Nondestructive Measurement of Momentum Transfer Collision Frequency for Low Temperature Combustion Plasma

Douglas Letsholathebe,Samuel Chimidza,Kgakgamatso M Mphale

doi:10.1155/2014/384701

Abstract

Accurately measured momentum transfer collision frequency and electron density for fire plasma enable correct simulation of electromagnetic wave propagation in the medium. The simulation is essential for designing high-performance systems suitable for the environment. Despite this, momentum transfer collision frequency for fire plumes has always been an estimated quantity and/or crudely determined. There are anecdotal reports of severe line-of-sight (LOS) radio frequency signal degradation on firegrounds. The problem has implications on safety of fire-fighters during wildfire suppression hence the need of high performance communication systems. In the experiment, a nonintrusive and direct method for measuring momentum transfer collision frequency in a fire plume was carried out. Using an automatic network analyser,x-band microwaves were caused to propagate combustion zones of eucalyptus and grass litter fires to measure the flames, scattering parameters. The parameters were then used to determine average collision frequencies for the plumes. The average collision frequencies for the eucalyptus and grass fire plumes were measured to be5.84×1010and5.92×1010 rad/s, respectively.

Highlights

Large high intensity wildfires are a recurring phenomenon in eucalyptus dominated forests of temperate south-eastern Australia and southern California shrublands [1, 2]
Antecedent climate under which the fires burn is often characterised by the occurrence of El-Nino Southern Oscillation (ENSO) related drought and persistent hot dry winds which sweep through the ecosystems making them fire prone [3]
Reliable radio communications systems which are capable of operating under severe atmospheric conditions are essential for distribution of information among firefighters

Summary

Introduction

Large high intensity wildfires are a recurring phenomenon in eucalyptus dominated forests of temperate south-eastern Australia and southern California shrublands [1, 2]. The wildfires result in tragic loss of human lives and properties worth millions of dollars, for example, Black Saturday fire incident (see [4]). Under such apprehensive situations, reliable radio communications systems which are capable of operating under severe atmospheric conditions are essential for distribution of information among firefighters. There are anecdotal reports of failure to maintain LOS radio frequency communication through large wildfire plumes [5]. This is a safety concern for fire-fighters on the fireground

Methods

Results

Conclusion