Millimeter Scale , Mems Gas Turbine Engines

The confluence of market demand for greatly improvedcompact power sources for portable electronics with the rapidlyexpanding capability of micromachining technology has madefeasible the development of gas turbines in the millimeter-sizerange. With airfoil spans measured in 100’s of microns ratherthan meters, these “microengines” have about 1 millionth theair flow of large gas turbines and thus should produce about 1millionth the power, 10-100 W. Based on semiconductor industry-derived processing of materials such as silicon and siliconcarbide to submicron accuracy, such devices are known asmicro-electro-mechanical systems (MEMS)....
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Millimeter Scale , Mems Gas Turbine Engines Proceedings of ASME Turbo Expo 2003 Power for Land, Sea, and Air June 16-19, 2003, Atlanta, Georgia, USA GT-2003-38866 MILLIMETER-SCALE, MEMS GAS TURBINE ENGINES Alan H. Epstein Gas Turbine Laboratory Massachusetts Institute of Technology Cambridge, MA 02139 USA epstein@mit.eduABSTRACT several of which are marketed commercially [1, 2]. Gas turbines The confluence of market demand for greatly improved below a few hundred kilowatts in size generally use centrifugalcompact power sources for portable electronics with the rapidly turbomachinery (often derivative of automotive turbochargerexpanding capability of micromachining technology has made technology in the smaller sizes), but are otherwise very similarfeasible the development of gas turbines in the millimeter-size to their larger brethren in that they are fabricated in much therange. With airfoil spans measured in 100’s of microns rather same way (cast, forged, machined, and assembled) from thethan meters, these “microengines” have about 1 millionth the same materials (steel, titanium, nickel superalloys). Recently,air flow of large gas turbines and thus should produce about 1 manufacturing technologies developed by the semiconductormillionth the power, 10-100 W. Based on semiconductor indus- industry have opened a new and very different design space fortry-derived processing of materials such as silicon and silicon gas turbine engines – one that enables gas turbines with diam-carbide to submicron accuracy, such devices are known as eters of millimeters rather than meters, with airfoil dimensionsmicro-electro-mechanical systems (MEMS). Current millime- in microns rather than millimeters. These shirt-button-sized gaster-scale designs use centrifugal turbomachinery with pressure turbine engines are the focus of this review.ratios in the range of 2:1 to 4:1 and turbine inlet temperatures of Interest in millimeter-scale gas turbines is fueled by both1200-1600 K. The projected performance of these engines are a technology push and a user pull. The technology push is theon a par with gas turbines of the 1940’s. The thermodynamics of development of micromachining capability based on semicon-MEMS gas turbines are the same as those for large engines but ductor manufacturing techniques. This enables the fabrication ofthe mechanics differ due to scaling considerations and manufac- complex small parts and assemblies – devices with dimensionsturing constraints. The principal challenge is to arrive at a design in the 1-10,000 µm size range with submicron precision. Suchwhich meets the thermodynamic and component functional parts are produced with photolithographically-defined featuresrequirements while staying within the realm of realizable micro- and many can be made simultaneously, offering the promise ofmachining technology. This paper reviews the state-of-the-art of low production cost in large-scale production. Such assembliesmillimeter-size gas turbine engines, including system design and are known in the US as micro-electrical-mechanical systemsintegration, manufacturing, materials, component design, acces- (MEMS) and have been the subject of thousands of publica-sories, applications, and economics. It discusses the underlying tions over the last two decades [3]. In Japan and Europe, devicestechnical issues, reviews current design approaches, and dis- of this type are known as “microsystems”, a term which maycusses future development and applications. encompass a wider variety of fabrication approaches. Early work in MEMS focused on sensors and simple actuators, and manyINTRODUCTION devices based on this technology ar ...