Exhaust gas recirculation system, control method thereof, engine and vehicle

Abstract

The invention discloses an exhaust gas recirculation system and a control method thereof, an engine and a vehicle, and the method comprises the steps: obtaining the pressure of a first position based on the ambient atmospheric pressure and the pressure drop of an air filter; acquiring the temperature of the first position based on the temperature difference between the environment temperature and the air filter; acquiring the pressure of a second position based on the pressure of the first position and the flow characteristic of the air inlet flow control valve; acquiring the pressure of a third position based on the pressure of the second position; acquiring the pressure of the fourth position based on the ambient atmospheric pressure and the pressure drop of the waste gas treatment device; acquiring the pressure of a fifth position based on the pressure of the fourth position and the pressure drop of the waste gas cooler; based on the effective circulation sectional area of the exhaust gas flow control valve, the pressure of the third position, the pressure of the fifth position and the temperature of the fifth position, the flow of the exhaust gas flow control valve is obtained; the opening degree of the plurality of flow rate control valves is controlled based on the flow rate of the exhaust gas flow rate control valve. Thus, the cost problem caused by the use of a differential pressure sensor is reduced.

Description

Technical Field

[0001] The present application relates to the technical field of exhaust gas recirculation, and in particular to an exhaust gas recirculation system and a control method thereof, an engine, and a vehicle. Background Art

[0002] Exhaust Gas Recirculation (EGR) is an emission control technology used in internal combustion engines (such as automobile engines) to reduce the emission of harmful pollutants such as nitrogen oxides (NOx) generated during the combustion process. Its basic principle is to reintroduce part of the exhaust gas into the engine cylinder to reduce the combustion temperature (high temperature is the main cause of NOx generation). The implementation method is to mix the exhaust gas with fresh air and enter the cylinder to dilute the oxygen concentration and slow down the combustion speed, thereby reducing the formation of NOx under high temperature and high pressure conditions. The EGR system usually consists of an EGR valve, ECU, EGR cooler, sensor, and connecting pipes. Among them, the EGR valve is the core component for controlling the exhaust gas recirculation volume. The opening is adjusted by the ECU according to the working conditions. The EGR cooler is used to reduce the exhaust gas temperature, improve the dilution effect and reduce the risk of knocking. The sensor is used to monitor the pressure, temperature and other parameters of the connecting pipe to ensure the accurate mixing of exhaust gas and fresh air. Through EGR technology, the engine meets environmental regulations while taking into account performance and efficiency. It is an indispensable emission reduction solution for modern internal combustion engines.

[0003] During the actual operation of the engine, the ECU needs to control the EGR valve opening and EGR flow rate according to the engine speed and load information, and the EGR valve opening control depends on the pressure difference or pressure ratio input of the EGR valve. In the related art, a pressure difference sensor is usually set on the EGR valve to obtain the pressure difference or pressure ratio of the EGR valve. This method requires the installation of a pressure difference sensor, which is not conducive to reducing costs. Summary of the invention

[0004] In view of the above, it is necessary to provide an exhaust gas recirculation system and a control method thereof, an engine, and a vehicle, which can reduce the cost problem caused by using a differential pressure sensor.

[0005] The first aspect of the present application provides a control method for an exhaust gas recirculation system, wherein the exhaust gas recirculation system is connected to a combustion chamber of an engine, wherein an intake pipe is provided with an air filter and an intake flow control valve in sequence, an exhaust pipe is provided with an exhaust gas treatment device, and an exhaust gas circulation pipe is provided with an exhaust gas cooler and an exhaust gas flow control valve in sequence, the method comprising: obtaining the pressure and temperature at a first position based on the environment and state parameters of the air filter; obtaining the pressure at a second position and the pressure at a third position based on the pressure at the first position and the flow characteristics of the intake flow control valve; obtaining the pressure at a fourth position and the pressure at a fifth position based on the environment, the exhaust gas treatment device and the state parameters of the exhaust gas cooler; obtaining the flow of the exhaust gas flow control valve based on the effective flow cross-sectional area of ​​the exhaust gas flow control valve, the pressure at the third position and the state parameters of the fifth position; and controlling the opening of the intake flow control valve and the exhaust flow control valve based on the flow of the exhaust gas flow control valve.

[0006] In some embodiments, the first position is located between the air filter and the intake flow control valve and is close to the intake flow control valve, the second position is located between the intake flow control valve and the engine and is close to the intake flow control valve, the third position is located between the intake flow control valve and the exhaust flow control valve and is close to the exhaust flow control valve, the fourth position is located between the exhaust treatment device and the exhaust flow control valve and is close to the exhaust treatment device, and the fifth position is located between the exhaust flow control valve and the exhaust cooler and is close to the exhaust flow control valve.

[0007] In some embodiments, the pressure and temperature of the first position are obtained based on the state parameters of the environment and the air filter, including: obtaining the pressure of the first position based on the ambient atmospheric pressure and the pressure drop of the air filter; obtaining the temperature of the first position based on the ambient temperature and the temperature difference of the air filter.

[0008] In some embodiments, the pressure drop of the air filter is related to the air flow at the first location, and the pressure drop of the air filter is a function or a calibrated value based on the air flow.

[0009] In some embodiments, the temperature difference is related to the air flow rate and the water temperature of the engine, and the temperature difference is a function or a calibrated value based on the air flow rate and the water temperature of the engine.

[0010] In some embodiments, obtaining the pressure at the fourth location includes: obtaining the pressure at the fourth location based on the ambient atmospheric pressure and the pressure drop of the exhaust gas treatment device. Obtaining the pressure at the fifth location includes: obtaining the pressure at the fifth location based on the pressure at the fourth location and the pressure drop of the exhaust gas cooler.

