Exhaust gas recirculation system and method of controlling the same, engine, vehicle

Abstract

A kind of exhaust gas recirculation system and its control method, engine, vehicle, method includes: based on ambient atmospheric pressure and the pressure drop of air cleaner, obtain the pressure of first position;Based on ambient temperature and the temperature difference of air cleaner, obtain the temperature of first position;Based on the pressure of first position, the flow characteristic of intake air flow control valve, obtain the pressure of second position;Based on the pressure of second position, obtain the pressure of third position;Based on ambient atmospheric pressure and the pressure drop of exhaust gas treatment device, obtain the pressure of fourth position;Based on the pressure of fourth position and the pressure drop of exhaust gas cooler, obtain the pressure of fifth position;Based on the effective flow-through cross-sectional area of exhaust gas flow control valve, the pressure of third position, the pressure of fifth position and the temperature of fifth position, obtain the flow of exhaust gas flow control valve;Based on the flow of exhaust gas flow control valve, control the opening of multiple flow control valves.It is thus reduced the cost problem caused by using pressure difference sensor.

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 emissions control technology used in internal combustion engines (such as automobile engines) to reduce emissions of harmful pollutants such as nitrogen oxides (NOx) produced during combustion. Its basic principle is to reintroduce some exhaust gas into the engine cylinders to lower combustion temperatures (high temperatures are the primary cause of NOx formation). This is achieved by mixing the exhaust gas with fresh air before entering the cylinders, diluting the oxygen concentration and slowing the combustion rate, thereby reducing NOx formation under high-temperature and high-pressure conditions. An EGR system typically consists of an EGR valve, an ECU, an EGR cooler, sensors, and connecting piping. The EGR valve is the core component controlling the amount of exhaust gas recirculated, with its opening adjusted by the ECU based on operating conditions. The EGR cooler lowers exhaust gas temperatures, enhancing dilution and reducing the risk of knock. Sensors monitor parameters such as pressure and temperature in the connecting piping to ensure precise mixing of exhaust gas and fresh air. EGR technology allows engines to meet environmental regulations while maintaining both performance and efficiency, making it an indispensable emissions reduction solution for modern internal combustion engines.

[0003] During actual engine operation, the ECU controls the EGR valve opening and EGR flow rate based on engine speed and load information. This EGR valve opening control relies on the EGR valve's pressure differential or pressure ratio input. Related technologies typically use a pressure differential sensor installed on the EGR valve to obtain the EGR valve's pressure differential or pressure ratio. This approach requires a pressure differential sensor and is therefore cost-effective. 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 the use of a pressure difference 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, and in the exhaust gas recirculation system, an air filter and an intake flow control valve are sequentially provided in an intake pipe, an exhaust gas treatment device is provided in an exhaust pipe, and an exhaust gas cooler and an exhaust gas flow control valve are sequentially provided in an exhaust gas circulation pipe. The method comprises: obtaining the pressure and temperature at a first position based on the environment and the 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 state parameters of the environment, the exhaust gas treatment device and 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 gas 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 across the air filter is related to the air flow at the first location, and the pressure drop across 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, 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. The standard gas flow is related to the air flow, pressure and temperature at the first position, and the standard gas flow is a function or calibration 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 cooler is related to the exhaust flow rate at the fifth location. The pressure drop of the exhaust cooler is a function or a calibrated value based on the exhaust flow rate at the fifth location.

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

[0015] In some embodiments, obtaining the pressure at the third position includes: if the pipeline pressure 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 at the third position, and the pipeline pressure drop is a function or a calibrated value based on the exhaust gas flow 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, and the exhaust gas circulation pipe is provided with an exhaust gas cooler and an exhaust gas flow control valve in sequence. 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 the exhaust gas recirculation system of any embodiment of the present application, wherein the exhaust gas recirculation system executes the control method of 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 the 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 at multiple specific positions (i.e., the first position, the second position, and the fourth position) in the intake and exhaust pipes through a calculation model. Since the pressures at these multiple specific positions are in the intake and exhaust pipes, 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 structural diagram 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 This is a schematic diagram of the exhaust gas flow accuracy result of the exhaust gas flow control valve calculated based on the model in an embodiment of the present application.

[0026] Description of main component symbols

[0027] 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.

[0028] The following specific implementation mode will further illustrate this application in conjunction with the above-mentioned drawings.

[0029] Specific implementation mode

[0030] In the description of the embodiments of this application, words such as "exemplary," "or," and "for example" are used to indicate examples, illustrations, or descriptions. Any embodiment or design described as "exemplary" or "for example" in the embodiments of this application should not be construed as being preferred or advantageous over other embodiments or designs. Rather, the use of words such as "exemplary," "or," and "for example" is intended to present related concepts in a specific manner.

