Program Manager: Dr. William Coblenz
Small UAV payload and endurance capabilities can be expanded by increasing the power density and efficiency of their power plants. The goal of the Small Uninhabited Air Vehicle Engine (SUAVE) Program is to develop gas turbine engines under 10 HP with a power density greater than 2 HP/pound and a thermal efficiency greater than 25 percent.
Small gas turbine engines are typically very inefficient, below 7 percent for engines below 10 HP. Design issues related to the high surface-to-volume ratio of small engines increases thermal losses, friction, and tip clearance losses. Auxiliary equipment such as fuel pumps and generators are generally not available in sizes that scale with the engine. Additionally, the reduced transit time for combustion provides a special challenge in design of efficient combustors.
Significant effort has been made to increase the efficiency of gas turbine engines by substituting refractory ceramic components for metal components such as combustion liners, turbine blades, and vanes. Increases in the turbine inlet operating temperature enabled by these materials increase the Carnot efficiency of the engine. These programs have taken a substitution approach of replacing metal hardware for ceramics. The risk associated with this approach is designing for brittle failure in the ceramics.
This program seeks to combine new engine designs that are both favorable to the use of ceramic components and that address the design-related issues that lead to low efficiency for small engines, and new manufacturing technologies to reduce the cost and time for prototyping. The highest efficiency motors now available and used for air propulsion are about 1 HP/pound. The high-speed engines to be developed in this program will push the power density to as high as 5 HP/pound. The surface finish and geometric complexity of the ceramic components needed for SUAVE engines will push the state of the art in fabrication. One of the objectives of this program is to exploit the rapid prototyping capabilities developed in the Solid Freeform Program to the maximum extent possible, to reduce the cycle time for design, prototype, test, and evaluation.
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