Advancing bio-derived sustainable aviation fuels

Bio-derived sustainable aviation fuels (SAFs) can be produced by several different methods, each of which result in variations in the fuel’s final chemical composition, which subsequently affects all associated properties including thermal stability, combustion performance and emissions. It is therefore important to understand the impact different SAF production methods have on fuel properties.

When a fuel travels through a gas turbine’s fuel system, it picks up heat and as a result it changes chemically affecting its thermal stability via a process called thermal degradation. This can create problems such as the growth of deposits and bulk insolubles throughout the fuel system and injectors, having severe impact on the performance, efficiency and maintenance of an engine.

So far, the modelling of thermal degradation has relied on the use of chemical kinetic schemes that have been under development since the 1980s for fossil-based Jet A-1 and still requiring further development up to this day. Considering there are several production pathways for bio-derived SAFs, the development of chemical kinetic schemes for each of these becomes prohibitive. This project aims to solve this problem by developing a new modelling approach whereby simulation software for complex aviation fuel systems will be developed to utilise a ‘heat loading’ metric of the fuel that directly affects bulk insolubles concentrations. This will solve the issue of having to use chemical kinetic schemes for every SAF production method which is incredibly challenging and instead provides a much more efficient methodology that can be quickly applied for any current and future SAFs.

Beyond the development of thermal degradation simulation software for bio-derived SAFs, the combustion performance such as flame speed and emissions will be investigated numerically so that different bio-derived SAFs can be characterised. Fuel analysis using two-dimensional chromatography (GCxGC) will be carried out for bio-derived fuel samples so they can be used in laminar flame chemical kinetics modelling. This will enable the assessment of combustion properties such as flame speed and emissions and therefore provide significant insight that will help differentiating the performance of different bio-derived SAFs.

The two work streams will bring significant insight into the performance of bio-derived SAFs that can support the development of the new generation aero engines for running purely on such fuels. This work will also inform fuel producers and airlines on the performance of the bio-derived SAFs, therefore contributing towards the knowledge of which bio-derived fuel chemistries and production methods result in the highest performing fuels in terms of engine efficiency and combustion emissions.

This project is led by Spiridon Souris.