A Turbocharged, Spark-Ignition Engine: Results From an Engine Cycle Simulation Including the Second Law of Thermodynamics

The use of turbocharging systems for spark-ignition engines has seen increased interest in recent years due to the importance of fuel efficiency, and in some cases, increased performance. An example of a possible strategy is to use a smaller displacement engine with turbocharging rather than a larger engine without turbocharging. To better understand the tradeoffs and the fundamental aspects of a turbocharged engine, this investigation is aimed at determining the energy and exergy quantities for a range of operating conditions for a spark-ignition engine. A 3.8 liter automotive engine with a turbocharger and intercooler was selected for this study. Various engine performance and other output parameters were determined as functions of engine speed and load. For the base case (2000 rpm and a bmep of 1200 kPa), the bsfc was about 240 g/kW-h. At these conditions, the second law analysis indicated that the original fuel exergy was distributed as follows: 34.7% was delivered as indicated work, 16.9% was moved via heat transfer to the cylinder walls, 23.0% exited with the exhaust gases, 20.6% was destroyed during the combustion process, 2.5% was destroyed due to inlet mixing processes, and 1.9% was destroyed due to the exhaust processes. The turbocharger components including the intercooler were responsible for less than 1.0% of the fuel exergy destruction or transfer.