[0031] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application belongs. The terms used in the specification of this application are for the purpose of describing specific embodiments only 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 mean A or B. "And / or" in this application is merely a way to describe the association relationship of associated objects, indicating that three relationships can exist. For example, A and / or B can mean: 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 mean: a, b, c, a and b, a and c, b and c, a, b and c.

[0032] 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 methods disclosed in the embodiments of this application or the methods shown in the flowcharts include one or more steps for implementing the methods. Without departing from the scope of the claims, the order of execution of multiple steps can be interchanged with each other, and some steps can also be deleted.

[0033] Exhaust Gas Recirculation (EGR) is an emissions control technology used in internal combustion engines (such as automobile engines) to reduce emissions of harmful pollutants such as nitrogen oxides (NOx) generated during the combustion process. The basic principle is to reintroduce some exhaust gas into the engine cylinders to lower combustion temperatures (high temperatures are the primary cause of NOx formation). This is achieved by mixing the exhaust gas with fresh air before it enters the cylinders, diluting the oxygen concentration and slowing the combustion rate, thereby reducing NOx formation under high-temperature and high-pressure conditions.

[0034] EGR technology is a key tool for reducing fuel consumption in spark-ignition engines and is currently widely used in new energy hybrid engines. In new energy hybrid engines, the EGR system typically consists of an EGR valve, an engine control unit (ECU), an EGR cooler, sensors, and connecting piping. The EGR valve is the core component for controlling the amount of exhaust gas recirculation, with its opening adjusted by the ECU based on operating conditions. The EGR cooler reduces exhaust gas temperature, enhancing dilution and reducing the risk of knock. Sensors monitor parameters such as pressure and temperature in the connecting piping to ensure precise mixing of exhaust gas and fresh air. There are two main types of EGR: high-pressure and low-pressure. High-pressure EGR draws air directly from the exhaust manifold and is suitable for low-speed operation (common in traditional gasoline engines). Low-pressure EGR draws air downstream of the turbocharger, cools it, and introduces it into the intake system. It is commonly used in diesel and supercharged engines and offers greater efficiency and compatibility. EGR technology allows engines to meet environmental regulations while maintaining both performance and efficiency, making it an essential emission reduction solution for modern internal combustion engines.

[0035] However, in actual engine operation, the electronic control unit (ECU) plays a crucial role, optimizing engine combustion efficiency and emissions performance by precisely controlling the exhaust gas recirculation (EGR) valve opening and EGR flow rate. The primary function of the EGR system is to reintroduce some exhaust gas into the engine's intake system to reduce combustion chamber temperatures and nitrogen oxide (NOx) emissions. To achieve this, the ECU monitors engine speed and load in real time and dynamically adjusts the EGR valve opening based on this data. EGR valve opening control relies on the EGR valve's differential pressure or pressure ratio input. The differential pressure refers to the difference in pressure across the EGR valve, while the pressure ratio refers to the ratio of pressure upstream to downstream of the EGR valve. These parameters are crucial for precise EGR flow control, as they directly impact the effectiveness of exhaust gas recirculation. Traditional solutions typically incorporate a differential pressure sensor on the EGR valve to monitor the valve's differential pressure or pressure ratio in real time. This approach offers the advantage of providing highly accurate differential pressure or pressure ratio data, ensuring precise control of the EGR system.

[0036] However, installing a differential pressure sensor also presents some challenges. First, the sensor is expensive, which increases the overall manufacturing cost of the engine control system. Second, the sensor is complex to install and maintain, requiring additional space and wiring, which can increase engine complexity and malfunction rates. Furthermore, the sensor can become contaminated or damaged in harsh operating environments, affecting its measurement accuracy and reliability.

[0037] To this end, embodiments of the present application provide an exhaust gas recirculation system and control method thereof, an engine, and a vehicle that can reduce the cost associated with the use of differential pressure sensors. Specifically, they can achieve precise control of the EGR valve while reducing reliance on differential pressure sensors, thereby improving engine performance and reliability and reducing manufacturing and maintenance costs. Several embodiments are described below with reference to the accompanying drawings. The following embodiments and features thereof may be combined unless otherwise noted.

[0038] Figure 1 It is a schematic structural diagram of the exhaust gas recirculation system of an embodiment of the present application.

[0039] 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 recirculation pipe 500. The intake pipe 300 and the exhaust pipe 400 are both connected to the engine 100, and the exhaust gas recirculation pipe 500 is connected to the intake pipe 300 and the exhaust pipe 400.

