Flame propagation for polymers in cylindrical configuration and vertical orientation

doi:10.1016/S0082-0784(89)80134-1

Symposium (International) on Combustion

Volume 22, Issue 1, 1989, Pages 1231-1240

https://doi.org/10.1016/S0082-0784(89)80134-1 Get rights and content

Experimental results are presented for vertical flame propagation for single and multiple cylinders (electrical cables and solid pine). Experiments for single, 0.508 and 1.29 m long, cylinders were performed in our apparatuses; O₂ concentration in the range of 21 to 45% was used to enhance the flame propagation rate. Experiments for multiple cylinders were performed in our 5 MW-scale apparatus, with two (0.61 m wide and 4.9 m long) sheets of cables facing each other and separated by about 0.31 m.

A new technique based on the chemical energy released during flame propagation and extent of flame propagation was used to calculate the flame propagation rate. The flame propagation rate in the 500 kW and 5 MW-scale apparatuses showed good correlation and satisfied the engineering relationships derived from the fundamental flame propagation theories. The following relationship was found for the flame propagation rate: fx1231-1

For 0.508 and 1.29 m long cylinders, the effective flame heat transfer distance was estimated to be about 0.16 m. The extent of flame propagation and propagation rate were found to be interrelated. Under our experimental condition, without additional heat flux to enhance the flame heat flux, the extent of flame propagation was estimated to be 100% of the available area for V≥5×10⁻³ m/s, and for V≤1×10⁻³ m/s, the estimation showed no propagation.

References (9)

TewarsonA. et al.
Fernandez-PelloA.C. et al.
Comb. Sci Tech.
(1983)
QuintiereJ.G. et al.
Comb. Sci. Tech.
(1986)
SibulkinM. et al.
Comb. Sci. Tech.
(1977)

There are more references available in the full text version of this article.

Cited by (36)

