Engine coupled aftertreatment device and control method thereof

Abstract

The application relates to an engine-coupled post-processing device and a control method thereof, the post-processing device comprising an oxidation catalyst DOC and a catalytic diesel particulate filter CDPF coupled in series, a flow-through oxidation catalyst DOC being installed upstream of a wall-flow catalytic diesel particulate filter CDPF, both being fixed in a same heat-resistant shell, and a hydrocarbon nozzle being arranged at the front end of the oxidation catalyst DOC. A specific temperature-control regeneration target is given according to a regeneration target strategy, a temperature-control process is realized by a DOC temperature-control strategy, and the two strategies are combined to construct an overall temperature-control regeneration strategy, so that the effectiveness and stability of the regeneration control strategy are ensured.

Description

Technical Field

[0001] This invention relates to the field of engine aftertreatment technology, and in particular to an engine-coupled aftertreatment device and its control method. Background Technology

[0002] Oxidation catalysts (DOC, diesel oxidation catalysts) are generally constructed by coating a cordierite support with a noble metal catalyst, the main components of which are platinum (Pt) and palladium (Pd). Their structure is as follows: Figure 1 As shown, pollutants emitted in the airflow, as they pass through the channel formed by the cordierite support, enter the surface of the catalyst (platinum and palladium) through processes such as diffusion and adsorption, and undergo catalytic reactions at the active sites. The catalytic process consumes oxygen in the exhaust gas, ultimately producing NO. x PM and carbon dioxide are released back into the exhaust gas and flow out of the DOC (dioxide) outlet.

[0003] A catalyzed diesel particulate filter (CDPF) works by coating a diesel particulate filter (DPF) with a catalyst. The working principle of a DPF is shown in the diagram below. Figure 2 As shown, with improvements in catalyst technology, the inlet gas temperature for active DPF regeneration, which previously required maintaining nearly 600°C, can now be achieved with a CDPF inlet gas temperature of around 450°C. The addition of a catalyst reduces the regeneration cycle, improves fuel economy, and enhances regeneration safety.

[0004] Due to the limited installation location and space for aftertreatment devices in passenger cars, different shapes of aftertreatment devices need to be designed to meet space requirements, which increases costs and the economic burden on car owners.

[0005] Regardless of whether a catalyst is included, DPFs (Distilled Power Factories) pose a safety hazard: during regeneration, a sudden drop in exhaust gas flow can cause excessively high DPF support wall temperatures, leading to support damage or even sintering. Therefore, the selection of temperature control targets and the safety performance of temperature control strategies during sudden exhaust gas flow drops are crucial. Commercial CDPFs are coated with catalysts primarily composed of platinum and palladium, consistent with the catalysts coated with DOCs. Therefore, during active regeneration, an unreacted hydrocarbon from the DOC flows into the CDPF and reacts on the CDPF wall, raising the CDPF wall temperature to a level higher than the CDPF inlet gas temperature. This temperature difference effect can increase the carbon particle regeneration reaction rate and shorten the regeneration time, but it also presents greater safety risks.

[0006] Patent application 201822106323.5 discloses a DPF diesel engine particulate matter treatment system. This system uses a periodically reversing pipeline connecting DOC+CDPF+DOC, and is controlled by a control system to form a periodically reversible treatment system. The system utilizes the chemical reactions caused by organic pollutants in the exhaust gas or by supplementing with trace amounts of atomized fuel oil. The respective filters and honeycomb ceramic carriers within the system undergo self-sustaining heat storage and release processes, and the reverse flow removes chemical reaction residues and non-flammable inorganic salts and other ash accumulated on the wall-flow channels. However, the aftertreatment system in this patented solution occupies a large volume, making it unsuitable for installation on many vehicles.

[0007] Patent application 202110957644.X discloses a self-cleaning exhaust gas purification system for heavy-duty diesel special vehicles. The system includes a DOC+CDPF exhaust gas purification device, an air duct, an electrostatic particulate filter, and an online monitoring and control system. The air duct connects to the electrostatic particulate filter, altering the gas flow direction as it enters the DOC+CDPF exhaust gas purification device along the electrostatic particulate filter. It utilizes the heat energy of the exhaust gas itself to heat and insulate the DOC and CDPF carriers, reducing heat loss and temperature fluctuations caused by operating conditions, thereby extending the regeneration temperature time window and promoting continuous passive regeneration of the DOC+CDPF system. However, this patent still requires an external electrostatic particulate filter, which remains a problem in terms of installation volume. Summary of the Invention

[0008] The purpose of this invention is to overcome the defects of the prior art and provide an engine-coupled aftertreatment device and its control method.

