Article citation information:
Jasiński, R., Pielecha, J. Evaluation of the impact of oil presence in
the aviation fuel on particle size distribution. Scientific Journal of Silesian University of Technology. Series
Transport. 2017, 94, 57-64. ISSN: 0209-3324. DOI: https://doi.org/10.20858/sjsutst.2017.94.6.
Remigiusz JASIŃSKI[1],
Jacek PIELECHA[2]
EVALUATION OF THE
IMPACT OF OIL PRESENCE IN THE AVIATION FUEL ON PARTICLE SIZE DISTRIBUTION
Summary.
Emissions from aircraft engines represent a highly complex and important issue,
which is related to the risk to human health. Particles emitted in urban areas
and in the vicinity of airports affect air quality and have a particularly
negative impact on airport workers. The development of measurement techniques
and the methodology for evaluating exhaust emissions have allowed for the
elaboration of appropriate procedures for the certification of aircraft and the
enhancement of existing standards. Particulate matter emissions depend, among
other things, on the composition of the fuel used and its additives. Some
aircraft engine designs require a fuel additive in the form of oil, which
ensures the proper operation of the fuel supply system. This article presents
the results of studies conducted on jet engines powered by clean aviation fuel
and fuel with the addition of oil. The aim of the study was to evaluate the
effect of the addition of oil on the size distribution and concentration of
emitted particles. It was found that, for small values of thrust, oil additive
increases the concentration of particles. With an increase in the thrust force,
the reduction of particles concentration was recorded in the case of the engine
powered by fuel with oil additive. There was no significant effect of oil
additive on the size distribution of emitted particles.
Keywords:
aviation engines, particles, fuel additives
1. INTRODUCTION
As a result of the high speed and
intercontinental range of aircraft, air transport has become a major part of
the global transport system [9]. For many years, there has been a strong
correlation between the rate of growth in the largest global economies and the
development of air services [10]. Comparing the growth of gross domestic
product around the world and air traffic, it can be seen that the growth rate
of air transport is greater than the growth of the global economy. According to
an analysis of the largest manufacturers of aircraft (Airbus and Boeing), the
growth in aviation in the near future will be much more dynamic than the
world’s economies. This is because of the dynamic development of low-cost
carriers, increasing the capacity of the aircraft, the introduction of new
fleet and the dynamic growth in emerging markets, such as China, India and
Japan [3]. By 2020, according to forecasts, the market in the Far East will
enjoy the highest growth in world traffic (by 31%). The rapid development of
the Asian market will represent 27% of global air transport conducted in Asia
[3].
The development of air transport is
associated with increased external environmental costs, which, in accordance
with EU definitions, include the impact of the air transport in terms of, inter
alia, air pollution, climate change and noise [4]. These negative effects are
due to the increasing volume of air traffic, as well as associated
infrastructure expansion. Aviation infrastructure is associated with the
occupation of large areas and has a crucial impact on the environment. The
inherent aspect of the functioning of an airport is the handling of air
traffic, which is associated with magnetic radiation and the possibility of
aircraft collisions with animals. Another negative effect of air traffic is air
pollution and its impact on greenhouse effects. According to the European
Environment Agency, air transport only accounts for a 0.5% share of total
emissions of nitrogen oxides and only 0.1% in emissions of non-methane organic
compounds. That said, its impact, particularly on air quality in areas adjacent
to airports, affects the composition of the atmosphere in the upper layers,
where air transport is the only source of pollution. In turn, this negatively
affects the atmosphere on a global scale and contributes to climate change and
ozone layer impoverishment [2].
The various efforts to reduce toxic
emissions are in response to the deterioration of atmospheric air quality,
particularly in urban areas. Currently, one of the biggest problems concerning
air quality in urban areas is the increased concentration of particulate matter
[7, 8], resulting in a reduction of visibility in the form of smog, which also
brings negative effects on human health appearing in the form of heart and lung
disease [5].While the EU has taken legislative measures focused on reducing the
emissions of harmful compounds from automotive vehicles, much more attention
needs to be paid, especially by the scientific community, on exhaust emissions
from aircraft engines.
