Diesel engine exhaust back pressure control method, diesel engine aftertreatment device and vehicle

Abstract

The present invention relates to the field of vehicle technology, and specifically discloses a diesel engine exhaust back pressure control method, a diesel engine aftertreatment device and a vehicle. The diesel engine exhaust back pressure control method comprises S10: reading detection data of the engine aftertreatment device, S20: determining an air pump opening and / or a combustion timing correction value according to the detection data of the engine aftertreatment device; S30: judging whether the air pump opening value exceeds the air pump opening change rate, and / or whether the gas timing value exceeds the gas timing change rate, if yes, executing S40, otherwise executing S50 air pump opening value and / or combustion timing correction value; S40: adjusting the air pump opening value to meet the air pump opening change rate, and / or adjusting the gas timing value to meet the gas timing change rate, executing S50; the method flexibly and actively realizes the regulation of the exhaust back pressure after the turbine, adjusts the performance of the engine, and adjusts the gas temperature in the aftertreatment assembly at the same time.

Description

Technical Field

[0001] The present invention relates to the field of vehicle technology, and in particular to a diesel engine exhaust back pressure control method, a diesel engine after-treatment device, and a vehicle. Background Art

[0002] As the requirements for automobile environmental protection and energy conservation become increasingly stringent, low fuel consumption and low emissions have put forward higher requirements for after-treatment. As after-treatment components gradually become more sophisticated and complex, the exhaust back pressure before after-treatment gradually increases, and at the same time, higher requirements are put forward for exhaust temperature control. The after-treatment temperature needs to be increased as soon as possible to increase the reaction efficiency.

[0003] Actual engine testing has revealed that exhaust backpressure significantly impacts engine power, economy, and bare-metal emissions. Existing technologies primarily control exhaust backpressure through structural optimization, such as optimizing the aftertreatment structure to reduce pressure drop and optimizing the exhaust pipe structure. Backpressure control is limited to increasing low-speed exhaust gas temperatures via the exhaust backpressure valve. This approach prevents flexible adjustment of exhaust backpressure across various operating conditions, particularly at high speeds and high loads, resulting in significant backpressure degradation, significantly impacting engine performance.

[0004] Therefore, there is an urgent need for a diesel engine exhaust back pressure control method to solve the above problems. Summary of the Invention

[0005] The purpose of the present invention is to provide a diesel engine exhaust back pressure control method, a diesel engine after-treatment device and a vehicle, so as to solve the problem that the control of exhaust back pressure in related technologies is mainly achieved through structural optimization, or is used to increase the low-speed exhaust temperature by an exhaust back pressure valve, and the exhaust back pressure under various working conditions cannot be flexibly adjusted, especially at high speed and high load, the back pressure is relatively large, which has a significant impact on engine performance.

[0006] In one aspect, the present invention provides a method for controlling exhaust back pressure of a diesel engine, which is implemented by a diesel engine aftertreatment device, wherein the diesel engine aftertreatment device includes an engine, a turbine, an aftertreatment assembly, and an air pump, wherein the exhaust port of the engine is connected to the air inlet of the turbine, the air outlet of the turbine is connected to the air inlet of the aftertreatment assembly, and the air outlet of the aftertreatment assembly is connected to the air inlet of the air pump;

[0007] The diesel engine exhaust back pressure control method comprises:

[0008] S10: Reading the detection data of the engine after-treatment device, including the gas temperature t1 in the after-treatment assembly, the engine cycle injection amount t2 and the smoke limit air-fuel ratio;

[0009] S20: determining the opening degree of the air pump and / or the combustion timing correction value according to the detection data of the engine after-treatment device;

[0010] S30: Determine whether the change rate of the gas pump opening value exceeds the set change rate of the gas pump opening, and / or whether the change rate of the gas timing correction value exceeds the set change rate of the gas timing. If yes, execute S40; if not, execute S50;

[0011] S40: Adjust the air pump opening value to meet the air pump opening setting change rate, and / or adjust the gas timing correction value to meet the gas timing setting change rate, and execute S50;

[0012] S50: Execute the air pump opening value and / or combustion timing correction value.

