Convex modeling and optimization of a vehicle powertrain equipped with a generator-turbine throttle unit

This paper investigates an internal combustion (gasoline) engine throttled by a generator-turbine unit. Apart from throttling, the purpose of this device is to complement the operation of a conventional car alternator and support its downsizing by introducing an additional source of energy for the electric auxiliaries. Its energy recovery potential is examined by employing a novel, convex approach to modeling and optimization of the resulting vehicle powertrain. For a given gear-shifting strategy, the proposed method allows the computation of optimal control trajectories, e.g., the optimal engine fuel, alternator, and turbine power, as well as of optimal design parameters, i.e., the optimal battery, alternator and turbogenerator size. The conducted numerical case study shows that a generator-turbine throttle unit has a potential to reduce the total operational (fuel) and component (battery, alternator, and turbogenerator) costs by typically 2%-6%, depending on factors such as the engine size and the choice of a driving cycle.