Rankine Cycle for Waste Heat Recovery of IC Engines

This paper deals with an analysis of the potential of the Rankine cycle as an additional power generation process, which uses the waste heat of a car engine. A review of different heat recovery technologies leads to the identification of the steam process as a favorable solution for automotive applications. Two basic configurations (exhaust gas only; exhaust gas plus coolant) are selected from numerous illustrated Rankine cycle layouts for a detailed evaluation of heat recovery based on a four-cylinder internal combustion engine (ICE). Furthermore, the impact of different working fluids is studied. A parametric analysis of the efficiency of two selected systems is accomplished with the Dymola simulation tool, followed by a direct comparison between both configurations for different engine technologies and vehicle speeds. Finally, test bench measurements of the applied engine coupled with a heat recovery device are carried out. It can be demonstrated that waste heat recovery can produce an additional power output of about 10% at typical highway cruising speeds.