Abstract
This paper focuses on the effects of HEV (Hybrid-Electric Vehicles) Powertrains on fuel economy and overall system efficiency. Three different hybrid-electric powertrains: Series; Parallel and Combined have been simulated on ADVISOR by the use of MATLAB platform. Three drive cycles, Urban Dynamometer Driving Schedule (UDDS), New European Driving Cycle (NEDC) and Highway Fuel Economy Transport Cycle (HWFET), were used to determine best Fuel Economy, Overall System Efficiency and Energy usage for each Powertrain.While Parallel Powertrain showed best fuel economy and system efficiency at lower speeds (20 mph) during frequent start-stops, Combined Hybrid showed much more significant fuel savings at constant speeds above 48 mph. In situations where both battery and engine power were required simultaneously, Combined Hybrid showed much higher system efficiency giving credence to its PowerSplit device. In conclusion, the selection of the preferred Powertrain for Hybrid Electric application depends strictly on the application required. The results clearly show that advantages of both Series and Parallel powertrains have not been effectively harnessed in the Combined Powertrain as expected. This highlights the need for a Powertrain which effectively saves fuel at all speeds irrespective of number of idle times or stops.
 Keywords: Hybrid electric vehicle; zero emissions; combined hybrid; series hybrid; parallel hybrid; electric vehicles; fuel cells
Highlights
Instead of comparing strength and weaknesses of existing hybrid electric vehicles (HEVs) powertrains, most research papers focus on building newer powertrains comparing their benefits over conventional vehicles. Meisel Jerome (2006) highlights the advantages of the Toyota hybrid system over conventional vehicles but fails to mention how it differs from other hybrid powertrains. Chachra and Bhartendu (2008) mention inefficiencies of Series and Combined hybrids but falls short of when these inefficiencies occur
It was designed as an analysis tool to assist the U.S Department of Energy (DOE) in developing and understanding hybrid electric vehicles (HEVs) through the Hybrid Vehicle Propulsion System contracts with Ford, GM, and Chrysler
Combined hybrid operated predominantly with the engine power while Series and Parallel powertrains relied on both engine and motor power
Summary
Instead of comparing strength and weaknesses of existing HEV powertrains, most research papers focus on building newer powertrains comparing their benefits over conventional vehicles. Meisel Jerome (2006) highlights the advantages of the Toyota hybrid system over conventional vehicles but fails to mention how it differs from other hybrid powertrains. Chachra and Bhartendu (2008) mention inefficiencies of Series and Combined hybrids but falls short of when these inefficiencies occur. This research attempts to determine the best HEV (Hybrid Electric Vehicle) Powertrain topology in terms of fuel economy, emissions and overall system efficiency over different drive cycles. In Parallel propulsion, power supplied by the gasoline engine and electric motor can be applied to move the wheels (Singer-Englar et al, 2005). Electric power can be applied independently from the battery through motor to gears to wheels. The power split device made up of planetary gear set is what defines a combined Hybrid This feature combines a series-parallel configuration that utilises advantages of both Powertrains (fig.). This feature combines a series-parallel configuration that utilises advantages of both Powertrains (fig.3) It splits power from the engine into two routes: mechanical and electrical (Meisel, 2006). Just like Parallel type both engine and motor can apply torque independently to move the wheels
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