[0040] In the embodiment of this application, Figure 1 As shown, the intake pipe 300 is sequentially provided with an air filter 1 and an intake flow control valve, which for ease of distinction is referred to herein as the "first intake flow control valve 2". The exhaust pipe 400 is provided with an exhaust gas treatment device 6, and the exhaust gas circulation pipe 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, and 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 pipes are 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. 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. The exhaust gas flow control valve 3 is located after the exhaust gas circulation pipeline 500, which is the outlet side. The outlet side is connected between the outlet side of the first intake flow control valve 2 and the intake side of the combustion chamber of the engine 100. Here, "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.

[0041] In some embodiments, as Figure 1As shown, the intake line 300 may also include an air supercharger 7, an air cooler 8, and a second intake air flow control valve 9, which are arranged in sequence. Specifically, from the intake side of the intake line 300 to the combustion chamber of the engine 100, an air filter 1, a first intake air flow control valve 2, an air supercharger 7, an air cooler 8, and a second intake air flow control valve 9 are arranged in sequence. In this embodiment, the outlet side is connected between the first intake air flow control valve 2 and the supercharger.

[0042] In some embodiments, as Figure 1 As shown, the exhaust line 400 may further include an exhaust turbine 10, which is disposed on the exhaust side of the combustion chamber of the engine 100. Specifically, the intake side of the exhaust turbine 10 is connected to the exhaust side of the combustion chamber of the engine 100, and the exhaust side of the exhaust turbine 10 is connected to the intake side of the exhaust gas treatment device 6.

[0043] In some embodiments, multiple exhaust gas treatment devices 6 may be connected in sequence.

[0044] In some embodiments, the air supercharger 7 is connected to the exhaust gas turbine 10 .

[0045] In the embodiments of this application, Figure 1 As shown, the electronic control unit 200, also known as 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 turbine 10, the exhaust gas treatment device 6, and the exhaust gas cooler 5, etc., and can also be used to read the current openings 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 openings of the first intake flow control valve 2, the second intake flow control valve 9, and the exhaust flow control valve 3.

[0046] 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 (e.g., Figure 1 The electronic control unit 200 can be used to read sensor data and control the air filter 1, the air supercharger 7, the air cooler 8, the engine 100, the exhaust 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.

[0047] In addition, the electronic control unit 200 can also be configured to execute the exhaust gas recirculation system control method of any embodiment of the present application. As follows, the embodiment of the present application also provides an exhaust gas recirculation system control method.

[0048] Figure 24 is a flow chart of a method for controlling an exhaust gas recirculation system according to an embodiment of the present application.

[0049] like Figure 2 As shown, the control method of the exhaust gas recirculation system of the embodiment of the present application may include:

[0050] Step S100 : obtaining the pressure at the first location based on the ambient atmospheric pressure and the pressure drop of the air filter.

[0051] 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.

[0052] 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 further include at least one of pressure, temperature, compression, or temperature difference.

[0053] In some embodiments, the pressure drop across the air filter is related to the air flow at the first location, and the pressure drop across the air filter is a function or a calibrated value based on the air flow.

[0054] In the embodiment of the present application, the pressure at the first position can be expressed by the formula:

[0055] (1)

[0056] Obtain. 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.

[0057] 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.

[0058] 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.

[0059] like Figure 2 As shown, the control method of the exhaust gas recirculation system in the embodiment of the present application may further include:

[0060] Step S200: Acquire the temperature of the first position based on the difference between the ambient temperature and the temperature of the air filter.

[0061] The temperature at the first position refers to the air temperature at the first position.

[0062] In some embodiments, the temperature difference is related to the air flow rate and the engine water temperature. The temperature difference is a function or a calibrated value based on the air flow rate and the engine water temperature. 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 expressed as:

[0063] (2)

[0064] Obtain. In formula (2), T A That is, 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 ( mair , T CEng )express.

[0065] 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.

[0066] 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.

[0067] like Figure 2 As shown, the control method of the exhaust gas recirculation system in the embodiment of the present application may further include:

[0068] 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.

[0069] 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.

[0070] 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 obtained by calculating 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. 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 ).

[0071] In some embodiments, the standard gas flow rate is related to the air flow rate, pressure, and temperature at the first location. The standard gas flow rate is a function or a calibrated value based on the air flow rate, pressure, and temperature at the first location. The standard gas flow rate can be expressed as:

[0072] (3)

[0073] Obtain. In formula (3), f ( P A )and f ( T A) are functions or calibration values ​​that correct the gas to its standard state (pressure and temperature). Correcting the gas to its standard state (pressure and temperature) means revising the state at the first location relative to the standard environment. For example, if the temperature at the first location is high, the gas density at that location will be lower than the ambient air, reducing the amount of air entering (i.e., regardless of pressure differences, a high temperature and low density at the first location will result in a low gas flow rate). Alternatively, if the pressure and density at the first location are low, the gas flow rate will be low.

