Exhaust gas treatment system for an engine, control method, and storage medium

Abstract

This application discloses an aftertreatment system, control method, and storage medium for an engine exhaust pipe. The aftertreatment system includes a first branch and a second branch connected in parallel. The input ends of the first and second branches are connected to the engine exhaust pipe. The first branch includes a first nitrogen oxide purification module. The second branch has a first switch module and a pollutant pre-purification module connected in series along the exhaust flow direction. The output ends of the first and second branches have a particulate matter capture module and a second nitrogen oxide purification module connected in series. The embodiments of this application can greatly improve the purification efficiency of exhaust gas.

Description

Technical Field

[0001] This application relates to the field of exhaust gas aftertreatment technology, specifically to an aftertreatment system, control method and storage medium for an engine exhaust pipe. Background Technology

[0002] Currently, diesel engines commonly employ a series aftertreatment system of "DOC + DPF + SCR & ASC". However, this structure has the following technical drawbacks: During engine cold starts, the exhaust temperature is low. The DOC (Diesel Oxidation Catalyst) and DPF (Diesel Particulate Filter) have large heat capacities, resulting in a gradual temperature drop in the exhaust. This means that it takes a considerable amount of time (e.g., over 200 seconds) for the SCR (Selective Catalytic Reduction) inlet temperature to reach the urea injection temperature (e.g., 185°C). During this period, NOx conversion efficiency is extremely low, leading to a large amount of NOx being directly released into the atmosphere.

[0003] Therefore, existing diesel engine after-treatment systems suffer from low pollutant purification rates. Summary of the Invention

[0004] In view of this, this application proposes an after-treatment system, control method and storage medium for engine exhaust pipe, in order to solve the problem of low pollutant purification rate in existing diesel engine after-treatment systems.

[0005] The first aspect of this application provides an after-treatment system for an engine exhaust pipe, the after-treatment system including a first branch and a second branch arranged in parallel, the input ends of the first branch and the second branch being used to connect to the engine exhaust pipe; The first branch includes a first nitrogen oxide purification module; The second branch is connected in series with the first switch module and the pollutant pre-purification module along the exhaust flow direction; The output terminals of the first branch and the second branch are connected in series with a particulate matter collection module and a second nitrogen oxide purification module.

[0006] The embodiments of this application achieve the following technical effects by connecting the DOC branch (i.e., the second branch in which the first switching module and the pollutant pre-purification module are connected in series along the exhaust flow direction) and the SCR branch (i.e., the first branch containing the first nitrogen oxide purification module) in parallel: 1. By setting up a pre-stage SCR (i.e. the first nitrogen oxide purification module mentioned above) and a post-stage SCR (i.e. the second nitrogen oxide purification module mentioned above), the pre-stage SCR can remove most of the NOx (usually 50-70%), and the post-stage SCR only needs to clean up the tail end, thereby greatly reducing the pressure on the post-stage SCR and improving the emission robustness of the aftertreatment system. In the two applications, the PN generated by the pre-stage SCR urea injection is captured by the DPF, which can reduce the PN emission rate to a certain extent.

[0007] 3. The pre-stage SCR is directly connected to the exhaust pipe through a valve, which makes the NO2 concentration at the inlet of the pre-stage SCR extremely low. It hardly generates NH4NO3 with the NH3 injected by urea. Therefore, it is impossible to obtain N2O through "NH4NO3 decomposition under temperature fluctuation conditions", thus greatly reducing the cold state N2O emission rate. 4. Since the upstream SCR has already treated most of the NOx, the urea injection amount of the downstream SCR can be reduced (e.g., by 30-50%). With the reduction of the urea injection amount of the downstream SCR, the ammonia oxidation side reaction caused by over-injection of urea will be weakened accordingly, thereby inhibiting the generation of high-temperature N2O and achieving the goal of reducing the N2O emission rate.

[0008] In this embodiment of the application, for any one of the first nitrogen oxide purification module and the second nitrogen oxide purification module, the nitrogen oxide purification module includes a selective catalytic reduction device and an ammonia purifier connected in series. The selective catalytic reduction device is used to purify nitrogen oxides in exhaust gas; The ammonia purifier is used to purify the ammonia generated by the selective catalytic reduction unit during the purification of nitrogen oxides.

[0009] In this embodiment of the application, the first branch further includes a first urea injection device and a first mixer arranged sequentially along the exhaust flow direction at the input end of the first nitrogen oxide purification module; a second urea injection device and a second mixer are arranged between the particulate matter collection module and the second nitrogen oxide purification module.

[0010] In this embodiment of the application, a temperature measuring module is provided between the particulate matter collection module and the second nitrogen oxide purification module.

[0011] In this embodiment of the application, the first branch further includes a second switch module disposed at the input end of the first urea injection device.

[0012] The second aspect of this application provides a control method for an aftertreatment system of an engine exhaust pipe, characterized in that the control method is applied to the aftertreatment system of the engine exhaust pipe described in the first aspect embodiment; the control method includes: Obtain the engine's current operating mode; If the current operating mode is cold start mode, then the first switch module is turned off. If the current working mode is not the cold start mode, then determine whether the input temperature of the second nitrogen oxide purification module is less than a preset temperature threshold. If the input temperature is less than the preset temperature threshold, the first switch module is controlled to turn on, and the valve opening of the first switch module is adjusted according to the input temperature. If the temperature at the input terminal is greater than or equal to the preset temperature threshold, then the first switch module is controlled to be fully open.

