DPF regeneration control method based on two-stage SCR system

Abstract

The application discloses a DPF regeneration control method based on a two-stage SCR system and relates to engine exhaust treatment technology. A bypass pipeline is arranged at the two ends of a close-coupled SCR of a front stage of the two-stage SCR system, and a bypass valve is arranged in the bypass pipeline; when DPF active regeneration is performed, the actual DPF temperature of the DPF is acquired, and the opening degree of the bypass valve and the far-after-injection fuel quantity in the cylinder are subjected to closed-loop PID control according to the temperature deviation between the set DPF target temperature and the actual DPF temperature. The application reduces the exhaust back pressure of the engine, reduces fuel consumption, reduces emissions, and meets the requirements of emission regulations.

Description

Technical Field

[0001] This invention relates to engine exhaust gas treatment technology, and more specifically, to a DPF regeneration control method based on a two-stage SCR system. Background Technology

[0002] With increasingly stringent emission regulations, Europe has introduced the Euro 7 emission standard, which further reduces the pollutant nitrogen oxides (NOx). x The requirements for particulate matter (PN), carbon monoxide (CO), and increased emissions of nitrogen oxides (N2O) and unconventional pollutants such as formaldehyde have been raised. Currently, various suppliers and engine companies are researching aftertreatment systems that meet Euro 7 emission limits. The mainstream aftertreatment system is a tightly coupled selective reduction catalytic converter (SCR) system (hereinafter referred to as tightly coupled SCR) added to the Euro VI aftertreatment system to treat nitrogen oxides (NOx) during cold starts. x And N2O and PN under different emission test cycles. Among them, the DPF filters particulate pollutants and PN from the engine. When the particulate matter accumulated inside the DPF reaches the regeneration limit, active regeneration is activated to remove the particulate matter inside the DPF, thereby reducing the engine back pressure.

[0003] like Figure 1 As shown, during active regeneration of the DPF in a single-stage SCR aftertreatment system, in-cylinder far-injection reduces intake airflow through the throttle valve and activates near-injection to increase exhaust temperature, rapidly raising the DOC temperature to the HC ignition temperature. Once the DOC ignition temperature is reached, in-cylinder far-injection is activated, allowing some fuel from the engine to enter the exhaust. This fuel in the exhaust rapidly increases the exhaust temperature, raising the internal temperature of the DPF to the active regeneration oxidation temperature of the engine particulate contaminants collected by the DPF, clearing particulate matter from the DPF and reducing the exhaust back pressure.

[0004] Because of the addition of a close-coupled SCR, most of the fuel injected into the cylinder is absorbed by the close-coupled SCR in the front stage, resulting in insufficient fuel in the exhaust. This causes the DOC to be unable to quickly raise the exhaust temperature, resulting in a low regeneration temperature that cannot reach the ignition temperature of the particulate matter inside the DPF, leading to regeneration failure, increased back pressure, worsened fuel consumption, and reduced power. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to address the shortcomings of the prior art by providing a DPF regeneration control method based on a two-stage SCR system, which can effectively reduce the exhaust back pressure of the engine and reduce fuel consumption.

[0006] The present invention discloses a DPF regeneration control method based on a two-stage SCR system, which adds bypass pipes to both ends of the tightly coupled SCR in the front stage of the two-stage SCR system and installs a bypass valve in the bypass pipes; when the DPF is actively regenerated, the actual temperature of the DPF is obtained, and the opening degree of the bypass valve and the in-cylinder fuel injection quantity are controlled in a closed loop according to the temperature deviation between the set target temperature and the actual temperature of the DPF.

