Extinguishing Performance Research Articles

Fire Extinguishing Performance Evaluation of the Downward Water Mist to Methane-Air Premixed Laminar Flame

Fire Extinguishing Performance Evaluation of the Downward Water Mist to Methane-Air Premixed Laminar Flame

Preparation of new gel foam and evaluation of its fire extinguishing performance

Developing a material that efficiently prevents spontaneous combustion of coal and can extinguish fire remains challenging. This research developed a gel foam that integrates the advantages of three fire-extinguishing technologies (i.e., foam, gel, and inert gas). The resistance and fire-extinguishing performance of this material were studied. The results show that a gel foam with compound foaming agent (sodium α-alkenyl sulfonate: fatty alcohol polyoxyethylene ether sodium sulfate = 8:4), gelling agent, and crosslinking agent concentrations of 0.7 wt%, 0.7 wt%, and 1.1 wt%, respectively, achieves excellent foam expansion ratio and foam stabilization performance. After treatment with this gel foam, the resistance rate and cross-point temperature of a coal sample increased by 61.72% and 9.1 ℃, respectively, and the low-temperature oxygen consumption decreased by 9.74%. Compared with the fire extinguishing performance of water and two-phase foam, this gel foam releases locked water and covers coal when extinguishing fire. The temperature and heat radiation of coal are effectively reduced, and re-ignition was not obvious after the fire had been extinguished. This shows that the developed gel foam has excellent fire extinguishing performance. • Gel foam integrates the advantages of foam, gel and inert gas. • The gel foam has a high foam expansion ratio and good foam stabilization performance. • Gel foam has excellent fire-extinguishing performance. • The preparation of gel foam is simple and low in cost.

The physicochemical and fire extinguishing performance of aqueous film‐forming foams based on a class of short‐chain fluorinated surfactants

AbstractAqueous film‐forming foams (AFFFs) are an important for fire extinguishing, and their key ingredient is fluorinated surfactant. In recent years, traditional long‐chain fluorinated surfactants have been banned by most countries because of their persistence, bio‐accumulation and toxicity. Therefore, increased attention has been paid to the research and development of short‐chain fluorinated surfactants. As is well known, the introduction of hydrophilic or hydrophobic groups in a surfactant affects its surface activity, and therefore, the fire extinguishing performance of AFFFs. In this work, a series of short‐chain fluorosurfactant‐based AFFFs with different hydrophobic chain lengths were prepared. The physicochemical performance of mixed systems (fluorinated surfactant plus sodium hexanesulfonate), including surface activity, spreading ability, foam expansion, drainage time, and the fire extinguishing and burn‐back performance of AFFFs were studied. The results show that the critical micelle concentration (CMC) and the surface tension (γCMC) at the CMC of mixed systems at 25°C are lower than 7.68 mmol/L and 16.51 mN/m, respectively. For mixed systems, the average spreading rate is more than 1.09 cm/s, the foam expansion is over 7.1, and the drainage time is greater than 3.28 min. The fire extinguishing time of AFFFs on fuels is less than 51 s while the burn‐back time is more than 15.18 min. The results imply a potential application prospect of the short‐chain fluorinated surfactants in AFFFs.

Numerical Study on Effects of Pipeline Geometric Parameters on Release Characteristics of Gas Extinguishing Agent

In order to guide the optimization design of the pipeline network of the aircraft-fixed gas fire extinguishing system and improve its fire extinguishing performance, FLUENT software was used to simulate the influence of pipeline parameters such as diameter, length, and roughness on the release characteristics of the fire extinguishing agent. It can be found that the extinguishing agent can be divided into liquid and vapor extinguishing agents in the fire extinguishing pipeline system during the release. The spatial distribution and proportion of the liquid and vapor extinguishing agents are asymmetric. Results show that the peak value of the pressure drop rate (dPmax) has a good quadratic function relationship with the pipeline diameter (D) and the functional relationship is dPmax=−22.224+2.782D+0.089D2, which means that the peak value increased significantly with the increase in the pipeline diameter. Moreover, when the pipeline diameter is 25 mm, the average pressure drop rate of the vessel is about 35.02 MPa/s, which is 5.97 times the value of the average pressure drop rate when the pipeline diameter is 10 mm. With the increase in the pipeline diameter, the release time decreases significantly, the mass flow rate increases obviously, while the gasification ratio decreases rapidly at first and then increases slightly. The pipeline length also has a significant influence on the release characteristics of the extinguishing agent. With the increase in the pipeline length, the release time and the gasification ratio increase linearly, while the mass flow rate decreases linearly. Compared with the pipeline diameter and pipeline length, the influence of the pipeline roughness on the release characteristics of the extinguishing agent is weak. With the increase in the pipeline roughness, the release time and the gasification ratio of the extinguishing agent increases slowly, while the mass flow rate decreases slowly.

