Investigation on Elastomer Compatibility with Alternative Aviation Fuels

The introduction of synthetic fuels produced from various alternative approaches has led to the concern over their compatibility with elastomeric seals used in current aircraft engines. The aim of this research is to investigate into this compatibility issue of alternative aviation fuels with typical elastomeric sealing materials. Experimental methodologies employed were the stress relaxation test (under both isothermal and temperature cycling conditions) and the Fourier Transform Infrared (FTIR) spectroscopy. A wide range of valuable data was collected and detailed analysis was carried out using statistical method and the Hansen Solubility Parameters (HSPs).

The outcome of this research establishes the fundamental stress relaxation characteristics of typical sealing materials in jet fuels produced via various sources. It demonstrates different impacts that individual fuel species may have on seals. A correlation has been found between the stress relaxation and the molecular structure changes of the O-rings. The HSP analysis suggests a good non-linear correlation between the equilibrium compression force and the RED number generated from the ‘triangle’ test data. It is proved that temperature is an influential factor in terms of the sealing performance of an O-ring. Generally, the stress relaxation process slows down (accelerates) as the temperature decreases (increases). At extremely low temperatures, seals become very inert and the relaxation process would stop. Temperature cycling tests show the relationship between seals’ ability to recovery from thermal contraction and the aromatic content in the fuel. Based on the knowledge gained here, recommendations have been given on the potential future work related to this topic.