Evaluating the combustion and flame extension characteristics of cable fire in utility tunnels with spontaneous combustion scenarios: An experimental study
2023, Tunnelling and Underground Space Technology
A cable fire in a utility tunnel can cause severe damage to the electric power supply in cities. This study aims to understand the combustion and flame spread characteristics of cable fires, which are mainly caused by overheating from the excessive current at the interconnections of the cables under spontaneous combustion. Fire experiments were conducted in a 1:6 scale model of a utility tunnel to analyse the flame spread characteristics under different heat release rates (HRRs), vertical distances, and transverse distances. The findings of this study show that the total burning time of the cable fire increases as the cable diameter increases, and the HRR also shows an increasing trend. Additionally, the spatial location of the cable fire has a significant impact on the flame spread. The terms H_c* and D_c* are defined to characterize the flame height and a general prediction model of the dimensionless flame height influenced by cable spontaneous combustion is proposed. A dimensionless model is also established to describe the flame spread rate. This research provides valuable guidance to aid in the development of fire safety measures in utility tunnels.
Experiment and numerical simulation of cable trench fire detection
2021, Case Studies in Thermal Engineering
Citation Excerpt :
Based on the classical fire heat transfer model, Hasegawa et al. [7] proposed a prediction model for the ignition time and upward fire spread rate of cables under the action of external radiant heat flux, and then evaluated and graded the fire performance of different types of cables. Tewarson et al. [8,9] obtained an empirical formula for the vertical upward fire propagation rate of cables and proposed the critical conditions for cables to sustain fire spread. Moreover, the influences of cable material, size and other parameters on fire spread behavior were revealed.
In this paper, the full-scale cable fire test is carried out in the fire compartment of cable trench in standard substation in order to explore the influence of fire detector sensitivity. The point-type temperature detector, point-type smoke detector, cable-type temperature detector, and suction-type smoke detector are used to test the fire alarm sequence. The temperature field, combustible gas concentration, and fire alarm sequence of fire detector with different sensitivity are simulated by FDS. The results show that: The numerical simulation results are in good agreement with the experimental results. The lower the alarm threshold, the shorter the response time of fire detector. The sensitivity of suction-type smoke detector has great influences on the detection results.
Evaluation of flammability and smoke corrosivity of data/power cables used in data centers
2021, Fire Safety Journal
Citation Excerpt :
FM 3972 measures the Fire Propagation Index (FPI) using small-scale flammability tests conducted with ASTM E−2058/ISO 12136 [3,4] Fire Propagation Apparatus (FPA). The flammability classification of FM 3972 was developed by correlating the fire test results of FPA flammability tests with intermediate-scale fire tests [5]. A comparative study by Khan et al. [6] evaluated NFPA 262 test method (the standard was UL 910 at the time of study and later accepted as NFPA 262 test standard), and showed that NFPA 262 is equivalent to FM 3972 for flammability evaluation of electrical cables.
Data centers use electrical cables to provide power and transmit data. The jacket and insulation materials of electrical cables are usually made with plastics and could be the major source of combustible materials in data centers. Therefore, understanding the fire and smoke hazard of electrical cables is important for reducing fire loss. For this purpose, we examined six electrical cables including power and data cables using the intermediate-scale parallel panel fire test (PPT), small-scale Fire Propagation Apparatus (FPA) test, and smoke corrosivity test. The PPT results showed that one cable examined in the PPT failed both the fire propagation and smoke generation criteria, and others passed. The FPA test measured the Fire Propagation Index and Smoke Damage Index using the ignition and fire propagation measurements, and the test results demonstrate the consistency with the PPT test results. Three electrical cables were examined for the smoke corrosivity, with two low smoke zero halogen (LSZH) cables showing lower smoke corrosivity and a cable with PVC insulation/jacket showing higher smoke corrosivity. This study shows that the LSZH cables examined herein have good fire and smoke corrosion properties. The fire/smoke corrosivity test methods provide a comprehensive approach to evaluate fire risk of electrical cables.
Effects of interlayer distance and cable spacing on flame characteristics and fire hazard of multilayer cables in utility tunnel
2020, Case Studies in Thermal Engineering
Citation Excerpt :
Zavaleta and Hanouzet [11] improved the previaous cable fire model (FLASH-CAT) to predict the heat release rate of the horizontal flame under wall-attached conditions. Tewarson et al. [12,13] obtained the empirical formula of upward spread rate of cable flame and proposed the critical conditions for the cable to maintain the flame spread. They also revealed the influence rule of the cable material, size, and other parameters on the flame spread.
Fire safety of utility tunnel, which is significantly affected with cables, has arouse public concern. This work experimentally investigated influences of interlayer distance (d) and cable spacing (s) on flame characteristics and fire hazard of multilayer cables in utility tunnel. Larger interlayer distance leads to higher flame height but lower flame width. The flame width decreases with an increase in cable spacing, while the flame height increases first and then reduces. The flame height reaches the highest value when s = 1.0 cm. Flame spread rate (v_f) progressively increases from bottom layer to the top when d = 4.5–7.0 cm, while the trend is inverse for d = 9.5–10 cm v_f over the middle layer presents the lowest value when s = 1.0–2.5 cm, while v_f gradually reduces from the bottom layer to the top for s = 3–4 cm. The maximum temperature of the pyrolysis zone of top cable layer gradually decreases as d rises, but rises in the bottom layer. When s = 1.0–2.5 cm, the highest temperature is observed in the middle cable layer, while in the top layer when s = 3–4 cm.
Experimental study on flame propagation over horizontal electrical wires under varying pressure
2020, International Journal of Thermal Sciences
Citation Excerpt :
The flame propagation behavior of electrical wires depends on extensive conditions. These conditions include internal and external parameters such as the insulation material [4], metal core material [5], wire diameter [6–8], core diameter [7,8], gravity environment [9–11], oxygen concentration [9,12–14], dilution gas [7,9], AC electrical fields [15,16], external flow [10,17], sub-atmospheric pressure [9,17–22], external radiation [13], and electric current [21,23,24]. Studies on the flame propagation behavior of electrical wires have also been conducted [9,19–22].
Flame propagation behavior over the polymer insulation of electrical wires can ignite adjacent combustibles and increase the scale of the fire. In this study, the flame propagation behavior over polyethylene (PE)-insulated wires was investigated theoretically and experimentally under varying pressures. The experiments were conducted in three cities with different altitudes (64, 76, and 100 kPa) and in a newly designed hypobaric chamber (7.5–101.3 kPa) for the first time. The flame morphology, structure, and spread rate were examined and discussed. The results show that pressure significantly affects flame propagation behavior. With increasing pressure, the flame illumination increases, and the flame shape changes, while the average flame height increases monotonously with decreasing average flame width. The weaker reaction rate and reduced heat transfer are the essential factors that result in a decreasing flame spread rate at lower pressures. In addition, a simplified correlation between the flame spread rate, pressure, and wire configuration in the form of $V_{f} \propto {(P^{2} L^{3})}^{0.65}$ is proposed to predict flame propagation along an electrical wire. Moreover, the influence of the metal core on the flame behavior was observed based on the different heat transfer mechanisms in the flame front zone. All results contribute to the safe operation of electrical wires.
Fire behaviors of flame-retardant cables part I: Decomposition, swelling and spontaneous ignition
2018, Fire Safety Journal
Citation Excerpt :
For example, Fernandez-Pello et al. [4] studied the piloted ignition time and the flame spread rate of several commercial cables under various external radiation and showed the similarity between the pyrolysis temperature of cable insulation and the ignition temperature. Tewarson and Khan [10] tested the upward flame spread over 35 commercial electrical cables with a copper or aluminum core, and found the metal core acted like the heat sink to slow down the flame spread. Xie et al. [11] conducted small-scale experiments (TG, FTIR, and MCC) on the new and aged cable PVC sheaths and found a strong aging effect on the heat release rate and toxic gas emission.
Electrical cable is a potential ignition source and fire hazard in residential houses, nuclear power plants, aircraft, and spacecraft. In this work, a bench-scale flame-retardant cable, consisted of the outer PVC sheath, middle XLPE insulation, and inner copper core, was heated uniformly inside a novel cylindrical heating chamber. The applied heat flux was transient, which increased with time close to a parabolic function. Once heated, the outer PVC sheath swelled and shrank under multiple stages. Before ignition, the swelling behavior was found to follow the same trend as the mass-loss rate. Analysis showed that the observed spontaneous ignition was likely a result of pyrolysis gas from inner XLPE insulation piloted by the smoldering hot spot (600~700 °C) on the outer charring PVC sheath. For the first time, the spontaneous ignition time was found to linearly increase with the integral heat flux, and it was different from other ignition experiments under the transient heat flux in the literature. Moreover, the measured critical mass flux of ignition increased with the heating power, and the critical surface temperature of PVC was above 500 $° C$ . The results of this work provide important information about the swelling and ignition behaviors of the flame-retardant cable under a real fire, and may guide the design of future fire-safety cable.

View all citing articles on Scopus

View full text

Flame propagation for polymers in cylindrical configuration and vertical orientation

Comb. Sci Tech.

Comb. Sci. Tech.

Comb. Sci. Tech.