An Investigation of Optimal Design of Hybrid Electric Vehicle with a Starrotor Engine

Abstract

Fuel economy of conventional hybrid electric vehicles (HEVs) gets limited improvements because of constraints from conventional internal combustion engines (ICEs). Electric vehicles (EVs) have the disadvantage of requiring large battery packs onboard. To overcome these problems, an HEV with a StarRotor Engine to replace the conventional ICE as the main power plant, which allows for a small battery pack, is proposed. The goal of this research is to develop an optimal design for the StarRotor Engine–based hybrid electric vehicle (SR–HEV) with minimal battery pack. The three most popular hybrid electric drivetrains are parallel, series and series–parallel, and each is studied in this research. All of them are fully analyzed for the purpose of maximally enhancing fuel economy.

A dynamic programming algorithm for optimal control of a dynamic model is implemented. The optimal control associated with the energy management is solved explicitly for each virtual hybrid electric drivetrain. The solution of the optimal control problem shows how optimal energy management strategies are derived. The same process is applied to conventional ICE HEVs to get the fuel economy to compare with SR–HEVs. The simulation indicates that the SR–HEVs can significantly increase vehicle fuel economy, and a series-parallel hybrid electric drivetrain with electric variable transmission (EVT) can provide better fuel economy among those drivetrains. An optimal design methodology is also presented for SR-HEVs in regards to fuel economy. A parametric study shows that the appropriate gear ratios can further improve the fuel economy for the SR–HEV with EVT.