[0013] As a preferred technical solution for the diesel engine exhaust back pressure control method, S20 specifically includes:

[0014] S201: Determine whether the gas temperature t1 in the post-processing assembly is less than α. If yes, execute S202; otherwise, execute S203.

[0015] S202: Determine that the post-processing low-temperature operating condition is met, determine the turbine exhaust target back pressure value MAP1, and execute S208;

[0016] S203: Determine whether the engine cycle injection amount t2 is less than β. If yes, execute S204; otherwise, execute S205.

[0017] S204: Determine that the operating condition is low load or reverse drag, determine the target back pressure value MAP2 of the turbine exhaust after the turbine, and execute S208;

[0018] S205: Determine whether the difference between the smoke-limited air-fuel ratio and the theoretical air-fuel ratio is t3 < γ. If yes, execute S206; otherwise, execute S207.

[0019] S206: Determine that the operating condition is a dynamic acceleration condition, determine the target back pressure value MAP3 of the turbine exhaust after the turbine, and execute S208;

[0020] S207: Determine that the operating condition is medium-to-high load and slightly steady state, calculate the air pump opening value and gas timing correction value through MPC, and execute S30;

[0021] S208: Determine the opening value of the air pump according to the target back pressure value of the exhaust after the turbine, and execute S30.

[0022] As a preferred technical solution for the diesel engine exhaust back pressure control method, S202 specifically includes:

[0023] S2021: Create a target MAP1 table for exhaust back pressure after the turbine through engine bench testing, including engine speed, engine fuel consumption, and MAP1 value. The MAP1 value determined at each engine speed ensures that the gas in the aftertreatment assembly reaches the optimal operating temperature and the engine fuel consumption is minimized.

[0024] S2022: Select the MAP1 value corresponding to the current engine speed and execute S208.

[0025] As a preferred technical solution for the diesel engine exhaust back pressure control method, S204 specifically includes:

[0026] S2041: Create a MAP2 table for target back pressure of turbine exhaust through engine bench testing, including engine speed, engine comprehensive operating cost, and MAP2 value. The MAP2 value determined at each engine speed minimizes the engine comprehensive operating cost.

[0027] S2042: Select the MAP2 value corresponding to the current engine speed and execute S208.

[0028] As a preferred technical solution for the diesel engine exhaust back pressure control method, S206 specifically includes:

[0029] S2061: Create a MAP3 table for target back pressure after the turbine exhaust through engine bench testing. This table includes engine speed, 2S torque difference, 2S acceleration difference, engine fuel consumption, and MAP3 value. The MAP3 value determined at each engine speed maximizes the 2S torque difference, the 2S acceleration difference, and minimizes engine fuel consumption.

[0030] S2062: Select the MAP3 value corresponding to the current engine speed and execute S208.

[0031] As a preferred technical solution of the diesel engine exhaust back pressure control method, S208 specifically includes: the opening of the air pump is determined by PID closed-loop control to reach the post-turbine exhaust target back pressure value.

[0032] As a preferred technical solution for the diesel engine exhaust back pressure control method, S207: the method for determining the air pump opening value and the gas timing correction value specifically includes:

[0033] The final comprehensive cost formula can be calculated based on fuel consumption and nitrogen oxide emissions as follows: C_total = UP_fuel*P_eng*BSFC+UP_fuel*P_pump*BSFC+UP_urea*M_NOx*C, where C_total is the total cost; UP_fuel is the average fuel price, RMB / L; P_eng is the current engine power, kW; BSFC is the current fuel consumption rate, L / kWh; P_pump is the current air pump power, kW; UP_urea is the average urea price, RMB / L; M_NOx is the current NOx generation rate, kg / h; C is the urea to NOx conversion coefficient;

[0034] Simplifying this into a calculation formula related to input quantities, we obtain C_total = UP_fuel*P_eng*BSFC(1+a1*dR_fan+a2*dSOI_main)+UP_fuel*P_pump(1+b*dR_fan)*BSFC+UP_urea*M_NOx*(1+c1*dR_fan+c2*dSOI_main)*C. Except for dR_fan and dSOI_main, all other constants are related to the operating conditions.

