DE102018117002A1 - Method for operating an internal combustion engine with a high-pressure exhaust gas recirculation - Google Patents

Abstract

Method for operating an internal combustion engine (2) with a high-pressure exhaust gas recirculation (HD-EGR), a mass flow (ṁ) of a high-pressure exhaust gas recirculation being determined, the determined mass flow (ṁ) of the high-pressure exhaust gas recirculation depending on a first high-pressure exhaust gas recirculation Mass flow (ṁ), based on a throttle equation, and a second high-pressure exhaust gas recirculation mass flow (ṁ), based on an air mass flow (ṁ) and a ratio of mass concentrations, is determined and used to operate the internal combustion engine (2).

Description

State of the art

The invention is based on a method for operating an internal combustion engine with a high-pressure exhaust gas recirculation.

Modern electronic engine controls for piston engines feature high-pressure exhaust gas recirculation for optimal control and regulation of the intake air and inert gases.

State of the art is that the exhaust gas recirculation rate is controlled by means of an exhaust gas recirculation valve based on the control deviation between a target concentration and a corresponding measured concentration after an exhaust gas recirculation mixing point. Here, the oxygen concentration represents a possible target value. Alternatively, the exhaust gas recirculation rate can be regulated by means of a model-based fresh air mass and exhaust gas recirculation rate control, wherein an exhaust gas recirculation mass flow is calculated based on a throttle equation.

• - mindestens einem Zylinder (2),
• - mindestens einer zu einem Ansaugsystem (3) zugehörigen Ansaugleitung (4) zur Versorgung des mindestens einen Zylinders (2) mit Ladeluft,
• - mindestens einer Abgasleitung (7) zur Abführung der Abgase, und
• - mindestens einem Abgasturbolader (8), der eine in der mindestens einen Abgasleitung (7) angeordnete Turbine (8b) und einen in der mindestens einen Ansaugleitung (4) angeordneten Verdichter (8a) umfaßt, wobei eine Abgasrückführung (9) vorgesehen ist, welche eine Rückführleitung (9a) umfaßt, die stromabwärts der Turbine (8b) aus der Abgasleitung (7) abzweigt und stromaufwärts des Verdichters (8a) in die Ansaugleitung (4) mündet.

Des Weiteren betrifft die Erfindung ein Verfahren zum Betreiben einer derartigen Brennkraftmaschine (1).
Es soll eine aufgeladene Brennkraftmaschine (1) der oben genannten Art bereitgestellt werden, bei der die Qualität der Regelung zur Einstellung der Rückführrate verbessert ist.
Erreicht wird dies durch eine Brennkraftmaschine (1) der genannten Art, die dadurch gekennzeichnet ist, dass

• - stromabwärts der Einmündung der Rückführleitung (9a) in die Ansaugleitung (4) ein Sensor (15) zur Erfassung der Konzentration Ci,intake der i-ten Komponente der Ladeluft im Ansaugsystem (3) vorgesehen ist

The DE 102010037650 A1 relates to an O2 control system ( 1 ) for an internal combustion engine ( 2 ). The internal combustion engine ( 2 ) has an intake passage ( 3 ) and an exhaust passage ( 4 ) and has a recirculation device for filtered exhaust gas ( 5 ) for recycling filtered exhaust gas ( 6 ) from the exhaust passage ( 4 ) to the intake passage ( 3 ). The intake passage ( 3 ) has a first segment ( 3_1 ) upstream to an inflow of filtered exhaust gas ( 7 ) and a second segment ( 3_2 ) downstream to an inflow of filtered exhaust gas ( 7 ) and upstream to an engine inlet ( 9 ) on. In the second segment ( 3_2 ) a mixture of fresh air ( 8th ) and recirculated filtered exhaust gas ( 23 ) flow. The O2 -Control system ( 1 ) the O2 concentration in the second segment ( 3_2 ) the intake passage ( 3 ) by regulating a pressure flow rate of recirculated filtered exhaust gas ( 23 ) through the filtered exhaust gas recirculation device ( 5 ) regulate. In the second segment ( 3_2 ) the intake passage ( 3 ) is an oxygen sensor ( 13 ) arranged. The regulation of the O2 concentration is based on a recorded O2 concentration in a mixture of fresh gas ( 8th ) and recirculated filtered exhaust gas ( 23 ) in the second segment ( 3_2 ) the intake passage ( 3 ). The regulation can be model-based.
The DE 102011002553 A1 discloses a supercharged internal combustion engine ( 1 ) With

• - at least one cylinder ( 2 )
• - at least one to an intake system ( 3 ) associated suction line ( 4 ) to supply the at least one cylinder ( 2 ) with charge air,
• - at least one exhaust pipe ( 7 ) to remove the exhaust gases, and
• - at least one exhaust gas turbocharger ( 8th ), the one in the at least one exhaust pipe ( 7 ) arranged turbine ( 8b ) and one in the at least one suction line ( 4 ) arranged compressor ( 8a ), with exhaust gas recirculation ( 9 ) is provided which has a return line ( 9a ) which is located downstream of the turbine ( 8b ) from the exhaust pipe ( 7 ) branches off and upstream of the compressor ( 8a ) in the suction line ( 4 ) flows out.

