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.

http://users.ntua.gr/rogdemma/MILLIMETER-SCALE,%20MEMS%20GAS%20TURBINE%20ENGINES.pdf

Millimeter-Scale, MEMS Gas Turbine Engines

Fabrication of alloy and ceramic microstructures by LIGA-MA-SPS process

: This report reviews Japan's research and development activities and strategies in the field of microsystems and microelectromechanical systems (MEMS). Topics covered include the future outlook of national initiatives, interactions between industry and universities, technology and manufacturing infrastructure, and emerging applications research. The panel's findings include the following: non-silicon microsystem technologies, together with parallel assembly technologies for low-cost mass manufacturing, merit increased attention. Incorporating non-silicon technologies into the MEMS Exchange should be considered, in order to identify, support, and standardize U.S. capabilities. Opportunities should be identified for exploiting early applications of synthetic nanostructures in microsystems. Metrology, process control, and device standardization should be pursued, in collaboration with Asia and Europe. Additional findings are outlined in the panel's executive summary.

/pdf/microsystems-research-in-japan-2t642pmar5.pdf

Microsystems Research in Japan

In the last decades, the enormous growth in portable electronics applications has stimulated research in lightweight and reliable power sources. In this technological niche, the idea of developing miniaturized turbomachinery to serve as portable power sources is attractive, especially in view of the much higher power density of a small turbogas generator in comparison with conventional chemical batteries. The potential social impact of an eventual commercialization of such “nano-devices” is enormous, but the technological and phenomenological complexity of the design and manufacturing of ultra-small machines (with a rotor diameter of the order of 1 cm) poses difficult problems, because some of the well-established design procedures for large and medium scale machines do not seem to be applicable as such at these extremely reduced scales. In this work the design and performance of a miniaturized gas turbine with a tip diameter of about 10 mm is examined from a thermo-fluiddynamic point of view. An extensive series of CFD simulations allows for the quantification of the losses at the resulting low Reynolds numbers (∼4600 in the stator and ∼1500 in the rotor) on the single-curvature geometry imposed by manufacturing constraints. The geometry of the blades is “optimized” on the basis of an entropy generation rate analysis, and the capabilities and limitations of conventional design strategies are assessed.Copyright © 2007 by ASME

Design and Performance Prediction of a Ultra-Micro Gas Turbine for Portable Power Generation

Silicon bulk micromachining

This paper describes a novel process, "Silicon Carbide Micro-reaction-sintering", to fabricate high-aspect-ratio silicon carbide microstructures. This process consists of micromachining of silicon molds, filling of material powders ( a-silicon carbide, graphite, silicon and phenol resin) into the molds, bonding of the molds with adhesive and reaction-sintering by hot isostatic pressing (HIP). Using our process, we have successfully fabricated silicon carbide microrotors of 5 and 10 mm diameters for micromachined gas turbines. We observed the cross section of the microrotors with a scanning electron microscope (SEM). The SEM observation demonstrated that the material powder was densely reaction-sintered by HIP. We also investigated the compositions of the microrotors by X-ray diffraction (XRD) analysis. The XRD analyses proved that graphite in the material powder reacted with melted silicon derived from the mold, and consequently /spl beta/-silicon carbide was produced around the /spl alpha/-silicon carbide originally included in the material powder.

Silicon carbide micro-reaction-sintering using a multilayer silicon mold

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Silicon carbide micro-reaction-sintering using a multilayer silicon mold