CN116857076A - Exhaust gas recirculation control method and system - Google Patents
Exhaust gas recirculation control method and system Download PDFInfo
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- 238000000034 method Methods 0.000 title claims abstract description 54
- 230000001052 transient effect Effects 0.000 claims abstract description 68
- 238000001228 spectrum Methods 0.000 claims abstract description 35
- 230000004044 response Effects 0.000 claims abstract description 15
- 230000001133 acceleration Effects 0.000 claims abstract description 14
- 239000007789 gas Substances 0.000 claims description 179
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 13
- 239000001301 oxygen Substances 0.000 claims description 13
- 229910052760 oxygen Inorganic materials 0.000 claims description 13
- 230000008859 change Effects 0.000 claims description 9
- 238000002485 combustion reaction Methods 0.000 claims description 8
- 230000008569 process Effects 0.000 claims description 7
- 238000004590 computer program Methods 0.000 claims description 6
- 238000006073 displacement reaction Methods 0.000 claims description 5
- 239000000446 fuel Substances 0.000 claims description 3
- 239000000779 smoke Substances 0.000 abstract description 11
- 238000004364 calculation method Methods 0.000 description 4
- 238000005516 engineering process Methods 0.000 description 3
- 238000011217 control strategy Methods 0.000 description 2
- 238000001816 cooling Methods 0.000 description 2
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- 238000012986 modification Methods 0.000 description 2
- 230000004043 responsiveness Effects 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 230000001276 controlling effect Effects 0.000 description 1
- 230000003111 delayed effect Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 230000006870 function Effects 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 239000010804 inert waste Substances 0.000 description 1
- 238000002347 injection Methods 0.000 description 1
- 239000007924 injection Substances 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 230000003134 recirculating effect Effects 0.000 description 1
- 230000001105 regulatory effect Effects 0.000 description 1
- 239000002912 waste gas Substances 0.000 description 1
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02D—CONTROLLING COMBUSTION ENGINES
- F02D41/00—Electrical control of supply of combustible mixture or its constituents
- F02D41/0025—Controlling engines characterised by use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures
- F02D41/0047—Controlling exhaust gas recirculation [EGR]
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02D—CONTROLLING COMBUSTION ENGINES
- F02D21/00—Controlling engines characterised by their being supplied with non-airborne oxygen or other non-fuel gas
- F02D21/06—Controlling engines characterised by their being supplied with non-airborne oxygen or other non-fuel gas peculiar to engines having other non-fuel gas added to combustion air
- F02D21/08—Controlling engines characterised by their being supplied with non-airborne oxygen or other non-fuel gas peculiar to engines having other non-fuel gas added to combustion air the other gas being the exhaust gas of engine
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02D—CONTROLLING COMBUSTION ENGINES
- F02D41/00—Electrical control of supply of combustible mixture or its constituents
- F02D41/0025—Controlling engines characterised by use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures
- F02D41/0047—Controlling exhaust gas recirculation [EGR]
- F02D41/005—Controlling exhaust gas recirculation [EGR] according to engine operating conditions
- F02D41/0052—Feedback control of engine parameters, e.g. for control of air/fuel ratio or intake air amount
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02D—CONTROLLING COMBUSTION ENGINES
- F02D41/00—Electrical control of supply of combustible mixture or its constituents
- F02D41/0025—Controlling engines characterised by use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures
- F02D41/0047—Controlling exhaust gas recirculation [EGR]
- F02D41/0065—Specific aspects of external EGR control
- F02D41/0072—Estimating, calculating or determining the EGR rate, amount or flow
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
- F02M26/00—Engine-pertinent apparatus for adding exhaust gases to combustion-air, main fuel or fuel-air mixture, e.g. by exhaust gas recirculation [EGR] systems
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02D—CONTROLLING COMBUSTION ENGINES
- F02D21/00—Controlling engines characterised by their being supplied with non-airborne oxygen or other non-fuel gas
- F02D21/06—Controlling engines characterised by their being supplied with non-airborne oxygen or other non-fuel gas peculiar to engines having other non-fuel gas added to combustion air
