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Volume 41 (1992)
- Issue 2 Pages 41-
- Issue 1 Pages 1-
Volume 41, Issue 1
Displaying 1-4 of 4 articles from this issue
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Paper
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Yasushi OKA, Osami SUGAWA, Hiroomi SATO1992 Volume 41 Issue 1 Pages 1-8
Published: 1992
Released on J-STAGE: January 10, 2012
JOURNAL FREE ACCESSExperimental study on merged flame and plume was performed to clarify the fire plume merging phenomena and its behavior above two rectangular burners in parallel configuration. Measurements of temperature, upward velocity and CO2 concentration along the vertical centerline between burners were conducted by means of thermocouples, bidirectional tubes, and non-dispersed gas analyzer. Visible merged or inclined flame height was also measured by means of a video camera.
Two types of rectangular diffusion burners, the aspect ratio of which were 1:20 and 1:40 respectively, were employed in this study. These rectangular burners were placed in a quiescent atmospher, the separation distance between the burners varying from 0.05 to 0.30 m. Propane gas was used as a fuel and the heat release rate per unit was changed, ranging from 9.5 to 57.0 kW/m.
Fire plumes above each rectangular diffusion burner in parallel configuration merged above the centerline between burners, and formed a single merged plume in a higher region. The height at which the plumes started to merge was a function of the separation distance of two rectangular burners, being independent on the heat release rate. The height at which merging occurred could be deduced by separation distance. Moreover, the decaying slope for excess temperature and upward velocity behavior along the centerline between burners of the merged plume showed the same properties as a line fire source.View full abstractDownload PDF (651K) -
T. MORIKAWA, E. YANAI, T. OKADA, M. KAJIWARA, K. SATO1992 Volume 41 Issue 1 Pages 9-19
Published: 1992
Released on J-STAGE: January 10, 2012
JOURNAL FREE ACCESSFive different fire retarded building materials, plywood, polyisocyanurate foam boards, polyvinylchloride foam boards, polystyrene foam boards and phenolic foam boards, were combusted one after another together with non-fire retarded materials in one of the 1st floor rooms of a fire resistant 2 story-house in order to evaluate the toxic effects of fire effluents from full-scale fires involving fire retarded materials.
The results are summerized as follow.
1) The fires involving polystyrene foam boards and phenolic foam boards had much lower heat release rates and toxicity of gases than those involving others materials, although the polystyrene which melted and dripped on the floor would have burned if the amounts of non-fire retarded materials were greater.
2) In preliminary fire experiments it was found that mere 40 kg of non-fire retarded materials and no building materials in a room of 10 m2 was large enough to kill animals (rabbits) exposed to the gases in the room upstairs whose opening was only 1 cm wide and 195 cm high.
3) HCN was considered to be the main cause to death of animals exposed to fire gases whenever the death occurred, because in such cases HCN concentration was detected and COHb saturation in blood was lower than 30%.
4) The times to incapacitation calculated based on FED model with HCN and CO as toxicants had relatively good agreements with those obtained in fire experiments.View full abstractDownload PDF (741K) -
Satoshi TAKAHASHI1992 Volume 41 Issue 1 Pages 21-28
Published: 1992
Released on J-STAGE: January 10, 2012
JOURNAL FREE ACCESSThe effects of accumulation of solid fuels on extinguishment by inerted air with CO2 was investigated in this study. It is commonly known that the extinguishment of stack solid fuel fires used to be very difficult. This difficulty seems to arise not just from geometric reason which prevents reaching extinguishant, but from intense heat stored inside the fuel array. The author have firstly performed extinguishment tests of plastic crib fires and wood crib fires with portable CO2 extinguisher and obtained the order of relative easiness of extinguishment. Secondly, the minimum oxygen concentration [O2] which can sustain combustion, in another word, which can extinguish flaming combustion, when plural number of burning-plastic rods and wood sticks were submerged into the inerted air stream, were measured. The measured oxygen concentration clearly decreased as the number of rods were increased. These two experiments were compared, but good correlations did not hold unless [O2] were very small or large.
POM was a unique material and the author never succeeded in extinguishment with portable CO2 extinguisher. PU, PC and PF were relatively easy materials to do. Some reasons were also considered. For instance, the raw material for POM is CH2O and (CH2)2O and they have wide range of combustion. If the pylolysis gives them or some close materials, then the pylolysis gas must be easy to burn even under lower [O2]. In case of solid PU, the extinguishment was extremely easy even though [O2] & OI was not so unique. This matererial drips waterly melt material violently, thus seems to remove the heat on to the surface. This must be making extinguishment very easy.View full abstractDownload PDF (691K) -
T. NAKAJIMA, I. MIYAGAWA1992 Volume 41 Issue 1 Pages 29-40
Published: 1992
Released on J-STAGE: January 10, 2012
JOURNAL FREE ACCESSSemiconductor gas sensors are said to lack the ability to discriminate among gas kinds, and consequently, it is regarded quite difficult for a single gas sensor unit to discriminate among different gas kinds.
Therefore, when a semiconductor gas sensor is used with a gas leak alarm, gas containing alcohol causes a false alarm.
In order to improve gas-kind discrimination, it is necessary to use several semiconductor gas sensor units, each sensing different kinds of gas.
As for single-component gases, discrimination is enabled by processing the output voltage of these sensor units. However, an effective method for discriminating among mixed gas kinds containing alcohol, such as between one gas containing alcohol and methane and another alcohol and propane, has not been established yet. This is because alcohol has a higher sensitivity than methane or propane; a mixed gas containing alcohol shows characteristics similar to that of single-component alcohol gases.
In this paper, we explain a method that compare the differences of the characteristics curves of various mixed gas kinds. The characteristics curves is the output voltage of the semiconductor gas sensor by control of the heater voltage of the sensor. Even mixed gases that contain the same gas components, the characteristics curves of mixed gases varies with the mixture ratio. Thus, by processing several patterns, discrimination becomes possible.
Furthermore, when comparing the characteristics curves of mixed gases that resemble each other, e. g., one containing alcohol and methane and another alcohol and propane, we have worked out a method to enlarge the distinctive portions of the characteristics curves in order to define the gas kind. As a result, this discrimination method has been successful and is highly reliable.View full abstractDownload PDF (940K)
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