Journal of Fire Sciences recent issues

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.

Comparative Verification Exercises on a Probabilistic Network Model for Building Evacuation

Spearpoint, M.J. — Fri, 28 Aug 2009 08:35:36 PDT

Functional testing of any model is a vital step in demonstrating that its predictive capabilities are working appropriately; correspond as expected to the circumstances being modeled and where further work should be directed. This article presents a series of exercises used to substantiate the movement prediction capability of a probabilistic network-based evacuation model that is currently under development. Two simple component configurations and two previously available worked examples are used to demonstrate that the model performs adequately. Movement times from model predictions, hand calculations, alternative empirical methods, and other computer models were compared for a range of typical occupant densities.

Flame Retardant Finishing of Cotton Fleece Fabric: Part IV-Bifunctional Carboxylic Acids

Wu, X., Yang, C. Q. — Fri, 28 Aug 2009 08:35:36 PDT

Most cotton fleece fabrics are not able to meet the federal flammability standard for general apparel (16 CFR 1610). In this research, we applied three carboxylic acids, i.e., succinic acid (SUA), malic acid (MLA), and tartaric acid (TTA), as flame retardant finishing systems for cotton fleece. We found that all three acids are able to esterify cotton in the presence of sodium hypophosphite as the catalyst, and SUA is the most reactive and the most hydrolysis-resistant when it is bound to cotton. The a-hydroxyl group with both MLA and TTA appears to hinder esterification and to facilitate hydrolysis for MLA and TTA bound to cotton. All three bifunctional carboxylic acids are effective in reducing the flammability of cotton fleece from ‘Class 3’ to ‘Class 1’. The micro-scale combustion calorimetry data reveal that SUA reduces cotton flammability by reducing its peak heat-release rate and heat-release capacity. The cotton fleece treated with SUA also has the highest bursting-strength retention and the least fabric yellowing.

Attenuation of Incident Heat Flux by Pyrolysis Volatiles when Heated Using Resistance Element Radiant Heater

Zhou, Y., Yang, L., Dai, J., Wang, Y., Deng, Z. — Fri, 28 Aug 2009 08:35:36 PDT

The attenuation of an incident radiant heat flux by pyrolysis volatiles when heated under a resistance element radiant heater, a phenomenon that is not well understood, is studied by simulated experiment and mathematical models. The radiation attenuation of an incident heat flux when pine or PMMA is heated (6—14%) obviously commences before ignition, although it is not as large as the result reported by Kashiwagi (50—80%) using a laser radiant heater. The calculated results clearly indicate that ignition models must consider radiation attenuation by pyrolysis volatiles.

Synergistic Effects of Fe2O3 with Layered Double Hydroxides in EVA/LDH Composites

Jiao, C., Chen, X., Zhang, J. — Fri, 28 Aug 2009 08:35:36 PDT

The synergistic effects of Fe₂O₃ with layered double hydroxides (LDH) in ethylene vinyl acetate copolymer/LDH (EVA/LDH) composites have been studied using limiting oxygen index (LOI), UL-94 tests, and cone calorimeter test (CCT). The results from the LOI and UL-94 tests show that the Fe₂O₃ can also act as flame retardant synergistic agents in the EVA/LDH composites. The CCT data indicated that the addition of Fe₂O₃ in the EVA/LDH system can greatly reduce the heat release rate, total heat release, carbon monoxide and carbon dioxide.

The Impact of Exit Route Designs on Evacuation Time for Crawling Occupants

Kady, R. A., Davis, J. — Fri, 28 Aug 2009 08:35:36 PDT

According to the Life Safety Code^®, the distance between the exit access and the exit is a function of the occupants, type and number of obstructions, and the type of hazard. This study investigates the impact of route design on evacuation times for crawling movements. The study compares evacuation time for a straight route to an indirect route design, and the influence of occupant characteristics, in terms of gender and BMI, on evacuation time for occupants crawling an indirect route. Eighteen subjects (9 males and 9 females) in the 19—29 age stratum participated in the study (normal, overweight, and obese). The findings indicate a statistical difference between evacuation time for crawling in a straight route and an indirect one. Furthermore, the study reveals that both gender and BMI are major physical determinants of evacuation time of crawlers in an indirect route. The study is an attempt to provide data on occupant movement in unique circumstances (such as crawling an indirect route). Such data will contribute to enhance the ability of evacuation models to better represent occupant movement in different building enclosures.

