Investigation and evaluation of potential exhaust braking strategiesusing model predictive control

Abstract: The eciency of today's aftertreatment system relies on the exhaust gas temperature.The Selective Catalytic Reduction system, which is a part of theaftertreatment system has an operating temperature window which starts atapproximately 200C in order to work as eciently as possible. Rolling downhillwithout burning fuel could cause the exhaust aftertreatment system to cooldown below this window, which gives higher emissions when burning fuel again.This thesis focuses on investigating the potential of using the exhaust brake, athrottle between the turbine and the exhaust aftertreatment system, in slopesand investigates and evaluates possible strategies. The exhaust brake is controlledusing Model Predictive Control with models of acceleration and temperaturewith respect to exhaust brake pressure, mass and road incline. Dierentstrategies are investigated and it is concluded that controlling the exhaust braketo keep constant velocity down the slope gives the highest temperature at theexhaust aftertreatment system. It is also concluded that there is no strategywhich could guarantee the exhaust aftertreatment temperature to stay withinthe temperature window just using the exhaust brake.