This research investigates the effects of an electric turbocharger in a hybrid electric powertrain. First generic vehicle models are created and run to understand the overall powertrain requirements of torque, power and energy of a performance consumer vehicle. Then a low fidelity baseline model of a conventional vehicle is created in Simulink to serve as a baseline measure. To analyze an electric turbocharger system a high-fidelity model in AMESIM of a 4 cylinder turbocharged engine was modified. This engine model was analyzed using virtual dynamometer tests and a simplified look-up table based controller was developed for the electric motor within the electric turbocharger. Next this engine model was inserted within three different types of hybrid powertrain architectures models in AMESIM. Each hybrid powertrain required a unique supervisory controller which was developed using Stateflow in Simulink. These controller algorithms were imported into AMESIM and the model was simulated over standard drive cycles. Since a very wide variation of electrification level exists within hybrid powertrains the supervisory controllers are calibrated for charge-sustaining simulations. This allows for impartial comparisons across the hybrid architectures. Lastly a track drive cycle was developed to understand electric turbocharger effects under high performance loading conditions / Thesis / Master of Applied Science (MASc) / Turbochargers on internal combustion engines can utilize a portion of waste exhaust energy to pump more air into the cylinder leading to greater power and efficiency. A modern high performance 4-cylinder turbocharged engine is capable of replacing a V6 engine of much higher cylinder displacement. However turbocharged engines suffer from ‘turbo lag’ when the engine cannot immediately produce power. An electric turbocharger can virtually eliminate this ‘turbo lag’ as well as generate electricity from excess energy the turbocharger does not use. Electric turbochargers have been development by researchers and various automotive manufacturers. However the potential effects of such a system within the framework of a hybrid electric powertrain in a consumer vehicle has not been quantified. The objective of this research is to use high fidelity models to investigate the effects of an electric turbocharger system within a hybrid powertrain.

A major cause of CO2 emissions today is fossil fuel vehicles, and lowering these emissions is of key importance, resulting in increasing electrification and hybridisation nowadays. Turbochargers have been used for a long time to recycle exhaust gas heat losses to improve engine performance by compressing the intake air. This thesis investigates a turbocharger with an added electric machine, to see if further energy can be recovered from these gasses, as well as how to control this machine for improved transients during acceleration and reduced turbo lag. A complete Simulink model is created of the system, comprised of a variable geometry turbine, compressor, cylinder, electric motor and battery model. This plant model is then evaluated on test cycles, which results in consistently lowered brake-specific fuel consumption and quicker responses at the cost of electric charge. The results show that an electrically assisted turbocharger poses as a feasible option for further improvements in fuel economy and performance during transients for spark ignited engines.

Das Betriebsverhalten eines elektrischen Turboladers zur Bedruckung des Kathodengassystems eines automobilen Brennstoffzellensystems wird unter Berücksichtigung der feuchten Brennstoffzellenabluft untersucht. Basierend auf den Komponentenkennfeldern von Elektromotor, Leistungselektronik, Lagerung und Turbomaschinenkomponenten werden stationäre und transiente Betriebslinien berechnet, anhand derer eine Betriebspunktverschiebung gezeigt wird. Diese kann auf die Einflüsse der Gaszusammensetzung und Kondensation in der Turbine zurückgeführt werden. Anhand von drei stationären Betriebspunkten wird die Zusammensetzung der Verluste innerhalb der Maschine gezeigt. Die Verzögerung wird zudem als kritisches Manöver im transienten Betrieb durch signifikante Abnahme des Pumpgrenzabstands identifiziert. / The performance of an electric turbocharger for the cathode gas supply system of an automotive fuel cell system is investigated considering moist air off gasses. Based on the component performance maps of electric motor, power electronics, bearings and turbomachinery, steady state and transient operating lines are calculated and a shift of operating points is shown. These can be traced back to the influence of gas composition and condensation within the turbine. Based on three operating points, losses inside the machine are characterized. Furthermore, deceleration is identified as the most critical transient operating scenario due to a significant decrease of the surge margin.