The gradual push towards electric vehicles (EV) as a primary mode of transport has resulted in an increased focus on electric and hybrid powertrain research. One answer to the consumers’ concern over EV range is the implementation of small combustion engines as generators to supplement the energy stored in the vehicle battery. Since these range extender generators have the opportunity to run in a small operating window, some engine types that have historically struggled in an automotive setting have the potential to be competitive.
The relative merits of two different engine options for range extended electric vehicles are simulated in vehicle across the WLTP drive cycle. The baseline electric vehicle chosen was the BMW i3 owing to its availability as an EV with and without a range extender gasoline engine.
Two different range extenders were considered; a single rotor Wankel rotary and a 4-stroke reciprocating engine, with the baseline vehicle electric glider mass fixed for all options. Fuel tank capacity was fixed at 9 litres. Baseline EV performance was evaluated on simulated European drive cycles with mass sensitivity conducted before the implementation of each range extender.
Potential options for the optimisation of the range extender operation were considered with respect to their impact on vehicle performance. Total combined fuel efficiency was compared and an assessment of maximum range and vehicle performance was also conducted.