An Illustrative Look at Energy Flow through Hybrid Powertrains for Design and Analysis 2015-01-1231

Improving fuel economy and overall vehicle emissions are very important in today's society with strict new regulations throughout the world. To help in the education process for the next generation of design engineers, this paper seeks to define a powertrain model created and developed to help users understand the basics behind hybrid vehicles and the effects of these advanced technologies.

One of the main goals of this research is to maintain a simplified approach to model development. The 1 Hz model described within this work aims to allow energy to be simply and understandably traced through a hybrid powertrain. Through the use of a “backwards” energy tracking method, demand for a drive cycle is found, and, after tracing the energy demand through each powertrain component, the resulting fuel to meet vehicle demand and associated powertrain losses is found. Various energy management strategies are developed and explained including controls for regenerative braking, Battery Electric Vehicles (BEV), and Thermostatic and Load-following Series Hybrid Electric Vehicles (SHEV). These strategies can be easily compared and manipulated to understand the tradeoffs and limitations of each.

After validating this model, several studies are completed, including looking at a parameter known as Power Split Fraction (PSF) and how it affects overall powertrain efficiency. Since the goal with advanced vehicle powertrains is to increase overall system efficiency and reduce overall energy consumption, it is important to understand how all of the factors involved affect the system as a whole. Overall, this work seeks to provide an educational tool and aid in the development of the automotive engineers of tomorrow.