Control of a turbocharged Diesel engine fitted with high pressure and low pressure exhaust gas recirculation systems

Exhaust gas recirculation is an effective way for reducing nitric oxides emissions in Diesel engine achieving low temperature combustion (LTC). Two strategies can be applied to recirculate burnt gas in a turbocharged Diesel engine using the high pressure loop or the low pressure loop. This paper describes a generic model based control structure for Diesel engines with dual-loop exhaust gas recirculation (EGR) and variable geometry turbocharger. An observer is designed to estimate the exhaust gas flow coming from the high pressure loop or from the low pressure loop. These estimates are used for the intake burnt gas fraction control. This approach avoids direct measurement or implementation of additional sensors. In addition, a generic model based control based on motion planning is adapted to the low pressure EGR system. The main advantage of the approach is that turbocharger and exhaust gas recirculation systems controllers have a limited number of calibration parameters. The observer and controller results are presented and validated on a LTC-Diesel engine with a dual-loop EGR system.