DEF dosing using multiple dosing locations while maintaining high passive soot oxidation
View Patent ↗Diesel Exhaust Fluid is metered into an engine exhaust gas aftertreatment system having a close coupled SCR catalyst and a main SCR catalyst. The DEF is injected into two injector locations, one upstream of the close coupled SCR catalyst and another upstream of the main SCR catalyst, the quantity of DEF in each injector being based on primarily the temperature at the main SCR catalyst and the mass flow of the NOx through the aftertreatment system. This method of injection enables a relatively better fuel economy outcome while meeting the regulated tailpipe NO x emission levels and the N 2 O formation limits.
1. An internal combustion engine generating exhaust, the internal combustion engine comprising:
an exhaust aftertreatment system comprising a diesel oxidation catalyst, a diesel particulate filter, a close coupled SCR catalyst for converting NOx in the exhaust into nitrogen and water by selective catalytic reduction upstream of the diesel oxidation catalyst and the diesel particulate filter and a main SCR catalyst for converting NOx in exhaust into nitrogen and water by selective catalytic reduction downstream of the diesel oxidation catalyst and the diesel particulate filter;
a Diesel Exhaust Fluid (DEF) dosing system comprising a first injector and a first mixer to inject and distribute a first quantity of DEF of a desired total DEF quantity into the close coupled SCR catalyst and a second injector and a second mixer to inject and distribute a second quantity of DEF of the desired total DEF quantity into the main SCR catalyst;
a controller for controlling the first quantity of DEF and the second quantity of DEF; wherein
the controller calculates the first quantity of DEF to be injected by using a plurality of predetermined maps based on temperature of the main SCR catalyst and a mass flow of the NOx flowing into the exhaust aftertreatment system and wherein;
the controller additionally calculates the second quantity of DEF to be injected based on the difference between the desired total DEF quantity and the first quantity of DEF.
2. The internal combustion engine of claim 1 wherein the first quantity of DEF to be injected through the first injector is additionally calculated based on temperature of the diesel particulate filter.
3. The internal combustion engine of claim 1 where in the first injector is upstream of the close coupled SCR catalyst and the second injector is upstream of the main SCR catalyst and downstream of the diesel particulate filter.
4. The internal combustion engine of claim 1 wherein the close coupled SCR is a vanadium-based formulation.
5. The internal combustion engine of claim 1 wherein the main SCR is a Cu Zeolite formulation.
6. The internal combustion engine of claim 1 wherein temperature of the main SCR is measured using a temperature probe in the main SCR and the mass flow of the NOx is measured using a flow sensor placed in the exhaust manifold.
7. A control system of an internal combustion engine, the control system comprising:
a controller;
a first data source providing data defining a first value of a main SCR temperature;
a second data source providing a mass flow of NOx;
a first pre-determined map determining a desired total DEF dosing quantity based on the main SCR temperature and the mass flow of NOx;
a second pre-determined map determining a desired first fraction of the desired total DEF dosing quantity through a first injector; wherein
the controller calculates a first DEF dosing quantity through the first injector based on the first fraction of the desired total DEF dosing quantity and the desired total DEF dosing quantity; and commands the first injector to inject the calculated first DEF dosing quantity; and wherein
the controller additionally commands a second injector to inject a second fraction of the desired total DEF dosing quantity; the second fraction of the desired total DEF dosing quantity determined by calculating the difference between the desired total DEF dosing quantity and the desired first fraction of the desired total DEF dosing quantity.
8. The control system of claim 7 ; wherein the first data source is a temperature sensor.
9. The control system of claim 7 , wherein the second data source is at least one of a flow sensor and a model.
10. The control system of claim 7 ; wherein the first injector is upstream of a close coupled SCR catalyst.
11. The second, injector of claim 7 ; wherein the second injector is upstream of the main SCR catalyst.