, wherein the post-injection comprises a near post-injection of fuel immediately after a main injection of the vehicle engine and a far post-injection of fuel to the vehicle engine (100) after the near post-injection when a piston of the vehicle engine (100) is in a vicinity of a farthest position from a point; and is

The exhaust gas treatment system further comprises a first intake air temperature detector (110I) for measuring a first actual intake air temperature (T1) of exhaust gas entering the first stage catalyst (110), and a first controller (110K) for controlling injection parameters of the near-after injection such that the first actual intake air temperature (T1) satisfies the first predetermined intake air temperature threshold value or range when the first actual intake air temperature (T1) does not satisfy a first predetermined intake air temperature requirement for the first stage catalyst (110).

2. The exhaust gas treatment system according to claim 1, wherein the third controller (130K) is configured to change the fuel injection amount by multiplying the fuel injection amounts of the far and near after injections by a change factor when the third actual intake air temperature (T3) does not satisfy a third predetermined intake air temperature threshold value or range for the vanadium-based selective catalytic reduction device (130).

3. The exhaust gas treatment system of claim 2, further comprising a second intake air temperature detector (120I) for measuring a second actual intake air temperature (T2) of exhaust gas entering the particulate trap (120).

4. The exhaust treatment system of claim 3, further comprising a second controller (120K) for controlling injection parameters of the after injection when the second actual intake air temperature (T2) does not meet a second predetermined intake air temperature requirement for the particulate trap (120).

5. The exhaust treatment system of claim 4, wherein the first controller (110K), the second controller (120K), and the third controller (130K) are separate controllers, or at least two of them are integrated together.

6. The exhaust gas treatment system of any of claims 1-5, wherein the first stage catalyst (110) is a nitrogen oxide storage catalyst or an oxidation catalyst.

7. A vehicle equipped with an exhaust gas treatment system according to any one of claims 1-6.

8. A method for vehicle exhaust gas treatment using an exhaust gas treatment system according to any one of claims 1 to 6, the method comprising the steps of measuring a third actual intake air temperature (T3) of the vanadium-based selective catalytic reduction device (130) using a third intake air temperature detector (130I); a step of comparing the measured third actual intake air temperature (T3) with a third preset intake air temperature threshold value or critical range for the vanadium-based selective catalytic reduction device (130) using a third controller (130K), and changing injection parameters for near-and far-after-injection of fuel to the vehicle engine (100) such that the third actual intake air temperature (T3) satisfies the third preset intake air temperature threshold value or critical range if the third actual intake air temperature (T3) does not satisfy the third preset intake air temperature threshold value or critical range; and a step of comparing, with the first controller (110K), the measured first actual intake air temperature (T1) with a first preset intake air temperature threshold value or threshold range for the first-stage catalyst (110), and changing fuel near-post injection of the vehicle engine (100) so that the first actual intake air temperature (T1) satisfies the first preset intake air temperature threshold value or threshold range, if the first actual intake air temperature (T1) does not satisfy the first preset intake air temperature threshold value or threshold range.