CN113482785B - Engine air inlet flow prediction method and system - Google Patents

Engine air inlet flow prediction method and system Download PDF

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Publication number
CN113482785B
CN113482785B CN202110874486.1A CN202110874486A CN113482785B CN 113482785 B CN113482785 B CN 113482785B CN 202110874486 A CN202110874486 A CN 202110874486A CN 113482785 B CN113482785 B CN 113482785B
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time period
air flow
manifold
cylinder
flow
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CN113482785A (en
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吕鹏
邹剑华
张甲乐
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Dongfeng Trucks Co ltd
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Dongfeng Trucks Co ltd
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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
    • F02D41/18—Circuit arrangements for generating control signals by measuring intake air flow

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Abstract

The application relates to a method and a system for estimating air inlet flow of an engine, comprising the following steps: based on the mixed gas flow entering the cylinder in the current time period and the previous time period, obtaining the air flow discharged by the manifold and entering the cylinder in the current time period and the previous time period, and carrying out difference on the air flow and the air flow to obtain a first difference value; obtaining an air flow estimated value of the throttle valve entering the manifold in the next time period based on the expected throttle valve flow in the current time period and the throttle valve flow under the throttle valve opening in the current time period; the in-cylinder intake air amount for the next period is obtained based on the first difference, the air flow predicted value, and the air flow rate that is discharged from the manifold and into the cylinder for the current period. Therefore, the fresh air flow filled in the air inlet manifold under the dynamic working condition is estimated based on the expected throttle flow, and the purpose of accurately estimating the dynamic air inlet flow of the single-point injection engine is achieved.

Description

Engine air inlet flow prediction method and system
Technical Field
The present disclosure relates to the field of engine control technologies, and in particular, to a method and a system for estimating intake air flow of an engine.
Background
The gas entering the cylinder of the air inlet injection engine is the mixed gas of oil and air, and the fuel injection time is earlier than the air input completion time (namely, the fuel injection is usually injected into the air inlet manifold in advance for premixing), namely, the fuel injection is completed before the air inlet stroke bottom dead center is completed. If the engine is operating in steady state conditions, fuel concentration may be accurately ensured. However, if the engine is under a transient condition in which the engine is suddenly changed, the next cylinder intake air amount must be estimated approximately before the fuel amount is calculated, and then the target fuel amount is calculated based on the intake air amount. Therefore, the air-fuel ratio of the next time period can be better ensured, otherwise, the phenomena of lean acceleration and over-rich deceleration of the engine are easy to occur, the torque responsiveness is poor under the transient working condition, the emission is deteriorated, and the air inflow in the cylinder is estimated.
In some related technologies, the dynamic intake air flow estimation scheme adopted by the current single-point injection engine is the same as that of the intake port multi-point injection engine, namely, based on manifold pressures in the current time period and the previous time period, the manifold pressure in the next time period is estimated through interpolation, and the estimated intake air flow is calculated by using a speed-density method, but the following problems exist:
(1) For a single-point injection engine, since fuel oil (or gas) is injected at the front end of an intake manifold, oil and gas are mixed in the intake manifold and then enter an in-cylinder combustion engine, the expected fuel injection quantity should be calculated based on fresh air flow in the intake manifold, and the dynamic intake air flow of the engine with single-point injection is estimated by adopting dynamic intake air flow estimation of the multi-point injection engine, so that the fresh air flow filled in the intake manifold under the dynamic working condition is not estimated, and the estimation of the engine intake air quantity in the next time period is deviated.
(2) The expected throttle opening is not considered when the dynamic air inlet flow is estimated, the requirements of the expected throttle opening in different states are different, and when the expected throttle opening changes, the estimated air inlet flow has great deviation from the actual flow.
Disclosure of Invention
The embodiment of the application provides an engine air inlet flow estimation method and system, which are used for solving the problems that in the related art, the dynamic air inlet flow of a single-point injection engine is estimated, the fresh air flow filled in an air inlet manifold under a dynamic working condition is not estimated, and the estimation of the air inlet amount of the engine in the next time period is deviated.