[0011] In some embodiments, the flow characteristic is related to the current opening of the intake flow control valve and the standard gas flow, the flow characteristic is a function or a calibrated value based on the current opening of the intake flow control valve and the standard gas flow, the standard gas flow is related to the air flow, pressure and temperature at the first position, the standard gas flow is a function or a calibrated value based on the air flow, pressure and temperature at the first position.

[0012] In some embodiments, the pressure drop of the exhaust treatment device is related to the exhaust flow rate at the fourth location, and the pressure drop of the exhaust treatment device is a function or a calibrated value based on the exhaust flow rate at the fourth location.

[0013] In some embodiments, the pressure drop of the exhaust gas cooler is related to the exhaust gas flow rate at the fifth location, and the pressure drop of the exhaust gas cooler is a function or a calibrated value based on the exhaust gas flow rate at the fifth location.

[0014] In some embodiments, obtaining the pressure at the third position includes: if the pressure of the pipeline between the second position and the third position is less than or equal to a predetermined value, using the pressure at the second position as the pressure at the third position.

[0015] In some embodiments, obtaining the pressure at the third position includes: if the pressure of the pipeline between the second position and the third position is greater than a predetermined value, obtaining the pressure at the third position based on the pressure at the second position and the pipeline pressure drop between the second position and the third position; wherein the pipeline pressure drop is related to the exhaust gas flow rate at the third position, and the pipeline pressure drop is a function or a calibrated value based on the exhaust gas flow rate at the third position.

[0016] In some embodiments, the effective flow cross-sectional area of ​​the exhaust flow control valve is related to the current opening of the exhaust flow control valve, and the effective flow cross-sectional area of ​​the exhaust flow control valve is a function or a calibrated value based on the current opening of the exhaust flow control valve.

[0017] The present application also provides an exhaust gas recirculation system, including an electronic control unit, an intake pipe, an exhaust pipe and an exhaust gas circulation pipe, the intake pipe and the exhaust pipe are both connected to the combustion chamber of the engine, the exhaust gas circulation pipe connects the intake pipe and the exhaust pipe, the intake pipe is provided with an air filter and an intake flow control valve in sequence, the exhaust pipe is provided with an exhaust gas treatment device, the exhaust gas circulation pipe is provided with an exhaust gas cooler and an exhaust gas flow control valve in sequence, and the electronic control unit is configured to execute the control method of any embodiment of the present application to achieve exhaust gas circulation control.

[0018] The present application also provides an engine, comprising an exhaust gas recirculation system according to any embodiment of the present application, wherein the exhaust gas recirculation system executes a control method according to any embodiment of the present application to achieve exhaust gas circulation control.

[0019] The present application also provides a vehicle, comprising an engine according to any embodiment of the present application, wherein the engine implements exhaust gas circulation control of the engine through a control method according to any embodiment of the present application.

[0020] In the exhaust gas recirculation system and its control method, engine, and vehicle of the present application, the pressure or pressure ratio upstream and downstream of the exhaust gas flow control valve (i.e., the third position and the fifth position) is replaced by the pressure of multiple specific positions (i.e., the first position, the second position, and the fourth position) in the intake pipe and the exhaust pipe through a calculation model. Since the pressures of these multiple specific positions are in the intake pipe and the exhaust pipe, they can be easily obtained through sensor measurement or data test fitting. That is, the flow of the exhaust gas flow control valve can be obtained without using a differential pressure sensor, thereby reducing the cost problem caused by using a differential pressure sensor on the exhaust gas flow control valve. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic diagram of the structure of the exhaust gas recirculation system of an embodiment of the present application.

[0022] Figure 2 4 is a flow chart of a method for controlling an exhaust gas recirculation system according to an embodiment of the present application.

[0023] Figure 3 This is an embodiment of the present application P’ C Schematic diagram of the deviation results of the pressure model calculation.

[0024] Figure 4 This is an embodiment of the present application P’ D Schematic diagram of the deviation results of the pressure model calculation.

[0025] Figure 5 It is a schematic diagram of the exhaust gas flow accuracy result of the exhaust gas flow control valve calculated based on the model according to an embodiment of the present application.

[0026] Main component symbols 100. Engine; 200. Electronic control unit; 300. Intake pipe; 400. Exhaust pipe; 500. Exhaust gas circulation pipe; 1. Air filter; 2. First intake flow control valve; 3. Exhaust flow control valve; 4. Temperature sensor; 5. Exhaust gas cooler; 6. Exhaust gas treatment device; 7. Air supercharger; 8. Air cooler; 9. Second intake flow control valve; 10. Exhaust turbine; A. First position; B. Second position; C. Third position; D. Fifth position; E. Fourth position.

[0027] The following specific implementation mode will further illustrate the present application in conjunction with the above-mentioned drawings. DETAILED DESCRIPTION In the description of the embodiments of the present application, words such as "exemplary", "or", "for example" and the like are used to indicate examples, illustrations or descriptions. Any embodiment or design described as "exemplary" or "for example" in the embodiments of the present application should not be interpreted as being more preferred or more advantageous than other embodiments or designs. Specifically, the use of words such as "exemplary", "or", "for example" and the like is intended to present related concepts in a specific mode.

[0029] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by technicians in the technical field in this application. The terms used in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application. It should be understood that, unless otherwise specified in this application, " / " means or. For example, A / B can represent A or B. "And / or" in this application is only a description of the association relationship of associated objects, indicating that three relationships can exist. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. "At least one" means one or more. "Multiple" means two or more than two. For example, at least one of a, b or c can represent: a, b, c, a and b, a and c, b and c, a, b and c seven situations.

