| Air Charge Estimation in Turbocharged Spark Ignition Engines (2009) | |||||||||||||
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| Turbocharged (TC) spark-ignited (SI) engines are popular as they combine high power output with good fuel economy. Furthermore, their emissions can be successfully reduced using a three way catalyst (TWC) provided that the airfuel ratio is precisely controlled. As the air-fuel ratio depends on the precision of the air charge estimate, this thesis is devoted to the systematic improvement of the cylinder air charge (CAC) estimation on TC SI engines. A second objective is to provide the design engineer with a flexible framework for CAC estimation that easily can be adapted to various engines. The CAC is not measurable and it is therefore estimated using a model. Part I concentrates on stationary conditions and examines existing air charge estimation methods using engine experiments where the wastegate is opened and closed. Measurements show that the existing methods are insufficient for TC SI engines since the CAC depends on exhaust backpressure and charge cooling from evaporating fuel. A new 2-parameter CAC model which accounts | |||||||||||||
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