Foundational Aero Research for Development of Efficient Power Turbines with 50% Variable-speed Capability

Report No. ARL-MR-0768
Authors: Gerard E. Welch, Gary J. Skoch, and Douglas R. Thurman
Date/Pages: February 2011; 32 pages
Abstract: Mission studies have shown strong potential to reduce in-theater casualties by using high-speed rotorcraft capable of both vertical takeoff and landing (VTOL) and high-speed, high-altitude, long-range cruising. The rotational speed of the prop-rotors on this type of vehicle must be slowed during forward flight to maintain high propulsive efficiency. One approach to meeting this requirement is to use a variable-speed power turbine (VSPT) to drive the prop-rotor. However, power turbines run most efficiently at high-speed and within a narrow speed range. The research and technology development effort described herein was funded by the U.S. Army Research Laboratory's (ARL) Director's Research Initiative award to develop the technology foundation needed for power turbines that operate efficiently over a speed range that may vary by as much as 50%. Results from this technology development effort are reported. Major barriers to VSPT operation and the approach selected for VSPT design are discussed. Results from the computational analysis and design system that has been assembled and validated are presented along with preliminary designs for VSPT incidence-tolerant blade sections. Technology transfer and future plans and collaborations, including performance evaluation using a turbine cascade and test rig or engine evaluations, are also discussed.
Distribution: Approved for public release
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Last Update / Reviewed: February 1, 2011