[0030] It should also be noted that the terms "first" and "second" in the specification, claims and drawings of this application are used to distinguish similar objects, rather than to describe a specific order or sequence. The method disclosed in the embodiments of this application or the method shown in the flowchart includes one or more steps for implementing the method. Without departing from the scope of the claims, the execution order of multiple steps can be interchanged with each other, and some steps can also be deleted.

[0031] Exhaust Gas Recirculation (EGR) is an emission control technology used in internal combustion engines (such as automobile engines) to reduce the emission of harmful pollutants such as nitrogen oxides (NOx) generated during the combustion process. Its basic principle is to reintroduce part of the exhaust gas into the engine cylinder to reduce the combustion temperature (high temperature is the main cause of NOx generation). This is achieved by mixing the exhaust gas with fresh air before entering the cylinder, diluting the oxygen concentration and slowing down the combustion rate, thereby reducing the formation of NOx under high temperature and high pressure conditions.

[0032] EGR technology is an important means for spark-ignition engines to reduce fuel consumption. It has been widely used in new energy hybrid engines. In new energy hybrid engines, the EGR system usually consists of an EGR valve, an engine control unit (ECU), an EGR cooler, sensors, and connecting pipes. Among them, the EGR valve is the core component for controlling the exhaust gas recirculation volume. The ECU adjusts the opening according to the working conditions. The EGR cooler is used to reduce the exhaust gas temperature, improve the dilution effect and reduce the risk of knocking. The sensor is used to monitor the pressure, temperature and other parameters of the connecting pipe to ensure the accurate mixing of exhaust gas and fresh air. The main types of EGR include high-pressure and low-pressure. High-pressure EGR refers to direct air intake from the exhaust manifold, which is suitable for low-speed conditions (common in traditional gasoline engines). Low-pressure EGR refers to air intake from the downstream of the turbocharger, which is introduced into the intake system after cooling. It is mostly used in diesel engines or supercharged engines, with higher efficiency and better compatibility. Through EGR technology, the engine meets environmental regulations while taking into account performance and efficiency. It is an indispensable emission reduction solution for modern internal combustion engines.

[0033] However, in the actual operation of the engine, the electronic control unit (ECU) plays a vital role in optimizing the engine's combustion efficiency and emission performance by precisely controlling the opening of the exhaust gas recirculation (EGR) valve and the EGR flow rate. The main function of the EGR system is to reintroduce part of the exhaust gas into the engine's intake system to reduce the temperature in the combustion chamber and the emission of nitrogen oxides (NOx). To achieve this goal, the ECU needs to monitor the engine's speed and load information in real time and dynamically adjust the opening of the EGR valve based on these data. The EGR valve opening control relies on the pressure difference or pressure ratio input of the EGR valve. The pressure difference refers to the pressure difference on both sides of the EGR valve, while the pressure ratio refers to the pressure ratio between the upstream and downstream of the EGR valve. These parameters are crucial for precise control of the EGR flow rate because they directly affect the effect of exhaust gas recirculation. In traditional technical solutions, a pressure difference sensor is usually set on the EGR valve to monitor the pressure difference or pressure ratio of the EGR valve in real time. The advantage of this method is that it can provide high-precision pressure difference or pressure ratio data, thereby ensuring precise control of the EGR system.

[0034] However, the installation of differential pressure sensors also brings some problems. First, the cost of differential pressure sensors is high, which increases the manufacturing cost of the entire engine control system. Second, the installation and maintenance of differential pressure sensors are also more complicated, requiring additional space and wiring, which may increase the complexity and failure rate of the engine. In addition, differential pressure sensors may be contaminated or damaged in harsh working environments, which will affect their measurement accuracy and reliability.

[0035] To this end, the embodiments of the present application provide an exhaust gas recirculation system and a control method thereof, an engine, and a vehicle, which can reduce the cost problem caused by the use of a differential pressure sensor, that is, while achieving precise control of the EGR valve, it can reduce the reliance on the differential pressure sensor, improve the performance and reliability of the engine, and reduce the manufacturing cost and maintenance cost. Some embodiments will be described below in conjunction with the accompanying drawings. In the absence of conflict, the following embodiments and features in the embodiments can be combined with each other.

[0036] Figure 1 It is a schematic diagram of the structure of the exhaust gas recirculation system of an embodiment of the present application.

[0037] like Figure 1 As shown, the embodiment of the present application first provides an exhaust gas recirculation system, which can include an electronic control unit 200, an intake pipe 300, an exhaust pipe 400, and an exhaust gas circulation pipe 500. The intake pipe 300 and the exhaust pipe 400 are both connected to the engine 100, and the exhaust gas circulation pipe 500 is connected to the intake pipe 300 and the exhaust pipe 400.

[0038] In the present application embodiment, Figure 1 As shown, the intake pipeline 300 is sequentially provided with an air filter 1 and an intake flow control valve, which are referred to as "the first intake flow control valve 2" for the sake of distinction. The exhaust pipeline 400 is provided with an exhaust gas treatment device 6, and the exhaust gas circulation pipeline 500 is sequentially provided with an exhaust gas cooler 5 and an exhaust gas flow control valve 3. Specifically, the intake side of the air filter 1 is ambient air, the outlet side of the air filter 1 is connected to the intake side of the first intake flow control valve 2, the outlet side of the first intake flow control valve 2 is connected to the intake side of the combustion chamber of the engine 100, the outlet side of the combustion chamber of the engine 100 is connected to the intake side of at least one exhaust gas treatment device 6, and the outlet side of the exhaust gas treatment device 6 and the connected pipeline is connected to the ambient air. In the exhaust gas circulation pipeline 500, the intake side is connected between, before or after the multiple exhaust gas treatment devices 6 of the exhaust pipeline 400, and the exhaust gas cooler 5 and the exhaust gas flow control valve 3 are sequentially arranged in the exhaust gas circulation pipeline 500 along the direction of gas flow. After the exhaust gas flow control valve 3, that is, the exhaust gas outlet side of the exhaust gas circulation pipeline 500, the exhaust gas outlet side is connected between the exhaust gas outlet side of the first intake flow control valve 2 and the intake side of the combustion chamber of the engine 100. Among them, "sequentially arranged" means arranged along the direction of gas flow, such as Figure 1 The arrows in the pipeline indicate the direction of gas flow.

