Optimization of Fuel Economy for a Multimode Plug-in Hybrid Electric Vehicle using Atkinson Thermodynamic Cycle Engine
Keywords:Hybrid Electric Vehicle, Plug-In, PHEV, Powertrain, Fuel Economy, Multimode, Mode Switching, Optimization
Recently, Plug-in Hybrid electric vehicles become a sustainable solution to strike a balance between performance and fuel economy. For a multimode PHEV, the car switches among three operation modes; namely electric mode, series mode, and parallel mode to maximize fuel economy based on the driving conditions. Atkinson thermodynamic cycle has a higher expansion stroke compared to Otto cycle; which leads to more work, less emissions and higher thermal efficiency. In this work, the optimization of fuel economy for a multimode PHEV reference vehicle that resembles Honda Accord PHEV using Atkinson engine is conducted. The optimization is based on a combined driving cycle that includes both a city cycle and a highway cycle. Mapping technique is used to represent performance and fuel consumption of Atkinson engine. The mapping is calibrated to match Honda Accord PHEV performance data. Global generalized pattern search optimization method is utilized. The optimization is performed in two steps. In the first step, the driving mode-switching strategy is optimized to increase overall equivalent Miles-per-Gallon () for the combined driving cycle. In the second step, powertrain components are re-sized to further improve equivalent fuel economy. Optimization of driving mode-switching increased from 48 to 64.5 (30% increase) and a further 10% increase to 70.5 is achieved by powertrain components sizing optimization. The developed optimization method proved to be a viable method to improve fuel economy of hybrid vehicles.