Turbochargers stand for the dominating dynamics in engines and in the design, analysis, and optimization of new engines, it becomes more and more important to analyze system interactions and dynamics. In the development process, modeling, simulation, and optimization have evolved from being used in research to being stan- dard tools for engineers and play an important role in the engine development. To be successful in the process, one needs to both have component models, and methods and tools where system models can be built, analyzed, and optimized. The component models should also have capabilities to extrapolate behavior outside the nominal re- gion since design explorations can go to extreme points while searching for optimal solutions.

The first part of the chapter summarizes the compressor and turbine maps and how they can be used in simulation models. A generic model structure for compressors and turbines that fit into an engine modeling and simulation framework is described. Then the Ellipse compressor flow model and the Enthalpy based efficiency model will be described, they have been developed so that they can be integrated in a simulation environment and also used in optimization. Their main features are that they are ca- pable of extrapolating compressor behavior outside the normal range of the map in a physically sane way. In addition to this, a tuning method has been developed that takes a normal manufacturer map and returns all model parameters for compressor flow and efficiency models. Thereafter, compact turbine flow and efficiency models will be described.

Then the attention is turned to simulation and optimization applications where compressor models are used. First an engine experiment where compressor surge oc- curs is modelled and used to illustrate the extrapolation capabilities using the models presented. Then the scope is turned to control and optimization of turbocharger opera- tion on an engine, where the focus will be on a VGT controlled diesel engine equipped with EGR. First the steady state mapping of the engine is demonstrated, then optimal control of the turbo operation is investigated using modern computer tools for dynamic optimization.