60093 - Reaction Model Development of Selected Aromatics as Relevant Molecules of a Kerosene Surrogate – the Importance of M-Xylene Within the Combustion of 1,3,5-Trimethylbenzene 

To reach the emissions reduction targets as defined in the Paris Agreement (UN, Paris 2015), different challenges need to be tackled in many sectors. In this regard, the aviation sector is challenged by the increasing air traffic expected over the next 20 years, as the number of passengers is expected to double (ACARE, 2017). As an important approach to reduce emissions, modern numerically aided designs of new gas turbine engines running on kerosene and on sustainable fuels are inevitable .Therefore, the aviation industry, is investigating the opportunities to achieve those targets. In order to facilitate the design process, the development of advanced software tools for the prediction of pollutant emissions, e.g., soot, besides others, in aero-engine combustors is playing a significant role. Such software development relies on a multidisciplinary approach based on chemical kinetics, CFD modeling, and experimental validation.

Jet A-1 is the most common fuel in aviation. Many efforts are undertaken on the development and improvement of accurate models for Jet A-1 combustion, including NOx and soot formation. Those models are also extended for alternative, sustainable fuels, which are allowed to be blended to Jet A-1 according to the respective specifications that are required to be matched.

In order to model Jet A-1 combustion, a detailed chemical kinetic mechanism is required. However, this fuel’s direct modeling is not possible due to its multi-species composition with up to hundreds of species and the extensive chemical reaction network needed. To this end, a common practice is a use of model fuel known as fuel surrogate. A surrogate is composed of a few hydrocarbons selected from the different chemical families, representing the major components of each chemical family and their fractions in a given fuel.

Recently the EU Horizon 2020 Clean Sky project ESTiMatE has proposed the formulation of a Jet A-1 surrogate with 1,3,5- trimethylbenzene selected to represent aromatics. Within ESTiMatE, a major goal is to achieve a deeper understanding of the combustion of Jet A-1 and of the soot formation and destruction network.

In the present work, a chemical kinetic mechanism is being developed for describing the 1,3,5-trimenthylbenzene combustion in a wide parameter range (temperature, pressure, and fuel-air ratio). The reaction sub-model is validated by experimental data taken from literature for ignition delay time (safety), laminar flame speed (heat release), and speciation data (soot precursor). A particular focus was set on the m-xylene sub model, which is an important part of the 1,3,5-trimenthylbenzene cause m-xylene is an important intermediate within the 1,3,5- trimethylbenzene oxidation. The performance of the developed reaction model is discussed in the present work.