scholarly journals A Study on the Emissions of Alternative Aviation Fuels

2017 ◽  
Vol 139 (8) ◽  
Author(s):  
Sebastian Riebl ◽  
Marina Braun-Unkhoff ◽  
Uwe Riedel
Keyword(s):  
Crude Oil ◽  
Plug Flow ◽  
Synthetic Jet ◽  
Jet Fuels ◽  
Detailed Knowledge ◽  
Low Carbon ◽  
Emission Data ◽  
Chemical Kinetic Model ◽  
Soot Precursors ◽  
Synthetic Aviation

Currently, the aviation sector is seeking for alternatives to kerosene from crude oil, as part of the efforts combating climate change by reducing greenhouse gas (GHG) emissions, in particular carbon dioxide (CO2), and ensuring security of supply at affordable prices. Several synthetic jet fuels have been developed including sustainable biokerosene, a low-carbon fuel. Over the last years, the technical feasibility as well as the compatibility of alternative jet fuels with today's planes has been proven However, when burning a jet fuel, the exhaust gases are a mixture of many species, going beyond CO2 and water (H2O) emissions, with nitrogen oxides (NOx), carbon monoxide (CO), unburned hydrocarbons (UHC) including aromatic species and further precursors of particles and soot among them. These emissions have an impact on the local air quality as well as on the climate (particles, soot, contrails). Therefore, a detailed knowledge and understanding of the emission patterns when burning synthetic aviation fuels are inevitable. In the present paper, these issues are addressed by studying numerically the combustion of four synthetic jet fuels (Fischer–Tropsch fuels). For reference, two types of crude-oil-based kerosene (Jet A-1 and Jet A) are considered, too. Plug flow calculations were performed by using a detailed chemical-kinetic model validated previously. The composition of the multicomponent jet fuels was imaged by using the surrogate approach. Calculations were done for relevant temperatures, pressures, residence times, and fuel equivalence ratios φ. Results are discussed for NOx, CO as well as for benzene and acetylene as major soot precursors. According to the predictions, the NOx and CO emissions are within about ±10% for all fuels considered, within the parameter range studied: T = 1800 K, T = 2200 K; 0.25 ≤ φ ≤ 1.8; p = 40 bar; t = 3 ms. The aromatics free GtL (gas to liquid) fuel displayed higher NOx values compared to Jet A-1/A. In addition, synthetic fuels show slightly lower (better) CO emission data than Jet A-1/A. The antagonist role of CO and NOx is apparent. Major differences were predicted for benzene emissions, depending strongly on the aromatics content in the specific fuel, with lower levels predicted for the synthetic aviation fuels. Acetylene levels show a similar, but less pronounced, effect.

scholarly journals A Study on the Emissions of Alternative Aviation Fuels

2016 ◽  
Author(s):  
Sebastian Riebl ◽  
Marina Braun-Unkhoff ◽  
Uwe Riedel
Keyword(s):  
Crude Oil ◽  
Plug Flow ◽  
Synthetic Jet ◽  
Jet Fuels ◽  
Detailed Knowledge ◽  
Low Carbon ◽  
Emission Data ◽  
Chemical Kinetic Model ◽  
Soot Precursors ◽  
Synthetic Aviation

Currently, the aviation sector is seeking for alternatives to kerosene from crude oil, as part of the efforts combating climate change by reducing greenhouse gas (GHG) emissions, in particular carbon dioxide (CO2), and ensuring security of supply at affordable prices. Several synthetic jet fuels have been developed including sustainable bio-kerosene, a low-carbon fuel. Over the last years, the technical feasibility as well as the compatibility of alternative jet fuels with today’s planes has been proven However, when burning a jet fuel, the exhaust gases are a mixture of many species, going beyond CO2 and water (H2O) emissions, with nitrogen oxides (NOx), carbon monoxide (CO), unburned hydrocarbons (UHC) including aromatic species and further precursors of particles and soot among them. These emissions have an impact on the local air quality as well as on the climate (particles, soot, contrails). Therefore, a detailed knowledge and understanding of the emission patterns when burning synthetic aviation fuels is inevitable. In the present paper, these issues are addressed by studying numerically the combustion of four synthetic jet fuels (Fischer-Tropsch fuels). For reference, two types of crude-oil based kerosenes (Jet A-1 and Jet A) are considered, too. Plug flow calculations were performed by using a detailed chemical-kinetic model validated previously. The composition of the multi-component jet fuels were imaged by using the surrogate approach. Calculations were done for relevant temperatures, pressures, residence times, and fuel equivalence ratios φ. Results are discussed for NOx, CO as well as benzene and acetylene as major soot precursors. According to the predictions, the NOx and CO emissions are within about ± 10% for all fuels considered, within the parameter range studied: T = 1800 K, T = 2200 K; 0.25 ≤ φ ≤ 1.8; p = 40 bar; t = 3 ms. The aromatics free GtL (Gas to Liquid) fuel displayed higher NOx values compared to Jet A-1/A. In addition, synthetic fuels show slightly lower (better) CO emission data than Jet A-1/A. The antagonist role of CO and NOx is apparent. Major differences were predicted for benzene emissions, depending strongly on the aromatics content in the specific fuel, with lower levels predicted for the synthetic aviation fuels. Acetylene levels show a similar, but less pronounced, effect.

