Transient Control of a Dedicated EGR Engine 2016-01-0616
Southwest Research Institute (SwRI) has successfully demonstrated the cooled EGR concept via the High Efficiency Dilute Gasoline Engine (HEDGE) consortium. Dilution of intake charge provides three significant benefits - (1) Better Cycle Efficiency (2) Knock Resistance and (3) Lower NOx/PM Emissions. But EGR dilution also poses challenges in terms of combustion stability, condensation and power density. The Dedicated EGR (D-EGR) concept brings back some of the stability lost due to EGR dilution by introducing reformates such as CO and H2 into the intake charge. Control of air, EGR, fuel, and ignition remains a challenge to realizing the aforementioned benefits without sacrificing performance and drivability. This paper addresses the DEGR solution from a controls standpoint. SwRI has been developing a unified framework for controlling a generic combustion engine (gasoline, diesel, dual-fuel natural gas etc.). The controller is factored into three parts - (a) The first part is physics-based and it incorporates engine topology to formulate a dynamical model connecting flows (air, EGR etc.) to engine states (pressure, oxygen fraction etc.). This part of the controller essentially inverts the dynamical model to determine flows to drive states to targets. (b) The second part is experimental and it synthesizes a multi-port device description connecting actuators to individual flows. (c) The third part pertains to fueling and ignition. The fuel quantity and split is based on the states (such as oxygen mass and oxygen fraction). The ignition timing and energy is based on the fuel quantity and the states (incorporating such effects as EGR dilution, fuel dilution, and presence of reformates). In this paper, an overview of the controller architecture and its successful application to a DEGR engine is presented.