[0013] An embodiment of the third aspect of this application provides a control method for an aftertreatment system of an engine exhaust pipe, characterized in that the control method is applied to the aftertreatment system of the engine exhaust pipe described in the embodiment of the first aspect; the control method includes: Obtain the engine's current operating mode; Determine whether the current working mode is active regeneration mode; the active regeneration mode refers to the working process in which the engine management system actively intervenes to restore the particulate filtration capacity when the amount of carbon soot accumulated in the particulate trap reaches a preset threshold. If the current operating mode is the active regeneration mode, then the first switch module is fully turned on and the second switch module is turned off. If the current working mode is not the active regeneration mode, then determine whether the current working mode is the cold start mode; If the current working mode is the cold start mode, then control the first switch module to turn off and control the second switch module to be fully open; If the current working mode is not the cold start mode, then the first switch module and the second switch module are turned on simultaneously, and the valve opening of the first switch module and the second switch module is controlled according to the input temperature of the second nitrogen oxide purification module and the carbon load of the particulate matter collection module.

[0014] In this embodiment, controlling the valve opening of the first and second switching modules based on the input temperature of the second nitrogen oxide purification module and the carbon load of the particulate matter collection module includes: If the input temperature of the second nitrogen oxide purification module is less than the preset temperature threshold, the valve opening of the first switch module is adjusted according to the input temperature, and the second switch module is controlled to be fully open. If the input temperature of the second nitrogen oxide purification module is greater than or equal to the preset temperature threshold, then it is determined whether the carbon loading of the particulate matter capture module is greater than the preset carbon loading. If the carbon load is greater than the preset carbon load, then the first switch module is fully opened and the valve opening of the second switch module is reduced. If the carbon loading is less than or equal to the preset carbon loading, then control the first switch module and the second switch module to be fully open.

[0015] In this embodiment, when the engine is in active regeneration mode, the engine management system actively intervenes to remove carbon buildup inside the DPF in order to remove carbon soot accumulation. This is achieved by injecting fuel after the cylinder (HC, Hydrocarbon) or before the DOC, causing the exhaust gas to oxidize and release heat in the DOC, forcibly raising the DPF inlet temperature to 550–650 °C. This directly burns the carbon soot (C + O2 → CO2), thereby removing the carbon soot inside the DPF and restoring its filtering capacity. However, during this process, due to the exhaust flow direction of the traditional aftertreatment system ("DOC + DPF + SCR & ASC"), fuel flows through the SCR with the exhaust gas. The fuel condenses below 200 °C, covering the active sites of the SCR catalyst, leading to sulfur poisoning and pore blockage, thus causing NO to accumulate. X The conversion efficiency is greatly reduced. To address this technical problem, the embodiments of this application close the SCR branch and open the DOC branch, so that the exhaust gas only flows through the DOC branch, and the upstream SCR is physically isolated and does not come into contact with the fuel at all, thereby avoiding problems such as catalyst poisoning and blockage.

[0016] In this embodiment, the traditional aftertreatment system, due to the exhaust flow direction of "DOC+DPF+SCR&ASC," requires the emitted exhaust gas to first heat the DOC and then the DPF. The heat is trapped by the two stages of the carrier, resulting in a slow heating rate at the SCR inlet, taking a long time to reach the urea injection temperature (e.g., 185°C). During this period, the NOx conversion efficiency is extremely low, causing a large amount of NOx to be directly released into the atmosphere, resulting in low pollutant purification rates. To address this technical problem, this embodiment closes the DOC branch and opens the SCR branch, allowing the exhaust gas to bypass the DOC and directly reach the SCR inlet. This increases the SCR heating rate, significantly shortening the injection time and helping to improve NOx conversion efficiency.

[0017] An embodiment of the fourth aspect of this application provides a computer device including a memory and a processor, the memory and the processor being communicatively connected to each other, the memory storing computer instructions, and the processor executing the computer instructions to perform the control method of the engine exhaust pipe aftertreatment system described in the second or third aspect above.

[0018] An embodiment of the fifth aspect of this application provides a computer-readable storage medium storing computer instructions for causing a computer to execute the control method of the engine exhaust pipe aftertreatment system described in the second or third aspect above.

[0019] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0020] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of this application. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings: Figure 1 A schematic diagram of the structure of an aftertreatment system for an engine exhaust pipe according to an embodiment of this application is shown; Figure 2 A schematic diagram of the structure of another engine exhaust pipe aftertreatment system provided in one embodiment of this application is shown; Figure 3 A schematic diagram of the structure of another engine exhaust pipe aftertreatment system provided in an embodiment of this application is shown; Figure 4 A schematic flowchart of a control method for an engine exhaust pipe aftertreatment system according to an embodiment of this application is shown. Figure 5 A schematic flowchart of a control method for an aftertreatment system for an engine exhaust pipe according to an embodiment of this application is shown. Figure 6 This illustration shows a schematic diagram of the structure of a computer device according to an embodiment of this application; Figure 7 A schematic diagram of a storage medium provided in one embodiment of this application is shown. Detailed Implementation

[0021] Exemplary embodiments of this application will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of this application are shown in the drawings, it should be understood that this application may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of this application and to fully convey the scope of this application to those skilled in the art.

