Modeling of Compressed Air Hybrid Operation for a Heavy Duty Diesel Engine

This paper presents the analysis and modeling of a 10.8 l heavy-duty diesel engine modified for operating compressed air hybrid engine cycles. A lumped parameter model is developed to first investigate the engine cylinder-air tank mass and energy interaction. The efficiency of compressed air energy transfer is defined based on the second law of thermodynamics. A high fidelity model is developed using commercially available software (GT-POWER) to capture the effects of engine friction, heat transfer, gas dynamics, etc. Engine valve timing for optimal efficiency in air regeneration and the corresponding engine speed-torque maps are established using the detailed engine model. The compressed air hybrid engine maps are then incorporated into vehicle simulation (ADVISOR) to evaluate the potential fuel economy improvement for a refuse truck under a variety of driving cycles. Depending on the particular driving cycle, the simulation has shown a potential 4–18% fuel economy improvement over the truck equipped with the conventional baseline diesel engine.