- F02D21/08—Controlling engines characterised by their being supplied with non-airborne oxygen or other non-fuel gas peculiar to engines having other non-fuel gas added to combustion air the other gas being the exhaust gas of engine
- F02D2021/083—Controlling engines characterised by their being supplied with non-airborne oxygen or other non-fuel gas peculiar to engines having other non-fuel gas added to combustion air the other gas being the exhaust gas of engine controlling exhaust gas recirculation electronically
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02D—CONTROLLING COMBUSTION ENGINES
- F02D41/00—Electrical control of supply of combustible mixture or its constituents
- F02D41/02—Circuit arrangements for generating control signals
- F02D41/14—Introducing closed-loop corrections
- F02D41/1401—Introducing closed-loop corrections characterised by the control or regulation method
- F02D2041/1409—Introducing closed-loop corrections characterised by the control or regulation method using at least a proportional, integral or derivative controller
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02D—CONTROLLING COMBUSTION ENGINES
- F02D41/00—Electrical control of supply of combustible mixture or its constituents
- F02D41/02—Circuit arrangements for generating control signals
- F02D41/14—Introducing closed-loop corrections
- F02D41/1401—Introducing closed-loop corrections characterised by the control or regulation method
- F02D2041/141—Introducing closed-loop corrections characterised by the control or regulation method using a feed-forward control element
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
- F02M26/00—Engine-pertinent apparatus for adding exhaust gases to combustion-air, main fuel or fuel-air mixture, e.g. by exhaust gas recirculation [EGR] systems
- F02M2026/001—Arrangements; Control features; Details
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y02T10/00—Road transport of goods or passengers
- Y02T10/10—Internal combustion engine [ICE] based vehicles
- Y02T10/40—Engine management systems
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- Engineering & Computer Science (AREA)
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- General Engineering & Computer Science (AREA)
- Exhaust-Gas Circulating Devices (AREA)
Abstract
The application belongs to the technical field of exhaust gas recirculation control, and provides an exhaust gas recirculation control method and system, wherein when the exhaust gas flow is acquired, a final exhaust gas flow set value is obtained through a correction coefficient, specifically, the correction coefficient is 1 in a steady state, the correction coefficient is smaller than 1 in a transient acceleration state, and the correction coefficient is larger than 1 in a transient deceleration state; the smoke intensity is guaranteed to be lower in transient state, the method is more practical, and the precision is higher; the exhaust gas recirculation control is carried out by adopting a method combining proportional integral differential control and feedforward control, specifically, the feedforward control adopts switching among different feedforward pulse spectrums, and under normal working conditions, the feedforward pulse spectrums quicken the transient response of the exhaust gas recirculation, so that the response of the exhaust gas recirculation is better, and under the transient action, the opening degree of the feedforward pulse spectrums is reduced, a great amount of exhaust gas can be prevented from entering an engine through an exhaust gas recirculation pipeline instantaneously, and the smoke intensity during sudden acceleration is reduced.
Description
Technical Field
The application belongs to the technical field of exhaust gas recirculation control, and particularly relates to an exhaust gas recirculation control method and system.
Background
The exhaust gas recirculation (Exhaust Gas Recirculation, EGR) technology is one of the key technologies for satisfying non-four emissions, and EGR is a process of reintroducing exhaust gas in an exhaust pipe into an intake pipe and participating in combustion, and by means of the EGR technology, NOX generated in the combustion process can be effectively reduced.
The inventor finds that during the traditional exhaust gas recirculation control, the control side is not adjusted according to the characteristics of NOX generation under different stable and transient working conditions, so that the control precision is low, the NOX generation amount is too high in the exhaust gas recirculation control process, and the traditional exhaust gas recirculation control method does not consider the pulse spectrum setting under different working conditions, so that the pulse spectrum setting cannot be quickly adapted to the transient response of the exhaust gas recirculation, and under the strong transient action, a great amount of instantaneous exhaust gas enters an engine through an exhaust gas recirculation pipeline, and the problem of suddenly increased smoke intensity occurs.
