Study on exergy recovery in hybrid vehicles via wastegate losses

Vehicle hybridization is considered a promising alternative for pollutant emission mitigation. This type of vehiclecombines the use of an internal combustion engine and electrical power. One of the most common layout is theseries-parallel hybrid vehicle, which consists of the use of one combustion engine as the main source of power inparallel to electrical sources. Besides propelling the vehicle, the combustion engine has the task of supplying energyto the electrical system. In parallel to hybridization, other technologies, such as the downsizing of an engine viaturbocharging, have been adopted to increase thermal efficiency of internal combustion engines. The purpose of thiswork is to analyse the viability of combining the aforementioned technologies. To improve energy utilisation, part ofthe energy of the exhaust system is recovered from a free turbine, being directed to the vehicle's battery. To evaluatethe viability of the proposal, experimental data was obtained from a turbocharged spark-ignition engine. Efficiencyindexes were calculated based on exergetic analyses for the turbo-compressor set and the entire engine system.Thereafter, a virtual free turbine was virtually added, assuming that it operates exactly as the main turbine and theefficiency indexes were re-calculated as also absolute values of the recovered energy. The comparison of resultsindicates the viability of implementing this proposal.