In a first aspect, a method for estimating an intake air flow of an engine is provided, including the steps of:
based on the mixed gas flow entering the cylinder in the current time period and the previous time period, obtaining the air flow discharged by the manifold and entering the cylinder in the current time period and the previous time period, and carrying out difference on the air flow and the air flow to obtain a first difference value;
obtaining an air flow estimated value of the throttle valve entering the manifold in the next time period based on the expected throttle valve flow in the current time period and the throttle valve flow under the throttle valve opening in the current time period;
and obtaining the in-cylinder air inflow of the next time period based on the first difference value, the air flow predicted value and the air flow discharged by the manifold and entering the cylinder in the current time period.
Obtaining whether the manifold is in the air charging process or the air discharging process corresponding to the next time period of the engine and the air charging or air discharging quantity, adding the air charging or air discharging quantity to the air flow discharged by the manifold and entering the cylinder in the current time period to obtain the value which is the air inflow of the cylinder in the next time period, thus, the air inflow of the cylinder in the next time period is estimated by taking different conditions of the air inflow of the manifold under different working conditions of the engine into consideration based on the expected throttle flow in the above way, the error caused by the air inflow estimation method of the multi-point injection engine is avoided, and the purpose of accurately estimating the dynamic air inflow of the single-point injection engine is realized
In some embodiments, the air flow rate of the manifold exiting and entering the cylinder for the current time period is calculated according to a first formula, wherein the first formula comprises:
Figure GDA0004082914970000031
wherein ,
Figure GDA0004082914970000032
air flow rate for manifold exhaust and into cylinder for current period EGR In order for the EGR rate to be desired,
Figure GDA0004082914970000033
the flow of the mixed gas into the cylinder for the current time period;
calculating an air flow rate of the manifold exiting and entering the cylinder for a previous period according to a second formula, wherein the second formula comprises:
Figure GDA0004082914970000034
wherein ,
Figure GDA0004082914970000035
for the last period of air flow rate from the manifold into the cylinder EGR-old For the last period the EGR rate is desired, +.>
Figure GDA0004082914970000036
For the amount of mixed gas that enters the cylinder for the previous time period.
In some embodiments, the engine intake air flow estimation method further includes calculating
Figure GDA0004082914970000038
Is calculated by the steps of
Figure GDA0004082914970000039
Comprising the following steps:
establishing a manifold pressure model and acquiring manifold pressure sensor measurements for a current time period to estimate a current time period manifold pressure model value MAP est ；
Based on the MAP est Calculating the flow of the mixed gas into the cylinder through the inlet valve in the current time period by using a speed-density method
Figure GDA0004082914970000037
In some embodiments, based on the expected throttle flow in the current time period and the throttle flow under the throttle opening in the current time period, an air flow predicted value of the throttle entering the manifold in the next time period is obtained, and the method specifically comprises the following steps:
the expected throttle flow in the current time period and the throttle flow under the throttle opening in the current time period are subjected to difference to obtain a second difference value;
and carrying out attenuation treatment on the second difference value to obtain an air flow predicted value of the throttle valve entering the manifold in the next time period.
In some embodiments, the attenuating process is performed on the second difference to obtain an air flow predicted value of the throttle valve entering the manifold in a next period of time, and the method includes the following steps:
performing attenuation treatment on the second difference value once to obtain an attenuation value;
judging whether the expected throttle valve flow changes in the current time period;
if the throttle valve is not changed, taking the attenuation value as an air flow predicted value of the throttle valve entering the manifold in the next time period;
if so, the expected throttle flow after the change of the current time period is different from the throttle flow under the throttle opening of the current time period, the attenuation value is added to obtain an updated second difference value, the updated second difference value is subjected to attenuation processing once to obtain a new attenuation value, and the new attenuation value is used as an air flow predicted value of the throttle entering the manifold in the next time period.
In some embodiments, the second difference is attenuated by filtering.
In some embodiments, the method further includes obtaining an in-cylinder intake air amount for a next time period based on the first difference, the air flow predicted value, and an air flow rate discharged from the manifold and into the cylinder for the current time period, including the steps of:
performing difference on the air flow predicted value and the first difference value to obtain a third difference value;
and adding the third difference value and the air flow discharged by the manifold and entering the cylinder in the current time period to obtain the air inflow in the cylinder in the next time period.
In some embodiments, after obtaining the third difference, before adding the third difference to the air flow rate of the manifold exhaust and into the cylinder for the current time period, the method further comprises the steps of:
and correcting the third difference value by using a correction coefficient.