[0035] The formula for evaluating downstream NOx emissions based on upstream NOx and current reaction efficiency is as follows: EM2_NOx = M_NOx*η_SCR / (M_exhmass*ρ_NOx)*1E6, where EM2_NOx is the downstream NOx concentration, ppm; M_NOx is the NOx generation rate, kg / h; η_SCR is the current reaction efficiency of the SCR model; M_exhmass is the current exhaust flow, kg / h; ρ_NOx is the recommended NOx density. Similarly, M_NOx can be simplified to M_NOx*(1+c1*dR_fan+c2*dSOI_main), where c1 and c2 are the rates of change of NOx generation under current operating conditions with changes in air pump opening and SOI, obtained from bench tests.

[0036] The cost function is set to J,

[0037]

[0038] The items in the series are the weighted square sum of the output deviation (assuming the target is 0) and the control quantity at the subsequent k moments. a, b, c, and d are the weights of the predictive control. According to the minimum J, dR_fan and dSOI_main can be solved to obtain the optimal air pump opening and combustion timing values ​​at the subsequent moments.

[0039] As a preferred technical solution of the diesel engine exhaust back pressure control method, a, b, c and d are adjustable respectively.

[0040] On the other hand, the present invention provides a diesel engine after-treatment device for implementing the diesel engine exhaust back pressure control method in any of the above-mentioned schemes, wherein the diesel engine after-treatment device includes an engine, a turbine, an after-treatment assembly, an air pump, an atmospheric pressure sensor, an exhaust temperature sensor and an exhaust pressure sensor, the exhaust gas interface of the engine is connected to the air inlet of the turbine, the air outlet of the turbine is connected to the air inlet of the after-treatment assembly, the air outlet of the after-treatment assembly is connected to the air inlet of the air pump, the atmospheric pressure sensor is used to detect the ambient pressure of the engine operation, the exhaust temperature sensor and the exhaust pressure sensor are used to detect the post-turbine exhaust temperature and post-turbine exhaust pressure of the turbine, respectively.

[0041] In one aspect, the present invention provides a vehicle comprising the diesel engine exhaust back pressure control method according to any one of the above schemes, and the diesel engine after-treatment device according to any one of the above schemes.

[0042] The beneficial effects of the present invention are:

[0043] The present invention provides a diesel engine exhaust backpressure control method, a diesel engine aftertreatment device, and a vehicle. The method is implemented using a diesel engine aftertreatment device comprising an engine, a turbine, an aftertreatment assembly, and an air pump. The engine's exhaust port is connected to the turbine's air inlet, the turbine's air outlet is connected to the aftertreatment assembly's air inlet, and the aftertreatment assembly's air outlet is connected to the air pump's air inlet. By adjusting the air pump's opening, the exhaust backpressure after the turbine's vortex can be flexibly and proactively adjusted, thereby regulating engine performance. The temperature of the gas within the aftertreatment assembly is also adjusted, thereby improving the aftertreatment assembly's processing efficiency.

