Development and turbine engine testing of coconut oil-based biojet fuel

The increasing demand for sustainable aviation fuels, along with the need to decarbonize the aviation sector, has led to ongoing extensive research into renewable jet fuels. Despite notable progress, there remains a need to expand the range of feedstocks, optimize technological pathways, and scale up new fuel production. The authors propose developing novel biojet fuel in response to these challenges. The work presents complex research on the synthesis of renewable fuel components, the study of basic physical-chemical properties of new biojet fuel, and the assessment of gas turbine engine operation parameters to validate the hypothesis that this fuel can be used for jet engine propulsion with the required efficiency. Coconut oil ethyl esters (COEE) used as a renewable component were synthesized via esterification of coconut oil with ethanol and refined via vacuum distillation. The choice of the feedstock and production method allowed the production of a product with a high level of purity (97.4 %) of COEE, a light molecular weight composition (C6-C18) close to conventional jet fuel, and a low content of unsaturated fatty acids (below 5 %). The study of basic physical-chemical properties of biojet fuels containing traditional jet fuel and 10 %, 20 %, and 30 % of COEE demonstrated the rise of density by 1.01–2.53 %, viscosity by 9.79–32.26 %, freezing point by 10.34–33.51 %, and reduction of combustion heat by 1.69–5.07 %. Performance tests of a small gas turbine engine with conventional and biojet fuels demonstrated an overall stable engine start-up and operation. While no negative impact on operating parameters was found, the rise of the engine's specific fuel consumption was observed at all operation regimes: by 2.58 % 4.81 %, and 7.42 % for biojet fuel with 10 %, 20 %, and 30 % of COEE, respectively.