Control Strategy and Control Device for Vehicle Aftertreatment Regeneration in Plateau Environment

Abstract

Control strategy and control device for vehicle aftertreatment regeneration in plateau environment. When calibrating the whole vehicle and engine bench in plateau, collect aftertreatment regeneration test data at different altitudes, obtain the ambient atmospheric pressure A corresponding to the altitude at which the regeneration ability decreases and the temperature cannot meet the regeneration requirements at a certain altitude, and write it into the ECU controller, set as the environmental pressure threshold. At the same time, set the real-time monitored ambient air pressure A1, and compile the ECU controller execution program pulse map; when A1 ≤ A, it is considered to be in the plateau environment. Add a gas supply pipeline in front of the DOC catalyst. When the ECU controller detects that the compression ignition engine enters the active regeneration mode, detect the current ambient air pressure. If A1 ≤ A, then open the gas supply valve, and control the gas supply volume by using the temperatures T1 and T2 fed back by the temperature sensors arranged before and after the DOC catalyst. After detecting the end of regeneration, close the gas supply valve. The present invention enables the engine aftertreatment to be successfully regenerated in the plateau environment and reduces the regeneration difficulty of the engine in the plateau environment.

Description

Technical Field

[0001] The present invention belongs to the technical field of vehicle and engine emission control, and particularly relates to a control strategy and a control device for post-treatment regeneration of a vehicle in a plateau environment. Background Art

[0002] With the upgrading of motor vehicle emission regulations, the requirements for emissions are becoming increasingly strict. Currently, most diesel engines adopt a post-treatment system of a catalytic oxidizer (DOC) + a particulate filter (CDPF particulate trap) + a selective catalytic reduction (SCR) + an ammonia slip catalyst (ASC) to control emissions.

[0003] Due to the design characteristics of a compression-ignition engine, the exhaust gas temperature of the engine is low, and it is in a working state of low speed and high torque for a long time. The main pollutants emitted by the engine are NO X and particulate matter. Moreover, there are many types of vehicles installed by the vehicle manufacturers, and it is impossible to ensure that the post-treatment is within the optimal working temperature range. China has a vast territory, and the driving conditions in most areas cannot ensure the effectiveness of the plain regeneration strategy. When the vehicle operates in a plateau environment for a long time, due to the decrease in the oxygen content in the air caused by the altitude, in order to ensure the power performance in the plateau area, a calibration strategy of over-injecting fuel is basically adopted, which causes great pressure on both the combustion system and the post-treatment system of the engine. The insufficient combustion in the plateau area leads to an increase in the original emissions of pollutants from the engine compared with the plain area. Coupled with the decrease in the oxygen content, these two reasons are likely to cause varying degrees of reduction in the post-treatment conversion efficiency. The back pressure of the CDPF particulate trap catalyst in the post-treatment system after trapping soot is most affected by the plateau environment. This puts forward higher performance requirements for the regeneration ability of the post-treatment of diesel vehicles. And the DOC catalyst, as a key component for increasing the temperature during the active regeneration of the CDPF particulate trap catalyst, has extremely high requirements for its temperature-raising ability.

[0004] The existing vehicle plateau regeneration control strategies basically follow the plain method strategies, without special strategies and devices for regeneration control in the plateau environment. Only by continuously improving the performance of the post-treatment and leaving a large margin for the regeneration function during plain calibration can the emission standards in the plateau environment be met to cover the plateau environment, which brings great pressure to the post-treatment development and practical application. The main defects and deficiencies of the existing technologies are summarized as follows:

[0005] At present, the conventional DOC catalyst technology and the existing calibration strategies can ensure the vehicle regeneration ability under the condition of sufficient oxygen concentration in the plain environment, but they cannot fully adapt to the frequent regeneration in the long-term plateau low-temperature and oxygen-deficient environment. The existing calibration strategies basically adopt a rich injection mode under plateau conditions to ensure the power economy in the plateau. The fuel cannot be completely burned, which has a large load on the post-treatment. After a long time in the plateau environment, the performance of the post-treatment will decline in different situations, and the post-treatment system will have problems such as DOC catalyst poisoning and urea crystallization, resulting in NOX Problems such as excessive emissions, low O2 concentration in the exhaust gas leading to difficult regeneration, will cause failures such as DOC catalyst failure, DPF particulate filter clogging, and DPF particulate filter melting.

