Internal Combustion Engines bottoming with Organic Rankine Cycles. A thermodynamic analysis.

In the paper a specific thermodynamic analysis is presented in order to efficiently match a vapour power cycle to a stationary internal combustion engine with a rated power output of 3MWe. Three different working fluids are considered to represent the main classes of fluids with reference to the shape of the vapour lines in the T-s diagram: overhanging, nearly isoentropic and bell shaped. A parameterized analysis is first conducted in order to determine the optimal evaporating pressure. Then three different cycles setups are considered: a simple cycle with use of only hot exhaust gases from the engine, a simple cycle with use of hot exhaust gases and engine cooling water to preheat the organic fluid and a regenerated cycle. A second law analysis of the cycles is performed with reference to the heat sources available in order to determine the best fluid and cycle configuration to be employed and the main parameters of the thermodynamic cycle as well as the overall efficiency of the combined power system.