Disclosure of Invention
In order to solve the problems, the application provides an exhaust gas recirculation control method and an exhaust gas recirculation control system, wherein the application adopts a new EGR rate closed-loop control strategy, corrects the charging efficiency, considers a differential calibration strategy of steady state and transient state working conditions, and ensures that the control method of proportional integral differential control and feedforward ensures that the responsiveness of EGR is better and the control of NOX is more accurate.
In order to achieve the above object, the present application is realized by the following technical scheme:
in a first aspect, the present application provides an exhaust gas recirculation control method including:
acquiring actual exhaust gas flow and an exhaust gas flow set value;
according to the obtained actual exhaust gas flow and the exhaust gas flow set value, performing exhaust gas recirculation control by adopting a method combining proportional-integral-derivative control and feedforward control;
the exhaust gas flow is obtained by calculating an exhaust gas recirculation rate set value and the total intake air amount, the exhaust gas flow is subjected to a correction coefficient to obtain a final exhaust gas flow set value, the correction coefficient is 1 in a steady state, the correction coefficient is smaller than 1 in transient acceleration, and the correction coefficient is larger than 1 in transient deceleration; the feedforward control adopts the switching between different feedforward pulse spectrums, under the normal working condition, the feedforward pulse spectrums are used for accelerating the transient response of the exhaust gas recirculation, and under the transient action, the feedforward pulse spectrums are used for reducing the opening of the exhaust gas recirculation valve.
Further, when the exhaust gas flow set value is obtained, the charging efficiency is corrected by the actual intake air temperature, the intake air pressure and the exhaust air pressure.
Further, the intake total amount m2 is:
V＝V _eng ·λ
wherein: r represents a molar gas constant; v (V) _eng Representing engine displacement; lambda (lambda) 0 Representing the engine charging efficiency under different working conditions in the closed state of the exhaust gas recirculation valve; t (T) ref A reference temperature representing the working conditions of different engines in a standard environment; fac represents a temperature correction coefficient; f (n, P3-P2) represents the correction of the charging efficiency after the pressure difference of the intake air and the exhaust air after the exhaust gas recirculation valve is opened at each rotating speed, n represents the rotating speed of the engine, P3 represents the exhaust pressure, and P2 represents the intake pressure; lambda represents the actual inflation efficiency in the nonstandard state.
Further, the correction coefficient obtaining method comprises the following steps:
acquiring an actual Lambd under the exhaust gas recirculation rate according to the set exhaust gas recirculation rate under each working condition;
filling the actual Lambd of each working point into a set Lambd pulse spectrum;
dividing the set Lambd under each working condition by the actual Lambd to obtain the correction coefficient under the transient state.
Further, the actual Lambd is obtained by converting the exhaust oxygen concentration; exhaust gas oxygen concentration= ((total amount of intake air-amount of engine combustion consumption-amount of pure exhaust gas in exhaust gas)/(total amount of intake air + fuel consumption)). Oxygen concentration.
Furthermore, the pure exhaust gas quantity in the exhaust gas adopts a time delay module, and the delay time is calibrated according to the working condition.
Further, when the engine operates in the normal mode, the feedforward value is obtained by looking up a normal feedforward pulse spectrum table, and when the engine is judged to be in a strong transient state, the feedforward value is switched to the strong transient state feedforward; the strong transient state judging process is as follows: and judging whether the throttle change rate, the engine torque change rate and the rotating speed change rate exceed the calibrated limit values or not respectively.
In a second aspect, the present application also provides an exhaust gas recirculation control system comprising:
a data acquisition module configured to: acquiring actual exhaust gas flow and an exhaust gas flow set value;
a control module configured to: according to the obtained actual exhaust gas flow and the exhaust gas flow set value, performing exhaust gas recirculation control by adopting a method combining proportional-integral-derivative control and feedforward control;
the exhaust gas flow is obtained by calculating an exhaust gas recirculation rate set value and the total intake air amount, the exhaust gas flow is subjected to a correction coefficient to obtain a final exhaust gas flow set value, the correction coefficient is 1 in a steady state, the correction coefficient is smaller than 1 in transient acceleration, and the correction coefficient is larger than 1 in transient deceleration; the feedforward control adopts the switching between different feedforward pulse spectrums, under the normal working condition, the feedforward pulse spectrums are used for accelerating the transient response of the exhaust gas recirculation, and under the transient action, the feedforward pulse spectrums are used for reducing the opening of the exhaust gas recirculation valve.