Zinc Stannates as Alternative Synergists in Selected Flame Retardant Systems

Horrocks, A.R., Smart, G., Price, D., Kandola, B. — Fri, 28 Aug 2009 08:35:36 PDT

Zinc stannates, including zinc hydroxystannate, are used components within synergistic fire retardant systems usually in conjunction with halogenated species in a number of polymers. Their behavior is similar to antimony III oxide (ATO) in that they enhance the effectiveness of the halogenated and, principally brominated retardant (Br-FR), present. Unlike antimony III oxide, they are non-toxic but are specific in their synergistic activity. Furthermore, they are effective smoke suppressants. This article reviews the published literature with regard to this synergistic specificity as well as the role of zinc stannates as synergists and smoke suppressants in halogenated polymers exemplified by poly(vinyl chloride), polyolefins exemplified by polypropylene, polyamides, acrylonitrile-butadiene-styrene and polyester and epoxy resins.

Erratum

Fri, 28 Aug 2009 08:35:36 PDT

Flammability and Thermal Properties of a Novel Intumescent Flame Retardant Polypropylene

Qingliang He, , Hongdian Lu, , Lei Song, , Yuan Hu, , Lijuan Chen, — Tue, 28 Jul 2009 01:38:19 PDT

A novel intumescent flame retardant system (IFRs) combines Tri (1-oxo-2,6,7-trioxa-1-phosphabicyclo [2. 2. 2] octane-methyl) phosphate (TPMP) with melamine pyrophosphate (MPOP) and its application in polypropylene (PP) has been investigated. The thermal stability, flammability, and water resistance were studied by thermogravimetric analysis (TGA), UL-94 test, and cone calorimetry. TGA shows that pure PP degrades at about 4008C, while sample PP-6 degrades at about 270°C under nitrogen atmosphere. With 30wt% total loading of the IFRs, sample PP-6 passes the UL-94 V-0 test. It can still pass the UL-94 V-0 test after the water treatment. The introduction of TPMP and MPOP strongly decreases the peak heat release rate (PHRR) value of the flame retardant (FR) PP composite. The morphologies of the char residues obtained after cone calorimetry were investigated by means of scanning electron microscopy (SEM). The char residue of sample PP-6 has better structure, which prevents the underlying materials from further decomposing. X-ray photoelectron spectroscopy (XPS) was used to further explore the char residues of the FR PP composites. The results show that sample PP-6 has the best char residue, which enhances the oxidation resistance of the char layer.

Evaluation of Forest Fuel Flammability and Combustion Properties with an Adapted Mass Loss Calorimeter Device

Madrigal, J., Hernando, C., Guijarro, M., Diez, C., Marino, E., De Castro, A.J. — Tue, 28 Jul 2009 01:38:19 PDT

An adapted bench-scale Mass Loss Calorimeter (MLC) device for evaluating forest fuel flammability and combustion properties is proposed. This fire test apparatus consists of an MLC fitted with a chimney containing a thermopile. After the thermopile output has been calibrated by use of a methane burner, these data are used to quantify heat release, as an alternative to the classical measurement of oxygen consumption due to combustion. The results showed good repeatability and reasonable approximation to HRR values obtained with a cone calorimeter, and also demonstrated that each variable analyzed was significantly affected by the species considered.

Simulating a Building as a People Movement System

Gwynne, S.M.V., Kuligowski, E.D. — Tue, 28 Jul 2009 01:38:19 PDT

Egress models are being used more frequently to simulate people movement; i.e., how people enter, use, and leave a building. However, little has been written on the different phases of people movement over the lifecycle of the building that can be examined and how these models may achieve this. In addition, little has been written on how these phases interact. This interaction may be due to these different phases occurring simultaneously or when an individual's experience in one phase (e.g., entering a building) influences another (e.g., route selection when leaving). This paper presents six modes in which an egress model can be applied: Naïve, Operational, Predictive, Engineered, Real-Time, and Interactive. The paper describes what is needed to enable these application modes, in terms of data, expertise, and model functionality and the benefits that these modes provide. These modes should appear in the same model enabling a comprehensive and integrated representation of people movement, and the factors that influence it, to be produced.

Design Fire Experiments for Commercial Premises

Zalok, E., Hadjisophocleous, G.V., Lougheed, G.D. — Tue, 28 Jul 2009 01:38:19 PDT

Two series of experiments were conducted to determine the burning characteristics of different fuel packages, in both pre- and post-flashover fires, to develop data to characterize design fires for commercial premises. These fuel packages represented fuel loads determined from the survey of commercial buildings. Results suggest substantial differences in the burning characteristics of different stores. In this article, the description of the recommended design fires includes: (1) types of combustibles, (2) fire load density (MJ/m²), (3) fire growth rate, and (4) yields of CO and CO₂.

