ARTICLE 1 MAKALE Combustion, Lawrence Berkley National Laboratory and Calnetix. United technologies 5-yr program: United Technologies Corp. 5-yr program includes demonstrating an advanced microturbine engine derived /rom the 400-kw class recuperated Pratt&Whitney Canada ST5 gas turbine engine. Target delivery date lor the baseline engine, which is expected to have an electrical efficiency of 30%, is March 2002. The microturbine development program aims to increase that design efficiency to betler !han 40%. Projects engineers plan on raising firing temperatures while using uncooled ceramic hat section components, increasing power generation and conversion efficiencies and preserving low Nox capability with "affordable" small scale fuel-air mixers. Partners in the UTC program (besides P&W Canada) include DTE Energy, TurboGenset (based in the UK with experience in high performance generator technology), Hamilton Sundstrand (part of UTC), SatCon (headquarters in Cambridge, Mass), Kyocera, Solar Turbines, and Oak Ridge National Laboratory. General Electric 4-yr program: General Electric's program, as presently constituted, is designed to apply DOE funding over a 4- year period to build an operational system derived /rom a design concept lor a 175-350kw configuration. The approach includes use of an advanced material recuperator (integral or off-board), advanced seals lor both compressor and turbine sections, advanced materials lor nozzle and rotor, a direct drive high-speed alternator, and an advanced low emissions combustion system. The projeci team alsa will apply advanced turbomachinary design methodology lor both compressor and turbine plus state of the art power electronics and controls. Partners include several company divisions including Power Systems and lndustrial Systems, semiconductor developer Semikron, and Kyocera lndustrial Ceramics. Solar Turbines 3-yr program: Solar Turbines, at this juncture, has not announced any plans to build its own microturbine. Company is locusing instead on providing advanced materials and recuperators applicable to any of the microturbine generator candidates. One of the goals over a 3-year period is to update the properties of its 11primary surface recuperator" technology. Among objectives are increasing the turbine exhaust temperature capability to 732 /rom 649 ° C; alloy modification to improve mechanical strength, creep strength and oxidation resistance; and reducing the manufacturing costs lor producing microturbine recuperators. Achieving cost containment and reduction lor recuperates, Solar points aut, is very important since currentıy recuperators account tor one-third the cost of a microturbine system. Partners include Allegheny Ludlum (steel maker), Capstone Turbine, Elliott Power Systems, United Technology Research Center, and Oak Ridge National Laboratory. Materials and Technology: One important input lor ceramics suppliers was to identify a design envelope of anticipated operating conditions lor potential ceramic components in an advanced microturbine. Researchers are evaluating the effects of temperature, pressure, water vapor and gases on the environmental resistance and mechanical stability of candidate ceramics !hat may be used in microturbine designs. They are alsa investigating ways to improve or enhance the environmental stability of these ceramics, with high performance coating as one possibility. Much of the research on advanced materials and materials systems is being conducted or supervised by experts at Oak Ridge National Laboratory with Dave Stinton serving as projeci manager. ORNL programs: Oak Ridge National Laboratory is working on environmental stability of silicon nitride ceramics, higher temperature recuperator materials, and heat sinks. Ceramics projects include environmental testing (with Honeywell and Kyocera), mechanical properties (with the University of Dayton Research lnstitute), protective coatings, and reliability and life prediction (with NASA). Dave Stinton of the ORNL team points aut that both Honeywell Ceramics and Kyocera have been developing silicon nitride lor some time. "Both make good materials with properties an order of magnitude betler !han 10 years ago". Complex-shaped ceramic components (including turbine vanes) are being tested in actual engines, say projeci engineers, with promising results. But there are potential problem areas. üne concern, lor example, is !hat turbine flows at high pressure (around 10 atm) containing water vapor could damage silicon nitride components. "We are running tesis to fınd aut what temperature, pressure and water vapor levels that silicon nitride can handle,'' says Stinton. "in addition, we are developing and evaluating coatings to protect silicon nitride components lor use in high temperature microturbines." Recuperators and heat sinks: in the case of recuperators, DOE points aut, the materials requirements lor near-term machines may be categorized by maximum operating temperatures at 1200'F (type 347 stainless steel), 1500'F (lnconel), and over 1600'F (ceramics). These temperature limitations are imposed by existing materials properties such as strength and corrosion, oxidation, and creep resistance !hat affect recuperator failure. Metallic alloys are now usable within the two lower temperature ranges, while ceramics are needed lor the higher temperature environments. Current activities at ORNL include work on creep-resistant materials lor 600-750'C environment and oxidation resistant materials to operate in the 750-900'C. ECOGENERATION WORLD iL
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