In some embodiments, the throttle flow at the throttle opening is calculated according to a third formula
Figure GDA0004082914970000042
Wherein the third formula comprises:
Figure GDA0004082914970000041
wherein ,Pin For throttle front pressure, P out Is the throttle back pressure, T in For the front temperature of throttle, A eff R is a gas constant, P is an effective sectional area related to throttle opening 0 and T0 Is the pressure and temperature under standard conditions, P 0 ＝101.3kPa，T 0 ＝20℃。
In a second aspect, an engine intake air flow estimation system is provided, comprising:
the first module is used for obtaining the air flow discharged by the manifold and entering the cylinder in the current time period and the previous time period based on the air flow of the mixture entering the cylinder in the current time period and the previous time period, and obtaining a first difference value by differencing the air flow discharged by the manifold and the air flow entering the cylinder in the current time period and the previous time period;
a second module for obtaining an air flow estimated value of the throttle valve into the manifold in the next time period based on the expected throttle flow in the current time period and the throttle flow at the throttle opening in the current time period;
and a third module for obtaining an in-cylinder intake air amount for a next period based on the first difference, the air flow predicted value, and an air flow amount that is manifold-discharged and taken into the cylinder for the current period.
The beneficial effects that technical scheme that this application provided brought include:
the embodiment of the application provides a method and a system for estimating the air intake flow of an engine, which divide the operation of the engine into a plurality of operation time periods, calculate the mixed air flow of the current time period and the last time period entering a cylinder, and the expected throttle flow of the current time period and the throttle flow under the throttle opening of the current time period, then respectively obtain the predicted value of the air flow of the throttle entering the manifold of the next time period and the difference value of the air flow of the manifold of the current time period and the last time period discharged by the manifold and entering the cylinder, and then, the difference value is differed from the predicted value of the air flow entering the manifold, whether the manifold is in the process of charging or discharging in the next time period of the engine or the quantity of charging or discharging is obtained, and the air flow discharged by the manifold and entering the cylinder in the current time period is added to the quantity of charging or discharging, namely the air inflow in the cylinder in the next time period, so that the air inflow in the cylinder in the next time period is estimated according to the air inflow in the manifold under different working conditions in the above mode, and the purpose of accurately estimating the dynamic air inflow of the single-point injection engine is realized.
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In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are needed in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a flowchart of a method for estimating engine intake air flow according to an embodiment of the present disclosure;
FIG. 2 is a flow chart providing a method for attenuating when a desired throttle flow is changed to obtain an estimated air flow value for a next period of throttle into a manifold according to an embodiment of the present application.
Detailed Description
For the purposes of making the objects, technical solutions and advantages of the embodiments of the present application more clear, the technical solutions of the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is apparent that the described embodiments are some embodiments of the present application, but not all embodiments. All other embodiments, which can be made by one of ordinary skill in the art without undue burden from the present disclosure, are within the scope of the present application based on the embodiments herein.
The embodiment of the application provides an engine air inlet flow estimation method and system, which are used for solving the problems that in the related art, the dynamic air inlet flow of a single-point injection engine is estimated, the fresh air flow filled in an air inlet manifold under a dynamic working condition is not estimated, and the estimation of the air inlet amount of the engine in the next time period is deviated.
The inventor has found that, based on the principle of influence of the filling effect of the intake manifold on the in-cylinder dynamic intake air flow rate:
for single-point injection engines, since fuel (or gas) is injected at the front end of the intake manifold, and the fuel is mixed in the intake manifold and then enters the cylinder to be combusted, the desired fuel injection amount should be calculated based on the air flow newly filled into the intake manifold. Considering the intake manifold as an opening system, the pressure change equation in the intake manifold can be obtained according to the ideal gas state equation, specifically the following formula:
Figure GDA0004082914970000061
wherein Vm For the volume of the intake manifold,
Figure GDA0004082914970000062
t is the pressure in the intake manifold m For the front temperature of the throttle, R is the gas constant +.>
Figure GDA0004082914970000063
For the intake air flow into the intake manifold, +.>
Figure GDA0004082914970000064
Is the flow out of the intake manifold.
