Nonlinear model predictive control applied to multivariable thermal and chemical control of selective catalytic reduction aftertreatment

Abstract

Manufacturers of diesel engines are under increasing pressure to meet progressively stricter NO x emission limits. A key NO x abatement technology is selective catalytic reduction in which ammonia, aided by a catalyst, reacts with NO x in the exhaust stream to produce nitrogen and water. The conversion efficiency is temperature dependent: at low temperature, reaction rates are temperature limited, resulting in suboptimal NO x removal, whereas at high temperatures, they are mass transfer limited. Maintaining sufficiently high temperature to allow maximal conversion is a challenge, particularly after cold start, as well as during conditions in which exhaust heat is insufficient, such as periods of low load or idling. In this work, a nonlinear model predictive controller simultaneously manages urea injection and power to an electric catalyst heater, in the presence of constraints.

Computational Study of Urea–Water Solution Sprays for the Analysis of the Injection Process in SCR-like Conditions

“…Proper understanding of the UWS dosing system and the spray development is of high importance because inadequate injection processes could lead into the formation of urea deposits in the engine exhaust line that could result in increasing line pressure drop, blockage of the pipe, and low NO x conversion. , Moreover, the need of properly mixing and evaporating UWS in small distances plus its decomposition into NH 3 leaves very little time for the process prior to SCR to be completed. , …”

NOx sensor cross sensitivity model and simultaneous prediction of NOx and NH3 slip from automotive catalytic converters under real driving conditions

“…Hsieh and Wang 17 used an extended Kalman filter (EKF), which based on the stochastic character of EKF and a cross sensitivity factor, made it possible to estimate the actual N O x and capture the cross sensitivity behavior. Zhang et al 18 presented the advantages of the nonlinear Luenberger observer over several existing approaches to estimate the cross sensitivity and Sowman et al 19 applied a nonlinear model predictive control (NMPC) in the SCR catalyst, to simultaneously manage the urea injection and heating of the catalyst, as result, an ideal trade-off that minimizes the consumption of urea and electrical energy was obtained.…”

Special issue: Symposium for combustion control 2019

“…The joint activity with the International Journal of Engine Research started in 2016 and underlined the scientific quality and high technical relevance of the presented work. The two previous special issues illustrated the spectrum of the conference, which ranged from advanced control concepts 1–4 to application-oriented contributions with on-road vehicle validation, 5 detailed control of the combustion process on a laboratory scale 6–9 to combustion process simulation. 10…”