Design of a waste energy recovery turbine from the exhaust of a spark ignition hybrid vehicle

The objective proposed by EU to reduce about 4%/year the CO2 emission of internal combustion engines for the next years up to 2030, requires to increase the engines efficiency and accordingly improving the technology. Flue gas from the internal combustion engine equipping a vehicle contains residual energy that could be exploited by a gas turbine directly connected to an electric generator, thus improving the global efficiency of the vehicle. The perspective of adopting this solution in a full-hybrid vehicle is studied in this work. Here, a radial turbine is designed to be placed at the exhaust ducts of a 2000 cc spark ignition engine, and its performance are simulated. The use of a gas turbine affects the fluid dynamic behavior of the exhaust gases, hence an evaluation of the performance and consumptions of the thermal engine in this new configuration have been made. It is assumed that the energy recovered from the exhaust is stored in the vehicle battery and used to power the auxiliaries. The benefits in terms of fuel consumption have been calculated in a standardized driving cycle. In the hybrid configuration, a consumption reduction larger than 20% is computed, thanks to the kinetic recovery. If an exhaust recovery turbine is adopted, an additional 3.8% fuel consumption reduction is achieved.