[0044] The diesel engine exhaust back pressure control method includes: S10: reading the detection data of the engine after-treatment device, including the gas temperature t1 in the after-treatment assembly, the engine cycle injection amount t2 and the smoke limit air-fuel ratio; S20: determining the opening of the air pump and / or the combustion timing correction value according to the detection data of the engine after-treatment device; S30: judging whether the air pump opening value exceeds the air pump opening change rate, and / or whether the gas timing value exceeds the gas timing change rate, if yes, executing S40, otherwise executing S50; S40: adjusting the air pump opening value to meet the air pump opening change rate, and / or adjusting the gas timing value to meet the gas timing change rate, executing S50; S50: executing the air pump opening value and / or combustion timing value. By reading the detection data of the engine after-processing device, the current working condition of the engine can be determined. Therefore, the most suitable air pump opening value and / or combustion timing correction value are determined according to the current working condition, and it is judged whether the air pump opening value exceeds the air pump opening change rate, and / or whether the gas timing correction value exceeds the gas timing change rate. If it does not exceed the change rate, the selected air pump opening value and / or gas timing correction value can be executed on the engine after-processing device. If there is a situation where the change rate is exceeded, it means that the engine after-processing device cannot perform normally under the above values, so it is necessary to correct the selected air pump opening value and / or gas timing correction value to make it consistent with the change rate. This method can flexibly and actively adjust the exhaust back pressure after the turbine, thereby adjusting the performance of the engine, while adjusting the temperature of the gas in the after-processing assembly and improving the processing efficiency of the after-processing assembly. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 Schematic diagram of the structure of a diesel engine after-treatment device in an embodiment of the present invention;

[0046] Figure 2 Flowchart of a method for controlling exhaust back pressure of a diesel engine according to an embodiment of the present invention.

[0047] In the picture:

[0048] 1. Atmospheric pressure sensor; 2. Exhaust temperature sensor; 3. Exhaust pressure sensor. DETAILED DESCRIPTION

[0049] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0050] In the description of the present invention, it should be noted that the terms "center", "up", "down", "left", "right", "vertical", "horizontal", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and are not intended to indicate or imply that the devices or elements referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention. In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance. Among them, the terms "first position" and "second position" are two different positions, and the first feature being "above", "above" and "above" the second feature includes the first feature being directly above and obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. The first feature being "below", "below" and "below" the second feature includes the first feature being directly below and obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0051] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed, detachable, or integral connections; mechanical or electrical connections; direct or indirect connections through an intermediate medium; and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0052] The following describes embodiments of the present invention in detail. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended only to explain the present invention and are not to be construed as limiting the present invention.

[0053] like Figure 1As shown, this embodiment provides a diesel engine aftertreatment device, which includes an engine, a turbine, an aftertreatment assembly, an air pump, an atmospheric pressure sensor 1, an exhaust temperature sensor 2, and an exhaust pressure sensor 3. The engine's exhaust interface is connected to the turbine's air inlet, the turbine's air outlet is connected to the aftertreatment assembly's air inlet, and the aftertreatment assembly's air outlet is connected to the air pump's air inlet. The atmospheric pressure sensor 1 is used to detect the ambient pressure of the engine's operation, and the exhaust temperature sensor 2 and exhaust pressure sensor 3 are used to detect the turbine's post-turbine exhaust temperature and post-turbine exhaust pressure, respectively. When the engine is operating, the engine's exhaust gas is discharged into the atmosphere through the turbine, aftertreatment assembly, and air pump. During this process, the exhaust gas temperature within the aftertreatment assembly determines the aftertreatment assembly's treatment effect on the exhaust gas. Therefore, by adjusting the air pump opening, the turbine's post-turbine exhaust back pressure can be adjusted, thereby achieving regulation of the exhaust gas temperature entering the aftertreatment assembly. At the same time, the post-turbine exhaust back pressure also affects the engine's performance.

[0054] The exhaust temperature sensor 2 and the exhaust pressure sensor 3 are both installed between the turbine and the after-treatment assembly to detect the exhaust temperature and exhaust pressure after the turbine.

[0055] The atmospheric pressure sensor 1 is installed on the vehicle body to monitor the ambient pressure of the engine, that is, the exhaust pipe outlet pressure, which is used to calculate the energy consumption of the air pump.