According to the formula, when the engine is in a steady-state working condition, the air inlet flow rate flowing into the air inlet manifold
Figure GDA0004082914970000065
Flow out of intake manifold =>
Figure GDA0004082914970000066
At this time the air flow in the intake manifold ∈ ->
Figure GDA0004082914970000067
=air flow through throttle->
Figure GDA0004082914970000068
=air flow through intake valve->
Figure GDA0004082914970000069
When the engine is in a transitional working condition, the throttle valve is quickly opened, the air inlet manifold carries out an air charging process, and the air inlet flow flowing into the air inlet manifold
Figure GDA0004082914970000071
Flow outFlow of intake manifold>
Figure GDA0004082914970000072
Thus pressure variation in manifold>
Figure GDA0004082914970000073
When the throttle valve is closed quickly, the air inlet manifold is an exhaust process, and the air inlet flow rate flowing into the air inlet manifold is +.>
Figure GDA0004082914970000074
< flow out of intake manifold
Figure GDA0004082914970000075
Thus pressure variation in manifold>
Figure GDA0004082914970000076
At this time, the intake air flow rate into the intake manifold calculated from the compressible gas equation
Figure GDA0004082914970000077
Or the intake air flow into the engine cylinder calculated by the speed-density method is not equal to the fresh air flow in the intake manifold +.>
Figure GDA0004082914970000078
Resulting in inaccurate calculation of the desired fuel flow. Therefore, the following method for estimating the air inlet flow of the engine is provided.
Referring to fig. 1, a method for estimating an intake air flow of an engine includes the following steps:
101. calculating the mixed gas flow entering the cylinder in the current time period and the mixed gas flow entering the cylinder in the last time period, and obtaining the air flow discharged by the manifold and entering the cylinder in the current time period based on the mixed gas flow entering the cylinder in the current time period and the mixed gas flow entering the cylinder in the last time period
Figure GDA0004082914970000079
And the air flow rate of the manifold discharged and into the cylinder in the previous period +.>
Figure GDA00040829149700000710
Then difference is carried out on the two to obtain a first difference value +.>
Figure GDA00040829149700000726
I.e. the first difference is given according to the following formula>
Figure GDA00040829149700000711
Figure GDA00040829149700000712
First difference->
Figure GDA00040829149700000713
A gradient of variation in the flow of air that is manifold out and into the cylinder for the current and previous time periods.
102. Calculating the expected throttle flow in the current time period
Figure GDA00040829149700000714
And throttle flow at the throttle opening of the current period +.>
Figure GDA00040829149700000715
Desired throttle flow based on the current time period>
Figure GDA00040829149700000716
And throttle flow at the throttle opening of the current period +.>
Figure GDA00040829149700000717
Obtaining the air flow predicted value of the throttle valve entering the manifold in the next period +.>
Figure GDA00040829149700000718
103. Based on the first difference
Figure GDA00040829149700000719
Air flow predictive value->
Figure GDA00040829149700000720
And the current period of air flow rate of manifold exhaust and into cylinder +.>
Figure GDA00040829149700000721
The cylinder intake air amount +.for the next period is obtained according to the following formula>
Figure GDA00040829149700000722
The formula is:
Figure GDA00040829149700000723
i.e. air predictive value->
Figure GDA00040829149700000724
And a first difference->
Figure GDA00040829149700000725
Performing difference to obtain a third difference value; the third difference value is compared with the air flow rate of the manifold exhaust and the air flow rate of the air flow rate into the cylinder in the current period +.>
Figure GDA0004082914970000081
Adding to obtain the in-cylinder intake air amount of the next period>
Figure GDA0004082914970000082
Through the above steps, the operation of the engine is divided into a plurality of operation time periods, and the air flow rate discharged from the manifold and entering the cylinder is the current time period
Figure GDA0004082914970000083
And the air flow rate of the manifold discharged and into the cylinder in the previous period +.>
Figure GDA0004082914970000084
And the desired throttle flow for the current period +.>
Figure GDA0004082914970000085
And throttle flow at the throttle opening of the current period +.>
Figure GDA0004082914970000086
Then, the estimated value of the air flow rate of the throttle valve entering the manifold in the next time period is respectively obtained>
Figure GDA0004082914970000087
And the difference between the current and the last time period of the air flow rate of the manifold discharged and into the cylinder is the first difference +.>
Figure GDA0004082914970000088
Then the first difference +.>
Figure GDA00040829149700000819
And a predicted value of air flow into the manifold +.>
Figure GDA0004082914970000089
Taking the difference, the amount of charge or exhaust corresponding to whether the next period of the engine manifold is in charge or exhaust, and adding the amount of charge or exhaust to the air flow from the current period of the manifold to the cylinder, the resulting value is the amount of intake air in the next period of the cylinder, and thus, based on the desired throttle flow in the above manner
Figure GDA00040829149700000810
The method has the advantages that the air inflow in the manifold is estimated in consideration of different conditions of the engine under different working conditions, so that the air inflow in the cylinder in the next time period is estimated, errors caused by an air inflow estimation method of the multi-point injection engine are avoided, and the purpose of accurately estimating the dynamic air inflow of the single-point injection engine is achieved.
