WO2020011664A1

WO2020011664A1 - Method for operating an internal combustion engine with a high-pressure exhaust gas return

Info

Publication number: WO2020011664A1
Application number: PCT/EP2019/068087
Authority: WO
Inventors: Martin Hausmann; Thomas Bleile; Rene Huck; Wilhelm Blumendeller; Martin Hoerner; Alfried Schwarz; Christian Vigild; Daniel Röttger
Original assignee: Robert Bosch Gmbh; Ford Global Technologies, Llc
Priority date: 2018-07-13
Filing date: 2019-07-05
Publication date: 2020-01-16
Also published as: DE102018117002A1

Abstract

The invention relates to a method for operating an internal combustion engine (2) with a high-pressure exhaust gas return (HD-AGR), wherein a mass flow (ṁ _EGRHPOpt ) of a high-pressure exhaust gas return is determined, wherein the determined mass flow (ṁ _EGRHPOpt) of the high-pressure exhaust gas return is determined according to a first high-pressure exhaust gas return mass flow (ṁEGRHPThr), based on a throttle equation, and a second high-pressure exhaust gas return mass flow (ṁ_EGRHPBal), based on an air mass flow (ṁ ₂₁) and a ratio of mass concentrations, and used for operating the internal combustion engine (2).

Description

Method for operating an internal combustion engine with a high pressure

Abqasrückführunq

State of the art

The invention relates to a method for operating a

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 by means of an exhaust gas recirculation valve based on the control deviation between a target concentration and a corresponding measured concentration after a

Exhaust gas recirculation mixing point is controlled. Here, the

Oxygen concentration is a possible target value. Alternatively, the exhaust gas recirculation rate can be determined using 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.

DE 102010037650 A1 relates to an 02 control system (1) for one

Internal combustion engine (2). The internal combustion engine (2) has an intake passage (3) and an exhaust passage (4) and has a return device for filtered exhaust gas (5) for returning filtered exhaust gas (6) from the

Exhaust passage (4) to intake passage (3). The intake passage (3) has a first segment (3_1) upstream of an inflow of filtered exhaust gas (7) and a second segment (3_2) downstream of an inflow of filtered exhaust gas (7) and upstream to an engine inlet (9). A mixture of fresh air (8) and recycled filtered exhaust gas (23) can flow in the second segment (3_2). The 02 control system (1) can measure the 02 concentration in the second segment (3_2) of the intake passage (3) by regulating a pressure flow rate of recirculated filtered exhaust gas (23) regulate the recirculation device for filtered exhaust gas (5). In the second

An oxygen sensor (13) is arranged in segment (3_2) of the intake passage (3). The regulation of the 02 concentration is based on a detected 02 concentration in the mixture of fresh gas (8) and recirculated filtered exhaust gas (23) in the second segment (3_2) of the intake passage (3). The scheme can

done model-based.

DE 10201 1002553 A1 discloses a supercharged internal combustion engine (1)

- at least one cylinder (2),

- at least one intake line (4) belonging to an intake system (3) for supplying the at least one cylinder (2) with charge air,

- At least one exhaust pipe (7) for removing the exhaust gases, and

- At least one exhaust gas turbocharger (8) comprising a turbine (8b) arranged in the at least one exhaust line (7) and a compressor (8a) arranged in the at least one intake line (4), one

Exhaust gas recirculation (9) is provided, which comprises a return line (9a) which branches off from the exhaust line (7) downstream of the turbine (8b) and opens into the intake line (4) upstream of the compressor (8a).

The invention also relates to a method for operating such an internal combustion engine (1).

The aim is to provide a supercharged internal combustion engine (1) of the type mentioned above, in which the quality of the regulation for setting the feedback rate is improved.

This is achieved by an internal combustion engine (1) of the type mentioned, which is characterized in that

- Downstream of the junction of the return line (9a) in the intake line (4), a sensor (15) for detecting the concentration Ci ntake 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 a

Internal combustion engine presented with a high pressure exhaust gas recirculation, wherein a mass flow of a high pressure exhaust gas recirculation is determined, the determined mass flow of the high pressure exhaust gas recirculation depending on 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, 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 (e.g. of the exhaust gas lambda) in the control of the internal combustion engine.