[0007] As a further improvement, in the closed-loop PID control, the control parameter for the opening degree of the bypass valve is determined by the following formula:

[0008] u(t2)=K p2 ×[e(t)+K i2 +K d2 ];

[0009] In the formula, u(t2) is the control parameter for the opening degree of the bypass valve; K p2 K is the proportional coefficient for controlling the opening of the bypass valve; e(t) is the temperature deviation; i2 This is the integral control coefficient for the bypass valve opening. T i2 d is the integral control time for the bypass valve opening. t2 K represents the integral time for the bypass valve opening, where t is the regeneration temperature correction time; d2 This is the differential control coefficient for the bypass valve opening. T d2 t2 is the differential control time of the bypass valve opening, de(t2) is the differential time of the bypass valve, and t2 is the time for the bypass valve opening to be corrected based on the regeneration temperature.

[0010] Furthermore, the upper and lower limits of the bypass valve opening are preset; in the closed-loop PID control, the control parameters for controlling the opening of the bypass valve are within the range of the upper and lower limits.

[0011] As a further improvement, in the closed-loop PID control, the control parameter for the in-cylinder remote injection quantity is determined by the following formula:

[0012] u(t1)=K p1 ×[e(t)+K i1 +K d1 ];

[0013] In the formula, u(t1) is the control parameter for the in-cylinder remote injection quantity; K p1 K is the proportional coefficient for post-injection quantity control; e(t) is the temperature deviation; i1 This is the integral control coefficient for the post-injection quantity. T i1 For the post-injection quantity integral control time, d t1K represents the post-injection quantity integral time, where t is the regeneration temperature correction time; d1 This is the differential control coefficient for the post-injection quantity. T d1 The differential control time for the post-injection quantity is denoted as de(t1), where de(t1) is the differential time for the post-injection quantity; t1 is the correction time for the post-injection quantity based on the regeneration temperature.

[0014] Furthermore, the upper and lower limits of the in-cylinder remote injection quantity are preset; in the closed-loop PID control, the control parameters of the in-cylinder remote injection quantity are controlled within the range of the upper and lower limits of the fuel quantity.

[0015] As a further improvement, the conditions for the active regeneration of the DPF are as follows:

[0016] When the actual temperature of the DPF is between the set temperature threshold one and the set temperature threshold two, the DPF actively regenerates.

[0017] Furthermore, the first temperature threshold is 600℃-700℃; the second temperature threshold is 250℃-300℃.

[0018] Beneficial effects

[0019] The advantages of this invention are:

[0020] 1. Add bypass pipes to both ends of the pre-stage tightly coupled SCR in a two-stage SCR system, and install bypass valves in the bypass pipes. When the regeneration condition parameters in the DPF reach the regeneration limit, the bypass valve opens, enabling in-cylinder remote injection. Fuel in the exhaust directly enters the DOC without passing through the pre-stage tightly coupled SCR, thus rapidly increasing the exhaust temperature to the particulate regeneration temperature, thereby reducing engine exhaust back pressure and fuel consumption. After regeneration is complete, the bypass valve closes, allowing the exhaust to pass through the pre-stage tightly coupled SCR, thus reducing emissions.

[0021] 2. During DPF active regeneration, the opening degree of the bypass valve and the amount of fuel injected into the cylinder are controlled by closed-loop PID based on the temperature deviation between the set target temperature of the DPF and the actual temperature of the DPF. This achieves precise control of the opening degree of the bypass valve and the amount of fuel injected into the cylinder, resulting in lower fuel consumption and better emission performance. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of a single-stage SCR system.

[0023] Figure 2 This is a schematic diagram of the two-stage SCR system of the present invention;

[0024] Figure 3 This is a flowchart of the DPF regeneration control method of the present invention;

[0025] Figure 4 This is a schematic diagram of the closed-loop PID control logic of the present invention. Detailed Implementation

[0026] The present invention will be further described below with reference to embodiments, but this does not constitute any limitation on the present invention. Any limited modifications made by any person within the scope of the claims of the present invention are still within the scope of the claims of the present invention.

