Estimation of exhaust gas temperature at the output of the EGR circuit of a combustion engine
AssigneeRENAULT s.a.s.
InventorsPhilippe Recouvreur, Olivier Tigrine
Life of this patent
Estimating the term…
Abstract
A method for estimating the temperature of exhaust gases of a combustion engine at an output of an EGR circuit fitted on the engine, based on a model that takes into account thermal energy losses of the exhaust gases at an EGR cooler or EGR circuit, the model also taking into account thermal exchange between the exhaust gases and the walls of a duct conveying the exhaust gases to the EGR cooler. A vehicle can implement such an estimation.
Claims6
A method of estimating an exhaust gas temperature T3 in an internal combustion engine of a vehicle at an outlet of an EGR circuit with which the engine is equipped, the vehicle including an electronic temperature estimating computer, the method comprising:
- measuring an EGR circuit inlet temperature T0;
- calculating, using the electronic temperature estimating computer, a temperature TW of a wall of an EGR duct conveying exhaust gas in the EGR circuit;
- calculating, using the electronic temperature estimating computer, a temperature T2 of the exhaust gas at an inlet of an EGR cooler of the EGR circuit;
- estimating, using the electronic temperature estimating computer, the exhaust gas temperature T3 at the outlet of the EGR circuit based on the EGR circuit inlet temperature T0, the temperature T2 of the exhaust gas at the inlet of the EGR cooler, and a thermal energy loss of the exhaust gas in the EGR cooler of the EGR circuit,
- wherein the temperature TW of the wall is calculated according to the following:
- {
- T
- w
-
-
- ∞
- =
- T
- 0
-
- (
- 1
- -
- ɛ
- 1
- )
- +
- ɛ
- 1
-
- T
- water
- ⅆ
- T
- w
- ⅆ
- t
- =
- 1
- τ
- w
-
- [
- T
- w
-
-
- ∞
- -
- T
- w
- ]
- where:
- ɛ
- 1
- =
- K
- 1
- K
- 1
- +
- Cp
- egr
-
- Q
- egr
-
- ɛ
- 2
- ;
- K1=constant;
- τw=Time constant of the EGR duct upstream of the EGR cooler;
- Tw∞=Instantaneous wall temperature (with zero wall thermal inertia);
- ε1=external efficiency of the EGR duct upstream of the EGR cooler upon simplifying predetermined differential equations;
- and
- ε2=Internal efficiency of the EGR duct upstream of the EGR cooler upon simplifying the predetermined differential equations.
A method of estimating an exhaust gas temperature T3 in an internal combustion engine of a vehicle at an outlet of an EGR circuit with which the engine is equipped, the vehicle including an electronic temperature estimating computer, the method comprising:
- estimating, using the electronic temperature estimating computer, a thermal energy loss of exhaust gas in an EGR cooler of the EGR circuit;
- estimating, using the electronic temperature estimating computer, an internal heat exchange between the exhaust gas and a wall of an EGR duct conveying the exhaust gas to the EGR cooler;
- and
- estimating, using the electronic temperature estimating computer, an external heat exchange between the wall of the EGR duct and an environment of an engine compartment;
- wherein the estimating the thermal energy loss, the estimating the internal heat exchange, and the estimating the external heat exchange are done according to the following:
- {
- M
- st
- .
- st
-
- Cp
- st
- .
