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Volume 31 (1981)
- Issue 2 Pages 31-
- Issue 1 Pages 1-
Volume 31, Issue 2
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Hiroshi OOUCHI, Masakazu SAKAKIDA, Tadao YOSHIDA1981 Volume 31 Issue 2 Pages 31-37
Published: 1981
Released on J-STAGE: November 26, 2012
JOURNAL FREE ACCESSThe hypergolic ignition of oxidizing agents with ethyleneglycol has been examined using a modified steel dish tester. 42 oxidants were selected from those which were known to be distributed in Tokyo district. Experiements of three types were carried out stepwise: contact of 2.5g each of two chemicals at room temperature (I) and at 100°C (II), and contact of 98% H2SO4 (5g) with the most exothermic binary mixture (10g) (III). Results were listed in tables and some comments were added.
The contact of ethyleneglycol with CrO3, KMnO4 or Na2O2 caused spontaneous ignition at room temperature. A bleaching agent containing calcium hypochlorite did not ignite on contact with the glycol at room temperature but a temperature rise was observed. 500g each of these chemicals ignited after about 30 seconds from the contact with each other at room temperature.
At 100°C, UO2 (NO3)2 NaClO2, AgClO3 and (NH4)2CrO7 gave the hypergolic ignition and other 19 oxidizing agents showed exothermic reactions on contact with the glycol.
The binary mixture of the glycol with the salts of chlorate, chlorite and hypochlorite and BaO2 ignited on contact with 98% H2SO4. Sodium and potassium bromate did not ignite but fumed smokes in this experiments. However, bromates are known to ignite on contact with strong mineral acids in the larger scale experiment.View full abstractDownload PDF (587K) -
Y. HASEMI1981 Volume 31 Issue 2 Pages 39-47
Published: 1981
Released on J-STAGE: November 26, 2012
JOURNAL FREE ACCESSA model to predict deterministic properties of the intermittent flaming region of upward current above diffusion flames is proposed. This model is basically founded on the dimensional relationships derived by McCaffrey and Cox-Chitty and the analytical solution of axisymmetric plume equations with uniform diffusivity. Using the eddy diffusivity estimated as K ≈ 0.0025Q3/5 [m2/s] with heat input Q in the units of kW from the dimensional analysis on theoretical and experimental plume characteristics, vertical velocity and excess temperature in this region are modelled as follows:
w ≈ √gβ/0.005πCΡρ · Q1/5/(η+1)2 , θ ≈ Q2/5/0.0075πCΡρz (η+1)3 , η = r2/xz , x ≈ 0.00212Q2/5√πCΡρ/gβ
Diagrams to calculate some useful properties such as mass flux and entrainment coefficient are also prepared. These results are applicable to methanol pool fire and natural gas fire, but they may not be applicable to the fuels that generate a flame whose height or shape is much different from that of above fuels.View full abstractDownload PDF (634K) -
Hisahiro TAKEDA, Takashi KAWAGUCHI, Kazuo AKITA1981 Volume 31 Issue 2 Pages 49-54
Published: 1981
Released on J-STAGE: November 26, 2012
JOURNAL FREE ACCESSUnstable behavior was investigated in liquid fuel compartment fires in order to research the critical phenomenon which appeared at the boundary between the stable and unstable fires. Four compartments were used in this study; an internal dimension of each size was 0.4m, 0.5m, 0.6m and 0.7m. Burning rate and extinction time were measured as a function of compartment size and ventilation parameter A√H, where A is the area of ventilation opening and H is its height. The influences of the compartment size and the fuel tray size on the fire behavior were especially investigared.
Two kinds of unstable behaviors were observed. One was in the small A√H region, where the flame could not spread over all the fuel surface for the insufficient air supply through the ventilation opening. The flame moved around slowly on the fuel surface and went out a few minutes after. The other was in the base of unstable oscillation. Oscillatory combustion began within a few minutes after ignition, and both the burning rate and the intensity of this oscillation were gradually increasing with time. But the sudden extinction occurred after 20 ∼ 80 minutes.
The former was independent on the compartment size and dependent only on the ventilation parameter. On the other hand, the latter was strongly dependent on the compartment size, implying that the unstable oscillation was ascribed to the correlation between the compartment size and the fuel tray size. The region of each fire behavior was clearly defined in this paper.View full abstractDownload PDF (443K) -
Hajime KIDA1981 Volume 31 Issue 2 Pages 55-61
Published: 1981
Released on J-STAGE: November 26, 2012
JOURNAL FREE ACCESSThe fluctuation of the time to extinguish the flame of burning gas oil in a fire pan with multipurpose dry powder extinguishing agent was studied.
A series of extinguishing experiments were carried out under nominally same experimental conditions.
Resulting frequency distribution of the time to extinguish the flame showed relatively wide scatter and unsymmetrical shape.
The time dependancy of the proportion of the cases in which flame extinction at time interval Δt following time t to the cases in which extinction did not occur before time t was small. (The start of discharge of powder was taken as t=0.)
This characteristics may be explained from the assumption that gradual accumulation of the powder in the flame is small and the powder discharged in the very short period prior to extinction have major effect to the extinction.View full abstractDownload PDF (555K) -
Ichiroh NAKAYA, Kazuo AKITA1981 Volume 31 Issue 2 Pages 63-68
Published: 1981
Released on J-STAGE: November 26, 2012
JOURNAL FREE ACCESSFor more exact evaluation of the radiative heat flux from burned gas in a room under fully developed fire conditions, experiments were conducted in a small scale room model. The gas temperature in the model was measured using a fine thermocouple and was theoretically corrected to compensate the delay due to thermal inertia. The amounts of the radiative fluxes, k(T)4 based on the average of the fourth power of the real temperature and kT4 on the fourth power of the average temperature were evaluated respectively, and the ratio, (kT4/(k(T)4) was estimated. The estimated ratio was mostly 1.1-1.3 with 1.7 at the maximum. This fact suggests that the effects of temperature fluctuations play an important role in causing the difference between these heat fluxes.View full abstractDownload PDF (455K)
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