10Several alternative synthetic fuels are in discussion as a replacement for conventional fuels like Jet A-1 11 to cope with limited supplies of crude oil as well as their emissions connected with its use such as the 12 greenhouse gas CO 2 . One of the alternative fuels which have received high attention recently is far-13 nesane (2,6,10-trimethyldodecane), a biofuel produced from sugar using a biotechnological process. 14 In this paper, combustion characteristics of farnesane were investigated by measuring its ignition 15 delay time using a shock tube at elevated pressure (16 bar) and two different stoichiometries ( = 1.0 16 and = 2.0) and the laminar burning velocity at atmospheric and elevated pressures (1, 3, and 6 bar). 17These results were compared to a conventional Jet A-1 fuel showing that farnesane has a similar 18 combustion behavior. Furthermore, a reaction model was developed capable to predict the measured 19 combustion properties. The calculation of the ignition delay times yields excellent results when com-20 pared to the measurements; the computations of the laminar flame speeds are in good agreement 21 with the measurements. In addition, the reaction model was analyzed to get further insight into the 22 main reaction steps of farnesane oxidation. 23 24 eling 26 flight conditions, e.g. cold temperatures at high altitude. Moreover, this certification assures that the 40 new synthetic jet fuel is compatible with current engines and technology and that synthetic jet fuel 41 blends are interchangeable with conventional aviation fuels to prevent any logistics or storage prob-42 lems at airports that may arise due to the handling of different fuels. 43The use of coal or natural gas as feedstock for synthetic fuel production via the Fischer-Tropsch 44 process (CtL or GtL) led to the first approved alternative fuels for blending up to 50 %. Moreover a 45CtL production process exists which yields a fully synthetic jet fuel (FSJF), meaning that it can be used 46 as a replacement of crude oil based fuels without blending [2]. This is of course an alternative to the 47To benefit from biofuels -a sustainable replacement for crude oil based fuels, reduction of overall 52 emissions, including the greenhouse gas CO 2 [3, 9] -other fuels, processes and technologies were 53 developed. Approved in 2014 [10], a biofuel for aviation which can be used as a drop-in-fuel is far-54 nesane [8], a branched alkane with 15 carbon atoms as it is shown in Fig. 1. Its chemical name is 55 2,6,10-trimethyldodecane; for a better readability, only the name farnesane is used in this paper. The 56 production of farnesane has three major steps. At first, sugar is fermented by yeast to farnesene, a 57 molecule with four double bonds [11]. The second step is the hydrogenation from farnesene to far-58 nesane which in the last step is purified by distillation [8]. Whereas Jet A-1 is a multicomponent mix-59 ture [2] farnesane is a single component with a molecular size being in the upper range of the molec-60 ular size distribution typical...
Almost the complete amount of jet fuel available on the global market is produced from fossil crude oil being an exhaustible raw material. Furthermore, its use is inherently connected with emissions of the greenhouse gas CO 2. To cope with this, several processes for the production of alternative aviation fuels were developed including the use of biomass as a renewable feedstock. Since biomass from cultivation farming is in competition with food and fodder production, the preferred raw material would be residues from agriculture and forestry or municipal waste, also microalgae can be used. Independent of the raw material, the conversion of biogenic feedstock into alternative jet fuel is based on microbial, thermal and/or chemical breakdown of larger (bio)-molecules into smaller ones, followed by the catalytic formation of fuel molecules and hydrogenation. An overview on the production of different alternative bio-based jet fuels is given including a survey about producers and capacities, focusing on already certificated bio-based jet fuels. In addition to that, a comparison of fundamental combustion properties between Jet A-1 and different alternative jet fuels is presented: Laminar burning velocities and ignition delay times, each measured for two synthetic jet fuels based on fossil resources (coal-to-liquid-CtL and gas-to-liquid-GtL) as well as for two biofuels (farnesane and an Alcohol-to-Jet fuel-AtJ). Measurements of the burning velocities were performed at a preheat temperature of 473 K and pressures of 1 bar and 3 bar by variation of the fuel-air-equivalence ratios φ. Ignition delay times were determined for φ-values of 0.5, 1.0, and 2.0, at an initial pressure of about 16 bar and temperatures ranging between 800 K and 1700 K. It turns out that with respect to the characteristic combustion properties tested the considered alternative fuels have a combustion behavior similar to Jet A-1.
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