In some preferred embodimentsIn an example, the desired throttle flow for the current time period is calculated
Figure GDA00040829149700000811
And throttle flow at the throttle opening of the current period +.>
Figure GDA00040829149700000812
The method comprises the following steps of:
calculating an air flow rate of the manifold exiting and entering the cylinder for a current time period according to a first formula, wherein the first formula comprises:
Figure GDA00040829149700000813
wherein ,
Figure GDA00040829149700000814
air flow rate for manifold exhaust and into cylinder for current period EGR In order for the EGR rate to be desired,
Figure GDA00040829149700000815
the flow of the mixed gas into the cylinder for the current time period;
calculating an air flow rate of the manifold exiting and entering the cylinder for a previous period according to a second formula, wherein the second formula comprises:
Figure GDA00040829149700000816
wherein ,
Figure GDA00040829149700000817
for the last period of air flow rate from the manifold into the cylinder EGR-old For the last period the EGR rate is desired, +.>
Figure GDA00040829149700000818
For the amount of mixed gas that enters the cylinder for the previous time period.
Further, the engine air inlet flow estimating method further comprises the steps of calculating
Figure GDA00040829149700000921
The step of (a) calculating said->
Figure GDA0004082914970000091
Comprising the following steps:
establishing a manifold pressure model and acquiring manifold pressure sensor measurements for a current time period to estimate a current time period manifold pressure model value MAP est ；
MAP-based est Calculating the flow of the mixed gas into the cylinder through the inlet valve in the current time period by using a speed-density method
Figure GDA0004082914970000092
In some preferred embodiments, throttle flow is desired based on the current time period
Figure GDA0004082914970000093
And throttle flow at the throttle opening of the current period +.>
Figure GDA0004082914970000094
Obtaining the air flow predicted value of the throttle valve entering the manifold in the next period +.>
Figure GDA0004082914970000095
The method comprises the following steps:
desired throttle flow for a current time period
Figure GDA0004082914970000096
And throttle flow at throttle opening for the current time period
Figure GDA0004082914970000097
Difference is made to obtain a second difference +.>
Figure GDA0004082914970000098
For the second difference
Figure GDA0004082914970000099
Performing attenuation treatment to obtain an air flow predicted value +_of the throttle valve entering the manifold in the next time period>
Figure GDA00040829149700000910
Further, considering that the throttle valve is expected to change in the later time period, the calculation result is influenced, and therefore the second difference value is calculated
Figure GDA00040829149700000911
The method comprises the following specific steps:
201. desired throttle flow for a current time period
Figure GDA00040829149700000912
And throttle flow at the throttle opening of the current period +.>
Figure GDA00040829149700000913
Difference is made to obtain a second difference +.>
Figure GDA00040829149700000914
202. For the second difference
Figure GDA00040829149700000915
Performing attenuation treatment once to obtain attenuation value +.>
Figure GDA00040829149700000916
203. Judging the expected throttle flow in the current time period
Figure GDA00040829149700000917
Whether a change occurs;
206. if there is no change, the attenuation value is reduced
Figure GDA00040829149700000918
Air flow rate of throttle valve into manifold as next period of time estimated value +.>
Figure GDA00040829149700000919
204. If the throttle valve is changed, acquiring the expected throttle valve flow after the change of the current time period and the throttle valve flow under the throttle opening of the current time period after the change of the expected throttle valve flow, then taking the difference to obtain a difference value, and combining the difference value with an attenuation value
Figure GDA00040829149700000920
Adding to obtain a new second difference value;
205. taking the new attenuation value as an air flow predicted value of the throttle valve entering the manifold in the next time period
