Modeling of Aftertreatment Technologies to Meet a Future HD Low-NOx Standard 2019-01-0043
The low-NOx standard for heavy duty trucks proposed by the California Air Resources Board represents a significant challenge to the engine and aftertreatment system. In this study, exhaust thermal management requirements have been quantified using a combination of engine and aftertreatment modeling. First, a 1-D engine model was used to develop a control strategy capable of increasing the exhaust enthalpy and decreasing the engine-out NOx over the initial portion of the cold FTP cycle. The outputs from this model were then used as inputs to a 1-D model of a representative HD aftertreatment system. Several different passive exhaust thermal management technologies were evaluated with this aftertreatment system model, including insulating the downpipe, close-coupling the aftertreatment system, and reducing the thermal inertia of the DOC and DPF; the last option provides the most benefit to early NOx conversion. As an example of active exhaust thermal management, a model of a mini-burner was inserted into the system model; this device is able to raise the system temperature quickly, using less fuel than the engine control strategy. Lastly, early NH3 dosing and NH3 preloading on the SCR catalyst were examined; pre-loading would appear to be much more effective.
Thomas Miller Harris, Timothy Gardner
International Powertrains, Fuels & Lubricants Meeting