[0027] See Figures 2-4 This invention discloses a DPF regeneration control method based on a two-stage SCR system. By adding bypass pipes to both ends of the tightly coupled SCR in the first stage of the two-stage SCR system, and installing bypass valves in the bypass pipes, the bypass valves open when the regeneration condition parameters in the DPF reach the regeneration limit, allowing engine exhaust to bypass the first-stage tightly coupled SCR. After in-cylinder remote injection is activated, fuel in the exhaust directly enters the DOC (Discharge Code), bypassing the first-stage tightly coupled SCR, thereby rapidly increasing the exhaust temperature to reach the particulate regeneration temperature, thus reducing engine exhaust back pressure and fuel consumption. After regeneration is complete, the bypass valve closes, allowing exhaust to pass through the first-stage tightly coupled SCR, thereby reducing emissions and meeting emission regulations.

[0028] Specifically, in a two-stage SCR system, when parameters such as carbon load, counter, and engine differential pressure protection exceed or equal to set thresholds, a regeneration request is triggered, and the two-stage SCR system enters regeneration mode. At this time, the engine mode coordinator configures the intake system configuration table, fuel system configuration table, and exhaust system configuration table in regeneration mode via a regeneration request, and begins to increase the internal temperature of the DPF. These configurations are completed in the regeneration coordinator before being transmitted to the engine mode coordinator. When the actual DPF temperature is between the set temperature threshold one and the set temperature threshold two (including the temperature thresholds themselves), the DPF actively regenerates. When the actual DPF temperature is greater than temperature threshold one or lower than temperature threshold two, DPF regeneration protection is activated, exiting regeneration mode and entering normal mode.

[0029] The regeneration coordinator, by monitoring data from receiving nodes and determining how to send or receive this data to target devices, achieves unified data collection and processing. It controls the ECU's data nodes, ensuring the engine and aftertreatment system operate in a stable, reliable, and low-power state, thereby extending their lifespan and optimizing energy consumption. Furthermore, the regeneration coordinator continuously receives and analyzes information such as data volume and communication status in the network, dynamically adjusting network transmission routes and rates based on actual conditions. This results in better adaptability and stability for the wireless sensor network, providing automatic network adjustment capabilities.

[0030] The first temperature threshold is 650℃, and the second temperature threshold is 270℃. The purpose of this setting is to prevent the DPF from burning out when its internal temperature exceeds 650℃, and to prevent the injected fuel from igniting after entering the DOC when the internal temperature of the DPF is below 270℃, resulting in excessive HC emissions.

[0031] To achieve lower fuel consumption and better emission performance, the DPF regeneration control method of the present invention also acquires the actual temperature of the DPF during active DPF regeneration, and performs closed-loop PID control on the opening degree of the bypass valve and the in-cylinder remote injection quantity based on the temperature deviation between the set DPF target temperature and the actual DPF temperature.

[0032] In closed-loop PID control, the in-cylinder post-injection quantity (hereinafter referred to as post-injection quantity) and the bypass valve opening are expressed by the following formulas:

[0033]

[0034] In the above formula, u(t1) is the control parameter for the in-cylinder remote injection quantity; K p1 K is the proportional coefficient for post-injection quantity control; e(t) is the temperature deviation; i1 T is the integral control coefficient for the post-injection quantity. i1 For the integral control time of the post-injection quantity; d t1 K is the integral time for the post-injection quantity. d1 T is the differential control coefficient for the post-injection quantity. d1 Here, de(t1) is the derivative control time for the post-injection quantity; t1 is the post-injection quantity correction time based on regeneration temperature; u(t2) is the control parameter for the opening degree of the bypass valve; K p2 K is the proportional coefficient for controlling the opening degree of the bypass valve. i2 T is the integral control coefficient for the bypass valve opening. i2 The integral control time for the bypass valve opening; d t2 K is the integral time for the bypass valve opening. d2 T is the differential control coefficient for the bypass valve opening; d2 t1 is the differential control time of the bypass valve opening; de(t2) is the differential time of the bypass valve; t2 is the time of the bypass valve opening based on the regeneration temperature correction; t1 is the time of the post-injection quantity based on the regeneration temperature correction; t2 is the time of the bypass valve opening based on the regeneration temperature correction; t is the regeneration temperature correction time, t=t1+t2.

