Full Length ArticleTechnical application of a ternary alternative jet fuel blend – Chemical characterization and impact on jet engine particle emission
Introduction
The aviation sector is facing particular challenges surrounding climate protection targets in light of the Paris Climate Agreement. Prior to the worldwide COVID-19 pandemic, the aviation industry showed growth rates between 3 % and 6 % (2015 – 2019) [1]. Despite the strong decrease in flight movements in 2020, the aviation industry will also require high amounts of jet fuel in the future. The use of sustainable aviation fuels (SAF) as a substitute for fossil fuels will play an important role in reducing CO2 emissions in aviation and fulfilling future regulations on greenhouse gas emissions. A further driver for the increased application of alternative jet fuels is the increasing relevance of airports as an emission source of ultra-fine particles (UFP). Several studies worldwide showed the release of UFP into the environment that could be attributed to jet engine emissions [2], [3], [4], [5]. Aircraft jet engines release volatile and non-volatile particles which feature different aerosol dynamics, airborne transport range and exposure potential [6], [7]. Lab and field studies with alternative jet fuel blends have demonstrated that jet fuels with an elevated hydrogen content (low amount of unsaturated hydrocarbons) show lower soot emissions than a regular reference Jet A-1 for the same engine [8], [9], [10], [11], [12]. However, in order to use SAF in aviation, compliance with sustainability criteria have to be monitored along the entire supply chain. Furthermore, it must be ensured that fuel mixtures containing different alternative fuel components do not deviate from current fuel specifications for Jet A-1 (“drop-in fuel”).
The primary goal of the research and demonstration project on the use of renewable kerosene at Leipzig/Halle Airport (short: DEMO-SPK) was to examine and verify the behavior of blends of several renewable SAF with fossil Jet A-1 under realistic conditions in the supply infrastructure of a major airport. Another aim was to successfully demonstrate the use of Multiblend Jet A-1 in the general fuel supply infrastructure, from procurement to aircraft fueling operations, on the international level for the first time. The key results are promising [13]. The project demonstrated that the supply chain for Multiblend Jet A-1 was technically feasible and that the fuel could be used without making any changes in normal operating procedures. The project also verified that the use of Multiblend Jet A-1 resulted in a reduction of about 35 % in CO2 equivalents compared with pure fossil Jet A-1. A number of solutions and recommendations to facilitate practical use were developed as well [13].
This study aims to summarize the findings with regard to the emission of ultra-fine particles from the use of the Multiblend Jet A-1 produced within the framework of DEMO-SPK. Two types of alternative jet fuel mixtures have been analyzed in a flow reactor experiment regarding their expected soot formation potential. Due to limitations in the availability of certain fuel components only one mixture has been tested on the engines of an A300 regarding the soot emission in comparison to a reference Jet A-1. In order to use multiblends, they have to comply with the fuel specification ASTM D7655 and have to possess sufficient storage stability. This has been evaluated prior to the campaign to avoid biases of the experiment. The results of this study demonstrate the positive impacts of SAF application in a real airport environment.
Section snippets
Materials and methods
Fuels One reference Jet A-1 and two alternative jet fuel blends were tested on a lab-scale basis. Multiblend Jet A-1 was a ternary mixture of 30 %v/v HEFA (hydroprocessed esters and fatty acids) fuel, 8 %v/v ATJ (alcohol-to-jet) fuel and 62 %v/v reference Jet A-1. The second blend (Multiblend Jet A-1 + SIP) consisted of 17 %v/v HEFA, 3 %v/v ATJ, 75 %v/v Jet A-1 and 5 %v/v SIP (synthesized iso-paraffins). All fuels comply with the requirements of ASTM D7566-20b. The reference fuel used for
Fuel characterization and stability
Analysis results of Multiblend Jet A-1 and Multiblend Jet A-1 + SIP before and after storage are summarized in Table 4. The analysis of both multiblend mixtures confirmed that ASTM D7566-compliant fuels had been obtained. This demonstrates that on-spec, semi-synthetic fuel mixtures can readily be produced from several different synthetic fuels. The comparison of physico-chemical parameters before and after storage shows only variations within the range of the uncertainty of the applied test
Conclusions
The experiment demonstrated the successful application of a ternary alternative jet fuel blending practice. On-spec, semi-synthetic fuel mixtures can be produced from several different synthetic fuels and be stored over the period of 6 months without the deterioration of fuel quality. The tendency to form soot from the different fuels was predicted in a flow reactor experiment on lab-scale basis. The trend in soot emission, which follows the hydrogen content of the fuels, could be demonstrated
CRediT authorship contribution statement
Tobias Schripp: Conceptualization, Data curation, Formal analysis, original draft, Writing. Tobias Grein: Resources, Validation. Julia Zinsmeister: Data curation, Formal analysis, Visualization. Patrick Oßwald: Conceptualization, Formal analysis. Markus Köhler: Funding acquisition, Supervision. Franziska Müller-Langer: Project administration, Resources, Conceptualization. Stephanie Hauschild: Project administration, Resources, Conceptualization. Christian Marquardt: Data curation, Formal
Declaration of Competing Interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgements
The research and demonstration project on the use of renewable kerosene at Leipzig/Halle Airport (in short: DEMO-SPK) involved the collaboration of more than 20 international partners from industry and science. It was initiated as a model project of the Mobility and Fuel Strategy (MFS) and financed by the German Federal Ministry of Transport and Digital Infrastructure (BMVI). In addition to thanks to the whole project team, the authors are especially grateful for the support and effort of
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Current affiliation: Centre of Competence for Climate, Environment and Noise Protection in Aviation, Frankfurt am Main, Germany