System and method to estimate intake charge temperature for internal combustion engines

1. Method to estimate an intake charge temperature of an intake charge flow flowing from an intake manifold of an internal combustion engine to cylinders of the engine, the intake charge flow comprising an intake air flow mixing in the intake manifold with an exhaust gas recirculation flow, the method comprising:

monitoring system conditions for the engine including monitoring an exhaust gas recirculation;

determining an effect of the mixing upon a specific heat coefficient of the intake charge flow based upon the system conditions comprising:

determining a ratio of a specific heat coefficient of the intake air flow to the specific heat coefficient of the intake charge flow based upon the exhaust gas recirculation;

estimating the intake charge temperature based upon the effect of the mixing upon the specific heat coefficient of the intake charge flow and the system conditions; and

controlling the engine based upon the intake charge temperature.

2. The method of claim 1 , wherein monitoring the system conditions further comprises monitoring an equivalence ratio; and

wherein determining the ratio of the specific heat coefficient of the intake air flow to the specific heat coefficient of the intake charge flow is further based upon the equivalence ratio.

3. The method of claim 1 , wherein monitoring the system conditions further comprises:

monitoring a ratio of an exhaust gas recirculation temperature to a charge air cooler temperature; and

monitoring an equivalence ratio;

wherein determining the effect of the mixing upon the specific heat coefficient of the intake charge flow further comprises:

determining a ratio of a specific heat coefficient of the exhaust gas recirculation flow to the specific heat coefficient of the intake air flow based upon the ratio of the exhaust gas recirculation temperature to the charge air cooler temperature and the equivalence ratio.

4. The method of claim 3 , wherein monitoring the system conditions further comprises:

monitoring an air fraction;

monitoring the charge air cooler temperature;

monitoring the exhaust gas recirculation temperature;

monitoring a flow rate of the intake charge flow; and

monitoring a derivative of a manifold absolute pressure with respect to time;

wherein estimating the intake charge temperature utilizes the following relationship:

T

c

=

c

pa

c

pc

⁢

(

f

A

·

T

cac

+

(

1

-

f

A

)

·

c

pe

c

pa

⁢

T

egr

-

V

W

c

⁢

γ

⁢

⁢

R

·

ⅆ

P

ⅆ

t

)

;

wherein T c equals the intake charge temperature,

c pa /c pc equals the ratio of the specific heat coefficient of the intake air flow to the specific heat coefficient of the intake charge flow,

f A equals the air fraction,

T cac equals the charge air cooler temperature,

c pe /c pa equals the ratio of the specific heat coefficient of the exhaust gas recirculation flow to the specific heat coefficient of the intake air flow,

T egr equals the exhaust gas recirculation temperature,

V equals a volume of the intake manifold,

W c equals the flow rate of the intake charge flow,

γ equals a specific heat ratio,

R equals a universal gas constant, and

ⅆ

P

ⅆ

t

 equals the derivative of the manifold absolute pressure with respect to time.

5. The method of claim 4 , wherein monitoring the flow rate of the intake charge flow comprises:

determining the flow rate of the intake charge flow based upon a previously estimated intake charge temperature.

6. The method of claim 1 , wherein monitoring the system conditions further comprises:

monitoring a charge air cooler temperature;

monitoring an equivalence ratio; and

monitoring an exhaust gas recirculation temperature;

wherein determining the effect of the mixing upon the specific heat coefficient of the intake charge flow further comprises:

determining a specific heat coefficient of the intake air flow based upon the charge air cooler temperature;

determining a specific heat of a stoichiometric fuel air mix at constant volume based upon the exhaust gas recirculation temperature;

determining a specific heat of air at constant volume based upon the exhaust gas recirculation temperature;

determining a specific heat coefficient of the exhaust gas recirculation flow utilizing the following relationship:

c pe =R+Φ·f cvstoic ( T egr )+(1−Φ) f cvair ( T egr )

wherein c pe equals the specific heat coefficient of the exhaust gas recirculation flow,

R equals a universal gas constant,

Φ equals the equivalence ratio,

T egr equals the exhaust gas recirculation temperature,

f cvstoic (T egr ) equals the specific heat of a stoichiometric fuel air mix at constant volume determined based upon the exhaust gas recirculation temperature, and

f cvair (T egr ) equals the specific heat of air at constant volume determined based upon the exhaust gas recirculation temperature; and

determining a ratio of the specific heat coefficient of the exhaust gas recirculation flow to the specific heat coefficient of the intake air flow.