Furthermore, the invention relates to a method for operating such an internal combustion engine ( 1 ).
A supercharged internal combustion engine ( 1 ) of the type mentioned above, in which the quality of the regulation for setting the return rate is improved.
This is achieved by an internal combustion engine ( 1 ) of the type mentioned, which is characterized in that

• - downstream of the return line junction ( 9a ) in the suction line ( 4 ) a sensor ( 15 ) to record the concentration Ci, intake of the i-th component of the charge air in the intake system ( 3 ) is provided

Disclosure of the invention

In a first aspect, a method for operating an internal combustion engine with a high-pressure exhaust gas recirculation is presented, wherein a mass flow of a high-pressure exhaust gas recirculation is determined, the determined mass flow of the high-pressure exhaust gas recirculation as a function of a first high-pressure exhaust gas recirculation mass flow, based on a throttle equation , and a second high-pressure exhaust gas recirculation mass flow, based on an air mass flow and a ratio of mass concentrations, is determined and used to operate the internal combustion engine.

The method has the particular advantage that an optimized high-pressure exhaust-gas recirculation mass flow is determined as a function of the first high-pressure exhaust gas recirculation mass flow and the second high-pressure exhaust gas recirculation mass flow. In this way, an optimized control and regulation of the internal combustion engine can be carried out, so that an optimization of emissions is achieved.
Due to the division of the mass flow to be determined by the first and the second high-pressure exhaust gas recirculation mass flow, stationary and dynamic operating points can be determined particularly precisely.
The high-pressure exhaust gas recirculation models used are independent of one another, so that a particularly precise high-pressure exhaust gas recirculation mass flow can be determined by weighting. Another advantage is the disturbance variable compensation (eg the exhaust gas lambda) in the control of the internal combustion engine.

It is advantageous if the ratio of the mass concentrations is formed as a function of a mass concentration via the high-pressure exhaust gas recirculation, a mass concentration of an inflowing air mass and a mass concentration of the gas mixture after the HD-EGR mixing point.

It can further be provided that the mass concentrations are oxygen mass concentrations or mass concentrations of an inert gas.

In an advantageous development it can be provided that the ratio of the proportions of the first and the second mass flow is determined as a function of an operating state of the internal combustion engine.
Depending on the operating state, a more precise determination of the mass flow can thus be achieved.

It is advantageous if, with the HD EGR valve closed and / or in a dynamic operating state of the internal combustion engine, the mass flow is determined based on the first high-pressure exhaust gas recirculation mass flow. This is advantageous because in this state, a particularly precise determination of the mass flow based on the throttle equation can be achieved. In dynamic operating states and when the HD EGR valve is closed, it is particularly advantageous if the mass flow determined is determined based on the first HD EGR mass flow, since the mass concentration sensor delivers inaccurate values in these operating states. The calculation becomes more robust.

Furthermore, it can be provided that the dynamic operating state is an overrun operation or an acceleration operation of the internal combustion engine.

In an advantageous development, the mass flow is determined in a stationary operating state based on the second HD-EGR mass flow. In this operating state, the HD-EGR mass flow can be determined particularly precisely by the second HD-EGR mass flow, based on an air mass flow and a ratio of mass concentrations, since the tolerances of the concentration sensors are particularly small in this operating state and the calculation is precise ,

It is advantageous if the determined EGR mass flow is determined on the basis of the concentration sensor and the fresh air mass flow in stationary operating states with small dynamics of the internal combustion engine, since a high level of accuracy is guaranteed in these stationary operating points. The mass concentration sensor has high accuracy in these operating states. The HD-EGR mass flow model should trust the measured value of the concentration sensor in a stationary manner and with small dynamics of the internal combustion engine, since the mass concentration sensor can only determine operating state changes of the internal combustion engine late due to the installation position downstream in the exhaust system. In this way, overshoots can be avoided when determining the HD EGR mass flow.

It can be provided here that the stationary operating state is an idling of the internal combustion engine.

