System analysis of a Diesel Engine with VGT and EGR
2009 (English)Report (Other academic)
A system analysis of a diesel engine with VGT and EGR is performed in order to obtain insight into a VGT and EGR control problem where the goal is to control the performance variables oxygen fuel ratio and EGR-fraction using the VGT actuator and the EGR actuator. Step responses over the entire operating region show that the channels VGT to oxygen fuel ratio, EGR-valve to oxygen fuel ratio, and VGT to EGR-fraction have non-minimum phase behaviors and sign reversals. The fundamental physical explanation of these system properties is that the system consists of two dynamic effects that interact: a fast pressure dynamics in the manifolds and a slow turbocharger dynamics. It is shown that the engine frequently operates in operating points where the non-minimum phase behaviors and sign reversals occur for the channels VGT to oxygen fuel ratio and VGT to EGR-fraction, and consequently, it is important to consider these properties in a control design. Further, an analysis of zeros for linearized multiple input multiple output models of the engine shows that they are non-minimum phase over the complete operating region. A mapping of the performance variables oxygen fuel ratio and EGR-fraction and the relative gain array show that the system from EGR-valve and VGT to oxygen fuel ratio and EGR-fraction is strongly coupled in a large operating region. It is also illustrated that the pumping losses decrease with increasing EGR-valve and VGT opening for almost the complete operating region.
Place, publisher, year, edition, pages
2009. , 39 p.
LiTH-ISY-R, ISSN 1400-3902 ; 2881
diesel engine, VGT, EGR
National CategoryEngineering and Technology
IdentifiersURN: urn:nbn:se:liu:diva-18334ISRN: LiTH-ISY-R-2881OAI: oai:DiVA.org:liu-18334DiVA: diva2:218321