Optimization of the Overall Efficiency of a Combined Cycle Machine: A Methodology for Piston ICE Coupled to Brayton Cycle

Autoren

Dr.-Ing. Wissam Bou Nader, Dr.-Ing. Yuan Cheng, Dipl.-Ing. Sebastien Houille, Dipl.-Ing. Seyyid Ali Belmedrek, Dr.-Ing. Clément Dumand, Groupe PSA, Technical Center of Velizy, Vélizy-Villacoublay

Zusammenfassung

Waste heat recovery (WHR) systems constitute a promising solution for reducing vehicle fuel consumption in order to meet the reglementation targets by 2025. This paper presents a methodology to improve the efficiency of a combined cycle machine consisting
of a reciprocating internal combustion engine (ICE) and a bottoming intercooled Brayton cycle (IBC). It investigates the potential of calibrating the ICE at some specific points of the engine map in order to achieve an optimal overall efficiency when coupled to the bottoming IBC. A three cylinders gasoline engine is modeled using GT suite code and the effect of CA50 variation on exhaust gas temperature and engine brake efficiency are compared to real engine test bench values. A Series Hybrid Electric Vehicle (SHEV) model is developed and the IBC is coupled to the ICE where both operate as auxiliary power unit (APU). The simulated fuel consumption results show an interest in delaying the ignition to enable higher engine exhaust gas temperature and mass flow rate, which are more favourable for WHR system. The proposed method is also beneficial to avoid knocking problems and can enable in the futur the design of higher
compression ratio engines for APU on SHEV.

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