It is advantageous if the ratio of the mass concentrations in

Dependence of a mass concentration on the high pressure exhaust gas recirculation, a mass concentration of an inflowing air mass and one

Mass concentration of the gas mixture is formed 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 particularly precisely based on the second HD-EGR mass flow

Determine 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, in steady-state operating states with small dynamics of the internal combustion engine, the EGR mass flow determined is based on the Concentration sensor and the fresh air mass flow is determined, since a high 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, due to the installation position downstream in the exhaust system, changes the operating state of the

Internal combustion engine can determine late. 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.

drawing

Below is the invention with reference to the accompanying

Drawings and described in more detail using exemplary embodiments. Show

1 is a schematic representation of an internal combustion engine with high-pressure exhaust gas recirculation,

Fig. 2 shows an exemplary sequence of the model for operating a

Internal combustion engine with a high pressure exhaust gas recirculation (HD-EGR). Description of the embodiments

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

The following is arranged in the air supply system 61 in the flow direction of the air 51: a first air mass sensor 10, a compressor 30 of an exhaust gas turbocharger 6, a charge air cooler 40, a second air mass sensor 50, a high-pressure throttle valve 60 and an internal combustion engine 2.

The following are arranged in the exhaust gas discharge 71 starting from the internal combustion engine 2 in the flow direction of the exhaust gas 52: a pressure sensor, an exhaust gas turbine 70, an exhaust gas aftertreatment system 80

Exhaust aftertreatment system 80 can, for. B. different

Exhaust emission control systems include, e.g. 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 turbine 70, i.e. on a high pressure side of the

Exhaust system 71, branches off from exhaust system 71 from a high-pressure exhaust gas recirculation line 46 (HD EGR line), which is upstream of internal combustion engine 2 and downstream of throttle valve 60

Fresh air system 61 opens, this opening is also referred to as a high-pressure _{mixing point} HD _mixing . Downstream of the internal combustion engine 2 there are an HD EGR cooler 43 with an HD EGR bypass 44, a temperature sensor 93 and an HD EGR valve 45 along the HD EGR line 46. B. a temperature sensor 93, a temperature T _EG RVI _V HPU _S between the HD EGR cooler 43 and the HD EGR valve 45 can be determined. Furthermore, a high-pressure exhaust gas recirculation mass flow m _EGRHP between the HD EGR valve 45 and the high-pressure exhaust gas recirculation _{mixing point} HD _MiSC h (HD EGR mixing point) can be determined by means of an air mass sensor. The sizes described can e.g. B. as sensor values or as model values available. 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 m ₁₀ between the air inlet and the compressor 30. In addition, a mass concentration sensor or a model can be used, for example

Fresh air mass concentration r _{x 12} between the air inlet and the

Compressor 30 can be determined.

Furthermore, an air mass flow m ₁₂ and a pressure p ₁₂ between the

Air mass sensor 10 and the compressor 30 determined. For this purpose, an air mass sensor and a pressure sensor can be provided, or alternatively the sizes are determined using corresponding models by means of the control device 100.

The second air mass sensor 50 determines an air mass flow m ₂₁ , a pressure p ₂₁ and a temperature T ₂₁ between the compressor 30 and the

High-pressure throttle valve 60, in particular at the location in front of the high-pressure throttle valve 60. The third air mass sensor 17 can have an air mass flow 2 ₂ , a pressure p ₂₂ and a mixing temperature T ₂₂ between the high-pressure throttle valve 60 and the engine intake valve 22, in particular at the location of the engine intake valve 22, determine.

Furthermore, between the HD _{mixing point} HD _MiSCh and the engine inlet _valve 22, a mass concentration of the mixed gas r _x E _G RM _IX HP consisting of the fresh air portion generated upstream of the compressor 30 and the returned high-pressure exhaust gas portions by means of a

Mass concentration sensor or a model determined. The mass concentration _{sensor is preferably} arranged downstream of the HD mixing point HD _MiSCh , so that the two mixed gas _portions 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. from sensor values or

Sensor values derived quantities are determined or available as model values. Furthermore, a can also be used for the sizes described single sensor installed. A control device 100 is provided to receive the aforementioned measured variables, to store them and to process them further.

2 shows the exemplary sequence of the method for operating the internal combustion engine 2 with high-pressure exhaust gas recirculation.

In a first step 500, a high-pressure exhaust gas recirculation mass flow based on a throttle equation (1) z. B. by a

Control device 100 determined.

This can preferably be carried out using the following formula:

, where TEGRVI _V HPU _S the temperature upstream of the HD EGR valve 45, p ₃ the pressure upstream of the high-pressure exhaust gas recirculation line 46, ar _{EGRHpV | V} the effective area of the HD EGR valve 45, c ₂ a scaling factor, and

a flow function as a function of 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.

