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Advanced Durability Systems for UAS Propulsion


OBJECTIVE: Improve UAS engine durability by applying advanced designs/materials for bearing, housing, and rotating components/systems. DESCRIPTION: UAS propulsion systems currently suffer from durability issues resulting in frequent overhauls. Incorporating advanced durability systems could lead to longer durations between engine overhaul times and increased engine life, resulting in a larger payback per UAV investment. These advanced durability systems can be applied to bearings, rotating components and static components in order to increase the life and times between overhauls. Bearings are an essential part of all UAV systems. As technologies continue to advance in current air vehicles, more demands are being made on bearing capability. With an increase in the demand of bearing capacity comes an increased risk of bearing fatigue and wear caused by heavier loading, inadequate/unsuitable lubrication and overheating. Future engine improvements need to incorporate advanced bearing designs and concepts to increase bearing durability and, thus, increase time between overhaul for UAV systems. Examples of advanced durability concepts include but are not limited to ceramic ball bearings and fuel lubricated bearings. Ceramic ball bearings have advantages of higher operating speeds, increased stiffness, lower friction, and less heat generation. The incorporation of ceramic bearings into UAV systems has the capability to reduce wear on the bearings through an increase in engine durability. Further, fuel (JP-8) lubricated bearings offer substantial benefits resulting from the elimination of the conventional recirculating lubrication system. Metal matrix composites (MMC) offer added strength and durability that can be incorporated in both static components such as engine housings and rotating components, where ceramic matrix composites (CMC) also offer benefits with respect to heat transfer in the engine housing and reduction in engine weight. The benefits offered by composite and ceramic materials are high strength-to-weight ratios, high temperature tolerance, low coefficients of thermal expansion, low coefficients of friction, and favorable lubrication properties. The high strength-to-weight ratio is a favorable property for engine components as it reduces the rotational mass of the engine and increases the specific power. The low coefficients of expansion of these materials allow tighter tolerances between moving and static components of the engines, which could lead to increased durability and longer engine life. Applications for this technology include engine liners, coatings for combustion surfaces, bearing cages and housings, rotating shafts, pistons, and rotors. PHASE I: Define and determine advanced durability systems that can be incorporated into bearings, rotating components, and static components of engines to increase durability of current UAV propulsion systems. This may include but is not limited to ceramics, metal matrix composites, ceramic matrix composites, fuel (JP-8) lubricated bearings, and ceramic ball bearings. Applications should be oriented to UAV propulsion systems with the intent to increase engine durability and reliability upon implementation of these advanced durability concepts. Present day durability parameter for tactical UAV propulsion is $150/hr a 20% improvement is sought. PHASE II: Apply the concepts researched and developed in Phase I to a current UAV propulsion system. The advanced durability system should be incorporated in a relevant UAV engine and demonstrated in a laboratory environment. Small scale testing of these engines should show increased durability upon the implementation of advanced durability systems. PHASE III DUAL USE APPLICATIONS: Military Application: This technology is applicable to Air Force, Navy, and Army UAV systems. By implementing advanced durability systems such as ceramic bearings, fuel lubricated bearings, and composite structures, the durability of each UAV can be greatly increased, increasing overhaul time and operation for each aircraft. This has significant cost and efficiency savings for the DoD. Commercial Application: This technology has additional transition opportunities in the commercial sector. Performance is a key factor in the commercial industry and with an increase in performance of small engines comes durability issues such as fatigue and overheating of engine components. By applying advanced durability systems to the rotating components, static components, and bearings of commercial engines, performance can be greatly increased.
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