The extinguish process using the water mist jet is one of the most efficient system for hydrocarbon flame accidentally developed. The environmentally friendly of the system is an important challenge. Both free jets characteristics are analysed in aim to have a quick suppression of the flame. The paper is focused on the geometrical shape of the cone realised by every jet (flame and water mist). On this basis the relative position of the jets is decisive in aim to obtain the desired effect. Experimental measurements were made, and the results are presented in the paper including the infrared temperature field. The experimental analysis allows to find the adequate angle between jets for the flame extinction. So, the optimum position of the water mist jet applied on the fire was found. A thermal flame extinguish efficiency evaluation is presented, too. The system is non pollutant and the damages are reduced.
Nowadays the world is facing an increasingly traffic, especially in the road. In order to short the distances and cross various road areas, road tunnels are built frequently and longest as possible. One of the greatest emergency situations that can occur in road tunnels, is represented by fire, involving all conditions relating to the nature and density of combustible materials existing, smoke, toxic gases and the combustion debris from fire fighting and action in order to minimize the negative consequences of it. Also, road tunnels represent semi-closed and closed spaces, with high fire risk, so no easy fire safety management opportunities can be used. Road tunnels can be framed in the category above mentioned, being exposed to a high traffic, because most of them are 20-30 years old and were built for the traffic estimated of those times. A simulation using Pyrosim software is based on the physical model in which one electrical fault accident involving a car appear. The accident, consisting in a fire event at one stationary car, is modeled at 1.5 m height. Considering an electrical fault followed by a fire, temperature and smoke spreading depending on time in this tunnel were obtained. Also, sprinklers have been used in the simulation time, in order to give an accurate firefighting simulation. There were obtained important values which allow us to realize an appropriate impact on the event in aim of minimizing the time for a promptly intervention and to limit the damages.
The aim of this work is to make a visual investigation of the fire behavior during the extinguish process with water mist at different temperatures, different diameters of the nozzle and different angles of diffusion jet, too. It was used a numerical simulation approach to analyze 24 scenarios regarding the influence of mist water in fire extinguish process. The main test was focused on a given enclosure with dimensions of 1.0 × 1.0 × 3.0 m and the fire source placed inside, in the middle. The enclosure is considered opened on the upper part. From the numerical simulation values, we concluded the best scenario in fire extinguish process using water mist.
The main objective of the present paper is to provide a visual investigation of the fire and water mist interference during the extinguish process. This kind of the experimental study for these processes is imposed by the phenomena complexity. The experimental study provides us the information of real behaviour of jets assembly in operation. On this way the physical theoretical model may by better conceived. The main test was focused on the concave shape of ceiling, which gives the better suppression of the flame. From the heat balance, of the studied case, the extinguish efficiency is obtained, the values being around 20%. From these values result that a lot of working agent is lost. That loss is related to the finest of the droplets in the liquid jet. The experimental tests give us the optimal angles between the two jets in aim to realise an efficient extinguish operation.
The paper presents the theoretical and experimental aspects concerning the droplet evaporation processes from the liquid jet, sprayed in an air vapour mixture. From the particularities of the transfer phenomena involved in the droplet evaporation, the lifetime evolution of this, as a function of liquid temperature, its dimension and the surroundings humidity, is displayed. The surroundings consist in a semi-open room in which we may control the entry of the fresh air. Based on these theoretical approaches the test bench was developed. The aspects regarding the experimental tests are mentioned as the jet development followed by the evaporation quality. The experimental diagrams concerning the chart of temperature and humidity inside and near the two-phase jet are shown. The practical values of the measured parameters allow us to use the jet device with a warm liquid in the extinguish system. The tests were realised with various liquid temperature for the gaseous hydrocarbon flame. From the experiment it was observed that the liquid phase in contact with the flame evaporates instantaneously forming the superheated vapour. Consequently, the vapour huge volume generated on this way will decrease the oxygen concentration in the mixture, which may fall it under the ignition limit. On the other hand, the surrounding temperature reduces due to the heat absorption during the liquid evaporation. These two phenomena, which act on the flame, rise the extinguish efficiency of the two-phase jet.
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