Simultaneous Control Optimization of Variable-Geometry Turbocharger and High Pressure EGR on a Medium Duty Diesel Engine

This research examines the interdependence of the control strategies of a high-pressure exhaust gas recirculation (HP-EGR) and a variable geometry turbocharger (VGT) on a medium-duty diesel engine in transient load operation. The effect on fuel economy, particulate and NO production were investigated through multiple tests of synchronously controlled VGT and EGR positions. An optimal steady-state strategy of the above determinants was defined as a function of the VGT’s boost pressure and EGR percent mass. The optimal steady-state strategy was then used to investigate the interdependence of the VGT and HP-EGR in transient load acceptence events which occurred over a range of 2 to 10 seconds. The faster transients increased deviations of boost and EGR levels from steady-state calibration values which consequently led to corresponding fuel consumption and particulate matter emission increases. These tests established that under the transient conditions the control strategies implemented in this work led to reduced boost pressure and increased EGR relative to the optimum steady state values. With this established, proactive EGR and VGT control policies were developed with the goal to minimize this transient degradation. Policies which advanced VGT and retarded EGR actuator openings were able to recover up to 75% of the degradation during the most rapid transient load acceptance.