By Eric Lindeman
Supporting the bio-fuels certification effort for the F110 jet engine, the Air Force has begun performance testing using a 50-50 blend of JP-8 jet fuel and a biofuel made from camelina oil.
Testing of the engine, which powers the F-16 aircraft, is being conducted at Arnold Engineering Development Center (AEDC) at Arnold AFB, Tenn. It will simulate the overall engine conditions experienced in the full range of flight conditions, ignition light-off, throttle transients, augmenter lights, sequencing and screech and rumble monitoring, according to First Lt. Antonio Brunson, 717th Test Squadron program manager for the first phase of the test.
Camelina has a number of important advantages over other bio-feedstocks. It is the most readily available today, with tens of thousands of acres currently under management and that much more planned for the near term. And, most importantly, testing so far indicates that camelina oil-based fuel can be used in unmodified jet and diesel engines.
The camelina plant, which requires less water, fertilizers and herbicides than other bio-feedstocks, is grown in rotation with wheat and does not displace food crops. Camelina seeds have high natural oil content and, because it is only used as a source of renewable fuel, it is relatively inexpensive. Many biofuel producers believe camelina oil can be competitive with crude oil at today’s prices and even more so if crude oil prices rise.
In April, the Navy successfully conducted the first test flight at supersonic speeds of an F/A-18 Super Hornet multi-role fighter jet powered by a 50-50 blend of JP-5 jet fuel and a camelina oil-based biofuel. That test at Naval Air Station Patuxent River, Md., showcased the Navy’s “Green Hornet” for Earth Day, April 22.
“The testing recently initiated at AEDC will be the first dedicated, uninstalled engine tests conducted by the Air Force [on Hydro-processed Renewable Jet (HRJ) blended fuel],” said Jeff Braun, director of the Air Force’s Alternative Fuels Certification Office.
“These will also be the first engine tests conducted by the Air Force [on HRJ blended fuel] in a facility that can simulate altitude effects on the aircraft. The data produced will be very, very valuable in this program. In fact, we plan on using that data to justify and support upcoming flight tests of the F-22, the C-17 and then possibly even the F- 15.”
Military jet engines operate with afterburners to enhance thrust, the Air Force explained in a June 28 announcement of the testing. But the afterburners can create significant unsteady pressure oscillations, referred to as screech and rumble, which can damage the afterburner structure.
Brunson, who was also project manager on earlier 50-50 synthetic fuel and JP-8 blend testing on military jet engines at AEDC, is enthusiastic about the program. “In my opinion,” he said, “this is going to be the future of the Air Force–alternative fuels–so being able to have a role in that early on, is important to me.”
He added, “AEDC is producing the baseline data that enables us to go forward and prove that these fuels are viable fleet-wide for the Air Force. We purposefully picked the F110 and F100, because they are what we consider the most challenging and the most fleet- representative engines across the Air Force.
“Our strategy is to have the engines tested and certified using AEDC’s facilities, and then use that data to support any other actual flight testing that we conduct within the Air Force.”
Braun lauded the work at AEDC, saying, “I can’t stress enough the data that we get from using Arnold’s engine test cells just goes miles as far as providing confidence to the aircraft community. That’s why we work so hard at structuring these tests and maintaining our schedule. Any delays would have serious ripple effect through the entire fleet-wide certification effort.”
David Dickey, the lead systems engineer for propulsion in the Alternative Fuels Certification Office at Wright Patterson AFB, Ohio and the program manager for AEDC’s current synthetic fuels testing, concurred that the Air Force’s longer term plan relies on the type of testing being done at AEDC.
“The goal is to complete certification of the Air Force fleet for unrestricted use of the HRJ blend by the end of 2012,” he said.
“It is expected that the F-16, along with the rest of the Air Force fleet, will be certified on the basis of the verification and validation provided by all of the data generated from the HRJ certification analysis and test program.” Dickey said. “Once certified, all aircraft, including the F-16, will be able to use the HRJ blended fuel for unrestricted operations.”
The Air Force, the Defense Department’s largest energy consumer, spent about $9 billion on energy in 2008–84 percent for aviation fuels. To reduce that usage, it created a comprehensive energy program and policy, “Air Force Energy Plan 2010,” the objective of which is to “make energy a consideration in all that we do.”
The plan focuses on three goals: reduce demand across aviation, ground operations and installations; increase supply by developing renewable fuels for aviation, ground operations and installations. Those goals include meeting 25 percent of base energy needs with renewable energy sources by 2025 and obtaining 50 percent of aviation fuels from biofuel blends by 2016.