実大廊下における火災気流の熱流動性状（I）（実験および実験結果の考察）
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The time-dependent behaviours of the shallow flow of hot fire products were studied by using the full scale corridors of different size (A: 13 m(L) × 1.5 m(B) × 2.5 m(H), B: 70 m(L) × 3.3 m(B) × 1.8 m(H)) and by taking the wood cribs as the model fire source. Those cribs were placed at the end of both corridors and were ignited by a small pilot-flame at the center of their bottoms to obtain the similarity for the growth of flame. The weight and maximum burning rate of the cribs were 5 kg and 20 kg, 5 g/sec and 20 g/sec for A and B corridor respectively. The smoke concentration (Cs) was defined by the turbidity in unit of 1/m. The gas concentrations were represented by the output of the gas-sensor (Cg) in unit of mV which were feasibly replaced by [CO] in the combustion gases in terms of the calibration curve. By taking CO as a labelled gas, the concentration of CO2 were estimated from Cg on the basis of [CO]/[CO2] at the fire source which were obtained the high precision I. R. measurement. The origin for the horizontal flow corresponding to the point of the hydraulic jump was determined by the break of the logarithmic plots of T/Too vs. travelling distance, where Too was the temperature at the surface of the crib and T meant those along the center of the fire plume or those at 10 cm beneath the ceiling of the corridor. As results, starting position (X=0) was taken at 2.5 m apart from the center of the crib for B corridor. Then, cartesian co-ordinates (x, y) were taken with abcissa along the corridor and aforesaid starting position at origin and with ordinate to vertical direction (y=0 on the ceiling). Following results were obtained; (1) Relations in the equation (1) and (2) were obtained at and around the fire source among Tavf-, Tavo- and Vavo- irrespective of time, (Tav0 − TR )/(Tavf − TR ) = 0.2 (1)Vav0 / √(Tavf − TR ) − Tc = 0.03 (2)where Tavo-, Tavf-, Tav-and TR-meant the height-average temperature of the fire plume, thickness-averaged temperature of the flow at X=0, the critical temperature for the efflux motion and the ambient temperature, respectively. Vavo- was the thickness-averaged velocity at X=0. (2) The constancy of the flow thickness (δv) of ca. 0.2 m at X=0 and of ca. 0.3 m at arbitrary X (X—35 m) after the ignition). was observed vs. time before the flow reached to the opposite end of the closed B corriodr (7min. after the ignition). (3) Disymmetrical triangular-shaped profile was obtained for Y-distribution of velocity. However, top-hat like profile tailing exponentially toward the floor was observed for the temperature. (4) It was estimated that the flow was relatively shallow on the base of equation (3). B δυ/(B +2δυ) ≈ 0.2 (3)(5) Exponential decrease of V and T at arbitrary y within δυ and of Cg at y=0.1 m were obtained along the corridor direction respectively. (6) The flow behaviour of quantity along the corridor was discussed in terms of Y-averaged quantity which was defined by following equation. Aav (X, t ) = 1⁄δυ ∫δυ0 A (X, y, t )dy (4)However, the stretcl-out of Cs-concentration terrace was observed vs. X itinerantly with time before 7 min. and the obvious accumulation of smoke around X=35 m was recognized after 7 min.
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