Estimation of transient intake burned gas and reformate mass fractions in a dedicated EGR engine

Abstract

An engine with a cylinder dedicated to providing enriched EGR (D-EGR) has been demonstrated by Southwest Research Institute (SwRI). A vehicle equipped with the D-EGR engine showed more than 10% of fuel economy improvement over various driving cycles. Despite a much higher level of EGR than a conventional engine, combustion in the engine is maintained stable since reformates such as H2 and CO from rich combustion increase dilution tolerance. Thus, it is deemed that precise real-time information of the level of reformates in the engine is critical to maintain stable combustion especially during transients. In this paper, a method to estimate intake burned gas and reformate mass fractions of the D-EGR engine is developed and validated through simulations. The estimated fractions can be used to control spark timing in real-time to prevent knocking or misfire during transients in the D-EGR engine.