Hierarchical model predictive control for an off-highway diesel engine with SCR catalyst

Abstract

Diesel engines become more and more complex systems, especially due to increasingly restrictive emission laws. The selective catalytic reduction (SCR) is a promising way to lower nitrogen oxide emissions. The slow dynamics of the catalyst, however, have to be compensated by the engine, for example to comply with emission laws during transients. This work presents a bi-level nonlinear model predictive control (MPC) concept for a diesel engine with an upper MPC layer to account for the SCR catalyst and a lower MPC layer to control the engine. The resulting hierarchical MPC structure is able to solve the overall control problem in real-time on ECU level using suitable MPC formulations as well as interconnecting variables. The numerical solution is based on an augmented Lagrangian MPC algorithm and control-oriented models. Simulation results against a detailed reference model of the overall system demonstrate the high performance of the hierarchical MPC concept.

Combined removal experiment of NOx, SO2 and PM from marine diesel exhaust gas with SCR-DryEGCS system

“…Tier III is only applicable to vessels operating in NOx Emission Control Areas (NECA), when sailing outside of NECA they must meet Tier I or Tier II requirements. 7 However, the treatment of NOx is relatively difficult 8 and there are currently two main technologies to reduce the NOx emission from ship exhaust to the IMO Tier III emission standard, namely selective catalytic reduction (SCR) 9–13 ,exhaust gas recirculation (EGR). 14–18 However, in terms of technical maturity and scope of application, SCR technology is the only IMO-approved NOx reduction technology that can be used on a wide range of ship engines and ship types.…”