In further aspects, the invention relates to a device, in particular a control device and a computer program, which are set up, in particular programmed, for executing one of the methods. In a still further aspect, the invention relates to a machine-readable storage medium on which the computer program is stored.

list of figures

• 1 eine schematische Darstellung einer Brennkraftmaschine mit Hochdruck-Abgasrückführung,
• 2 einen beispielhaften Ablauf des Modells zum Betreiben einer Brennkraftmaschine mit einer Hochdruck-Abgasrückführung (HD-AGR).

The invention is described in more detail below with reference to the accompanying drawings and using exemplary embodiments. Show

• 1 1 shows a schematic illustration of an internal combustion engine with high-pressure exhaust gas recirculation,
• 2 an exemplary sequence of the model for operating an internal combustion engine with a high-pressure exhaust gas recirculation (HD-EGR).

Description of the embodiments

The 1 shows a schematic representation of the engine system 1 with an internal combustion engine 2 , the air through an air duct system 61 is supplied and exhaust gas can be returned via a high exhaust gas discharge.

In the air supply system 61 is in the direction of air flow 51 seen arranged the following: a first air mass sensor 10 , a compressor 30 of an exhaust gas turbocharger 6 , an intercooler 40 , a second air mass sensor 50 , a High-pressure throttle 60 and an internal combustion engine 2 ,

In the exhaust system 71 is based on the internal combustion engine 2 in the flow direction of the exhaust gas 52 Arranged the following: a pressure sensor, an exhaust gas turbine 70 , an exhaust after-treatment system 80 , The exhaust aftertreatment system 80 can z. B. include various exhaust gas purification systems, such as. B. a diesel particulate filter, a nitrogen oxide catalyst and a selective catalytic system with an SCR catalyst. A pressure p ₃ after the engine intake can be measured by means of the pressure sensor.

Upstream of the exhaust gas turbine 70 , ie on a high pressure side of the exhaust system 71 , branches from the exhaust system 71 a high pressure exhaust gas recirculation line 46 (HD EGR line) from upstream of the internal combustion engine 2 and the downstream of the throttle valve 60 into the fresh air system 61 flows, this mouth is also referred to as a high-pressure _{mixing point} HD _mixing . Downstream of the internal combustion engine 2 are located along the HD EGR line 46 an HD EGR cooler 43 with HD EGR bypass 44 , a temperature sensor 93 and an HD EGR valve 45 , By means of e.g. B. a temperature sensor 93 can be a temperature T _EGRVlvHPUs between the HD EGR cooler 43 and the HD EGR valve 45 be determined. Furthermore, a high-pressure exhaust gas recirculation mass flow ṁ _{EGRHP can be} between the HD EGR valve by means of an air mass sensor 45 and the high-pressure exhaust gas recirculation _{mixing point} HD _mixing (HD-EGR _{mixing point} ) can be determined. The sizes described can e.g. B. present as sensor values or as model values. The recirculation of exhaust gas serves to reduce the emissions of the internal combustion engine 2 ,

The first air mass sensor 10 determines a fresh air mass flow ṁ ₁₀ between the air inlet and the compressor 30 , In addition, for example by means of a mass concentration sensor or a model, a fresh air mass concentration r _{X, 12} between the air inlet and the compressor 30 be determined. Furthermore, an air mass flow ṁ ₁₂ and a pressure p ₁₂ between the air mass sensor 10 and the compressor 30 certainly. For this purpose, an air mass sensor and a pressure sensor can be provided, or alternatively the sizes are determined using corresponding models using the control unit 100 determined.

The second air mass sensor 50 determines an air mass flow ṁ ₂₁ , a pressure p ₂₁ and a temperature T ₂₁ between the compressor 30 and the high pressure throttle 60 , especially on site in front of the high pressure throttle valve 60 , The third air mass sensor 17 can an air mass flow ṁ ₂₂ , a pressure p ₂₂ and a mixing temperature T ₂₂ between the high pressure throttle valve 60 and the engine intake valve 22 , especially at the location of the engine intake valve 22 , determine.
There is also HD _mixing between the HD _{mixing point} and the engine intake valve 22 a mass concentration of the mixed gas r _{x, EGRMixHP} consisting of that upstream of the compressor 30 generated fresh air portion and the returned high-pressure exhaust gas components by means of a mass concentration sensor or a model. The mass concentration sensor is preferably arranged downstream of the HD _{mixing point} HD _Misch , so that the two mixed gas components have already been mixed well.
Alternatively or additionally, the mass concentration of the inert gas rate can also be used for the process. An inert gas rate is preferably to be understood as the proportion of the gas mixture at which the oxygen is completely burned.
The sizes described can e.g. B. can be determined from sensor values or values derived from sensor values or are available as model values. Furthermore, a single sensor can also be installed for the sizes described. A control unit 100 it is provided to receive the above-mentioned measured variables, to save them and to process them further.

