The progress of
the flame after ignition in a post-impact mist of Jet-A fuel treated with
prior ultra-long
polymers (upper) and the Caltech polymer (lower) after the samples
have passed
through a fuel pump 50 times. The efficacy of prior polymers is lost,
and a large, hot
fireball ensues. The Caltech polymer retains its ability to mitigate
post-impact fire.
The color scale shows the progression of the flame with time.
Credit:
Caltech/JPL
(October 2, 2015) Before
embarking on a transcontinental journey, jet airplanes fill up with tens of
thousands of gallons of fuel. In the event of a crash, such large quantities of
fuel increase the severity of an explosion upon impact. Researchers at Caltech
and JPL have discovered a polymeric fuel additive that can reduce the intensity
of postimpact explosions that occur during accidents and terrorist acts.
Furthermore, preliminary results show that the additive can provide this
benefit without adversely affecting fuel performance.
The work is published in the October 2 issue of the journal
Science.
Jet engines compress air and combine it with a fine spray of
jet fuel. Ignition of the mixture of air and jet fuel by an electric spark
triggers a controlled explosion that thrusts the plane forward. Jet airplanes
are powered by thousands of these tiny explosions. However, the process that
distributes the spray of fuel for ignition—known as misting—also causes fuel to
rapidly disperse and easily catch fire in the event of an impact
The additive, created in the laboratory of Julia Kornfield
(BS '83), professor of chemical engineering, is a type of polymer—a long
molecule made up of many repeating subunits—capped at each end by units that
act like Velcro. The individual polymers spontaneously link into ultralong
chains called "megasupramolecules."
Megasupramolecules, Kornfield says, have an unprecedented
combination of properties that allows them to control fuel misting, improve the
flow of fuel through pipelines, and reduce soot formation. Megasupramolecules
inhibit misting under crash conditions and permit misting during fuel injection
in the engine.