Online Spectroscopic Chemical Diagnostics for Thermally Stressed Fuel Flows

The limits of high-performance aircraft continue to be pushed, requiring more capacity from thermal management systems as hydraulic, mechanical, and pneumatic power systems are replaced with electrical components. Rejecting this heat to the fuel can lead to composition changes and the production of insolubles and surface deposits via pyrolysis and oxidation at elevated fuel temperatures, especially at walls and hot spots. As such, it is important to understand and monitor online the thermal degradation processes.A few trace compounds have been identified as critical in the thermal oxidative chemical process including hydroperoxides, reactive sulfur compounds, polar organic compounds, trace metals, and dissolved oxygen. Currently, there is no way to measure these compounds in real-time at aircraft-relevant conditions or determine the onset of thermal instability. Mainstream Engineering is developing a fuel composition monitor (FCM) that uses a spectroscopic approach to track changing fuel chemistry, including reactive sulfur compounds, polar organic compounds, aromatics, saturates, and olefins. Phase II will include testing a prototype demonstrator on the Advanced Reduced Scale Fuel System Simulator as well as development and execution of the technology transition strategy.