[0009] The objective of this invention can be achieved through the following technical solutions:

[0010] As a first aspect of the present invention, an engine-coupled aftertreatment device is provided, the aftertreatment device comprising an oxidation catalyst DOC and a catalytic diesel particulate filter CDPF coupled in series, wherein the flow-through oxidation catalyst DOC is installed upstream of the wall-flow catalytic diesel particulate filter CDPF, and both are fixed in the same heat-resistant housing, and a hydrocarbon nozzle is provided at the front end of the oxidation catalyst DOC.

[0011] As a second aspect of the present invention, a control method for the engine-coupled aftertreatment device as described above is provided, the method specifically comprising the following steps:

[0012] The series-coupled oxidation catalyst (DOC) and catalytic converter (CDPF) for diesel engines were calibrated separately. Based on the calibration experiments of DOC and CDPF, the regeneration strategy of CDPF was obtained, including:

[0013] Temperature control requires ensuring that the incoming flow temperature is greater than the temperature threshold determined by calibration experiments;

[0014] Maintain the oxygen concentration at a multiple greater than the injected hydrocarbon concentration;

[0015] The target outlet temperature of DOC is within the operating range of the injector's injection volume. If the target outlet temperature cannot be reached even after the injector's operating limit has been reached, switch to a smaller flow rate or a higher inflow temperature for temperature-controlled regeneration.

[0016] Estimate the carbon loading of CDPF, determine the start / stop of regeneration based on the carbon loading, and switch the capture and regeneration phases of CDPF.

[0017] Furthermore, the step of calibrating the thermal properties of the DOC specifically includes:

[0018] Thermal characteristics of DOC were tested by injecting diesel fuel with different injection rates, and the temperature rise curves were dynamically recorded to study the DOC temperature model based on hydrocarbon injection.

[0019] The parameters of the flow-reaction coupling model of DOC are obtained through experiments, including physical parameters given by the actual experimental system and temperature characteristic curves obtained by actual DOC temperature rise characteristic experiments. The temperature characteristic curves are obtained by parameter identification and calibration based on the experimental curves.

[0020] The injector is controlled by PWM pulse width control, which adjusts the injection volume by keeping the injection pulse width constant and only changing the injection frequency.

[0021] Furthermore, when conducting thermal characteristic tests on the DOC, a set mass flow rate threshold is used. For test conditions where the mass flow rate is greater than or equal to the set mass flow rate threshold, a larger injection frequency is used for comparative verification. And when the outlet temperature of the injected DOC exceeds the set test temperature threshold, subsequent injections of a larger volume are stopped.

[0022] Furthermore, the specific steps for calibrating the CDPF include:

[0023] Multiple temperature sensors are arranged at the inlet, inside and outlet of the CDPF, and a differential pressure sensor is set up to measure the pressure difference between the inlet and outlet of the CDPF. Multiple armored thermocouples that are tightly attached to the CDPF carrier are inserted into the CDPF in sequence, and the average wall temperature inside the CDPF is obtained by averaging and weighting the carrier temperature measured by each thermocouple.

[0024] The engine speed was changed to conduct a loading experiment. Loading was stopped when the carbon load reached the set experimental stop threshold, and experimental data was obtained.

[0025] The regeneration test was conducted using an open-loop injection mode, i.e., a fixed steady-state condition was selected, and the DOC outlet temperature was increased by a given injection rate to ensure that the DOC outlet temperature reached and exceeded the required carbon particle ignition temperature. The CDPF inlet and outlet pressure difference curves and the temperature measurement curves of each CDPF point were recorded during regeneration. The CDPF model was calibrated and verified. The CDPF model includes a flow pressure difference-related trapping model and a temperature and chemical reaction model related to regeneration.

[0026] Furthermore, the CDPF regeneration strategy also includes:

[0027] The greater the engine torque, the lower the hydrocarbon injection volume during temperature-controlled regeneration; the lower the engine torque, the higher the hydrocarbon injection volume during temperature-controlled regeneration.

[0028] Furthermore, the CDPF regeneration strategy also includes increasing the injection volume of hydrocarbon injectors at higher engine speeds.

[0029] Furthermore, the CDPF regeneration strategy also includes:

[0030] Calculate the overall reaction efficiency of DOC under the current operating condition. If the overall reaction efficiency under the current operating condition is lower than the set reaction efficiency threshold, then switch the operating condition accordingly based on the factors affecting the reaction efficiency.