In the 2 is the exemplary sequence of the method for operating the internal combustion engine 2 with high pressure exhaust gas recirculation, shown.

, wobei T_EGRVlvHPUs die Temperatur vor dem HD-AGR-Ventil 45, p₃ der Druck stromaufwärts der Hochdruck-Abgasrückführungs-Leitung 46, ar_EGRHPVlv die effektive Fläche des HD-AGR-Ventils 45, c₂ einem Skalierungsfaktor, und ψ $\left(\frac{p_{22}}{p_3}\right)$

eine Durchflussfunktion in Abhängigkeit des Drucks p₂₂ stromabwärts des HD-AGR-Ventils 45 und des Drucks p₃ stromaufwärts der Hochdruck-Abgasrückführungs-Leitung 46.In a first step 500 a high pressure exhaust gas recirculation mass flow is based on a throttle equation ( 1 ) z. B. by a control unit 100 determined.
This can preferably be carried out using the following formula: $$\begin{array}{c}{\dot{m}}_{\text{EGRHPThr}}={\mathrm{<figure-callout\; id="2"\; label="c"\; filenames="DE102018117002A1\_0017.png"\; state="\{\{state\}\}">c</figure-callout>}}_2\sqrt{\frac{1}{T_{\text{EGRVlvHPUs}}}}\times p_3\times {\text{ar}}_{\text{EGRHPVlv}}\\ \times \psi \left(\frac{p_{22}}{p_3}\right)\end{array}$$

where T _{EGRVlvHPUs is} the temperature _{upstream of} the HD EGR valve 45 , p _{3 is} the pressure upstream of the high-pressure exhaust gas recirculation line 46 , ar _{EGRHPVlv is} the effective area of the HD EGR valve 45 , c ₂ a scaling factor, and ψ $\left(\frac{p_{22}}{p_3}\right)$

a flow function depending on the pressure p ₂₂ downstream of the HD EGR valve 45 and the pressure p ₃ upstream of the high-pressure exhaust gas recirculation line 46 ,

,mit σ_{p 3} der Standardabweichung des Drucks p₃, σ_{p 22} der Standardabweichung des Drucks p₂₂, σ_{ar EGRVlvHP} der Standardabweichung der effektiven Querschnittsfläche des HD-AGR-Ventils 45 ar_EGRHPVlv, σ_{T EGRVlvHPus} der Standardabweichung der Temperatur vor dem HD-AGR-Ventil 45 und der Funktion f₄.In one step 510 becomes a standard deviation for the high pressure exhaust gas recirculation Mass flow is determined based on the throttle equation using the standard deviations of the input variables of the formula (1). For this purpose, the throttle equation ( 1 ) linearized for each of the input variables T _EGRVlvHPUs , p ₃ , p ₂₂ and ar _EGRHPVlv and added quadratically. $$\begin{array}{l}{\sigma }_{\dot{m}}{}_{{}_{\text{EGRHPThr}}}\\ =f_4\left({\sigma }_{p_3}.{\sigma }_{p_{22}}.{\sigma }_{{\text{ar}}_{\text{EGRVlvHP}}}.{\sigma }_{{\text{T}}_{\text{EGRVlvHPUs}}}\right)\end{array}$$

, with σ _{p 3} the standard deviation of the pressure p ₃ , σ _{p 22} the standard deviation of the pressure p ₂₂ , σ _{ar EGRVlvHP} the standard deviation of the effective cross-sectional area of the HD EGR valve 45 ar _EGRHPVlv , σ _{T EGRVlvHPus} the standard deviation of the temperature upstream of the HD EGR valve 45 and the function f ₄ .

, mit ṁ_EGRHPOpt,k-1 dem aus dem vorherigen Berechnungschritt errechneten optimalen Hochdruck-Abgasrückführungs-Massenstrom und der Sauerstoffdifferenz Diff_O2 multipliziert mit einem Verstärkungsfaktor K₁. Falls für ṁ_EGRHPOpt,k-1 noch kein vorheriger Wert im Steuergerät 100 verfügbar sein sollte, wird mit einem Startwert gleich 0 oder mit einem vorgebbaren Wert initialisiert. Dies wird vorzugsweise im ersten Berechnungsdurchlauf durchgeführt.
Die Sauerstoffmassenkonzentration Diff_O2 wird aus der Differenz zwischen der gemessenen Sauerstoffmassenkonzentration nach der Hochdruck-Abgasrückführ-Mischstelle $r_{\text{x}\mathrm{,22}}^{\text{Snsr}},$

