EP3810915A1

EP3810915A1 - Method for determining a power setpoint of a compressor of an internal combustion engine

Info

Publication number: EP3810915A1
Application number: EP19742429.4A
Authority: EP
Inventors: Moustansir Taibaly; Mathieu Selle
Original assignee: PSA Automobiles SA
Current assignee: Stellantis Auto SAS
Priority date: 2018-06-21
Filing date: 2019-05-13
Publication date: 2021-04-28
Also published as: WO2019243675A1; FR3082887B1; FR3082887A1

Abstract

The invention relates to a method for determining a power setpoint (Pcomp cons) of a compressor equipping an intake line connected to an internal combustion engine at an air distributor, the engine comprising a line for recirculating exhaust gases, the intake line comprising, downstream of the compressor, an air dosage valve, the power setpoint (Pcomp cons) of the compressor being determined on the basis of an air flow, said air flow being an air flow setpoint (Qair cons) obtained on the basis of the speed of the engine (N), the number of cylinders of the engine, the capacity of a single cylinder of the engine, the temperature (Tp) and the pressure (Pp) in the intake distributor, the supercharging pressure setpoint (Psural cons), the current supercharging pressure (Psural), the current rate of recirculating exhaust gas (Tegr), the specific constant of the gases in the intake distributor (rpi enum ), the filtered current volumetric efficiency (11 'vol).

Description

METHOD FOR DETERMINING A POWER SETPOINT OF AN INTERNAL COMBUSTION ENGINE COMPRESSOR

The present invention relates to the field of internal combustion engines. The invention relates more particularly to a method for determining a power setpoint of an internal combustion engine compressor.

Constraints due to standards, for example European standards known as Euro VI, relating to the levels of polluting emissions generated by the operation of internal combustion engines, are becoming more and more severe.

As the performance levels required for engine control functions are therefore more and more demanding, it is interesting to know the state of the system to be checked in stabilized and transient conditions. This knowledge currently involves the installation of sensors supplemented by modeling of the physical phenomena present. A specific quantity of the system can then be estimated via the measurement of the sensor and by the result of the modeling.

In particular in the case of an internal combustion engine with compression ignition equipped with a supercharging system such as a turbocharger, the estimation of the air flow which will pass through the compressor of the turbocharger is necessary to correctly control by example, the discharge valve, also commonly known as “waste gâte” in English. This estimate requires calculating the power that the turbine will have to provide to the compressor.

The power required for the compressor can be determined from the current air flow, however this implies

-a possible divergence because when the boost pressure will be higher than the setpoint, then the air flow achieved will be higher than expected. However, if the air flow rate is higher than expected then the pressure drops of the air filter and the charge air cooler will increase. The power required for the compressor will then increase, which will have the effect of increasing the boost pressure and therefore amplifying the phenomenon.

-A dynamic response of overeating. In fact, based on the current air flow, which is dependent on the boost pressure achieved, the calculation of the compressor power will increase when the boost pressure increase. To be more dynamic, the compressor power should be of a niche type, that it goes directly to the value that we see when we are on a stabilized point.

There is therefore a need to accurately estimate the power requested from the compressor,

An object of the present invention is to propose a method which makes it possible to improve the precision of estimation of the power required from the compressor of such a turbocharger.

To achieve this objective, there is provided according to the invention a method for determining a power setpoint of a compressor equipping an intake line connected to an internal combustion engine at an air distributor, the engine comprising an exhaust gas recirculation line, the intake line comprising, downstream of the compressor, an air metering valve for controlling the flow of air admitted into the engine, in which the compressor power setpoint is determined from an air flow,

characterized in that this air flow is an air flow instruction, this air flow instruction being obtained from the relation:

knew

plenum

ylunitary b ^ cylinder N

With:

-N, the engine speed,

No. _Cyiindre , the number of cylinder of the engine,

Cylindrical, the displacement of a single engine cylinder,

-Tp and Pp respectively the temperature and the pressure in the inlet distributor (9), -Psural_cons and Psural_cour respectively the boost pressure setpoint and the current boost pressure,

-T _egr , the current rate of recirculating exhaust gas,

-r _P ienum, the specific gas constant in the intake manifold,

- h ' _noΐ the filtered current volumetric efficiency.