[0039] In some embodiments, Figure 1As shown, the intake pipeline 300 may also include an air supercharger 7, an air cooler 8, and a second intake flow control valve 9 which are arranged in sequence. Specifically, from the intake side of the intake pipeline 300 to the combustion chamber of the engine 100, an air filter 1, a first intake flow control valve 2, an air supercharger 7, an air cooler 8, and a second intake flow control valve 9 are arranged in sequence. In this embodiment, the outlet side is connected between the first intake flow control valve 2 and the supercharger.

[0040] In some embodiments, Figure 1 As shown, the exhaust line 400 may further include an exhaust gas turbine 10, which is disposed on the exhaust side of the combustion chamber of the engine 100. Specifically, the intake side of the exhaust gas turbine 10 is connected to the exhaust side of the combustion chamber of the engine 100, and the exhaust side of the exhaust gas turbine 10 is connected to the intake side of the exhaust gas treatment device 6.

[0041] In some embodiments, a plurality of exhaust treatment devices 6 may be connected in sequence.

[0042] In some embodiments, the air charger 7 is connected to the exhaust gas turbine 10 .

[0043] In the embodiments of the present application, Figure 1 As shown, the electronic control unit 200, also called the engine 100 control unit (i.e., ECU), can be used to control the air filter 1, the air supercharger 7, the air cooler 8, the engine 100, the exhaust gas turbine 10, the exhaust gas treatment device 6, and the exhaust gas cooler 5, etc., and can also be used to read the current opening of the first intake flow control valve 2, the second intake flow control valve 9, and the exhaust flow control valve 3 and control the opening of the first intake flow control valve 2, the second intake flow control valve 9, and the exhaust flow control valve 3.

[0044] In some embodiments, the exhaust gas recirculation system may further include multiple sensors, such as pressure sensors disposed in the intake pipe 300 and the exhaust pipe 400, or a temperature sensor 4 (such as a temperature sensor 400 disposed in the exhaust pipe) Figure 1 The electronic control unit 200 can be used to read the data of the sensor and control the air filter 1, the air supercharger 7, the air cooler 8, the engine 100, the exhaust gas turbine 10, the exhaust gas treatment device 6 and the exhaust gas cooler 5 based on the data, or control the opening of the first intake flow control valve 2, the second intake flow control valve 9 and the exhaust flow control valve 3.

[0045] In addition, the electronic control unit 200 can also be configured to execute the control method of the exhaust gas recirculation system of any embodiment of the present application. As follows, the embodiment of the present application also provides a control method of the exhaust gas recirculation system.

[0046] Figure 24 is a flow chart of a method for controlling an exhaust gas recirculation system according to an embodiment of the present application.

[0047] like Figure 2 As shown, the control method of the exhaust gas recirculation system of the embodiment of the present application may include: Step S100: obtaining the pressure at the first position based on the ambient atmospheric pressure and the pressure drop of the air filter.

[0048] The position between the air filter and the intake flow control valve and close to the intake flow control valve is defined as the first position (i.e. Figure 1 In other words, along the flow direction of the gas, the first position is the intake side of the intake flow control valve.

[0049] The ambient atmospheric pressure is a state parameter of the environment, and the pressure drop of the air filter is a state parameter of the air filter. In some embodiments, the state parameter of the environment or the air filter may also include at least one of pressure, temperature, compression or temperature difference.

[0050] In some embodiments, the pressure drop of the air filter is related to the air flow at the first location, and the pressure drop of the air filter is a function or a calibrated value based on the air flow.

[0051] In the embodiment of the present application, the pressure at the first position can be expressed by the formula: (1) Obtained. In formula (1), P A That is, the pressure at the first position, P Amb That is, the ambient atmospheric pressure, △ P AairF As mentioned above, the pressure drop of the air filter is a function or calibration value based on the air flow rate, which can be expressed as f ( m air ) indicates that, m air That is, air flow.

[0052] In some embodiments, the ECU can obtain the air flow rate by measuring the intake air flow sensor or calculating the air flow rate through a model. m air . Air filter pressure drop f ( m air ) can be obtained by obtaining multiple air flow m airThe experimental data is obtained by fitting, and the fitting method may include but is not limited to at least one of a linear method, a nonlinear method, a regularization method, a machine learning method, a probability method, a time series method and a non-parametric method.

[0053] In some embodiments, multiple parameters can be added, such as environmental parameters (temperature, atmospheric pressure or humidity, etc.), other state parameters of the air filter (pollution degree, blockage rate or filter element characteristics, etc.), flow characteristic parameters (air density or Reynolds number), system design parameters (pipeline shape, filter material resistance coefficient) and dynamic operating parameters (transient flow rate change rate), etc., to affect the pressure drop of the air filter. f ( m air ) to make corrections. This can improve the pressure drop of the air filter f ( m air ) calculation accuracy.

[0054] like Figure 2 As shown, the control method of the exhaust gas recirculation system of the embodiment of the present application may also include: Step S200: Acquire the temperature of the first position based on the temperature difference between the ambient temperature and the air filter.

