Issues in modelling and control of intake flow in variable geometry turbocharged engines

This chapter considers one such situation when demands for increased engine power, improved fuel economy and drivability provide a rationale for utilizing a variable geometry turbocharger while emission regulations necessitate an external exhaust gas recirculation system. An automotive turbocharger consists of a compressor and a turbine coupled by a common shaft. The engine exhaust gas drives the turbine which drives the compressor which, in turn, compresses ambient air and directs it into intake manifold. Turbocharging also affects regulated engine emissions such as particulates (PM), oxides of nitrogen (NOx), hydrocarbons (HC) and carbon monoxide (CO). A turbocharger is typically sized to a particular engine so that it provides fast airflow response when the driver demands acceleration at low engine speeds. A control system for a diesel engine must meet driver torque demand while satisfying constraints on emissions.