Passenger car, Rankine cycle, new architecture, cooling engine, exhaust gas
Passenger cars roughly represent 12% of the CO2 emissions in EU. Passenger car gasoline engines present large losses in thermal energy (roughly 60% in engine coolant and exhaust gases). This paper presents a new architecture of organic Rankine cycle using both sources of heat to decrease the emissions of the car with the cooling engine fluid as working fluid. It allows to decrease the cost, the complexity, environmental and safety issues. In this paper, the main losses of the system are taken into account: under and over-expansion of the expander, bypass flow, thermal power at the condenser limitation and exhaust gas exchanger pinch-point. Two working fluids are considered (mixture of water and ethanol and mixture of glycol and water). New improvements of the cooling engine loop of passenger cars allow to reach 20 bar and 200°C, which are used as constraints in the simulation. First, a parametric study emphasizes the main losses of the proposed architecture and how to minimize them by adjusting control variables (fraction of bypass flow and pressure). Following this, the performance is presented in function of the speed of the vehicle. The simulations show a high benefit in terms of fuel consumption for speeds higher than 75 km/h. Following this, the consumption improvements are analysed on two driving cycles and are compared with other classical architectures. The maximum consumption decrease on a WLTP cycle reaches 6% with an optimal control and a steady-state model. This theoretical investigation shows the potential of this new architecture and would require experimental investigations to validate the promising results.