[0055] The temperature at the first position refers to the air temperature at the first position.

[0056] In some embodiments, the temperature difference is related to the air flow rate and the water temperature of the engine, and the temperature difference is a function or a calibrated value based on the air flow rate and the water temperature of the engine. Specifically, the air temperature at the first position is the temperature of the atmosphere after passing through the air filter. Since the air filter is located in the engine compartment, its temperature is affected by the air flow rate. m air , Engine water temperature T CEng Therefore, the air temperature at the first position can be calculated by the formula: (2) Obtain. In formula (2), T A The air temperature at the first location, T Amb is the ambient temperature (i.e., atmospheric temperature), △ T AirF is the temperature difference of the air filter. As mentioned above, △ T AirF It is a function or calibration value based on air flow and engine water temperature. f ( m air , T CEng)express.

[0057] Likewise, in some embodiments, the temperature difference of the air filter f ( m air , T CEng ) can be obtained by obtaining multiple air flow m air and engine water temperature T CEng The experimental data is obtained by fitting, and the fitting method may include but is not limited to at least one of a linear method, a nonlinear method, a regularization method, a machine learning method, a probability method, a time series method and a non-parametric method.

[0058] Similarly, in some embodiments, multiple parameters can be added, such as environmental parameters (temperature, atmospheric pressure or humidity, etc.), other state parameters of the air filter (pollution degree, blockage rate or filter element characteristics, etc.), flow characteristic parameters (air density or Reynolds number), system design parameters (pipeline shape, filter material resistance coefficient) and dynamic operating parameters (transient flow rate change rate), etc., to affect the temperature difference of the air filter. f ( m air , T CEng ) to make corrections. This can improve the temperature difference of the air filter f ( m air , T CEng ) calculation accuracy.

[0059] like Figure 2 As shown, the control method of the exhaust gas recirculation system of the embodiment of the present application may also include: Step S300: Based on the pressure at the first position and the flow characteristics of the intake flow control valve, the pressure at the second position is obtained.

[0060] The position between the intake flow control valve and the engine and close to the intake flow control valve is defined as the second position (i.e. Figure 1 In other words, along the flow direction of the gas, the second position is the outlet side of the intake flow control valve.

[0061] It can be understood that the pressure at the second position is the product of the pressure at the first position and the pressure ratio before and after the intake flow control valve, that is, P B = P A · P B / P A ,in,P A is the pressure at the first position, P B is the pressure at the second position, P B / P A The pressure ratio before and after the intake flow control valve. P B / P A It can be calculated through the flow characteristics of the intake flow control valve, so the pressure ratio before and after the intake flow control valve is P B / P A Can be used f ( wr k1 ，m c,air ) indicates that, wr k1 is the current opening of the intake flow control valve, m c,air is the corrected standard gas flow. In other words, the flow characteristic is related to the current opening of the intake flow control valve and the standard gas flow, and the flow characteristic is a function or calibration value based on the current opening of the intake flow control valve and the standard gas flow. f ( wr k1 ，m c,air ).

[0062] In some embodiments, the standard gas flow is related to the air flow, pressure and temperature at the first location, and the standard gas flow is a function or a calibrated value based on the air flow, pressure and temperature at the first location. The standard gas flow can be expressed by: (3) Obtained. In formula (3), f ( P A )and f ( T A ) are functions or calibration values ​​for correcting the gas to the standard state (pressure and temperature). Correcting the gas to the standard state (pressure and temperature) means correcting the state of the first position with reference to the standard environment. For example, if the temperature of the first position is high, the gas density at the first position will be lower than that of the atmosphere, and the air entering will be reduced (i.e., regardless of the pressure difference, when the temperature at the first position is high and the density is low, the gas flow at the first position is small), or the pressure at the first position is low, the density is low, and the flow is small.

[0063] Likewise, f ( wrk1 ，m c,air ) can be obtained by obtaining multiple air flow m air The test data of the current opening of the intake flow control valve is obtained by fitting, and the fitting method may include but is not limited to at least one of a linear method, a nonlinear method, a regularization method, a machine learning method, a probability method, a time series method and a non-parametric method.

[0064] Similarly, in some embodiments, multiple parameters may be added, such as environmental parameters (temperature, atmospheric pressure or humidity, etc.), other state parameters of the air filter (pollution degree, blockage rate or filter element characteristics, etc.), flow characteristic parameters (air density or Reynolds number), system design parameters (pipeline shape, filter material resistance coefficient) and dynamic operating parameters (transient flow rate change rate), etc. f ( wr k1 ，m c,air ) to make corrections. This can improve f ( wr k1 ，m c,air ) calculation accuracy.

[0065] like Figure 2 As shown, the control method of the exhaust gas recirculation system of the embodiment of the present application may also include: Step S400: Based on the pressure at the second position, obtain the pressure at the third position.

[0066] The position between the intake flow control valve and the exhaust flow control valve and close to the exhaust flow control valve is defined as the third position (i.e. Figure 1 In other words, along the flow direction of the gas, the third position is the outlet side of the exhaust gas flow control valve.

[0067] In some embodiments, if the pipeline distance between the second position and the third position is less than or equal to a predetermined value, for example, the pipeline distance between the second position and the third position is small, and the pressure loss of the pipeline is small, then the pressure at the second position can be used as the pressure at the third position, that is, expressed as P ' C = P B ,in, P ' C is the pressure at the third position, P B is the pressure at the second position.

