Fuel Saving Potential of Different Turbo-Compounding Systems Under Steady and Driving Cycles

The performance of three different electric turbo-compounding systems under both steady and driving cycle condition is investigated in this paper. Three configurations studied in this paper are serial turbo-compounding, parallel turbo-compounding and electric assisted turbo-compounding. The electric power, global gain of the whole system (engine and power turbine) under steady operating condition is firstly studied. Then investigation under three different driving cycles is conducted. Items including fuel consumption, engine operating point distribution and transient response performance are analyzed among which the second item is done based on statistic method combined with the results obtained under steady operating conditions. Study under steady condition indicates that electric assisted turbo-compounding system is the best choice compared with the other two systems. The performance of serial turbo-compounding is load oriented while parallel configuration is speed oriented. Research under driving cycles shows that performance differs greatly according to driving cycles considered for the same turbo-compounding system though all the turbo-compounding systems is capable of enhancing the fuel economy. Electric assisted turbo-compounding is still the best no matter what driving cycle is considered. Serial system shows much better performance than parallel configuration because more operating points falls in the region corresponding to significant improvement of overall fuel conversion efficiency (including the power recovered by power turbine). What is more, the electric assisted turbo-compounding system shows much better transient response performance than the other two systems. Serial configuration is more suitable for the driving cycle characterized by frequent vehicle speed change compared with parallel layout.