Argonne-developed evaluation tools may lead to more efficient gas turbine generators

Sophisticated nondestructive, non-contact, sensing technologies developed at Argonne are playing a critical role in assuring the reliable operation of the nation’s fastest growing electric power supply producer — natural-gas-fired turbine generators. Gas-fired turbines coupled to electric generators are expected to satisfy more than 80 percent of new electric power demand in the United States in the next few decades, according to the U.S. Department of Energy (DOE).

Argonne researchers have developed technologies to enable the reliable use of high-temperature ceramic materials that improve turbine efficiency, lower exhaust emissions and enhance turbine lifetimes.

Reaching peak turbine efficiency — 75 percent from the current 45-55 percent — with low emissions requires tough ceramic components that allow higher gas-firing temperatures. Reliability is a key concern because unscheduled shutdowns are costly.

Argonne has assembled an arsenal of nondestructive evaluation (NDE) techniques to detect flaws that are frequently hidden beneath the ceramic surface. The NDE methods include thermal imaging, acoustic resonance, air-coupled ultrasound and laser back-scatter methods.

Ceramic component makers are taking advantage of these techniques to evaluate reliability in each processing stage because detecting faults early saves both time and money.

Ceramic liners are being made for gas combustion chambers, and Argonne is developing methods to test these components. The liners are laminated cloth seamed together into belts that are 0.12-inch thick, 8- to 12-inches wide and up to 30-inches-in-diameter. NDE techniques can detect faults or flaws in the layers or seams that can change mechanical and thermal properties before the liners are used in turbines.

ARGONNE’S GAS TURBINE NDE TOOLBOX
By combining off-the-shelf infrared cameras, initially developed for spy satellite technology, with Argonne-written software, Argonne engineers created a thermal-imaging NDE technique for automated data collection. Data acquisition and analysis have been reduced from 14 hours to less than 30 minutes with this patent-pending advance, and routine parts surveillance is now more economically feasible.

"It is our philosophy to use at least two NDE techniques to ensure confidence in the NDE data," said Bill Ellingson, senior engineer. Researchers corroborate the thermal-imaging data with air-coupled ultrasound for high reliability. Similar to the conventional ultrasound devices found in doctors’ offices that use a coupling gel, the new technology requires no coupling gel or water that might ruin the part being tested. Argonne researchers improved the software used in support of this technique.

NDE TECHNIQUES FOR ROTATING COMPONENTS
Argonne researchers are also developing NDE techniques for rotating components based on detection of resonant sound. Ceramists regularly use the "tap" test — a high pitch reveals a good component, a low pitch a bad one. Argonne’s NDE method replaces the human ear with a sensitive laser doppler velocimeter detector and sophisticated software to "hear" every blade’s resonance. Argonne engineers successfully demonstrated this method by showing the National Aeronautics and Space Administration (NASA) how tests of high-rotational-speed pumps for NASA’s reuseable launch vehicle had changed the materials.

NDE techniques for thin thermal barrier coatings, which allow metals to operate at higher temperatures, are also being investigated. Argonne researchers are developing a laser-scattering analysis method to detect changes that could show when the coating is in danger of separating from the metal.

Researchers are also developing methods to survey components with minimal engine disassembly and transferring them to industry. In these studies Argonne is working with such turbine engine manufacturers as Pratt & Whitney, Rolls Royce-Allison, Siemens-Westinghouse, GE Power Systems, Solar Turbines division of Caterpillar and Honeywell Engines and Systems.

Funding for this research is provided by the U.S. DOE’s Offices of Fossil Energy and Energy Efficiency and Renewable Energy.

For more information please contact Evelyn Brown

Next: ARM CARTs reduce climate change uncertainty