In a third aspect, the present application also provides a computer-readable storage medium having stored thereon a computer program which, when executed by a processor, implements the steps of the exhaust gas recirculation control method according to the first aspect.
In a fourth aspect, the present application also provides an electronic device comprising a memory, a processor and a computer program stored on the memory and executable on the processor, the processor implementing the steps of the exhaust gas recirculation control method according to the first aspect when executing the program.
Compared with the prior art, the application has the beneficial effects that:
1. when the exhaust gas flow is obtained, a final exhaust gas flow set value is obtained through a correction coefficient, specifically, the correction coefficient is 1 in a steady state, the correction coefficient is smaller than 1 in transient acceleration, and the correction coefficient is larger than 1 in transient deceleration; the smoke intensity is guaranteed to be lower in transient state, the method is more practical, and the precision is higher; the exhaust gas recirculation control is carried out by adopting a method combining proportional integral differential control and feedforward control, specifically, the feedforward control adopts switching among different feedforward pulse spectrums, under normal working conditions, the feedforward pulse spectrums are used for accelerating transient response of exhaust gas recirculation, so that the response of the exhaust gas recirculation is better, under the transient action, the feedforward pulse spectrums are used for reducing the opening of an exhaust gas recirculation valve, and a great amount of instantaneous exhaust gas can be prevented from entering an engine through an exhaust gas recirculation pipeline, and smoke intensity during sudden acceleration is reduced;
2. in the application, the charging efficiency is corrected through the actual air inlet temperature, the air inlet pressure and the exhaust pressure, so that the air inlet amount is calculated more accurately, and the calculated exhaust gas flow is more accurate;
3. the application adopts the exhaust gas recirculation rate set value to carry out closed-loop control instead of directly adopting the exhaust gas flow, thereby ensuring better environmental applicability, for example, under the plateau environment or after the supercharger is continuously aged, the air inlet pressure is changed, the combustion state is changed, the exhaust gas quantity can be adaptively adjusted by adopting the exhaust gas recirculation rate closed-loop, and the emission is ensured to be within reasonable limit;
4. according to the application, real-time Lambd correction is performed, so that the smoke intensity in the transient state is lower, the actual Lambd calculation adopts inert waste gas recirculation to participate in calculation and uses a delay module, so that the method is more practical and has higher precision;
5. the proportional integral differential control and feedforward control method of the application ensures that the responsiveness of the exhaust gas recirculation is better, and the feedforward adopts a double MAP form to ensure that the performance calibration selectivity is larger and the performance is better in strong transient state.
Drawings
The accompanying drawings, which are included to provide a further understanding of the embodiments and are incorporated in and constitute a part of this specification, illustrate and explain the embodiments and together with the description serve to explain the embodiments.
FIG. 1 is an exhaust gas recirculation system according to embodiment 1 of the present application;
FIG. 2 is an overall EGR control strategy of embodiment 1 of the present application;
FIG. 3 is a practical Lambd acquisition method of example 1 of the present application;
FIG. 4 is a schematic diagram of a feedforward control module according to embodiment 1 of the present application;
fig. 5 is a strong transient state determination process according to embodiment 1 of the present application.
Detailed Description
The application will be further described with reference to the drawings and examples.
It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the application. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.
EGR: exhaust Gas Recirculation, the exhaust gas is recirculated, and the exhaust gas discharged from the engine is reintroduced into the air inlet pipe and is mixed with fresh gas and then enters the combustion chamber for combustion, so that the NOx emission of the engine can be effectively reduced.
And (3) ECU: electronic Control Unit, an electronic control unit.
EGR valve: for controlling the amount of recirculating exhaust gases, a so-called hot-side EGR valve before the EGR cooler and a so-called cold-side EGR valve after the EGR cooler.