welche vorzugsweise durch einen Sensor ermittelt wird, und einer modellierten Sauerstoffmassenkonzentration nach der Hochdruck-Abgasrückführ-Mischstelle $r_{x\mathrm{,22}}^{\text{Mod}}$

ermittelt. Die modellierte Sauerstoffkonzentration $r_{x\mathrm{,22}}^{\text{Mod}}$

wird mittels eines Sauerstoffmodells basierend auf dem optimalen Hochdruck-Abgasrückführungs-Massenstrom ṁ_EGRHPOpt ermittelt.
Der Verstärkungsfaktor K₁ ergibt sich aus der Linearisierung der Sauerstoffmassenbilanz und hängt damit von dem Luftmassenstrom ṁ₂₁, den Sauerstoffkonzentrationen der zugeführten Luft r_x,21, der Masse über die HD-AGR-Leitung 41 und nach der Hochdruck-Abgasrückführ-Mischstelle HD_Misch ab.Then in one step 520 the uncorrected high pressure exhaust gas recirculation mass flow ṁ _EGRHPBalRaw based on a mass flow _balance preferably calculated according to the following formula: $$\begin{array}{l}{\dot{m}}_{\text{EGRHPBalRaw}}\\ ={\dot{m}}_{\text{EGRHPOpt}\text{.}k\text{-1}}+K_1\\ \cdot {\text{<figure-callout id="2" label="Diff O" filenames="DE102018117002A1\_0017.png" state="{{state}}">Diff </figure-callout>}}_O\end{array}$$

, with ṁ _{EGRHPOpt, k-1} the optimal high pressure exhaust gas recirculation mass flow calculated from the previous calculation _step and the oxygen difference Diff _O2 multiplied by a gain factor K ₁ . If for ṁ _{EGRHPOpt, k-1} there is no previous value in the control unit 100 should be available, is initialized with a start value equal to 0 or with a specifiable value. This is preferably carried out in the first calculation run.
The oxygen mass concentration Diff _O2 is the difference between the measured oxygen mass concentration after the high-pressure exhaust gas recirculation mixing point $r_{\text{x}\mathrm{,\; 22}}^{\text{Snsr}}.$

which is preferably determined by a sensor, and a modeled oxygen mass concentration after the high-pressure exhaust gas recirculation mixing point $r_{x\mathrm{,\; 22}}^{\text{Mod}}$

determined. The modeled oxygen concentration $r_{x\mathrm{,\; 22}}^{\text{Mod}}$

is determined using an oxygen model based on the optimal high-pressure exhaust gas recirculation mass flow ṁ _EGRHPOpt .
The gain factor K ₁ results from the linearization of the oxygen mass balance and thus depends on the air mass flow ṁ ₂₁ , the oxygen concentrations of the supplied air r _{x, 21} , the mass via the HD EGR line 41 and after the high pressure exhaust gas recirculation _{mixing point} HD _Misch .

, mit ṁ_EGRHPBalRaw dem unkorrigierten Hochdruck-Abgasrückführungs-Massenstrom, mit ṁ_EGRHPThr dem Hochdruck-Abgasrückführungs-Massenstrom basierend auf der Drosselgleichung (1) und mit der Funktion g. Der korrigierte Hochdruck-Abgasrückführungs-Massenstrom ṁ_̇EGRHPBal entspricht stationär dem unkorrigierten Hochdruck-Abgasrückführ-Massenstrom und folgt der Dynamik des Hochdruck-Abgasrückführ-Massenstroms ṁ_EGRHPThr basierend auf der Drosselgleichung. Hierbei kann die Funktion g als ein Filter, vorzugsweise als ein PT1-Filter, ausgestaltet sein. Dabei kann die Zeitkonstante des PT1-Filters variiert werden. Vorzugsweise wird der Hochdruck-Abgasrückführungs-Massenstrom ṁ_EGRHPThr basierend auf der Drosselgleichung (1) hochpassgefiltert und der unkorrigierte Hochdruck-Abgasrückführungs-Massenstrom ṁ_EGRHPBalRaw tiefpassgefiltert. Die Filterung dient hierbei dafür, um Rückkopplungen der Signale zu dämpfen sowie ungewünschte niedrige Frequenzanteile des Hochdruck-Abgasrückführungs-Massenstroms ṁ_EGRHPThr basierend auf der Drosselgleichung (1) herauszufiltern. Hierdurch dominiert im dynamischen Betriebsbereichen der Brennkraftmaschine 2 der Anteil des Hochdruck-Abgasrückführungs-Massenstroms ṁ_EGRHPThr basierend auf der Drosselgleichung (1) und stationär der unkorrigierte Hochdruck-Abgasrückführungs-Massenstrom ṁ_EGRHPBalRaw.In one step 530 a corrected HD EGR mass flow ṁ _EGRHPBal is then determined. The following formula can be used for this: $$\begin{array}{l}{\dot{m}}_{\text{EGRHPBal}}\\ =G\left({\dot{m}}_{\text{EGRHPBalRaw}\text{.}}{\dot{m}}_{\text{EGPHPThr}}\right)\end{array}$$

