Simulation Based Evaluation of Simple Hybrid Electric Topologies for a Small Two-Wheeler for Characterizing the Performance and Emission Benefits

Electrifying powertrains has become vital to improve overall efficiency and reduce greenhouse gas emissions when the Internal Combustion Engine (ICE) is the prime power source. Though scooters are popular among Asian countries for personal transportation, they suffer from losses because of fluctuating load and speed and use of the Continuously Variable Transmission (CVT). The parallel hybrid drive concept has shown significant benefits in cars but has not found its way significantly in two-wheelers. This work focuses on quantifying the improvements in powertrain efficiency of a scooter, by adopting simple parallel electric hybrid layouts and also simultaneously eliminating the CVT. Two drive versions are evaluated, one using a single speed ratio and the other using two speed ratios. Validated simulation models of the sub systems have been integrated in order to evaluate the fuel consumption, grade-ability, acceleration and emissions of these drives and compare them with the conventional ICE + CVT based powertrain under the World Motorcycle Test Cycle. A rule based control strategy is used. The influences of the power capacity of the EM, battery capacity have also been studied. Even though significant benefits in fuel economy can be realized a trade-off exists with NOx emissions. Thus the work brings out the benefit of using simple powertrain layouts to hybridize a small two-wheeler.