[0022] It should be noted that, unless otherwise stated, the technical or scientific terms used in this application shall have the ordinary meaning as understood by one of ordinary skill in the art to which this application pertains.

[0023] The following describes the relevant terms and technical scenarios involved in the embodiments of this application.

[0024] DOC (Diesel Oxidation Catalyst): Through catalytic oxidation reactions, it converts carbon monoxide (CO), hydrocarbons (HC), and some particulate matter (PM) in diesel engine exhaust into carbon dioxide (CO2) and water (H2O), and oxidizes NO into NO2.

[0025] DPF (Diesel Particulate Filter): Used to capture and remove particulate matter (PM) (including soot, ash, soluble organic matter SOF, etc.) from diesel exhaust.

[0026] SCR (Selective Catalytic Reduction): A device that converts nitrogen oxides (NOx) in exhaust gas into harmless nitrogen (N2) and water (H2O) by injecting urea solution (AdBlue) into the exhaust gas.

[0027] SCR fast reaction: The reaction of NH3 with NO2 to produce N2 and H2O has a faster reaction rate than other SCR reactions such as the reaction of NH3 with NO and the reaction of NH3 with NO and NO2.

[0028] ASC (Ammonia Slip Catalyst): Used to treat leaked ammonia by oxidizing it into N2.

[0029] Active regeneration: When the carbon load inside the particulate filter reaches the limit, HC is injected into the exhaust gas. The precious metal oxide coating oxidizes the HC and releases heat, thereby raising the temperature of the particulate filter and oxidizing the carbon soot into CO2.

[0030] Passive regeneration: using a precious metal oxide coating to oxidize NO in the exhaust gas into NO2, thereby achieving carbon removal in the particulate filter at low temperatures (2C+2NO2→2CO2+N2).

[0031] MFC (Mixed Functional Catalyst): Based on SCR catalyst, noble metals such as Pd are added, so that it can not only reduce NOx, but also oxidize HC and desulfurize, avoiding the impact of HC on NOx conversion efficiency when SCR is placed before DOC.

[0032] NOx: Nitrogen oxides, combustion products of engines.

[0033] N2O: Nitrous oxide, commonly known as laughing gas, is a by-product of the NOx reduction process by SCR catalyst.

[0034] PN (Particulate Number): The number concentration of suspended particulate matter in diesel engine exhaust or air, typically used to measure the pollution level of ultrafine particles (such as nanoparticles).

[0035] Urea: Used in diesel vehicle SCR systems, it is injected into the exhaust gas before the SCR system to reduce nitrogen oxide (NOx) emissions through a chemical reaction.

[0036] Currently, the "DOC + DPF + SCR & ASC" series aftertreatment system for diesel engines still has the following technical drawbacks: 1. Because urea injection contributes to the particulate number (PN), and the SCR is placed after the DPF output, some of the PN generated by urea injection cannot be effectively captured by the DPF and is discharged with the exhaust gas; 2. The traditional "DOC→DPF→SCR" sequence artificially generates a large amount of N2O: DOC oxidizes NO to NO2, and the SCR is at the DOC output. In the low-temperature section, the NO2 concentration is high, which reacts with the over-injected NH3 to generate a large amount of ammonium nitrate. The ammonium nitrate then suddenly decomposes during temperature fluctuations, instantly releasing a large amount of N2O. Furthermore, to ensure NOx conversion rate, existing technologies often employ urea over-injection, which leads to an increase in N2O generated by the ammonia oxidation side reaction.

[0037] To address the aforementioned technical deficiencies, this application provides an after-treatment system for an engine exhaust pipe and a control method for the after-treatment system, which can significantly improve the pollutant purification rate of the after-treatment system.

[0038] This application provides an after-treatment system for an engine exhaust pipe. Figure 1 This is a schematic diagram of the structure of the aftertreatment system of the engine exhaust pipe according to an embodiment of this application, as shown below. Figure 1As shown, the aftertreatment system includes a first branch and a second branch connected in parallel. The input ends of the first branch and the second branch are used to connect to the engine exhaust pipe. The first branch includes a first nitrogen oxide purification module 101. The second branch is connected in series with a first switch module 102 and a pollutant pre-purification module 103 along the exhaust flow direction. The output ends of the first branch and the second branch are connected in series with a particulate matter collection module 104 and a second nitrogen oxide purification module 105.

[0039] In some specific embodiments, for either the first nitrogen oxide purification module 101 or the second nitrogen oxide purification module 105, the nitrogen oxide purification module includes a selective catalytic reduction device and an ammonia purifier connected in series. The selective catalytic reduction device is used to purify nitrogen oxides in the exhaust gas; the ammonia purifier is used to purify the ammonia generated by the selective catalytic reduction device during the nitrogen oxide purification process.

