Fire Technology

, Volume 53, Issue 3, pp 1275–1289 | Cite as

The Influence of Currents on the Ignition and Correlative Smoke Productions for PVC-Insulated Electrical Wires

Article

Abstract

Ignition of energized polyvinyl chloride insulated copper conductor wires by external heating was investigated for a better understanding of the initiation of electrical wire fires. First, a simplified theoretical analysis was developed to quantitatively explain the effects of currents on the ignition of electrical wires. The numerical result predicted that the ignition time concavely decreases with the increasing external heat flux while convexly decreasing with the increasing current of wire. Second, experiments with several sample wires were conducted to study the ignition process. It showed a good consistency between the experimental and numerical results. Using the methods of Transmission Electron Microscope, Scanning Electron Microscope and Fast Particulate Spectrometer, the properties of released smoke productions were obtained. The smoke particles size distribution was found independent to the current of wire and showed the same morphology with the standard test fires. The properties of pyrolysis smoke particles showed a two-regime behavior with the increasing current of wire. The pyrolysis smoke particle size distribution with one certain current showed a bimodal phenomenon. The three-stage changes of the count median diameter and geometry mean diameter were also presented.

Keywords

Electric current Electrical wire Ignition time Smoke productions PVC insulation 

List of Symbols

\( d \)

Diameter (m)

\( \delta \)

Thickness (m)

\( L \)

Length of heating zone (m)

\( A \)

Area (m2)

\( \rho \)

Density (kg/m3)

\( \lambda \)

Thermal conductivity (W/m/K)

\( c \)

Specific heat (kJ/kg/K)

\( h \)

Heat transfer coefficient (W/m2/K)

\( \dot{q}^{\prime\prime}_{e} \)

External heat flux per unit area (kW/m2)

\( I \)

Current (A)

\( T \)

Temperature (K or °C)

\( R^{\prime} \)

Electrical resistance per unit length (\( \Omega/\text{m} \))

\( Bi \)

Biot number

\( r \)

Radius (m)

Subscripts

c

Core

p

Insulation

w

Wire

ch

Coil heater

ig

Ignition

o

Outer surface

a

Ambient

b

Balance

Notes

Acknowledgements

This work was supported by the Joint Funds of the National Natural Science Foundation of China under Grant No. U1233102, the National Program on Key Basic Research Project of China under Grant No. 2012CB719702, and the Collaborative Innovation Center of City Public Safety of Anhui Province. The authors gratefully acknowledge all of this support.

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Copyright information

© Springer Science+Business Media New York 2016

Authors and Affiliations

  1. 1.State Key Laboratory of Fire ScienceUniversity of Science and Technology of ChinaHefeiChina

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