Memorandum of agreement for testing facility signed

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On Sept. 15, a collaborative rela¬tionship between Arnold Engineer¬ing Development Center (AEDC) and the University of Tennessee Space Institute (UTSI) reached a major milestone with the signing of a memorandum of agreement between the two organizations for the ownership and maintenance of UTSI's Propulsion Research Facil¬ity and associated assets.

Jim Goodman, UTSI's technical research department director, has been the school's lead in providing support to operate and maintain the Propulsion Research Facility, which includes other test sections in addition to the J85 test stand. AEDC and UTSI also are collaborating on other projects, including renovating flow benches for Arnold's Precision Measurement Equipment Laboratory.

"Our collaboration with AEDC on this research facility benefits UTSI in several ways," Goodman explained. "UTSI can use it to provide graduate research education by enabling master's and doctor¬ate degree candidates the opportunity to work in these different sections of the facility and also provides us the opportunity to reach out to customers from all areas, industry and the federal agencies.

This facility came into existence as a result of a joint vision shared by the Air Force, ATA and UTSI.

"This memorandum of agreement between the university and AEDC provides a formal foundation for these three entities to carry forward with this important work."

Captain McNiel said everyone will benefit from this recently formalized relationship, but one thing that makes the facility unique is that it fulfills an immediate need.

"The Propulsion Research Facility is providing equipment, both hardware and techniques that are being used now - this facility is in high demand and it's very critical to testing that's currently underway - it's a very important asset for AEDC and for the Air Force," he said.

In addition to other ongoing projects, UTSI and AEDC recently partnered to provide valuable, new cutting-edge tools to be used in testing developmental en¬gines like the F119, the power plant for the F-22A Raptor.

The most recent project involved us¬ing a J85 afterburning turbine engine as a test bed to evaluate and validate new test techniques and technologies for near-term use in ground testing on the engines powering the F-22A Raptor and the F-35 Lightning II Joint Strike Fighter at Arnold. The J85 is the power plant for the T-38 Talon, an American supersonic jet trainer used by the U.S. Air Force and a host of other countries.

Last month, a team from AEDC used the J85 engine to validate a non-intrusive measurement technique called hydroxyl tagging velocimetry, according to Dr. Joe Wehrmeyer, a senior engineer with ATA's Technology and Analysis Branch. He said non-intrusive measurements of velocity are needed in supersonic flow where probes easily produce flow dis¬turbances.

"Non-intrusive gas phase velocity measurements are normally made with laser scattering from particles that natu¬rally exist in the flow or are added to the flow," he explained. "Hydroxyl tag¬ging velocimetry measures the engine's exhaust gas velocity instantaneously by using a pulsed laser to create a line of specialized molecules (OH) that move along with the exhaust gas.

Along the ultraviolet laser path a process called photodissociation produces the OH through light absorption by water vapor in the exhaust and subsequent breaking of the H2O into H and OH molecules. These then fluoresce, giving off light to show their movement downstream with the exhaust gas."

Dr. Wehrmeyer explained why accu¬rate velocity data is so important.
"Instantaneous, spatially-resolved velocity data can aid in the diagnosis of engine performance issues," he continued. "Such data could help us better understand screech and rumble, acoustic instability problems, in augmented engines if the data is obtained at a suf¬ficiently high acquisition rate - at least twice the screech or rumble frequency under investigation.

Exhaust velocity data, when coupled with exhaust density data, could also be used to indirectly measure engine thrust without the use of load cells. This is termed noncontact thrust measurement.

In late 2007, deconstruc¬tion began on an old coal-fired flow facility near UTSI's main campus to make way for a new complex known as the Propul¬sion Research Facility. This new facility is the site of the J85 test stand where a team from ATA and their counterpartsfrom UTSI have been using the engine to conduct performance tests on sensors, probes and non-intrusive diagnostic technologies for vali¬dation and eventual application in ground test cells at AEDC.

Don Gardner, an ATA Inte¬grated Test and Evaluation De¬partment engineer on the project, said the team conducting the recent tests chose to use a J85 engine for several reasons.

"We had a need for an af¬terburning engine because our diagnostics equipment needs to operate at higher temperatures to properly simulate conditions an engine experiences in flight," Gardner explained.

Greg Beitel, an engineer with ATA's Instrumentation and Diag¬nostics branch, said cost consid¬erations and issues of efficiency also come into play when consid¬ering the test bed.

"We don't want to do this work on a big engine in many cases because of the economics of maintaining that engine and plus you don't necessarily need that large a flow field to demon¬strate some sensor for measure¬ment techniques," he said. "Since the J85 is still in service, there are plenty of them in the Air Force inventory and we can rely on organizations such as Edwards AFB Propulsion Flight to rebuild and maintain the engine for us."

The collaboration between AEDC and UTSI using the J85 engine paid off recently when former Secretary of the Air Force Michael Wynne visited AEDC Nov. 27, 2007.

He was on hand to view another milestone event, the first ground testing of the General Electric F101 engine using a 50-50 mix of Fischer- Tropsch and JP-8 jet fuels.

"Right now, the J85 is used to prove instrumentation and diagnostics, both hardware and test techniques," explained Capt. Chuck McNiel, AEDC's Air Force aeropropulsion test tech¬nology program lead with the 649th Test Systems Squadron. "We basically use the engine as a plant, or our environment creator, like over here in J-1 they use the plant to provide their processed air and then the system under test is the engine. With the Propulsion Research Facility, the system under test is instrumentation."