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Rankine cycle for hybrid vehicles: The potential for CO2 emissions reduction

: Kraljevic, I.; Kollmeier, H.-P.; Spicher, U.


American Society of Mechanical Engineers -ASME-:
ASME Internal Combustion Engine Division Fall Technical Conference 2015. Proceedings. Vol.2: Emissions control systems; instrumentation, controls, and hybrids; numerical simulation; engine design and mechanical development : Presented at ASME 2015 Internal Combustion Engine Division Fall Technical Conference, November 8-11, 2015, Houston, Texas, USA
New York/NY.: ASME, 2015
ISBN: 978-0-7918-5728-1
Paper ICEF2015-1096, 10 S.
American Society of Mechanical Engineers, Internal Combustion Engine Division (ASME ICED Fall Technical Conference) <2015, Houston/Tex.>
Fraunhofer ICT ()

This paper presents the analysis of a Rankine cycle unit applied to improve overall efficiency of a hybrid electric vehicle (HEV). Exhaust waste heat is recovered from the internal combustion engine (ICE) and is converted into electrical power that is fed into the electrical system on board. The discontinuously available exhaust waste heat from the ICE operating cycle is stored as sensible heat in a pressurized working fluid applying the principle of a Ruths storage tank. Thus, it can provide almost constant mass flows to the expansion device during discharge in contrast to the standard Rankine cycle. It is also shown that the outlined system configuration leads to faster engine warm up resulting in optimum ICE operating conditions improving fuel economy. The benefits of a mild HEV versus conventional car powertrain are outlined step by step in a vehicle simulation. Additionally, improvement in fuel economy achieved by applying an additional Rankine cycle is demonstrate d in the New European Driving Cycle (NEDC).