Understanding the Compositional Effects of SAFs on Combustion Intermediates

Abstract

This work analyses, experimentally and numerically, the combustion behavior of three aviation fuels: a standard Jet A-1, a high aromatic content fuel, and an isoparaffinic Alcohol to Jet (ATJ) fuel. The goal is to demonstrate the ability of a chemical kinetic model to capture the chemistry underlying the combustion behavior of a wide range of jet fuels, starting from compositional information. Real fuels containing up to hundreds of components are modeled as surrogates containing less than 10 components, which represent the chemical functionalities of the real fuel. By using an in-house numerical optimizer, the fuel components and their relative quantities are selected, and a semi-detailed kinetic model (containing about 450 species) is used to simulate the formation of the main oxidation products and reaction intermediates. Calculations are compared with species profiles measured in a laminar flow reactor to validate the model and provide insights into the reactivity of the fuels. Finally, starting from the results, general observations on the strengths and limits of the approach are provided, highlighting areas where further investigations are required.

Combustion, Chemistry, and Carbon Neutrality

“…Mehl et al recently (2022) discussed the influence of alternative jet fuel composition on combustion intermediates, relying on experiments, surrogates, semidetailed kinetic models, and optimization strategies, and pointed out that more validation is needed for certain compounds, including aromatic and naphthenic fuel fractions . Coupling fundamental-level results and approaches with observations from ground-based and flight experiments will further enhance the knowledge on such challenging, multicomponent targets as real aviation fuels and their emission behavior under practical conditions. , …”

“…533−535 Mehl et al recently (2022) discussed the influence of alternative jet fuel composition on combustion intermediates, relying on experiments, surrogates, semidetailed kinetic models, and optimization strategies, and pointed out that more validation is needed for certain compounds, including aromatic and naphthenic fuel fractions. 536 Coupling fundamental-level results and approaches with observations from ground-based and flight experiments will further enhance the knowledge on such challenging, multicomponent targets as real aviation fuels and their emission behavior under practical conditions. 517,537 Research needs include catalyst and reactor design as well as efficient process integration for upstream processes, 500,502,507,522 investigation of catalytic pathways for biomass-derived SAFs that may require less hydrogen, 507 but most prominently the evaluation of the properties and suitability of suggested fuel and fuel component candidates, including the needed physicochemical characteristics for international deployment as well as combustion and emission performance.…”

“…Characterization of the combustion behavior of SAFs on a fundamental level is receiving intense attention. Selected recent examples provide insight into combustion details for potential and existing SAFs, their comparison with those of conventional jet fuels, and efforts in the development of physico-chemically meaningful reaction models for these complex fuels. − One important issue is the emission of particulate matter by aircraft with its consequences on atmospheric reactions and radiative forcing, requiring a fundamental understanding of the relations between fuel composition, sooting tendency, and particle properties for alternative jet fuels and their blends. Tan et al (2022) have studied the soot formation propensity of direct blending of fossil jet fuel with oxygenated fuel components, considering this strategy as alternative to prior conversion of these oxygenates to hydrocarbons .…”

“…Overall, the observed and simulated soot volume fraction did not depend significantly on the respective fuels and their blends, with some differences noted in particle properties . Further investigation into the soot formation mechanism from SAFs under laboratory and engine conditions and related model development (Section ) is clearly warranted. − …”