Exploration of Novel Powerplant Architectures for Hybrid Electric Helicopters

Abstract

A comprehensive survey of power source choices for helicopter use is presented. Using the University of Maryland helicopter sizing code, several powerplant and drive options including electric batteries, fuel cells, gasoline and diesel powered piston engines, turboshaft engines, electric generators, and electric motors are evaluated for two helicopters: a two-seat 600 kg class helicopter similar to the Robinson R22 (payload of 180 kg and endurance of about 2 hours) and a 1700 kg class helicopter similar to the EC120 (payload of 400 kg and endurance of about 4 hours). Recent developments in diesel and gas turbine powered electric generators (Range Extender) and integrated electric motor-gear boxes are surveyed and evaluated for helicopter use. A survey of electric motors and integrated gear boxes shows the availability of geared electric motors with high specific powers. The objective is that the alternate-powered helicopters should have the same payload, range and endurance capabilities as the baseline helicopters. Parametric studies are conducted with various power sources including IC engines, battery, fuel cell, range extender, integrated electric motor and gear box. These results show that the pure diesel engine option is an attractive fuel efficient option for both helicopters. The diesel hybrid electric option results in a heavier helicopter that has higher fuel consumption. However, all these options have lower take-off weights than the existing baseline helicopters and the hybrid diesel electric option can be a practical lead-in for a pure electric helicopter.