Aviation Fuels with Improved Fire Safety A Proceedings (1997) / Chapter Skim
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Appendix B: New Concepts in Fuel Fire Research: Final Summary Report of Short-Term Advisory Services (STAS) Team
Appendix B: New Concepts in Fuel Fire Research: Final Summary Report of Short-Term Advisory Services (STAS) Team
Pages 125-140
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From page 125... ...
Appendix B New Concepts in Fuel Fire Research: Final Summary Report of Short-Term Advisory Services (STAB} Team Frederick L Dryer (Team :Leader)
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From page 126... ...
These approaches are all based on established technology, have significant fire AVIATION FUELS WITH IMPROVED FIRE SAFETY: A PROCEEDINGS hazard reduction potential, are compatible with the addition of other approaches which involve fuel modification, and do not result in (what appear to be ~ unacceptable performance or logistics penalties. With fuel cooling and suitable fuel systems modifications, conventional antimisting agents may have some potential for reducing aerosol formation, but again fundamental information to guide successful development is lacking.
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From page 127... ...
Finally, if neither the aerosol ignition nor flame ball size can be controlled, one must consider prevention of the ignition of the fuel pool spill, or the containment of the pool fire to a small area by limiting the region over which the fuel is spilled or the rate at which the flames spread over the fuel spill. The occurrence of these phenomena are inter-related through the actual fire scenario, the mechanical design of the vehicle, fuel storage, and fuel delivery systems, as well as through the physical and chemical properties of the fuel.
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From page 128... ...
Obviously, the minimum droplet size will be a complex function of the amount the liquid is subcooled below its flash temperature, etc., but unlike the case of low flash temperature fuels, aerosol flame ball development may be inhibited by controlling aerosol formation. Finally, the ignition of a pool spill will require heating of the pool surface to produce flammable conditions, and subsequently, ignition of this flammable mixture.
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From page 129... ...
In the case of low flash point fuels, aerosol drops already provide flammable vapor concentrations at the environmental temperature. Antimisting agents show no effect on flame propagation over fuel spills for either low or high flash temperature fuels once the pool fire is initiated.
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From page 131... ...
In fact, the lower the fuel circulation temperature is kept relative to the flash point, the stronger the ignition phenomena will have to be to initiate the flame ball, and the more intense the fireball must be to ignite a pool fire. Such fuel cooling will have little or no effect in terms of diesel engine performance or vehicle range.
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From page 132... ...
FRF-type blends containing 6 vol pet surfactant and between 2 and 10 vol pot water as micro-emulsions appear to behave similarly as far as liquid vapor pressure-temperature relationships are concerned, but a formulation containing 6 vol pet surfactant, 6 percent co-solvent to solvate the surfactant in aromatic diesel fuel, and 10 vol pot water was chosen A VIA TION FUELS WITH IMPROVED FIRE SAFE7 Y.: A PROCEEDINGS as the prototype FRF composition. These large amounts of materials added significant procurement costs, caused substantial deployment difficulties (since the material was to be prepared in forward supply areas)
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From page 133... ...
It appears that liquid/vapor interface dilution is itself a feasible technical approach which should be further considered before it is abandoned. Limited storage life and operating temperatures are compelling reasons for rejection of candidate systems, but the STAS team concluded that lower energy content and octane number of candidate mixtures have less serious impact.
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From page 134... ...
The STAS team is fully supportive of additional efforts to further evaluate such possibilities. If the fireball formation can be eliminated, one of the major sources of ignition for any fuel pool spill will have been removed.
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From page 135... ...
135 Gelling Agents Gelling agents were one of the earliest methods investigated by the Army for fuel fire hazard reduction. The basic premise of using gelling agents was to achieve performance similar to antimisting agents as well as contain the region of post-impact fuel spillage.
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From page 136... ...
The added use of conventional antimisting agents and fuel vapor interface dilution techniques require additional fundamental questions to be answered, as well as some vehicle design modifications, logistics decisions, and fuel cost procurement decisions to be made. In the case of antimisting agents, the minimum shear required to degrade the agent in comparison to shears experienced under ballistic impact needs to be quantified rather than qualitatively determined.
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From page 137... ...
It is neither useful nor realistic for DARCOM to state that any approach to reducing the fire hazard issue must: · not degrade performance, range in particular · not generate additional procurement cost · contribute significantly to fuel survivability · have worldwide use capability · be compatible with fuel handling and distribution systems Tests and quantitative definitions must be provided for such issues if a successful program is to result. For example, the STAS team consensus was that possibly a range degradation of 10 percent and a maximum power degradation of 5 percent might be accommodated, since these are comparable to effects derived from changes in altitude, alternate base fuels, temperature, etc.
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From page 138... ...
Based upon the emphasis of previous Army research programs on this subject, it is also likely that too little emphasis will be placed on obtaining such information from laboratory research prior to full scale systems and field tests in future programs. Recommended Additional Approaches On the basis of earlier discussions, this section briefly summarizes the STAS team consensus on other potential approaches to mitigating the fire hazard problem.
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From page 139... ...
Fuel cooling effects may also be synergistic with the addition of antimisting agents. With the system design modifications and fundamental questions answered which were mentioned above, the development of an antimisting fuel package in an intermediate time (5 to 8 years)
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From page 140... ...
Army Fuels & Lubricants Laboratory 8500 Culebra Road San Antonio, lax 78284
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