Steady-state modeling of a turbocharger in gasoline engines

The gas flow estimation is crucial for the proper operation and monitoring of turbocharged (TC) engines with a torque structured engine control unit (ECU). This paper presents mean value models developed for modeling gas flow over the compressor, the turbine and the wastegate (WG) in a TC gasoline engine not equipped with a hot film air-mass flow meter (HFM). The turbine flow was modeled by an isentropic nozzle with an effective pressure ratio. A physically sensible model was developed for estimating the WG flow and its position which estimates them over a wide range of the engine operating conditions. Finally, a novel model for estimating the compressor air flow was proposed, using coupling between powers generated by the turbine and used by the compressor. All models are simple and accurate enough to be utilized for engine real-time control applications. Experimental results from a modern gasoline TC engine were used to validate all the models. Prediction results from models were in very good agreement with the experimental measurements.