[0068] In some embodiments, if the pressure drop of the pipeline between the second position and the third position is greater than a predetermined value, the pressure drop of the pipeline is large. At this time, the pressure of the third position can be obtained based on the pressure of the second position and the pressure drop of the pipeline between the second position and the third position. The pressure drop of the pipeline between the second position and the third position is related to the exhaust gas flow rate at the third position, and the pipeline pressure drop is a function or a calibrated value based on the exhaust gas flow rate at the third position. f1 ( m EGR ), where m EGR is the exhaust gas flow at the third position. The pressure at the third position can be expressed by: (4) In formula (4), △ P BC That is, the pipeline pressure drop between the second position and the third position.

[0069] Likewise, f1 ( m EGR ) can be obtained by obtaining the exhaust gas flow at multiple third locations m EGR The experimental data is obtained by fitting, and the fitting method may include but is not limited to at least one of a linear method, a nonlinear method, a regularization method, a machine learning method, a probability method, a time series method and a non-parametric method.

[0070] Similarly, in some embodiments, multiple parameters may be added, such as system design parameters (pipeline shape, filter material resistance coefficient) and dynamic operating parameters (transient flow rate change rate), etc. f1 ( m EGR ) to make corrections. This can improve f1 ( m EGR ) calculation accuracy.

[0071] Figure 3 This is an embodiment of the present application P’ C Schematic diagram of the deviation results of the pressure model calculation. The X-axis is the deviation value between the measured pressure and the model calculated pressure, and the Y-axis is the number of test measurement points within the deviation range. Figure 4 and Figure 5 Same as this, no further elaboration is required.

[0072] like Figure 3 As shown, P_EGRV_OUT is the embodiment of the present application. P’ C , the model value P’ C Compared with the actual measured valueP C (i.e. the pressure value actually measured by the sensor) for comparison. RMSE is the root mean square error, R2 is the coefficient of determination, and a coefficient of determination of 0.99 or above indicates that the model value P’ C Has very high prediction accuracy and can replace actual measured values P C .

[0073] like Figure 2 As shown, the control method of the exhaust gas recirculation system of the embodiment of the present application may also include: Step S500: obtaining the pressure at the fourth position based on the ambient atmospheric pressure and the pressure drop of the exhaust gas treatment device.

[0074] The fourth position (i.e. Figure 1 In other words, along the flow direction of the gas, the fourth position is the outlet side of the first exhaust gas treatment device connected after the engine combustion chamber.

[0075] The ambient atmospheric pressure is a state parameter of the environment, and the pressure drop of the exhaust gas treatment device is a state parameter of the exhaust gas treatment device. In some embodiments, the state parameter of the environment or the exhaust gas treatment device may also include at least one of pressure, temperature, compression or temperature difference.

[0076] It can be understood that since the fourth position is separated from the ambient atmosphere by the exhaust gas treatment device, the pressure at the fourth position can be expressed by the formula: (5) Obtained. In formula (5), P E That is, the pressure at the fourth position, P Amb is the ambient atmospheric pressure, △ P Exh is the pressure drop of the exhaust gas treatment device.

[0077] In some embodiments, the pressure drop of the exhaust treatment device is related to the exhaust flow rate at the fourth location, and the pressure drop of the exhaust treatment device is a function or a calibrated value based on the exhaust flow rate at the fourth location. f ( m exh ),in, m exh is the exhaust gas flow rate at the fourth position.

[0078] Likewise, f ( m exh ) can be obtained by obtaining the exhaust gas flow at multiple fourth locationsm exh The experimental data is obtained by fitting, and the fitting method may include but is not limited to at least one of a linear method, a nonlinear method, a regularization method, a machine learning method, a probability method, a time series method and a non-parametric method.

[0079] Similarly, in some embodiments, multiple parameters may be added, such as system design parameters (pipeline shape, filter material resistance coefficient) and dynamic operating parameters (transient flow rate change rate), etc. f ( m exh ) to make corrections. This can improve f ( m exh ) calculation accuracy.

[0080] like Figure 2 As shown, the control method of the exhaust gas recirculation system of the embodiment of the present application may also include: Step S600: Based on the pressure at the fourth position and the pressure drop of the exhaust gas cooler, the pressure at the fifth position is obtained.

[0081] The position between the exhaust gas flow control valve and the exhaust gas cooler and close to the exhaust gas flow control valve is defined as the fifth position (i.e. Figure 1 In other words, along the flow direction of the gas, the fifth position is the intake side of the exhaust gas flow control valve.

[0082] Likewise, the pressure drop of the exhaust gas cooler is a state parameter of the exhaust gas cooler. In some embodiments, the state parameter of the exhaust gas cooler may also include at least one of pressure, temperature, compression or temperature difference.

[0083] It can be understood that the pressure at the fifth position is the pressure after passing through the fourth position and the exhaust gas cooler, so the pressure at the fifth position can be expressed by the formula: (6) Obtained. In formula (6), P’ D That is, the pressure at the fifth position, △ P EGRCooler is the pressure drop of the exhaust gas cooler.

[0084] In some embodiments, the pressure drop of the exhaust gas cooler is related to the exhaust gas flow rate at the fifth position, and the pressure drop of the exhaust gas cooler is a function or a calibrated value based on the exhaust gas flow rate at the fifth position. f2 ( m EGR ), where m EGR is the exhaust gas flow rate at the fifth position.

[0085] Likewise, f2 ( m EGR ) can be obtained by obtaining the exhaust gas flow at multiple fifth positions m EGR The experimental data is obtained by fitting, and the fitting method may include but is not limited to at least one of a linear method, a nonlinear method, a regularization method, a machine learning method, a probability method, a time series method and a non-parametric method.

[0086] Similarly, in some embodiments, multiple parameters can be added, such as loop system design parameters (pipeline shape, filter material resistance coefficient) and dynamic operating parameters (transient flow rate change rate), etc. f2 ( m EGR ) to make corrections. This can improve f2 ( m EGR ) calculation accuracy.

