(312d) Real-Time Monitoring of Supercritical Hydrocarbon Fuels

Jet fuel is used in high-performance aircraft as the primary heat sink, which causes chemical changes inflight that alters fuel properties and can affect flight performance. Trace species in the fuel can drastically change how the fuel reacts to the increased temperature and lead to deposition of solids, resulting in increased maintenance of aircraft components. As new, high-performance aircraft are developed and fuel is taken to higher temperatures (160 – 500 °C), real-time monitoring of fuel during flight and during system development is needed to better understand the fuel degradation process and enable reliable aircraft operation. At temperature and pressure, tracking of the trace components that cause bulk fuel degradation is challenging due to low concentrations and a constantly changing matrix. Mainstream Engineering has continued development of a Raman spectroscopic sensor that uses a fiber-coupled, in-line, flow cell capable of withstanding 550 °C and 3.8 MPa to measure fuel composition in real-time. The flow cell was used to obtain high-quality spectra of different fuels from room temperature up to 550 °C and calibrations were used to identify changing concentrations of fuel components. The system has been used to examine fuel degradation in the thermal oxidation regime (160 – 350 °C) and in supercritical fuel in the pyrolytic regime (350 – 550 °C). Method development and sensor performance from room temperature to 550 °C as validated with gas chromatography/mass spectrometry and 3D fluorescence spectroscopy will be presented.