Optimization of a Heavy-Duty Hybrid Transit Bus Operated over Transient Cycles

This thesis centers on the simulation and optimization of a hybrid transit bus when operated over transient emissions cycles. The simulation was conducted using Powertrain System Analysis Toolkit (PSAT) as a platform by integrating components\u27 data and operation maps of a pre-transmission parallel hybrid transit bus. The model was validated against the limited experimental data when operated over the China\u27s Urban Bus (CUB) driving cycle and the Beijing cycle. The validated model was then used to predict the performance and exhaust emissions of this hybrid bus operated over typical U.S. cycles. The potential of a real-time control strategy in improving the performance and reducing the exhaust emissions was investigated. The significant effect of air conditioning (A/C) system on the fuel economy was examined using the A/C model developed in this research.;Compared to the operation with the baseline control strategy, the application of the conventional engine efficiency-based control strategy reduced the fuel consumption by 1.5%, 1.7% and -0.4% when operated over Central Business District (CBD) cycle, Manhattan Bus cycle, and New York Bus cycle, respectively; NOx emissions were reduced only by 5.6%, 5.6% and 0.4%, respectively. Simulation results indicated potential of the real-time overall efficiency-based control strategy in improving the performance of hybrid bus. Compared with the baseline control strategy, the real-time control strategy has the potential to reduce the fuel consumption and NOx emissions respectively by 8.1% and 6.1% when operated over New York Bus cycle.;The A/C model developed in this research was integrated into the PSAT model to investigate the effect of A/C system operation on the fuel consumption. The effects of ambient conditions (temperature, relative humidity, and solar radiation) and heat/humidity generation on board on the fuel consumption were investigated when operated over the featured summer weather of West Virginia, Arizona, and Florida. When operated over scaled SFTP-SC03 cycle, the operation of A/C system could increase the fuel consumption by 31.9%, 45.9%, and 50.2%, respectively