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Volume 27 (1977)
- Issue 2 Pages 27-
- Issue 1 Pages 1-
Volume 27, Issue 2
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Paper
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R. I. EMORI, K. SAITO1977 Volume 27 Issue 2 Pages 27-32
Published: 1977
Released on J-STAGE: January 29, 2013
JOURNAL FREE ACCESSBecause of the safety hazard and the difficulty of controlling boundary conditions in full scale experiments of tank fire, many model tests have been performed. This paper describes experimental verification of model rules on fire of liquid fuel in shallow oil pan. The model rules were obtained by “ law approach ” which calls for the physical interpretation of the phenomena to bring out the governing physical laws. Mechanical follow-up of the routine process leads to a contradictory and impracticable model rules. It was realized by a more subtle understanding of the phenomena that the geometrical shape of the flame at a certain instant and the temporal change of the shape are governed by two different sets of physical laws. As a result, two independent times could be assigned to the flame geometry and the temporal change of the flame, and the model rules became realizable. Fire experiments done by others were reviewed and the results were re-interpreted, all of which substantiated the model rules. Fire experiments of liquid fuel in three geometrically similar pans of diameters 0.3, 0.6 and 1.2 meters were performed with and without wind in a laboratory, and the results were compared with a fire experiment, which was published by others, of the same fuel in a pan of 10 meters in diameter. Results of these experiments also showed a remarkable similarity and the model rules seemed to be well verified.View full abstractDownload PDF (447K) -
T. HIRANO, T. KOSHIDA, K. AKITA1977 Volume 27 Issue 2 Pages 33-39
Published: 1977
Released on J-STAGE: January 29, 2013
JOURNAL FREE ACCESSThe mechanisms by which flames spread over flat surfaces of polymethylmethacrylate (PMMA) have been studied. Spread rates of vertically downward and hrizontally spreading flames were measured, and the gas velocity and temperature profiles near the spreading flames were examined using particle tracer techniques, fine wire thermocouples, and a Mach-Zender interferometer.
For PMMA sheets thinner than 0.2 cm, the spread rate was inversely proportional to the thickness, and for those thicker than 2.0 cm, it was independent of the thickness. The velocity profiles in front of the preheat zone resembled those across the boundary layer near a uniform temperature wall, while those in the preheat zone and pyrolysis zone resembled those across the boundary layer with a diffusion flame.
The temperature profiles indicated that the heat flux to the surface increased with the decrease of the distance from the pyrolysis front.
A brief theoretical analysis based on the experimental results indicated that when a buring sheet was thin, the heat flux through the gas phase into the solid phase in the preheat zone was much larger than that into the solid phase in the pyrolysis zone, while when a buring sheet was thick, this relation between the heat fluxes became reverse. If the former and latter cases can be classified as thermally thin and thick sheet burings, respectively, a PMMA sheet can be considered to be thermally thin or thick when its thickness is smaller than 0.2 cm or larger than 2.0 cm, respectively.View full abstractDownload PDF (540K) -
T. HAYASHI, M. SHIBATA, H. YAMAGUCHI, H. SAKURAI, K. KANEHARA1977 Volume 27 Issue 2 Pages 41-48
Published: 1977
Released on J-STAGE: January 29, 2013
JOURNAL FREE ACCESSSo far, a single air shutter for fire protection has been studied for shutting off flame and smoke flowing through a corridor at a fire, and follows have been described in the preceding reports.
(1) The significance of an air shutter for fire protection and the economical method for its design (Report 1)
(2) The smoke leak ratio and the permissible time to take refuge safely (Report 2)
(3) The influence of side flow, out side disturbing flow to air shutter, which has ununiform velocity distribution on the air shutter flow (Report 3)
Now, as shown in the Report 1, the more the air shutters are installed at a corridor, the less the area of danger zone caused by a fire becomes, and the easier escapers can take refuge to the safety zone.
From the above, it is necessary to know the characteristics of push-pull flows of a plural type air shutter installed in a limited space as a corridor or a passage way.
Then, to begin with, the static pressure at the space among two air shutters is investigated experimentally with variation of the ratios of flow rate from the sorroundings, Q2, to the one from the push opening, Q1, and of the size ratios of the air shutter. As the result, it becomes clear that the static pressure at the inner space is negative and distributes uniformly. Furthemore, using Euler's number defined by dividing the static pressure by the dynamic pressure at the push opening, the Euler's number depends only flow ratio, Q2/Q1, and the ratio of distance, H/E, between push and pull opening to width of push opening. In the range of practical use of two air shutters (2.0 ≦ H/E ≦ 5.0, 2.0 ≦ Q2/Q1 ≦ 7.0), the relation between Euler's number, Eu , and H/E and Q2/Q1 can be expressed as following experimental equations.
(1) When the both external sides of two air shutters are open to the atomosphere.
Eu = 2.2(H/E )-2.0 (Q2/Q1)1.7 (1)
(2) When one of the sides is close.
Eu = 8.8(H/E )-2.0 (Q2/Q1)1.7 (2)
From the above equations, the static pressure at the space shut in a practical two air shutters can be estimated when the values of H/E, Q2/Q1 and the push flow velocity, υ1, are given.
In addition, the relation between the fact that the static pressure rises caused by thermal expantion of air at a practical fire and the negative static pressure caused by the two air shutters is referred to.View full abstractDownload PDF (595K)
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