In-Tank Optical Oxygen Sensor

Military and some commercial aircraft protect fuel tanks from explosion by reducing the gaseous oxygen (O2) content in the ullage headspace above the fuel from typical ambient levels of 21% to less than 9% via a process called inerting. To this end, engine compressor bleed air feeds an On-Board Inert Gas Generation System (OBIGGS) that supplies Nitrogen-Enriched-Air (NEA) to the ullage. The NEA O2 is usually measured prior to pumping it into the fuel tank. However, the ullage O2 content can fluctuate compared to the NEA, especially during rapid maneuvers or altitude changes, since the tank is vented to the external atmosphere. No sensor technology is presently able to monitor the O2 content of the ullage itself under the widely variable aircraft operating conditions. Therefore, reliable and accurate real-time sensors are needed. The sensors must be lightweight, compatible with fuel vapors and the aircraft electrical system, and low cost.  The project proposed herein, through Phase II, seeks to build upon prior foundations with innovations that simplify the design for manufacturability and ease of installation, and for eliminating supplemental measurement of temperature and pressure. The developed oxygen sensor system intends to achieve TRL8 upon completion of Phase II.