A post-treatment emission device and control method for active regeneration of DPF

Abstract

This application relates to the field of automotive electronics, and specifically to a post-treatment emission device with active DPF regeneration and a control method. The device comprises: a ccDOC system, a ccSCR system, a DOC system, a DPF system, an SCR system, an ASC system, an HC injection system disposed between the ccSCR and DOC systems, and a control system connected to the engine post-injection system and the HC injection system, respectively. The control system further comprises at least: 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. The above-described device enables two-stage fuel injection, reduces HC entering the SCR, prevents HC poisoning, and reduces the risk of oil dilution.

Description

Technical Field

[0001] The present application relates to the field of automotive electronics technology, and in particular to a post-processing emission device and a control method for active regeneration of a DPF. Background Art

[0002] The DPF (diesel particulate filter) is used to capture engine particulate matter, thereby reducing the amount of dust emitted into the atmosphere. The particulate matter captured in the DPF can be burned through active regeneration or passive regeneration; passive regeneration means that within a certain temperature range, the NO2 in the exhaust gas has a strong oxidizing ability on the captured particles, so NO2 can be used as an oxidant to remove the particles in the particulate filter and generate CO2, and NO2 is reduced to NO, thereby achieving the purpose of removing the particles; active regeneration refers to the use of external energy to increase the temperature inside the DPF to ignite and burn the particulate matter, which is mainly used for particulate matter that cannot be removed after passive regeneration. However, the existing technology uses DOC systems and SCR systems, and when regenerating, there is a risk of exceeding the emission standards of pollutants such as PM (particulates) and NOx (nitrogen oxides). Summary of the Invention

[0003] The object of the present invention is to provide a post-treatment emission device and a control method for active regeneration of a DPF, so as to at least partially solve the problems of the prior art.

[0004] A first aspect of the present invention provides a post-treatment emission system with active DPF regeneration, comprising: a ccDOC system, a ccSCR system, a DOC system, a DPF system, an SCR system, and an ASC system connected in sequence to the engine exhaust outlet through an exhaust pipe, an HC injection system arranged between the ccSCR system and the DOC system, and a control system connected to the engine post-injection system and the HC injection system respectively; the control system also includes at least: 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 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.

[0005] A second aspect of the present invention provides a post-treatment emission control method for active DPF regeneration, which is implemented using the post-treatment emission system in the DPF regeneration working condition as described above, and includes the following steps:

[0006] Determine whether the first-level regeneration conditions and the second-level regeneration conditions are met, and start calculating the fuel injection amount when the conditions are met;

[0007] The primary injection output value is calculated based on the exhaust gas mass flow rate, the temperature in the ccDOC system, and the temperature upstream of the ccDOC system;

[0008] The secondary injection output value is calculated based on the exhaust gas mass flow rate, the temperature in the DPF system and the temperature upstream of the DOC system;

[0009] Fuel is injected into the engine cylinders through the engine post-injection system based on the primary injection output value, and fuel is injected into the DOC system through the HC injection system based on the secondary injection output value.

[0010] The post-treatment emission control method for DPF regeneration conditions provided by the present invention may also have the following additional technical features:

[0011] In one embodiment of the present invention, determining whether the primary regeneration condition and the secondary regeneration condition are met includes:

[0012] When the vehicle speed is 0, the temperature upstream of the ccDOC system is greater than the light-off temperature and the vehicle is in regeneration mode, the first-level regeneration conditions are met;

[0013] When the vehicle speed is 0, the upstream temperature of the DOC system is greater than the ignition temperature and it is in regeneration mode, the secondary regeneration conditions are met.

[0014] In a specific embodiment of the present invention, the ignition temperature is set to 280°C.

[0015] In one embodiment of the present invention, the primary injection output value is calculated based on the exhaust gas mass flow rate, the temperature in the ccDOC system, and the temperature upstream of the ccDOC system, including:

[0016] The post-set temperature of the ccDOC system is obtained based on the upstream temperature of the ccDOC system and the exhaust gas mass flow rate;

[0017] The temperature difference is obtained based on the set temperature after the ccDOC system and the actual temperature of the ccDOC system;

[0018] The temperature difference is closed-loop controlled to obtain the feedback oil volume;

[0019] Calculate the sum of the feedback oil volume and the feedforward oil volume. The smaller value of the sum and the injection boundary is the first-stage injection output value.