[0087] Figure 4 This is an embodiment of the present application P’ D Schematic diagram of the deviation results of the pressure model calculation.

[0088] Likewise, if Figure 4 As shown, P_EGRV_IN is the embodiment of the present application. P’ D , the model value P’ D Compared with the actual measured value P D (i.e. the pressure value actually measured by the sensor) for comparison. RMSE is the root mean square error, R2 is the coefficient of determination, and a coefficient of determination of 0.99 or above indicates that the model value P’ D Has very high prediction accuracy and can replace actual measured values P D .

[0089] like Figure 2 As shown, the control method of the exhaust gas recirculation system of the embodiment of the present application may also include: Step S700: acquiring the flow rate of the exhaust gas flow rate control valve based on the effective flow cross-sectional area of ​​the exhaust gas flow rate control valve, the pressure at the third position, the pressure at the fifth position, and the temperature at the fifth position.

[0090] In some embodiments, the effective flow cross-sectional area of ​​the exhaust flow control valve is related to the current opening of the exhaust flow control valve, and the effective flow cross-sectional area of ​​the exhaust flow control valve is a function or a calibrated value based on the current opening of the exhaust flow control valve.

[0091] By combining the principles of gas dynamics and actual calibration parameters, the EGR flow rate can be quickly estimated (the exhaust gas flow control valve is essentially a throttling device, and its flow formula is based on the isentropic flow model or Fanno flow model in gas dynamics. When the exhaust gas passes through the exhaust gas flow control valve, the flow rate and pressure will change due to the change in the cross-sectional area of ​​the valve port, and the mass flow rate depends on the upstream and downstream pressure ratio and the valve opening). The formula for quickly estimating the EGR flow rate is: (7) In formula (7), m EGR That is, the exhaust gas flow rate of the exhaust gas flow control valve, A eff is the effective flow cross-sectional area of ​​the exhaust gas flow control valve, as mentioned above, A eff Based on the current opening of the exhaust gas flow control valve wrk2 Function or calibration value of f ( wrk2 ), T D is the gas temperature at the fifth position, R is the standard gas constant, φ Function is the pressure ratio correction function, φ The function can be used to correct the effect of the actual pressure ratio on the flow rate.

[0092] Likewise, f ( wrk2 ) can obtain the current opening of multiple exhaust gas flow control valves wrk2 The experimental data is obtained by fitting, and the fitting method may include but is not limited to at least one of a linear method, a nonlinear method, a regularization method, a machine learning method, a probability method, a time series method and a non-parametric method.

[0093] Similarly, in some embodiments, multiple parameters may be added, such as flow characteristic parameters (air density or Reynolds number), system design parameters (pipeline shape, filter material resistance coefficient), and dynamic operating parameters (transient flow rate change rate), etc. f ( wrk2 ) to make corrections. This can improve f ( wrk2 ) calculation accuracy.

[0094] In the embodiments of the present application, f ( wrk2 ) can also be corrected by the engine speed or load. This can increase the effective flow cross-sectional area of ​​the exhaust gas flow control valve A eff The calculation accuracy of .

[0095] Figure 5 It is a schematic diagram of the exhaust gas flow accuracy result of the exhaust gas flow control valve calculated based on the model according to an embodiment of the present application.

[0096] Likewise, if Figure 5 As shown, msagr is the embodiment of the present application m EGR , the model value m EGR Compare with the actual measured value (i.e. the pressure value actually measured by the sensor). RMSE is the root mean square error, R2 is the determination coefficient, and a determination coefficient of 0.98 or above can meet engineering requirements.

[0097] like Figure 2 As shown, the control method of the exhaust gas recirculation system of the embodiment of the present application may also include: Step S800: Based on the flow rate of the exhaust gas flow control valve, control the opening of the intake flow control valve and the opening of the exhaust gas flow control valve.

[0098] Thereby, closed-loop control of the exhaust gas flow control valve is achieved.

[0099] In addition, an embodiment of the present application further provides an engine, comprising an exhaust gas recirculation system according to any embodiment of the present application, wherein the exhaust gas recirculation system executes a control method according to any embodiment of the present application to achieve exhaust gas circulation control.

[0100] In addition, an embodiment of the present application further provides a vehicle, comprising an engine according to any embodiment of the present application, wherein the engine implements exhaust gas circulation control of the engine through a control method according to any embodiment of the present application.

[0101] In the exhaust gas recirculation system and its control method, engine, and vehicle of the present application, the pressure or pressure ratio upstream and downstream of the exhaust gas flow control valve (i.e., the third position and the fifth position) is replaced by the pressure of multiple specific positions (i.e., the first position, the second position, and the fourth position) in the intake pipe and the exhaust pipe through a calculation model. Since the pressures of these multiple specific positions are in the intake pipe and the exhaust pipe, they can be easily obtained through sensor measurement or data test fitting. That is, the flow of the exhaust gas flow control valve can be obtained without using a differential pressure sensor, thereby reducing the cost problem caused by using a differential pressure sensor on the exhaust gas flow control valve.

[0102] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present application and are not intended to limit it. Although the present application has been described in detail with reference to the preferred embodiments, a person of ordinary skill in the art should understand that the technical solution of the present application may be modified or replaced by equivalents without departing from the spirit and scope of the technical solution of the present application.

