CN116398283B

CN116398283B - Aftertreatment emission device for DPF active regeneration and control method

Info

Publication number: CN116398283B
Application number: CN202310341996.1A
Authority: CN
Inventors: 王国栋; 李钊; 孙建颖; 王素梅; 薛振涛; 殷治梅; 钟绍海; 褚国良
Original assignee: Weichai Power Co Ltd
Current assignee: Weichai Power Co Ltd
Priority date: 2023-03-29
Filing date: 2023-03-29
Publication date: 2025-09-19
Anticipated expiration: 2043-03-29
Also published as: CN116398283A

Abstract

The application relates to the technical field of automobile electronics, in particular to a post-treatment emission device for DPF active regeneration and a control method, wherein the device comprises ccDOC systems, ccSCR systems, DOC systems, DPF systems, SCR systems, ASC systems, HC injection systems arranged between the ccSCR systems and the DOC systems, and a control system respectively connected with the engine post-injection systems and the HC injection systems, and the control system at least further comprises a first temperature sensor, a second temperature sensor, a third temperature sensor, a fourth temperature sensor, a first differential pressure sensor and a second differential pressure sensor. Through the device, two-stage fuel injection can be realized, HC entering SCR can be reduced, HC poisoning is prevented, and engine oil dilution risk can be reduced.

Description

Aftertreatment emission device for DPF active regeneration and control method

Technical Field

The application relates to the technical field of automobile electronics, in particular to a post-treatment emission device for DPF active regeneration and a control method.

Background

A DPF (diesel particulate filter, particulate matter trap) is used to trap engine particulates, thereby reducing the amount of ash emitted to the atmosphere. The trapped particulates in the DPF can be burnt out through active regeneration or passive regeneration, the passive regeneration refers to that NO2 in the tail gas has strong oxidizing capability on the trapped particulates in a certain temperature interval, so that the NO2 can be used as an oxidizing agent to remove particulates in a particulate trap, CO2 is generated, the NO2 is reduced to NO, the purpose of removing the particulates is achieved, the active regeneration refers to that the temperature in the DPF is increased by using external energy, and the particulate is burnt on fire, and is mainly used for the particulates which cannot be removed after the passive regeneration. However, in the prior art, the DOC system and the SCR system are adopted, and the pollutant emissions such as PM (particulate matters) and NOx (nitrogen oxides) are out of limits during regeneration.

Disclosure of Invention

The invention aims to provide a DPF active regeneration after-treatment emission device and a control method, so as to at least partially solve the problems in the prior art.

The invention provides a DPF active regeneration aftertreatment emission system which comprises a ccDOC system, a ccSCR system, a DOC system, a DPF system, an SCR system and an ASC system which are sequentially communicated with an engine tail gas outlet through an exhaust pipe, an HC injection system arranged between the ccSCR system and the DOC system, and a control system respectively connected with the engine post-injection system and the HC injection system, wherein the control system at least further comprises a first temperature sensor arranged in the ccDOC system, a second temperature sensor arranged in the DOC system, a third temperature sensor and a fourth temperature sensor respectively arranged at the upstream and downstream of the ccDOC system, and a first pressure difference sensor and a second pressure difference sensor respectively arranged in the ccSCR system and the DPF system.

The second aspect of the present invention provides a post-treatment emission control method for active regeneration of a DPF, implemented by a post-treatment emission system for a DPF regeneration condition as described above, comprising the steps of:

Respectively judging whether the first-stage regeneration condition and the second-stage regeneration condition are met, and starting to calculate the oil injection quantity when the conditions are met;

Calculating to obtain a primary oil injection output value based on the mass flow of the waste gas, the temperature in the ccDOC system and the temperature at the upstream of the ccDOC system;

calculating to obtain a secondary oil injection output value based on the mass flow of the exhaust gas, the temperature in the DPF system and the temperature at the upstream of the DOC system;

and injecting fuel oil to an engine cylinder based on the primary injection output value through an engine post-injection system, and injecting fuel oil to the DOC system based on the secondary injection output value through the HC injection system.

The post-treatment emission control method for DPF regeneration working conditions provided by the invention can also have the following additional technical characteristics:

in one embodiment of the present invention, determining whether the first-stage regeneration condition and the second-stage regeneration condition are met includes:

When the vehicle speed is 0, the temperature of the upstream of the ccDOC system is higher than the ignition temperature and is in a regeneration mode, the first-stage regeneration condition is met;

and when the vehicle speed is 0, the temperature of the upstream of the DOC system is greater than the ignition temperature and the DOC system is in the regeneration mode, the secondary regeneration condition is met.

In one embodiment of the present invention, the light-off temperature is set to 280 ℃.

