Development of a HTSMA-Actuated Surge Control Rod for High-Temperature Turbomachinery Applications

Abstract

In recent years, a demand for compact, lightweight, solid-state actuation systems has emerged, driven in part by the needs of the aeronautics industry. However, most actuation systems used in turbomachinery require not only elevated temperature but high-force capability. As a result, shape memory alloy (SMA) based systems have worked their way to the forefront of a short list of viable options to meet such a technological challenge. Most of the effort centered on shape memory systems to date has involved binary NiTi alloys but the working temperatures required in many aeronautics applications dictate significantly higher transformation temperatures than the binary systems can provide. Hence, a high temperature shape memory alloy (HTSMA) based on NiTiPdPt, having a transformation temperature near 300 o C, was developed. Various thermo-mechanical processing schemes were utilized to further improve the dimensional stability of the alloy and it was later extruded/drawn into wire form to be more compatible with envisioned applications. Mechanical testing on the finished wire form showed reasonable work output capability with excellent dimensional stability. Subsequently, the wire form of the alloy was incorporated into a benchtop system, which was shown to provide the necessary stroke requirements of ~0.125 inches for the targeted surge-control application. Cycle times for the actuator were limited to ~4 seconds due to control and cooling constraints but this cycle time was determined to be adequate for the surge control application targeted as the primary requirement was initial actuation of a surge control rod, which could be completed in approximately one second.

Active Stiffness Method for High Cycle Fatigue Mitigation using Topical Thin Foil Shape Memory Alloy

“…It is expected that optimally designed components will be of low weight and low power consumption (using a method other than joule heating), and thus attractive for future use in flight applications. Alternatively, SMA formulations exist with high temperature transformation temperatures [14,15,16]; utilization of the engine operating temperature may be a viable source of actuation.…”

“…The composition of the NiTi alloy and the thermo-mechanical processing influence the damping characteristics of the material [11]. In addition, the transformation temperature can be tailored through formulation, especially for high temperature applications [14,15]; Ni 19.5 Ti 50.5 Pd 25 Pt 5 has a transformation temperature near 300°C, which is conducive for turbomachinery applications [16].…”

“…When an SMA is in the austenite phase and is slightly above a prescribed temperature, the addition of an external stress can produce the martensite phase. The amount of damping observed depends upon the steady state stress level, alternating stress level, frequency, and temperature [16].…”

NASA and Superalloys: A Customer, a Participant, and a Referee

“…A compressor's aerodynamics can improve efficiency but may be limited by the onset of compressor stall conditions. A strategy of advanced sensors that can detect the onset of incipient stall, which would then trigger small changes to the flow geometry, allows for a compressor that has both improved efficiency plus tolerance against stall conditions [8]. Many of these concepts have been envisioned in the past, but could not be achieved because they relied upon electric, hydraulic or pneumatic actuators that brought excessive weight penalties.…”

Damping of high-temperature shape memory alloys

“…al. 9 described a NiTiPdPt alloy with a transformation temperature near 300 o C for high-temperature turbomachinery applications. The NASA GRC research has primarily supported the application of HTSMAs as actuators; the damping properties have not been investigated prior to this study.…”