7. The method of claim 6 , wherein monitoring the system conditions further comprises:

monitoring an air fraction;

monitoring a flow rate of the intake charge flow; and

monitoring a derivative of a manifold absolute pressure with respect to time;

wherein estimating the intake charge temperature utilizes the following relationship:

T

c

=

c

pa

c

pc

⁢

(

f

A

·

T

cac

+

(

1

-

f

A

)

·

c

pe

c

pa

⁢

T

egr

-

V

W

c

⁢

γ

⁢

⁢

R

·

ⅆ

P

ⅆ

t

)

;

wherein T c equals the intake charge temperature,

c pa /c pc equals the ratio of the specific heat coefficient of the intake air flow to the specific heat coefficient of the intake charge flow,

f A equals the air fraction,

T cac equals the charge air cooler temperature,

c pe /c pa equals the ratio of the specific heat coefficient of the exhaust gas recirculation flow to the specific heat coefficient of the intake air flow,

T egr equals the exhaust gas recirculation temperature,

V equals a volume of the intake manifold,

W c equals the flow rate of the intake charge flow,

γ equals a specific heat ratio,

R equals a universal gas constant, and

ⅆ

P

ⅆ

t

 equals the derivative of the manifold absolute pressure with respect to time.

8. The method of claim 1 , wherein monitoring the system conditions further comprises:

monitoring an exhaust gas recirculation valve command;

monitoring a charge air cooler temperature;

monitoring an exhaust gas recirculation temperature;

monitoring a flow rate of the intake air flow;

monitoring a manifold absolute pressure; and

monitoring an engine speed;

wherein determining the effect of the mixing upon the specific heat coefficient of the intake charge flow further comprises:

determining a specific heat coefficient of the intake air flow based upon the system conditions;

determining a specific heat coefficient of the exhaust gas recirculation flow based upon the system conditions; and

determining the specific heat coefficient of the intake charge flow based upon the specific heat coefficient of the intake air flow and the ratio of the specific heat coefficient of the intake air flow to the specific heat coefficient of the intake charge flow; and

wherein, when the exhaust gas recirculation valve command does not indicate closure of the exhaust gas recirculation valve, estimating the intake charge temperature utilizes the following relationship:

T

c

=

PD

⁡

(

N

2

)

⁢

η

v

[

PD

⁡

(

N

2

)

⁢

η

v

⁢

c

pc

R

-

W

a

⁢

c

pa

⁢

T

cac

c

pe

⁢

T

egr

+

W

a

]

⁢

R

·

120

;

wherein T c equals the intake charge temperature,

P equals the manifold absolute pressure,

D equals a cylinder displacement volume,

N equals an engine speed,

η v equals a volumetric efficiency of the engine,

c pc equals the specific heat coefficient of the intake charge flow,

W a equals a flow rate of the intake air flow,

c pa equals the specific heat coefficient of the intake air flow,

T cac equals the charge air cooler temperature,

c pe equals the specific heat coefficient of the exhaust gas recirculation flow,

T egr equals the exhaust gas recirculation temperature, and

R equals a universal gas constant.

9. The method of claim 8 wherein, when the exhaust gas recirculation valve command indicates closure of the exhaust gas recirculation valve, estimating the intake charge temperature utilizes the following relationship:

T c =T cac +ΔT;

wherein ΔT is a temperature change within the intake manifold.