[0006] Due to the strict national VI emission standards, the current mainstream calibration strategy for vehicles is to ensure the stability of the engine system by shortening the regeneration mileage and increasing the regeneration times. However, when the vehicle is in a plateau environment for a long time, the regeneration frequency will further increase, resulting in the impact on the fuel economy of the engine and increasing the risk of regeneration failure.

[0007] Both the vehicle and the aftertreatment have a certain design service life. If the vehicle is in a plateau environment for a long time, frequent clogging and regeneration of the aftertreatment will lead to a shortened service life of the engine and the aftertreatment, and there will be a risk of failure within the designed validity period of the aftertreatment system. Summary of the Invention

[0008] The purpose of the present invention is to provide a control strategy and control device for vehicle aftertreatment regeneration in a plateau environment, aiming to solve the problem of difficult regeneration of plateau environment vehicles under existing technical conditions.

[0009] In order to achieve the above purpose, the present invention provides the following technical solutions:

[0010] A control strategy for vehicle aftertreatment regeneration in a plateau environment, enabling the following control strategy during plateau environment regeneration:

[0011] (1) When calibrating the vehicle and the engine bench for plateau, collect the aftertreatment regeneration test data at different altitudes, analyze the regeneration differences of the aftertreatment at different altitudes, and obtain that the regeneration ability decreases and the temperature cannot meet the regeneration requirements at a certain altitude. The ambient atmospheric pressure corresponding to this altitude is A. Write the collected ambient atmospheric pressure A into the ECU controller and set it as the ambient pressure threshold. At the same time, set the real-time monitored ambient air pressure as A1, and compile and form an ECU controller execution program pulse map in combination with the test parameters A and A1;

[0012] (2) After plateau calibration, obtain the ambient atmospheric pressure A. In the control strategy writing, set that when the actual ambient air pressure A1 ≤ A, it is in a plateau environment. Add a gas supply pipeline in front of the DOC catalyst of the aftertreatment system. When the ECU controller detects that the engine enters the active regeneration mode, start the program to detect the current ambient atmospheric pressure, and the detected value is A1. If A1 ≤ the set ambient threshold A, then the ECU controller controls to open the gas supply valve of the gas supply pipeline;

[0013] (3)Gas supply device execution strategy: The ECU controller controls the opening of the gas supply valve of the gas supply device according to the developed strategy, and uses the temperature data fed back by the first temperature sensor T1 set at the inlet of the DOC catalyst and the second temperature sensor T2 set at the inlet of the DPF particulate trap to control the size of the gas supply in real time. When it is detected that the regeneration is over, the gas supply valve is closed, and at the same time, the air pressure and the engine operation mode are continuously monitored, waiting for the next regeneration.

[0014] The control device that can implement the control strategy described in the present invention includes an ECU controller, a gas supply pipeline connected to the exhaust pipe of the vehicle's compression-ignition engine and located before the DOC catalyst in the after-treatment system and its gas supply device. A gas supply valve controlled by the ECU controller to open and close is provided on the gas supply pipeline. A first temperature sensor T1 and a second temperature sensor T2 connected to the ECU controller are respectively provided at the inlet of the DOC catalyst and the inlet of the DPF particulate trap connected behind the DOC catalyst. The ECU controller is also connected to a pressure sensor.

[0015] The present invention has the following beneficial effects:

[0016] It solves the problem of difficult after-treatment regeneration in the plateau environment. A simple and practical vehicle regeneration control device and an efficient control strategy are developed for the plateau environment. By detecting the air pressure, the environment where the vehicle is located is identified, and it is judged whether to enter the plateau regeneration system. When the vehicle enters regeneration and is in the plateau environment, the ECU controller controls the gas supply device to increase appropriate O2 in the exhaust pipe. The temperature sensor is used to monitor the regeneration process in real time, and the regeneration temperature is adjusted in a closed loop, solving the problem of insufficient oxygen concentration in the exhaust gas under the current plateau calibration strategy, ensuring that the DOC catalyst has sufficient oxygen content when spraying fuel after oxidation in the regeneration mode, reducing the performance pressure of the DOC catalyst in the plateau environment, being able to quickly raise the temperature, ensuring that the DPF particulate trap has a sufficient inlet temperature, completely regenerating and removing the trapped particulate matter, reducing the failure rate of the vehicle after-treatment in the plateau environment, and at the same time ensuring that the tail gas meets the emission standards in the plateau environment.

