Frequent flyers might think that filling up an aircraft is like filling up a car — choose from regular, premium, supreme and perhaps diesel.
The reality is, there are different types of jet fuel each with different characteristics. One of the most common jet fuels is Jet A — with Jet A-1 used in colder climates due to its lower freezing point.
Various manufacturers are also creating alternative jet fuels that are better for the environment or make use of the fossil fuels that are in abundance — such as coal or natural gas.
“To minimize cost and simplify logistics, the US Department of Defense has largely transitioned to Jet A with military additives,” says Anna Oldani, database manager at the University of Illinois Champaign’s alternative jet fuels test database project, an ANSYS Academic Partner. “However, we still need to monitor property variability that can exist, even across conventional fuels.
“Fuel variations may not affect the engine’s performance, but it can affect other system components and emissions. Any fuel that has particulates or other impurities can create soot, nitrogen oxides or other pollutants that can either damage the engine or the environment.”
That is why Oldani and her team are using physical tests and ANSYS Chemkin-Pro to track different types of jet fuels within a single database. The tests, Chemkin-Pro simulations and database have turned enough heads in the aerospace and defense industry that the US Department of Transportation awarded Oldani with the Student of the Year Award.
Why the Aerospace and Defense Industry Needs a Jet Fuel Database
Before Oldani’s project, there wasn’t a standard database of jet fuels. Hard to believe since this database could help the aerospace and defense industry in a variety of ways.
The obvious example is that engineers can optimize an engine’s design to work with different types of jet fuel. Additionally, operators will be able to predict which fuels will work with legacy engines.
“Fuels need to be drop-in ready so engineers can minimize switching costs and compatibility issues,” explains Oldani. “For instance, the first few times pure alternative jet fuel was used in engines it tended to leak and cause other issues.
“Alternative fuels don’t have the aromatics that traditional fuels have. These aromatics are absorbed by O-rings, which swell to tighten up seals. No aromatics, no seals and the engines leak. So, that’s why current alternative jet fuels are mixed with traditional jet fuels.”
The database could also help those looking to get new fuels approved and drop-in-ready. ASTM International governs fuel approval’s lengthy, costly process.
“Instead of spending all the capital to produce 100,000 gallons of fuel for testing, engineers can produce a few milliliters and we can test it against fuels in the database as an initial screening,” says Oldani. “Once the engineers are convinced they have a fuel that is comparable, or outperforms the ASTM approved fuels in the database, they can then start the approval process.”
How a Jet Fuel Database Helps the Environment
The database will also help engineers come up with alternative jet fuels that make economic and environmental sense.
“There is some distrust in the market from previous fuels like ethanol. It took too long to realize the impact it had on commodity prices, food costs and a deluge of other things,” says Oldani.
“The jet fuel database,” she adds. “will help us understand things like land use and social economic impacts. This data will help us find the most sustainable fuels from an environmental, social and economic perspective.”
Down the road, Oldani is also looking to add emissions data to the database.
“That would be a long-term project as we will have to standardize how the data is collected. But most airline operators have signed onto a carbon reduction scheme,” says Oldani. “A Recent report showed that a 50/50 blend of traditional and alternative jet fuel can reduce carbon dioxide emissions by 50% to 70%. Tracking this data will make the case that alternative jet fuels are having a good impact overall on the environment.”
How to Collect and Simulate Properties of Different Types of Jet Fuel
Oldani’s team works with airports and the US Air Force Research Lab (AFRL) to gather information for the jet fuel database.
“One of my primary collaborators is Tim Edwards. He’s been a leader in the field at the AFRL for decades,” says Oldani. “His database includes his test data of thousands of fuels from various industry leaders.
“The challenge is that this data is typically labeled by a reference number instead of a specific fuel so it can be challenging to know which sample comes from which batch, brand or source.”
Additionally, the AFRL data isn’t easily accessible and Oldani had to go through an involved process before she could take a single CD’s worth of data with her. If you are a company testing your fuel, this isn’t exactly efficient.
“We also have data from a dozen domestic airports,” she adds, “but we need to connect with more and facilitate how they are testing the fuel. We also need to work with the airlines as the airports don’t have direct control of the fuel, it is coordinated between fuel suppliers and the airlines.”
To enable the database to provide a more complete understanding between fuel properties and performance, Oldani uses fuel testing experiments and ANSYS Chemkin-Pro simulations.
“For the majority of our simulations, we use Chemkin-Pro to model the shock tube and rapid compression machine (RCM),” she says. “The RCM compresses the fuel until it ignites — similar to a single stroke of an internal combustion engine. We can simulate this in Chemkin-Pro.
“The simulations allow us to look deeper into the jet fuel conditions and properties that might be important. If a fuel has a unique ignition, we can use Chemkin-Pro to see what species create that condition. This can speed up fuel approvals because we will know that other fuels with those species could perform similarly.”
Or, learn more about the ANSYS Academic Program and Oldani’s student of the year award from the Department of Transportation.