Specialized requirements exist for advanced high altitude unmanned air vehicles (UAV’s) capable of extended durations the propulsion units of which can only be served by either air-breathing highly turbocharged piston, and or, gas turbines engines with high thermal efficiency and light weight. These UAV requirements encompass ground surveillance, air sampling, and global atmospheric missions proposed in a variety of roles previously performed by larger manned aircraft. Some applications demand up to several days loitering endurance at altitudes over 65000ft, with which existing production propulsion engines are either incapable of meeting or require extensive modifications. Highly turbocharged piston engines and low specific fuel consumption turbofans have been developed for these specialized duties and record breaking global circumnavigation piloted aircraft. Recuperated cycle gas turbines thermal efficiencies of the order 40% are necessary to match those of current highly turbocharged piston engines which are difficult to attain with conventional uncooled metallic turbine rotors even at standard sea level day conditions. It is believed however that above the tropopause with sub zero air inlet temperatures, thermal efficiencies of 40% can rationally be attained with small relatively light weight recuperated gas turbine turboprops. The performance details and flowpath configuration of a two candidate recuperated turboprop designs are presented as specifically optimized for the propulsion of a long endurance UAV operating at 65000ft altitude, fueled with hydrogen.

This content is only available via PDF.
You do not currently have access to this content.