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Hybrid Powertrain Choices for Emerging Engine Technologies
ISSN: 0148-7191, e-ISSN: 2688-3627
To be published on April 14, 2020 by SAE International in United States
US department of energy estimates the peak efficiency of a modern spark ignited naturally aspirated Otto cycle engine to be 36%. Atkinson cycle engines are estimated to get 40% peak efficiency. Most engines can achieve this peak efficiency only for a limited operating region. Hybrid powertrains enable engine to operate in this efficiently. Overall efficiency is improved by shutting down engine during idle events and by adjusting the operating speed and load on the engine using electric machines. The choice of the powertrain and component sizes depends on the engine characteristics, drive cycles and vehicle technical requirements. This study examines what type of powertrains will be suitable for more efficient engines that are likely to be available in the near future. Some of these technologies achieve higher efficiency with a trade off on power or by accepting a more restrictive operating region. An appropriate powertrain choice can still enable such an engine to be a viable option for an automobile. Using simulation tools, 14 different engine technologies are evaluated in this paper for their fuel saving potential. These engines vary in their speed, torque and fuel consumption characteristics. Autonomie, a simulation tool developed at Argonne national laboratory, is used in this study. Vehicle models are created using these advanced engines with various transmissions and powertrain choices for 5 different vehicles classes. Sensitivity of fuel consumption to drive cycles is also evaluated. This analysis quantifies the fuel saving potential of each powertrain considering the technology changes that are expected in engines and transmissions.