TECHNOLOGY AREAS: Air Platform, Materials/Processes, Biomedical, Human Systems

ACQUISITION PROGRAM: PMA-202 Aircrew Systems; PMA 257 AV-8B; PMA 265 F/A 18

OBJECTIVE: Eliminate carbon monoxide (CO) from oxygen breathing gas produced by the aircraft’s on-board oxygen generating system (OBOGS) during shipboard operations.

DESCRIPTION: Navy tactical aircraft operate in close proximity to one another during shipboard launch and recovery. During these operations, high levels of engine exhaust gases are ingested into the aircraft’s bleed air system which provides pressurized air to the OBOGS. The OBOGS uses pressure swing adsorption (PSA) to selectively remove nitrogen and other contaminates from a pressurized air source to provide oxygen enriched breathing gas to the pilot. Prolonged exposure to jet engine exhaust while sitting behind another aircraft waiting to take off and operating with low bleed air pressures can result in carbon monoxide (CO) breaking through the PSA unit’s molecular sieve beds and into the pilot’s breathing gas. A method of eliminating CO from the breathing gas while meeting the needs for low pressure operation is required. Preference will be given to solutions that can be adapted at the OBOGS component level rather than adding parts to the aircraft. The solution should not require routine servicing.

General OBOGS operating conditions to consider are as follows: 1) Bleed air flow into the OBOGS is approximately 1 pound-mass per minute which could include up to 120 parts per million by volume (ppmv) CO at pressures that ranges from 9 to 150 pounds per square inch, gage (PSIG). 2) OBOGS oxygen pressures supplied from the OBOGS PSA unit to the pilot’s breathing regulator ranges from 8 to 60 PSIG. Pressures downstream of the pilot’s breathing regulator are approximately atmospheric pressure. 3) Oxygen flow from the OBOGS to the pilot(s) ranges from 8 to 200 liters/minute at atmospheric pressure. 4) Atmospheric pressure ranges from sea level to 50,000 ft. 5) OBOGS breathing oxygen delivered to the pilot must contain less than 10 ppmv CO to comply with physiological safety requirements specified in reference (6) (threshold requirement). It is preferred to reduce CO levels to 5 ppmv or less (objective requirement). 6) The operating temperature of the OBOGS for this application can range from -40 deg F to +160 deg F (objective) and 0 deg F to +160 deg F (threshold). 7) Contamination of the OBOGS is primarily a ground based event that can include exposure to engine exhaust and CO for up to 60 minutes prior to take-off. 8) The pilot’s breathing oxygen must be at or below threshold (preferably objective) CO levels for the duration of the pre-flight, mission, and post-flight.

PHASE I: Develop an approach and method for eliminating CO (or oxidizing the CO to CO2) while meeting the performance and reliability requirements of the oxygen system. Develop the concept for aircraft integration. Provide preliminary performance data to verify the chosen method will eliminate or effectively oxidize the CO to CO2.

PHASE II: Optimize the method and develop a prototype for system and aircraft testing. Demonstrate the method developed in Phase I by integrating the solution into an OBOGS mock up.

PHASE III: Produce the components for incorporation in the aircraft or aircraft subcomponent.

PRIVATE SECTOR COMMERCIAL POTENTIAL/DUAL-USE APPLICATIONS: PSA based oxygen systems are being considered by commercial aviation. Traffic patterns for commercial aviation often result in aircraft lining up behind one another waiting to take off. Thus future commercial aircraft that use OBOGS will face the same issues and are potential candidates for this technology. The commercial aviation sector would benefit from an effective CO filter of OBOGS gas for crew and passenger safety.

A dual-use application includes CO elimination in point of use oxygen generating systems used by military mobile hospitals and civilian disaster / mass casualty response teams.

REFERENCES:
1. "Fundamentals of Aerospace Medicine", edited by Roy L. DeHart, Lea and Febiger, 1985.

2. "Aviation Medicine", Second Edition, Edited by Air Vice-Marshal John Ernsting and Air Vice-Marshal Peter King, Butterworth -Heinemann, Ltd, 1988.

3. "Gas Separation By Adsorption Processes", Ralph T. Yang, Imperial College Press, 1997.

4. "Pressure Swing Adsorption", Douglas Ruthven et. al, John Wiley and Sons, 1994.

5. General Description of OBOGS Aircraft Integration
"OBOGS and OBIGGS: The Application of Molecular Sieves to Aircrew Breathing and Aircraft Survivablity", Robert L. Cramer, Proceedings of the 19th Annual SAFE Symposium, 1981.

6. ASCC 61/101/10, "The Minimum Quality Requirement for On Board Generated Oxygen", Air Standardization Coordinating Committee Advisory Publication, 12 Feb 1988.

KEYWORDS: OBOGS; Breathing; Oxygen; Carbon monoxide(CO); Pressure Swing Adsorption (PSA); Engine Exhaust.

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