NDLI: Mechanical Design Features of a Small Gas Turbine for Power Generation in Unmanned Aerial Vehicles

Content Provider	The American Society of Mechanical Engineers (ASME) Digital Collection
Author	Caleb, S. Cunningham Ransom, David Wilkes, Jason Bishop, John White, Benjamin
Copyright Year	2015
Abstract	As part of the Intelligence Advanced Research Projects Activity (iARPA) Great Horned Owl (GHO) program, Southwest Research Institute® (SwRI®) developed and tested a small gas turbine for power generation in Unmanned Aerial Vehicles (UAV). This development program focused on advancing the state of the art in UAV power systems by meeting key metrics in weight, fuel efficiency, and noise generation. Design, assembly, and testing of the gas turbine were completed in-house at SwRI. Fundamental mechanical design features of the gas turbine include an integrated 7 kW motor-generator, minimal oil lubrication system, cantilevered compressor/turbine assembly, and can combustor with air-atomizing fuel nozzles. The compressor/turbine assembly is cantilevered directly off of the motor-generator shaft, which spins on hybrid ceramic bearings. Due to potential rotor natural frequencies in the design operating range, the rotor-dynamic design of this configuration was a special design challenge. The outboard rotor bearing is softly supported on O-rings to provide compliance and drive shaft natural frequencies below the operating range. The lube oil system is another interesting design feature of the GHO gas turbine. It is based on a minimal oil lubrication system previously used at SwRI. The minimal oil lubrication system relies on low oil flow rates and cooling air to pull droplets of oil through the bearing. The oil passes through the machine and is consumed during combustion. This system eliminates traditional oil recirculation hardware for simplicity and weight savings. The can combustor features a modular design and uses additive manufacturing techniques to facilitate easy and cost effective prototyping. All combustor components are manufactured from Inconel 718 using direct metal laser sintering (DMLS) with additional post-machining. These parts are particularly challenging for DMLS because of their thin walls and high aspect ratio. The custom air-atomizing fuel nozzles also highlight one of the exciting advantages of the DMLS process. Each nozzle would be difficult to machine using traditional techniques because of the tight internal flow passages; however, they are simple to construct using additive manufacturing. The GHO turbine developed by SwRI demonstrates interesting design features including a minimal oil lubrication system, a cantilever shaft with softly supported bearing, and combustor components built using additive manufacturing techniques. This design provides a platform for further development, testing, and demonstration of small gas turbine technology for UAV power generation.
Sponsorship	International Gas Turbine Institute
File Format	PDF
ISBN	9780791856796
DOI	10.1115/GT2015-43491
Volume Number	Volume 8: Microturbines, Turbochargers and Small Turbomachines; Steam Turbines
Conference Proceedings	ASME Turbo Expo 2015: Turbine Technical Conference and Exposition
Language	English
Publisher Date	2015-06-15
Publisher Place	Montreal, Quebec, Canada
Access Restriction	Subscribed
Subject Keyword	Bearings Metals Machining Motors Industrial lubrication systems Combustion Additive manufacturing Fuels Machinery Engines Thin wall structures Design Cantilevers Noise (sound) Design engineering Gas turbines Fuel efficiency Internal flow Lasers Power systems (machinery) Weight (mass) Energy generation Nozzles Unmanned aerial vehicles Hardware Manufacturing Turbines Testing Cooling Rotors Compressors Generators Ceramics Flow (dynamics) Sintering Drops Seals Combustion chambers
Content Type	Text
Resource Type	Article

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