[0056] like Figure 2 As shown, the diesel engine exhaust back pressure control method includes:

[0057] S10: Reading test data from the engine aftertreatment device, including the gas temperature t1 within the aftertreatment assembly, the engine cycle fuel injection amount t2, and the smoke-limited air-fuel ratio. In this step, the exhaust temperature sensor detects the exhaust temperature after the turbine, which is the gas temperature t1 within the aftertreatment assembly. The engine cycle fuel injection amount t2 and the smoke-limited air-fuel ratio are determined based on the engine's fuel injection and combustion systems.

[0058] S20: Determine the opening degree of the air pump and / or the combustion timing correction value according to the detection data of the engine after-treatment device.

[0059] S20 specifically includes:

[0060] S201: Determine whether the gas temperature t1 in the post-processing assembly is less than α. If yes, execute S202; otherwise, execute S203.

[0061] In this step, the value range of α is 220°C-300°C, preferably 220°C.

[0062] S202: Determine that the post-processing low-temperature operating condition is met, determine the turbine exhaust target back pressure value MAP1, and execute S208.

[0063] In this step, S202 specifically includes:

[0064] S2021: Through engine bench tests, a MAP1 table of target back pressure of after-turbine exhaust is produced, including engine speed, engine fuel consumption and MAP1 value. The MAP1 value determined at each engine speed makes the gas in the after-treatment assembly reach the optimal operating temperature and the engine fuel consumption is the lowest. The engine is bench tested in advance. When the engine is working at a preset speed, different MAP1 values ​​are selected for testing, and then a MAP1 value corresponding to the engine speed is selected to make the gas temperature in the after-treatment assembly reach the optimal operating temperature and the engine fuel consumption is the lowest. This makes the after-treatment assembly most efficient in treating exhaust gas. Therefore, the engine speed, engine fuel consumption and MAP1 value form a MAP1 table of target back pressure of after-turbine exhaust. The corresponding MAP1 value can be selected through the engine speed.

[0065] S2022: Select the MAP1 value corresponding to the current engine speed and execute S208.

[0066] S203: Determine whether the engine cycle injection amount t2 is less than β. If yes, execute S204; otherwise, execute S205.

[0067] In this step, the selected value of β is between 8 mg and 20 mg, preferably 10 mg.

[0068] S204: Determine that the operating condition is low load or reverse drag, determine the target back pressure value MAP2 of the turbine exhaust after the turbine, and execute S208.

[0069] In this step, S204 specifically includes:

[0070] S2041: Create a MAP2 table for target backpressure after the turbine exhaust through engine bench testing. This table includes engine speed, engine comprehensive operating cost, and MAP2 value. The MAP2 value determined at each engine speed minimizes the engine comprehensive operating cost. The engine is bench tested in advance. While operating at a preset engine speed, various MAP2 values ​​are selected to determine a MAP2 value that corresponds to the engine speed and minimizes the engine comprehensive operating cost. Thus, a MAP2 table for target backpressure after the turbine exhaust is formed using engine speed, engine comprehensive operating cost, and MAP2 value. The corresponding MAP2 value can be selected based on the engine speed.

[0071] S2042: Select the MAP2 value corresponding to the current engine speed and execute S208.

[0072] S205: Determine whether the difference between the smoke-limited air-fuel ratio and the theoretical air-fuel ratio t3 is less than γ. If yes, execute S206; otherwise, execute S207.

[0073] In this step, the selected value of γ is a number between 0.3 and 0.7, preferably 0.5.

[0074] S206: Determine that the condition is a dynamic acceleration condition, determine the target back pressure value MAP3 of the exhaust gas after the turbine, and execute S208.