[0031] Under the condition that the overall reaction efficiency meets the threshold, obtain the current mass flow rate of the diesel engine, the inlet temperature and oxygen concentration of the exhaust gas system, and calculate the maximum outlet temperature of DOC.

[0032] If the maximum outlet temperature of the DOC can be higher than the set temperature value, the regeneration condition selection process is complete; if it cannot be reached, the condition is switched according to the unmet factors, selecting a smaller mass flow rate, a higher inlet oxygen concentration, or a higher inlet temperature.

[0033] Furthermore, the specific steps for estimating the carbon loading of CDPF include:

[0034] The cumulative carbon integral method is adopted to continuously and periodically accumulate carbon particles according to the carbon particle concentration under various working conditions until the carbon load exceeds the set judgment limit, and then regeneration is initiated.

[0035] Calculate the real-time regeneration rate of carbon particles, and stop regeneration when the carbon loading reaches the set lower limit;

[0036] After regeneration, a stable operating condition is selected, and the remaining carbon load is calculated by the pressure difference between the inlet and outlet of the CDPF using the Darcy flow resistance method; the carbon load in the cumulative carbon integral method is corrected, and the ash content and combustible carbon load are distinguished.

[0037] Furthermore, if the carbon load reaches the upper limit of the ash removal carbon load after multiple regenerations, an ash removal and maintenance instruction will be given.

[0038] Compared with the prior art, the present invention has the following beneficial effects:

[0039] 1) This invention provides a regeneration control method for a DOC+CDPF coupled device. This method employs hydrocarbon injection-based technology, where catalytic oxidation generates heat on the DOC catalyst surface through diffusion mass transfer, and the heat is then transferred back to the tail gas via convection to achieve a temperature rise. Based on this principle, a feedforward control algorithm is designed, and a stable boundary trajectory (SBL) combined with an intelligent weighted self-optimizing PI feedback control algorithm is designed. A specific temperature control regeneration target is given according to the regeneration target strategy, and the temperature control process is achieved by the DOC temperature control strategy. The two strategies are combined to construct an overall temperature control regeneration strategy, ensuring the effectiveness and stability of the regeneration control strategy. Attached Figure Description

[0040] Figure 1 This is a schematic diagram illustrating the principle of DOC.

[0041] Figure 2 This is a schematic diagram of the DPF structure;

[0042] Figure 3 This is a schematic diagram of the series-coupled DOC+CDPF structure of the present invention;

[0043] Figure 4 This is a structural diagram of a temperature-controlled regeneration system;

[0044] Figure 5 This is the regeneration logic diagram. Detailed Implementation

[0045] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0046] Example 1

[0047] This invention relates to an engine-coupled aftertreatment device and its control method, which uses a series coupling of DOC and CDPF, and its structure is as follows: Figure 3 As shown, the flow-through DOC is installed upstream of the wall-flow CDPF, and both are fixed within the same heat-resistant stainless steel housing. A gasket surrounds the carrier, providing shock absorption and sealing. A temperature-controlled regeneration platform was constructed using various sensors, thermocouples, and hydrocarbon injection technology to test and calibrate the series-coupled DOC+CDPF, and a temperature-controlled regeneration strategy was developed.

[0048] The DOC support is cordierite, and the catalyst is coated with precious metals platinum and palladium in a platinum-palladium ratio of 5:1. The catalyst coating amount is 0.5 g / L.

[0049] The CDPF also uses cordierite as a support, which is a honeycomb ceramic support with a mesh size of 400 cpsi, a thickness of 12 mil, and a porosity of 50-60%. The CDPF is also coated with a noble metal catalyst with a platinum to palladium ratio of 5:1, with a coating amount of 5 g / L.

[0050] To enable communication for the temperature-controlled regeneration platform, the injection controller needs to be chip-controlled and communicate with the host computer in real time via the CAN bus protocol. The host computer uses DataView software to send commands and responses to data packets on the CAN bus.

[0051] The overall experimental structure is as follows: The hydrocarbon nozzle is installed at the front end of the DOC (Diesel Exhaust Gas Charge). The exhaust temperature sensor and mass flow sensor are located after the diesel engine exhaust turbocharger. The upstream temperature sensor of the DOC is located after the hydrocarbon nozzle, near the DOC inlet. The downstream temperature sensor of the DOC is located at the DOC outlet. The temperature sensors are 1mm diameter high-temperature resistant K-type armored thermocouples. The aftertreatment system is a DOC+CDPF integrated encapsulated structure. The regeneration platform structure diagram is shown below. Figure 4 As shown.