In one embodiment of the present invention, calculating a primary injection output value based on the mass flow of exhaust gas, the temperature within the ccDOC system, and the temperature upstream of the ccDOC system comprises:

Obtaining ccDOC post-system set temperature based on ccDOC system upstream temperature and exhaust mass flow;

obtaining a temperature difference value based on ccDOC system rear set temperature and ccDOC system actual temperature;

performing closed-loop control on the temperature difference value to obtain feedback oil quantity;

And calculating the sum of the feedback oil quantity and the feedforward oil quantity, wherein a smaller value in the calculated sum and the oil injection boundary is the primary oil injection output value.

In one embodiment of the present invention, calculating the secondary fuel injection output value based on the exhaust gas mass flow, the temperature in the DPF system, and the temperature upstream of the DOC system includes:

Obtaining an upstream set temperature of the DPF system based on the DOC system upstream temperature and the exhaust gas mass flow;

obtaining a temperature difference value based on the set temperature of the upstream of the DPF system and the actual temperature of the upstream of the DPF system;

and calculating the sum of the feedback oil quantity and the feedforward oil quantity, wherein a smaller value in the calculated sum and the oil injection boundary is the secondary oil injection output value.

In one embodiment of the invention, the feed-forward oil amount is calculated by the following formula:

Wherein q is the fuel mass flow rate in kg/h, C is the exhaust gas mass flow rate in kg/h, m is the exhaust ratio constant pressure heat capacity in J/(kg·DEG C), deltat is the temperature difference in DEG C, h is the heat value of the fuel in J/kg, eta is the fuel oxidation efficiency in%.

In one specific embodiment of the present invention, whether the first-stage regeneration condition and the second-stage regeneration condition are met is determined, and before the conditions are met, the fuel injection amount calculation is performed, the method further includes:

The upstream temperature ccDOC is controlled above the light-off temperature by means of a pair of thermal management measures.

A third aspect of the present invention provides a vehicle comprising an aftertreatment exhaust system for active regeneration of a DPF as described above.

In one embodiment of the present invention, the post-system set temperature of ccDOC is at least 350 ℃.

According to the aftertreatment emission system for DPF active regeneration, the ccDOC system and the ccSCR system are added between the turbocharger and the DOC system, during regeneration, fuel injection is carried out in two stages, the first stage uses in-cylinder post injection, the second stage uses the HC injection system for injection, HC entering SCR can be reduced, HC poisoning is prevented, and the engine oil dilution risk can be reduced. Meanwhile, fuel injection is carried out in two stages, the post-temperature of ccDOC is increased to 350 ℃ by means of in-cylinder post-injection, and at the moment, the SCR conversion efficiency is high, and emission is guaranteed.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are needed in the description of the embodiments or the prior art will be briefly described, and it is obvious that the drawings in the description below are some embodiments of the present invention, and other drawings can be obtained according to the drawings without inventive effort for a person skilled in the art.

FIG. 1 is a layout of an aftertreatment exhaust system for active DPF regeneration in an embodiment of the invention;

FIG. 2 is a logic diagram of calculation of the first-order regeneration fuel injection quantity;

FIG. 3 is a logic diagram of the calculation of the amount of secondary regeneration fuel injection.

1-First temperature sensor, 2-second temperature sensor, 3-third temperature sensor, 4-fourth temperature sensor, 5-first differential pressure sensor, 6-second differential pressure sensor, 7-fifth temperature sensor, 8-HC injection system.

Detailed Description

Exemplary embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. While exemplary embodiments of the present invention are shown in the drawings, it should be understood that the present invention may be embodied in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

It is to be understood that the terminology used herein is for the purpose of describing particular example embodiments only, and is not intended to be limiting. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. The terms "comprises," "comprising," "includes," "including," and "having" are inclusive and therefore specify the presence of stated features, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, steps, operations, elements, components, and/or groups thereof. The method steps, processes, and operations described herein are not to be construed as necessarily requiring their performance in the particular order described or illustrated, unless an order of performance is explicitly stated. It should also be appreciated that additional or alternative steps may be used.

Although the terms first, second, third, etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms may be only used to distinguish one element, component, region, layer or section from another region, layer or section. Terms such as "first," "second," and other numerical terms when used herein do not imply a sequence or order unless clearly indicated by the context. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the example embodiments.

For ease of description, spatially relative terms, such as "inner," "outer," "lower," "below," "upper," "above," and the like, may be used herein to describe one element or feature's relationship to another element or feature as illustrated in the figures. Such spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as "below" or "beneath" other elements or features would then be oriented "above" or "over" the other elements or features. Thus, the example term "below" may include both upper and lower orientations. The device may be otherwise oriented (rotated 90 degrees or in other directions) and the spatial relative relationship descriptors used herein interpreted accordingly.

Some terms in the embodiments of the present application are explained below to facilitate understanding by those skilled in the art.