VNT: variable Nozzle Turbine the turbine end exhaust gas inlet is provided with a nozzle ring with a changeable blade angle, and the nozzle ring can be completely opened and closed at any position, and the position can reach a designated position according to a signal sent by the ECU, so that the flow capacity of the supercharger at each engine speed is regulated, and the working efficiency and the response speed of the supercharger are ensured.
EGR driving differential pressure Δp: P3-P2, P3 is turbine front exhaust pressure, P2 is intake pipe intake pressure (supercharger boost pressure).
Example 1:
the method aims at solving the problems that the control precision is low, the NOX production amount is too high in the exhaust gas recirculation control process, and the smoke intensity suddenly increases when a large amount of instantaneous exhaust gas enters an engine through an exhaust gas recirculation pipeline in the traditional exhaust gas recirculation control method. The present embodiment provides an exhaust gas recirculation control method including:
acquiring actual exhaust gas flow and an exhaust gas flow set value;
according to the obtained actual exhaust gas flow and the exhaust gas flow set value, performing exhaust gas recirculation control by adopting a method combining proportional-integral-derivative control and feedforward control;
the exhaust gas flow is obtained by calculating an exhaust gas recirculation rate set value and the total intake air amount, the exhaust gas flow is subjected to a correction coefficient to obtain a final exhaust gas flow set value, the correction coefficient is 1 in a steady state, the correction coefficient is smaller than 1 in transient acceleration, and the correction coefficient is larger than 1 in transient deceleration; the feedforward control adopts the switching between different feedforward pulse spectrums, under the normal working condition, the feedforward pulse spectrums are used for accelerating the transient response of the exhaust gas recirculation, and under the transient action, the feedforward pulse spectrums are used for reducing the opening of the exhaust gas recirculation valve.
Specifically, when the exhaust gas flow is obtained, a final exhaust gas flow set value is obtained through a correction coefficient, specifically, the correction coefficient is 1 in a steady state, the correction coefficient is smaller than 1 in a transient acceleration state, and the correction coefficient is larger than 1 in a transient deceleration state; the smoke intensity is guaranteed to be lower in transient state, the method is more practical, and the precision is higher; the exhaust gas recirculation control is carried out by adopting a method combining proportional integral differential control and feedforward control, specifically, the feedforward control adopts switching among different feedforward pulse spectrums, and under normal working conditions, the feedforward pulse spectrums quicken the transient response of the exhaust gas recirculation, so that the response of the exhaust gas recirculation is better, and under the transient action, the opening degree of the feedforward pulse spectrums is reduced, a great amount of exhaust gas can be prevented from entering an engine through an exhaust gas recirculation pipeline instantaneously, and the smoke intensity during sudden acceleration is reduced.
In this embodiment, the hardware configuration corresponding to the exhaust gas recirculation system is as shown in fig. 1:
alternatively, an intake air temperature and pressure sensor is installed on an intake manifold (after EGR mixing) to measure the temperature T2 and the pressure P2 of the gas entering the Engine (Engine), respectively. A pressure sensor may be installed before the exhaust turbine to measure the exhaust pressure P3. The amount of EGR exhaust gas may be measured using an exhaust venturi. The supercharger may be configured as a normal bleed valve supercharger, uncontrolled (ECU cannot control the supercharger), non-VNT supercharger.
In this embodiment, the overall strategy of EGR control is shown in fig. 2:
alternatively, the overall control may be implemented by a Proportional-Integral-Derivative control (PID) control method, and the exhaust gas flow set point may be obtained by calculating an EGR rate set point MAP (EGR rate MAP), where the EGR rate set point MAP may be calibrated according to different operating conditions. The EGR rate is understood to be the ratio of the amount of recirculated exhaust gas to the total amount of intake air drawn into the cylinders.