[0017] The present invention can make the after-treatment system regenerate completely. Under the condition of complete regeneration, the regeneration frequency can be greatly shortened, ensuring the stability of the engine system, guaranteeing the power, reducing the number of regenerations and at the same time reducing the number of failures such as blockages can ensure the service life of the after-treatment, reduce the replacement frequency of the after-treatment, reduce fuel consumption, and reduce the vehicle use cost.

[0018] The control strategy developed specifically for the plateau environment in the present invention not only solves the problem of plateau regeneration, but also can effectively reduce the difficulty of calibration in the plain. When calibrating in the plain, there is no need to consider too much the coverage problem of plateau regeneration, saving the development cost. Description of the Drawings

[0019] Figure 1 It is the vehicle regeneration control strategy logic based on the plateau environment of the present invention;

[0020] Figure 2 It is a schematic diagram of a control device that can implement the control strategy of the present invention. DETAILED DESCRIPTION

[0021] The content of the present invention is further described below in conjunction with the accompanying drawings.

[0022] Figure 2 The control device of the present invention is shown as follows, including an ECU (Electronic Control Unit) controller 1, an air supply pipeline 3 and an air supply device 2 connected to the exhaust pipe 6 of the automobile compression ignition engine and located before the post-treatment DOC catalyst, and an air supply valve 4 controlled to open and close by the ECU controller 1 is provided on the air supply pipeline. The ECU controller 1 controls the operation of the compression ignition engine 5. The DPF particulate filter is connected after the DOC catalyst, and a first temperature sensor T1 and a second temperature sensor T2 connected to the ECU controller are respectively provided at the inlet of the DOC catalyst and the inlet of the DPF particulate filter. The ECU controller is also connected to the vehicle's own air pressure sensor 7. The outlet end of the air supply pipeline 3 can be located at any position between the rear end of the supercharger on the exhaust pipe, the air filter and the intake flow meter. The air supply valve is controlled by the ECU controller of the engine.

[0023] like Figure 1 As shown, the control strategy based on vehicle post-processing regeneration in plateau environment of the present invention is enabled during regeneration in plateau environment, and the control strategy is as follows:

[0024] We started to calibrate the vehicle and engine bench at high altitudes, collect post-treatment regeneration test data at different altitudes, collect carbon load data, obtain the regeneration differences of post-treatment at different altitudes, and form a data table for calculation and analysis in the subsequent regeneration monitoring process. When a certain altitude H is reached, the regeneration capacity decreases and the temperature cannot meet the regeneration requirements. The ambient atmospheric pressure corresponding to this altitude H is A. The collected ambient atmospheric pressure A is written into the ECU controller and set as the ambient pressure threshold. At the same time, the real-time monitored ambient pressure is set to A1. Combined with the test parameters A and A1, the ECU controller execution program map (MAP) is written.

[0025] Perform engine regeneration mode monitoring: After calibration at high altitudes, the ambient atmospheric pressure A is obtained. In the control strategy programming, it is set that when the actual ambient air pressure A1 ≤ A, it is in a high-altitude environment. During regeneration mode monitoring, the ECU controller monitors in real time through the differential pressure sensor of the aftertreatment system (currently, all aftertreatment systems with DPF are equipped with differential pressure sensors for auxiliary regeneration monitoring). When the ECU controller detects that the back pressure difference of the DPF particulate filter or the modeled carbon loading reaches the calibrated threshold A, the compression ignition engine enters the regeneration mode. At this time, the ECU controller determines whether it has entered a high-altitude area based on the ambient air pressure detected by the air pressure sensor 7. When A1 ≤ A, the oxygen concentration in the exhaust gas is low and ignition is difficult, indicating that it is already in a high-altitude environment. If the detected ambient air pressure is lower than the set threshold, proceed to the next step of detection to check whether the engine operating mode is in the regeneration state. If it is in the regeneration state, open the air supply valve 4, and at the same time, turn on the fuel post-injection module for engine regeneration, and use the method of post-injection in the engine cylinder to inject excess fuel into the exhaust pipe. The DOC catalyst heats the post-injected HC (fuel) to raise the temperature in front of the DPF particulate filter to about 600 °C for regeneration. The modeled carbon loading is a modeled value calculated by the ECU based on the engine speed and fuel injection volume, and the calculation method is a method of the prior art.

