Potential of capturing transportation wasted heat for better fuel economy and electricity generation: Comprehensive testing

Abstract

This study is experimentally exploring the feasibility of organic Rankine cycle (ORC) as a waste heat recovery (WHR) technology in internal combustion engines, aiming at improving engine’s power, fuel consumption and CO2 emissions. Exhaust gases of a heavy-duty diesel engine are used as heat source of the ORC system. However, as the engine’s operating conditions vary, powertrain performance changes substantially. Therefore and in order to provide a thorough overview, the system was tested at different engine points. The expansion machine is a custom-designed radial inflow turbine that is operating with NOVEC 649 as the working fluid. In order to assure a steady state testing, a thermal oil loop was installed between the exhaust gas and the ORC loop. For a robust study, the test results were compared with CFD ones. The coupled engine-ORC system presented an expansion power, turbine efficiency and thermal efficiency of 7.6 kW, 48% and 6.2%, respectively, when the turbine is running at maximum speed. The results also revealed that ORC systems have a promising influence in reducing the fuel consumption of diesel engine and providing extra power. Maximum percentages of improvements of BSFC and powertrain power were, respectively, 2.74 and 7.8% compared to engine without ORC.