An intake air temperature pressure sensor mounted on the engine measures an intake air pressure P2 (supercharger boost pressure) and an intake air temperature T2 entering the engine, and the intake air temperature pressure sensor calculates and acquires a total intake air amount m2 entering the engine, wherein a calculation formula is as follows:
V＝V _eng ·λ (2)
wherein: r represents a molar gas constant; v (V) _eng Representing the displacement of the engine, and obtaining the displacement according to the actual condition by calibrating the displacement of the engine as a known quantityTaking; lambda (lambda) 0 The engine charging efficiency representing the different working conditions under the EGR valve closing state/standard environment state can be obtained in a calibrated manner in a laboratory standard environment, and the standard environment specifically refers to the reference after-cooling temperature T ref For example, the temperature after cooling is 50 ℃ at a calibrated working point; t (T) ref The reference temperature representing the working conditions of different engines in the standard environment can be obtained through calibration, for example, after the calibration point is fixed at 50 ℃, each working condition point has a fixed intercooling post temperature, T ref MAP based on the rotation speed n and the injection amount; fac represents a temperature correction coefficient and can be obtained through calibration; f (n, P3-P2) represents correction of the charging efficiency after the pressure difference of the intake air and the exhaust air is changed after the EGR valve is opened at each rotating speed, and the correction can be obtained through calibration, and n represents the rotating speed of the engine; lambda represents the actual charge efficiency in the nonstandard state and can be determined based on the actual intake air temperatures T and f (n, P3-P2).
The actual exhaust gas flow can be obtained by an exhaust venturi tube arranged on an EGR pipeline of an engine, and the calculation formula is shown in a formula (4):
wherein: Δp is the differential pressure measured by a differential pressure sensor mounted on the venturi; cε is an outflow coefficient that represents the coefficient of the relationship between the actual flow through the device and the theoretical flow; beta is the diameter ratio, the ratio of venturi throat diameter to inlet diameter; d is the diameter of the venturi throat; ρ is the density of the venturi inlet gas, specifically calculated from the temperature and pressure of the inlet gas.
The exhaust gas flow is obtained by the set value of the EGR rate and the total intake air amount m2, and the final set value of the exhaust gas flow is obtained by the exhaust gas flow through a Lambd correction coefficient A, wherein the method for obtaining the Lambd correction coefficient comprises the following steps:
the ECU acquires the actual Lambd under the EGR rate according to the set EGR rate under each working condition;
filling the actual Lambd of each working point into a set Lambd pulse spectrum (MAP);
dividing the set Lambd under each working condition by the actual Lambd to obtain a correction coefficient A under the transient state.
The actual Lambd obtaining method is shown in fig. 3:
the amount of exhaust gas megr may be obtained by an exhaust venturi installed on the EGR line;
EGFVCtl_rO2AirRef_C is the mass fraction 0.2315 of oxygen in the atmosphere; the conversion formula of the exhaust oxygen concentration EGFVCtl_rO2ModVal and the actual Lambd (EGFVCtl_rLamactVal) is as follows:
wherein O is 2 Is the exhaust oxygen concentration EGFVCtl_rO2ModVal.
The method for obtaining the exhaust gas oxygen concentration EGFVCtl_rO2ModVal is shown in FIG. 3:
egfvctl_ro2 modval= ((intake air amount m 2-amount of combustion consumption of engine-amount of pure exhaust gas in EGR exhaust gas)/(intake air amount m2+fuel consumption))) oxygen concentration.
Wherein: considering the actual situation of the delay of the recirculation of the exhaust gas, the pure exhaust gas amount in the EGR exhaust gas adopts a Time delay module, and the delay Time can be calibrated according to the working condition (Time delay). Exhaust gas is oxygen-containing and EGR recycle gas is also oxygen-containing in some amount: megr/Lambd calculates the amount of pure exhaust gas in EGR (inert EGR amount).
The feedforward control module is composed of two parts, namely a feedforward MAP and a strong transient feedforward MAP under normal working conditions as shown in fig. 4, when the engine operates in a normal mode, a feedforward value is obtained by looking up a table of the normal feedforward MAP, and when the engine is judged to be in a strong transient state, the feedforward value is switched into the strong transient feedforward, and in general, the strong transient feedforward MAP has smaller calibrated opening degree, for example, 0%.
The strong transient state judging process is as shown in fig. 5:
judging whether the throttle change rate, the engine torque change rate and the rotating speed change rate exceed the calibration limit values or not respectively;
based on the time delay cur of the engine speed calibration state, the strong transient state can be delayed for a period of time (for example, 1 s), and the setting of the function can ensure the control stability of EGR in the transient state of the engine.
