Besides the octane rating and price, most drivers probably don’t think too much about the fuel they put in their cars. And, with modern engines and normal driving conditions, that’s probably OK for the mass majority.
But, what about a supersonic F-35 Lightning, a fully loaded-down C-17 Globemaster III flying out of Afghanistan or the first, yet-to-be-invented, hypersonic marvel to routinely soar at five times the speed of sound?
“There is a lot going on in the world where we want to get to far places really fast, and fuel is critical,” said Miguel Maldonado, Air Force Research Laboratory Fuels and Energy branch chief and electrical engineer. “People don’t realize that fuel is not just your energy source. All machines are not 100 percent efficient – they’re not even close to that. So, a lot of the energy being generated is heat. All that heat is being absorbed through the fuel.”
Back when airplanes were mostly made of metal, the airframe and wings served as heat sinks, according to Maldonado. But, with the focus on high-tech composites to manufacture cutting-edge airframes, that particular advantage is gone.
“Fighters now are kind of an [insulated] bottle,” Maldonado said. “You’re creating a lot more energy and heat inside and you have nowhere to dump it; the only thing you have left is the fuel. That’s what absorbs it and tries to take it away to cool down all the other components. So, it’s your heat sink, your energy source, and, in some cases, also the lubricity for bearings and other aspects.”
Because of the multipurpose function of fuel, the Fuels and Energy branch conducts studies across the full spectrum of Department of Defense fuels, while also working closely with commercial aviation. This includes determining the composition of fuels, combustion properties, emissions, and biological identification and mitigation. Some organisms live in fuel, where they then can degrade the fuel, clog the fuel system or otherwise wreak havoc on multimillion dollar aircraft.
Fuels and Energy’s focus on fuel is so mission-oriented the branch is broken down into three high impact technology programs: fuel and combustion science (HIT 1), endothermic fuels (HIT 2) and nanofuels and fuel biodeterioration (HIT 3). All are designed to define what makes up fuel and how those materials can be used to make fuel even better or find a solution to a problem.
“We take fuel, which is comprised of up to thousands of different components and we try to identify and quantify, or count, how many of each component is in the fuel,” said Milissa Griesenbrock, AFRL Fuels and Energy branch co-lead for HIT 1 and research chemist. “After that, we attempt to link the different components in the fuel to different properties of that specific fuel.”
Although indistinguishable to human senses, often on a parts-per-million scale, these components can give clues to scientists trying to figure out how to fix a problem.
“Our end goal is to support the warfighter,” Griesenbrock said. “Any sort of field issues that the warfighter is having, if fuel is [not functioning properly], we investigate and solve that problem.”
For those at the Air Force Petroleum Office fuel laboratory, also located at Wright-Patterson, Fuels and Energy’s assistance is crucial.
“Fuels and Energy’s technical expertise and analytical capabilities are critical to the development and revision of AFPET managed aviation turbine fuel specifications,” said Gordon J. Walker, AFPET aerospace chemist.
AFPET is the service control point for all Defense Logistics Agency fuel – that is, all of the aviation fuel used across the Air Force worldwide is quality checked at AFPET.
“[They’ve] provided unequaled capabilities in support of aviation fuel quality investigations to allow AFPET to develop course of actions to mitigate operational impacts worldwide,” Walker said.
One of the issues Fuels and Energy was able to fix was a problem with the fuel system ice inhibitor system on an aircraft. The inner coating on its fuel tanks was peeling off, degrading the fuel and risking a clog in the fuel system, which could have had catastrophic consequences if it occurred in flight.
The cause of the peeling was diagnosed – the fuel additive used to prevent icing in the fuel system was making the coating come off. The Fuels and Energy branch then had to figure out how to stop the peeling while also ensuring the fuel system wouldn’t freeze.
“There were multiple efforts looking at how we could mitigate the problem,” said Zachary West, a senior research engineer contractor from the University of Dayton Research Institute who works in the Fuels and Energy branch. “One of them was coming up with a replacement additive; one was looking at completely removing the additive; and another effort was looking at reducing the concentration of the additive. So we looked down all three of those avenues; we came up with a viable alternative FSII option; and then we also came up with guidance on what an acceptable lower dose level was [for the inhibitor]; and ultimately, that’s what went through in the specification.”
As it turned out, only half the amount of inhibitor was needed to prevent icing in the system while also reducing the amount of peeling, according to Maldonado. The fix saved the Air Force roughly $2 million a year, both from reduced inhibitor use and maintenance no longer needed to deal with the peeling. But, that’s not all the branch discovered.
“Interestingly, we found that FSII not only provides ice inhibition but also helps with the microbial growth, having some impact in keeping that away,” Maldonado said.
Information like that is what the Fuels and Energy branch attempts to garner no matter the project. It’s not just about fixing a problem; it’s also about finding the next technologic breakthrough.
“While working on a project, you always find interesting things that you want to delve into a little bit more,” Griesenbrock said. “So, we take some extra time and we do that. Luckily, we’re part of AFRL, which encourages and allows us to do that. If you look at any of the [companies that do a lot of research], they devote 5 to 10 percent of their time researching [interesting things]. That is how you get innovative, sometimes seemingly insane ideas that lead to transformational technologies for the warfighter.”
To foster that innovation, the Fuels and Energy branch partners with more than 30 contractors from UDRI and United Technology Corp. to augment their military and civilian staff of 15.
“The government realizes that they can’t do this on their own,” West said. “You want to take a technology and then develop it to fruition and actually field it. [At UDRI], we have experience in both. So, if the Air Force wishes to go in-depth into the science, we can do that. If they wish to go more practical, we can do that as well to strike that balance.”
The Fuels and Energy branch strikes a balance with its workforce as well. Due to the unique nature of fuels and how they are used, the branch employs a wide range of skillsets, including chemists, physicists and biologists, as well as electrical, chemical and mechanical engineers.
“As in everything, diversity just makes it more fun,” Maldonado said. “You’re looking at problems from different angles and different backgrounds and then you have to try to bring it together. Sometimes, you have to fight it out, ‘No, this is the way because of physics or because of chemistry or because of mechanical.’ But, I believe it leaves a better solution because you’re having a broader source of where you’re looking at things and being able to provide that.”
It’s a different environment than most labs that focus on one type of engineering or research, according to Maldonado, but it’s one that leaves some staff members a feeling of accomplishment.
“It’s just a great feeling because you help [the customer],” Griesenbrock said. “I’ve always been a people person. My first degree I completed was in social work because I wanted to help people. So, this is just an extension of that but now I get to use chemistry to help people.”