DSA Volume 1 Issue 4 December 2010 - Defence Science and ...

DEFENCE SCIENCE AUSTRALIA
eventually be built into storage tanks,
thereby obviating the need to open the
tank for sampling and eliminating the risk
that the contents may spoil or be exposed
to contamination.
Jet fuel monitoring
One possible application of considerable
interest to the Australian Defence Force
(ADF) is for monitoring aircraft fuel quality.
Fuel has a dual role in modern jet aircraft,
providing not only engine power but also
cooling for the engines, with fuel being
circulated around engine parts to draw
away heat that would otherwise cause
damage over time.
The effect of the heat on fuel, however, is to
cause quality degradation that diminishes
engine performance and the life of certain
parts. Fuel degradation can happen
very quickly, and occurs in somewhat
unpredictable ways, so the ability to
monitor in situ for impending degradation is
seen to offer a valuable management tool.
Optical fibre sensing technology can
do so via use of a sensor chemically
sensitised to detect hydroperoxide, the
presence of which indicates the initial state
of fuel degradation.
This form of monitoring, producing virtually
instantaneous results in support of real-time
decision-making, could also be used for
monitoring the quality of other fluids such
as turbine oils and hydraulic fluids.
Sensing the effects of corrosion
Another application of major interest to
the ADF is that of detecting corrosion on
aircraft structures.
Aircraft maintenance inspections are
currently difficult, costly and timeconsuming,
and in some cases, involve the
dismantling of aircraft structures for manual
inspection of hard-to-access parts.
The development by IPAS of open-core
chemically sensitised sensors that fluoresce
in the presence of aluminium ions, a
corrosion by-product of aluminium
structures, promises to significantly improve
this situation.
To monitor alloy condition at a particular
site, a sensor with fully exposed core is laid
over it. Multiple sensors can be fabricated
into a single optical fibre, with monitoring
undertaken via pulsed laser light emissions
that elicit time-series sets of fluorescence
spectra ‘echoes’.
Any such echoes detected indicate not only
that corrosion is happening, and how much is
happening, but also where it is happening, as
revealed by the time of signal return.
The eventual aim of the work is to allow for
corrosion monitoring through a simple check
of signals from sensors built into aircraft at
each site where corrosion is known to be a
problem, thereby greatly reducing inspection
costs and aircraft downtime.
DSTO support for the research
DSTO’s Corporate Enabling Research Program
(CERP) in Signatures, Materials and Energy
is supporting the IPAS research on corrosion
detection and fuel degradation monitoring
through top-up scholarships awarded to
Stephen Warren-Smith and Erik Schartner for
their doctoral studies in these areas.
“The joint IPAS-DSTO programs in corrosion
detection and fuel degradation monitoring
offer highly innovative approaches and
promising solutions to long-standing
issues affecting the availability and cost-ofownership
of ADF assets,” says CERP Program
Leader, Dr Christine Scala.
The various kinds of microstructured sensors
in development are expected to be available
for field-testing within two to five years.
Opposite page: Design for nanorail optical fibre in the preform stage of production.
Top: IPAS optical fibre sensor apparatus for assaying liquid sample.
Above: Close-up of IPAS optical fibre sensor components.
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