A predictive control approach to diesel Selective Catalytic Reduction

Abstract

Reduction of oxides of nitrogen (NOx) emitted from diesel exhaust systems is a current problem due to increased stringency in worldwide emissions legislation. One of the most successful approaches to reduce tailpipe NOx is to reduce NOx by ammonia over a catalyst, known as Selective Catalytic Reduction (SCR). Control of the ammonia injection in such systems is typically a map-based approach, often augmented by feedback from NOx sensors to account for mechanical variation and ageing. We show that a predictive control approach to this system yields several compelling improvements over such industry standard controllers during a representative test cycle. These include better NOx conversion performance whilst simultaneously minimising the quantity of ammonia released to the environment, along with reduced design effort.

In‐use emissions testing of diesel‐driven buses in Southampton: is selective catalytic reduction as effective as fleet operators think?

“…Another way to improve the catalyst efficiency is through advanced control of the ammonia injection. The use of reference governor approach [15] and some of the authors' recent works on medel predictive control (MPC) [16,17] have shown promise for achieving improved NOx reduction in this temperature limited operating region, since it allows operation closer to constraint boundaries than classical control. However, it is clear from this work that this is not sufficient to meet emissions targets: additional thermal management of the catalyst is required.…”