巻号一覧
28 巻 (1978)
- 2 号 p. 21-
- 1 号 p. 1-
28 巻, 2 号
選択された号の論文の3件中1～3を表示しています
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論文
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半田 隆, 浜田 俊孝, 須川 修身, 秋山 忠, 金子 和人1978 年 28 巻 2 号 p. 21-29
発行日: 1978年
公開日: 2013/01/11
ジャーナル フリーThe present study is primarily to pursue the analysis on the experimental results of the preceding study (Part I)1) for the motion and thermal behaviours of the relatively shallow flow of fire products along the ceiling in the full scale corridor.
In so far as y -profiles of the velocity and temperature concerned, approximately the same patterns were obtained among their normalized form (V/V max, T/T max or θ/θ max) respectively, when the flow was fully developed. On the other hand, in so far as the optical smoke density CS and gas concentration CG , their y -profiles were tailed as compared to those of the velocity and the temperature especially far from the fire source.
The y -averaged velocity Vav and temperature Tav decreased exponentially along the corridor and the modes of their changes were expressed as followings on the basis of the reduced-time on time parameter τ ;
ln (Vav/V0) = −KV · x/δV , (1)
ln (Tav/Tav0) = −KT · x/δV , (2)
where Vav0 and Tav0 was the average velocity and temperature at x = 0 and t = τ (t : time) respectively. δV was the observed flow thickness and were retained to be equal until the flow front reached to the opposite end of the corridor. KV and KT were the reduced time (τ) dependent attenuation coefficient for the velocity and temperature. The value of ratio KV /KT was found to be conserved as equal to 1/2.
In the initial stage of burning, y -averaged gas concentration CavG decreased exponentially along the corridor. However, as the stratification of the flow was developed, CG became constant excluding the front part of the flow where the exponential decrease were still recognized and therefore illustrated terrace along the corridor.
The distribution of the averaged smoke density CavS along the corridor showed a different pattern. The obvious accumulation of the smoke at and around the x = 35 m was observed 8 min when the flow front reached to the opposite closed end of the corridor.
The mean radius and the number of the smoke particles was found to be comparatively small, so its contribution to Δρ/ρ in estimating ∂ρ/∂y could be neglected. Therefore the hydrodynamic stability of the flow could be discussed in terms of the Richardson number on the basis of the temperature and were estimated from the y -temperature and y -velocity profile.
The effective diffusion coefficient for momentum (Km ) and for heat (Kh ) were also discussed with Richardson number (RiT ) on the hydrodynamic stability of the flow. Km and Kh were reduced vs.
RiT from ca. 2.8 × 10-4 to 1.0 × 10-4 (m2/sec) for Km and from 4 × 10-4 to 0.2 × 10-4 (m2/sec) for Kh respectively regarding the increase of RiT from ca. 0.5 to 1.2.
The contribution of smoke particles on the stability of the flow was also discussed regarding the particle size and concentration of the smoke (DVSav = 0.5μ , N = 2.4 × 1012/m3) in the present flow was obtained by unpolarized He-Ne laser.抄録全体を表示PDF形式でダウンロード (692K) -
半田 隆, 浜田 俊孝, 深谷 博, 須川 修身, 金子 和人, 古川 義男, 遠藤 弘1978 年 28 巻 2 号 p. 31-38
発行日: 1978年
公開日: 2013/01/11
ジャーナル フリーThe function time and performance pattern of various types of detectors (e.g. ionization smoke detector, rate-of-rise detector, heat detector, gas detector etc.) was pursued individually in full scale corridor and compartment vs. the flow of fire-products evolved from the miscellaneous fire source (i.e. paper, wool, wood and their mixture including some amount of plastics).
Each detector worked correctly when the stratification of the fire-products flow was developed.
Breaking point was obtained in the output-time curve of each detector corresponding to the time of the successive and itinerant stratification of the flow through the corridor and in the compartment, respectively. These points defined as each detector's correct function-time and were exactly corresponded with the breaking points in the burning rate-time curves of miscellaneous fire source on reduced time base using time parameter.
Following results were obtained :
(1) Gas and smoke which were included in the flow head were found to be the ones drifting around the fire source which had been produced during the very earlier stage of the combustion.
(2) The value V/√θ and V/Q1⁄3 was individually retained for those in the head and core of the flow of fire-products on real time bases.
(3) The gas and smoke detector indicated a quicker response than the heat detector when placed on the same position far from the flaming fire source. However, they worked simultaneously when placed near the flaming fire source.
(4) Breaking point-time in the correlation plots of gas output voltage vs. smoke optical density of the two-element detector which were obtained itinerantly through the corridor and in the compartment were found to be coincident with the breaking point-time in the Rb -time curve on reduced time basis, where Rb was the rate of burning.
(5) The aforementioned breaking point time was also coincident with time when the stratification of the flow was established.
(6) Pre-alarm level (optical smoke density: CS = 0.1m-1, output voltage of gas detector: CG = 50mV) and alarm level (CS = 0.1m-1, CG = 100mV) were preferably obtained from the statistical analysis of the working level of the respective detectors with miscellaneous fire source through the corridor and in the compartment. And the alarm-level of the smoke detector (CS = 0.1m-1) was recognized to be identified to the authorized fire-level of smoke-detector in Japan.抄録全体を表示PDF形式でダウンロード (566K) -
武田 久弘, 仲谷 一郎, 秋田 一雄1978 年 28 巻 2 号 p. 39-44
発行日: 1978年
公開日: 2013/01/11
ジャーナル フリーFor making clear the effects of ventilation opening and fuel surface on fires in enclosure, small scale model fires were studied experimentally by using methanol as a fuel. The behavior of fire was observed in detail, and the burning rate of liquid fuel and the temperature in enclosure were measured.
According to these results, the behavior of model fires changes gradually from a quasi-steady burning, at which flame attaches to the opening edge, to a stable fully developed fire with the increase of opening area of the enclosure. An oscillatory burning also appears at a transient region. The average temperature in enclosure increases with the ventilation parameter A√H in similar to that of the burning rate of fuel, while the temperature decreases with the surface areas of fuel tray.
In the present study, these experimental results were summarized by the use of a dimensionless ventilation parameter which was defined as a ratio of the rate of air entraiment through the opening to the maximum burning rate of fuel. Using this dimensionless parameter, both burning rate and average temperature do not depend favorably on the surface areas of the fuel tray and the size of enclosure, and so the ventilation controlled regime in enclosure fires can be determined definitely.抄録全体を表示PDF形式でダウンロード (465K)
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