Jewish World Review
http://www.jewishworldreview.com | (UPI) -- The fuel of high-flying spy planes of the future could be kept from freezing by a surprisingly simple additive -- urea, the chief ingredient of urine.
"It's an extremely simple way of improving the low temperature properties of jet fuel to prevent freezing," researcher Steven Zabarnick, a chemist at the University of Dayton Research Institute in Ohio, told United Press International.
"Many flights are going over the North Pole in long-duration flights to Asia, upwards of 14 hours, and over that long time, fuel can be subjected to very low temperatures, approaching freezing," Zabarnick said. "If economically viable, this can be used to produce fuel for both military and commercial aviation."
Asked whether the urea treatment could allow spy planes to fly longer missions, Zabarnick replied, "I don't think I can comment on that."
Aircraft that fly at high altitudes for long stretches of time, such as the U.S. Air Force's U-2, can experience temperatures as low as -135 degrees F and commonly get as cold as -75 to -95 degrees F, Zabarnick said. Fuel can gum up and freeze at the relatively balmy range of -40 to -65 degrees F, making it unable to enter engines and risking the prospect of catastrophic fuel system failure.
Air Force high-altitude aircraft use expensive jet propellant thermally stable, or JPTS, fuel that resists freezing. However, it costs three times as much as conventional jet fuel. As reported in an upcoming issue of the journal Energy & Fuels, the researchers found refining regular jet fuel with urea improved its freezing point by 12 degrees C, or about 20 degrees F.
"I was shocked at how dramatic the change was. We expected to possibly see a 2 to 3 degree C change," Zabarnick said.
Jet fuel freezes because one of its components, called normal paraffins -- which are leftovers from the distillation processes that create the fuel out of crude oil -- tends to solidify at low temperatures.
In the 1940s, scientists found urea clung to and reacted with normal paraffins, but no one had ever tried adding the substance to jet fuel during the refining process. First discovered in human urine in 1773, urea can be synthesized to help make barbituates -- also known as sleeping pills -- fertilizer and industrial coatings.
The researchers took small vials of urea powder, added it to jet fuel and stirred it up. The urea and normal paraffins reacted at room temperature and formed crystals that fell to the bottom of the mixture. "Our initial run, the crystallization was off the scale," Zabarnick said.
They also found adding 1 percent methanol greatly helped the reaction by increasing urea's solubility, making it better able to react with the normal paraffins, Zabarnick said. The crystals then were removed, and when the refined fuel was cooled with liquid nitrogen or thermoelectric coolers, the scientists noted improvements in freezing properties.
Zabarnick said further research is needed to see if the refining process is financially feasible. "It may never happen," he said. The hope is that refining jet fuel with commercially available urea will prove cheaper than making current low-temperature fuels and the research team has begun a program, funded by the Federal Aviation Administration, to improve jet fuel for commercial flights.
Mechanical engineer and aviation fuel expert Kurt Strauss in Portland, Maine, said one basic problem with such a refining process is removing the normal paraffins afterwards. "If you're treating millions of gallons of jet fuel, you'll end up with an enormous amount of normal paraffins, and I don't know what you'd do with it," he said.
Appreciate this type of reporting? Why not sign-up for the daily JWR update. It's free. Just click here.
Comment by clicking here.