New X-ray technique may lead to better, cleaner fuel
injectors for automobiles
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ARGONNE, Ill. (Feb. 19, 2008) — Standard microscopy and visible light imaging
techniques cannot peer into the dark and murky centers of dense-liquid jets,
which has hindered scientists in their quest for a full understanding of
liquid breakup in devices such as automobile fuel injectors.
The Advanced Photon Source, located at Argonne National Laboratory,
is funded by the U.S. Department of Energy's Office of Basic
Energy Sciences as part of its mission to foster and support fundamental research to
expand the scientific foundations for new and improved energy technologies
and for understanding and mitigating the environmental impacts of energy
use. |
Scientists at the U.S. Department of Energy's (DOE) Argonne National Laboratory
have developed a technique to peer through high-speed dense liquids using high-energy
X-rays from Argonne's Advanced Photon Source (APS).
“The imaging contrast is crisp and we can do it orders of magnitude faster
than ever before,” Argonne X-ray
Science Division physicist Kamel Fezzaa said.
Fuel injector efficiency and clean combustion is dependent on the best mixture
of the fuel and air. To improve injector design, it is critical to understand
how fuel is atomized as it is injected. However, standard laser characterization
techniques have been unsuccessful due to the high density of the fuel jet near
the injector opening. Scientists have been forced to study the fuel far away
from the nozzle and extrapolate its dispersal pattern. The resulting models
of breakup are highly speculative, oversimplified and often not validated by
experiments.
“Research in this area has been a predicament for some time, and there has
been a great need for accurate experimental measurement,” Fezzaa said. “Now
we can capture the internal structure of the jet and map its velocity with
clarity and confidence, which wasn't possible before.”
Fezzaa and his colleagues, along with collaborators from Visteon Corp. developed
a new ultrafast synchrotron X-ray full-field phase contrast imaging technique
and used it to reveal instantaneous velocity and internal structure of these
optically dense sprays. This work is highlighted in the Advance Online Publication
of the journal Nature Physics.
A key to the experiment was taking advantage of the special properties of
the X-ray beam generated at the APS. Unlike hospital x-rays, the synchrotron
x-rays are a trillion times brighter and come in very short pulses with durations
as little as 0.1 nanoseconds.
“The main challenge that our team had to overcome was to be able to isolate
single x-ray pulses and use them to do experiments, and at the same time protect
the experimental setup from being destroyed by the overwhelming power of the
full x-ray beam,” Fezzaa said.
Their new technique has the ability to examine the internal structure of materials
at high speed, and is sensitive to boundaries. Multiphase flows, such as high-speed
jets or bubbles in a stream of water, are ideal systems to study with this
technique. Other applications include the dynamics of material failure under
explosive or ballistic impact, which is of major importance to transportation
safety and national security, and material diffusion under intense heat.
Argonne National Laboratory seeks solutions to pressing national problems in science and technology.
The nation's first national laboratory, Argonne conducts leading-edge basic
and applied scientific research in virtually every scientific discipline. Argonne
researchers work closely with researchers from hundreds of companies, universities,
and federal, state and municipal agencies to help them solve their specific
problems, advance America 's scientific leadership and prepare the nation for
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Argonne, LLC for
the U.S.
Department of Energy's Office
of Science.
For more information, please contact Brock Cooper (630/252-5565 or media@anl.gov) at Argonne.
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