[0074] Likewise, f ( wr k1 ，m c,air ) can be obtained by obtaining multiple air flow m air and the test data of the current opening of the intake flow control valve are 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.

[0075] 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. f ( wr k1 ，m c,air ) to make corrections. This can improve f ( wr k1 ，m c,air ) calculation accuracy.

[0076] like Figure 2 As shown, the control method of the exhaust gas recirculation system in the embodiment of the present application may further include:

[0077] Step S400: Based on the pressure at the second position, obtain the pressure at the third position.

[0078] 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.

[0079] In some embodiments, if the distance between the second position and the third position is less than or equal to a predetermined value, for example, the distance between the second position and the third position is small, the pressure loss of the pipeline is small, and the pressure at the second position can be used as the pressure at the third position, which 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.

[0080] In some embodiments, if the pressure drop in the pipeline between the second location and the third location is greater than a predetermined value, the pressure drop in the pipeline is large. In this case, the pressure at the third location can be obtained based on the pressure at the second location and the pressure drop in the pipeline between the second location and the third location. The pressure drop in the pipeline between the second location and the third location is related to the exhaust gas flow rate at the third location, and the pipeline pressure drop is a function or a calibrated value based on the exhaust gas flow rate at the third location. f1 ( m EGR ), where m EGR is the exhaust gas flow at the third location. The pressure at the third location can be expressed as:

[0081] (4)

[0082] Obtain. In formula (4), △ P BC That is, the pipeline pressure drop between the second position and the third position.

[0083] Likewise, f1 ( m EGR ) can obtain the exhaust gas flow rate of 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.

[0084] Similarly, in some embodiments, multiple parameters can be added, such as system design parameters (shape of the pipeline, resistance coefficient of the filter material) and dynamic operating parameters (transient flow rate change rate), etc. f1 ( m EGR ) to make corrections. This can improve f1 ( m EGR ) calculation accuracy.

[0085] 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 details will be given.

[0086] 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 value P 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 measurement values P C .

[0087] like Figure 2 As shown, the control method of the exhaust gas recirculation system in the embodiment of the present application may further include:

[0088] Step S500: obtaining the pressure at the fourth location based on the ambient atmospheric pressure and the pressure drop of the exhaust gas treatment device.

[0089] 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.

[0090] 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.

[0091] 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:

[0092] (5)

[0093] Obtain. In formula (5), P E That is, the pressure at the fourth position, PAmb is the ambient atmospheric pressure, △ P Exh is the pressure drop of the exhaust gas treatment device.

[0094] In some embodiments, the pressure drop of the exhaust treatment device is related to the exhaust flow rate at the fourth location. 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.

[0095] Likewise, f ( m exh ) can be obtained by obtaining the exhaust gas flow of multiple fourth positions m 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.

[0096] Similarly, in some embodiments, multiple parameters can be added, such as system design parameters (shape of the pipeline, resistance coefficient of the filter material) and dynamic operating parameters (transient flow rate change rate), etc. f ( m exh ) to make corrections. This can improve f ( m exh ) calculation accuracy.

[0097] like Figure 2 As shown, the control method of the exhaust gas recirculation system in the embodiment of the present application may further include:

[0098] Step S600: Obtaining the pressure at the fifth position based on the pressure at the fourth position and the pressure drop of the exhaust gas cooler.

[0099] 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.

[0100] 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 further include at least one of pressure, temperature, compression, or temperature difference.

[0101] 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. Therefore, the pressure at the fifth position can be expressed as follows:

[0102] (6)

[0103] Obtain. In formula (6), P’ D That is, the pressure at the fifth position, △ P EGRCooler is the pressure drop of the exhaust gas cooler.

[0104] In some embodiments, the pressure drop of the exhaust gas cooler is related to the exhaust gas flow rate at the fifth location. 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. f2 ( m EGR ), where m EGR is the exhaust gas flow rate at the fifth position.

[0105] Likewise, f2 ( m EGR ) can be obtained by obtaining the exhaust gas flow of 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.

[0106] Similarly, in some embodiments, multiple parameters can be added, such as ring system design parameters (shape of the pipeline, resistance coefficient of the filter material) and dynamic operating parameters (transient flow rate change rate), etc. f2 ( m EGR ) to make corrections. This can improve f2 ( m EGR ) calculation accuracy.