[0040] In some specific embodiments, the selective catalytic reduction device in the nitrogen oxide purification module can be either an SCR catalyst or a composite catalyst MFC.

[0041] In some specific embodiments, the first nitrogen oxide purification module 101 includes a selective catalytic reduction unit (MFC) and an ammonia purifier (ASC), for example... Figure 2 The "MFC&ASC" in the text; the second nitrogen oxide purification module 105 includes a selective catalytic reduction (SCR) and an ammonia purifier (ASC), namely Figure 2 "SCR&ASC" in the text.

[0042] In some specific embodiments, both the first nitrogen oxide purification module 101 and the second nitrogen oxide purification module 105 include a selective catalytic reduction (SCR) and an ammonia purifier (ASC), i.e. Figure 3 "SCR&ASC" in the text.

[0043] Specifically, composite catalysts (MFCs) possess the functions of oxidizing HC and reducing NOx. They are generally based on SCR catalysts with the addition of the noble metal palladium (Pd), thereby enabling the upstream SCR (i.e., Figure 2 The “MFC&ASC” in the text has the functions of HC oxidation and desulfurization, avoiding the impact of HC injection and covering on NOx conversion efficiency during DPF active regeneration.

[0044] In some specific embodiments, the first branch further includes a first urea injection device and a first mixer, sequentially arranged along the exhaust flow direction at the input end of the first nitrogen oxide purification module 101, for example... Figure 2A urea injector and mixer are installed at the input of "MFC&ASC"; a second urea injector and a second mixer are provided between the particulate matter collection module 104 and the second nitrogen oxide purification module 105, for example... Figure 2 The urea injector and mixer is located between "DPF" and "SCR&ASC".

[0045] In the embodiments of this application, the SCR catalytic reaction is essentially the reaction of ammonia (NH3) with nitrogen oxides (NO). X The selective reduction reaction of ammonia is necessary, but the vehicle system cannot directly carry high-pressure ammonia gas (which is highly toxic, corrosive, and has a high storage risk). Therefore, urea aqueous solution is used as a safe and stable liquid precursor.

[0046] The core purpose of setting up a urea injection device and mixer before the SCR (Selective Catalytic Reduction) is to efficiently convert the urea aqueous solution into a uniformly distributed ammonia gas (NH3), providing an ideal reducing agent concentration field for the SCR catalytic reaction, as shown below: Urea droplets decompose into ammonia and isocyanic acid (HNCO) at temperatures above 180°C, as shown in the following chemical formulas: CO(NH2)2→ NH3+ HNCO HNCO further reacts with water vapor to produce NH3, which is used as a reducing agent in the SCR catalytic reaction. HNCO + H2O → NH3 + CO2 The purpose of the mixer is to completely decompose uric acid into NH3 and distribute it evenly (e.g., NH3 uniformity at the front cross-section of the SCR carrier >95%) in the exhaust gas. Inhomogeneity can cause the following problems: localized excessive NH3 concentration → ammonia leakage (>10ppm), localized dilution → NO. X Conversion efficiency <70%.

[0047] The catalytic reaction stages of SCR (Selective Catalytic Reduction) are as follows: NH3 and NO X Selective reduction occurs on the surface of copper / iron zeolite catalysts, and the main reactions are: Standard reaction (stoichiometric ratio 1:1) 4NO + 4NH3 + O2 → 4N2 + 6H2O When the NO2 concentration is low, more than 90% of NO... X This path was used to restore the original state.

[0048] Rapid response (requires NO2) NO + NO2 + 2NH3 → 2N2 + 3H2O When DOC provides NO2 so that NO / NO2≈1:1, the reaction rate increases by 17 times, which is the key to efficient operation in the low-temperature range (180-250℃).

[0049] In some specific embodiments, the particulate matter collection module 104 is a diesel particulate filter, for example... Figure 2 The "DPF" in the text refers to the primary pollutant purification module 103, which is a diesel oxidation catalyst, for example. Figure 2 The "DOC" in the text.

[0050] In some specific embodiments, a temperature measuring module is provided between the particulate matter collection module 104 and the second nitrogen oxide purification module 105, for example... Figure 2 The temperature sensor in the middle.

[0051] In some specific embodiments, the first branch further includes a second switch module disposed at the input end of the first urea injection device, for example... Figure 3 Control valve 2 in the middle.

[0052] In some specific embodiments, the engine is a diesel engine.

[0053] In this embodiment, the first nitrogen oxide purification module 101 in the first branch and the pollutant pre-purification module 103 in the second branch are connected in parallel. Compared with the traditional after-treatment system, this does not increase the length of the after-treatment system and is convenient for vehicle layout.

[0054] The aftertreatment system corresponding to the above engine exhaust pipe (e.g.) Figure 2 As shown in the figure, this application embodiment also provides a control method for an aftertreatment system of an engine exhaust pipe. Figure 4 As shown, the control method for the aftertreatment system of the engine exhaust pipe includes: Step S201: Obtain the current operating mode of the engine.

