Fire Extinguishing Process Research Articles

Thermal kinetics of nitrogen inhibiting spontaneous combustion of secondary oxidation coal and extinguishing effects

Spontaneous combustion of secondary oxidation coal seriously affects the safety of goaf in coal mine. To investigate the effect of nitrogen on secondary oxidation coal, thermal analysis and temperature-programmed methods were adopted to explore the thermal behavior and extinguishing ability. The combustion process was divided into the heating process and extinguishing process. Simultaneous thermal analyses performing connected with a Fourier transform infrared spectroscopy analyzer, were applied to the heating process. A temperature-programmed system was employed for extinguishing process. The results demonstrated that nitrogen concentration inhibited the oxidized decomposition and solid-phase reaction. As the nitrogen concentration increased, characteristic temperatures were delayed, and the activation energy of the secondary oxidation coal combustion stage elevated from 138.6 to 158.6 kJ/mol. The nitrogen concentration had little effect on the product H2O, CO, and CO2, while change of the nitrogen concentration mainly inhibited the generation of oxygen-containing functional groups and decomposition of aliphatic hydrocarbons. When the nitrogen concentration increased to 50% during the extinguishing process, the time required for the temperature to decrease from 400 to 30 °C was 39.0% shorter than that during natural extinction, and CO disappeared 42.1% faster. Reaction kinetics were used to analyze the fire extinguishing process of secondary oxidation coal and its spontaneous combustion. The heating process is conducive to determining the combustion characteristics of secondary oxidation coal. The extinguishing process experiments can monitor the changes after extinguishing the spontaneous combustion of coal in a closed fire zone.

Motion Stability of Fire Ladder Truck Under Braking Process Working Conditions

During the fire extinguishing process, the motion stability of the fire ladder truck can be affected by the jet reaction forces of the fire water monitor, lengths, vertical angles and horizontal angles of the fire ladder. This paper presents a virtual prototype method and its analysis of the effects of the aforementioned parameters on the motion stability of fire ladder truck under different working conditions during the braking process. An experiment analyzing fire water monitor jet reaction forces is established in this paper to obtain the forces under working conditions as the boundary conditions for the subsequent simulation analysis. During the simulation, two vertical pitch angles and three horizontal angles of the fire ladder are selected in this paper as the boundary conditions for the fire ladder truck motion stability simulations. The judgment standard of the motion stability of fire ladder truck is based on design criteria that the vehicle can maintain stability under braking operating working conditions if the maximum vertical pressure forces of all tires range from 0 N to 100,000 N. Thus, the findings based on the analysis results of this study can provide a theoretical foundation for the stability design of a fire ladder truck.

Applicability of liquid nitrogen fire extinguishing in urban underground utility tunnel

This paper built the experimental platform in the shrinkage-sized circular utility tunnel. A series of experiments were conducted by changing the parameters of liquid nitrogen injection. The feasibility of liquid nitrogen fire extinguishing in utility tunnel was studied. It is found that the main mechanism of liquid nitrogen fire extinguishing is cooling and asphyxiation. Cooling during vaporization can suppress fire rapidly, and the asphyxiation completely extinguishes the flame. During the liquid nitrogen fire extinguishing process, the temperature and the heat flux showed a decreasing trend of fast first and then slow. By increasing the injection rate and time of liquid nitrogen, the process of fire extinguishing can be accelerated and the extinguishing time would be shortened significantly. In addition, it is also found that the critical temperature at the flame of liquid nitrogen fire extinguishing is 230.0 °C, and the critical heat flux at 0.2 m from the flame is 0.20 kW/m2. Not considering oxygen consumption and nitrogen leakage, the critical oxygen volume fraction of liquid nitrogen extinguishing cable fire in utility tunnel is about 15–16%.

