1997 Fiscal Year Final Research Report Summary
FLAME SPREAD OVER LIQUID FUELS AT GRAVITY AND MICRO-GRAVITY CONDITIONS
| Project/Area Number |
08044161
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| Research Category |
Grant-in-Aid for international Scientific Research
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| Allocation Type | Single-year Grants |
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| Section | Joint Research |
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| Research Field |
Thermal engineering
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| Research Institution | OITA UNIVERSITY |
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Principal Investigator |
ITO Akihiko OITA UNIVERSITY,FACULTY OF ENGINEERING,PRODUCTION SYSTEMS ENGINEERING,ASSOCIATE PROFESSOR, 工学部, 助教授 (30127972)
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| Co-Investigator(Kenkyū-buntansha) |
KONISHI Tadashi OITA NATIONAL COLLEGE OF TECHNOLOGY,ASSOCIATE PROFESSOR, 助教授 (00225468)
NARUMI Akira KANAGAWA INSTITUTE OF TECHNOLOGY,PROFESSOR, 教授 (50100764)
CREMERS Clif ケンタッキー大学, 工学部, 教授
SAITO Kozo UNIVERSITY OF KENTUCKY,MECHANICAL ENGINEERING,PROFESSOR, 工学部, 教授
CREMERS Clifford J. UNIVERSITY OF KENTUCKY,MECHANICAL ENGINEERING,PROFESSOR
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| Project Period (FY) |
1996 – 1997
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| Keywords | Combustion / Liquid fuel / Flame spread / Micro gravity / Surface tension flow / Bouyancy / Flash point / Fuel vapor concentration |
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| Research Abstract |
The phenomenon of flame spread over Liquid id of current interest because of its importance to fire safety and the curiosity of fundamental mechanism of the flame spread. To clarify the effects of gravity on flame spread the experimental research was excuted for measuring velocity, temperture and vapor concentration profies both in sub-flash and super-flash conditions using particle track laser sheet method, infrared thermography and dual-wave length holographic interferometry. These results were compaired with NASA's microgravity test conducted aboard a sounding rocket. Thefollowing conclusions are deduced ;
1. Two circulation cells exist in the sub-surface liquid just ahead of the flame leading edge in sub-flash conditions, which are mainly controlled by the thermocopillary force, whiele the buoyancy force secondarily effects to circulation growth and chenges the temperature field in the sub-suface liquid. the circulation cells have 3-dimensional structure.
2. The cold temperature zone
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exists in sub-surface liquid whose temperature is below flash point. The cold zone clearly obstruct crawing flame from shifting to jumping stage, because no substrantial fuel vapor is accumunilated ahead of flame leading edge. The jump phase occurs after the cold temperature valley disappears. The cold zone is derived by the interaction between the surface tension flow and buoyancy driven flow.
3. the infrared image revealed that the cold zone in mug conditions is much larger than that of 1g conditions. The surface temperature in the cold zone in mug is not beyond the flash point, so that the flame steadily spreads with no pulsating in mug conditions.
4. In gas-phase, two recirculation cells are created. One is formed in horizontal plane to the fuel surface, and the other is formed in vertical plane perpendicular to the fuel surface. Both circulation cells are formed when there is : (1) surface convection moving to the flame spread direction and (2) gas-phase convection in the free-stream air moving opposite to the flame spread direction. The recirculation cells contribute to make the flammable layr to be uniform.
5. Even with forced air flow of the sama order of magnitude as that induced naturally by buoyancy in lg, the mug flame spreads steadily and very slowly, which spead is about half that of 1g. The absence of liquid-phase buoyancy in mug leads to a very differnt liquid-phase surface temperature filed. Less
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