Notre Dame Researchers Designing A Way To Prevent Cavitation
Damage In Jet-Fuel Pumps
For more than 250 years, researchers have known that under
certain conditions vapor bubbles can form in fluids moving swiftly
over a surface. These bubbles soon collapse with such great force
that they can poke holes in steel and damage objects such as ship
propellers, turbine blades, nozzles and pump impellers.
Scientists have conducted extensive research for decades to try
to understand this phenomenon -- called cavitation. But most
experiments to date have been related to open-water objects like
ship propellers.
Now a group led by Notre Dame professors Patrick Dunn and Flint
Thomas has published the first detailed results of experiments
aimed at preventing cavitation damage in jet fuel pumps, which are
essential components in modern aircraft. Appearing in the journal
Physics of Fluids, which is published by the American Institute of
Physics, the results showed great differences in cavitation
behavior between water and JP-8 jet fuel, which is a complex
mixture of more than 228 hydrocarbons and additives, each with its
own fluid properties.
While it can be used to clean jewelry and disintegrate kidney
stones, cavitation is usually considered to be highly detrimental
and to be avoided. It was first described scientifically by
Leonhard Euler in 1754, but the phenomenon made its initial
impression with engineers in 1893 when it caused the failure of a
propeller on the world's fastest ship at the time, Great Britain's
HMS Daring. In modern times, degraded performance is the typical
consequence, as maintenance crews usually discover and replace
damaged components before they fail.
"Improved jet-fuel pumps are needed particularly for military
aircraft being designed to fly at higher altitudes and in other
demanding environments," Dunn said. "But manufacturers still rely
heavily upon trial-and-error in design. If they were confident that
a computer-designed pump would work as predicted, new pumps could
be lighter, more efficient and have longer lifetimes."
The Notre Dame research provides jet-fuel pump designers with
the first realistic data that they can use in their computer models
to make better predictions of vulnerable locations in their pumps
and systems where cavitation bubbles may be created and
collapse.
It's much more difficult to model cavitation in pumps than in
open water, Dunn added, because the fluid typically has a turbulent
journey with accelerated flows though small channels, orifices, and
spinning discs. With so many constituents, jet fuel is also a
computer modeler's nightmare. Its properties can even change with
storage conditions and is often contaminated with microparticles
that can promote cavitation.