, with ṁ _EGRHPBalRaw the uncorrected high pressure exhaust gas recirculation mass flow, with ṁ _EGRHPThr the high pressure exhaust gas recirculation mass flow based on the throttle equation ( 1 ) and with the function g. The corrected high pressure exhaust gas recirculation mass flow ṁ _̇EGRHPBal stationary corresponds to the uncorrected high pressure exhaust gas recirculation mass flow and follows the dynamics of the high pressure exhaust gas recirculation mass flow ṁ _EGRHPThr based on the throttle _equation . The function g can be configured as a filter, preferably as a PT1 filter. The time constant of the PT1 filter can be varied. The high-pressure exhaust gas recirculation mass flow ṁ _{EGRHPThr is preferably} based on the throttle _equation ( 1 ) high pass filtered and the uncorrected high pressure exhaust gas recirculation mass flow ṁ _EGRHPBalRaw low pass filtered. The filtering serves to dampen feedback of the signals as well as undesired low frequency components of the high pressure exhaust gas recirculation mass flow ṁ _EGRHPThr based on the throttle _equation ( 1 ) to filter out. This dominates in the dynamic operating ranges of the internal combustion engine 2 the proportion of the high pressure exhaust gas recirculation mass flow ṁ _EGRHPThr based on the throttle _equation ( 1 ) and stationary the uncorrected high pressure exhaust gas recirculation mass flow ṁ _EGRHPBalRaw .

,wobei σ_{ṁ EGRHPBal} die Standardabweichung des korrigierten Hoch-Abgasrückführungs-Massenstroms ṁ_EGRHP, σ_{ṁ 21} die Standardabweichung des Frischluftmassenstroms ṁ₂₁, die σ_{r x,22} Standardabweichung der gemessenen Sauerstoffmassenkonzentration r_x,22 nach der Hochdruck-Abgasrückführ-Mischstelle HD_Misch und σ_{r x,21} die Standardabweichung der Sauerstoffmassenkonzentration r_x,21. Die Sauerstoffmassenbilanz wird für jede Eingangsgröße linearisiert und die Terme anschließend quadratisch addiert.Then in one step 540 a standard deviation of the corrected high pressure exhaust gas recirculation mass flow ṁ _{EGRHPBal is determined} using the following formula: $$\begin{array}{l}{\sigma }_{\dot{m}}{}_{{}_{\text{EGRHPBal}}}\\ =f_2\left({\sigma }_{m_{21}}.{\sigma }_{r_{O2.22}}.{\mathrm{<figure-callout\; id="2"\; label="\sigma \; r\; O"\; filenames="DE102018117002A1\_0017.png"\; state="\{\{state\}\}">\sigma \; </figure-callout>}}_{r_O}.{\sigma }_{r_{x\mathrm{,\; 21}}}\right)\end{array}$$

, where σ _{ṁ EGRHPBal} the standard deviation of the corrected high exhaust gas recirculation mass flow ṁ _EGRHP , σ _{ṁ 21} the standard deviation of the fresh air mass flow ṁ ₂₁ , the σ _{r x 22} Standard deviation of the measured oxygen mass concentration r _{x, 22} after the high pressure exhaust gas recirculation _{mixing point} HD _Misch and σ _{r x 21} the standard deviation of the oxygen mass concentration r _{x, 21} . The oxygen mass balance is for each input variable linearized and the terms then added together quadratically.

In one step 550 the optimal high-pressure exhaust gas recirculation mass flow ṁ _EGRHPOpt is then _determined using the following equation: $$\begin{array}{l}{\dot{m}}_{\text{EGRHPOpt}}\\ =c_1*{\dot{m}}_{\text{EGRGHPThr}}+\left(1-c_1\right)\\ *{\dot{m}}_{eGRHPBal}\end{array}$$

The factor c ₁ is calculated using a function f ₅ based on the standard deviations of the high pressure exhaust gas recirculation mass flow ṁ _EGRHPThr based on the throttle _equation ( 1 ) and the corrected high pressure exhaust gas recirculation mass flow ṁ _EGRHPBal : $$c_1=f_5\left({\sigma }_{{\dot{m}}_{\text{EGRHPThr}}}.{\sigma }_{{\dot{m}}_{\text{EGRHPBal}}}\right)$$

The function f ₅ is designed in such a way that the value of the standard deviation with the smaller standard deviation is given greater weight. The factor c ₁ is preferably a value between 0 and 1. By taking into account the tolerances or the standard deviations of the two mutually independent modeling methods for the high-pressure recirculation mass flow, an optimal high-pressure exhaust gas recirculation mass flow can be determined. By means of the weighting, significant non-physical overshoots can be avoided in the transitions into and out of the operating points, so that the modeling method dominates, which has the smaller standard deviation at the current operating point.