Advantages of using Lambd based correction and feed forward control:
filling the actual Lambd of the engine into a set Lambd pulse spectrum in a steady state, wherein the correction coefficient is 1, and no correction exists; the actual Lambd is different from the set Lambd in transient state, and correction exists, for example, the actual Lambd is smaller than the set Lambd under the working condition in acceleration, the correction coefficient is smaller than 1, the set value of the exhaust gas flow is smaller, the actual opening degree of the EGR is smaller, so that the transient smoke degree of the engine is reduced, the acceleration dynamic property is improved, the air inflow is relatively sufficient in deceleration, NOX is higher, the correction coefficient is larger than 1 at the moment, the opening degree of the EGR is larger, and the effect of reducing NOX is good. According to the different intensity of the transient state, the correction is different, and the larger the transient state intensity is, the more obvious the correction is.
The feedforward adopts the switching among different MAP, under the normal working condition, the setting and the calibration of feedforward MAP can accelerate the transient response of EGR, under the strong transient action, feedforward MAP is switched into the opening (for example, 0%) that the opening is relatively smaller, can make the EGR valve close fast, can prevent in the twinkling of an eye that a large amount of waste gas from entering the engine through the EGR pipeline like this, reduce the smoke intensity when accelerating suddenly.
Example 2:
the present embodiment provides an exhaust gas recirculation control system including:
a data acquisition module configured to: acquiring actual exhaust gas flow and an exhaust gas flow set value;
a control module configured to: according to the obtained actual exhaust gas flow and the exhaust gas flow set value, performing exhaust gas recirculation control by adopting a method combining proportional-integral-derivative control and feedforward control;
the exhaust gas flow is obtained by calculating an exhaust gas recirculation rate set value and the total intake air amount, the exhaust gas flow is subjected to a correction coefficient to obtain a final exhaust gas flow set value, the correction coefficient is 1 in a steady state, the correction coefficient is smaller than 1 in transient acceleration, and the correction coefficient is larger than 1 in transient deceleration; the feedforward control adopts the switching between different feedforward pulse spectrums, under the normal working condition, the feedforward pulse spectrums are used for accelerating the transient response of the exhaust gas recirculation, and under the transient action, the feedforward pulse spectrums are used for reducing the opening of the exhaust gas recirculation valve.
The operation method of the system is the same as that of the exhaust gas recirculation control method of embodiment 1, and will not be described here again.
Example 3:
the present embodiment provides a computer-readable storage medium having stored thereon a computer program which, when executed by a processor, implements the steps of the exhaust gas recirculation control method described in embodiment 1.
Example 4:
the present embodiment provides an electronic device including a memory, a processor, and a computer program stored on the memory and executable on the processor, the processor implementing the steps of the exhaust gas recirculation control method described in embodiment 1 when executing the program.
The above description is only a preferred embodiment of the present embodiment, and is not intended to limit the present embodiment, and various modifications and variations can be made to the present embodiment by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present embodiment should be included in the protection scope of the present embodiment.
Claims (10)
1. An exhaust gas recirculation control method, characterized by comprising:
acquiring actual exhaust gas flow and an exhaust gas flow set value;
according to the obtained actual exhaust gas flow and the exhaust gas flow set value, performing exhaust gas recirculation control by adopting a method combining proportional-integral-derivative control and feedforward control;
the exhaust gas flow is obtained by calculating an exhaust gas recirculation rate set value and the total intake air amount, the exhaust gas flow is subjected to a correction coefficient to obtain a final exhaust gas flow set value, the correction coefficient is 1 in a steady state, the correction coefficient is smaller than 1 in transient acceleration, and the correction coefficient is larger than 1 in transient deceleration; the feedforward control adopts the switching between different feedforward pulse spectrums, under the normal working condition, the feedforward pulse spectrums are used for accelerating the transient response of the exhaust gas recirculation, and under the transient action, the feedforward pulse spectrums are used for reducing the opening of the exhaust gas recirculation valve.
2. The exhaust gas recirculation control method according to claim 1, wherein the charging efficiency is corrected by the actual intake air temperature, the intake air pressure, and the exhaust gas pressure when the exhaust gas flow rate set value is acquired.