- st
-
- ⅆ
- T
- w
- ⅆ
- t
- =
- h
- int
-
- S
-
- (
- T
- 2
- -
- T
- w
- )
- +
-
- ɛσ
-
-
- Sf
- ij
-
- (
- T
- radiative
- 4
- -
- T
- w
- 4
- )
- +
- h
- ext
-
- S
-
- (
- T
- convective
- -
- T
- w
- )
- M
- egr
-
- Cp
- egr
-
- ⅆ
- T
- 2
- ⅆ
- t
- =
- h
- int
-
- S
-
- (
- T
- w
- -
- T
- 2
- )
- +
- Q
- egr
-
- Cp
- egr
-
- (
- T
- 0
- -
- T
- 2
- )
- ⅆ
- T
- 3
- ⅆ
- t
- =
- 1
- τ
- 3
-
- [
- T
- 2
-
- (
- 1
- -
- ɛ
- 3
- )
- +
- ɛ
- 3
-
- T
- water
- -
- T
- 3
- ]
- where:
- Cpegr=Specific heat of the exhaust gas at constant pressure
- Cpst.st=Specific heat of the EGR duct upstream of the EGR cooler
- ⅆ
- ⅆ
- t
- =
- Derivative
-
-
- with
-
-
- respect
-
-
- to
-
-
- time
- fij=Form factor for radiative heat exchange
- hext=Convective heat exchange coefficient for exchange between the wall of the EGR duct and airflow under a hood of the vehicle
- hint=Convective heat exchange coefficient for exchange between the exhaust gas upstream of the EGR cooler and the wall
- Mst.st=Mass of said EGR duct
- Megr=Mass of the exhaust gas upstream of the EGR cooler
- Qegr=EGR mass flow rate
- S=Heat exchange area of the EGR duct upstream of the EGR cooler
- T0=Exhaust gas temperature before a turbine or at an inlet of the EGR circuit
- Tconvective=Average temperature of air under the hood of the vehicle
- Twater=Water temperature at an outlet of the engine
- Tradiative=Average temperature of all components under the hood of the vehicle
- ε=Emissivity of said EGR duct at an inlet of the EGR cooler
- ε3=Efficiency of the EGR cooler
- τ3=Time constant of the EGR cooler
- and in which:
- Tconvective≈Tradiative≈Twater
- hint is calculated using an empirical relationship linking three dimensionless coefficients, namely a Nusselt number, a Reynolds number and a Prandtl number:
- Nu=f(Re0.8,Pr);
- hext is considered to be constant and adjusted so as to reset the method of estimating in respect to trials;
- fij=1;
- ε is around 0.8 or another known constant;
- and
- ɛ
- 3
- =
- T
- 2
- -
- T
- 3
- T
- 2
- -
- T
- water
- .
A non-transitory computer-readable storage medium, having stored thereon a program that when executed by an electronic temperature estimating computer, causes the electronic temperature estimating computer to perform a method comprising:
- measuring an EGR circuit inlet temperature T0;
- calculating, using the electronic temperature estimating computer, a temperature TW of a wall of an EGR duct conveying exhaust gas to an EGR circuit;
- calculating, using the electronic temperature estimating computer, a temperature T2 of the exhaust gas at an inlet of an EGR cooler of the EGR circuit;
- estimating, using the electronic temperature estimating computer, an exhaust gas temperature T3 at an outlet of an EGR circuit based on the EGR circuit inlet temperature T0, the temperature T2 of the exhaust gas at the inlet of the EGR cooler, and a thermal energy loss of the exhaust gas in the EGR cooler of the EGR circuit,
- wherein the temperature TW of the wall is calculated according to the following:
- {
- T
- w
-
-
- ∞
- =
- T
- 0
-
- (
- 1
- -
- ɛ
- 1
- )
- +
- ɛ
- 1
-
- T
- water
- ⅆ
- T
- w
- ⅆ
- t
- =
- 1
- τ
- w
-
- [
- T
- w
-
-
- ∞
- -
- T
- w
- ]
- where:
- ɛ
- 1
- =
- K
- 1
- K
- 1
- +
- Cp
- egr
-
- Q
- egr
-
- ɛ
- 2
- ;
- K1=constant;
- τw=Time constant of the EGR duct upstream of the EGR cooler;
- Tw∞=Instantaneous wall temperature (with zero wall thermal inertia);
- ε2=external efficiency of the EGR duct upstream of the EGR cooler upon simplifying predetermined differential equations;
- and
- ε2=Internal efficiency of the EGR duct upstream of the EGR cooler upon simplifying the predetermined differential equations.
Dependencies are inferred from the claim text.