In a step 510, 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) is preferably used for each of the input variables ^ EGRVIVHPUS P3. P22 ^{ur |} d ar _{EGRHpV | V} linearized and added quadratically.

, with a _Ps the standard deviation of the pressure p ₃ , s _R22 the standard deviation of the pressure p ₂₂ , ^CT ar _EGR v _ivHP

Standard deviation of effective

Cross-sectional area of the HD EGR valve 45 ar _{EGRHpV | V} , ^CT T _EGRVIVHPUS Standard deviation of the temperature upstream of the HD EGR valve 45 and the function f ₄ .

Then in a step 520 the uncorrected high-pressure exhaust gas recirculation mass flow nr _{EGRHPBa | Raw is} based on a

Mass flow balance preferably calculated using the following formula: mEGRHPBalRaw

(3)

, with rE _G RHP _O pt _{, f} ei the optimal high pressure exhaust gas recirculation mass flow calculated from the previous calculation step and the

Oxygen difference Diff ₀₂ multiplied by a gain factor ^. If there is no previous value available for control unit 100 for ^ EGRHPOP -I ^noc h, the initialization is initialized with 0 or with a predeterminable value. This is preferably done in the first calculation run

carried out.

The oxygen mass concentration Diff ₀₂ is determined from the difference between the measured oxygen mass concentration after the high-pressure exhaust gas recirculation mixing point r ^ ₂ f ^r , which is preferably determined by a sensor, and a modeled oxygen mass concentration after the high-pressure exhaust gas recirculation mixing point r ^ ₂ ⁰ ₂ , The modeled

oxygen concentration

is determined using an oxygen model based on the optimal high-pressure exhaust gas recirculation mass flow mE _G RHP _O pt. The gain factor Ki results from the linearization of the

Oxygen mass _balance and thus depends on the air mass flow m ₂ 1, the oxygen concentrations of the supplied air r _{X 2i} , the mass via the HD-EGR line 41 and after the high-pressure exhaust gas recirculation _{mixing point} HD _MiSCh .

A corrected HD EGR mass flow mE _G RHPBai is then determined in a step 530. The following formula can be used for this:

, with iE _G RHPBaiRaw the uncorrected high pressure exhaust gas recirculation mass flow, with m _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 m _{EGRHPBa |} corresponds stationary to the uncorrected high pressure exhaust gas recirculation mass flow and follows the dynamics of the high pressure exhaust gas recirculation mass flow iE _G RHPT _h r based on the throttle equation. The function g can be configured as a filter, preferably as a PT 1 filter. The time constant of the PT 1 filter can be varied. The high-pressure exhaust gas recirculation mass flow m _{EGRHPThr is preferably} based on the throttle _equation (1)

high pass filtered and the uncorrected high pressure exhaust gas recirculation mass flow iE _G RHPBaiRaw low pass filtered. The filtering serves to dampen feedback of the signals as well as undesired low ones

Filter out the frequency components of the high-pressure exhaust gas recirculation mass flow iE _G RHPT _h r based on the throttle equation (1). As a result, the share of the high-pressure exhaust gas recirculation mass flow iE _G RHPT _h r based on the throttle equation (1) and stationary the uncorrected high-pressure exhaust gas recirculation mass flow mE _G RHPBaiRaw dominates in the dynamic operating ranges of the internal combustion engine 2.

A standard deviation of the corrected high-pressure exhaust gas recirculation mass flow mE _G RHPBa _l is then determined in a step 540 ^{using the} following formula:

, where s ^m EGRHPBal is the standard deviation of the corrected high

_EGRHP exhaust gas recirculation mass _flow ,

Standard deviation of the fresh air mass flow m ₂₁ , the s _{Tc 22} standard deviation of the measured

Oxygen _mass concentration r _{x 22} after the high-pressure exhaust gas recirculation mixing point HD _MiSC h and

Standard deviation of

Oxygen _mass concentration r _{x 2i} . The oxygen mass balance is linearized for each input variable and the terms are then added quadratically. In a step 550, the optimal high-pressure exhaust gas recirculation mass flow Pi _EGRHPOpt is then _determined using the following equation: mEGRHPOpt

The factor ci is calculated using a function f ₅ based on the

Standard deviations of the high pressure exhaust gas recirculation mass flow

E _GRHPTh r based on the throttle _equation (1) and the corrected one

High pressure exhaust gas recirculation mass flow Pi _EGRHPB ai determined:

^{Cl ~} - ^ (^ EGRHPThr '^ EGRHPBal) (7)

The function f ₅ is designed such that the value of the

Standard deviation with the smaller standard deviation receives the higher weight. The factor c-i 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 in the

Transitions into and out of the operating points significant non-physical overshoots are avoided, so that the modeling method dominates, which is the smaller at the current operating point

Standard deviation.