[0055] Specifically, the current operating modes include, but are not limited to, cold start mode. Cold start mode can be understood as the operating phase of an engine after a long period of inactivity (e.g., ≥12 hours), from the initial start at ambient temperature (e.g., 25°C) until the coolant temperature reaches 70°C or the exhaust temperature rises to the catalyst ignition point (e.g., 180°C).

[0056] Step S202: If the current working mode is cold start mode, then control the first switch module 102 to turn off.

[0057] Specifically, traditional aftertreatment systems, due to the exhaust flow direction of "DOC+DPF+SCR&ASC," require the emitted exhaust gas to first heat the DOC and then the DPF. Heat is trapped by the two stages of the carrier, and the SCR inlet heating rate is slow, taking a long time to reach the urea injection temperature (e.g., 185°C). During this period, the NOx conversion efficiency is extremely low, resulting in a large amount of NOx being directly released into the atmosphere, causing a low pollutant purification rate. To address this technical problem, this application's embodiment closes the second branch (i.e.,... Figure 2 The branch where the DOC is located ensures that the engine exhaust gas does not flow through the DOC and goes directly to the SCR inlet, thereby increasing the SCR heating rate and greatly shortening the injection start-up time, which helps to improve the NOx conversion efficiency.

[0058] Step S203: If the current working mode is not the cold start mode, then determine whether the input temperature of the second nitrogen oxide purification module 105 is less than a preset temperature threshold.

[0059] Specifically, the preset temperature threshold can be set according to the actual situation. For example, the preset temperature threshold can be set to the urea spraying temperature, i.e., 185℃.

[0060] More specifically, the input temperature of the second nitrogen oxide purification module 105 can be measured by a temperature sensing module (e.g., Figure 2 The temperature sensor in the middle is used to determine this.

[0061] Step S204: If the input terminal temperature is less than the preset temperature threshold, control the first switch module 102 to turn on, and adjust the valve opening of the first switch module 102 according to the input terminal temperature.

[0062] Specifically, the valve opening of the first switch module 102 can be determined based on the temperature difference between the input temperature and a preset temperature threshold. The larger the temperature difference, the smaller the valve opening. The specific correspondence between the temperature difference and the valve opening can be set according to the situation and is not specifically limited here. For example, when the input temperature is 175℃, the temperature difference is 185℃-180℃=5℃, and the corresponding valve opening is 95%. As another example, when the input temperature is 160℃, the temperature difference is 185℃-160℃=25℃, and the corresponding valve opening is 75%.

[0063] More specifically, when the input temperature of the second nitrogen oxide purification module 105 is lower than the preset temperature threshold, the NOx treatment effect of the second nitrogen oxide purification module 105 is poor. Therefore, it is necessary to improve the NOx treatment efficiency of the first nitrogen oxide purification module 101, thereby improving the NOx treatment efficiency of the entire post-treatment system. This is achieved by controlling the first switch module 102 to turn on and adjusting the valve opening of the first switch module 102 according to the input temperature.

[0064] Step S205: If the temperature at the input terminal is greater than or equal to the preset temperature threshold, then control the first switch module 102 to be fully open.

[0065] The aftertreatment system corresponding to the above engine exhaust pipe (e.g.) Figure 3 As shown in the figure, this application embodiment also provides a control method for an aftertreatment system of an engine exhaust pipe. Figure 5 As shown, the control method for the aftertreatment system of the engine exhaust pipe includes: Step 301: Obtain the current operating mode of the engine.

[0066] Specifically, the current operating modes include, but are not limited to, active regeneration mode, cold start mode, and normal operation mode.

[0067] Step 302: Determine whether the current working mode is active regeneration mode.

[0068] Specifically, the active regeneration mode refers to the process by which the engine management system actively intervenes to restore the particulate filter's filtration capacity when the amount of carbon soot accumulated in the particulate filter reaches a preset threshold. For example, it automatically raises the temperature of the exhaust gas from the engine to above 500–550°C to burn off the carbon soot accumulated in the particulate filter, thereby restoring the particulate filter's filtration capacity.

[0069] Step 303: If the current working mode is the active regeneration mode, then control the first switch module 102 to be fully open and control the second switch module to be closed.

[0070] Specifically, when the engine is in active regeneration mode, in order to remove the carbon buildup inside the DPF, the engine management system actively intervenes by injecting fuel after the cylinder (HC, Hydrocarbon) or before the DOC, causing the exhaust to oxidize and release heat in the DOC, forcibly raising the DPF inlet temperature to 550–650℃, directly burning the carbon soot (C + O2 → CO2), thereby removing the carbon soot inside the DPF and restoring its filtering capacity. However, in this process, due to the exhaust flow direction of the traditional aftertreatment system's "DOC + DPF + SCR & ASC", fuel will flow with the exhaust gas through the SCR. The fuel condenses below 200℃, covering the active sites of the SCR catalyst, leading to sulfur poisoning and pore blockage, thus causing NO to be released. X The conversion efficiency is greatly reduced. To address this technical problem, this application embodiment closes the SCR branch (i.e., the first branch mentioned above) and opens the DOC branch (i.e., the second branch mentioned above), so that the exhaust gas only flows through the DOC branch. The upstream SCR is physically isolated and does not come into contact with fuel at all, avoiding problems such as catalyst poisoning and blockage, thereby improving NO conversion efficiency. X Conversion efficiency.