Figure GDA0004082914970000101
Wherein the engine has a process of moving from dynamic to steady state, the air flow predicted value into the manifold is calculated for each time period during the process of moving from dynamic to steady state>
Figure GDA0004082914970000102
Is decayed once and when the decay value is 0, then it is proved to be steady state, the gradient value of the change of the next time period from the current time period +.>
Figure GDA0004082914970000103
Air flow rate of manifold exhaust and intake into cylinder in the present period +.>
Figure GDA0004082914970000104
The difference between (1) and (2) is the air flow rate of the manifold exhaust and into the cylinder in the next time period>
Figure GDA0004082914970000105
An example is given below for illustration:
Figure GDA0004082914970000106
during the intake air flow rate changes to steady state, the intake air flow rate is attenuated once each cycle until the intake air flow rate is attenuated to be
Figure GDA0004082914970000107
If at->
Figure GDA0004082914970000108
In the decay process of (2), for example to +.>
Figure GDA0004082914970000109
In this case, the throttle opening degree +.>
Figure GDA00040829149700001010
The difference between the new desired throttle flow and the throttle flow at that time is +.>
Figure GDA00040829149700001011
The fresh air flow rate filled in the intake manifold becomes +.>
Figure GDA00040829149700001012
This value continues to filter the attenuation. The value obtained by attenuation of each cycle, namely the predicted value of fresh air flow filled in the intake manifold for the next cycle +.>
Figure GDA00040829149700001013
Further, filtering the second difference
Figure GDA00040829149700001014
Attenuation is performed.
In some preferred embodiments, the throttle flow at the throttle opening is calculated according to a third formula
Figure GDA00040829149700001015
Wherein the third formula comprises:
Figure GDA00040829149700001016
wherein ,Pin For throttle front pressure, P out Is the throttle back pressure, T in For the front temperature of throttle, A eff P is the effective cross-sectional area related to throttle opening 0 and T0 Is the pressure and temperature under standard conditions, R is the gas constant, P in this example 0 ＝101.3kPa，T 0 ＝20℃。
In some preferred embodiments, to ensure accuracy of the calculation under different engine operating conditions, a calibration correction is made to the third difference, i.e., the flow of air from the manifold into the cylinder during the next time period by the following equation
Figure GDA00040829149700001017
Figure GDA00040829149700001018
Where k is a calibration correction factor.
An engine intake air flow estimation system is also provided, comprising:
a first module for calculating the current and last time period of the air flow into the cylinder and obtaining the current time period of the air flow discharged from the manifold into the cylinder based on the current and last time period of the air flow
Figure GDA0004082914970000111
And the air flow rate of the manifold discharged and into the cylinder in the previous period +.>
Figure GDA0004082914970000112
Then difference is carried out on the two to obtain a first difference value +.>
Figure GDA0004082914970000113
A second module for calculating a desired throttle flow for the current time period
Figure GDA0004082914970000114
And throttle flow at the throttle opening of the current period +.>
Figure GDA0004082914970000115
Desired throttle flow based on the current time period>
Figure GDA0004082914970000116
And throttle flow at the throttle opening of the current period +.>
Figure GDA0004082914970000117
Obtaining the air flow predicted value of the throttle valve entering the manifold in the next period +.>
Figure GDA0004082914970000118
A third module for based on the first difference
Figure GDA0004082914970000119
Air flow predictive value->
Figure GDA00040829149700001110
And the current period of air flow rate of manifold exhaust and into cylinder +.>
Figure GDA00040829149700001111
Obtaining the cylinder intake air amount of the next period>
Figure GDA00040829149700001112
The storage medium comprises a stored program, wherein equipment where the storage medium is located is controlled to execute the engine air inlet flow estimating method when the program runs.