One of the fundamental issues in the assessment of air quality is the
concentration of particulate matter. The term “particulate matter” describes a
type of air pollutant, consisting of different particle mixtures, which differ
in size, composition and formation. There are many sources of particulate
matter, such as factories, power plants and vehicles. The basic division of
solid particles, due to their aerodynamic diameter, has allowed for the
determination of two main groups, PM2.5 and PM10, which respectively refer to
particulate matter with a diameter of less than 2.5 µm and 10 µm.
In recent years, attention has been increasingly paid to the emissions
from areas around airports, due to the rapid increase in air traffic volume and
the growing demand for air transport in the coming years. Most of the research
and publications in this area offer an inadequate explanation of the phenomena,
which are the subject of intensive research because, as the literature shows,
air transport emissions can significantly affect the quality of the air in the
vicinity of airports [1, 6].
In terms of particle emissions, the chemical composition of the fuel is
very important. Fuel for Jet A-1 turbine aircraft engines is produced from
components obtained under a specific regime involving the technological
processes of hydrodesulphurization, hydrocracking and distillation. The
components meet the established quality requirements. The fuel contains many
additives (antioxidant and antistatic). The use of oil additive in the fuel is
common in military and civil aviation in order to ensure the proper
thermodynamic phenomena and friction. To date, the influence of additives in
aviation fuel on particulate emissions is remains an unexplored issue.
2. OBJECTIVE AND METHODOLOGY
2.1. Purpose of the research
The aim of the study was to determine the size distribution of particles
emitted by the GTM-120 jet engine, powered by Jet A-1 and Jet A-1 aviation fuel
with a 3% addition of Mobil Jet Oil II.
Mobil Jet Oil II is a high-quality
lubricant designed for aircraft gas turbines, based on a combination of a
highly stable synthetic oil base and a unique additive package. This combination
provides thermal and oxidation stability in order to counteract deterioration
and deposit formation in both phases for both liquid and gas, as well as
provide resistance to foaming. The effective range of oil operation is at
temperatures between -40°C and 204°C.
Mobil Jet Oil II is designed for
aircraft turbine engines used in commercial and military service requiring high
performance. It was developed to meet the high requirements of aircraft gas
turbines, operated in a wide range of difficult operating conditions. The
product has a high specific heat in order to ensure a good heat conduction from
oil-cooled parts of the engine. According to extensive laboratory testing and
the verification of performance during flights, oil stability can be observed
at temperatures up to 204°C. At the same time, the evaporation rate at this
temperature is low enough to prevent excessive fluid loss.
Determination of the size
distribution of particles based on the used fuel mixture allowed for the effect
of oil on the emission of a jet engine to be determined. Measurements were
carried out under laboratory conditions on a prepared test stand.
2.2. Test object and measurement
equipment
The object of the study was the GTM-120 turbine
engine (Fig. 1), constructed of a single-stage radial compressor and driven by
a single-stage axial turbine. The test stand with the engine allows for the
measurement of the shaft speed, exhaust gas temperature at the nozzle, thrust,
and exhaust gas mass flow. Particle size distributions were measured at six
points, including in terms of minimum and maximum thrust values. The
measurements were performed twice, once for each fuel mixture used.
For measuring the size distribution of
particles, a TSI Incorporated - EEPS 3090™ mass spectrometer was used, which
enabled the measurement of a discrete particle diameter range (from 5.6 nm to
560 nm) on the basis of their different speeds. The scope of the electric
mobility of the particle matter was exponentially changed, with the particles’
size measured at a frequency of 10 Hz.
Fig. 1. View of the GTM-120 engine
The initial filter retains particles with a
diameter greater than 1 μm and thus are outside the measuring range of the
device. After passing through the neutralizer, the particles are directed to
the charging electrode; after being electrically charged, they can be classed
by their size. The particles deflected by the high-voltage electrode go to an
annular slit, which is the space between the two cylinders. The gap is
surrounded by a stream of clean air supplied from outside. An exhaust cylinder
is built into a stack of sensitive electrodes isolated from one another and
arranged in a ring. The electric field that is present between the cylinders
causes the repulsion of particles from the positively charged electrode; the
particles are then collected on the outer electrodes. When striking the
electrodes, the particles generate an electric current, which is read by a
processing circuit. An exhaust flow meter (EFM) with a diameter of 125 mm and a
high-speed EFM (EFM-HS) flowmeter characterized by a sampling frequency of 2500
Hz were used. The engine workbench and its schematic are shown in Figure 2.
a) b)
Fig. 2. View of a) the
engine workbench and b) its schematic
3. MEASUREMENT RESULTS
AND THEIR ANALYSIS
Diametrical
distributions of particles emitted by the GTM-120 engine turbine were
determined using an apparatus for measuring particulate emissions from
combustion engines. Figures 3-8 present the measurement results for each level
of engine thrust.
