UWE Bristol Engineering showcase 2015

David Kilvington
MEng. Aerospace Systems Engineering
An Investigation into the Detection and Measurement of Water
Concentration in Jet Fuel using Absorption Spectroscopy Techniques
Introduction
This dissertation investigates the possibility of
using optical technology, harnessing
absorption spectroscopy techniques to
identify water, jet fuel layers and measure
water concentration within jet fuel, for use
within an aircraft fuel system. In part A of this
report a study was undertaken to identify
water, jet fuel and kerosene layers and
measure water concentration within
kerosene and jet fuel using an UV/VIS, FTIR
spectrometer between wavelengths 4000-
600 .
What is Spectroscopy?
Spectroscopy is the study of the interaction
between radiated energy and matter. It
measures the level of rational intensity as a
function of wavelengths. Studying the
frequency ranges that are absorbed or
reflected through a substance provide
important clues to the functional groups,
which are present. Functional groups absorb
at similar frequencies in many different
compounds, so an absorption pattern can be
provided as a finger print of the molecule.
Water in Aircraft Fuel Tanks
Water within an aircraft fuel system can cause
serious issues for aircraft operators, such as
microbial growth, forming in water hydrocarbon
divergence layers, blocking pump filters. The
capacitance based fuel quantity measurement
systems can malfunction due to the disparity in
the dielectric constant of jet fuel and water. With
commercial aircraft operating at temperatures
below -50˚C free water will form ice, causing
defects in fuel system equipment. These
complications increase aircraft turnaround times,
operator’s expenditure and in rare cases have
safety implications.
Absorption spectrum of anhydrous Jet A-1 between 4000-
600ccmm −11 with resolution 4 ccmm −11 with zinc selenide fixed
path length cell
Absorption spectrum of deionised between 4000-600 ccmm −11 at
4 ccmm −11 resolution with zinc selenide fixed path length cell
Experimental Method
10 ml test samples of kerosene and jet fuel (type
jetA-1) with different water concentrations were
created using differing ratios of anhydrous and
saturated samples.
Water concentration was directly measured in
the anhydrous, saturated and standard kerosene
and jet fuel samples with a Karl Fischer
coulometer.
Experiments were carried out using an UV/VIS
spectrometer fitted with a fixed length zinc
selenide spec cell between 4000-600 cm −1
wavelengths. Scans of kerosene, jet fuel and
water were taken for analysis. Measurements of
anhydrous and saturated blends were taken
between 4000-3000 cm −1 ; with a background
scan of the cell with anhydrous sample present,
so corrected absorbance could be calculated. The
peak height of the corrected absorbance at the
different water concentrations was measured.
Major Findings
• 4000-3000 cm −1 wavelengths is the most
viable region within the UV/VIS spectrum
for analysis of water in jet fuel
• Measurements undertaken between 4000-
3000 cm −1 found there was positive linear
correlation between corrected absorbance
peak heights against water concentration.
• The kerosene and jet fuel samples
absorbance increased at the same gradient
with increased water concentration, but
the kerosene sample was offset with
higher absorbance for a given
concentration
Project Supervisor
Professor Norman Ratcliffe
Project Summary
Airbus are investigating possible alternative fuel
gauging technologies that would be an improvement
on the current capacitance systems. This body of
work hopes to shed light on the possibility of applying
optical sensors using absorption spectroscopy
techniques to measure water concentrations and
levels within a fuel system. This system is hoped
could offer additional attribute’s in:
• Distinguishing between water, fuel and air
• Characterise the type and chemical composition
of fuel
• Detect and measure water concentration
The system may be more intrinsically safe with only
light entering the fuel tank and be able to detect and
measure water levels within the fuel system. These
benefits could improve overall aircraft performance
and safety.
This report will investigate the ability of absorption
spectroscopy to identify water, fuel layers and make
accurate measurements of water concentrations
within fuel
Project Objectives
The aims for part A of the project to be completed
are as follows:
• To measure water concentration in jet fuel and
kerosene at a range of concentrations using an
FTIR Spectrometer between 4000-600
• To identify the best region on this spectra for
analysis of water concentration.
• To identify clear definition between water, jet fuel
and kerosene within the absorption spectrum
Project Conclusion
The central implication of this study is that it is
possible to detect water and jet fuel in by UV/VIS
absorption spectroscopy between wavelengths of
4000-3000 and that it is possible with a certain level
of error to measure water concentration up to
saturation level. This could be applied to an optical
detection system for use within an aircraft fuel
system.