2013 1(12)

RESEARCH OF EVAPORATION REGULARITIES FOR PULVERIZED WATER MOVING THROUGH HIGH-TEMPERATURE GASES

Volkov R.S., Kuznetsov G.V., Strizhak P.A.

National Research Tomsk Polytechnic University, Tomsk, Russia

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Introduction

The prospects of pulverized water using for extinguish fires of various complexity are quite intensively discussed in recent years. Assumptions of expediency and of uselessness of using of such phlegmatizers of burning are formulated. At the same time there are results of theoretical investigations which show that pulverized phlegmatizers of burning can localize rather effectively a flame and quickly liquidate the ignition source as a whole. However practically there is no information about pilot studies in the field. In this regard, it is interesting to conduct experimental investigations for two-phase flows to assess the validity of the main theoretical conclusions.

Purpose

The purpose of that work is carrying out of experimental investigation to identify the integrated evaporation characteristics of the typical sprayed extinguishing liquids at movement through high-temperature combustion products.

Method

The experiments used a scheme providing pulverizing fluids (composition ¹ 1: H₂O – 99.5%, TiO₂ – 0.5%; composition ¹ 2: H₂O – 97%, TiO₂ – 0.5%, NaCl – 2.5%) from a certain height to the flame zone. Video footage of the sprayed liquid drops moving on a flame entrance, and also after passing of a flame zone was fixed. For formation of a steady flame the typical liquid fuel – kerosene was used. For combustion products temperature registration the technique of thermopair measurements was used. The integrated parameters of pulverized liquid drops moving through a flame, such as the weight, the sizes and speed of drops in working area, were determined by the video footage received in experiments.

All experimental investigations were carried out with use of modern measuring high-precision diagnostic PIV system.

Results

The executed experimental investigations allowed to establish some important points characterizing movement of typical sprayed extinguishing liquids through a flame:

• the influence of the salt impurities on completeness of the extinguishing liquid evaporation is established;

• the change ranges of the main evaporation integrated characteristics for the pulverized liquids drops are determined;

• it is shown that the two-phase flow rate of pulverized liquid is considerably decreases after passing the flame;

• it is established that for full evaporation of liquid at its passing of a flame height 1 m by it is expedient to spray it with the sizes of R_d < 0,25 mm.

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