火災プルームの巨視的性状に関する研究 A Study on the Deterministic Properties of Fire Plumes
A lot of studies on fire plumes formed above fire sources have been carried out in the field of building fire analyses. There are two methods to define the boundaries of continuous, intermittent and plume regions of turbulent diffusion flames. One is to be decided from flame height. And the other is to be decided from the properties of fire plumes on the basis of the classical theory on the point-source plumes. The relationship between them had been ambiguous, and we proposed the following models of virtual source locations resulted from the past experimental works [15-18]: <br>z<sub>0</sub> = (γ − α<sup>2/5</sup>C')Q＊<sup>2/5</sup>D (Q＊ ≧ 1), <br>z<sub>0</sub> = γQ＊<sup>2/3</sup>D − α<sup>2/3</sup>C'Q＊<sup>2/5</sup>D (0.1 < Q＊ < 1) <br>In order to ensure these models, several experiments were performed by using 0.14 m or 0.2 m square burner with LPG or LNG fuels. Flame heights were recorded by video tape recorder, and the centerline temperatures and velocities were recorded for 5 minutes at 5 seconds interval in a steady state. <br>As the results, the flame heights were formulated as Lf=γQ＊<sup>n</sup>D, where n=2/5 for Q＊ ≧ 1, and n=2/3 for 0.4 < Q＊ < 1. And γ equals 3.30 for the mean heights, 4.40 for the boundary height between intermittent flame region and plume region, and 2.10 for the boundary height between flame region and intermittent flame region for calculating z<sub>0</sub>. According to these results, excess temperatures and velocities were plotted above along the central axis of fire plumes. It was found that the boundaries decided both from flame heights and from excess temperatures had been in agreement with each other.
日本火災学会論文集 44(1), 25-37, 1996-04-30
Japan Association for Fire Science and Engineering