[0075] S206 specifically includes:

[0076] S2061: Create a MAP3 table for the target backpressure of the turbocharger exhaust through engine bench testing. This table includes engine speed, 2S torque difference, 2S acceleration difference, engine fuel consumption, and MAP3 values. The MAP3 value determined at each engine speed maximizes the 2S torque difference, the 2S acceleration difference, and minimizes engine fuel consumption. The engine is bench tested in advance. While operating at a preset engine speed, various MAP3 values ​​are selected to determine a MAP3 value corresponding to the engine speed that maximizes the 2S torque difference, the 2S acceleration difference, and minimizes engine fuel consumption. Therefore, a MAP3 table for the target backpressure of the turbocharger exhaust is formed using engine speed, MAP3, 2S torque difference, 2S acceleration, engine fuel consumption, and MAP3 values. The corresponding MAP3 value can be selected based on the engine speed.

[0077] S2062: Select the MAP3 value corresponding to the current engine speed.

[0078] S207: Determine that the operating condition is a medium-to-high load, slightly steady state. Calculate the air pump opening value and the gas timing correction value through MPC, and execute S30.

[0079] In this step, the method for determining the air pump opening value and the gas timing correction value specifically includes:

[0080] The final comprehensive cost formula can be calculated based on fuel consumption and nitrogen oxide emissions as follows: C_total = UP_fuel*P_eng*BSFC+UP_fuel*P_pump*BSFC+UP_urea*M_NOx*C, where C_total is the total cost; UP_fuel is the average fuel price, RMB / L; P_eng is the current engine power, kW; BSFC is the current fuel consumption rate, L / kWh; P_pump is the current air pump power, kW; UP_urea is the average urea price, RMB / L; M_NOx is the current NOx generation rate, kg / h; C is the urea to NOx conversion coefficient;

[0081] Simplifying this into a calculation formula related to input quantities, we obtain C_total = UP_fuel*P_eng*BSFC(1+a1*dR_fan+a2*dSOI_main)+UP_fuel*P_pump(1+b*dR_fan)*BSFC+UP_urea*M_NOx*(1+c1*dR_fan+c2*dSOI_main)*C. Except for dR_fan and dSOI_main, all other constants are related to the operating conditions.

[0082] The formula for evaluating downstream nitrogen oxide (NOx) emissions based on upstream nitrogen oxides and current reaction efficiency is as follows: EM2_NOx = M_NOx*η_SCR / (M_exhmass*ρ_NOx)*1E6, where EM2_NOx is the downstream NOx concentration, ppm; M_NOx is the NOx generation rate, kg / h; η_SCR is the current reaction efficiency of the SCR model; M_exhmass is the current exhaust flow, kg / h; ρ_NOx is the recommended NOx density. Similarly, M_NOx can be simplified to M_NOx*(1+c1*dR_fan+c2*dSOI_main), where c1 and c2 are the change rates of nitrogen oxide generation under current operating conditions with changes in air pump opening and SOI, obtained from bench tests.

[0083] The cost function is set to J,

[0084]

[0085] The items in the series are the weighted square sum of the output deviation (assuming the target is 0) and the control quantity at the subsequent k moments. a, b, c, and d are the weights of the predictive control. According to the minimum J, dR_fan and dSOI_main can be solved to obtain the optimal air pump opening and combustion timing values ​​at the subsequent moments.

[0086] Optionally, a, b, c, and d are individually adjustable. By minimizing J, the optimal dR_fan and dSOI_main values ​​for the next k moments can be calculated. The optimal air pump opening and combustion timing at these subsequent moments are then used for control. Weights can be adjusted based on specific needs. Increasing item a prioritizes fuel consumption and urea consumption costs, while increasing item b prioritizes downstream NOx emissions. The weights c and d represent the control over the rate of change of the air pump opening correction and combustion timing correction values. Due to insufficient model feedback, excessive correction values ​​can lead to deterioration in overall performance. Simultaneously, the combustion timing and air pump opening outputs for each operating condition are limited as MPC constraints to prevent the correction results from deviating too far from the baseline values. The maximum and minimum values ​​for the combustion timing and air pump opening corrections for these constraints are determined through bench testing. The upper and lower limits for combustion timing and air pump opening that occur when fuel consumption and NOx levels deteriorate significantly, or when cylinder pressure exceeds the limit, are determined based on bench testing. These limits are then subtracted from the baseline map values ​​to determine the correction range limits.