In the case of an engine powered by
pure Jet A-1 fuel at minimum value of engine thrust (10 N), particles with a
diameter of 30-45 nm dominated (Fig. 3a). The characteristic value of particle
diametrical distribution obtained from the measurements was 35 nm. There were
no emissions of particles with a diameter greater than 100 nm. The diametrical
distribution of particles emitted in the case of an engine supplied with oil
additive (Fig. 3b) was similar to the distribution obtained when the engine was
fuelled with clean Jet A-1 fuel. The main difference was a twofold increase in
the concentration of particulate matter resulting from the use of oil as a fuel
additive.
a) b)
Fig. 3. Dimensional
distribution of particulate matter corresponding to 10 N
of a jet engine
powered by a) pure Jet A-1 or b) a blend with oil
The
obtained diametrical distributions of particulate matter for the engine fuelled
with Jet A-1 and operated at 25% of maximum thrust were dominated by small
particles with a diameter of 30-50 nm (Fig. 4a). There were no emissions of
particulates with a diameter greater than
100 nm. No significant effect was observed of the addition of oil on
dimensional distribution or concentration of particles emitted.
The
obtained diametrical distributions of particulate matter for the engine fuelled
with Jet A-1 and operated at a medium level of engine load (Figs. 5-6) were
dominated by small particles with a diameter of 25-40 nm. There was no emission
of particulates with a diameter greater than 100 nm. The addition of oil to the
Jet A-1 fuel caused an almost twofold reduction in the concentration of
particulate matter in the exhaust of the jet engine (Fig. 6).
Increasing
the level of engine load for the engine fuelled with Jet A-1 to 80-100%
resulted in a reduction of the diameter of the particles emitted (Figs. 7-8).
Emissions were dominated by particles with the smallest diameters, from 15 nm
to 25 nm. The use of oil additive resulted in no change in the size distribution
of particles compared to the distribution obtained for the particles emitted
from an engine supplied with clean jet fuel. It was found that using oil
additive causes a slight reduction in particulate matter concentration.
a) b)
Fig. 4. Dimensional
distribution of particulate matter corresponding to 30 N
of a jet engine
powered by a) pure Jet A-1 or b) a blend with oil
a) b)
Fig. 5. Dimensional
distribution of particulate matter corresponding to 50 N
of a jet engine
powered by a) pure Jet A-1 or b) a blend with oil
a) b)
Fig. 6. Dimensional
distribution of particulate matter corresponding to 70 N
of a jet engine
powered by a) pure Jet A-1 or b) a blend with oil
a) b)
Fig. 7. Dimensional
distribution of particulate matter corresponding to 100 N
of a jet engine
powered by a) pure Jet A-1 or b) a blend with oil
a) b)
Fig. 8. Dimensional
distribution of particulate matter corresponding to 120 N
of a jet engine
powered by a) pure Jet A-1 or b) a blend with oil
4. CONCLUSIONS
In order to
consider the effects of the addition of oil to fuel on the intensity of the
emissions of particle matter, proper measurements were performed on the GTM-120
jet engine, powered with pure kerosene (Jet A-1) fuel and its blend with oil
(Mobil Jet Oil II). The presence of oil in the fuel resulted in a change in the
concentration of particles emitted by the turbine engine in relation to the
distributions recorded when using the Jet A-1 fuel without additives. In the
case of the minimum level of thrust, oil additive causes an increase in the
concentration of particulate matter compared to an engine powered by clean Jet
A-1 fuel. There were no significant changes in the size distribution of
particles emitted from the jet engine due to the use of oil additive.
Increasing turbine engine thrust resulted in a particle concentration decrease
for the engine fuelled with the oil additive. It was noticed that using oil
additive causes a significant reduction in the number of emitted particulates
for an engine operating at medium and high load levels. In the full range of
measurements, the addition of oil did not result in significant changes in the
size distribution of emitted particles.
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Received 07.12.2016;
accepted in revised form 29.02.2017
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