Modeling and experiment of compressed air hybrid engines

Conventional internal combustion (IC) engines can be modified to run regenerative braking cycles that include air compressing (AC), air motoring (AM) and air power assisting (APA). Air hybridization has the potential to improve vehicle fuel economy at lower costs compared to electric hybridization. The dissertation work focuses on the modeling and experimental design of compressed air hybrid engines. The hybrid mode torque generation mechanism is analyzed utilizing P-V diagrams. Cylinder-tank interaction is modeled to gain insights for hybrid cycle optimization. Both torque control and cycle optimization are achieved through engine valve timing control. Thus, engine valve timing strategies for hybrid operations are proposed. The concept is demonstrated using a model engine system modified for hybrid operations. The framework is utilized in the hybridization design of a heavy-duty diesel engine. Detailed hybridization system design, modeling and simulation are carried out. The simulation results are incorporated with a vehicle model to predict the fuel economy improvement. The experimental system is built for cell tests. The test procedures and results are presented. As an extension, the concept and simulation work of 2-stage air hybrid are introduced.