[0020] In one embodiment of the present invention, the secondary injection output value is calculated based on the exhaust gas mass flow rate, the temperature in the DPF system, and the temperature upstream of the DOC system, including:

[0021] The upstream set temperature of the DPF system is obtained based on the upstream temperature of the DOC system and the exhaust gas mass flow rate;

[0022] A temperature difference is obtained based on a set temperature upstream of the DPF system and an actual temperature upstream of the DPF system;

[0023] The temperature difference is closed-loop controlled to obtain the feedback oil volume;

[0024] Calculate the sum of the feedback oil volume and the feedforward oil volume. The smaller value of the sum and the injection boundary is the secondary injection output value.

[0025] In a specific embodiment of the present invention, the feed forward oil amount is calculated by the following formula:

[0026]

[0027] Where q is the fuel mass flow rate in kg / h; c is the exhaust mass flow rate in kg / h; m is the exhaust heat capacity at constant pressure in J / (kg·°C); Δt is the temperature difference in °C; h is the calorific value of the fuel in J / kg; and η is the fuel oxidation efficiency in %.

[0028] In a specific embodiment of the present invention, whether the primary regeneration condition and the secondary regeneration condition are met are judged respectively, and before starting to calculate the injection amount when the conditions are met, the following steps are further included:

[0029] Thermal management measures are used to control the temperature upstream of the ccDOC to above the ignition temperature.

[0030] A third aspect of the present invention provides a vehicle comprising the above-mentioned DPF active regeneration after-treatment emission system.

[0031] In one embodiment of the present invention, the post-set temperature of the ccDOC system is at least 350°C.

[0032] The DPF active regeneration post-treatment emission system provided by this invention incorporates a ccDOC system and a ccSCR system between the turbocharger and the DOC system. During regeneration, fuel injection is performed in two stages: the first stage uses in-cylinder post-injection, and the second stage uses the HC injection system. This reduces HC entering the SCR, preventing HC poisoning, and also reduces the risk of oil dilution. Furthermore, the two-stage fuel injection, using in-cylinder post-injection, raises the temperature after the ccDOC to 350°C, achieving high SCR conversion efficiency and ensuring emissions. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0034] Figure 1 Schematic diagram of the post-treatment emission system for active DPF regeneration according to an embodiment of the present invention;

[0035] Figure 2 This is the calculation logic diagram of the first-stage regeneration injection amount;

[0036] Figure 3 This is the calculation logic diagram of the secondary regeneration injection amount.

[0037] 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

[0038] Exemplary embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments described herein. Rather, these embodiments are provided to enable a more thorough understanding of the present invention and to fully convey the scope of the present invention to those skilled in the art.

[0039] It should be understood that the terms used herein are for the purpose of describing specific example embodiments only and are not intended to be limiting. Unless the context clearly indicates otherwise, the singular forms "one", "an" and "said" as used herein may also be meant to include plural forms. The terms "comprise", "include", "contain" and "have" are inclusive and therefore specify the presence of stated features, steps, operations, elements and / or parts, but do not exclude the presence or addition of one or more other features, steps, operations, elements, parts, and / or combinations thereof. The method steps, processes, and operations described herein are not to be construed as necessarily requiring them to be performed in the specific order described or illustrated, unless the order of execution is clearly indicated. It should also be understood that additional or alternative steps may be used.

[0040] Although the terms first, second, third, etc. can be used in the text to describe multiple elements, components, regions, layers and / or sections, these elements, components, regions, layers and / or sections should not be limited by these terms. These terms can only be used to distinguish an element, component, region, layer or section from another region, layer or section. Unless the context clearly indicates otherwise, terms such as "first", "second" and other numerical terms do not imply order or sequence when used in the text. Therefore, the first element, component, region, layer or section discussed below can be referred to as the second element, component, region, layer or section without departing from the teaching of the example embodiments.

[0041] For ease of description, spatially relative terms may be used herein to describe the relationship of one element or feature relative to another element or feature as shown in the figures, such as "inside," "outside," "inside," "outside," "below," "beneath," "above," and the like. Such spatially relative terms are intended to include 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 flipped, an element described as "below" or "below" another element or feature would then be oriented as "above" or "above" another element or feature. Thus, the example term "below" can include both above and below orientations. The device may be otherwise oriented (rotated 90 degrees or in other orientations) and the spatially relative descriptors used herein are interpreted accordingly.

[0042] The following explains some of the terms used in the embodiments of the present application to facilitate understanding by those skilled in the art.

[0043] (1) DPF (diesel particulate filter): used to capture particulate matter in exhaust gas. When the mass of captured particulate matter reaches a certain level, passive or active regeneration is required to restore the DPF's ability to capture particulate matter.