[0071] Step 304: If the current working mode is not the active regeneration mode, then determine whether the current working mode is the cold start mode.

[0072] Step 305: If the current working mode is the cold start mode, then control the first switch module 102 to turn off and control the second switch module to turn on fully.

[0073] Specifically, under the condition that the first switch module 102 is closed and the second switch module is fully open, Figure 3 The post-processing system structure shown is equivalent to Figure 2 Given the post-processing system structure shown, the specific implementation of step 305 can refer to step S102 above, and will not be repeated here.

[0074] Step 306: If the current working mode is not the cold start mode, then the first switch module 102 and the second switch module are turned on simultaneously, and the valve opening of the first switch module 102 and the second switch module is controlled according to the input temperature of the second nitrogen oxide purification module 105 and the carbon load of the particulate matter collection module 104.

[0075] In some specific embodiments, step S306 above includes steps S3061-S3064: Step S3061: If the input temperature of the second nitrogen oxide purification module 105 is less than a preset temperature threshold, the valve opening of the first switch module 102 is adjusted according to the input temperature, and the second switch module is fully opened.

[0076] Specifically, the implementation of step S3061 is the same as that of step S204, and will not be repeated here.

[0077] Step S3062: If the input temperature of the second nitrogen oxide purification module 105 is greater than or equal to the preset temperature threshold, then determine whether the carbon loading of the particulate matter collection module 104 is greater than the preset carbon loading.

[0078] Specifically, the preset carbon loading can be set according to actual conditions. For example, the preset carbon loading can be the product of the carbon loading that triggers the active regeneration mode and a preset ratio. The preset ratio is greater than 50% and less than 100%.

[0079] Step S3063: If the carbon load is greater than the preset carbon load, then control the first switch module 102 to be fully open and reduce the valve opening of the second switch module.

[0080] Specifically, when the carbon load exceeds the preset carbon load, the NO emission of the pre-stage SCR (i.e., the first nitrogen oxide purification module 101) in the first branch needs to be reduced. X This improves processing efficiency and enhances the conversion efficiency of NO from DOC (i.e., pollutant pre-purification module 103) in the second branch, thereby facilitating the passive regeneration of DPF (i.e., particulate matter capture module 104) and extending the active regeneration cycle of DPF. To achieve this, under the condition that "carbon load is greater than the preset carbon load", the first switch module 102 is fully opened, and the valve opening of the second switch module is reduced.

[0081] Step S3064: If the carbon loading is less than or equal to the preset carbon loading, then control the first switch module 102 and the second switch module to be fully open.

[0082] Specifically, when the first switch module 102 and the second switch module are fully open, it indicates that the engine's current operating mode is the normal operating mode (neither active regeneration mode nor cold start mode). Through the engine exhaust pipe aftertreatment system and its control method in this embodiment, the following technical effects can be achieved: 1. The pre-stage SCR (i.e., the first nitrogen oxide purification module 101 in the first branch above) removes most of the NOx (usually 50-70%), and the post-stage SCR (i.e., the second nitrogen oxide purification module 105 above) only needs to clean up the tail end, which can greatly reduce the pressure on the post-stage SCR and improve the emission robustness of the aftertreatment system.

[0083] 2. In traditional aftertreatment systems, since the SCR is located after the output of the DPF, the PN generated by the SCR urea injection is directly discharged into the atmosphere. However, in the present application, the PN generated by the pre-stage SCR urea injection is captured by the DPF, which can reduce the PN emission rate to a certain extent.

[0084] 3. The input of the pre-stage SCR is directly connected to the engine exhaust pipe via a valve, and is not connected to the output of the DOC. Therefore, the NO2 concentration at the inlet of the pre-stage SCR is extremely low, and it hardly generates NH4NO3 with the NH3 injected by urea. As a result, it is impossible to generate N2O through "NH4NO3 decomposition under temperature fluctuation conditions", thus greatly reducing the cold N2O emission rate.

[0085] 4. Since the upstream SCR has already treated most of the NOx, the urea injection rate of the downstream SCR will be reduced (e.g., 30-50%). With the reduction in the urea injection rate of the downstream SCR, the ammonia oxidation side reaction caused by over-injection of urea will be weakened accordingly, thereby inhibiting the generation of high-temperature N2O and achieving the goal of reducing the high-temperature N2O emission rate.

[0086] In this embodiment, cold N2O emissions are primarily based on the ammonium nitrate decomposition pathway, as shown below: NO2 + NH3 → NH4NO3 (solid sediment) NH4NO3 → N2O + 2H2O (decomposes upon temperature fluctuation) The key to achieving cold N2O emissions lies in: 1. High NO2 concentration: The DOC located before the SCR will oxidize the NO in the exhaust gas into NO2, which will then provide raw materials for the formation of ammonium nitrate required by the SCR. 2. Temperature window: SCR catalyst activity is low at 150–250℃, NH3 cannot effectively reduce NOx, but instead reacts with NO2 to generate NH4NO3 which is deposited on the catalyst surface; 3. Triggered decomposition: When the operating conditions change (such as rapid acceleration) and the discharge temperature rises sharply, the sediment decomposes and releases N2O instantaneously.