Pool fire suppression performance by twin‐fluid water mist under low pressures in an altitude chamber

AbstractFire suppression tests using low pressure twin‐fluid water mist under low pressure environments were carried out to exam the performance of water mist systems at low pressure environments. The experiment results show that the suppression time gets shorter for lower chamber pressure, and relevant total weight of water and nitrogen used decreases as the chamber pressure gets lower. For the case of 30‐cm diameter pool fire, the suppression times are 20.19, 7.5, and 2.24 under the chamber pressure of 60, 38, and 24 kPa, respectively. In case of a cargo compartments fire, it is suggested to open the ventilation valve of the cargo compartment at a high cruising altitude to relieve pressure, so as to achieve rapid fire suppression. When a fire happens at the position off the center below the water mist nozzle, the water mist suppression effects will be weakened. The fire size has little effects on the fire extinguishing process under pressure of 24 kPa. Under the critical atomization condition with the pressure differential between the inlet and outlet of the nozzle for water as 0.05 MPa (5.04 L/min), and the pressure differential for nitrogen as 0.10 MPa (10.97 L/min), the suppression time is the shortest as 18.66 seconds.

Model of Thermal Mechanism of Subclass A1 Fire Extinguishing with General Purpose Fire Extinguishing Powder in Non-Stationary Heat Exchange Conditions

The aim of the paper was to develop a model of thermal extinguishing mechanism using dry chemical powder taking into account the inertia of heat transfer to powder particles during unsteady heat exchange to identify the optimal conditions for extinguishing of A1 class fires with powders.The method of experimental and mathematical modelling of fire extinguishing process using dry chemical powder with short-term effect on the fire was used to achieve the goal. The experimental dependences of the extinguishing time and unit consumption of the extinguishing powder on the intensity of the powder supply to the combustion zone in extinguishing of subclass A1 fire in same area and in a limited volume were obtained. The mathematical model of a thermal extinguishing mechanism using dry chemical powder has been developed, taking into account the inertia of heat transfer to powder particles during unsteady heat exchange.Analysis of the regularities of extinguishing the subclass A1 fire using powder with a short feeding it into the fire indicates the presence of optimum values of unity consumption of powder on the fire from the intensity of feeding it into the fire. The presence of this optimum is due to the inertia of extinguishing the subclass A1 fire using powder due to the finiteness of the heat transfer time to the particles of the extinguishing powder and the limited time of interaction of particles with the combustible material.The theoretical analysis of the fire extinguishing process over the area taking into account the inertia of heat transfer to the powder particles at non-stationary heat exchange are carried out. The results of the analysis are in qualitative agreement with the results of the experimental study of the regularities of extinguishing of model fire foci of subclass A1 with General-purpose fire extinguishing powder.

Irovers: Real Time Unmanned Four Wheeled Iot Vehicles for Fire Monitoring and Extinguishing using Sonic Waves

The aim of the proposed system is to build an autonomous mobile robot system for measuring the various levels of air and noise pollution as well as the fire monitoring and in case of fire, this robot is used to extinguish the fire using SONIC WAVES. This is a IOT based robot which moves autonomously avoiding obstacles using the IR sensor. This robot is used for temperature monitoring for the analysis of the presence of fire. The data from the robot is sent and received using WIFI in IOT. This mobile robot is capable of avoiding obstacles using IR sensor thereby it can be easily introduced in places of fire accidents for the process of fire extinguishing. The fire detection are monitored by using the temperature sensor. These information from the sensor are sent to the PIC microcontroller and then using the wi-fi the information are sent to the cloud. The fire extinguishing process is carried out by the sonic fire extinguisher

APPLICATION OF MODELS OF INFORMATION AND ANALYTICAL SUPPORT SYSTEMS FIRE FIGHTING RESCUE UNITS

Objectives It was proposed to review the structure of the fire and rescue divisions management system, based on the decomposition of the forces and means of the subdivisions into fire extinguishing positions and ensuring fire extinguishing actions.Method The structural and functional model of the development of the fire and rescue divisions management system has been clarified, which allows to present the stages of the development of the system as components of a single fire extinguishing process. The reasons for the lack of information about the situation at the site of a fire in a person who makes management decisions regarding the forces and means of fire and rescue units are given.Result The analysis of information about the situation at the place of fire consumed by the person making management decisions. The structure of the database of the object of possible fire as a source of design parameters for the system of information and analytical support for the management of fire and rescue units is given. The structure of the settlement module of the system of information and analytical support for the management of fire and rescue units in the organization of extinguishing fires in buildings is proposed. The conditions for the interaction of the person making management decisions in relation to the forces and means of fire and rescue divisions with the software of management support systems and documents of preliminary planning of actions of the divisions for fighting fires and conducting rescue operations are given.Conclusion The software implementation of the models of information and analytical support systems for the management of fire and rescue units makes it possible to formalize the process of researching the fires that have occurred. The direction of perspective integration of models of information and analytical systems support systems for fire and rescue units in their activities is given.