[0087] S208: Determine the opening value of the air pump according to the target back pressure value of the exhaust after the turbine, and execute S30.

[0088] S208 specifically includes determining whether the opening of the air pump reaches the target back pressure value of the after-turbine exhaust through PID closed-loop control.

[0089] S30: Determine whether the change rate of the gas pump opening value exceeds the set change rate of the gas pump opening, and / or whether the change rate of the gas timing correction value exceeds the set change rate of the gas timing. If yes, execute S40; if not, execute S50;

[0090] In this step, the calculated air pump opening value and / or gas timing value may not meet the normal working requirements. For example, when the air pump opening selection change rate is 200%, the air pump opening value is unreasonable and does not meet the requirement of 100% air pump opening setting change rate. Therefore, it needs to be adjusted. Therefore, execute S40. When it meets the change rate requirement, execute S50 directly.

[0091] S40: Adjust the gas pump opening value to meet the set gas pump opening change rate, and / or adjust the gas timing correction value to meet the set gas timing change rate, and then execute S50. In this step, any gas pump opening values ​​that do not meet the set change rate requirements are adjusted so that their change rate meets the set gas pump opening change rate. The gas timing correction value modification logic is the same as the gas pump opening value modification logic and will not be further described here.

[0092] S50: Execute the air pump opening value and / or combustion timing correction value.

[0093] In summary, by reading the detection data of the engine after-processing device, the current operating condition of the engine can be determined. Therefore, the most suitable air pump opening value and / or combustion timing correction value are determined according to the current operating condition, and it is judged whether the air pump opening value exceeds the air pump opening change rate, and / or whether the gas timing correction value exceeds the gas timing change rate. If it does not exceed the change rate, the selected air pump opening value and / or gas timing correction value can be executed on the engine after-processing device. If there is a situation where the change rate is exceeded, it means that the engine after-processing device cannot be executed normally under the above values, so it is necessary to correct the selected air pump opening value and / or gas timing correction value to make it consistent with the change rate. This method can flexibly and actively adjust the exhaust back pressure after the turbine, thereby adjusting the performance of the engine, while adjusting the temperature of the gas in the after-processing assembly and improving the processing efficiency of the after-processing assembly.

[0094] This embodiment also provides a vehicle, comprising the diesel engine exhaust back pressure control method in the above solution and the diesel engine after-treatment device in the above solution.

[0095] Obviously, the above embodiments of the present invention are merely examples for the purpose of clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. Those skilled in the art will appreciate that other variations or modifications can be made based on the above description. It is not necessary and impossible to enumerate all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the claims of the present invention.