Experimental study of the effectiveness of sands on extinguishing pool fires based on small sand-throwing equipment

In this paper, diesel, ethanol and n-heptane were used as fuels, sand was used as fire extinguishing material, and massive fire extinguishing experiments were carried out based on a small-scale sand-throwing equipment. A large number of throwing experiments were carried out on the equipment and the throwing performance of the equipment was tested. Based on the throwing experiments, a series of experiments of sand throwing to put out circular pool fire were carried out. Some indicators were measured and analyzed, including flame shape, flame temperature, fire extinguishing time and fire extinguishing mechanism. During the experiment, the flame intensification phenomenon and the " blow-off of flame " phenomenon was found. With the analysis of experimental data, covering the fuel to isolate combustibles and oxygen is considered to be the leading fire extinguishing mechanism of sand throwing to extinguish the pool fire. Sand has good coverage and suffocation performance, and the possibility of re-ignition after fire extinguishing is extremely small. The results of this paper are helpful to understand the experimental phenomenon and mechanism of sand throwing to extinguish pool fire, which provide a reference for the optimization of fire extinguishing performance of the equipment.

Research on Three Phase Signal Separation Method and Device for Live Detection of Circuit Breaker Contact Ablation Degree

A three-phase identification method and device for live detection of arc extinguishing performance of circuit breaker are proposed. In this paper, a sensor with three antennas is used to detect the electromagnetic wave radiated by the circuit breaker, and the three-phase identification is realized by controlling the receiving angle of the antenna and comparing the amplitude of the received electromagnetic wave. The method proposed in this paper has the technical advantages of simple implementation and low cost of detection device, and can realize the three-phase identification of live detection of circuit breaker arc extinguishing performance.

Comparison of fire extinguishing performance of four halon substitutes and Halon 1301

The Halon 1301 fixed gas fire extinguishing system used in ship engine rooms has been banned from production all over the world, because halon destroys the ozone layer. Therefore, it is necessary to find an environmentally friendly, compatible and efficient alternative firefighting system. In this study, we performed fire extinguishing tests in an ISO9705 standard room for four alternative fire extinguishing agents, as well as Halon 1301. The fire extinguishing efficiency of each agent was determined based on its cooling effect, dilution effect of oxygen concentration, the extinguishing time of the oil pool fire and the re-ignition probability of the wood stack. The test results provide data support for the selection of alternatives of Halon 1301 from the aspect of fire extinguishing efficiency. Among these results, Novec 1230 had the best ability to put out the oil pool fire, and HFC-227ea suppressed the wood stack fire the best. The difference between the cooling ability of each fire extinguishing agent was small, and the inert gas (IG-541) displayed the best ability to dilute oxygen. Hot aerosol required the longest time to extinguish fire. Consequently, under the existing design standards, HFC-227ea had the better firefighting efficiency, more suitable to replace Halon 1301.

Application techniques for micro capsules on energy security: A case study on Class B fire

At present, with the rapid development of the national economy, China’s demand for energy is becoming stronger. It is particularly important to develop an efficient and environmentally friendly fire extinguishing agent to ensure energy security. As a new type of environmentally friendly fire extinguishing agent, dry water has the advantages of both water mist and dry powder fire extinguishing agent. The core-shell structure of dry water fire extinguishing agent makes it have fluidity and dispersibility similar to powder fire extinguishing agent, while maintaining extremely high-water content, making it of great application value in the field of fire extinguishing agents. In this paper, the preparation, physical and chemical properties of dry water extinguishing agents and the fire extinguishing performance of Class B fires are studied, based on the existing fire extinguishing theories and experimental results, the fire extinguishing mechanism of dry water extinguishing agents is discussed.

Experimental and theoretical studies on the effect of Al(OH)3 on the fire-extinguishing performance of superfine ABC dry powder

A new type of dry powder fire extinguishing agent was prepared, which was called composite superfine dry powder with Aluminum Trihydrate (CSFP-ATH). The CSFP-ATH was characterized by laser particle size analysis, scanning electron microscope (SEM), thermal gravity analyzer (TGA), transform infrared spectroscopy(FTIR) analyzer and differential scanning calorimetry (DSC). The extinguishing performance of different samples was examined in a small-scale experimental platform for the liquid hydrocarbon fire. The tests were proved that the fire-extinguishing performance was as follows: CSFP-ATH > superfine ABC dry powder(SFP) > commercial ABC dry powder(CDP). Besides, the mechanism, kinetics and thermochemical changes in the reaction process were calculated by Gaussian simulation, and the reaction path of the CSFP-ATH with free radicals in the flame was predicted. Experimental and theoretical studies have been proved that the addition of Al(OH)3 can promote the fire extinguishing performance of superfine ABC dry powder.

