Performance analysis of a novel system combining a dual loop organic Rankine cycle (ORC) with a gasoline engine

An organic Rankine cycle (ORC) can be used to harness the wasted heat from an internal combustion engine. In this paper, the characteristics of a novel system combining a gasoline engine with a dual loop ORC which recovers the waste heat from both the exhaust and coolant systems is analyzed. A high temperature loop recovers the exhaust heat while a low temperature loop recovers both the residual high temperature loop heat and the coolant heat. The performance map of a gasoline engine is measured on an engine test bench and the heat quantities wasted by the exhaust and coolant systems are calculated and compared within the engine's entire operating region. Based on this data, the working parameters of a dual loop ORC are defined, and the performance of a combined engine-ORC system is evaluated across this entire region. The results show that the net power of the low temperature loop is higher than that of the high temperature loop, and the relative output power improves by from 14 to 16% in the peak effective thermal efficiency region to 50% in the small load region, and the absolute effective thermal efficiency increases by 3-6% throughout the engine's operating region.