Thermodynamic analysis and fluids screening for a gasoline engine exhaust heat recovery system

This study explores the possibility of increasing the power output and improving the fuel economy of an internal combustion engine by employing a Rankine cycle driven by the engine exhaust. Engine exhaust energy is analyzed based on the brake power output and exhaust temperature of a 2.0DCVVT engine. The quantitative and qualitative analysis of exhaust energy was conducted on the basis of the first and second laws of thermodynamics. The effects on the efficiency of heat recovery of the parameters of various states of the working fluids were also studied. The results of the theoretical studies give a good indication of the overall efficiency of the Rankine cycle. In addition, an appropriate working fluid for the recovery system was also investigated and selected. Among the working fluids investigated, water shows the best work potential when water is heated over 500 degrees C, the total system efficiency is over 22%, and the system net work (W-net) is above 13 kW (up to 14.5 kW), all of which can increase the petrol engine output by more than 14.5%. (C) 2014 AIP Publishing LLC.