[0052] To achieve temperature control, the thermal characteristics of the DOC must first be calibrated. The steps are as follows:

[0053] The thermal characteristic test of DOC involved injecting diesel fuel at different injection rates. The test conditions are shown in Table 1. Temperature rise curves were dynamically recorded to study the DOC temperature model based on hydrocarbon injection. The injectors were controlled by PWM pulse width modulation. To ensure the injection rate was as linear as possible, the injection pulse width was kept constant while only the injection frequency was changed. The injection rate corresponding to each injection frequency is shown in Table 2. During the test, for conditions 1-6 (mass flow rate less than or equal to 300 kg / h), five injection frequencies of 40Hz, 60Hz, 80Hz, 100Hz, and 120Hz were used for comparison and verification. When the DOC outlet temperature was likely to exceed 600℃, subsequent injections of higher volumes were stopped to prevent damage from excessively high DOC temperatures.

[0054] Table 1 Test Conditions

[0055]

[0056] For operating conditions 7-12, with a mass flow rate greater than or equal to 400 kg / h, a larger injection rate is required to achieve a significant temperature rise. Therefore, five injection frequencies of 40 Hz, 80 Hz, 120 Hz, 160 Hz, and 200 Hz were used for comparative verification. When the temperature generated by the injection becomes too high, the aforementioned cutoff method is also used to prevent high-temperature damage to the DOC. The injection rate table is shown in Table 2.

[0057] Table 2 Injection Volume Table

[0058] Injection frequency Hz Jet pulse width μs Injection rate g / s 40 2000 0.176 60 2000 0.265 80 2000 0.363 100 2000 0.466 120 2000 0.518 140 2000 0.613 160 2000 0.718 180 2000 0.829 200 2000 0.945

[0059] The parameters of the flow-reaction coupling model for DOC consist of two parts. One part is the physical parameters given by the actual experimental system, such as incoming mass flow rate, incoming temperature, incoming oxygen concentration, and DOC structural parameters. The other part is the temperature characteristic curve obtained from actual DOC temperature rise characteristic experiments. Parameters are identified and calibrated based on the experimental curves. The parameter identification toolbox in Matlab is used, and the method employed is automatic optimization using nonlinear least squares.

[0060] Experiments revealed that increasing the injection volume initially increased the catalytic oxidation efficiency of hydrocarbons, followed by a decrease. Increasing the mass flow rate resulted in an initial decrease followed by an increase in catalytic oxidation efficiency. As the inlet temperature increased from near the DOC ignition temperature, the efficiency rapidly increased from a very low point until complete ignition. Further temperature increases resulted in almost no change in reaction efficiency. Initially, decreasing the oxygen concentration from 21% to 0% had no effect on reaction efficiency; only after reaching a lower value did the catalytic oxidation efficiency significantly drop to zero, while the evaporation and pyrolysis process continued depending on the inlet conditions. For this DOC, a good catalytic oxidation effect can be achieved as long as the inlet oxygen concentration is greater than or equal to 34 times the hydrocarbon concentration. The study of factors affecting reaction efficiency can provide a design basis for selecting regeneration conditions in subsequent temperature-controlled regeneration strategies.

[0061] After calibrating the DOC model, the CDPF needs to be calibrated. The steps are as follows:

[0062] Temperature sensors T2-T6 are associated with the CDPF, measuring temperatures at the CDPF inlet (DOC outlet), upper CDPF section, middle CDPF section, lower CDPF section, and CDPF outlet. The inlet measuring point is located on the windward side of the CDPF, thus measuring the CDPF inlet temperature value in the model. Three 1mm diameter K-type armored thermocouples are sequentially inserted inside the CDPF, tightly fitted to the CDPF carrier, and the temperatures of the CDPF carrier in the upper, middle, and lower sections are measured, denoted as Tw1, Tw2, and Tw3 respectively. The average weighted average of these three measurements reflects the average wall temperature Tw inside the CDPF. The system outlet temperature is measured at the CDPF outlet temperature measuring point. Of the five measuring points, for typical commercial exhaust aftertreatment systems, the CDPF inlet and outlet temperatures are available; however, the CDPF wall temperature is not available. This measurement is only used to verify the wall temperature model; the wall temperature in subsequent control strategies needs to be obtained using the wall temperature calculation method.

[0063] Furthermore, the CDPF differential pressure sensor has two pins connected to the CDPF inlet and outlet respectively to measure the CDPF inlet-outlet pressure difference.

[0064] The engine speed was changed, and a loading experiment was conducted. The loading was stopped when the carbon load was 8 g / L, and the experimental data were obtained.