10. The method of claim 8 , wherein monitoring the system conditions further comprises:

monitoring an air fraction;

monitoring an exhaust gas recirculation temperature;

monitoring a flow rate of the intake charge flow;

monitoring a manifold absolute pressure; and

monitoring a derivative of the manifold absolute pressure with respect to time

wherein determining the effect of the mixing upon a specific heat coefficient of the intake charge flow further comprises:

determining a ratio of the specific heat coefficient of the exhaust gas recirculation flow to the specific heat coefficient of the intake air flow;

wherein, when the exhaust gas recirculation valve command indicates closure of the exhaust gas recirculation valve, estimating the intake charge temperature utilizes the following relationship:

T

c

=

c

pa

c

pc

⁢

(

f

A

·

T

cac

+

(

1

-

f

A

)

·

c

pe

c

pa

⁢

T

egr

-

V

W

c

⁢

γ

⁢

⁢

R

·

ⅆ

P

ⅆ

t

)

;

wherein T c equals the intake charge temperature,

c pa /c pc equals the ratio of the specific heat coefficient of the intake air flow to the specific heat coefficient of the intake charge flow,

f A equals the air fraction,

T cac equals the charge air cooler temperature,

c pe /c pa equals the ratio of the specific heat coefficient of the exhaust gas recirculation flow to the specific heat coefficient of the intake air flow,

T egr equals the exhaust gas recirculation temperature,

V equals a volume of the intake manifold,

W c equals the flow rate of the intake charge flow,

γ equals a specific heat ratio,

R equals a universal gas constant, and

ⅆ

P

ⅆ

t

 equals the derivative of the manifold absolute pressure with respect to time.

11. Method to estimate an intake charge temperature of an intake charge flow flowing from an intake manifold of an internal combustion engine to cylinders of the engine, the intake charge flow comprising an intake air flow mixing in the intake manifold with an exhaust gas recirculation flow, the method comprising:

monitoring system conditions for the engine;

determining a ratio of a specific heat coefficient of the intake air flow to a specific heat coefficient of the intake charge flow based upon the system conditions;

determining a ratio of a specific heat coefficient of the exhaust gas recirculation flow to the specific heat coefficient of the intake air flow based upon the system conditions;

estimating the intake charge temperature based upon the ratio of the specific heat coefficient of the intake air flow to the specific heat coefficient of the intake charge flow, the ratio of the specific heat coefficient of the exhaust gas recirculation flow to the specific heat coefficient of the intake air flow, and the system conditions; and

controlling the engine based upon the estimated intake charge temperature.

12. System to estimate an intake charge temperature in an intake manifold of an internal combustion engine comprising a charging system providing an intake air flow and an exhaust gas recirculation circuit providing an exhaust gas recirculation flow, the system comprising:

the intake manifold mixing the intake air flow and exhaust gas recirculation flow to provide an intake charge flow to cylinders of the engine; and

a control module:

monitoring system conditions for the engine including monitoring an exhaust gas recirculation;

determining an effect of the mixing upon a specific heat coefficient of the intake charge flow based upon the system conditions comprising:

determining a ratio of a specific heat coefficient of the intake air flow to the specific heat coefficient of the intake charge flow based upon the exhaust gas recirculation;

estimating the intake charge temperature based upon the effect of the mixing upon the specific heat coefficient of the intake charge flow and the system conditions; and

controlling the engine based upon the estimated intake charge temperature.

13. The system of claim 12 , wherein the control module further monitors an exhaust gas recirculation valve command; and

wherein estimating the intake charge temperature is based upon the exhaust gas recirculation valve command.

14. The system of claim 12 :

wherein monitoring system conditions for the engine further comprises:

monitoring a ratio of an exhaust gas recirculation temperature to a charge air cooler temperature; and

monitoring an equivalence ratio;

wherein determining a ratio of a specific heat coefficient of the intake air flow to the specific heat coefficient of the intake charge flow comprises:

referencing a look-up table providing a calibrated ratio of a specific heat coefficient of the intake air flow to the specific heat coefficient of the intake charge flow;

wherein determining the effect of the mixing upon the specific heat coefficient of the intake charge flow further comprises:

referencing a look-up table providing a calibrated ratio of a specific heat coefficient of the exhaust gas recirculation flow to the specific heat coefficient of the intake air flow; and

wherein estimating the intake charge temperature comprises estimating the intake charge temperature based upon the calibrated ratio of the specific heat coefficient of the intake air flow to the specific heat coefficient of the intake charge flow and the calibrated ratio of the specific heat coefficient of the exhaust gas recirculation flow to the specific heat coefficient of the intake air flow.