The principle of the present application:
(1) Dividing the operation of the engine into a plurality of operation time periods, and first the current time period is the air flow rate discharged from the manifold and into the cylinder
Figure GDA00040829149700001113
And the air flow rate of the manifold discharged and into the cylinder in the previous period +.>
Figure GDA00040829149700001114
And the desired throttle flow for the current period +.>
Figure GDA00040829149700001115
And throttle flow at the throttle opening of the current period +.>
Figure GDA00040829149700001116
Then, the estimated value of the air flow rate of the throttle valve entering the manifold in the next time period is respectively obtained>
Figure GDA00040829149700001117
And the difference between the current and the last time period of the air flow rate of the manifold discharged and into the cylinder is the first difference +.>
Figure GDA00040829149700001118
Then the first difference +.>
Figure GDA00040829149700001119
And an estimate of air flow into the manifold
Figure GDA00040829149700001120
Taking the difference, the air charge or exhaust amount corresponding to whether the manifold of the next period of the engine is in the air charge process or the air exhaust process, and adding the air charge or exhaust amount to the air flow discharged from the manifold and into the cylinder of the current period, the obtained value is the air intake amount in the cylinder of the next period, and therefore, the air intake amount is based on the expected throttle flow in the above manner>
Figure GDA00040829149700001121
The method has the advantages that the air inflow in the manifold is estimated in consideration of different conditions of the engine under different working conditions, so that the air inflow in the cylinder in the next time period is estimated, errors caused by an air inflow estimation method of the multi-point injection engine are avoided, and the purpose of accurately estimating the dynamic air inflow of the single-point injection engine is achieved.
(2) The change of a desired throttle valve is considered, and the calculation is carried out by matching with the air flow of the engine dynamically entering the manifold, so that the accuracy of estimating the dynamic air inlet flow is further improved.
The present application is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems) and computer program products according to embodiments of the application. It will be understood that each flow and/or block of the flowchart illustrations and/or block diagrams, and combinations of flows and/or blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks. In a typical configuration, the device includes one or more processors, memory, and a bus. May include input/output interfaces, network interfaces, and the like. The memory may include non-volatile memory in a computer readable medium, random access memory, and/or non-volatile memory, such as read-only memory or flash memory, and the memory includes at least one memory chip. Memory is an example of a computer-readable medium. Computer readable media, including both non-transitory and non-transitory, removable and non-removable media, may implement information storage by any method or technology. The information may be computer readable instructions, data structures, modules of a program, or other data. Examples of storage media for a computer include, but are not limited to, phase change memory, static random access memory, dynamic random access memory, other types of random access memory, read only memory, electrically erasable programmable read only memory, flash memory or other memory technology, read only optical disk read only memory, digital versatile disks or other optical storage, magnetic cassettes, magnetic tape magnetic disk storage or other magnetic storage devices, or any other non-transmission medium, which can be used to store information that can be accessed by a computing device. Computer-readable media, as defined herein, does not include transitory computer-readable media, such as modulated data signals and carrier waves.
In the description of the present application, it should be noted that the azimuth or positional relationship indicated by the terms "upper", "lower", etc. are based on the azimuth or positional relationship shown in the drawings, and are merely for convenience of description of the present application and simplification of the description, and are not indicative or implying that the apparatus or element in question must have a specific azimuth, be configured and operated in a specific azimuth, and thus should not be construed as limiting the present application. Unless specifically stated or limited otherwise, the terms "mounted," "connected," and "coupled" are to be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; can be directly connected or indirectly connected through an intermediate medium, and can be communication between two elements. The specific meaning of the terms in this application will be understood by those of ordinary skill in the art as the case may be.
It should be noted that in this application, relational terms such as "first" and "second" and the like are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Moreover, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one … …" does not exclude the presence of other like elements in a process, method, article, or apparatus that comprises the element.
The foregoing is merely a specific embodiment of the application to enable one skilled in the art to understand or practice the application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the application. Thus, the present application is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims (10)

1. An engine intake air flow estimation method is characterized by comprising the following steps:
based on the mixed gas flow entering the cylinder in the current time period and the previous time period, obtaining the air flow discharged by the manifold and entering the cylinder in the current time period and the previous time period, and carrying out difference on the air flow and the air flow to obtain a first difference value;
obtaining an air flow estimated value of the throttle valve entering the manifold in the next time period based on the expected throttle valve flow in the current time period and the throttle valve flow under the throttle valve opening in the current time period;
and obtaining the in-cylinder air inflow of the next time period based on the first difference value, the air flow predicted value and the air flow discharged by the manifold and entering the cylinder in the current time period.
2. The engine intake air flow estimation method according to claim 1, characterized in that:
calculating an air flow rate of the manifold exiting and entering the cylinder for a current time period according to a first formula, wherein the first formula comprises:
Figure FDA0003931927560000011
wherein ,
Figure FDA0003931927560000012
air flow rate for manifold exhaust and into cylinder for current period EGR For the desired EGR rate +.>
Figure FDA0003931927560000013
The flow of the mixed gas into the cylinder for the current time period;
calculating an air flow rate of the manifold exiting and entering the cylinder for a previous period according to a second formula, wherein the second formula comprises:
Figure FDA0003931927560000014
wherein ,
Figure FDA0003931927560000015
for the last period of air flow rate from the manifold into the cylinder EGR-old For the last period the EGR rate is desired, +.>
Figure FDA0003931927560000016
For the amount of mixed gas that enters the cylinder for the previous time period.