3. The exhaust gas recirculation control method according to claim 1, characterized in that the intake air total amount m2 is:
V＝V _eng ·λ
wherein: r represents a molar gas constant; v (V) _eng Representing engine displacement; lambda (lambda) 0 Representing the engine charging efficiency under different working conditions in the closed state of the exhaust gas recirculation valve; t (T) ref A reference temperature representing the working conditions of different engines in a standard environment; fac represents a temperature correction coefficient; f (n, P3-P2) represents the correction of the charging efficiency after the pressure difference of the intake air and the exhaust air after the exhaust gas recirculation valve is opened at each rotating speed, n represents the rotating speed of the engine, P3 represents the exhaust pressure, and P2 represents the intake pressure; lambda represents the actual inflation efficiency in the nonstandard state.
4. The exhaust gas recirculation control method according to claim 1, characterized in that the correction coefficient acquisition method is:
acquiring an actual Lambd under the exhaust gas recirculation rate according to the set exhaust gas recirculation rate under each working condition;
filling the actual Lambd of each working point into a set Lambd pulse spectrum;
dividing the set Lambd under each working condition by the actual Lambd to obtain the correction coefficient under the transient state.
5. The exhaust gas recirculation control method according to claim 4, wherein the actual Lambd is obtained by converting an exhaust gas oxygen concentration; exhaust gas oxygen concentration= ((total amount of intake air-amount of engine combustion consumption-amount of pure exhaust gas in exhaust gas)/(total amount of intake air + fuel consumption)). Oxygen concentration.
6. A method for recirculation control of exhaust gases according to claim 5, wherein the amount of pure exhaust gases in the exhaust gases is provided by a time delay module, the time delay being calibrated based on operating conditions.
7. The exhaust gas recirculation control method according to claim 1, wherein the feedforward value is obtained by a normal feedforward pulse spectrum lookup table when the engine is operated in the normal mode, and the feedforward value is switched to a strong transient feedforward when the engine is judged to be in a strong transient state; the strong transient state judging process is as follows: and judging whether the throttle change rate, the engine torque change rate and the rotating speed change rate exceed the calibrated limit values or not respectively.
8. An exhaust gas recirculation control system, characterized by comprising:
a data acquisition module configured to: acquiring actual exhaust gas flow and an exhaust gas flow set value;
a control module configured to: according to the obtained actual exhaust gas flow and the exhaust gas flow set value, performing exhaust gas recirculation control by adopting a method combining proportional-integral-derivative control and feedforward control;
the exhaust gas flow is obtained by calculating an exhaust gas recirculation rate set value and the total intake air amount, the exhaust gas flow is subjected to a correction coefficient to obtain a final exhaust gas flow set value, the correction coefficient is 1 in a steady state, the correction coefficient is smaller than 1 in transient acceleration, and the correction coefficient is larger than 1 in transient deceleration; the feedforward control adopts the switching between different feedforward pulse spectrums, under the normal working condition, the feedforward pulse spectrums are used for accelerating the transient response of the exhaust gas recirculation, and under the transient action, the feedforward pulse spectrums are used for reducing the opening of the exhaust gas recirculation valve.
9. A computer-readable storage medium, on which a computer program is stored, characterized in that the program, when being executed by a processor, implements the steps of the exhaust gas recirculation control method according to any one of claims 1 to 7.
10. An electronic device comprising a memory, a processor and a computer program stored on the memory and executable on the processor, characterized in that the processor implements the steps of the exhaust gas recirculation control method according to any one of claims 1-7 when executing the program.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN117452795A (en) * | 2023-12-18 | 2024-01-26 | 潍柴动力股份有限公司 | Method for determining delay time of intake air flow and related equipment |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN117452795A (en) * | 2023-12-18 | 2024-01-26 | 潍柴动力股份有限公司 | Method for determining delay time of intake air flow and related equipment |
| CN117452795B (en) * | 2023-12-18 | 2024-04-16 | 潍柴动力股份有限公司 | Method for determining delay time of intake air flow and related equipment |
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