The LETHE™ Gas Turbine Hybrid Prototype Vehicle of the University of Roma 1: Drive Cycle Analysis of Model Vehicle Management Unit

The paper describes the logic of the vehicle’s power management unit (VMU) for the prototype configuration of the LETHE™ (low emissions turbo hybrid electric) vehicle designed by the University of Roma 1. The theoretical and practical feasibility of the concept (a series hybrid in which the thermal engine is a small turbo-gas and the traction is fully electric) was demonstrated in a series of previous works by the same authors, and some experimental tests were conducted at the ENEA-Casaccia Laboratories on a small 45 kW gas turbine set, to investigate the performance of the propulsive unit (turbine plus batteries and electrical motor) under the European vehicular emission (ECE) tests. After successful completion of these tests, a further analysis was carried out to identify an optimal hybridization ratio with respect both to driveability and fuel consumption: the results led to the conclusion that such an absolute optimal configuration does not exist, because not only the system performance, but also the absolute and relative sizes (i.e., nameplate power) of turbines and battery pack depend largely on the type of the proposed driving mission of the car. In the final configuration discussed in this paper, the vehicle is equipped with an additional energy storage device, a compact ultra-fast flywheel, to partially compensate for the low recharge capability of the Pb-acid batteries and to exploit better brake recovery for futher reduction of the fuel consumption. The present status report describes the VMU control logic, the individual components of the propulsive system and the proposed chassis configuration for the prototype.