Fire-Extinguishing Efficiency of Superfine Powders under Different Injection Pressures

Ammonium phosphate fire-extinguishing agents are one of the best substitutes for halon in many powder media. Here, 11 μm median diameter ammonium phosphate ultrafine dry powder was used as a fire-extinguishing medium. The fire-extinguishing performance of ultrafine powder under different pressures was studied by analyzing fire-extinguishing time, amount of extinguishing agent, and temperature during the fire-extinguishing process. The results show that the fire-extinguishing performance of the ultrafine powder is improved with increasing injection pressure. Finally, we used FDS software for fire simulation to study the influence of injection pressure on the extinguishing agent. The results show that the extinguishing time is shortened with increasing injection pressure. From 0.2 MPa to 1.0 MPa, the extinguishing time decreases from 34 seconds to 4 seconds.

Research on the influence of driving gas types in compound jet on extinguishing the pool fire.

Compound jet fire extinguishing technology is an efficient technology for oil fires. The hydrophobic ultrafine dry powder is used for the solid phase in the compound jet, but it can't be supplied continuously due to the insufficient supply of compressed nitrogen. Thus, the feasibility of using the compressed air to replace the compressed nitrogen in the compound jet was explored. The key factor for the replacement, which influences the fire extinguishing efficiency, is the oxygen content in the contact point between the jet and the flame. Firstly, the oxygen content of the ultrafine powder jet driven by air or nitrogen were investigated by gas analyzer; Secondly, 150 L (liter) gas oil and 50 L water were put in a oil pan, the compared fire extinguishing experiments were conducted, the fire extinction time and the temperature drop range were investigated. In order to reveal the effect of ultrafine dry powder on oxygen content in gas jet, the experiment that spray the compressed nitrogen were conducted. The results show that there are not much differences for the two gases in extinguishing the pool fire, indicating that compressed air as the driving gas of the compound jet is feasible during fire extinguishing process.

Information and Analytical Support for Management of Fire Extinguishing at Highly Dangerous and Technically Complex Facilities

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Experimental Study on Fire Extinguishing Properties of Compound Superfine Powder

Abstract In this paper, the existing fire extinguishing powder was improved with magnesium hydroxide as additive to prepare the compound superfine powder. And the fire extinguishing performance of the compound powder was tested by the modified cup-burner, being compared with the commercial dry powder and the superfine powder. The advantages of the compound superfine powder were explained from the aspects of minimum extinguishing concentration, temperature and extinguishing time. The experimental results showed that the minimum extinguishing concentration of compound superfine powder was much lower than the other two, and the temperature drop rate was greater in the process of suppressing flame. Although the compound superfine powder was slightly lower than the superfine powder in the average extinguishing time, the standard deviation results showed that the composite powder had better stability. In addition, the experimental results showed that the fray-out of flame was very fast and the time only accounted for 17.5% in the fire extinguishing process.

Environment influences and extinguish technology of spontaneous combustion of coal gangue heap of Baijigou coal mine in China

This paper has tested the CO source of 2521 fully mechanized face through SF6 gas and contrapuntally made the comprehensive control technology based on loess cover, loess isolation and grouting slurry. In fire extinguishing process, loess isolation is used to prevent spontaneous combustion area from enlarging, loess cover reduces the air leakage in the spontaneous combustion area of Coal Gangue Heaps, and borehole grouting and trenching grouting reduce heat quantity of the spontaneous combustion area. According to the detection of spontaneous combustion field parameters, above technical measures have controlled the spontaneous combustion areas of coal gangue in Baijigou Coal Mine.