[0087] In this embodiment of the application, high-temperature N2O emissions are mainly based on the direct oxidation pathway of ammonia, as shown below: 4NH3 + 3O2 → 2N2O + 6H2O (side reaction) 4NH3 + 5O2 → 4NO + 6H2O (a more violent side reaction) The key to achieving high-temperature N2O emissions lies in: 1. Excess NH3: To achieve high NOx conversion efficiency, urea is often over-sprayed, with an NH3 / NOx molar ratio > 1.05; 2. High temperature (e.g., temperature > 400℃): When the catalyst activity is too high, the main SCR reaction (reduction) and the side reaction (oxidation) compete for energy, and some NH3 is oxidized by O2 to N2O instead of N2.

[0088] The above comparison shows that the generation of cold N2O needs to be suppressed from the raw material end (NO2), while the generation of high-temperature N2O needs to be suppressed from the dosage end (NH3).

[0089] This application also provides a computer device for executing the control method of the above-described engine exhaust pipe aftertreatment system. Please refer to... Figure 6 This illustrates a schematic diagram of a computer device provided by some embodiments of this application. For example... Figure 6 As shown, the computer device 6 includes: a processor 600, a memory 601, a bus 602, and a communication interface 603. The processor 600, the communication interface 603, and the memory 601 are connected via the bus 602. The memory 601 stores a computer program that can run on the processor 600. When the processor 600 runs the computer program, it executes the control method of the aftertreatment system of the engine exhaust pipe provided in any of the foregoing embodiments of this application.

[0090] The memory 601 may include high-speed random access memory (RAM) or non-volatile memory, such as at least one disk storage device. Communication between this system network element and at least one other network element is achieved through at least one communication interface 603 (which can be wired or wireless), such as the Internet, wide area network, local area network, or metropolitan area network.

[0091] Bus 602 can be an ISA bus, PCI bus, or EISA bus, etc. The bus can be divided into an address bus, a data bus, a control bus, etc. Memory 601 is used to store programs. After receiving an execution instruction, processor 600 executes the program. The control method of the engine exhaust pipe aftertreatment system disclosed in any of the foregoing embodiments can be applied to processor 600, or implemented by processor 600.

[0092] The processor 600 may be an integrated circuit chip with signal processing capabilities. In implementation, each step of the above method can be completed by the integrated logic circuitry in the hardware of the processor 600 or by instructions in software form. The processor 600 may be a general-purpose processor, including a central processing unit (CPU), a network processor (NP), etc.; it may also be a digital signal processor (DSP), an application-specific integrated circuit (ASIC), an off-the-shelf programmable gate array (FPGA), or other programmable logic devices, discrete gate or transistor logic devices, or discrete hardware components. It can implement or execute the methods, steps, and logic block diagrams disclosed in the embodiments of this application. The general-purpose processor may be a microprocessor or any conventional processor. The steps of the methods disclosed in the embodiments of this application can be directly embodied in the execution of a hardware decoding processor, or executed by a combination of hardware and software modules in the decoding processor. The software modules may reside in random access memory, flash memory, read-only memory, programmable read-only memory, electrically erasable programmable memory, registers, or other mature storage media in the art. The storage medium is located in memory 601. Processor 600 reads the information in memory 601 and, in conjunction with its hardware, completes the steps of the above method.

[0093] The computer equipment provided in this application embodiment and the control method of the engine exhaust pipe aftertreatment system provided in this application embodiment are based on the same inventive concept and have the same beneficial effects as the methods they adopt, operate or implement.

[0094] This application also provides a computer-readable storage medium corresponding to the control method for the aftertreatment system of the engine exhaust pipe provided in the foregoing embodiments. Please refer to [reference needed]. Figure 7 The computer-readable storage medium shown is an optical disc 30, on which a computer program (i.e., a program product) is stored. When the computer program is run by a processor, it executes the control method of the aftertreatment system of the engine exhaust pipe provided in any of the foregoing embodiments.

[0095] It should be noted that examples of the computer-readable storage medium may also include, but are not limited to, phase-change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other optical and magnetic storage media, which will not be elaborated here.

[0096] The computer-readable storage medium provided in the above embodiments of this application and the control method of the engine exhaust pipe aftertreatment system provided in the embodiments of this application are based on the same inventive concept and have the same beneficial effects as the methods adopted, run or implemented by the application programs stored therein.

[0097] It should be noted that: Numerous specific details are set forth in the specification provided herein. However, it will be understood that embodiments of this application may be practiced without these specific details. In some instances, well-known structures and techniques have not been shown in detail so as not to obscure the understanding of this specification.

[0098] Similarly, it should be understood that, for the sake of brevity and to aid in understanding one or more of the various inventive aspects, in the above description of exemplary embodiments of this application, various features of this application are sometimes grouped together in a single embodiment, figure, or description thereof. However, this disclosure should not be construed as reflecting a schematic diagram in which the claimed application requires more features than expressly recited in each claim. Rather, as reflected in the following claims, inventive aspects lie in fewer than all features of a single foregoing disclosed embodiment. Therefore, the claims following the detailed description are hereby expressly incorporated into that detailed description, wherein each claim itself is a separate embodiment of this application.

