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Volume 43 (1995)
- Issue 1+2 Pages 1-
Volume 43, Issue 1+2
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Paper
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Katsumichi NITTA1995 Volume 43 Issue 1+2 Pages 1-9
Published: 1995
Released on J-STAGE: October 02, 2011
JOURNAL FREE ACCESSThis paper presents the characteristics of the compartment fire, especially the concentration of unburned decomposed gas, flowing out from a fire room at the ventilation control fire phase, which were investigated by the experimental study using a scale model. The experiment was conducted using an about 1/4 scale model of 600 width, 600 height and 1,200 depth constructed by 10 mm gypsum boards. The enclosure was set only one opening which is either vertically narrow or horizontally narrow with various sizes. PMMA plates or methanol in pan were burned at the center of the compartment. The concentration of hydrocarbon as an indicator of unburned gas and other terms such as ventilation rate, consumption rate of burning source and temperature field were measured.
The experimental results are summerized as follows. (1) As compared with liquid fuel, solid fuel like PMMA burned more slowly, of which consumption rate was proportioned to the square of time as the former being nearly constant. But in a compartment fire the relationship of burning rate with temperature, flow rate and gas concentration was not substantially different between both fuels except for their own material characteristics. (2) The consumption rate on the fuel control fire was nearly proportional to the opening factor and the rate on the ventilation control fire was larger than the value at free space burning condition for reasons of heat reception of fuel in room. (3) Though the unburned decomposed gas is essentially generated at the ventilation control fire, we can point out that the concentration was not monotonously inverse proportion to the opening factor and the maximum point of gas concentration was found in the ventilation control range near the border with fuel control range. (4) In case of vertically narrow opening such as 300 width and 100 height, fire characteristics were considerably changed with the disparity of the vertical position of the opening. The experimental evidences showed that it resulted from the change of in-flowing route of fresh air. In case of the opening touched with the floor, the out-flowing unburned gas became dangerously high concentration.View full abstractDownload PDF (713K) -
Masatomo YOSHIDA, Yoshinori OKAMURA, Shigeki TASAKA, Toshikatsu SHIMOD ...1995 Volume 43 Issue 1+2 Pages 11-20
Published: 1995
Released on J-STAGE: October 02, 2011
JOURNAL FREE ACCESSWhen fire-damaged Reinforced Concrete buildings are investigated, it is very important to evaluate maximum temperatures of concrete and steel in main structural parts and to diagnose the degree of damage to each member. This paper describes a new method to evaluate maximum temperatures during fire, utilizing the characteristic of an admixture responsive to thermal variations. Even if the quantity of admixture in concrete is small, its absorbance of ultraviolet rays can be measured with high accuracy because of its sensitivity. Concrete test samples were heated to every 100°C from normal temperature up to 600°C, and the absorption curves were obtained at each temperature. The relations between temperatures and absorbances were derived from the measured absorption curves, and showed almost linear relations. Therefore, it was found that maximum temperatures in concrete could be evaluated from absorbance measurements.
The validity of this evaluation method was verified by fire tests of a column and a floor. In the results, the evaluated values agreed with the ones measured by thermocouples. Moreover, the method was applied to various actual fires. In the results, it was found that the method could be applied to the fires and that the maximum temperatures in the concrete damaged by fire were accurately obtained by the method.View full abstractDownload PDF (738K) -
Yuichi WATANABE, Sanae MATUSHIMA, Tokiyoshi YAMADA1995 Volume 43 Issue 1+2 Pages 21-29
Published: 1995
Released on J-STAGE: October 02, 2011
JOURNAL FREE ACCESSIn order to evaluate the stack effect of the smoke shaft installed in a fire compartment, a series of experiments was conducted with a reduced scale model. Flow rate of exhaust gas through the shaft and smoke height in the compartment were measured. And these experimental data were compared with the predictions based on two layer zone model.
As a result, it was found that a certain adjusting parameter was required for prediction of smoke exhaust flow rate in order to predict experimental results with good accuracy. Because the smoke shaft exhausts fresh air of lower zone as well as smoke of upper layer, when the smoke layer thickness under the inlet of the shaft becomes thin.View full abstractDownload PDF (670K) -
Hiroshi HAYASAKA1995 Volume 43 Issue 1+2 Pages 31-39
Published: 1995
Released on J-STAGE: October 02, 2011
JOURNAL FREE ACCESSA new way of using thermography for radiative objects like pool flames is introduced and applied to small pool flames of three different fuels. Radiative characteristics and flame structure of small pool flames are considered by comparing flame temperature distribution from a radiation point of view. In addition, it was shown that pool flame structure of various fuels became more clear when the standard deviation and the coefficient of variation obtained from thermographic data were used. The discussion allows the following conclusions :
(1) Small pool flames tend to have a high radiance zone in the continuous flame region. This high radiance zone is important to sustain pool flames thermally.
(2) In addition to the high radiance zone of the continuous flame region, luminous flames of heptane and kerosene have an upper high radiance zone near the boundary of continuous and intermittent flame regions. When a mushroom flame cap is observed, it forms here.
(3) The non luminous flame of methanol does not have the upper high radiance zone because combustion of soot will not occur near the boundary of continuous and intermittent flame regions.
(4) The contours of standard deviation give us information about the flame edge and the vortex regions where mushroom flame cap is formed.
(5) The contours of the coefficient of variation identify the limits of the stable flame region.View full abstractDownload PDF (787K)
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