[0044] (2) Particulate matter: The particulate matter contained in the engine exhaust generally includes two components: soot and ash. Soot generally refers to the part that can be burned through regeneration, and ash generally refers to the non-combustible component. It will continue to accumulate in the DPF. When a certain amount of accumulation is reached, it is necessary to go to a service station for cleaning.

[0045] (3) Active regeneration: diesel is injected through the engine's rear injection or seventh injector, causing the soot to react with O2 at high temperature (above 500°C), which generally occurs cyclically;

[0046] Passive regeneration: Through engine thermal management measures or when the engine is running at high temperature, soot reacts with NO2 at a lower temperature (generally 250℃-450℃), which usually occurs continuously.

[0047] (4) ccSCR (close coupled selectively catalytic reduction): ccSCR is a catalyst usually installed at the front end of the SCR after-treatment system to fully utilize the heat in the exhaust gas, reduce the urea injection stop time, and improve the NOx conversion efficiency of the after-treatment system at low temperatures.

[0048] (5) SCR (selective catalytic reduction): SCR is a catalyst installed after the ccSCR. It is a post-installed selective catalytic converter and an effective means of reducing nitrogen oxide emissions from diesel engines using selective catalytic reduction technology. Typically, a 32.5% urea aqueous solution is injected into the exhaust pipe. The urea decomposes at high temperatures to produce ammonia, which reduces NOx in the exhaust into nitrogen and water, thereby reducing NOx emissions.

[0049] (6) ccDOC (close coupled diesel oxide catalyst): ccDOC is used to convert NO in exhaust gas into NO2, assisting the normal operation of ccSCR.

[0050] (7) DOC (diesel oxide catalyst): The oxidative catalytic converter can be installed before the DPF to convert NO in the exhaust gas into NO2, while increasing the exhaust gas temperature and assisting the normal operation of the DPF and SCR.

[0051] (8) ASC (Ammonia Slip Catalyst): ASC is a type of exhaust gas aftertreatment device for diesel vehicles. It is installed at the rear end of the SCR and reduces the ammonia leaked from the exhaust gas at the rear end of the SCR through catalytic oxidation.

[0052] like Figure 1As shown, the first aspect of the present invention provides a post-treatment emission system with active DPF regeneration, comprising: a ccDOC system, a ccSCR system, a DOC system, a DPF system, an SCR system, and an ASC system connected in sequence to the engine exhaust outlet through an exhaust pipe, an HC injection system 8 arranged between the ccSCR system and the DOC system, and a control system connected to the engine post-injection system and the HC injection system 8 respectively; the control system also includes at least: 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 upstream and downstream of the ccDOC system, and a first differential pressure sensor 5 and a second differential pressure sensor 6 respectively arranged in the ccSCR system and the DPF system.

[0053] In this system, the control system is also connected to at least an exhaust gas mass flow sensor located in the exhaust pipe. It obtains temperature signals, pressure differential signals, and exhaust gas mass flow signals from a first temperature sensor 1, a second temperature sensor 2, a third temperature sensor 3, a fourth temperature sensor 4, a first differential pressure sensor 5, and a second differential pressure sensor 6. Based on these signals, the control system directs the engine's post-injection system and the HC injection system 8 to inject fuel, thereby performing a two-stage regeneration. This regeneration method, implemented by the aforementioned device, reduces HC entering the SCR, preventing HC poisoning, and mitigating the risk of oil dilution. Furthermore, fuel injection is performed in two stages, utilizing in-cylinder post-injection to raise the ccDOC post-temperature to 350°C, achieving high SCR conversion efficiency and ensuring emissions.

[0054] Furthermore, it also includes a fifth temperature sensor 7 arranged at the tail end of the exhaust pipe and electrically connected to the control system.

[0055] like Figure 2-3 As shown, the second aspect of the present invention provides a post-treatment emission control method for active DPF regeneration, which is implemented using the post-treatment emission system for DPF regeneration conditions as described above, comprising the following steps:

[0056] Determine whether the first-level regeneration conditions and the second-level regeneration conditions are met, and start calculating the fuel injection amount when the conditions are met;

[0057] The primary injection output value is calculated based on the exhaust gas mass flow rate, the temperature in the ccDOC system, and the temperature upstream of the ccDOC system;

[0058] The secondary injection output value is calculated based on the exhaust gas mass flow rate, the temperature in the DPF system and the temperature upstream of the DOC system;

[0059] Fuel is injected into the engine cylinder through the first nozzle based on the primary injection output value, and fuel is injected into the DOC system through the second nozzle based on the secondary injection output value.