Application of Sprinkler Head Discharge Obstruction in Semiconductor Factories

Semiconductor factories are significantly affected by the spray pattern of ceiling sprinkler heads owing to the large scale and complex mix of organic/exhaust ducts and multiple pipes. Therefore, sprinkler heads are installed in the spray disorder section of the lower barrier. However, more efficient installation measures are needed to mitigate the absence of detailed installation standards and interference with human and equipment transport lines. Currently, installation causes major confusion at construction sites and increases construction costs. The purpose of this research is to overcome these challenges by evaluating the operation status of sprinkler facilities in semiconductor factories, identify problems, and suggest more efficient installation measures. An installation plan that considers maintenance and fire extinguishing performance together is reviewed, and supported systematically with a relevant checklist.

Effects of Discharge Area and Atomizing Gas Type in Full Cone Twin-Fluid Atomizer on Extinguishing Performance of Heptane Pool Fire under Two Heat Release Rate Conditions in an Enclosed Chamber

In this study, the effects of discharge area and atomizing gas type in a twin-fluid atomizer on heptane pool fire-extinguishing performance were investigated under the heat release rate conditions of 1.17 and 5.23 kW in an enclosed chamber. Large and small full cone twin-fluid atomizers were prepared. Nitrogen and air were used as atomizing gases. With respect to the droplet size of water mist, as the water and air flow rates decreased and increased, respectively, the Sauter mean diameter (SMD) of the water mist decreased. The SMD of large and small atomizers were in the range of approximately 12–60 and 12–49 μm, respectively. With respect to the discharge area effect, the small atomizer exhibited a shorter extinguishing time, lower peak surface temperature, and higher minimum oxygen concentration than the large atomizer. Furthermore, it was observed that the effect of the discharge area on fire-extinguishing performance is dominant under certain flow rate conditions. With respect to the atomizing gas type effect, nitrogen and air appeared to exhibit nearly similar extinguishing times, peak surface temperatures, and minimum oxygen concentrations under most flow rate conditions. Based on the present and previous studies, it was revealed that the effect of atomizing gas type on fire-extinguishing performance is dependent on the relative positions of the discharged flow and fire source.

Environmentally Friendly Firefighting Foams Used to Fight Flammable Liquid Fire

The application of conventional aqueous film-forming foam (AFFF) has been restricted due to the environmental hazards caused by long-chain fluorocarbon surfactants. Environmentally friendly firefighting foams are urgently needed. In this study, AFFFs based on a long-chain fluorocarbon surfactant and a short-chain fluorocarbon surfactant, and fluorine-free foams based on a silicone surfactant and a mixture of foam stabilizers are prepared. The critical properties, including film-forming ability, foam stability, and foam spreading property, of foams and a commercial AFFF are investigated systematically. The fire extinguishing and burn-back performances are evaluated by a small-scale test method. Results indicate that the removal of fluorocarbon surfactants from AFFF leads to an apparent decrease in film-forming ability, foam stability, foam spreading property, and corresponding fire extinguishing performance. AFFF based on short-chain fluorocarbon surfactant shows excellent extinguishing and burn-back performances even if its film-forming ability, foam stability, and foam spreading are slightly worse than those of conventional AFFF. Although FfreeF cannot form an aqueous film and exhibits poor foam spreading, it demonstrates satisfactory fire extinguishing performance and optimal burn-back performance depending on its superhigh stability. This study can provide guidance in the development of environmentally friendly firefighting foams.

The influence of load type on electromagnetic wave radiation during the opening of circuit breaker

Radiated electromagnetic waves during the opening of the circuit breaker can be used to evaluate the arc extinguishing performance of the circuit breaker. Current research shows that the duration of electromagnetic waves is the main feature. However, the current research does not consider the influence of the type of load on the electromagnetic wave radiation during the opening process. In this paper, an experimental research platform is established, and the influence of the load type on the electromagnetic wave radiation during the opening process is studied by testing the resistance, inductance and capacitance loads. The research results show that the arcing time and visible arcing times of breaking capacitive loads are significantly greater than resistive and inductive loads.