How to improve efficiency of using water when extinguishing fires through the explosive breakup of drops in a flame: Laboratory and field tests

The study reports results of the experimental research on the explosive breakup of heterogeneous water drops in high-temperature (800–1200 K) conditions typical for fires. The temperature of heating conforms to mean values for large forest fires. We use water drops containing special-purpose inclusions, such as 1–3 mm solid opaque particles (natural graphite). Laboratory experiments enable us to define conditions for the intensive fragmentation of such the drops. This process is characterized by formation of droplets of smaller size. The number of fragments can be from several ones to several hundreds. As a result, the evaporation surface area of liquid increases 3–15-fold during such the fragmentation. This effect is important for the most complete water evaporation in a flame during the fire extinguishing process. In such a case, the maximum temperature reduction in a flame zone becomes possible by absorption of heat of phase change. Field tests show that the usage of suspensions based on water facilitates a dramatic drop in temperature in a flame zone by 40–70 K as compared to water without additives. Consequently, fire extinguishing occurs during shorter time and by using smaller volume of water. Both the characteristics can decrease by 30–40% as compared to water without additives.

Active substances study in fire extinguishing by water mist with potassium salt additives based on thermoanalysis and thermodynamics

The active substances during the process of fire extinguishing by water mist with potassium salt additives was studied. The minimum extinguishing concentration (MEC) experiment results showed that K2CO3 have the most benefit in improving the fire extinguishing efficiency of pure water with the improving rate of 37.6%, 47.2% and 64.8% which the mass percent was 1%, 2% and 5%, respectively. Other potassium salt additives followed the order by: K2C2O4>CH3COOK>KNO3>KCl>KH2PO4, and the reason attributed to the different active substances decomposed from flame temperature by different kinds of potassium salt additives. Thermoanalysis and characterization of the pyrolysis products of potassium salt solutions at flame temperature were analyzed through TG-DSC, XRD, and SEM, the results showed the KOH was the main product in the high extinguishing performance of potassium salts in flame chemical reactions. Thermodynamics analysis by HSC CHEMISTRY showed the K2CO3 could provide 4.85% KOH in equilibrium substances, which well above other potassium salts, and other active substances good for fire extinguishing benefited from the intermediate product during the process of the KOH reacted with the flame free radicals.

Тактическое термографирование процесса тушения пожара устройством высокоскоростной подачи огнетушащего вещества

Тактическое термографирование процесса тушения пожара устройством высокоскоростной подачи огнетушащего вещества

ПРОГРЕССИВНЫЕ ТЕХНОЛОГИИ И СРЕДСТВА ТУШЕНИЯ ПОЖАРОВ НА НЕФТЕБАЗАХ

This article analyses challenges of the fire extinguishing process at fuel storage facilities and looks at modern technologies aimed at extinguishing burning petrochemicals, such as: subsurface foam injection, combined gas and powder fire extinguishing technology «BiZone», aerosol generator «Purga», automatic fire-fighting system USP-01F, foam generating substance «Storm», heat shields «Sogda» designed to protect firefighters from thermal radiation, etc. Recommendations are given to facilitate the use of advanced fire suppression technologies at fuel storage facilities.

Physical–chemical explanation of fire-fighting efficiency of FHF (fast-hardening foam) based on structured silica particles

Report is dedicated to thermophysical and chemical explanation of the ways of increasing the fire-extinguishing process of solid combustible materials. As a result of research such indicators are obtained as speed of extinguishing, specific consumption, $${I_{{\rm{FFE}}}}$$ (index of fire-fighting efficiency) with help of fast-hardening foam. Fire-extinguishing mechanisms of fast-hardening foam are considered and evidences of their positive features are given. Application areas of fast-hardening foam are pointed. At the Fig. 1 thermal insulating capabilities of the fast-hardening foam, which hinder the flame to impact on opened parts of body are clearly presented.

SIMULATION TESTS OF EXTINGUISHING PROCESS USING MIST NOZZLES WITH APPLICATION OF HYBRID FIRE MODEL

The article presents a computer model of the fire extinguishing process using mist nozzles. A previously developed hybrid fire model was used for this purpose. Assumptions and relationships were given to represent a math­ematical model of extinguishing process, which comprises a unique approach to the determination of sprinkling area in an elementary cell of field fire model. A description of simulation tests of the model was given for several different input data, differing by mean diameters of droplets. This enabled a study of their effects on such output parameters as received heat flux, temperature and rate of its growth. For one selected computational cell located on the axis of the nozzle at floor level having the coordinates [10, 10, 1], the obtained results were presented in the form of heat flux and temperature. To simplify the analysis, characteristic parameters of particular curves were listed in the table. Conclusions formulated on the basis of results obtained during tests were specified at the end of work. They confirmed the expected regularity assuming that the extinguishing process was more effective in the case of droplets of a smaller diameter and greater sprinkling intensity. This allows assessing the degree, to which these stream parameters affect the extinguishing effectiveness.