The following system of equations is then solved in a step 560:

^ EGRHPOpt

, with p ₃ the pressure upstream of the HD EGR line 41, p ₂₂ the pressure downstream of the HD EGR line 41, T _EG RVI _V HPU _S the temperature before High pressure EGR valve 45 and the effective cross-sectional area ar _EGR vi _{vHP 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) of the pressures p ₃ and p ₂ 2, the temperature T _EG RVI _V HPU _S and the effective cross-sectional area ar _EGRV | _V HP of the HD EGR valve 45 can be corrected such that the throttle equation (1) is still satisfied with the new optimal mass flow. What is decisive for the distribution of the error is how large is 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.

In a step 570, based on the determined optimum

High pressure exhaust gas recirculation mass flow mE _G RHP _O pt using a 0 ₂ model a modeled oxygen mass concentration r _{X 22} after the high pressure exhaust gas recirculation _{mixing point} HD _MiSCh and a difference Diff ₀₂ between the current value of the measured oxygen mass concentration r and the determined value of the modeled oxygen _mass concentration r ^ ₂ formed. This difference Diff ₀₂ ensures that the corrected high pressure exhaust gas recirculation mass flow mE _G RHPBai stationary corresponds to the converted measured oxygen mass concentrations. The

Oxygen mass concentrations can be calculated as follows:

_. ^V X, 21 ^r x, EGRHP mix

mEGRHPBal ~ ^m 21

'X.EGRHPMix' X.EGRHP

, with m 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 returned 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 from the high pressure EGR feedback.

In a step 580, the control of the internal combustion engine (10) is then carried out with the determined value for the optimized high-pressure exhaust gas recirculation mass flow mE _G RHP _O pt 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, a target value for the high-pressure throttle valve 60 or a target value for the exhaust gas valve 81 can also be specified.

The process then continues in step 500.

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.

Claims

Expectations

1. A method for operating an internal combustion engine (2) with a high-pressure exhaust gas recirculation (HD-EGR), wherein a mass flow (m _EGRHPOpt ) of a high-pressure exhaust gas recirculation is determined, characterized in that the determined mass flow (m _EGRHPOpt ) of the high-pressure exhaust gas recirculation in

Dependency of a first high-pressure exhaust gas recirculation mass flow (™ - _EGRHPTh r) _> based on a throttle _equation , and a second high-pressure exhaust gas recirculation mass flow (m _EGRHPBai ), based on an air mass flow (m ₂₁ ) and a ratio of mass concentrations, determined and at Operating the internal combustion engine (2) is used.

2. The method 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 , _2i ) and a mass concentration of one from air and above the high pressure exhaust gas recirculation recirculated exhaust gas mixture (r _{x EGRMIXHP} ) is formed.

3. The method according to any one of the preceding claims, characterized

characterized that the mass concentrations

Are oxygen mass concentrations or mass concentrations of an inert gas.

4. The method according to any one of the preceding claims, characterized

characterized in that the ratio of the proportions of the first high-pressure exhaust gas recirculation mass flow {m _EGRHPThr ) and the second high-pressure exhaust gas recirculation mass flow (™. _EGRHPBai ) is determined as a function of an operating state of the internal combustion engine (2).

5. The method according to claim 4, characterized in that at

closed HD EGR valve and / or in a dynamic

Operating state of the internal combustion engine (2) the mass flow (m _EGRHPOpt ) is determined based on the first high-pressure exhaust gas recirculation mass flow m _EGRHPTh r).

6. The method 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).

7. The method according to claim 4, characterized in that in one

steady-state operating state of the internal combustion engine (2) the mass flow (™ - _EGRHPOpt ) is determined based on the second HD-EGR mass flow {m _EGRHPBai ).

8. The method according to claim 7, characterized in that the stationary operating state is an idling of the internal combustion engine (2).

9. Computer program which is set up to carry out a method according to one of claims 1 to 8.

10. Electronic storage medium with a computer program

Claim 9.

1 1. Device, in particular control device (100), which is set up to carry out a method according to one of claims 1 to 8.