Claims

1. A control method for an exhaust gas recirculation system, wherein the exhaust gas recirculation system is connected to a combustion chamber of an engine, wherein an air filter and an intake flow control valve are sequentially arranged in an intake pipe, an exhaust gas treatment device is arranged in an exhaust pipe, and an exhaust gas cooler and an exhaust gas flow control valve are sequentially arranged in an exhaust gas circulation pipe, characterized in that: The method comprises: Based on the environment and the state parameters of the air filter, obtaining the pressure and temperature of the first position; Based on the pressure at the first position and the flow characteristics of the intake flow control valve, obtaining the pressure at the second position and the pressure at the third position; Based on the state parameters of the environment, the exhaust gas treatment device, and the exhaust gas cooler, obtaining the pressure at the fourth position and the pressure at the fifth position; acquiring the flow rate of the exhaust gas flow control valve based on the effective flow cross-sectional area of ​​the exhaust gas flow control valve, the pressure at the third position, and the state parameter at the fifth position; Based on the flow rate of the exhaust gas flow rate control valve, the openings of the intake air flow rate control valve and the exhaust gas flow rate control valve are controlled.

2. The exhaust gas recirculation system control method according to claim 1, characterized in that: The first position is located between the air filter and the intake flow control valve and is close to the intake flow control valve, the second position is located between the intake flow control valve and the engine and is close to the intake flow control valve, the third position is located between the intake flow control valve and the exhaust flow control valve and is close to the exhaust flow control valve, the fourth position is located between the exhaust treatment device and the exhaust flow control valve and is close to the exhaust treatment device, and the fifth position is located between the exhaust flow control valve and the exhaust cooler and is close to the exhaust flow control valve.

3. The exhaust gas recirculation system control method according to claim 1, characterized in that: The obtaining of the pressure and temperature of the first position based on the environment and the state parameters of the air filter comprises: obtaining a pressure at a first location based on an ambient atmospheric pressure and a pressure drop of the air filter; The temperature of the first position is acquired based on the difference between the ambient temperature and the temperature of the air filter.

4. The exhaust gas recirculation system control method according to claim 3, characterized in that: The pressure drop of the air filter is related to the air flow rate at the first position, and the pressure drop of the air filter is a function or a calibrated value based on the air flow rate.

5. The exhaust gas recirculation system control method according to claim 3, characterized in that: The temperature difference is related to the air flow rate and the water temperature of the engine, and the temperature difference is a function or a calibrated value based on the air flow rate and the water temperature of the engine.

6. The exhaust gas recirculation system control method according to claim 1, characterized in that: The obtaining of the pressure at the fourth position includes: obtaining the pressure at the fourth location based on the ambient atmospheric pressure and the pressure drop of the exhaust gas treatment device; The obtaining of the pressure at the fifth position includes: The pressure at the fifth location is acquired based on the pressure at the fourth location and the pressure drop of the exhaust gas cooler.

7. The exhaust gas recirculation system control method according to claim 1, characterized in that: The flow characteristic is related to the current opening of the intake flow control valve and the standard gas flow. The flow characteristic is a function or a calibrated value based on the current opening of the intake flow control valve and the standard gas flow. The standard gas flow is related to the air flow, pressure and temperature at the first position. The standard gas flow is a function or a calibrated value based on the air flow, pressure and temperature at the first position.

8. The exhaust gas recirculation system control method according to claim 1, characterized in that: The pressure drop of the exhaust gas treatment device is related to the exhaust gas flow rate at the fourth location, and the pressure drop of the exhaust gas treatment device is a function or a calibrated value based on the exhaust gas flow rate at the fourth location.

9. The exhaust gas recirculation system control method according to claim 1, characterized in that: The pressure drop of the exhaust gas cooler is related to the exhaust gas flow rate at the fifth position, and the pressure drop of the exhaust gas cooler is a function or a calibrated value based on the exhaust gas flow rate at the fifth position.

10. The exhaust gas recirculation system control method according to claim 1, characterized in that: Acquiring the pressure at the third position includes: If the pressure of the pipeline between the second position and the third position is less than or equal to a predetermined value, the pressure of the second position is used as the pressure of the third position.

11. The exhaust gas recirculation system control method according to claim 10, characterized in that: Acquiring the pressure at the third position includes: If the pressure of the pipeline between the second position and the third position is greater than the predetermined value, the pressure of the third position is obtained based on the pressure of the second position and the pressure drop of the pipeline between the second position and the third position; The pipeline pressure drop is related to the exhaust gas flow rate at the third position, and the pipeline pressure drop is a function or a calibrated value based on the exhaust gas flow rate at the third position.

12. The exhaust gas recirculation system control method according to claim 1, characterized in that: The effective flow cross-sectional area of ​​the exhaust gas flow control valve is related to the current opening of the exhaust gas flow control valve, and the effective flow cross-sectional area of ​​the exhaust gas flow control valve is a function or a calibrated value based on the current opening of the exhaust gas flow control valve.

13. An exhaust gas recirculation system, characterized in that: It includes an electronic control unit, an intake pipe, an exhaust pipe and an exhaust gas circulation pipe, the intake pipe and the exhaust pipe are both connected to the combustion chamber of the engine, the exhaust gas circulation pipe connects the intake pipe and the exhaust pipe, the intake pipe is provided with an air filter and an intake flow control valve in sequence, the exhaust pipe is provided with an exhaust gas treatment device, the exhaust gas circulation pipe is provided with an exhaust gas cooler and an exhaust gas flow control valve in sequence, and the electronic control unit is configured to execute the control method as described in any one of claims 1 to 12 to achieve exhaust gas circulation control.

14. An engine, characterized in that: It comprises the exhaust gas recirculation system as claimed in claim 13, wherein the exhaust gas recirculation system executes the control method as claimed in any one of claims 1 to 12 to achieve exhaust gas circulation control.

15. A vehicle, characterized in that: It comprises the engine as claimed in claim 14, wherein the exhaust gas circulation control of the engine is realized by the control method as claimed in any one of claims 1 to 12.

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