[0099] Furthermore, those skilled in the art will understand that although some embodiments described herein include certain features but not others included in other embodiments, combinations of features from different embodiments are intended to be within the scope of this application and form different embodiments. For example, in the following claims, any of the claimed embodiments can be used in any combination.

[0100] The above description is merely a preferred embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. An aftertreatment system for an engine exhaust pipe, characterized in that, The aftertreatment system includes a first branch and a second branch arranged in parallel, and the input ends of the first branch and the second branch are used to connect to the engine exhaust pipe. The first branch includes a first nitrogen oxide purification module (101). The second branch is connected in series with the first switch module (102) and the pollutant pre-purification module (103) along the exhaust flow direction. The output terminals of the first branch and the second branch are connected in series with a particulate matter collection module (104) and a second nitrogen oxide purification module (105).

2. The aftertreatment system for the engine exhaust pipe according to claim 1, characterized in that, For any one of the first nitrogen oxide purification module (101) and the second nitrogen oxide purification module (105), the nitrogen oxide purification module includes a selective catalytic reducer and an ammonia purifier connected in series. The selective catalytic reduction device is used to purify nitrogen oxides in exhaust gas; The ammonia purifier is used to purify the ammonia generated by the selective catalytic reduction unit during the purification of nitrogen oxides.

3. The aftertreatment system for the engine exhaust pipe according to claim 1 or 2, characterized in that, The first branch also includes a first urea injection device and a first mixer arranged sequentially along the exhaust flow direction at the input end of the first nitrogen oxide purification module (101); a second urea injection device and a second mixer are arranged between the particulate matter collection module (104) and the second nitrogen oxide purification module (105).

4. The aftertreatment system for the engine exhaust pipe according to claim 1 or 2, characterized in that, A temperature measuring module is provided between the particulate matter collection module (104) and the second nitrogen oxide purification module (105).

5. The aftertreatment system for the engine exhaust pipe according to claim 3, characterized in that, The first branch also includes a second switch module disposed at the input end of the first urea injection device.

6. A control method for an aftertreatment system of an engine exhaust pipe, characterized in that, The control method is applied to the aftertreatment system of the engine exhaust pipe according to any one of claims 1 to 4; the control method includes: Obtain the engine's current operating mode; If the current operating mode is cold start mode, then control the first switch module (102) to turn off; If the current working mode is not the cold start mode, then determine whether the input temperature of the second nitrogen oxide purification module (105) is less than the preset temperature threshold. If the input temperature is less than the preset temperature threshold, the first switch module (102) is controlled to turn on, and the valve opening of the first switch module (102) is adjusted according to the input temperature. If the temperature at the input terminal is greater than or equal to the preset temperature threshold, then the first switch module (102) is controlled to be fully open.

7. A control method for an aftertreatment system of an engine exhaust pipe, characterized in that, The control method is applied to the aftertreatment system of the engine exhaust pipe according to claim 5; the control method includes: Obtain the engine's current operating mode; Determine whether the current working mode is active regeneration mode; the active regeneration mode refers to the working process in which the engine management system actively intervenes to restore the particulate filtration capacity when the amount of carbon soot accumulated in the particulate trap reaches a preset threshold. If the current working mode is the active regeneration mode, then control the first switch module (102) to be fully open and control the second switch module to be closed; If the current working mode is not the active regeneration mode, then determine whether the current working mode is the cold start mode; If the current working mode is the cold start mode, then control the first switch module (102) to be turned off and control the second switch module to be fully turned on; If the current working mode is not the cold start mode, the first switch module (102) and the second switch module are turned on at the same time, and the valve opening of the first switch module (102) and the second switch module is controlled according to the input temperature of the second nitrogen oxide purification module (105) and the carbon load of the particulate matter collection module (104).

8. The method according to claim 7, characterized in that, The valve openings of the first switching module (102) and the second switching module are controlled based on the input temperature of the second nitrogen oxide purification module (105) and the carbon load of the particulate matter collection module (104), including: If the input temperature of the second nitrogen oxide purification module (105) is less than the preset temperature threshold, the valve opening of the first switch module (102) is adjusted according to the input temperature, and the second switch module is fully opened. If the input temperature of the second nitrogen oxide purification module (105) is greater than or equal to the preset temperature threshold, then it is determined whether the carbon load of the particulate matter collection module (104) is greater than the preset carbon load. If the carbon load is greater than the preset carbon load, the first switch module (102) is fully opened, and the valve opening of the second switch module is reduced. If the carbon load is less than or equal to the preset carbon load, then the first switch module (102) and the second switch module are fully turned on.

9. A computer device, characterized in that, include: A memory and a processor are communicatively connected, the memory storing computer instructions, and the processor executing the computer instructions to perform the control method of the engine exhaust pipe aftertreatment system according to any one of claims 6 to 8.

10. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores computer instructions for causing the computer to execute the control method of the aftertreatment system of the engine exhaust pipe according to any one of claims 6 to 8.

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