Description:
OBJECTIVE: To develop, and demonstrate improvements in cooling capability of propulsion systems currently in use on unmanned aerial vehicles (UAV); to show a 20% reduction in cooling efficiency. DESCRIPTION: Two of the most popular UAVs used in the US are the US Air Force"s Predator, and the US Army"s Shadow 200. The US Air Force Predator is classified as a medium altitude, long endurance UAV and is powered by a 100 HP 4-cylinder piston engine. The US Army"s Shadow 200 is a tactical UAV and is powered by a 38 HP rotary engine. Both of these propulsion systems suffer durability issues which can be linked to undesirable heat transfer within the engine. Moreover, desired increases in engine power or improvements in engine efficiency are limited by thermal loading in the engine. This topic will focus on the development of improved cooling methodologies for the above mentioned engines. The piston engine relies primarily on liquids as the cooling medium (oil and engine coolant) while the rotary engine rejects heat directly to the airstream. A solution is sought to better manage internal heat transfer which can be applied to either engine. Proposed solutions should be consistent with the desire to increase engine power, improve engine efficiency, and be compatible with heavy fuels. As the engine is to be used in flight, the following constraints apply: 1) minimal or no increase in the frontal area. 2) minimal or no increase to the installed weight of the propulsion assembly. PHASE I: Define and determine innovative technologies that will result in improvements to the engine cooling with minimal frontal area/weight impact. Demonstrate the feasibility of the approach through a detailed design. Identify the impact to the engine installation in terms of weight and bulk. Estimate improvements to the engine which may be realized by incorporation of the technology, specifically increases in power output (brake mean effective pressure, BMEP), improvements in efficiency (brake specific fuel consumption, BSFC), or durability (time between overhaul, TBO). A demonstration of hardware or fabrication/test of key components is desired. PHASE II: Demonstrate and validate performance improvements based on the Phase I technology on representative engine. Fabricate and bench test (as appropriate) prototype hardware or modifications. Conduct baseline testing on an in-service UAV engine incorporating the new technology. Refine the design and develop a plan leading to production-ready hardware. PHASE III DUAL USE APPLICATIONS: Military Application: Advanced thermal management systems are applicable to the Air Force, Navy, and Army. An increase in thermal management of engines could lead to increase life of engine components, and, thus, possibly a large cost savings per engine. This could be directly applicable to heavy fuel engines currently under development, such as the USAF"s Predator-Rotax 914 engine and the US Army"s Shadow-200 using the UEL AR741. Commercial Application: Current commercial applications aim for an increase in engine power, and an increase in engine power leads to an increase in heat transfer to engine components. Advanced thermal management systems offer the ability to minimize heat transfer to engine components. Further, this topic will incorporate thermal systems without a large increase in engine weight or size, which can be made directly applicable to the commercial market.
