Model Predictive Control for Low Pressure Exhaust Gas Recirculation with scavenging

Abstract

Low-Pressure Exhaust Gas Recirculation (LP-EGR) has been shown to be an effective means of improving fuel economy and suppressing knock in downsized, boosted, spark ignition engines. However, the transport delays inherent in LPEGR systems can lead to combustion instability and misfire during tip-out events. This paper implements a Linear Time-Varying (LTV) Model Predictive Control (MPC) to track transient demand in LPEGR rates, while limiting EGR in the intake manifold at lower loads. The LTV-MPC leverages high overlap causing short-circuit flow behaviour through the cylinders that may improve EGR evacuation rates. The controller is tested in simulation for representative tipout transients. The amount of torque demand preview required to satisfy the constraint on intake manifold burned gas is investigated, and the benefit of including high overlap valve timing is assessed.