Journal of Fire Sciences current issue

Experimental Investigation on Onsetting Internal Fire Whirls in a Vertical Shaft

Chow, W.K., Han, S.S. — Wed, 21 Oct 2009 07:41:23 PDT

Internal fire whirls might be induced in tall buildings under fires. Hazards associated with such fire whirls should be assessed carefully. The physics behind is not clearly understood, even the conditions of onsetting internal fire whirls are unknown. It is important to observe the physical phenomenon carefully first, before carrying out theoretical analysis.

In this article, internal fire whirls were studied with a small vertical shaft model under different ventilation conditions. A 1.6 kW propanol pool fire was placed in a rectangular vertical shaft of height 145 cm. Ventilation provisions at the bottom and side wall were arranged. The conditions of onsetting internal fire whirls were investigated in detail with support from some full-scale burning tests at Harbin, Heilongjiang, China.

It is concluded that allowing a vertical gap of appropriate width and height at the side wall would onset internal fire whirls. Flame height would be stretched by several times the value for free burning. The burning rate of the pool fire would increase. Results are also confirmed by full-scale burning tests.

Experimental Study on the Interaction of a Water Drop Impacting on Hot Liquid Surfaces

Wang, X.-S., Zhao, X.-D., Zhang, Y., Cai, X., Gu, R., Xu, H.-L. — Wed, 21 Oct 2009 07:41:26 PDT

This article presents the results of experimental investigation of water drop impacting on surfaces of different fuel liquids, such as alcohol, kerosene, and molten-ghee, which are typical fuels for liquid pool fire study or typical fire source in historical buildings. Each of the liquids was heated to simulate the temperature conditions as it burns, although the temperature is still a little lower than the real one. The impacting processes were recorded using a high-speed digital camera with 1000fps. The results show that the liquid physical properties, such as surface tension, viscosity, and miscibility, have primary influences on the drop impact behavior except for drop Weber number, and liquid temperature mainly influences the size of the splashed drops and bouncing height of the jet. The drop liquid is ejected for water—alcohol impact, while the bulk liquid is ejected for water—kerosene impact. The drop immersed into the liquid when it impacts on molten-ghee surface, no splashing and drop rebounding occur in this case.

Analysis and Modeling of Ignitability of Polymers in the UL-94 Vertical Burning Test Condition

Wang, Y., Zhang, J., Jow, J., Su, K. — Wed, 21 Oct 2009 07:41:27 PDT

Modeling the UL-94 vertical burning test is of practical importance in industries which, however, has not been addressed sufficiently. In this article, a 3D convective heat transfer model was developed to simulate ignition times for the UL-94 test. An experimental procedure was proposed to measure ignition times of two polymers under the UL-94 test condition. Comparisons between experimental and simulated results of ignition times showed that edge effects were significant in the ignition process of the UL-94 test and the convective heat transfer ignition model considering edge effects gave ignition times close to experimental results. Sensitivity analyses showed that the ignition time increased linearly with decreasing initial temperature and increasing density, heat capacity and emissivity, but nonlinearly with decreasing flame temperature and convective heat transfer coefficient and increasing thickness, thermal conductivity, and ignition temperature of the specimen.

Flame Retardant Finishing of Cotton Fleece Fabric: Part VI. The Combination of a Hydroxyl-Functional Organophosphorus Oligomer and 1,2,3,4-Butanetetracarboxylic Acid

Cheng, X., Yang, C. Q. — Wed, 21 Oct 2009 07:41:29 PDT

The use of flame retardant finishing becomes necessary for cotton fleece to pass the U.S. government regulation ‘Standard for the Flammability of Clothing Textiles’ (16 CFR 1610). The objective of this research was to reduce the flammability of cotton fleece using a flame retardant finishing system consisting of a hydroxyl-functional organophosphorus oligomer (HFPO) as a flame retardant and 1,2,3,4-butanetetracarboxylic acid (BTCA) as a bonding agent. We investigated the role triethanolamine (TEA) played as a reactive additive in the HFPO/BTCA finishing system on cotton fleece. We also applied micro-scale calorimeter (MCC) to study the effectiveness of HFPO and BTCA in reducing the flammability of cotton. BTCA alone was able to reduce the peak heat release rate (PHRR) of cotton as demonstrated by the MCC data. Combining BTCA with HFPO decreased PHRR further and also significantly reduced the decomposition temperature and the temperature at PHRR of cotton. The cotton fleece treated with HFPO/BTCA/TEA passed the federal regulation (16 CFR Part 1610) and achieved ‘Class 1’ flammability. The treated cotton fleece was durable to multiple home laundering cycles. The use of TEA enhanced the performance of HFPO/BTCA and the treatment caused no significant changes in fabric physical properties.