(1) The DPF (diesel particulate filter, particulate matter trap) is used for trapping the particulate matters in the tail gas, and when the trapped particulate matters reach a certain level, passive regeneration or active regeneration is required, so that the trapping capacity of the DPF on the particulate matters is restored.

(2) Particulate matter, namely particulate matter contained in engine exhaust, generally comprises two components, namely a boot and an ash, wherein the boot refers to a part which can be burnt through regeneration, the ash refers to a non-combustible component which can be accumulated in a DPF all the time, and ash removal is needed to be carried out to a service station after a certain accumulated amount is reached.

(3) Active regeneration, namely injecting diesel oil through a back injection or seventh injection nozzle of the engine to enable the boot to react with O2 at a high temperature (more than 500 ℃), wherein the reaction generally occurs periodically;

Passive regeneration, by engine thermal management measures or when the engine is operating at a high temperature, the boot is caused to react with NO2 at a lower temperature (typically 250-450 ℃), typically continuously.

(4) CcSCR (closed coupled SELECTIVELY CATALYTIC reduction, tightly coupled selective catalytic conversion device) ccSCR is a catalyst usually installed at the forefront end of the SCR aftertreatment system, so as to fully utilize the heat in the tail gas, reduce the urea stop time, and improve the NOx conversion efficiency of the aftertreatment system at low temperature.

(5) SCR (SELECTIVELY CATALYTIC reduction, selective catalytic conversion device) SCR is a catalyst installed after ccSCR, and is an effective means for reducing the emission of nitrogen oxides of diesel engine by using selective catalytic reduction technology. An aqueous urea solution having a concentration of 32.5% is typically injected into the exhaust pipe, urea is decomposed at high temperature to produce ammonia, and NOx in the exhaust gas is reduced to nitrogen and water by the produced ammonia, thereby reducing NOx emissions.

(6) CcDOC (close coupled diesel oxide catalyst, close-coupled oxidation catalytic converter): ccDOC is used to convert NO in the exhaust gas to NO2, assisting in the normal operation of ccSCR.

(7) DOC (diesel oxide catalyst, oxidation catalytic converter) the oxidation catalytic converter can be installed before DPF for converting NO in the exhaust gas to NO2, and raising the temperature of the exhaust gas at the same time, assisting the normal operation of DPF and SCR.

(8) ASC (Ammonia SLIP CATALYST, ammonia oxidation catalyst) ASC is one of the exhaust gas post-treatment devices of diesel vehicles, and is arranged at the rear end of SCR and used for reducing the Ammonia leaked from the exhaust gas at the rear end of SCR through catalytic oxidation.

As shown in FIG. 1, the first aspect of the invention provides a post-treatment emission system for DPF active regeneration, which comprises a ccDOC system, a ccSCR system, a DOC system, a DPF system, an SCR system, an ASC system, an HC injection system 8 arranged between the ccSCR system and the DOC system and a control system respectively connected with the engine post-injection system and the HC injection system 8, wherein the ccDOC system, the ccSCR system, the DOC system, the DPF system, the SCR system, the ASC system and the HC injection system are sequentially communicated with an engine exhaust outlet through an exhaust pipe, the control system at least comprises a first temperature sensor 1 arranged in the ccDOC system, a second temperature sensor 2 arranged in the DOC system, a third temperature sensor 3 and a fourth temperature sensor 4 respectively arranged at the upstream and downstream of the ccDOC system, and a first pressure difference sensor 5 and a second pressure difference sensor 6 respectively arranged in the ccSCR system and the DPF system.

In the system, the control system is at least connected with an exhaust gas mass flow sensor arranged in the exhaust pipe, and obtains a temperature signal, a pressure difference signal and an exhaust gas mass flow signal through a first temperature sensor 1, a second temperature sensor 2, a third temperature sensor 3, a fourth temperature sensor 4, a first pressure difference sensor 5 and a second pressure difference sensor 6, and the engine post-injection system and the HC injection system 8 are designated to inject fuel according to the signals so as to execute two-stage regeneration. The regeneration method formed by the device can reduce HC entering the SCR, prevent HC poisoning and reduce the engine oil dilution risk. Meanwhile, fuel injection is carried out in two stages, the post-temperature of ccDOC is increased to 350 ℃ by means of in-cylinder post-injection, and at the moment, the SCR conversion efficiency is high, and emission is guaranteed.

Further, a fifth temperature sensor 7 is arranged at the tail end of the exhaust pipe and is electrically connected with the control system.

As shown in fig. 2-3, a second aspect of the present invention provides a method for controlling post-treatment emission of active regeneration of a DPF, implemented using a post-treatment emission system for DPF regeneration conditions as described above, comprising the steps of:

And injecting fuel to the engine cylinder through the first nozzle based on the primary injection output value, and injecting fuel to the DOC system through the second nozzle based on the secondary injection output value.