[0035] To avoid overshoot and its impact on engine reliability, this invention presets an upper and lower limit for the bypass valve opening, as well as an upper and lower limit for the fuel injection quantity. In closed-loop PID control, the control parameters for the bypass valve opening are kept within the upper and lower limits, while the control parameters for the in-cylinder fuel injection quantity are kept within the upper and lower limits, effectively ensuring engine reliability.

[0036] Specifically, the upper limit of the opening is 100%; the lower limit of the opening is 0. The upper limit of the fuel quantity is the maximum post-injection quantity when the target temperature is calibrated through open-loop control; the lower limit of the fuel quantity is 0.

[0037] The above description is only a preferred embodiment of the present invention. It should be noted that those skilled in the art can make several modifications and improvements without departing from the structure of the present invention, and these will not affect the effectiveness of the implementation of the present invention or the practicality of the patent.

Claims

1. A DPF regeneration control method based on a two-stage SCR system, characterized in that, Bypass pipes are added to both ends of the tightly coupled SCR in the front stage of the two-stage SCR system, and a bypass valve is installed in the bypass pipes. When the DPF is actively regenerated, the actual temperature of the DPF is obtained, and the opening degree of the bypass valve and the amount of fuel injected into the cylinder are controlled by closed-loop PID based on the temperature deviation between the set target temperature of the DPF and the actual temperature of the DPF. In the closed-loop PID control, the control parameter for the opening degree of the bypass valve is determined by the following formula: u(t2)=K p2 ×[e(t)+K i2 +K d2 ]; In the formula, u(t2) is the control parameter for the opening degree of the bypass valve; K p2 K is the proportional coefficient for controlling the opening of the bypass valve; e(t) is the temperature deviation; i2 This is the integral control coefficient for the bypass valve opening. T i2 d is the integral control time for the bypass valve opening. t2 t is the integral time for the bypass valve opening, and t is the regeneration temperature correction time. K d2 This is the differential control coefficient for the bypass valve opening. T d2 Here, de(t2) is the differential control time for the bypass valve opening, and de(t2) is the differential time for the bypass valve; t2 is the time for the bypass valve opening to be corrected based on the regeneration temperature. In the closed-loop PID control, the control parameter for the in-cylinder far-rear injection quantity is determined by the following formula: u(t1)=K p1 ×[e(t)+K i1 +K d1 ]; In the formula, u(t1) is the control parameter for the in-cylinder remote injection quantity; K p1 K is the proportional coefficient for post-injection quantity control; e(t) is the temperature deviation; i1 This is the integral control coefficient for the post-injection quantity. T i1 For the post-injection quantity integral control time, d t1 t is the post-injection quantity integral time, and t is the regeneration temperature correction time. K d1 This is the differential control coefficient for the post-injection quantity. T d1 The differential control time for the post-injection quantity is denoted as de(t1), where de(t1) is the differential time for the post-injection quantity; t1 is the correction time for the post-injection quantity based on the regeneration temperature.

2. The DPF regeneration control method based on a two-stage SCR system according to claim 1, characterized in that, The upper and lower limits of the bypass valve opening are preset; in the closed-loop PID control, the control parameters for controlling the opening of the bypass valve are within the range of the upper and lower limits.

3. The DPF regeneration control method based on a two-stage SCR system according to claim 1, characterized in that, The upper and lower limits of the in-cylinder remote injection quantity are preset; in the closed-loop PID control, the control parameters of the in-cylinder remote injection quantity are controlled within the range of the upper and lower limits of the fuel quantity.

4. The DPF regeneration control method based on a two-stage SCR system according to claim 1, characterized in that, The conditions for active DPF regeneration are as follows: When the actual temperature of the DPF is between the set temperature threshold one and the set temperature threshold two, the DPF actively regenerates.

5. The DPF regeneration control method based on a two-stage SCR system according to claim 4, characterized in that, The first temperature threshold is 650℃; the second temperature threshold is 270℃.

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