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Abstract



Bypass Valve Modeling and Surge Control for Turbocharged SI Engines


Since measurements in engine test cells are closely coupled with high costs it is of interest to use physically interpretable engine models instead of engine maps. Such engine models can also be used to do off-line tests of how new or altered components affect engine performance. In the thesis an existing mean value engine model will be extended with a model of a compressor bypass valve. A controller for that valve will also be developed. The purpose with that controller is to save torque and boost pressure but at the same time avoid having the compressor entering surge during fast closing transients in the throttle position. Both the extension and controller is successfully developed and implemented. The extension lowers the pressure after the compressor and increases the pressure before the compressor when the bypass valve is being opened and the controller shows better results in simulations than the present controller used in the research lab. By using the proposed controller, as much as 5 percent higher torque can be achieved in simulations. Finally, there is a discussion on wastegate control alternatives and the use of TOMOC for optimization of wastegate control.

Eric Wiklund and Claes Forssman

2005

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