, mit p₃ der Druck stromaufwärts der HD-AGR-Leitung 41, p₂₂ dem Druck stromabwärts der HD-AGR-Leitung 41, T_EGRVlvHPUs der Temperatur vor dem Hochdruck-AGR-Ventil 45 und der effektiven Querschnittsfläche ar_EGRVlvHP des HD-AGR-Ventils 45 und den dazugehörigen Fehlern. Vorzugsweise ist die Funktion f₇ ein Kalmanfilter, wobei die ursprünglichen Werte der Drosselgleichung (1) von den Drücken p₃ und p₂₂, der Temperatur T_EGRVlvHPUs und der effektiven Querschnittsfläche ar_EGRVlvHP des HD-AGR-Ventils 45 derart korrigiert werden, dass mit dem neuen optimalen Massenstrom immer noch die Drosselgleichung (1) erfüllt ist. Entscheidend für die Verteilung des Fehlers ist, wie groß die Auswirkung der Standardabweichungen der Eingangsgrößen auf den Massenstrom zum jeweiligen Betriebspunkt der Brennkraftmaschine 2 sind.In one step 560 the following system of equations is then solved: $$\begin{array}{l}{\dot{m}}_{\text{EGRHPOpt}}\\ =f_7(p_3+p_{err.p3}.p22+p_{err.p22}.T\text{EGRVIvHPUs}\\ +T_{\text{Err}.T_{\text{EGRVIvHPUs}}.}{\text{ar}}_{\text{EGRVIvHP}}+{\text{ar}}_{\text{Err}\text{, a}{\text{r}}_{\text{EGRVIvHP}})}\end{array}$$

, with p ₃ the pressure upstream of the HD EGR line 41 , p ₂₂ the pressure downstream of the HD EGR line 41 , T _EGRVlvHPUs the temperature _upstream of the high pressure EGR valve 45 and the effective cross-sectional area ar _{EGRVlvHP of} the HD EGR valve 45 and the associated errors. The function f ₇ is preferably a Kalman filter, the original values of the throttle equation ( 1 ) from the pressures p ₃ and p ₂₂ , the temperature T _EGRVlvHPUs and the effective cross-sectional area ar _{EGRVlvHP of} the HD EGR valve 45 are corrected in such a way that the throttle equation ( 1 ) is satisfied. What is decisive for the distribution of the error is how large the effect of the standard deviations of the input variables on the mass flow at the respective operating point of the internal combustion engine 2 are.

nach der Hochdruck-Abgasrückführ-Mischstelle HD_Misch und eine Differenz Diff_O2 zwischen dem aktuellen Wert der gemessenen Sauerstoffmassenkonzentration $r_{x\mathrm{,22}}^{\text{sens}}$

mit dem ermittelten Wert der modellierten Sauerstoffmassenkonzentration $r_{x\mathrm{,22}}^{Mod}$

gebildet. Diese Differenz Diff_O2 stellt dabei sicher, dass der korrigierte Hochdruck-Abgasrückführ-Massenstrom ṁ_EGRHPBal stationär den umgerechneten gemessenen Sauerstoffmassenkonzentrationen entspricht. Die Sauerstoffmassenkonzentrationen können hierbei folgendermaßen berechnet werden: $${\dot{m}}_{EGRHPBal}={\dot{m}}_{21}\cdot \frac{r_{x\mathrm{,21}}-r_{x,EGRHPMix}}{r_{x,EGRHPMix}-r_{x,EGRHP}}$$

