| Summary: | An air hybrid vehicle is an alternative to the electric hybrid vehicle that stores the kinetic
energy of the vehicle during braking in the form of pressurized air. In this thesis, a novel
compression strategy for an air hybrid engine is developed that increases the efficiency of
conventional air hybrid engines significantly. The new air hybrid engine utilizes a new
compression process in which two air tanks are used to increase the air pressure during the
engine compressor mode. To develop the new engine, its mathematical model is derived and
validated using GT-Power software. An experimental setup has also been designed to test the
performance of the proposed system. The experimental results show the superiority of the
new configuration over conventional single-tank system in storing energy.
In addition, a new switchable cam-based valvetrain and cylinder head is proposed to
eliminate the need for a fully flexible valve system in air hybrid engines. The cam-based
valvetrain can be used both for the conventional and the proposed double-tank air hybrid
engines. To control the engine braking torque using this valvetrain, the same throttle that
controls the traction torque is used. Model-based and model-free control methods are adopted
to develop a controller for the engine braking torque. The new throttle-based air hybrid
engine torque control is modeled and validated by simulation and experiments. The fuel
economy obtained in a drive cycle by a double-tank air hybrid vehicle is evaluated and
compared to that of a single-tank air hybrid vehicle.
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