Abstract
Basing on a symbolic program developed in MATLAB/Simulink, a parallel hybrid simulation model for the new system is developed in this paper. The simulation model includes all the system components such as the vehicle, the air tank, the accumulators, the pressure exchangers, the hydraulic pump/motor, the compressor and the internal combustion engine (ICE). The power management system is implemented based on using all the available hydraulic power. The main objective of this model is to evaluate the average fuel economy (FE) for the Hydraulic hybrid vehicle (HHV) with the added compressed-air system. This model is tested basing on the federal urban drive schedule (FUDS). The simulation results with various configurations have not shown a significant improvement in the fuel economy. This paper provides a detailed analysis about the results from the system structure and the energy losses. In this system, there are two alternating accumulators. Every time the accumulator switches to a reservoir, energy will be lost. When the engine drives the compressor to recharge the air system, a large engine would be needed to power such a compressor. These are the main reasons for the poor fuel economy of the proposed HHV system.
Keywords: Hydraulic Hybrid, Energy Density, Power Density, Fuel Economy, Compressed Air