[0065] The regeneration test adopted an open-loop injection mode, that is, a fixed steady-state condition was selected, and the DOC outlet temperature was raised to exceed the ignition temperature of carbon particles by a given injection amount. Then, the pressure difference change curve and the temperature measurement curve of each CDPF point were recorded during regeneration and compared with the model for verification.

[0066] In practical applications, CDPF models can be divided into two categories: one is the trapping model related to the flow pressure difference, and the other is the temperature and chemical reaction model related to regeneration. These correspond to the trapping and regeneration stages of CDPF during normal operation, respectively. Therefore, calibration and verification of these two models need to be performed separately. The tool used is still the parameter identification toolbox in Matlab, and the method employed is automatic optimization using nonlinear least squares.

[0067] Experiments revealed that under steady-state conditions, a higher CDPF inlet temperature resulted in a lower oxygen concentration flowing into the CDPF, but also a higher wall temperature. The former slowed down the regeneration rate, while the latter accelerated it, with the latter having a stronger accelerating effect. To achieve faster regeneration under the same conditions, the CDPF inlet temperature needs to be as high as possible. When controlling the CDPF inlet at the same target temperature under different mass flow rates, the larger mass flow rate resulted in a more significant difference between the wall and inlet temperatures. For this engine, controlling the target temperature at a larger mass flow rate resulted in a higher oxygen concentration flowing into the CDPF, accelerating the regeneration process and ultimately significantly shortening the regeneration time at larger mass flow rates. When controlling the CDPF inlet at the same target temperature under different incoming flow temperatures, the larger incoming flow temperature resulted in less residual hydrocarbons flowing into the CDPF, leading to a smaller difference between the CDPF wall and inlet temperatures. Simultaneously, a larger incoming flow temperature resulted in a lower oxygen concentration flowing into the exhaust aftertreatment system, thus reducing the residual oxygen concentration in the DOC reaction and decreasing the regeneration rate.

[0068] Based on the above conclusions, we can derive three CDPF objective design principles:

[0069] The higher the mass flow rate, the higher the residual oxygen concentration and the significantly higher the residual hydrocarbon content. Therefore, the target temperature can be appropriately selected to keep the wall temperature from becoming too high.

[0070] The higher the incoming flow temperature, the lower the residual hydrocarbon content and residual oxygen concentration will be. Therefore, the target temperature can be appropriately selected to increase the wall temperature and reduce the regeneration time.

[0071] Throughout the CDPF's entire operating cycle, the switching between the capture and regeneration phases is achieved through regeneration start / stop determination. The core basis for regeneration start / stop determination is generally the carbon loading of the CDPF. When the carbon loading captured within the CDPF exceeds the maximum allowable carbon loading, regeneration is required. During regeneration, the carbon loading continuously decreases, and once it falls below the set lower limit, regeneration is considered complete, and the system switches back to the capture cycle phase.

[0072] Carbon loading can be obtained using two methods. One is the Darcy flow resistance method, where carbon loading is calculated based on the current operating physical parameters and the measured pressure difference between the inlet and outlet of the CDPF. The other is the cumulative carbon integration method, which measures and calibrates the original emission carbon soot concentration under various operating conditions and external physical conditions to construct a carbon soot MAP.

[0073] Once the current carbon loading is determined, the start / stop of regeneration needs to be determined based on the carbon loading. When the calculated carbon loading value is greater than the set upper limit, such as 8 g / L, carbon loading regeneration is initiated. During the regeneration process, the carbon loading is dynamically calculated. When this value is less than the set lower limit, such as 0.4 g / L (the upper limit for 5% carbon loading), it indicates that regeneration is complete, and regeneration is stopped to re-enter the capture stage.

[0074] It is worth mentioning that the Darcy flow resistance method has a drawback: it has many input parameters, and the output carbon loading can vary greatly, leading to inaccurate results. The advantage of the cumulative carbon loading method is that the carbon loading is obtained by integrating the operating conditions, and fluctuations in the operating conditions do not cause significant jumps in the cumulative carbon loading value. Furthermore, the cumulative carbon loading method calculates the carbon loading regeneration rate based on the model, allowing for stable prediction of carbon loading changes during the regeneration process. However, the cumulative carbon loading method is susceptible to cumulative errors due to ash accumulation; therefore, this patent uses a combination of both methods. The design logic diagram is as follows: Figure 5 As shown.