The technical effect is to create a set air flow which is consistent with the set pressure of the boost pressure, which avoids the risk of divergence in air flow and boost pressure. Various additional characteristics can be provided, alone or in combination:

According to one embodiment, the current volumetric efficiency filtered by a low-pass filter is determined from the current volumetric efficiency.

According to one embodiment, the low-pass filter takes into account a filtering coefficient which depends on the difference between the filtered and unfiltered value of the current volumetric efficiency.

According to one embodiment, the filtering coefficient is obtained by means of a map which establishes this filtering coefficient as a function of the difference between the filtered and unfiltered value of the current volumetric efficiency.

According to one embodiment, the method is activated when the current rate of recirculating exhaust gas is less than or equal to 5%.

The invention also relates to an engine assembly comprising:

-an internal combustion engine

an air intake line equipped with a compressor and connected to the internal combustion engine at an air distributor, the intake line comprising downstream of the compressor an air metering valve for the control of the air flow admitted into the engine,

- an exhaust gas recirculation line,

characterized in that it comprises an electronic computer comprising the means of acquisition, of processing by software instructions stored in a memory as well as the control means required for implementing a method according to one of the variants described above.

The invention also relates to a vehicle comprising such an engine assembly for its movement.

Other particularities and advantages will appear on reading the following description of a particular, non-limiting embodiment of the invention, made with reference to the figures in which: - Figure 1 is a schematic representation of a heat engine according to the invention.

- Figure 2 is a schematic representation of the process of the invention.

FIG. 1 shows a heat engine 1, for example an internal combustion engine with compression ignition, comprising an engine block with at least one cylinder 2, for example here four cylinders, for combustion. Such a heat engine can equip a vehicle, for example a vehicle to allow movement thereof.

The heat engine 1 further comprises a computer, not shown, comprising the means of acquisition, of processing by software instructions stored in a memory as well as the control means required for implementing the method detailed below.

The heat engine 1 is connected to an air intake line 3 and to a burnt gas exhaust line 4. The heat engine 1 also comprises a turbocharger 5, with its compressor 6 arranged in the intake line and its turbine 7 disposed in the exhaust line 4. The intake line 3 also comprises an air metering valve 8 for controlling the flow of air admitted into the engine 1, which can for example be conventionally a throttle body, and a distributor 9 of air to the cylinders 2 of the engine. The intake line 3 may also include an air filter 10 placed upstream of the compressor 6 and a charge air cooler 11 placed downstream of the compressor 6.

The heat engine 1 also includes an exhaust gas recirculation line 12 connecting the exhaust line 4 to the intake line 3. The exhaust gas recirculation line 12 is connected at one of its ends to the exhaust line 4 by a nozzle located upstream of the turbine 7, relative to the direction of flow of the exhaust gases. The exhaust gas recirculation line 12 is connected at the other of its ends to the intake line 3 by a connection located downstream of the compressor 6, relative to the direction of circulation of the intake air. The exhaust gas recirculation line 12 conventionally comprises a valve 13 for metering the quantity of exhaust gas to be recirculated.

Figure 2 details the steps of the method of the invention. In block 20, the volumetric efficiency h _noί current is calculated. The volumetric efficiency corresponds to the ratio between the gas flow actually admitted into the engine, Qtotadmis, and the theoretical flow that can be admitted into the engine:

Qtotadmis

^ lvol

_Qtot theoretical _admjs

On the one hand:

Qtot _admitted Qair + Qegr

And,

Qair, the current air flow in line 3 of intake. This current air flow is for example measured by a flow meter,

Qegr, the recirculating exhaust gas flow.

The current rate of recirculating exhaust gas, T _egr , is given by the relation:

Qegr

x _egr = 100 X

Q ^tot admitted

In practice, this current rate of recirculating exhaust gas is estimated as a function of the current air flow rate, Qair, and of the engine operating point.

