Experimental demonstration of a new model-based SCR control strategy for cleaner heavy-duty diesel engines

Selective catalytic reduction (SCR) is a promising diesel aftertreatment technology that enables low nitrogen oxides $({rm NO}_{rm x})$ tailpipe emissions with relatively low fuel consumption. Future emission legislation is pushing the boundaries for SCR control systems to achieve high ${rm NO}_{rm x}$ conversion within a tailpipe ammonia $({rm NH}_{3})$ slip constraint, and to provide robustness to meet in-use compliance requirements. This work presents a new adaptive control strategy that uses an ammonia feedback sensor and an online ammonia storage model. Experimental validation on a 12-liter heavy-duty diesel engine with a 34-liter Zeolite SCR catalyst shows good performance and robustness against urea under- and over-dosage for both the European steady-state and transient test cycles. The new strategy is compared with a ${rm NO}_{rm x}$ sensor-based control strategy with cross-sensitivity compensation. It proved to be superior in terms of transient adaptation and taking an ${rm NH}_{3}$ slip constraint into account