[0060] In one embodiment of the present invention, determining whether the primary regeneration condition and the secondary regeneration condition are met includes:

[0061] When the vehicle speed is 0, the temperature upstream of the ccDOC system is greater than the light-off temperature and the vehicle is in regeneration mode, the first-level regeneration conditions are met;

[0062] When the vehicle speed is 0, the upstream temperature of the DOC system is greater than the ignition temperature and it is in regeneration mode, the secondary regeneration conditions are met.

[0063] That is, both the first-level regeneration and the second-level regeneration must meet three conditions, namely the vehicle condition (in the parking state), the temperature condition and whether the active regeneration operation is ready.

[0064] In a specific embodiment of the present invention, the ignition temperature is set to 280°C.

[0065] like Figure 2 As shown, in one embodiment of the present invention, the primary injection output value is calculated based on the exhaust gas mass flow rate, the temperature in the ccDOC system, and the temperature upstream of the ccDOC system, including:

[0066] The post-set temperature of the ccDOC system is obtained based on the upstream temperature of the ccDOC system and the exhaust gas mass flow rate;

[0067] The temperature difference is obtained based on the set temperature after the ccDOC system and the actual temperature of the ccDOC system;

[0068] The temperature difference is closed-loop controlled to obtain the feedback oil volume;

[0069] Calculate the sum of the feedback oil volume and the feedforward oil volume. The smaller value of the sum and the injection boundary is the first-stage injection output value.

[0070] Specifically, the ccDOC system post-set temperature MAP can be queried based on the ccDOC system upstream temperature and exhaust gas mass flow rate to obtain the ccDOC system post-set temperature. The ccDOC system post-set temperature MAP can be pre-calibrated, with the exhaust gas mass flow rate as the horizontal axis and the ccDOC system upstream temperature as the vertical axis. PI closed-loop control is performed on the temperature difference to obtain the feedback oil volume.

[0071] like Figure 3 As shown, in a specific embodiment of the present invention, the secondary injection output value is calculated based on the exhaust gas mass flow rate, the temperature in the DPF system and the upstream temperature of the DOC system, including:

[0072] The upstream set temperature of the DPF system is obtained based on the upstream temperature of the DOC system and the exhaust gas mass flow rate;

[0073] A temperature difference is obtained based on a set temperature upstream of the DPF system and an actual temperature upstream of the DPF system;

[0074] The temperature difference is closed-loop controlled to obtain the feedback oil volume;

[0075] Calculate the sum of the feedback oil volume and the feedforward oil volume. The smaller value of the sum and the injection boundary is the first-stage injection output value.

[0076] Specifically, the DPF system upstream set temperature MAP can be queried based on the DOC system upstream temperature and exhaust gas mass flow rate to obtain the DPF system upstream set temperature. The DPF system upstream set temperature MAP can be pre-calibrated, with the exhaust gas mass flow rate as the horizontal axis and the DOC system upstream temperature as the vertical axis. PI closed-loop control is performed on the temperature difference to obtain the feedback oil volume.

[0077] In a specific embodiment of the present invention, the feed forward oil amount is calculated by the following formula:

[0078]

[0079] Where q is the fuel mass flow rate in kg / h; c is the exhaust mass flow rate in kg / h; m is the exhaust heat capacity at constant pressure in J / (kg·°C); Δt is the temperature difference in °C; h is the calorific value of the fuel in J / kg; and η is the fuel oxidation efficiency in %.

[0080] The feedforward fuel calculation formulas in the first-stage injection output value and the second-stage injection output value are exactly the same. The difference is that the exhaust mass flow and its exhaust gas ratio constant-pressure heat capacity in the first-stage injection output value are the exhaust mass flow and its exhaust gas ratio constant-pressure heat capacity upstream of the ccDOC system, while the exhaust mass flow and its exhaust gas ratio constant-pressure heat capacity in the second-stage injection output value are the exhaust mass flow and its exhaust gas ratio constant-pressure heat capacity between the ccSCR system and the DOC system.

[0081] In a specific embodiment of the present invention, whether the primary regeneration condition and the secondary regeneration condition are met are judged respectively, and before starting to calculate the injection amount when the conditions are met, the following steps are further included:

[0082] Thermal management measures are used to control the temperature upstream of the ccDOC to above the ignition temperature.

[0083] In one embodiment of the present invention, the post-set temperature of the ccDOC system is at least 350°C.