The gas flow rate actually admitted to the engine, Qtotadmis, is then written:

100

Qtot _admitted X Qa

100 - x _egr ^air

The theoretical total flow to the engine, VARtot th _ed _admitted orical ^'cor P ^{ond to:}

With:

N, the engine speed, which can be obtained by measurement using a speed sensor, No. _Cyiindre , the number of engine cylinders,

_Unit cylinder, the displacement of a single engine cylinder,

Pp, the pressure in the plenum, in other words in the intake manifold 9, which can be measured by means of a pressure sensor, Tp, the temperature in the plenum, which can be measured by a sensor or estimated by calculation,

ï ^" plenum ₃ the specific constant of the gases in the plenum,

The volumetric efficiency is then written as follows:

100

We assume here that the specific constant of the gases in the plenum is equal to that of the air:

^ plenum r _ajr —287 J / kg / K

This volumetric efficiency r | _vol is then filtered via a low-pass filter (block 23), the filtering value of which depends on the difference between the value of the volumetric efficiency h _no1 , and the value of the volumetric efficiency h ' _no i filtered. This difference between the unfiltered value and the filtered value of the volumetric efficiency is shown in FIG. 2 in block 21. From this difference, a filter coefficient is determined in block 22, which can be determined from a map which establishes the filter coefficient as a function of the difference between the unfiltered value and the filtered value of the yield. volumetric.

This filter makes it possible to attenuate the oscillations of the volumetric efficiency due to the various calculations.

In Figure 2, the target air flow is then calculated in block 24, as follows: setpoint

Q ^tot admitted ^ ^V ° 1 Q ^tot admitted theoretical

With the volumetric efficiency h ' _no i filtered, and

Q _tot admitted ^setpoint , the total gas flow setpoint to be admitted into the engine,

Qtot _admitted th _ed orical ° ^C ^nSlgne ^{'the eohd'} 9 ^{hq total flow rate of} 9 ^az can be admitted into the engine, Using the set plenum pressure, P _p ienum ^COnSlgne . ^N ° P ^was calculating total flow, VARtot _{admitted the0} America ^point corresponding to this pressure:

To calculate the setpoint plenum pressure: p setpoint _ p _ A D setpoint

^ plenum ^- sural_cons ^ “dispenser

With _ boost pressure setpoint, and, AP _dosing ^setpoint , the pressure deviation setpoint at the air metering device 8. This setpoint, AP _d0 ^{sor C0nsi3ne} , pressure deviation at the air metering unit 8 being impossible to predict, we assume that the current value corresponds to the set value:

"P set point _> p current _ p _ p

^ c _doser - ^ ï doser - r _S ural_cour * p

With P _p the current plenum pressure, and P _SU rai_coun ' ^{at the} current boost pressure, downstream of the compressor 6 and upstream of the metering device 8. This current boost pressure P _on ai_coun can be estimated via Qair, the air flow current in line 3 of intake, current plenum pressure, Pp, and the position of the butterfly valve 8.

The setpoint plenum pressure, P _p ienum ^C ° ^nSlgne _> is then written: p setpoint _ _p _ p _ p

rplenum ^r sural_cons v ^r sural_cour ^r p J

Or for the total flow: r> setpoint

^ totadmis r_cons

With T _egr ^setpoint , the recirculation exhaust gas rate setpoint. This recirculation exhaust gas rate setpoint being impossible to predict, we also assume that the current value corresponds to the setpoint:

_ deposit _

^L egr ^L egr

We then obtain for the set air flow, Q air_cons

100 - t, setpoint egr

Qt air cons 100 ° t _a DMIS

In short:

X Oylunit * Nbr ^e cylinder * N

Since the target air flow rate is directly linked to the target boost pressure, the risk of divergence is eliminated because we no longer depend on the boost pressure achieved in calculating the power requested from the compressor.

Advantageously, the method is used when there is exhaust gas recirculation for a range of exhaust gas rate in low recirculation, that is to say in a range less than or equal to 5%. Indeed, if the estimate of the exhaust gas recirculation rate is tainted with an error, this makes it possible to limit this error and therefore ultimately that of the power setpoint of the compressor 6.