Claims

1. A diesel engine exhaust back pressure control method, characterized in that: The method is implemented by a diesel engine after-treatment device, which includes an engine, a turbine, an after-treatment assembly, and an air pump, wherein the exhaust port of the engine is connected to the air inlet of the turbine, the air outlet of the turbine is connected to the air inlet of the after-treatment assembly, and the air outlet of the after-treatment assembly is connected to the air inlet of the air pump; The diesel engine exhaust back pressure control method comprises: S10: Reading the detection data of the engine after-treatment device, including the gas temperature t1 in the after-treatment assembly, the engine cycle injection amount t2 and the smoke limit air-fuel ratio; S20: determining the opening degree of the air pump and / or the combustion timing correction value according to the detection data of the engine after-treatment device; S30: Determine whether the change rate of the gas pump opening value exceeds the set change rate of the gas pump opening, and / or whether the change rate of the gas timing correction value exceeds the set change rate of the gas timing. If yes, execute S40; if not, execute S50; S40: Adjust the air pump opening value to meet the air pump opening setting change rate, and / or adjust the gas timing correction value to meet the gas timing setting change rate, and execute S50; S50: Execute the air pump opening value and / or combustion timing correction value; S20 specifically includes: S201: Determine whether the gas temperature t1 in the post-processing assembly is less than α. If yes, execute S202; otherwise, execute S203. S202: Determine that the post-processing low-temperature operating condition is met, determine the turbine exhaust target back pressure value MAP1, and execute S208; S203: Determine whether the engine cycle injection amount t2 is less than β. If yes, execute S204; otherwise, execute S205. S204: Determine that the operating condition is low load or reverse drag, determine the target back pressure value MAP2 of the turbine exhaust after the turbine, and execute S208; S205: Determine whether the difference between the smoke-limited air-fuel ratio and the theoretical air-fuel ratio is t3 < γ. If yes, execute S206; otherwise, execute S207. S206: Determine that the operating condition is a dynamic acceleration condition, determine the target back pressure value MAP3 of the turbine exhaust after the turbine, and execute S208; S207: Determine that the operating condition is medium-to-high load and slightly steady state, calculate the air pump opening value and gas timing correction value through MPC, and execute S30; S208: Determine the air pump opening value according to the target back pressure value of the exhaust after the turbine, and execute S30; The value range of α is 220° C.-300° C., the value range of β is 8 mg-20 mg, and the value range of γ is 0.3-0.

7.

2. The diesel engine exhaust back pressure control method according to claim 1, characterized in that: S202 specifically includes: S2021: Create a target MAP1 table for exhaust back pressure after the turbine through engine bench testing, including engine speed, engine fuel consumption, and MAP1 value. The MAP1 value determined at each engine speed ensures that the gas in the aftertreatment assembly reaches the optimal operating temperature and the engine fuel consumption is minimized. S2022: Select the MAP1 value corresponding to the current engine speed and execute S208.

3. The diesel engine exhaust back pressure control method according to claim 1, characterized in that: S204 specifically includes: S2041: Generate a MAP2 table for the target exhaust back pressure after turbulence through engine bench testing. This table includes engine speed, engine comprehensive operating cost, and MAP2 value. The MAP2 value determined at each engine speed minimizes the engine comprehensive operating cost. S2042: Select the MAP2 value corresponding to the current engine speed and execute S208.

4. The diesel engine exhaust back pressure control method according to claim 1, characterized in that: S206 specifically includes: S2061: Create a MAP3 table for target back pressure after the turbine exhaust through engine bench testing. This table includes engine speed, 2S torque difference, 2S acceleration difference, engine fuel consumption, and MAP3 value. The MAP3 value determined at each engine speed maximizes the 2S torque difference, the 2S acceleration difference, and minimizes engine fuel consumption. S2062: Select the MAP3 value corresponding to the current engine speed and execute S208.

5. The diesel engine exhaust back pressure control method according to claim 1, characterized in that: S208 specifically includes: determining the opening degree of the air pump to reach the target back pressure value of the turbine exhaust through PID closed-loop control.

6. Diesel engine after-treatment device, characterized in that: The invention is used to implement the diesel engine exhaust back pressure control method according to any one of claims 1 to 5, wherein the diesel engine after-treatment device comprises an engine, a turbine, an after-treatment assembly, an air pump, an atmospheric pressure sensor (1), an exhaust temperature sensor (2) and an exhaust pressure sensor (3), the exhaust gas interface of the engine is connected to the air inlet of the turbine, the air outlet of the turbine is connected to the air inlet of the after-treatment assembly, and the air outlet of the after-treatment assembly is connected to the air inlet of the air pump, the atmospheric pressure sensor (1) is used to detect the ambient pressure of the engine, the exhaust temperature sensor (2) and the exhaust pressure sensor (3) are used to detect the exhaust temperature and exhaust pressure of the turbine after the turbine respectively.

7. A vehicle, characterized in that It includes the diesel engine after-treatment device according to claim 6.

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