Investigation and evaluation of potential exhaust braking strategiesusing model predictive control

• Main Author: Hallqvist, Erik
• Format: Others
• Language: English
• Published: KTH, Reglerteknik 2015
• Online Access: http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-175388

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. === Eektiviteten av dagens efterbehandlingssystem forlitar sig pa att avgasernaar inom ratt temperaturomrade. SCR-katalysatorn, som ar en del av efterbehandlingssystemet,har en arbetstemperatur som borjar vid ca 200 C. Narfordonet rullar utfor utan att forbranna bransle sa kan efterbehandlingssystemetkylas ner under arbetstemperaturen, vilket ger hogre utslapp vid forbranningav bransle igen. Detta examensarbete fokuserar pa att undersoka mojligheternaatt anvanda avgasbromen, en ventil mellan turbin och avgasefterbehandlingssystemet,i sluttningar och undersoka mojliga strategier. Avgasbromsen styrs medhjalp av prediktiv modellbaserad reglering vilket innehaller modeller av accelerationoch temperatur i forhallande till avgasbromstryck, massa och vaglutning.Olika strategier utreds och slutsatsen ar att det basta resultatet uppnas genomatt styra avgasbromsen for att halla konstant hastighet i backen. Men det nnsingen strategi dar endast avgasbromsen anvands som kan garantera att efterbehandlingtemperaturenhaller sig inom arbetsomradet.