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Volume 34 (1984)
- Issue 2 Pages 25-
- Issue 1 Pages 1-
Volume 34, Issue 1
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Satoshi TAKAHASHI1984 Volume 34 Issue 1 Pages 1-5
Published: 1984
Released on J-STAGE: July 04, 2012
JOURNAL FREE ACCESSExtinction of a compartment fire is attended with difficulties especially when the compartment interior is wooden and its scale becomes larger. These troubles are brought because the wetted area dries up under intense radiation from the surroundings and reignites with the move of the spray nozzle. Therefore, the extinction of the whole body is thought to be achieved in the dynamism of local suppression speed and reignition speed.
The author formerly gave equation which describes the ignition time of the wet wood ember. Using this equation, dynamic equation was composed for model fires. That is, the fundamental condition for the extinction is given by,
Reignition time ≧ Sweeping time of the whole body
The necessary water application rate, W, quantity of water required, Me, and necessary density of the soaked water, x, are calculated as a function of room size and fire temperature, and compared with actual experience as well as experimental data. The theoretically derived curve not only agreed well with the experiment, but also could explain generally recognized requirements of the water application.View full abstractDownload PDF (362K) -
Ryoya KITAHARA, Minoru UMEZU1984 Volume 34 Issue 1 Pages 7-15
Published: 1984
Released on J-STAGE: July 04, 2012
JOURNAL FREE ACCESSThe aim of this investigation is to give a description of the flow behaviors of a stratified layer beneath the ceiling associated with tunnel fires.
This paper deals with the experimental results on the hot-layer movement in the full-scale and model tunnels which were closed at one end and completely open at the other. The fire sources in these tests were an alcohol pan on the floor near the closed end. The heat output was maintained for a period of about 8 min., during which time approximately constant heat-release rate conditions prevailed. Temperature and velocity distributions were measured at several locations of the tunnel during the steady burning period of the fire. The influence of forced ventilation on the hot-layer was also studied in the full-scale.
Following results were obtained;
(1) Hot-layer depth defined as the observed flow thickness was retained to be equal to the open end.
(2) Temperature and steady travelling velocity of the hot-layer decreased exponentially with distance from fire source respectively.
(3) The vertical temperature and velocity profiles showed a remarkable simularity between the full-scale and model experiments respectively.View full abstractDownload PDF (665K) -
Tadahiro YAMAMOTO, Masato ASO, Toshiaki SHIMIZU1984 Volume 34 Issue 1 Pages 17-23
Published: 1984
Released on J-STAGE: July 04, 2012
JOURNAL FREE ACCESSIt is well known that on addition of water onto a large amount of quick lime an exothermic reaction occurs and accumulated energy brings about a fire. However, even a small amount of desiccant for foods (about 110 g) brought about a fire in Himeji City of Hyogo Prefecture last year.
Authors had interest in the fire caused by a desiccant and tried 47 ignition tests using desiccant (I) and quick lime in technical grades (II). The tests were carried out under conditions like the fire: Package of (I) or (II) was placed in sugar can (200 φ × 270 H) filled with a large volume of newspapers and tissue papers. Water was dropped into the opened package.
1) In 33 ignition tests for (II), ignition occurred 8 times and smoldering 10 times. The shortest time reached to ignition was 40 minutes and 34.6 ml of water was dropped for this period. The longest time was 90 minutes and 60 ml was dropped. When water was dropped at the rate of 0.5 - 0.9 ml/min in the range of these times and water amounts, the possibility reached to the ignition was high.
2) In 14 ignition tests for (I), smoldering occurred 4 times and smoke filled inner parts of the can. In the case of (I) having low calorific values such as less than 4 kcal/mol, smoke did not occur and the temperature did not rise to over than 200 °C.
3) Calorific values of (I) with water were 5 - 6 kcal/mol in average and less than 1/2 as compared to those of quick lime in 100% purity (determined value, 14.6) and in technical grades (11.9). The lowest one was 3.3 kcal/mol.
4) When the package included desiccant was immersed in water for 2 hours, about 70% of initial weight increased. The packing paper can pass fairly large amounts of water.View full abstractDownload PDF (690K)
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