, mit ṁ₂₁ dem Luftmassenstrom, r_x,21 der Massenkonzentration der zugeführten Luft, r_x,EGRHP der Massenkonzentration des über die Hochdruck-Abgasrückführung zurückgeführten Abgases, r_x,EGRHPMix der gemessene Massenkonzentration des gemischten Gases aus der zugeführten Luft und rückgeführten Abgas aus der Hochdruck-Abgasrück-Rückführung.In one step 570 then a modeled oxygen mass _{concentration} based on the determined optimal high pressure exhaust gas recirculation mass flow ṁ _EGRHPOpt using an O ₂ model $r_{x\mathrm{,\; 22}}^{\text{Mod}}$

after the high pressure exhaust gas recirculation _{mixing point} HD _Misch and a difference Diff _O2 between the current value of the measured oxygen mass concentration $r_{x\mathrm{,\; 22}}^{\text{sens}}$

with the determined value of the modeled oxygen mass concentration $r_{x\mathrm{,\; 22}}^{MOd}$

educated. This difference Diff _O2 ensures that the corrected high pressure exhaust gas recirculation mass flow ṁ _EGRHPBal stationary corresponds to the converted measured oxygen mass concentrations. The oxygen mass concentrations can be calculated as follows: $${\dot{m}}_{eGRHPBal}={\dot{m}}_{21}\cdot \frac{r_{x\mathrm{,\; 21}}-r_{x.eGRHPMix}}{r_{x.eGRHPMix}-r_{x.eGRHP}}$$

, with ṁ ₂₁ the air mass flow, r _{x, 21} the mass concentration of the supplied air, r _{x, EGRHP} the mass concentration of the exhaust gas recirculated via the high pressure exhaust gas recirculation, r _{x, EGRHPMix} the measured mass concentration of the mixed gas from the supplied air and recirculated exhaust gas the high pressure exhaust gas recirculation.

In one step 580 the control of the internal combustion engine is then determined with the determined value for the optimized high pressure exhaust gas recirculation mass flow ṁ _EGRHPOpt ( 10 ) executed such that a target value for the high pressure exhaust gas recirculation valve 39 is specified.
Alternatively, in addition to the high pressure exhaust gas recirculation valve 45 also a target value for the high pressure throttle valve 60 or a target value for the exhaust flap 81 be specified.
Then in step 500 continued.

Alternatively or additionally, the mass concentration of the inert gas rate can also be used instead of the oxygen mass concentration.
An inert gas rate is preferably to be understood as the proportion of the gas mixture at which the oxygen is completely burned.

QUOTES INCLUDE IN THE DESCRIPTION

This list of documents listed by the applicant has been generated automatically and is only included for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• DE 102010037650 A1 [0004]
• DE 102011002553 A1 [0004]

Claims (11)

Method for operating an internal combustion engine (2) with a high-pressure exhaust gas recirculation (HD-EGR), a mass flow (ṁ _EGRHPOpt ) of a high-pressure exhaust gas recirculation being determined, characterized in that the determined mass flow (ṁ _EGRHPOpt ) of the high-pressure exhaust gas recirculation as a function of a first high-pressure exhaust gas recirculation mass flow (ṁ _EGRHPThr ), based on a throttle _equation , and a second high-pressure exhaust gas recirculation mass flow (ṁ _EGRHPBal ), based on an air mass flow (ṁ ₂₁ ) and a ratio of mass concentrations, determined and for operating the internal combustion engine (2) is used. Procedure according to Claim 1 , characterized in that the ratio of the mass concentrations as a function of a mass concentration via the high-pressure exhaust gas recirculation (r _{x, EGRHP} ), a mass concentration of an inflowing air mass (r _{x, 21} ) and a mass concentration of an exhaust gas recirculated from air and via the high-pressure exhaust gas recirculation formed mixture (r _{x, EGRMixHp} ) is formed. Method according to one of the preceding claims, characterized in that the mass concentrations are oxygen mass concentrations or mass concentrations of an inert gas. Method according to one of the preceding claims, characterized in that the ratio of the proportions of the first high-pressure exhaust gas recirculation mass flow (ṁ _EGRHPThr ) and the second high-pressure exhaust gas recirculation mass flow (ṁ _EGRHPBal ) is determined as a function of an operating state of the internal combustion engine (2). Procedure according to Claim 4 , characterized in that when the HD EGR valve is closed and / or in a dynamic operating state of the internal combustion engine (2), the mass flow (ṁ _EGRHPOpt ) is determined based on the first high-pressure exhaust gas recirculation mass flow (ṁ _EGRHPThr ). Procedure according to Claim 5 , characterized in that the dynamic operating state is an acceleration process or a coasting operation of the internal combustion engine (2). Procedure according to Claim 4 Characterized in that the mass flow (ṁ _EGRHPOpt) is determined based on the second HD EGR mass flow (ṁ _EGRHPBal) in a steady operating state of the internal combustion engine (2). Procedure according to Claim 7 , characterized in that the stationary operating state is an idling of the internal combustion engine (2). Computer program which is set up to carry out a method according to one of the Claims 1 to 8th perform. Electronic storage medium with a computer program Claim 9 , Device, in particular control device (100), which is set up to implement a method according to one of the Claims 1 to 8th perform.

Images