[0075] like Figure 5 As shown, the system first employs a cumulative carbon integration method, continuously accumulating carbon particle concentrations under various operating conditions. When the carbon particle concentration exceeds a set upper limit, regeneration is initiated, and the real-time regeneration rate is calculated. Regeneration stops when the calculated result indicates that regeneration has reached a set lower limit. After regeneration, the system selects a relatively stable operating condition and uses the Darcy flow resistance method to calculate the remaining carbon load, correcting the carbon load in the cumulative carbon integration method and distinguishing between ash and combustible carbon load. If, after multiple regenerations, the carbon load reaches the upper limit for ash removal, it indicates that a significant amount of carbon particles remain unremoved after regeneration, resulting in excessive ash content, and a ash removal maintenance instruction is issued.

[0076] Based on previous calibration experiments of DOC and CDPF, the regeneration strategy of CDPF can be obtained as follows:

[0077] Temperature control requires ensuring that the incoming flow temperature is greater than 270°C to ensure that the system can completely evaporate, pyrolyze, and ignite.

[0078] Maintaining an oxygen concentration 34 times greater than the injected hydrocarbon concentration allows DOC to undergo catalytic oxidation with higher reaction efficiency.

[0079] The target outlet temperature of DOC needs to be within the operating range of the ejector's injection volume. If the ejector's operating limit has been reached and the target outlet temperature still cannot be achieved, it is necessary to consider switching to a lower flow rate or a higher inflow temperature for temperature-controlled regeneration.

[0080] The greater the engine torque, the lower the oxygen concentration, but the relatively higher the exhaust temperature. When the exhaust temperature is controlled, the amount of hydrocarbon injection required by the injector is lower.

[0081] The lower the engine torque, the higher the oxygen concentration and the relatively lower the exhaust temperature. When the exhaust temperature is controlled, the hydrocarbon injector needs a higher injection volume.

[0082] There is a direct correlation between engine speed and exhaust mass flow rate. At higher engine speeds, a significant increase in temperature requires higher injection demands from hydrocarbon injectors.

[0083] Calculate the overall DOC reaction efficiency under the current operating conditions. If the reaction efficiency is less than 0.5, it means that the operating conditions are not suitable for temperature control. It is necessary to analyze the factors affecting the reaction efficiency and switch to the appropriate operating conditions.

[0084] If the reaction efficiency meets the requirements, obtain the current mass flow rate of the diesel engine, the inlet temperature of the exhaust gas system, and the oxygen concentration, and use the formula to calculate the maximum outlet temperature of DOC.

[0085] If the maximum outlet temperature of the DOC can exceed 773K (500℃), it indicates that the operating condition meets the requirements of the regeneration operating condition selection strategy, and the regeneration operating condition selection process is complete. If it cannot be achieved, it means that the operating condition is not suitable for temperature-controlled regeneration, and the operating condition needs to be switched according to the unmet factors, selecting a smaller mass flow rate, a higher inlet oxygen concentration, or a higher inlet temperature.

[0086] Example 1

[0087] An engine-coupled aftertreatment device and its control method are as follows:

[0088] Use the DOC vector, with specific parameters shown in Table 3; use the CDPF vector, with specific parameters shown in Table 4.

[0089] Table 3 DOC Parameter Table

[0090] parameter numerical values Carrier diameter / mm 190 Carrier length / mm 76 carrier material Iolite catalyst Pt / Pd Platinum-Palladium Ratio 5：1 Number of holes 400cpsi

[0091] Table 4 CDPF Parameter Table

[0092] parameter numerical values Carrier diameter / mm 190 Carrier length / mm 127 carrier material silicon carbide catalyst Pt / Pd Platinum-Palladium Ratio 12:1 Number of holes 300cpsi Porosity 0.42 Wall thickness 10mil

[0093] Step 1: Install DOC and CDPF into the temperature-controlled regeneration platform described in the above embodiment.

[0094] Step 2: Calibrate the DOC according to the DOC calibration method described in the above embodiment.

[0095] Step 3: Calibrate the CDPF according to the CDPF calibration method described in the above embodiment.

[0096] Step 4: Based on the previous calibration experiments of DOC and CDPF, the regeneration strategy of CDPF is obtained:

[0097] Temperature control requires ensuring that the incoming flow temperature is greater than 280℃ to ensure that the system can completely evaporate, pyrolyze, and ignite.

[0098] Maintaining an oxygen concentration 27 times greater than the injected hydrocarbon concentration allows DOC to undergo catalytic oxidation with higher reaction efficiency.

