Innovative Ram Air Turbine for Airborne Power Generation

Abstract

An innovative high power density and low drag ram air turbine for airborne power generation has been developed. Future systems on military and commercial aircraft will require greater electrical power. Unfortunately, expanding the capacity of the electrical systems on current aircraft and ones in development can result in costly design changes, require recertification, and significantly impact performance. Powering these systems locally with batteries is often considered. However, operation time is limited by the battery and the additional weight can limit aircraft range. The innovative ram air turbine design configuration described here has a power density that can be significantly higher than batteries and a lower drag and greater integration flexibility than conventional ram air turbines. Unlike batteries, which have a finite specific energy, the ram air turbine is only limited by the flight time of the vehicle. This system has a ducted turbine located in a pod or fuselage interior, unlike current ram air turbines that are externally mounted and require direct exposure to the free-stream flow. The internally mounted ram air turbine contributes less to overall aerodynamic drag than current ram air turbines, allows for more power to be extracted in an equivalent design space, and offers reduced radar signature compared to present externally-bladed turbines. Computational analyses along with wind tunnel testing have been conducted in support of this design. A 25-inch (0.635 m) diameter turbine demonstrated 110 kW of electrical power over a wide range of Mach numbers and simulated altitudes.