The confluence of market demand for greatly improved compact power sources for portable electronics with the rapidly expanding capability of micromachining technology has made feasible the development of gas turbines in the millimeter-size range. With airfoil spans measured in 100’s of microns rather than meters, these “microengines” have about 1 millionth the air flow of large gas turbines and thus should produce about 1 millionth the power, 10-100 W. Based on semiconductor industry- derived processing of materials such as silicon and silicon carbide to submicron accuracy, such devices are known as micro-electro-mechanical systems (MEMS) | 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@ ABSTRACT The confluence of market demand for greatly improved compact power sources for portable electronics with the rapidly expanding capability of micromachining technology has made feasible the development of gas turbines in the millimeter-size range. With airfoil spans measured in 100 s of microns rather than meters these microengines have about 1 millionth the air flow of large gas turbines and thus should produce about 1 millionth the power 10-100 W. Based on semiconductor industry-derived processing of materials such as silicon and silicon carbide to submicron accuracy such devices are known as micro-electro-mechanical systems MEMS . Current millimeter-scale designs use centrifugal turbomachinery with pressure ratios in the range of 2 1 to 4 1 and turbine inlet temperatures of 1200-1600 K. The projected performance of these engines are on a par with gas turbines of the 1940 s. The thermodynamics of MEMS gas turbines are the same as those for large engines but the mechanics differ due to scaling considerations and manufacturing constraints. The principal challenge is to arrive at a design which meets the thermodynamic and component functional requirements while staying within the realm of realizable micromachining technology. This paper reviews the state-of-the-art of millimeter-size gas turbine engines including system design and integration manufacturing materials component design accessories applications and economics. It discusses the underlying technical issues reviews current design approaches and discusses future development and applications. INTRODUCTION For most of the 60-year-plus history of the gas turbine economic forces have directed the industry toward ever larger engines .