[0099] The target outlet temperature of DOC needs to be within the operating range of the ejector's injection volume. If the ejector's operating limit has been reached and the target outlet temperature still cannot be achieved, it is necessary to consider switching to a lower flow rate or a higher inflow temperature for temperature-controlled regeneration.

[0100] The greater the engine torque, the lower the oxygen concentration, but the relatively higher the exhaust temperature. When the exhaust temperature is controlled, the amount of hydrocarbon injection required by the injector is lower.

[0101] The lower the engine torque, the higher the oxygen concentration and the relatively lower the exhaust temperature. When the exhaust temperature is controlled, the hydrocarbon injector needs a higher injection volume.

[0102] There is a direct correlation between engine speed and exhaust mass flow rate. At higher engine speeds, to achieve a significant increase in temperature, the injection requirements of hydrocarbon injectors need to be increased.

[0103] Calculate the overall DOC reaction efficiency under the current operating conditions. If the reaction efficiency is lower than 0.48, it indicates that the operating conditions are not suitable for temperature control. It is necessary to analyze the factors affecting the reaction efficiency and switch to the appropriate operating conditions.

[0104] If the reaction efficiency meets the requirements, obtain the current mass flow rate of the diesel engine, the inlet temperature of the exhaust gas system, and the oxygen concentration, and use the formula to calculate the maximum outlet temperature of DOC.

[0105] If the maximum outlet temperature of the DOC can exceed 750K (477℃), it indicates that the operating condition meets the requirements of the regeneration operating condition selection strategy, and the regeneration operating condition selection process is complete. If it cannot be achieved, it means that the operating condition is not suitable for temperature-controlled regeneration, and the operating condition needs to be switched according to the unmet factors, selecting a smaller mass flow rate, a higher inlet oxygen concentration, or a higher inlet temperature.

[0106] Step 5: Estimate the CDPF carbon loading according to the method described in the embodiment, determine the start / stop of regeneration based on the carbon loading, and switch the CDPF capture stage and regeneration stage.

[0107] The system employs a cumulative carbon integration method, continuously accumulating carbon particle concentrations under various operating conditions. When the carbon particle concentration exceeds a set upper limit, regeneration is initiated, and the real-time regeneration rate is calculated. Regeneration stops when the calculated result indicates that the concentration has been reduced to a set lower limit. After regeneration, the system selects a relatively stable operating condition and uses the Darcy flow resistance method to calculate the remaining carbon load, correcting the carbon load in the cumulative carbon integration method and distinguishing between ash and combustible carbon load. If, after multiple regenerations, the carbon load reaches the upper limit for ash removal, it indicates that a significant amount of carbon particles remain unremoved after regeneration, resulting in excessive ash content, and a ash removal maintenance instruction is issued.

[0108] This invention proposes an engine-coupled aftertreatment device and its control method. It employs hydrocarbon injection-based technology, where heat is generated on the surface of the DOC catalyst through diffusion mass transfer and catalytic oxidation to heat the DOC. This heat is then transferred back to the exhaust gas via convection, achieving a temperature rise. Based on this principle, a feedforward control algorithm is designed, combining a stable boundary trajectory (SBL) with an intelligent weighted self-optimizing PI feedback control algorithm. A specific temperature control regeneration target is given based on the regeneration objective strategy, and the temperature control process is achieved by a DOC temperature control strategy. The two strategies are combined to construct an overall temperature control regeneration strategy, ensuring the effectiveness and stability of the regeneration control strategy.