Thermal Decomposition Behavior of the Flame Retardant Melamine in Slabstock Flexible Polyurethane Foams

Konig, A., Fehrenbacher, U., Kroke, E., Hirth, T. — Wed, 06 May 2009 04:39:16 PDT

Due to their low density, high surface-to-mass ratio, high air permeability and open cell structure, slabstock polyurethane foams ignite easily and have a high burning velocity. In this study, the decomposition behavior of melamine in both an inert and an oxygen atmosphere has been investigated. TGA/DSC and EGA-IR experiments revealed the decomposition steps and products in inert and oxygen atmospheres, respectively. Cone calorimeter, NIR-flame characterization and small-scale burner test results showed that the excellent working mechanism of melamine as a flame retardant mainly depends on the formation of an effective closed char layer, which may involve condensation of melamine to form melam, melem, and related products as well as reactions of the amino and isocyanato groups forming urea derivatives, and the sublimation of melamine at the exact temperature at which TDI release occurs.

Development and Application of Smoke Leakage Test Apparatus

Chuang, Y.-J., Luan, C.-P., Lin, C.-Y., Chen, P.-H. — Wed, 06 May 2009 04:39:16 PDT

The purpose of this study is to establish a CNS 15038 conforming apparatus for smoke leakage testing. The maximum test size accommodated by its test chamber is 3 m(H) x 3 m(W). The test apparatus is capable of controlling temperature and pressure. The test chamber wall, fan, and air duct are enclosed by sandwich construction (steel plate + rock wool + steel plate) and filled with heat resistant materials, which reduces the leakage rate of the apparatus to 1 m³/h. Three circular openings with different areas are used in this study for the basic volumetric airflow rate test. The apparatus proves to be capable of accurately measuring the volumetric airflow rate for a range of opening areas. The measurement is also made for wooden doors. The results of the study show that the volumetric airflow rate decreases gradually when the temperature increases, but as the temperature reaches 150°C, the volumetric airflow rate for wooden doors starts to increase. The test apparatus can be used for measuring the volumetric airflow rate for various gaps or openings. The design of this apparatus also provides an example for establishing other leakage test apparatus in the future.

Studies of the Action of Silicone at the Interphase on the Flame Retardant System of EBA Copolymer-chalk

Nianhua Huang, , Jianqi Wang, — Wed, 06 May 2009 04:39:16 PDT

Mechanistic study on the system has been performed with the aid of XPS in combination with other appraisal techniques, like TGA/LOI/CONE. It follows that remarkable enhancement of silicon-containing species at the surface region in the course of the combustion appear to play the crucial role for the protective barrier.

Flow Structure Downstream of a Confined Buoyant Round Jet in Cross Flow with Relevance to Tunnel Fires

Michaux, G., Vauquelin, O. — Wed, 06 May 2009 04:39:16 PDT

The flow structure downstream of a confined buoyant round jet in cross flow discharging into a channel is investigated. Experimental visualizations in the rectangular channel cross-section revealed that the interface between the upper layer of light gas and the lower clean air layer is distorted, appearing in the form of `hollows' and `bulges.' Numerical simulations show that these flow features are due to vorticity transfers from the upper to the lower part of the channel. Applied to the tunnel fire issue, this study contributes to the understanding of the impact of a longitudinal ventilation on a fire plume in a tunnel that can affect the smoke natural stratification.

Flame Spread in Opposed Flow along the Ground Soaked with High-volatile Liquid Fuel

Ishida, H., Kenmotsu, Y. — Wed, 06 May 2009 04:39:16 PDT

The flame spread in opposed flow through the layered flammable gas mixture along the ground soaked with high-volatile liquid fuel was studied experimentally. The effects of opposed flow velocity on the aspect of flame spread, the velocity of flame spread, the thickness of flammable gas layer and the preheated distance ahead of the flame leading edge were investigated experimentally. If the velocity of opposed flow at about 1 mm above the ground surface is over the flame spread velocity with no surrounding airflow, no flame spread occurs even when the ground temperature is highly above the flash point of the spilled liquid fuel. The velocity of opposed flow has a large effect on the preheat distance ahead of the flame leading edge also. With increase in the velocity of opposed flow, the maximum preheat distance decreases to the local minimum, and increases to the local maximum thereafter. This is due to the balance between the convective cooling by the flow and the heat conduction through the ground beneath the inclined flame in downstream.