Reaction Model Development for Synthetic Jet Fuels: Surrogate Fuels As a Flexible Tool to Predict Their Performance

2018 ◽  
Author(s):  
Trupti Kathrotia ◽  
Sandra Richter ◽  
Clemens Naumann ◽  
Nadezhda Slavinskaya ◽  
Torsten Methling ◽  
...  
Keyword(s):  
Reaction Mechanism ◽  
Crude Oil ◽  
Reaction Mechanisms ◽  
Reaction Model ◽  
Jet Fuel ◽  
Synthetic Jet ◽  
Jet Fuels ◽  
Synthetic Fuel ◽  
Soot Precursors ◽  
Combustion Properties

In the last years, the development of synthetic aviation jet fuels has attracted much interest, to provide alternatives to crude-oil based kerosene. Synthetic jet fuels can be produced from a variety of feedstocks and processes. To limit possible harmful effects on the environment when burning a jet fuel, discussions are attributed to the effects of the specific composition of a synthetic fuel on its performance and its emission pattern. A numerical tool, if available, would also be helpful within the specification process any aviation jet fuel must pass. The present work contributes to the studies and efforts how to design a synthetic jet fuel to match predefined properties, e.g. the energy content or a less harmful emission characteristics compared to Jet A-1. The approach of a generic fuel will be followed in order to design a synthetic jet fuel with pre-defined chemical properties: A chemical kinetic reaction mechanism will be elaborated capable predicting the fundamental combustion properties of the generic fuel for each possible mixing ratio of the components included. In this work, a generic mixture serving as an innovative synthetic jet fuel was studied, with n-dodecane, cyclohexane, and iso-octane chosen as single fuel components; no aromatics were added to reduce the concentration of soot precursors. Then, their fundamental combustion properties, i.e. laminar burning velocity and ignition delay time, were measured in a burner test rig and applying the shock tube technique, respectively. These experimental data were used for the validation of the reaction mechanisms developed for each single fuel component, which were then combined to the reaction mechanism for the generic fuel under consideration. To allow a comparison of the combustion behavior of the synthetic jet fuel directly, with the same reaction mechanism, to Jet A-1, toluene was added as a model component for aromatics. A reduced surrogate reaction model was produced, too. All the reaction mechanisms elaborated are shown to reasonably predict the fundamental combustion properties within the parameter range considered. The compact reduced surrogate model can serve as a virtual jet fuel within numerical simulations. Thus, ultimately, an estimation of the suitability of an innovative synthetic jet fuel as a blending component to crude-oil kerosene is enabled. As a result, CFD simulations can be run efficiently tackling the combustion of a synthetic fuel in a jet engine under practical conditions and by taking into account the interaction between turbulence and chemistry.

The Combustion of Synthetic Jet Fuels (Gas to Liquid and Coal to Liquid) and Multi-Component Surrogates: Experimental and Modeling Study

2015 ◽  
Author(s):  
Philippe Dagaut ◽  
Guillaume Dayma ◽  
Florent Karsenty ◽  
Zeynep Serinyel
Keyword(s):  
Chemical Kinetic ◽  
Synthetic Jet ◽  
Sensitivity Analyses ◽  
Jet Fuels ◽  
Chemical Kinetic Model ◽  
Experimental Database ◽  
Stirred Reactor ◽  
Auto Ignition ◽  
Gas To Liquid ◽  
Using Data

Research on synthetic jet fuels production and combustion has recently gained importance because they could help addressing security of supply and sustainable air transportation challenges. The combustion of a 100% Gas to Liquid from Shell (C10.45H23.06; M=148.44 g.mol−1; H/C=2.20; density=737.7 g L−1), a 100% vol. Coal to Liquid from Sasol (C11.06H21.6; M=154.32 g mol−1; H/C=1.95; density= 815.7 g L−1) and surrogates composed of various concentrations of n-decane iso-octane, n-propylcyclohexane, n-propylbenzene, and decalin, were studied in a jet-stirred reactor under the same conditions (temperature, 550–1150 K; pressure, 10 bar; equivalence ratio, 0.5–2). Comparison of these results helped designing optimum surrogate model fuels for the chemical kinetic computations. For simulating the kinetics of oxidation of the synthetic fuels we used new surrogates consisting of mixtures of n-decane, iso-octane, 2-methylheptane, 3-methylheptane, decalin, n-propylcyclohexane, n-propylbenzene, and tetralin. The detailed chemical kinetic reaction mechanism proposed here consisted of 2430 species reacting in 10962 reversible reactions. It was validated using the entire experimental database obtained previously in our laboratory and in the present work. The current chemical kinetic model was also tested for the auto-ignition under shock tubes using data from the literature. Kinetic computations involving reaction paths analyses and sensitivity analyses were used to interpret the results.

