A hybrid propulsion system for a passenger car is described and its preliminary design and performance discussed. A gas turbine operating in a controlled on-off mode, a generator, a battery pack, an inverter, and an electric motor constitute the power system, with an electronic vehicle management unit supervising the system for control and regulation. Road simulation tests are presented, based on standard ECC driving mission cycles. The turbogas performance might be improved adopting ceramic blades, with a possible increase of the TIT (turbine inlet temperature), and a consequent increase of its efficiency. The paper reports on the first results of a study in progress, within a joint research program between the University of Roma 1 “La Sapienza” and the Italian Research Centre of ENEA-Casaccia.

A hybrid propulsion system of new conception for medium-size passenger cars is described and its preliminary design developed. The system consists of a turbogas set operating at fixed rpm, and a battery-operated electric motor that constitutes the actual “propulsor”. The battery pack is charged by the thermal engine which works in an electronically controlled on/off mode. Though the idea is not entirely new (there are some concept cars with similar characteristics), the present study has important new aspects, in that it bases the sizing of the thermal engine on the foreseen “worst case” vehicle mission (derived from available data on mileage and consumption derived from road tests and standard EEC driving mission cycles) that they can in fact be accomplished, and then proceeds to develop a control strategy that enables the vehicle to perform at its near–peak efficiency over a wide range of possible missions. To increase the driveability of the car, a variable-inlet vane system is provided for the gas turbine. After developing the mission concept, and showing via a thorough set of energy balances (integrated over various mission profiles), a preliminary sizing of the turbogas set is performed. The results of this first part of the development program show that the concept is indeed feasible, and that it has important advantages over both more traditional (Hybrid Vehicles powered by an Internal Combustion Engine) and novel (All-Electric Vehicle) propulsion systems.