Influence of dispersion degree of water drops on efficiency of extinguishing of flammable liquids

Depending on the size of water drops, process of fire extinguishing is focused either in a zone of combustion or on a burning liquid surface. This article considers two alternate solutions of a heat balance equation. The first solution allows us to trace decrease of temperature of a flammable liquid (FL) surface to a temperature lower than fuel flash point at which combustion is stopped. And the second solution allows us to analyze decrease of burnout rate to a negligible value at which steam-air mixture becomes nonflammable. As a result of solve of a heat balance equation it was made the following conclusion: water drops which size is equal to 100 μm will completely evaporate in a zone of combustion with extent of 1 m if the flying speed of drops is even 16 mps (acc. to Stokes v = 3 mps); whereas drops of larger size will evaporate only partially.

Анализ типового соотношения для описания зависимости времени тушения горючих жидкостей и удельного расхода различных огнетушащих веществ от интенсивности их подачи

On the basis of analysis of experimental data on extinguishing of flammable liquids it is offered the model of extinguishing process which includes local interaction of the base of dispersed stream with part of a flame jet and further spreading of extinguishing layer on the burning surface of oil product. The basis of analysis is a dual suppression mechanism of fire extinguishing agents. The dual suppression mechanism is universal and is especially strongly revealed during extinguishing of flammable liquids by dispersed streams of water and freon, by stream of powder and air, by foam giving into the bottom of burning tank with oil product. The dual mechanism is accompanied by fact that the stream of agent carries away atmospheric oxygen that sharply increases volume of flame jet at the initial stage of stream supplying. Taking into account action of inflow of additional air we can reveal the nature of extreme dependence of specific consumption on flow rate of extinguishing agent and existence of its optimal flow rate during fire extinguishing. Material balance of extinguishing process of hydrocarbon flame using method of covering of the burning surface by layer of fire extinguishing agent (FEA) is considered. As a result, it was defined that the thickness of layer in the place where stream falls onto the burning surface depends on flow rate of dispersed stream. Dependence of average thickness of extinguishing layer on flow rate of stream is offered. Based on the results of experiment, conducted on specific model of extinguishing of gasoline flame using water with high dispersion degree, it was described dependence of specific consumption of FEA and extinguishing time on its flow rate. This allowed us to determine the optimal flow rate and the minimal specific consumption of dispersed water. The analysis of formulas, deduced during research, shows that multiplication of extinguishing time by corresponding value of flow rate of dispersed stream allow to obtain the extreme dependence of specific consumption of extinguishing agent on its flow rate. This effect was found in all experiments on fire extinguishing of hydrocarbons by dispersed water, dispersed freon or extinguishing powder. The analysis of extinguishing of gasoline flame by dispersed freon 114B2 and fire extinguishing powder is carried out. Process of extinguishing of a heptane flame by giving of foam onto the burning surface and into the layer of oil product is considered. It is shown that description of extinguishing process of diesel fuel due to giving of air into the bottom of tank reveal the reverse, as compared with dispersed water, situation. In case of application of dispersed water, extinguishing process is realized due to the steam layer which is formed as a result of evaporation of water drops. If extinguishing is realized due to the giving of air, its stream carries away the flow of liquid. As in the previous case, the initial value is a flow rate of air which carries out cold layers of oil product to the upper level. Suppression of flame will occur when the entire burning surface will be covered by hydrocarbon layer which temperature is lower than temperature of ignition. To describe the experimental results it is offered the formula which includes data of the process of fire extinguishing using foams formed from hydrocarbon agents and from fluorinated agents. Possibility of creation of the standard equation which describe dependence of specific consumption and extinguishing time on flow rate of extinguishing agents of different nature is shown. Possibility of determination of the optimal flow rate and the minimal specific consumption of fire extinguishing agent, irrespective of its nature, and possibility of application of the standard calculated ratio for description of the process of extinguishing as by dispersed streams, so by foam giving onto the burning surface and into the layer of oil product are shown.