METHOD FOR OPERATING AUTO IGNITION COMBUSTION ENGINE

• US 20100131171A1
• Filed: 11/25/2009
• Published: 05/27/2010
• Est. Priority Date: 11/27/2008
• Status: Active Grant

• Current Assignee: Vitesco Technologies GmbH (Continental AG)
• Original Assignee: Continental Automotive GmbH (Continental AG)
• Inventors: Müller, Karl, Varoquie, Bertrand
• Granted Patent: US 8,463,530 B2
• Time in Patent Office: Days
• US Class Current: 701/102
• CPC Class Codes: F02D 2250/18 Control of the engine output torque
• CPC Class Codes: F02D 41/1406 with use of a optimisation method, e.g. iteration
• CPC Class Codes: F02D 41/3035 a mode being the premixed charge compression-ignition mode

Abstract

A low computation method for operating auto ignition combustion engines, in which outputs, in particular a requested torque set point TQI_SP is directly linked to an injected fuel mass flow distribution, to the EGR rate and the air control by taking into account engine out emissions & drivability constrains by using a multi-objective optimization method. A method to monitor in the embedded controller the indicated torque, TQI is also proposed.

Claims

1. A method for operating auto ignition combustion engines, comprising the step of directly linking outputs to an injected fuel mass flow distribution and to an injection timing by taking into account engine out emissions and/or drivability constraints by using an optimization method.

2. The method according to claim 1, wherein the output is at least one of a requested torque set point TQI_SP and an estimation of a torque realization TQI.

3. The method according to claim 1, wherein the torque realization set point directly linked to an injected fuel mass flow distribution and to an injection timing are optimizing by taking into account at least one of engine out emissions and drivability constraints.

4. The method according to claim 1, wherein the indicated torque realization used for torque production monitoring is TQI=η

*30* LHV*MF/(N*π

), where MF is the fuel mass injected per combustion cycle [g/stroke] dedicated to torque production, where LHV is the fuel combustion lowest heating value [J/g], where N is the engine speed, and where η

is the global fuel to torque conversion efficiency.

5. The method according to claim 4, wherein the global fuel to torque conversion efficiency η

is given by the product of the combustion efficiency η

_comb and of the engine mechanical efficiency η

_mech with η

=η

_comb*η

_mech.

6. The method according to claim 1, wherein an overall fuel mass injected in a combustion chamber for lean combustion is burnt during the auto-ignition process if the start of injections SOI are calibrated to compensate the injector response, the auto ignition delay and the EGR effect on the auto ignition delay, ideally thus the combustion efficiency variation η

_comb can be ignored and fixed to η

_comb=1, at least for a selected SOI bandwidth that respects engine out emission constrains.

7. The method according to claim 1, wherein a mechanical efficiency η

_mech is used in an embedded software as a 2D look up table depending both on the engine speed N and the engine cooling temperature TCO, η

_mech=η

_mech (N, TCO).

8. The method according to claim 1, wherein a global equivalence ratio Φ

=(MF/MA)/(MF/MA)_stoich=(MF/MA)*α

_stoich is used to adapt the air mass flow via the air path control and turbocharger position control because MA the air mass flow is continuously measured on modern engine management systems and MF is known by in the embedded software.

9. The method according to claim 1, wherein the realisation of the indicated torque set point TQI_SP is done considering several constrains, whereas these constrains are selected from the group consisting of:

maximum indicated torque production (unit Nm);

minimum noise ie slower increase of the in-cylinder pressure (unit DbA or bar.s<sup>−

1</sup>);

minimum emission of Nitrous oxides [NOx];

minimum emission of Soot [Soot];

minimum emission of carbon monoxide [CO];

minimum emission of unburnt hydrocarbons [HC]; and

minimum fuel consumption and hence minimum carbon monoxide emission [CO2], where [i] is the emission of a specie i in g/stroke or g/km.

10. The method according to claim 1, wherein optimized realization TQI_SP is found by minimizing the error of a multi-objective function J for the overall engine operating points, with

J=W_TQI—

_SP*TQI_—

SP/TQI<sub>—

SP</sub>^ref+W_soot*[Soot]/[Soot]^ref+W_nox*[Nox]/[Nox]^ref+W_co2*[CO2]/[CO2]^ref+W_HC*[HC]/[HC]^ref+W_CO*[CO]/[CO]^ref+W_noise*[Noise]/[Noise]^ref

and where;

TQI_SP^ref is the targeted indicated torque in Nm;

[Soot]^ref is the targeted soot emission value in g/stroke or g/km;

[Nox]^ref is the targeted nitrogen oxides emission value in g/stroke or g/km;

[CO2]^ref is the targeted carbon dioxide emission value in g/stroke or g/km;

[HC]^ref is the targeted unburnt hydrocarbons emission value in g/stroke or g/km;

[CO]^ref is the targeted carbon monoxide emission value in g/stroke or g/km;

[Noise]^ref is the targeted noise limitation in DbA or bar/s; and

/or

W_k is a weight proportional to the importance of an objective k relative to the others. For example, if the CO2 emission constrains should be rigorously respected, W_CO2 should be more important than the other weights by respecting Σ

_kW_k=1 .

11. The method according to claim 1, wherein an engine actuator used to minimize an error of a multi-objective function J for each operating point in the case of modern EMS dedicated to auto ignition engine control are selected from the group consisting of:

The number of injection Nb_inj par combustion cycle, 1≦

i≦

Nb_inj where i is an index for different fuel injections relating to a large number of fuel injection patterns, such as i=1 for a first pre-injection, i=2 for a second preinjection, etc.;

The quantities injected per elementary injection MFⁱ with Σ

_iMFⁱ=MF;

The start of injection SOI^L per elementary injection;

The air path control by the way of the global equivalence ratio Φ

because in our case the measured air mass flow, MA, is linked to injected mass flow MF by Φ

=(MF/MA)*α

_stoich. The global equivalence ratio Φ

is set according to the engine load targets and the turbocharger air mass flow limitation for a given operating point; and

The EGR rate, X_EGR=[burnt gases]./[fresh gases] defined as the ratio between burnt gases and fresh gases in the intake manifold.

12. The method according to claim 1, wherein embedded maps for the torque realization TOI related to an engine actuators control according to the aforementioned constrains are then reduced to at least one of:

A 2D look up table with a dependence in N and TQI_SP for Nb_inj , the number of injection request per combustion cycle;

A 2D look up table with a dependence in N and TQI_SP for MFⁱ, the injected fuel mass request for each elementary injection i and per combustion cycle;

A 2D look up table with dependence in N and TQI_SP for SOIⁱ, the start of injection request for each elementary injection and per combustion cycle;

A 2D look up table with dependence in N and TQI_SP for Φ

, the global equivalence ratio request per combustion cycle; and

A 2D look up table with dependence in N and TQI_SP for the EGR rate request per combustion cycle.