In block 28, the power setpoint of the compressor 6 is determined, P _¥ mp ¥ ns. This power setpoint is obtained from the air flow setpoint, Q _a ir_cons _> the upstream and downstream pressure setpoints of the compressor, P _a m_com _P _cons and P av_comp_cons _{3 as} well as from Tam_comp ₃ the air temperature setpoint upstream of compressor 6:

With, ricomp e compressor efficiency,

c _Pajr , the heat capacity of the air,

y _air , adiabatic coefficient of air

The upper pressure value of the compressor, P _am _com _cons _P is determined at block 25 from the air flow setpoint Q _air _{_cons>} and taking ^into account the load loss induced by the air filter 10 .

The downstream pressure value of the compressor, P _av-COMP-cons is determined from the air flow setpoint Q _{air con} _s> taking ^into account the load loss induced by the charge air cooler 1 1 (block 26) and P _SU rai_cons J ^a boost pressure setpoint (block 27).

The invention makes it possible to create a set air flow which is consistent with the set plenum pressure.

The invention has the advantage of eliminating the risk of divergence in air flow and boost pressure which means that when the boost pressure increases then the air flow increases which tends to cause the control law to diverge because the power demand at compressor level increases. In addition, it makes it possible to have a power demanded from the compressor which is of the "slot" type when a torque slot is imposed on the engine, which makes it possible to improve the dynamics of the boost pressure.

This invention improves the quality of boost pressure and recirculating exhaust gas flow regulations, reducing the risk of oscillation and the response time of the boost pressure. This invention does not entail any additional material cost because it is a simple control command to set up.

Claims

1. Method for determining a power setpoint (Pcomp cons) of a compressor (6) fitted to an intake line (3) connected to an internal combustion engine (1) at an air distributor (9), the engine (1) comprising an exhaust gas recirculation line (12), the intake line comprising downstream of the compressor (6) an air metering valve (8) for controlling the air flow admitted into the engine (1), in which the power setpoint (Pcomp cons) of the compressor is determined from an air flow,

characterized in that this air flow is an air flow instruction (Qair cons), this air flow instruction (Qair cons) being obtained from the relation:

ylunitary X No. _C yj _jncjre XN

With:

-N, the engine speed,

No. _Cyiindre , the number of cylinder of the engine,

Cylindrical, the displacement of a single engine cylinder,

-Tp and Pp respectively the temperature and the pressure in the inlet manifold

(9)

-Psural_cons and Psural_cour respectively the boost pressure set point and the current boost pressure,

-Xegr, the current rate of exhaust gas in recirculation,

-r _P ienum, the specific gas constant in the intake manifold,

- I send you the filtered current volumetric efficiency.

2. Method according to claim 1, characterized in that one determines the current volumetric efficiency filtered (T | 'voi) by a low-pass filter (23) from the current volumetric efficiency (T | _V oi).

3. Method according to claim 2, characterized in that the low-pass filter (23) takes into account a filtering coefficient (22) which depends on the difference (21) between the filtered and unfiltered value of the current volumetric efficiency.

4. Method according to claim 3, characterized in that the filtering coefficient is obtained by means of a map which establishes this filtering coefficient as a function of the difference (21) between the filtered and unfiltered value of the current volumetric efficiency.

5. Method according to one of the preceding claims, characterized in that it is activated when the current rate of recirculating exhaust gas (Tegr) is less than or equal to 5%.

6. Motor assembly including

-an internal combustion engine (1),

an air intake line (3) equipped with a compressor (6) and connected to the internal combustion engine (1) at an air distributor (9), the intake line comprising at downstream of the compressor (6) an air metering valve (8) for controlling the air flow admitted into the engine (1),

-a line (12) for exhaust gas recirculation,

characterized in that it comprises an electronic computer comprising the means of acquisition, of processing by software instructions stored in a memory as well as the control means required for implementing a method according to any one of the preceding claims.

7. Vehicle, characterized in that it comprises an engine assembly according to the preceding claim for its movement.