ABSTRACT

A series of experiments were conducted in a bifurcated channel consisting of horizontal main and branch channels to investigate the effects of branch and the confined ratio (the ratio of confined area to cross-section area at branch portal) on fire behaviors. The cross-angle between main and branch channels was 45° and ethanol pool fire fixed in the main channel center was used as fire source. Temperature distribution and flame behavior inside channel were recorded and analyzed. The results show that the branch leads to a much difference in the pattern of smoke flow and makes flame tilt to proximal sidewall to some extent, which is probably ascribed to the asymmetrical air entrainment in spatial. Cold air entrained through branch channel and downstream of main channel is more tend to carry hot smoke into upstream to enhance heat exchange and disturbance to smoke layer, which causes temperature field to asymmetrically distribute and high-temperature region to migrate to upstream. The confined ratio, which determines the proportion of opening area at branch portal, has no obvious influence on temperature distribution of main channel, while it could significantly affect temperature distribution inside the branch channel. The temperature below branch channel ceiling significantly increases with the increase of confined ratio at branch portal, and a corresponding empirical equation is developed. Additionally, under current experimental conditions, the maximum ceiling temperature in bifurcated channel is obviously lower than that of ordinary channel and decreases as confined ratio increases.

摘要

在由水平主、支通道组成的分叉通道中进行了一系列实验，以研究分支和约束比（约束面积与分支入口处的横截面积之比）对火灾行为的影响。主通道与支通道的交叉角为45°，以固定在主通道中心的乙醇池火为火源。记录和分析通道内的温度分布和火焰行为。结果表明，该分支导致烟气流动模式有很大差异，并使火焰向近端侧壁倾斜一定程度，这可能归因于空间上不对称的空气夹带。主通道下游夹带的冷空气更容易携带热烟进入上游，加强对烟层的热交换和扰动，导致温度场分布不对称，高温区向上游迁移。密闭比决定了支道口开口面积的比例，对主通道温度分布没有明显影响，而对支通道内部温度分布有显着影响。分支通道顶板以下的温度随着分支入口处密闭比的增加而显着增加，并建立了相应的经验方程。此外，在目前的实验条件下，