3. The engine intake air flow estimation method according to claim 2, characterized in that the engine intake air flow estimation method further includes calculating
Figure FDA0003931927560000017
The step of (a) calculating said->
Figure FDA0003931927560000018
Comprising the following steps:
establishing a manifold pressure model and acquiring manifold pressure sensor measurements for a current time period to estimate a current time period manifold pressure model value MAP est ；
Based on the MAP est Calculating the flow of the mixed gas into the cylinder through the inlet valve in the current time period by using a speed-density method
Figure FDA0003931927560000021
4. The engine intake air flow estimation method according to claim 1, wherein the air flow estimated value of the throttle valve into the manifold in the next period is obtained based on the desired throttle valve flow in the current period and the throttle valve flow at the throttle opening in the current period, specifically comprising the steps of:
the expected throttle flow in the current time period and the throttle flow under the throttle opening in the current time period are subjected to difference to obtain a second difference value;
and carrying out attenuation treatment on the second difference value to obtain an air flow predicted value of the throttle valve entering the manifold in the next time period.
5. The engine intake air flow estimation method according to claim 4, wherein the attenuation processing is performed on the second difference value to obtain an air flow estimated value of the throttle valve into the manifold for the next period of time, comprising the steps of:
performing attenuation treatment on the second difference value once to obtain an attenuation value;
judging whether the expected throttle valve flow changes in the current time period;
if the throttle valve is not changed, taking the attenuation value as an air flow predicted value of the throttle valve entering the manifold in the next time period;
if so, the expected throttle flow after the change of the current time period is different from the throttle flow under the throttle opening of the current time period, the attenuation value is added to obtain an updated second difference value, the updated second difference value is subjected to attenuation processing once to obtain a new attenuation value, and the new attenuation value is used as an air flow predicted value of the throttle entering the manifold in the next time period.
6. The engine intake air flow estimation method according to claim 4, wherein:
the second difference is attenuated by filtering.
7. The engine intake air flow estimation method according to claim 1, wherein the in-cylinder intake air amount for the next period is obtained based on the first difference value, the air flow amount estimated value, and the air flow amount that is manifold-discharged and taken into the cylinder for the current period, comprising the steps of:
performing difference on the air flow predicted value and the first difference value to obtain a third difference value;
and adding the third difference value and the air flow discharged by the manifold and entering the cylinder in the current time period to obtain the air inflow in the cylinder in the next time period.
8. The engine intake air flow estimation method according to claim 6, characterized by further comprising, after obtaining a third difference, before adding the third difference to the air flow rate of the manifold exhaust and intake into the cylinder for the current period, the steps of:
and correcting the third difference value by using a correction coefficient.
9. The engine intake air flow estimation method according to claim 1, characterized in that:
according to a third formula, calculating the throttle flow under the throttle opening
Figure FDA0003931927560000031
Wherein the third formula comprises:
Figure FDA0003931927560000032
wherein ,Pin For throttle front pressure, P out Is the throttle back pressure, T in Is of a gas saving typeFront door temperature, A eff R is a gas constant, P is an effective sectional area related to throttle opening 0 and T0 Is the pressure and temperature under standard conditions, P 0 ＝101.3kPa，T 0 ＝20℃。
10. An engine intake air flow estimation system, comprising:
the first module is used for obtaining the air flow discharged by the manifold and entering the cylinder in the current time period and the previous time period based on the air flow of the mixture entering the cylinder in the current time period and the previous time period, and obtaining a first difference value by differencing the air flow discharged by the manifold and the air flow entering the cylinder in the current time period and the previous time period;
a second module for obtaining an air flow estimated value of the throttle valve into the manifold in the next time period based on the expected throttle flow in the current time period and the throttle flow at the throttle opening in the current time period;
and a third module for obtaining an in-cylinder intake air amount for a next period based on the first difference, the air flow predicted value, and an air flow amount that is manifold-discharged and taken into the cylinder for the current period.
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