An analytical investigation is proposed that aims to establish technical support for an automated engine control and facultative fuel injection system suitable for a candidate prop-drive power plant capable of providing propulsion for a very high altitude unmanned aircraft. The proposed system would provide full-authority digital control of the principal engine operating variables such as shaft speed, torque, injection timing and the like as well as starting sequences and parameter optimizations connected with operation on alternative fuels and available air. By these means, a facultative engine can be implemented whereby a highly variable amount of air can be efficiently utilized to conserve expendables to the benefit of payload, range, and endurance. The proposed system would be electrohydraulically operated and regeneratively cooled with circulated fuel thereby eliminating external cooling provisions and cumbersome mechanical drives and controls while providing convenient packaging and automation interfaces for remote command and control. The proposed investigation will examine the transient hydraulic effects, injection pulse profiles, turn-down range and design details of the components required to implement a common rail, solenoid-controlled electrohydraulic unit injection system subject to microprocessor control. Control algorithms, sensors and external signal interfaces will also be defined.
