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Summer 2016 European Energy Innovation  25


                                           Figure: Properties evaluated all along the aircraft fuel use chain in the EXPLIC program

of expense (representing up t	o            Volume variation of nitrile, fluorosilicon, fluorocarbone O-rings aged 28 days in JetVolume variation (%)
                                           A-1/SPK blends (aromatic % 2.4, 4, 6, 8 and 20.6) compared to unaged O-rings
30% of direct operating costs) with
unpredictable, large fluctuations that                                                                                                                       SPK (2.4%)
were difficult to manage. In the longer          10 4%
term, crude oil will rise in price again.
Moreover, security of supply is an issue                                                                                                                    6%
for a sector which today fully depends                                                                                                                      8%
on “fossil” hydrocarbon fuel.                                                                                                                               Jet A-1 (20.6%)

Compared to other transport modes,

the introduction of alternative fuels in                         5
aviation requires careful consideration

due to the particular requirements

of aviation fuels (low temperature

properties, high energy content,

etc.) that exclude the use of the fuels

currently deployed for road transport.                           -1
In addition, aviation fuels need to be
approved to international standards                                  Nitrile     Fluorosilicone   Fluorocarbone 	
by all stakeholders before being

deployed.                        Figure : Voliunmvoelvveadriantpiornogorfanmitsrdile,dfilcuaoterodstiolicone, fluTohreosceatrhbroeenestOra-nridnsgosf awgoerdk a2r8edays in Jet A-1/SPK

                                           alternbalteivnedfsue(alsrofomraatiirccr%aft2s.s4u, c4h, 6a,s8 and 2c0o.6n)scisotemnpt awriethdttwoousnigangiefidcaOn-triisnsguses

The field of alternative fuels is moving    CALIN (French program), DREAM         of alternative jet fuel development

fast. The landscape of alternative fuels   and ALFA-BIRD (both FP7 funded)       (decrease of the aromatic content

in aviation has significantly evolved with and was the coordinator of SWAFEA      and introduction of fuels with

the approval by ASTM of the Fischer-       (European commission program). It     narrow distribution of molecules).

Tropsch Synthetic Paraffinic Kerosenes      was decided in 2013 to self-finance    The experimental work is based

(FT-SPK), the Hydroprocessed               a program on alternative jet fuels.   on a combination of standard tests

Esters and Fatty Acids (HEFAs), the        The main objectives of this ONERA     and complementary tests aimed at

Synthesised Iso-Paraffinic (SIP) fuels and funded program, called EXPLIC, is to   promoting the better understanding of

very recently (march 2016) the Alcohol better understand the consequences        the phenomena involved.

to Jet (AtJ) fuels. None of these fuels    of the chemical modification of a jet

contains aromatics. One of the current fuel on its performance criteria and to One of the strengths of this project is

limitations of the blending ratio (50 %    determine the acceptable blending     to work all along the aircraft fuel use

for FT-SPK and HEFAs) stems from the       limits of alternative jet fuels in fossil jet chain. The influence of the chemical

lack of aromatics that keeps them from fuels. In order to do so, focuses will    composition is determined on

matching the specification for density,     be done:                              physicochemical properties (density,

lubricity and compatibility with some                                            viscosity, net heat of combustion…),

polymer materials. Currently, fuels with • to determine the minimal              thermal stability, cold flow behaviour,

less than 8% aromatics cease to be         concentration of the aromatics        material compatibility, spraying,

“drop-in”. Combustion tests have shown     compounds suitable with a drop-in     ignition, emissions…That is to say the

that a potential benefit of decreasing      concept;                              behavior of the fuel is studied from the

the aromatic content would be the                                                storage up to the emissions.

reduction of particulates emissions. By • to better understand the role of

far, the most obvious problem is the       various types of aromatics (mono- or Beyond the scientific results, it allows

impact on seals. Low or zero aromatic      di-aromatics);                        ONERA acquiring a deeper knowledge

fuels represent an unknown with                                                  of the technical problematic of the

significant risk of causing seals leakage. • to study the impact of alternative   alternative jet fuels and developing

                                           fuels with a disrupted profile         new skills on jet fuel characterisations

From 2007, ONERA has become                blended with “fossil” jet fuels.      and modeling. ●
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