[0084] A third aspect of the present invention provides a vehicle comprising the above-mentioned DPF active regeneration after-treatment emission system.

[0085] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A post-treatment emission control method for active DPF regeneration, characterized in that: The post-treatment emission system is implemented using an active DPF regeneration system, comprising: a ccDOC system, a ccSCR system, a DOC system, a DPF system, an SCR system, and an ASC system sequentially connected to the engine exhaust outlet through an exhaust pipe; an HC injection system disposed between the ccSCR system and the DOC system; and a control system respectively connected to the engine post-injection system and the HC injection system; the control system further comprises at least: a first temperature sensor disposed in the ccDOC system, a second temperature sensor disposed in the DOC system, a third temperature sensor and a fourth temperature sensor disposed upstream and downstream of the ccDOC system, respectively; and a first differential pressure sensor and a second differential pressure sensor disposed in the ccSCR system and the DPF system, respectively. The method comprises the following steps: Determine whether the first-level regeneration conditions and the second-level regeneration conditions are met, and start calculating the injection amount when the conditions are met; The primary injection output value is calculated based on the exhaust gas mass flow rate, the temperature in the ccDOC system, and the temperature upstream of the ccDOC system; The secondary injection output value is calculated based on the exhaust gas mass flow rate, the temperature in the DPF system and the temperature upstream of the DOC system; Fuel is injected into the engine cylinders through the engine post-injection system based on the primary injection output value, and fuel is injected into the DOC system through the HC injection system based on the secondary injection output value.

2. The post-treatment emission control method for active DPF regeneration according to claim 1, characterized in that: Determining whether the first-level regeneration conditions and the second-level regeneration conditions are met include: When the vehicle speed is 0, the ccDOC system upstream temperature is greater than the light-off temperature and the vehicle is in regeneration mode, the first-level regeneration conditions are met; When the vehicle speed is 0, the upstream temperature of the DOC system is greater than the ignition temperature and it is in regeneration mode, the secondary regeneration conditions are met.

3. The post-treatment emission control method for active DPF regeneration according to claim 2, characterized in that: The ignition temperature was set to 280°C.

4. The post-treatment emission control method for active DPF regeneration according to claim 1, characterized in that: The primary injection output values ​​calculated based on the exhaust gas mass flow rate, the temperature inside the ccDOC system, and the temperature upstream of the ccDOC system include: The post-set temperature of the ccDOC system is obtained based on the upstream temperature of the ccDOC system and the exhaust gas mass flow rate; The temperature difference is obtained based on the set temperature after the ccDOC system and the actual temperature of the ccDOC system; The temperature difference is closed-loop controlled to obtain the feedback oil volume; Calculate the sum of the feedback oil volume and the feedforward oil volume. The smaller value of the sum and the injection boundary is the first-stage injection output value.

5. The post-treatment emission control method for active DPF regeneration according to claim 1, characterized in that: The secondary injection output values ​​calculated based on the exhaust gas mass flow rate, the temperature in the DPF system, and the temperature upstream of the DOC system include: The upstream set temperature of the DPF system is obtained based on the upstream temperature of the DOC system and the exhaust gas mass flow rate; A temperature difference is obtained based on a set temperature upstream of the DPF system and an actual temperature upstream of the DPF system; The temperature difference is closed-loop controlled to obtain the feedback oil volume; Calculate the sum of the feedback oil volume and the feedforward oil volume. The smaller value of the sum and the injection boundary is the secondary injection output value.

6. The post-treatment emission control method for active DPF regeneration according to claim 4 or 5, characterized in that: The feed forward oil quantity is calculated by the following formula: Where q is the fuel mass flow rate in kg / h; c is the exhaust mass flow rate in kg / h; m is the exhaust heat capacity at constant pressure in J / (kg·°C); Δt is the temperature difference in °C; h is the calorific value of the fuel in J / kg. η is the fuel oxidation efficiency, %.

7. The post-treatment emission control method for active DPF regeneration according to claim 1, characterized in that: It is judged whether the first-level regeneration condition and the second-level regeneration condition are met respectively, and before the fuel injection amount calculation starts when the conditions are met, it also includes: Thermal management measures are used to control the temperature upstream of the ccDOC to above the ignition temperature.

8. The post-treatment emission control method for active DPF regeneration according to claim 7, characterized in that: The ccDOC system post-set temperature is at least 350°C.

9. A vehicle, characterized in that: The invention relates to an after-treatment emission system comprising a DPF active regeneration system controlled by the control method described in claim 1.

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