Namely, the first-stage regeneration and the second-stage regeneration are required to satisfy three conditions, namely, a vehicle condition (in a parking state), a temperature condition, and whether or not an active regeneration operation is to be performed.

In one embodiment of the present invention, as shown in FIG. 2, calculating the primary injection output value based on the exhaust gas mass flow, the temperature within the ccDOC system, and the temperature upstream of the ccDOC system comprises:

Specifically, the post-system set temperature MAP of ccDOC can be queried according to the upstream temperature of ccDOC and the exhaust gas mass flow rate to obtain the post-system set temperature of ccDOC, wherein the post-system set temperature MAP of ccDOC can be obtained by calibrating in advance, and the abscissa is the exhaust gas mass flow rate and the ordinate is the upstream temperature of ccDOC. And performing PI closed-loop control on the temperature difference value to obtain the feedback oil quantity.

In one embodiment of the present invention, as shown in fig. 3, calculating the secondary fuel injection output value based on the exhaust gas mass flow, the temperature in the DPF system, and the temperature upstream of the DOC system includes:

Specifically, the upstream set temperature MAP of the DPF system can be queried according to the upstream temperature of the DOC system and the exhaust gas mass flow, so that the upstream set temperature MAP of the DPF system can be obtained, wherein the upstream set temperature MAP of the DPF system can be obtained by calibration in advance, the abscissa of the MAP is the exhaust gas mass flow, and the ordinate is the upstream temperature of the DOC system. And performing PI closed-loop control on the temperature difference value to obtain the feedback oil quantity.

The feed-forward oil mass calculation formulas in the first-stage oil injection output value and the second-stage oil injection output value are identical, and the difference is that the exhaust mass flow of the first-stage oil injection output value and the exhaust specific constant pressure heat capacity are the exhaust mass flow of the upstream of a ccDOC system and the exhaust specific constant pressure heat capacity, and the exhaust mass flow of the second-stage oil injection output value and the exhaust specific constant pressure heat capacity are ccSCR system, the exhaust mass flow of the DOC system and the exhaust specific constant pressure heat capacity.

It should be noted that the above embodiments are merely for illustrating the technical solution of the present invention and not for limiting the same, and although the present invention has been described in detail with reference to the above embodiments, it should be understood by those skilled in the art that the technical solution described in the above embodiments may be modified or some or all of the technical features may be equivalently replaced, and these modifications or substitutions do not make the essence of the corresponding technical solution deviate from the scope of the technical solution of the embodiments of the present invention.

Claims

1. A DPF active regeneration after-treatment emission control method is characterized by adopting a DPF active regeneration after-treatment emission system, wherein the system comprises a ccDOC system, a ccSCR system, a DOC system, a DPF system, an SCR system, an ASC system and a HC injection system, wherein the ccDOC system, the ccSCR system, the DOC system, the DPF system, the SCR system and the ASC system are sequentially communicated with an engine tail gas outlet through an exhaust pipe, the HC injection system is arranged between the ccSCR system and the DOC system, and the HC injection system is respectively connected with the engine after-injection system and the HC injection system;

The method comprises the following steps:

2. The post-treatment emission control method for active regeneration of a DPF of claim 1, wherein determining whether the first-stage regeneration condition and the second-stage regeneration condition are satisfied, respectively, comprises:

When the vehicle speed is 0, the upstream temperature of the ccDOC system is higher than the ignition temperature and is in a regeneration mode, the first-stage regeneration condition is met;

3. The post-treatment emission control method for active regeneration of a DPF of claim 2, wherein the light-off temperature is set to 280 ℃.

4. The post-treatment emission control method for active regeneration of a DPF of claim 1, wherein calculating a primary injection output value based on the exhaust gas mass flow, the ccDOC in-system temperature, and the ccDOC system upstream temperature comprises:

5. The post-treatment emission control method for active regeneration of a DPF of claim 1, wherein calculating a secondary fuel injection output value based on the exhaust gas mass flow, the temperature in the DPF system, and the temperature upstream of the DOC system comprises:

6. The post-treatment emission control method for active regeneration of a DPF according to claim 4 or 5, wherein the feed-forward oil amount is calculated by the following formula:

7. The post-treatment emission control method for active regeneration of a DPF according to claim 1, wherein determining whether the first-stage regeneration condition and the second-stage regeneration condition are satisfied, respectively, and before starting the fuel injection amount calculation according to the conditions, further comprises:

8. The post-treatment emission control method for active regeneration of a DPF of claim 7, wherein said ccDOC post-system set temperature is at least 350 ℃.

9. A vehicle comprising an aftertreatment exhaust system for active regeneration of a DPF controlled by the control method of claim 1.