Shape memory alloy adaptive control of gas turbine engine compressor blade tip clearance

Lawrence McDonald Schetky; Bruce M. Steinetz

doi:10.1117/12.310649

16 June 1998 Shape memory alloy adaptive control of gas turbine engine compressor blade tip clearance

Lawrence McDonald Schetky, Bruce M. Steinetz

Proceedings Volume 3326, Smart Structures and Materials 1998: Industrial and Commercial Applications of Smart Structures Technologies; (1998) https://doi.org/10.1117/12.310649
Event: 5th Annual International Symposium on Smart Structures and Materials, 1998, San Diego, CA, United States

Abstract

The ambient air ingested through the inlet of a gas turbine is first compressed by an axial compressor followed by further compression in a centrifugal compressor and then fed into the combustion chamber where ignition and expansion take place to produce the engine thrust. The axial compressor typically has five or more stages which consist of revolving blades and stators and the overall performance of the turbine is strongly affected by the compressor efficiency. When the turbine is turned on, to accommodate the rapid initial increase in the compressor blade length due to centrifugal force, the cold turbine has a built in clearance between the turbine blade tip and the casing. As the turbine reached its operating temperature there is a further increase in the blade length due to thermal expansion and, at the same time, the diameter of the casing increases. The net result is that when these various components have reached their equilibrium temperatures, the initial cold build clearance is reduced, but there remains a residual clearance. The magnitude of this clearance has a direct effect on the compressor efficiency and can be stated as: Δη/Δ CLR equals 0.5 where η is efficiency and CLR is the tip clearance. The concept of adaptive tip clearance control is based on the ability of a shape memory alloy ring to shrink to a predetermined diameter when heated to the temperature of a particular stage, and thus reducing the tip clearance. The ring is fabricated from a CuAlNi shape memory alloy and is mounted in the casing so as to be coaxial with the rotating blades of the particular stage. When cold, the ring dimensions are such as to provide the required cold build clearance, but when at operating temperature the reduced diameter creates a very small tip clearance. The clearance provided by this concept is much smaller than the clearance normally obtained for a turbine of the size being studied.

Citation Download Citation

Lawrence McDonald Schetky and Bruce M. Steinetz "Shape memory alloy adaptive control of gas turbine engine compressor blade tip clearance", Proc. SPIE 3326, Smart Structures and Materials 1998: Industrial and Commercial Applications of Smart Structures Technologies, (16 June 1998); https://doi.org/10.1117/12.310649

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