System and method of controlling maximum hydrocarbon injection for diesel particulate filter regeneration
View Patent ↗A method of providing hydrocarbons to an engine exhaust for regenerating a diesel particulate filter within an exhaust system of a diesel engine. A mass flow rate of exhaust gas within an exhaust system is determined. A mass flow rate of oxygen within the exhaust gas entering the diesel oxidation catalyst is determined. A set point indicative of an allowable mass flow rate of oxygen within the exhaust gas exiting the diesel oxidation catalyst is received. A hydrocarbon threshold that may be injected into the exhaust system is calculated. Hydrocarbons are injected into the exhaust system upstream of the diesel oxidation catalyst, wherein the injected hydrocarbons do not exceed the calculated threshold amount of hydrocarbons.
1. A method of providing hydrocarbons to an engine exhaust for regenerating a diesel particulate filter within an exhaust system of a diesel engine, the diesel engine comprising an electronic control module, at least one cylinder, and a diesel oxidation catalyst within the exhaust system, the method comprising:
determining a mass flow rate of exhaust gas within an exhaust system;
determining a mass flow rate of oxygen within the exhaust gas entering the diesel oxidation catalyst;
determining a minimum mass flow rate of oxygen within the exhaust gas exiting the diesel oxidation catalyst;
receiving a set point indicative of an allowable mass flow rate of oxygen within the exhaust gas exiting the diesel oxidation catalyst;
calculating a hydrocarbon threshold for injecting into the exhaust system based upon the mass flow rate of exhaust gas within the exhaust system, the mass flow rate of oxygen within the exhaust gas entering the diesel oxidation catalyst, and the minimum mass flow rate of oxygen within the exhaust gas exiting the diesel oxidation catalyst;
calculating an amount of hydrocarbons required to raise a temperature of the diesel particulate filter to a pre-set temperature for regeneration;
comparing the amount of hydrocarbons required to raise the temperature of the diesel particulate filter to the hydrocarbon threshold determined to be injected into the exhaust system based upon the mass flow rate of exhaust gas within the exhaust system, the mass flow rate of oxygen within the exhaust gas entering the diesel oxidation catalyst, and the minimum mass flow rate of oxygen within the exhaust gas exiting the diesel oxidation catalyst;
injecting an amount of hydrocarbons equal to the lesser of the amount of hydrocarbons required to raise a temperature of the diesel particulate filter to a pre-set temperature for regeneration and a maximum amount of hydrocarbons determined to be injected into the exhaust system based upon the mass flow rate of exhaust gas within the exhaust system, the mass flow rate of oxygen within the exhaust gas entering the diesel oxidation catalyst, and the minimum mass flow rate of oxygen within the exhaust gas exiting the diesel oxidation catalyst.
2. The method of claim 1 , wherein the hydrocarbon threshold determined to be injected into the exhaust system based upon the mass flow rate of exhaust gas within the exhaust system, the mass flow rate of oxygen within the exhaust gas entering the diesel oxidation catalyst, and the minimum mass flow rate of oxygen within the exhaust gas exiting the diesel oxidation catalyst varies based upon the hydrocarbon utilized.
3. The method of claim 1 , wherein the hydrocarbon threshold determined to be injected into the exhaust system based upon the mass flow rate of exhaust gas within the exhaust system, the mass flow rate of oxygen within the exhaust gas entering the diesel oxidation catalyst, and the minimum mass flow rate of oxygen within the exhaust gas exiting the diesel oxidation catalyst is calculated during transient engine operating conditions.
4. The method of claim 1 , wherein the hydrocarbon threshold determined to be injected into the exhaust system based upon the mass flow rate of exhaust gas within the exhaust system, the mass flow rate of oxygen within the exhaust gas entering the diesel oxidation catalyst, and the minimum mass flow rate of oxygen within the exhaust gas exiting the diesel oxidation catalyst is calculated according to the formula:
m
.
DOCfuel
,
max
=
(
12.01
a
+
1.008
b
)
(
a
+
b
4
)
(
m
.
O
2
,
in
-
mf
O
2
,
out
,
min
m
.
exh
32.00
)
wherein a corresponds to the number of carbon atoms in the hydrocarbon and b corresponds to the number of hydrogen atoms in the hydrocarbon.
5. A method for preventing over-injection of hydrocarbons, the method comprising, a non-transitory computer usable medium having an executable computer readable program code embodied therein, the executable computer readable program code for implementing a method for determining a maximum amount of hydrocarbons to be provided to an engine exhaust system for regenerating a diesel particulate filter while limiting hydrocarbon slip through a diesel oxidation catalyst, the method comprising:
determining a mass flow rate of exhaust gas within an exhaust system;
determining a mass flow rate of oxygen within the exhaust gas entering the diesel oxidation catalyst;
retrieving a minimum allowable mass flow rate of oxygen within the exhaust gas exiting the diesel oxidation catalyst;
varying the minimum allowable mass flow rate of oxygen within the exhaust gas exiting the diesel oxidation catalyst based on the hydrocarbon;
calculating a maximum amount of hydrocarbons to be injected into the exhaust system based upon the mass flow rate of exhaust gas within the exhaust system, the mass flow rate of oxygen within the exhaust gas entering the diesel oxidation catalyst, and the minimum mass flow rate of oxygen within the exhaust gas exiting the diesel oxidation catalyst to combust the hydrocarbons injected into the exhaust system, and injecting an amount of hydrocarbons less than the maximum amount of hydrocarbons calculated to be injected into the exhaust system.
6. The method of claim 5 , wherein the hydrocarbon is diesel fuel.
7. The method of claim 5 , wherein the maximum amount of hydrocarbons to be injected into the exhaust system based upon the mass flow rate of exhaust gas within the exhaust system, the mass flow rate of oxygen within the exhaust gas entering the diesel oxidation catalyst, and the minimum mass flow rate of oxygen within the exhaust gas exiting the diesel oxidation catalyst is calculated during transient engine operating conditions.
8. The method of claim 5 , wherein the maximum amount of hydrocarbons to be injected into the exhaust system based upon the mass flow rate of exhaust gas within the exhaust system, the mass flow rate of oxygen within the exhaust gas entering the diesel oxidation catalyst, and the minimum mass flow rate of oxygen within the exhaust gas exiting the diesel oxidation catalyst is calculated according to the formula:
m
.
DOCfuel
,
max
=
(
12.01
a
+
1.008
b
)
(
a
+
b
4
)
(
m
.
O
2
,
in
-
mf
O
2
,
out
,
min
m
.
exh
32.00
)
wherein a corresponds to the number of carbon atoms in the hydrocarbon and b corresponds to the number of hydrogen atoms in the hydrocarbon.
9. The method of claim 8 , wherein mf O2 , out, min is stored in the electronic control module.