[0026] During the regeneration process, the air supply valve is opened to inject excessive compressed air, so that the air and the fuel after the fuel supercharger of the post-injected fuel are fully mixed in the exhaust pipe, increasing the O2 content in the exhaust pipe to assist the DOC in oxidizing HC to achieve the purpose of cleaning the carbon deposits in the particulate filter. During the regeneration process, closed-loop diagnosis is performed according to the temperatures measured by the temperature sensors T1 and T2 before and after the DOC catalyst. If the regeneration temperature does not reach the target temperature, continue to supply air and control the air volume of the air supply device in real time. When it is detected that the regeneration is completed, close the air supply valve and stop supplying air, and the regeneration assistance is completed. At the same time, continue to monitor the air pressure and the engine operating mode and wait for the next regeneration.

[0027] The compression ignition engine, DOC catalyst, DPF particulate filter, temperature sensor, air pressure sensor, and fuel post-injection module described in the present invention are all common components in the prior art and do not require special improvement design. Only the regeneration strategy of the ECU controller needs to be developed and work with the existing components. The writing method of the program pulse spectrum diagram executed by the ECU controller is also a method of the prior art.

[0028] The present invention adopts a method of supplying air after the supercharger. By promoting the mixing of fuel and air, it increases the O2 content in the exhaust gas in the exhaust pipe, promotes better heating and ignition of the fuel in the DOC, can reduce the performance pressure of the DOC catalyst in the plateau environment, and reduce the regeneration failure rate of the vehicle in the plateau environment. When using the DPF particulate trap for regeneration, a control strategy and device for regeneration are adopted by supplying additional air in front of the DOC catalyst to increase the oxygen concentration in the exhaust gas. In specific implementation, a device for heating compressed air can be added.

[0029] Based on the characteristics of poor combustion due to low temperature and low oxygen in the plateau environment, the present invention is used to solve the difficulty of post-treatment regeneration of compression ignition engines, thereby improving the emission level of the engine in the plateau, reducing the plateau regeneration failure rate, protecting the plateau environment, and at the same time improving the adaptability of the engine and post-treatment in the plateau environment and increasing the success rate of plateau post-treatment regeneration.

Claims

1. A control strategy for vehicle aftertreatment regeneration in a plateau environment, characterized in that, Enable the following control strategies during regeneration in the plateau environment:

1. During the plateau calibration of the vehicle and the engine bench, collect the aftertreatment regeneration test data at different altitudes, analyze the regeneration differences of the aftertreatment at different altitudes, and obtain that the regeneration ability decreases at a certain altitude and the temperature cannot meet the regeneration requirements. The ambient atmospheric pressure corresponding to this altitude is A. Write the collected ambient atmospheric pressure A into the ECU controller and set it as the ambient pressure threshold. At the same time, set the real-time monitored ambient air pressure as A1, and compile and form the ECU controller execution program pulse spectrum diagram in combination with the test parameters A and A1; 2. After the plateau calibration, obtain the ambient atmospheric pressure A. Set that when the actual ambient air pressure A1 ≤ A, it is in the plateau environment during the control strategy writing. Add a gas supply pipeline in front of the DOC catalyst in the aftertreatment system. When the ECU controller detects that the compression ignition engine enters the active regeneration mode, start the program to detect the current ambient atmospheric pressure, and the detected value is A1. If A1 ≤ the set ambient threshold A, then the ECU controller controls the opening of the gas supply valve of the gas supply pipeline; 3. Gas supply device execution strategy: The ECU controller controls the opening of the gas supply valve of the gas supply device according to the developed strategy, and uses the temperature data fed back by the first temperature sensor T1 arranged at the inlet of the post-DOC catalyst and the second temperature sensor T2 arranged at the inlet of the DPF particulate trap to control the gas volume of the gas supply device in real time. When it is detected that the regeneration ends, the gas supply valve closes, and at the same time, continue to monitor the air pressure and the engine operation mode and wait for the next regeneration.

2. The control device for implementing the control strategy according to claim 1, characterized in that, The control device includes an ECU controller, a gas supply pipeline connected to the exhaust pipe of the vehicle compression ignition engine and located before the DOC catalyst in the aftertreatment system and its gas supply device. A gas supply valve controlled by the ECU controller is arranged on the gas supply pipeline. A first temperature sensor T1 and a second temperature sensor T2 connected to the ECU controller are respectively arranged at the inlet of the DOC catalyst and the inlet of the DPF particulate trap connected behind the DOC catalyst. The ECU controller is also connected with a pressure sensor.

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