STTR Phase I: Active Fiber Optic Sensor Array for Cryogenic Fuel Monitoring and Management

This Small Business Technology Transfer (STTR) Phase I proposal addresses key components for managing the liquid natural gas and hydrogen fuel supply economy. Transporting and storing cryogenic liquid fuels entails danger of fire and explosion. Since these fuel technologies are growing and acquiring increasing US strategic as well as worldwide importance, sensors and instrumentation to safely manage it are required. The outcome of this work will be a basic technology, first demonstrated at the University of Pittsburgh, consisting of active fiber optic sensors powered by in-fiber light, to measure cryogenic liquid level, temperature and hydrogen concentration in air. Such sensors can be multiplexed at multiple points on a single fiber. The sensors are fiber Bragg gratings (FBG), which produce a signal that is independent of optical intensity noise, electromagnetic interference, and are all-dielectric, avoiding the potential for electrical sparking. With the heating laser off, temperature can be accurately measured to detect liquid density stratification and other management problems. With the heating laser on, Bragg grating with functional coating can be used to measure the thermal conductance difference between cold liquids and gases for leveling sensing. Hydrogen is detected by the strain on the fiber induced by the absorption of hydrogen in a palladium film applied to the fiber at each Bragg grating. The palladium will be heated by the heating laser into a temperature range where it is most active even if it is near a cold pipe or vessel. If successful this technology will assist in providing security when transporting liquid natural gases. The safety of people and facilities are also great importance and impact. A bad accident could delay the wide adoption of hydrogen as a major fuel source. Having a flexible, multi-use system available that can be installed with absolute confidence to monitor and manage these fuels, as well as the health of installed systems, will have a major impact on the acceptance of hydrogen as a safe alternative fuel source. The ability to multiplex many sensors on a single fiber will enable safer and more economical penetrations in cryogenic walls and the low corrosion potential of the fibers will enable sensors to be placed along piping underground. The same basic active fiber sensor technology has the potential to be extended to fuel flow and other economically useful functions.