scholarly journals Transforming carbon dioxide into jet fuel using an organic combustion-synthesized Fe-Mn-K catalyst

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Benzhen Yao ◽  
Tiancun Xiao ◽  
Ofentse A. Makgae ◽  
Xiangyu Jie ◽  
Sergio Gonzalez-Cortes ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Crude Oil ◽  
Raw Materials ◽  
Combustion Process ◽  
Combustion Method ◽  
Jet Fuel ◽  
Light Olefins ◽  
Jet Fuels ◽  
Low Carbon ◽  
Fossil Carbon

AbstractWith mounting concerns over climate change, the utilisation or conversion of carbon dioxide into sustainable, synthetic hydrocarbons fuels, most notably for transportation purposes, continues to attract worldwide interest. This is particularly true in the search for sustainable or renewable aviation fuels. These offer considerable potential since, instead of consuming fossil crude oil, the fuels are produced from carbon dioxide using sustainable renewable hydrogen and energy. We report here a synthetic protocol to the fixation of carbon dioxide by converting it directly into aviation jet fuel using novel, inexpensive iron-based catalysts. We prepare the Fe-Mn-K catalyst by the so-called Organic Combustion Method, and the catalyst shows a carbon dioxide conversion through hydrogenation to hydrocarbons in the aviation jet fuel range of 38.2%, with a yield of 17.2%, and a selectivity of 47.8%, and with an attendant low carbon monoxide (5.6%) and methane selectivity (10.4%). The conversion reaction also produces light olefins ethylene, propylene, and butenes, totalling a yield of 8.7%, which are important raw materials for the petrochemical industry and are presently also only obtained from fossil crude oil. As this carbon dioxide is extracted from air, and re-emitted from jet fuels when combusted in flight, the overall effect is a carbon-neutral fuel. This contrasts with jet fuels produced from hydrocarbon fossil sources where the combustion process unlocks the fossil carbon and places it into the atmosphere, in longevity, as aerial carbon - carbon dioxide.

scholarly journals Investigation of the sooting propensity of aviation fuel mixtures

2020 ◽  
Author(s):  
S. Richter ◽  
T. Kathrotia ◽  
C. Naumann ◽  
S. Scheuermann ◽  
U. Riedel
Keyword(s):  
Aromatic Compounds ◽  
Soot Formation ◽  
Hydrocarbon Fuel ◽  
Synthetic Jet ◽  
Molecular Structures ◽  
Aviation Fuel ◽  
Jet Fuels ◽  
Radiation Balance ◽  
Detailed Knowledge ◽  
Fuel Mixtures

AbstractAromatic compounds occurring naturally in jet fuels are precursors for the formation of soot in the exhaust gas of jet engines. Directly emitted in cruising altitude, soot particles lead to the formation of contrails and clouds influencing the radiation balance of the atmosphere. Hence, a detailed knowledge on the effect of aromatics on the sooting behavior is of great importance, especially for the development of alternative synthetic jet fuels. Investigations on the sooting propensity influenced by the molecular structure and concentration of diverse aromatic compounds contained in synthetic and fossil aviation fuels as well as blends of synthetic paraffinic kerosene (SPK) with aromatic compounds (SKA) were carried out experimentally. Using a predefined SPK fuel, five different blends—each containing a single aromatic compound—were prepared in addition to one blend with a typical composition consisting of all these aromatic compounds. In subsequent measurements, the concentration of the aromatics was increased from initially 8.0 vol%, to about 16.5, and 25.0 vol%. The aromatics added were toluene, n­-propylbenzene, indane, 1­methylnaphthalene, and biphenyl. The studied jet fuels include fossil-based Jet A-1 as well as different synthetic jet fuels (with and without aromatics). Furthermore, the experimental results of the sooting propensity are compared with the results of the hydrogen deficiency model being a measure for the amount of cyclic and unsaturated molecular structures occurring in a hydrocarbon fuel. This study shows the hydrogen deficiency as a useful tool to make predictions about the sooting behavior of different fuels compared to a reference fuel at a specified condition. Additionally, it is observed from the measured sooting propensities as well as from the model predictions of hydrogen deficiency that the structure of aromatic compounds presents greater influence on the soot formation than the aromatic concentration.

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