[0109] Finally, it should be noted that the above embodiments are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A control method for an engine-coupled aftertreatment device, characterized in that, The aftertreatment device includes an oxidation catalyst DOC and a catalytic diesel particulate filter CDPF coupled in series. The flow-through oxidation catalyst DOC is installed upstream of the wall-flow catalytic diesel particulate filter CDPF. Both are fixed in the same heat-resistant housing. A hydrocarbon nozzle is provided at the front end of the oxidation catalyst DOC. The specific steps of the control method include: The series-coupled oxidation catalyst DOC and the catalytic diesel particulate filter CDPF were calibrated respectively. The specific steps for calibrating the thermal characteristics of the oxidation catalyst DOC include: Thermal characteristics tests of DOC were conducted using diesel fuel injection at different injection rates, and the temperature rise curves were dynamically recorded to form a DOC temperature model based on hydrocarbon injection. The parameters of the flow-reaction coupling model of DOC are obtained through experiments, including physical parameters given by the actual experimental system and temperature characteristic curves obtained by actual DOC temperature rise characteristic experiments. The temperature characteristic curves are obtained by parameter identification and calibration based on the experimental curves. The fuel injector is opened and closed by PWM pulse width control, and the injection quantity is adjusted by keeping the injection pulse width constant and only changing the injection frequency. The specific steps for calibrating the catalytic converter particulate filter (CDPF) for the diesel engine include: Multiple temperature sensors are arranged at the inlet, inside and outlet of the CDPF, and a differential pressure sensor is set up to measure the pressure difference between the inlet and outlet of the CDPF. Multiple armored thermocouples that are tightly attached to the CDPF carrier are inserted into the CDPF in sequence, and the average wall temperature inside the CDPF is obtained by averaging and weighting the carrier temperature measured by each thermocouple. The engine speed was changed to conduct a loading experiment. Loading was stopped when the carbon load reached the set experimental stop threshold, and experimental data was obtained. The regeneration test was conducted using an open-loop injection mode, i.e., a fixed steady-state condition was selected, and the DOC outlet temperature was increased by a given injection rate until it reached and exceeded the ignition temperature of the carbon particles. The pressure difference curves at the inlet and outlet of the CDPF and the temperature measurement curves at various points of the CDPF were recorded during regeneration. The CDPF model was calibrated and verified. The CDPF model includes a trapping model related to the flow pressure difference and a temperature and chemical reaction model related to regeneration. The regeneration strategy for CDPF was obtained based on calibration experiments of DOC and CDPF, including: Temperature control requires that the incoming flow temperature be greater than the temperature threshold determined by calibration experiments. Maintain the oxygen concentration at a multiple greater than the injected hydrocarbon concentration; If the target outlet temperature of DOC cannot be reached even after reaching the injector's operating limit within the injector's injection volume operating range, then switch to a smaller flow rate condition or a higher incoming flow temperature condition for temperature-controlled regeneration. Estimate the carbon loading of CDPF, determine the start / stop of regeneration based on the carbon loading, and switch the capture and regeneration phases of CDPF.

2. The control method for an engine-coupled aftertreatment device according to claim 1, characterized in that, When conducting thermal characteristic tests on the DOC, a set mass flow rate threshold is used. For test conditions where the mass flow rate is greater than or equal to the set mass flow rate threshold, a larger injection frequency is used for comparative verification. Furthermore, when the outlet temperature of the injected DOC exceeds the set test temperature threshold, subsequent injections of larger quantities are stopped.

3. The control method for an engine-coupled aftertreatment device according to claim 1, characterized in that, The CDPF regeneration strategy also includes: The greater the engine torque, the lower the hydrocarbon injection volume during temperature-controlled regeneration; the lower the engine torque, the higher the hydrocarbon injection volume during temperature-controlled regeneration.

4. The control method for an engine-coupled aftertreatment device according to claim 1, characterized in that, The CDPF regeneration strategy also includes increasing the injection volume of hydrocarbon injectors at higher engine speeds.

5. The control method for an engine-coupled aftertreatment device according to claim 1, characterized in that, The CDPF regeneration strategy also includes: Calculate the overall reaction efficiency of DOC under the current operating condition. If the overall reaction efficiency under the current operating condition is lower than the set reaction efficiency threshold, then switch the operating condition accordingly based on the factors affecting the reaction efficiency. Under the condition that the overall reaction efficiency meets the threshold, obtain the current mass flow rate of the diesel engine, the inlet temperature and oxygen concentration of the exhaust gas system, and calculate the maximum outlet temperature of DOC. If the maximum outlet temperature of the DOC can be higher than the set temperature value, the regeneration condition selection process is complete; if it cannot be reached, the condition is switched according to the unmet factors, selecting a smaller mass flow rate, a higher inlet oxygen concentration, or a higher inlet temperature.

6. The control method for an engine-coupled aftertreatment device according to claim 1, characterized in that, The specific steps for estimating CDPF carbon loading include: The cumulative carbon integral method is adopted to continuously and periodically accumulate carbon particles according to the carbon particle concentration under various working conditions until the carbon load exceeds the set judgment limit, and then regeneration is initiated. Calculate the real-time regeneration rate of carbon particles, and stop regeneration when the carbon loading reaches the set lower limit; After regeneration, a stable operating condition is selected, and the remaining carbon load is calculated by the pressure difference between the inlet and outlet of the CDPF using the Darcy flow resistance method; the carbon load in the cumulative carbon integral method is corrected, and the ash content and combustible carbon load are distinguished.

7. The control method for an engine-coupled aftertreatment device according to claim 6, characterized in that, If the carbon load reaches the upper limit of the ash cleaning carbon load after multiple regenerations, an ash cleaning and maintenance instruction will be given.

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