TECHNICAL ABSTRACT (LIMIT 200 WORDS) The operation of the low-pressure turbine at cruise conditions produces a Reynolds number significantly below takeoff conditions leading to laminar separation over the blades; consequently, the efficiency of the LP turbine at cruise is significantly below that at takeoff for both military and commercial engines. In the Phase I SBIR Techsburg demonstrated the capability of an innovative flow control technique designed to improve the LP turbine performance leading to a reduction in costs. Flow control was achieved with ejector pumps machined into the blade surface to provide a simple and efficient way of producing blowing and suction. High-pressure supply air from the compressor is injected into the flow as a high momentum jet providing a boundary layer that is resistant to separation, while low momentum fluid in the boundary layer is removed with suction upstream and combined with the supply air to enhance the jet. CFD and experimental data predicted a 72% increase in loss coefficient for a single blade row. Techsburg is proposing a comprehensive Phase II project to perform an in-depth computational optimization, detailed low-speed testing and high-speed cascade testing. The computational effort will focus on optimizing the flow control variables and blade shape for an LP turbine blade to eliminate separation and design a more highly loaded blade. The low-speed testing will validate the CFD work on the most promising blade candidates and subsonic cascade tests at engine Mach conditions will be performed to verify the results in a more realistic test environment.
POTENTIAL COMMERCIAL APPLICATIONS The proposed flow control system has significant potential for both military and commercial applications. In addition to its originally intended application as a technique for increasing efficiency by eliminating separation, ejector pump flow control in the low-pressure turbine may have other potential uses including enabling the design of more highly loaded blades leading to reduced part count and fewer stages. This flow control demonstrates a unique competitive advantage in several arenas, designed to meet the specific needs of the current commercial market. Low-pressure turbine research, particularly in the US is severely under funded, yet is critical to reducing operating costs in large commercial engines. The goal of this technology is twofold: increasing LP turbine efficiency at cruise and decreasing weight. A study done at NASA GRC showed that for large transport engines, improving the efficiency and reducing the weight of the LP turbine has the greatest impact on overall improvement in both direct operating costs (DOC+I) and specific fuel consumption (SFC) of the engine. The performance degradation from take-off to cruise of such an engine is on the order of 2%. By reducing separation to regain these two points, the decrease in SFC and operating costs would be very significant to the commercial gas turbine industry.
NAME AND ADDRESS OF PRINCIPAL INVESTIGATOR (Name, Organization Name, Mail Address, City/State/Zip) Sarah Stitzel Technology in Blacksburg, Inc. 2901 Prosperity Road Blacksburg , VA 24060 - 3636
NAME AND ADDRESS OF OFFEROR (Firm Name, Mail Address, City/State/Zip) Technology in Blacksburg, Inc. 2901 Prosperity Road Blacksburg , VA 24060 - 3636