Experimental study on fire behaviors in narrow bifurcated channel with a confined portal

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.

KEYWORDS:

• Bifurcated channel fire
• Confined portal
• Fire behavior
• Temperature distribution
• Experiment

Article highlights

• Fire behaviors in bifurcated channel with a confined branch portal were studied.

• Flame tilt caused by spatially asymmetrical entrainment was observed and analyzed.

• Temperature in main channel is asymmetrical and high temperature tilts to upstream.

• Fitted equation about temperature distribution in branch channel is developed.

• Maximum ceiling temperature over fire source decreases as confined ratio increases.

Disclosure statement

The authors declared no potential conflicts of interest with respect to the research, authorship, and publication of this article.

Additional information

Funding

This work was supported by the National Natural Science Foundation of China [No. 51576212]. The authors appreciate the supports deeply.