METHOD FOR ESTIMATING THE HEAT EXCHANGE RATE RELATED TO EXOTHERMIC OXIDATION REACTIONS OF A DIESEL OXIDATION CATALYTIC CONVERTER IN AN INTERNAL COMBUSTION ENGINE
A method is provided for estimating the heat exchange rate related to the exothermic oxidation reactions of a catalytic converter in an internal combustion engine. Exhaust gases flow through the catalytic converter, the method includes, but is not limited to providing a thermal model of a catalytic converter where no oxidation reactions take place. The thermal model includes, but is not limited to equations that take into account the heat exchange rate related to the processes between the exhaust gases, the catalytic converter and an external environment surrounding the catalytic converter, calculating an estimated outlet temperature at the outlet of the catalytic converter, based on the thermal model, measuring an outlet temperature at the outlet of the catalytic converter comparing the estimated outlet temperature with the measured outlet temperature, thus obtaining a correction factor, correcting the thermal model by using the correction factor in order to make the estimated outlet temperature converge to the measured outlet temperature, estimating the heat exchange rate related to the exothermic oxidation reactions as the correction factor.
1 . A method for estimating a heat exchange rate related to the exothermic oxidation reactions of a catalytic converter in an internal combustion engine, wherein exhaust gases flow through said catalytic converter, the method comprising the steps of:
providing a thermal model of a catalytic converter, wherein no oxidation reactions take place, said thermal model comprising a plurality of equations that take into account the heat exchange rate related to the processes between the exhaust gases, the catalytic converter and an external environment surrounding said catalytic converter;
calculating an estimated outlet temperature (T out,est ; T out,est1 ) at the outlet of said catalytic converter, based on said thermal model;
measuring an outlet temperature (T out,meas ) at the outlet of said catalytic converter;
comparing said estimated outlet temperature with the measured outlet temperature (T out,meas ), thus obtaining a correction factor;
correcting the thermal model by using said correction factor in order to make the estimated outlet temperature (T out,est ; T out,est1 ) converge to the measured outlet temperature (T out,meas ); and
estimating the heat exchange rate related to the exothermic oxidation reactions as said correction factor.
2 . The method according to claim 1 , wherein the thermal model is based on the following equations:
Q
in
t
+
Q
out
t
+
Q
exch
1
t
=
0
C
T
cat
t
=
Q
exch
t
where Q in is an input entropy flow rate at the inlet of the catalytic converter, Q out is an output entropy flow rate at the output of the catalytic converter, Q exch1 is a thermal exchange between the exhaust gases and the catalytic converter, Q exch is a heat exchange rate due to the processes between the exhaust gases, the catalytic converter and the external environment, C is a heat capacity of the catalytic converter and T cat is a temperature value indicative of the thermal state of the catalytic converter.
3 . The method according to claim 2 , wherein the input entropy flow rate (Q in ) and the output entropy flow rate (Q out ) are defined according to the following equations:
Q
in
t
=
m
.
in
C
p
T
in
Q
out
t
=
-
m
.
out
C
p
T
out
where {dot over (m)} out is an exhaust mass flow rate at the output of the catalytic converter, T out is an outlet gas temperature and C p is an exhaust gas specific heat.
4 . The method according to claim 3 , wherein said estimated temperature is a function of an inlet exhaust mass flow rate ({dot over (m)} in ) an inlet gas temperature (T in ), the exhaust gas specific heat (C p ), the thermal exchange between the exhaust gases and the catalytic converter (Q exch1 ) and the temperature value indicative of the thermal state of the catalytic converter (T cat ).
5 . The method according to claim 1 , wherein said correction factor is based on the following equation:
Q
oxi
t
=
K
(
T
out
,
meas
-
T
out
,
est
)
where Q oxi is the heat exchange rate related to the exothermic oxidation.