Real-time Spectroscopic Chemical Diagnostics for Hypersonic Propulsion Systems

Hypersonic aircraft powered by scramjets are the future, but face incredible technical challenges. Hydrocarbon-fueled scramjets must use only the fuel supply as a heat sink, causing a cascade of chemical changes that alter the properties of the fuel throughout the flight. Designing new and improved scramjets requires accurate information of how the fuel changes to determine the impact on heat exchangers and aircraft systems. Components are currently tested by preheating fuel to scramjet conditions where the fuel is supercritical at up to 1300 °F and 1200 psia. Due to these extreme conditions, fuel cracking and decomposition is not monitored in real-time, but a small amount of fuel is periodically collected in a sampling tube for offline analysis. This leads to misleading and delayed results as the fuel cools off and continues to change. Mainstream Engineering proposes a spectroscopic approach to determine real-time fuel decomposition in-line while in the supercritical state.