Method and apparatus for controlling operation of an internal combustion engine operating in HCCI combustion mode
View Patent ↗An internal combustion engine is configured to operate in a homogeneous-charge compression-ignition combustion mode. A method for operating the internal combustion engine includes determining a desired effective charge dilution for a cylinder charge for a cylinder firing event. A desired air/fuel ratio, a desired intake air mass and a desired intake oxygen are determined to achieve the desired effective charge dilution for a combustion event. The desired air/fuel ratio is adjusted based upon a difference between the desired intake oxygen and the actual intake oxygen, and engine operation is controlled to achieve the adjusted desired air/fuel ratio.
1. Method for operating an internal combustion engine configured to operate in a homogeneous-charge compression-ignition (HCCI) combustion mode, comprising:
determining a desired effective charge dilution for a cylinder firing event in accordance with the following relationship:
ED
=
α
Ambient
Intake
O
2
(
%
)
-
Intake
O
2
(
%
)
Ambient
Intake
O
2
(
%
)
+
β
AFR
-
Stoichiometric
AFR
Stoichiometric
AFR
wherein Ambient Intake O 2 is an amount (in %) of oxygen in ambient air,
Intake O 2 is an actual amount (in %) of oxygen in engine intake air,
AFR is an actual air/fuel ratio,
Stoichiometric AFR is the stoichiometric air/fuel ratio for the fuel, and
α and β are positive, calibratable/tunable parameters;
determining a desired air/fuel ratio, a desired intake air mass, and a desired intake oxygen to achieve the desired effective charge dilution;
adjusting the desired air/fuel ratio based upon a difference between the desired intake oxygen and an actual intake oxygen; and
controlling engine operation to achieve the adjusted desired air/fuel ratio.
2. The method of claim 1 , wherein controlling engine operation to achieve the adjusted desired air/fuel ratio comprises controlling a fast engine actuator to achieve the adjusted desired air/fuel ratio.
3. The method of claim 2 , wherein controlling the fast engine actuator to achieve the adjusted desired air/fuel ratio comprises controlling a setpoint for a variable cam phaser to achieve the adjusted desired air/fuel ratio.
4. The method of claim 1 , wherein adjusting the desired air/fuel ratio based upon the difference between the desired intake oxygen and the actual intake oxygen comprises adjusting the desired air/fuel ratio to an air/fuel ratio setpoint that is leaner than the desired air/fuel ratio in response to a change in an operator torque request comprising an accelerator pedal tip-in event.
5. The method of claim 1 , wherein adjusting the desired air/fuel ratio based upon the difference between the desired intake oxygen and the actual intake oxygen comprises adjusting the desired air/fuel ratio to an air/fuel ratio setpoint that is richer than the desired air/fuel ratio in response to a change in an operator torque request comprising an accelerator pedal tip-out event.
6. The method of claim 1 , wherein adjusting the desired air/fuel ratio based upon the difference between the desired intake oxygen and the actual intake oxygen comprises adjusting the desired air/fuel ratio in response to a change in engine load.
7. Method for operating an internal combustion engine configured to operate in a homogeneous-charge compression-ignition (HCCI) combustion mode, comprising:
determining a desired effective charge dilution for a cylinder firing event in response to a change in an operator torque request during operation in the HCCI combustion mode in accordance with the following relationship:
ED
=
α
Ambient
Intake
O
2
(
%
)
-
Intake
O
2
(
%
)
Ambient
Intake
O
2
(
%
)
+
β
AFR
-
Stoichiometric
AFR
Stoichiometric
AFR
wherein Ambient Intake O 2 is an amount (in %) of oxygen in ambient air,
Intake O 2 is an actual amount (in %) of oxygen in engine intake air,
AFR is an actual air/fuel ratio,
Stoichiometric AFR is the stoichiometric air/fuel ratio for the fuel, and
α and β are positive, calibratable/tunable parameters;
determining a desired air/fuel ratio, a desired intake air mass, and a desired intake oxygen to achieve the desired effective charge dilution;
monitoring actual intake oxygen;
adjusting the desired air/fuel ratio based upon a difference between the actual intake oxygen and the desired intake oxygen; and
controlling engine operation to achieve the adjusted desired air/fuel ratio for subsequent firing events.
8. The method of claim 7 , wherein controlling engine operation to achieve the adjusted desired air/fuel ratio comprises controlling a fast engine actuator to achieve the adjusted desired air/fuel ratio.
9. The method of claim 8 , wherein controlling the fast engine actuator to achieve the adjusted desired air/fuel ratio comprises controlling a setpoint for a variable cam phaser to achieve the adjusted desired air/fuel ratio.
10. The method of claim 7 , wherein adjusting the desired air/fuel ratio based upon the difference between the actual intake oxygen and the desired intake oxygen comprises adjusting the desired air/fuel ratio to an air/fuel ratio setpoint that is leaner than the desired air/fuel ratio in response to a change in the operator torque request comprising an accelerator pedal tip-in event.
11. The method of claim 7 , wherein adjusting the desired air/fuel ratio based upon the difference between the actual intake oxygen and the desired intake oxygen comprises adjusting the desired air/fuel ratio to an air/fuel ratio setpoint that is richer than the desired air/fuel ratio in response to a change in the operator torque request comprising an accelerator pedal tip-out event.
12. The method of claim 7 , wherein adjusting the desired air/fuel ratio based upon the difference between the actual intake oxygen and the desired intake oxygen comprises adjusting the desired air/fuel ratio in response to a change in engine load associated with the change in the operator torque request.
13. An internal combustion engine, comprising:
an intake manifold;
an exhaust manifold;
a combustion chamber;
a phase controllable intake valve for controlling airflow from the intake manifold to the combustion chamber;
a phase controllable exhaust valve for controlling exhaust flow from the combustion chamber to the exhaust manifold;
an exhaust gas recirculation system for controlling exhaust flow from the exhaust manifold to the intake manifold; and
a control system comprising a control module to provide a setpoint for an effective charge dilution comprising a predetermined relationship between an air-fuel ratio and an intake oxygen fraction, determine an air-fuel ratio adjustment based upon the difference between an actual intake oxygen fraction and a desired intake oxygen fraction, and control the intake and exhaust valve phase relationship to effect the air-fuel ratio adjustment by trapped air in order to maintain said setpoint for the effective charge dilution.
14. The internal combustion engine of claim 13 , wherein said predetermined relationship between the air-fuel ratio and the intake oxygen fraction comprises the following relationship:
ED
=
α
Ambient
Intake
O
2
(
%
)
-
Intake
O
2
(
%
)
Ambient
Intake
O
2
(
%
)
+
β
AFR
-
Stoichiometric
AFR
Stoichiometric
AFR
wherein Ambient Intake O 2 is an amount (in %) of oxygen in ambient air,
Intake O 2 is an actual amount (in %) of oxygen in engine intake air,
AFR is an actual air/fuel ratio,
Stoichiometric AFR is the stoichiometric air/fuel ratio for the fuel, and
α and β are positive, calibratable/tunable parameters.