Model-Based Control of Two-Stage Turbochargers for Heavy-Duty Diesel Engines
The concept of downsizing has proved to be a succesful method to improve engine efficiency. The engine key component is the turbocharging system that use excess energy in the exhaust gases to compress air into the cylinder. There are different types of supercharging systems, in the thesis a serial turbo system is modeled together with a complete six cylinder engine. A model-based controller is developed that regulates the intake pressure to a certain reference. The controller operates in modes that are defined by the engine operating point. To control the turbochargers it is necessary to have knowledge about the energy in the exhaust gases. A dynamic temperature model has therefore been analyzed, which has led to surprising results regarding the temperature measurements made in the test cells. This is analyzed and improvements are suggested.The engine model is validated and the system, including controller, is evaluated in certain simulations. The serial turbo concept is compared to a VGT turbo system, which gives a hint of the possible advantages of serial turbo charging.
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