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Fiber Optic Oxygen Sensor for Fuel Tank Monitoring SBIR Contract # F33615-02-M-2248

Fiber Optic Oxygen Sensor for Fuel Tank Monitoring SBIR Contract # F33615-02-M-2248. Ocean Optics Dr. Mahmoud R. Shahriari Mike Morris Rob Waterbury Wingfu Yu ASF Kenneth Susko. http://www.oceanoptics.com. Significance of the Problem or Opportunity.

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Fiber Optic Oxygen Sensor for Fuel Tank Monitoring SBIR Contract # F33615-02-M-2248

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  1. Fiber Optic Oxygen Sensor for Fuel Tank MonitoringSBIR Contract #F33615-02-M-2248 Ocean Optics Dr. Mahmoud R. Shahriari Mike Morris Rob Waterbury Wingfu Yu ASF Kenneth Susko http://www.oceanoptics.com

  2. Significance of the Problem or Opportunity • Fuel tank explosions are potential hazards to any military or commercial aircraft. • FAA and NTSB have focused attention on the potential for explosion in the fuel tank. • On Board Inert Gas Generation System (OBIGGS) have been developed for some military aircraft and are under study for use in commercial aircraft. • The necessary technology to measure the Oxygen concentration in the fuel tank ullage during flight does not exist. • There is a need for a self-calibrating, flight worthy sensor capable of measuring Oxygen in real-time within the fuel tank.

  3. O2 T S S Flt. Data Recorder Cockpit Status Display Remote Locations (ie Cargo Holds) P Tank Vent L Fuel Tank N2 Fill Connection

  4. LOC Ignition Test IASFPWG – Seattle, WA 03-12-02

  5. LOC in Terms of Oxygen Partial Pressure Required

  6. Fuel Tank Environment • Parameter • Temperature -50 to + 50 oC • Total Pressure 2 PSIA to 2 ATM • Composition Fuel Vapor/Fuel Liquid/Air •  O2 levels 0.04 – 0.16 atmospheres (explosive range) • 0 – 0.4 atmospheres (operational range)

  7. General Requirements for O2 Sensor in Fuel Tank • Non-electrical, non-conductive • Operable in temperature, pressure and concentration range of fuel tank • Calibration free, self-diagnostic • Chemically, physically and functionally resistant to fuel liquid and vapor • Light in weight and small in size • Fast response – a few seconds • Moderate resolution and accuracy: 0.001- 0.005 atm O2 • Low power • Data must interface with aircraft automatic control systems. • Realistic cost of acquisition, installation and ownership.

  8. Proposed Solution: Optical Oxygen Sensor • Advantages compared to fuel cells and thermo chemical sensors • Works well with explosive environments because no current goes into sensor • Not contaminated by water • Immune to EMI • Low maintenance • Potential for Inherent Calibration • Specificity

  9. Core Cladding (Active layer) Light In Light Out Overcoating Fiber Optic Oxygen Sensor System Fiber Optical sensor Coupler Light Source Optical Detection System Electronics & Data Processing O2 soluble matrix fluorophore

  10. Foxy Fiber Optic Oxygen Sensor spectrometer

  11. Intensity Spectra and Quenching

  12. Pump pulse No quenching Intensity Quenching t3 t1 t2 Decay Time Measurement

  13. Sensor Response

  14. Jet Fuel Applications • Boeing & the FAA Evaluate Standard FOXY Sensors • Optical Signal Decreased upon Exposure to Fuel • Poor Signal Reproducibility During Thermal Cycling prevented temperature calibration • Ocean Optics Secures Phase I Project to Improve the Technology • Intensive Study of the causes of the signal degradation • Feasibility Testing of improved matrix chemistry • Feasibility Testing of advanced overcoatings • Feasibility Testing of Alternative Optoelectronics

  15. Sensor Chemical Modification • Modified the surface of sol-gel host matrix to exclude volatile hydrocarbons from sensor • Added singlet oxygen scavenger to our standard sol-gel formulation

  16. Effect of Chemical Modification on Sensor Degradation in Fuel Vapor Note: Samples were under CW excitation by blue LED

  17. Short Term Stability Excitation on Every Hour

  18. Accelerated Test (Constant Exposure)

  19. Adjusted Long Term Stability

  20. Environmental Chamber at ASF Used for Thermal and pressure Cycling and Calibration Studies

  21. Temperature Regulated Spectrometers and LEDS for Ultra Stable Intensity Measurements

  22. Temperature Cycle in Air Sensor Temperature Cycling

  23. Decay Time (t ) stability

  24. Sensor Stability in Fuel Liquid - Comparing the New Formulation to Standard Formulation Dynamic quenching by volatiles Standard Formulation

  25. Sensor Stability in Fuel Liquid - Comparing the New Formulation to Standard Formulation New Formulation

  26. Summary • Photo-bleaching seems to be the main component responsible for sensor photo-degradation. • Photo-bleaching is accelerated by fuel vapor and liquid by factor of 10. • Chemical modification of sensor is effective in reducing the photo-bleaching by a factor of 8. • Reducing the excitation energy density is effective in reducing the photo-bleaching rate.

  27. Phase I Accomplishments • Determined degradation is photo-bleaching • Discovered dynamic quenching of fluorescence by volatiles in fuel • Developed a sol-gel recipe that excludes fuel volatiles from sensor • Established that TRF detection is relatively immune to photobleaching, bending fibers and other sources of instability in intensity measurements.

  28. Phase II • Phase II Objectives • Develop robust probe • Develop TRF electronics • Develop flight - ready prototype system

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