Arnold AFB supports DOD assured fuels initiative

ARNOLD AIR FORCE BASE, Tenn. (AFPN) -- The Arnold Engineering Development Center is taking a leading role in supporting the Department of Defense's assured fuels initiative, which aims to steer the military away from its reliance on foreign oil.

A team from the center took its technical expertise and specialized equipment on the road to assist the Air Force in fielding time-critical alternative fuel testing at Tinker Air Force Base, Okla.

"We had been asked to provide exhaust gas analysis for the TF33, the engine powering the B-52 Stratofortress," said Paul Jalbert, an Aerospace Testing Alliance emissions system engineer at AEDC who was among those assisting with the tests at Tinker.

"We were asked to quantify the exhaust gas emissions from that engine when it was burning baseline JP-8 fuel and when it was burning a 50 percent blend of synthetic Fischer-Tropsch fuel and JP-8. We were looking for the differences in those emissions from the same engine from two different fuels," Mr. Jalbert said.

ATA is the support contractor at AEDC, and is a joint venture between Jacobs Sverdrup, Computer Sciences Corp. and General Physics Corp.

The AEDC team's continuous sweep emission measurement system provided conclusive evidence that there were no significant differences in either atmospheric emissions or engine performance with the JP-8/Fischer-Tropsch blend fuel from the straight JP-8 fuel. The test results will help to support the Air Force's plans to test fly a B-52 powered in part by the blend of the synthetic fuel and JP-8 later this year.

The urgency behind the Air Force's motivation to test Fischer-Tropsch, which is derived from natural gas, was driven largely by the same concerns shared by industry and consumers with the nation's high dependence on foreign oil, according to Don Gardner, ATA's Technology and Analysis Branch lead on the project. A limited supply of available Fischer-Tropsch fuel also meant the team doing the work had to perform the measurements and data quality checks in near-real time to complete the test matrix.

In 2004, the team at AEDC had first demonstrated the continuous sweep emissions measurement system as a means to reduce the cost of emission measurements by reducing the amount of time required to obtain them.

This system includes a water-cooled probe rake assembly that sweeps back and forth across the engine nozzle exit in approximately two minutes. This allows the engineers to measure a full cross-section of the exhaust gas emissions from the engine in a relatively short period of time. The gases are drawn through probes and flow through heated lines to fast-response gas analyzers.

"The analyzers were located about 80 feet away from the engine," Mr. Jalbert said. "We pull in the exhaust gas samples as well as ambient air samples because we want to be able to separate what came out of the back of the engine from any pollution or contamination that may have entered the front of the engine. We try to quantify all of the exhaust gases that are either considered to be aircraft pollution or indications of aircraft engine performance.

The probe rake traverses continually behind the engine collecting exhaust gas samples. Those samples are processed by analyzers, which look for things like carbon dioxide and carbon monoxide.

"The data set is analyzed and processed by computer so that within a three-and-half-minute time period from the start of each rake traverse, we can provide our customers with a complete digital representation of what the exhaust plume looked like," Mr. Jalbert said.

The test was a collaborative effort between representatives from AEDC, the Air Force Research Laboratory at Wright-Patterson AFB, Ohio, and Tinker AFB, Okla.

(Courtesy of Air Force Materiel Command News Service)