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Volume 40 (1990)
- Issue 2 Pages 37-
- Issue 1 Pages 1-
Volume 40, Issue 1
Displaying 1-4 of 4 articles from this issue
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Paper
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Kwang Ill KIM, Hideo OHTANI, Yoichi UEHARA1990 Volume 40 Issue 1 Pages 1-6
Published: 1990
Released on J-STAGE: January 10, 2012
JOURNAL FREE ACCESSIn order to investigate mechanisms of heat tranfer to the fuel surface burning in a compartment, an experimental study was conducted in a small scale compartment by using methanol as a fuel. The radiative heat transfer depends on ventilation parameter (A√H) in a compartment fire. The radiative heat feedback to fuel in a compartment is larger than that in an open air. The enhanced radiative heat feedback was considered to cause large burning rate of fuel in a compartment. Comparison between calculated and measured radiative heat fluxes showed a close relationship between them. The emissivity of burnt gas from methanol fire was estimated to be less than 0.05, so the burnt gas was considered to have little contribution to the radiative heat transfer.View full abstractDownload PDF (422K) -
Takashi ONO, Hiromitsu ISHII, Norio MUROI1990 Volume 40 Issue 1 Pages 7-17
Published: 1990
Released on J-STAGE: January 10, 2012
JOURNAL FREE ACCESSTo detect a fire in the early stage and eliminate false alarms, it is necessary to measure the physical and chemical phenomena of a fire continuously from an early stage and process the information obtained to make a fire judgment.
The authors have been studying a fire judgment system based on the three-dimensional information obtained from three kinds of analog sensors : temperature sensor, smoke sensor and CO gas sensor. This paper discusses a fire alarm system which uses a combination of both fire judgment with composite fire information and fire judgment with time-series fire information.
Fire judgment with composite fire information is a method to judge a fire using a three-dimensional coordinate space whose axes represent three kinds of analog sensor outputs. In this coordinate space, the position vector obtained by adding the vectors of the respective sensor outputs represents the environmental situation at that time. The fire judgment is made by forecasting whether or not the position vector will go out of the non-fire region predefined in the coordinate space. This fire judgement method has the advantage that the progression of a fire can be estimated overall with multiple kinds of information.
Fire judgment with time-series fire information is a method to judge a fire using the time-series information obtained from the sensor output. The fire judgment is made by forecasting the change of each sensor output and by judging whether or not the forecasted value will reach the predefined danger level. This fire judgment method has the advantage that the time elapsing to reach the danger level can be forecasted.
We have developed a fire alarm system using a combination of these two fire judgment methods. The fire alarm system is designed to is sue a fire alarm when both the time-series fire judgment system and the composite fire judgment system forecast that the current phenomena will reach a danger level, ensuring high reliability of fire judgment.
The fire alarm system responded well in the case of either a smoldering fire or a flaming fire in a compartment and did not issue any false alarms in several model experiments assuming non-fires.View full abstractDownload PDF (815K) -
Jianzhou WU, Yuji WADA, Toshio MATSUZAWA, Masamitsu TAMURA, Kamu KURAM ...1990 Volume 40 Issue 1 Pages 19-27
Published: 1990
Released on J-STAGE: January 10, 2012
JOURNAL FREE ACCESSHeat rate characteristics were examined for 4 pressure vessels and 3 heating furnaces of the pressure vessel test designted by the Fire Services Law. The heat rate of liquid silicon oil in the A1 cup can be kept 40°C/min by applying 70V electricity to the furnace and controlling the furnace temperature at 810°C. The standard deviation (σ) of the heating rate was 2.4°C/min for 15 experiments using 3 pressure vessels. No significant deffirences were observed among the vessels and the furnaces. The temperature differences between bottom and center of samples were about 20°C for silicon oil and 50°C for α-alumina powder, respectively.
Applying continuous electric current to the furnace, the experiments could not be carryed out under constant furnace temperature. It was also found that it was important to fix the position of thermocouples for controlling furnace temperature to keep constant.View full abstractDownload PDF (696K) -
Kimio SATO1990 Volume 40 Issue 1 Pages 29-35
Published: 1990
Released on J-STAGE: January 10, 2012
JOURNAL FREE ACCESSThis experiment is related to extinguishment of the liquefied gas fires by carbon dioxide and liquid nitrogen.
It was shown that the pool fires of liquefied gas be can extinguished as well as normal liquid pool fires.
The extinguishants were discharged by tank side method or by an over head method.
A fuel pan used was a square of 1 m2 made of SUS 304. Fuel used were liquefied natural gas, liquefied butane, and n-heptane.
The extinction time (te) became long as the discharg rate (q') became little. Then critical discharge rate (qc') can be taken as a point that it can not extinguish no longer. The relation between extinction time and the discharge rate is calculated by following equation.
te = − (V/Q) 1n (1 − qc'/q') (1)
Where Q is a assumed flow rate of air and V is a assumed volume to be extinguished.
The theoretical critical discharge rate is calclated by following equation.
qc' = CeQ / (1 − Ce) (2)
Where Ce is a flame extinguishing concentration.
If the critical discharge rate is calculated from eq. 2, it can estimate the relation of the discharge rate the extinction time by using eq. 1.
The calculations gave good agreement with the experimental data in case of tank side method, but disagreement with them in case of over head method.View full abstractDownload PDF (482K)
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