[0107] Figure 4 This is an embodiment of the present application P’ D Schematic diagram of the deviation results of the pressure model calculation.

[0108] 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 measurement values P D .

[0109] like Figure 2 As shown, the control method of the exhaust gas recirculation system in the embodiment of the present application may further include:

[0110] Step S700 : obtaining 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.

[0111] 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.

[0112] By combining gas dynamics principles 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 valve port cross-sectional area. 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:

[0113] (7)

[0114] 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 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 actual pressure ratio on flow rate.

[0115] 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.

[0116] Similarly, in some embodiments, multiple parameters can 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.

[0117] In the embodiments of this application, f ( wrk2 ) can also be modified 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 .

[0118] Figure 5 This is a schematic diagram of the exhaust gas flow accuracy result of the exhaust gas flow control valve calculated based on the model in an embodiment of the present application.

[0119] Likewise, if Figure 5 As shown, msagr is the embodiment of the present application m EGR , the model value m EGR Compare this with the actual measured value (i.e., the pressure value actually measured by the sensor). RMSE is the root mean square error, and R² is the coefficient of determination. A coefficient of determination of 0.98 or higher can meet engineering requirements.

[0120] like Figure 2 As shown, the control method of the exhaust gas recirculation system in the embodiment of the present application may further include:

[0121] Step S800: Controlling the opening of the intake flow control valve and the opening of the exhaust flow control valve based on the flow of the exhaust flow control valve.

[0122] This achieves closed-loop control of the exhaust gas flow control valve.

[0123] In addition, an embodiment of the present application further provides an engine, comprising the exhaust gas recirculation system of any embodiment of the present application, wherein the exhaust gas recirculation system executes the control method of any embodiment of the present application to achieve exhaust gas circulation control.

[0124] 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.

[0125] 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 at multiple specific positions (i.e., the first position, the second position, and the fourth position) in the intake and exhaust pipes through a calculation model. Since the pressures at these multiple specific positions are in the intake and exhaust pipes, 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.

[0126] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application and are not intended to limit the present application. Although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions 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 provided in an intake pipe, an exhaust gas treatment device is provided in an exhaust pipe, and an exhaust gas cooler and an exhaust gas flow control valve are sequentially provided in an exhaust gas circulation pipe, characterized in that: The method comprises: acquiring a pressure and a temperature at a first location based on the environment and a state parameter of the air filter; 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; acquiring a pressure at a fourth location and a pressure at a fifth location based on state parameters of the environment, the exhaust gas treatment device, and the exhaust gas cooler; obtaining a flow rate of the exhaust gas flow control valve based on an effective flow cross-sectional area of ​​the exhaust gas flow control valve, a pressure at the third position, and a state parameter at the fifth position; controlling the openings of the intake flow control valve and the exhaust flow control valve based on the flow rate of the exhaust flow control valve; Among them, 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 gas treatment device and the exhaust gas flow control valve and is close to the exhaust gas treatment device, and the fifth position is located between the exhaust gas flow control valve and the exhaust gas cooler and is close to the exhaust gas flow control valve.

2. The exhaust gas recirculation system control method according to claim 1, characterized in that: The obtaining of the pressure and temperature at the first position based on the environment and the state parameters of the air filter includes: obtaining a pressure at a first location based on an ambient atmospheric pressure and a pressure drop across 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.

3. The exhaust gas recirculation system control method according to claim 2, characterized in that: The pressure drop across the air filter is related to the air flow at the first location.

4. 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.

5. 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 a pressure at the fourth location based on an ambient atmospheric pressure and a 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 obtained based on the pressure at the fourth location and the pressure drop of the exhaust gas cooler.

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

7. 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 position.

8. 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.

9. 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.

10. The exhaust gas recirculation system control method according to claim 9, 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, obtaining the pressure of the third position 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.

11. 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.

12. 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 sequentially provided with an air filter and an intake flow control valve, the exhaust pipe is provided with an exhaust gas treatment device, the exhaust gas circulation pipe is sequentially provided with an exhaust gas cooler and an exhaust gas flow control valve, and the electronic control unit is configured to execute the control method according to any one of claims 1 to 11 to achieve exhaust gas circulation control.

13. An engine, characterized in that: The exhaust gas recirculation system comprises the exhaust gas recirculation system according to claim 12, wherein the exhaust gas recirculation system executes the control method according to any one of claims 1 to 11 to achieve exhaust gas circulation control.

14. A vehicle, characterized in that: The invention comprises an engine as claimed in claim 13, wherein the exhaust gas circulation control of the engine is achieved by the control method as claimed in any one of claims 1 to 11.

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