Simulation and Experimental Analysis of DC Arc Characteristics in Different Gas Conditions

The structures of high-voltage direct current (HVDC) relays are compact. In order to extinguish the arc, the external magnetic field is applied near the contact. HVDC relays with a large capacity are also filled with gas medium to enhance the ability of arc extinguishing. The research on the characteristics of the arc in different gases under different pressures is of great significance to improve the reliability and the lifetime of the HVDC relays. The characteristics of the arc in nitrogen, hydrogen, and nitrogen–hydrogen mixtures and that of the arc root motion in the magnetic field are simulated by means of magnetohydrodynamics (MHD). The arcing processes in N2 and air are tested by a high-speed camera, and the arc root coordinates are calculated by the image processing method, and the simulation models are verified. The result shows that under the same condition, the hydrogen arc voltage is the highest, and the moving speed of the arc root is the fastest, so that the arc extinguishing performance of the hydrogen is the best. Nitrogen–hydrogen mixture is also a superior arc extinguishing gas, and the higher the proportions of H2, the better the performance. With the increase of the pressure, arc voltage increases. Except H2, increasing the pressure of the gas is beneficial for arc motion.

Experimental investigation on spray characteristics of twin-fluid nozzle for water mist and its heptane pool fire extinguishing performance

Water mist, which is an alternative to halon fire-extinguishing agents, can maintain the clean environments and prevent the huge fire loss in diverse industrial fields. In the present experimental study, the spray characteristics of a twin-fluid nozzle for water mist and its heptane pool fire extinguishing performance were investigated. As the spray characteristics, the SMD (Sauter Mean Diameter) of water mist, discharged water flux distribution, downward air flow velocity, and inlet pressures of fluids were measured and analyzed. Subsequently, through the fire extinguishing experiments using three different heat release rate conditions, the fire extinguishing map, extinguishing time, water consumption, and water mist effect on the mass loss rate were examined in detail. In addition, the experimental data using the twin-fluid nozzle were compared and discussed with those using the single-fluid nozzle reported in a previous study. Based on the present experimental data of fire extinguishments, particularly under high air flow rate conditions, the twin-fluid nozzle showed high fire extinguishing performance. Moreover, compared with a previous study using the single-fluid nozzle, it was found that the twin-fluid nozzle can successfully extinguish liquid pool fire with shorter fire extinguishing times, lesser water consumption, and lower inlet pressures. Based on the present results, it was found that the air flow of the twin-fluid nozzle is an important factor that determines and affects its fire extinguishing performance. Further, the twin-fluid nozzle was found to possess a significant potential to considerably improve the performance of water mist fire suppression systems.

Experimental Study on Thermosensitive Hydrogel Used to Extinguish Class A Fire.

Hydrogels are crosslinked polymers that become fully swollen when placed in aqueous environments. They are widely used in the field of firefighting because they can remarkably increase the viscosity and wettability of water. In this study, a thermosensitive hydrogel used to effectively suppress class A fire was synthesized by using methylcellulose, sodium polyacrylate, and magnesium chloride. The structure, surface activity and viscosity of the hydrogel were characterized. Fire extinguishing performance was evaluated based on small-scale and large-scale experiments. The results showed that a phase transition of the hydrogel occurred when the temperature rose from 50 °C to 80 °C. After the phase transition, the hydrogel showed a higher viscosity and lower surface tension, which was conducive to attach to the surface of the burning material and acting as an effective barrier to isolate oxygen. The small-scale fire extinguishing tests indicated that the concentration of the hydrogel solution has an eminent influence on fire extinguishing performance. The optimum concentration for extinguishing performance was around 6 wt%. The large-scale experiments demonstrated that the fire-extinguishing performance of this thermosensitive hydrogel was superior to the two other commercial water-based fire extinguishing agents, as it prevented re-ignition highly efficiently.

Flame‐retardant, phosphorous‐based polyurethane triazoles via solvent‐free and catalyst‐free azide–alkyne cycloaddition and their cure kinetics

A novel class of phosphorous‐containing polyurethane triazoles (PUTs) with self‐extinguishing property is reported. Initially, a set of new urethane diazide monomers were synthesized by reacting diisocyanates (DI) (isophorone (IPDI), hexamethylene (HDI), and toluene (TDI)) with 2‐azidoethanol and characterized by FTIR, 1H NMR, 13C NMR, and ESI‐MS analysis. Later, the corresponding PUTs were synthesized via azide–alkyne cycloaddition of urethane diazides with triprop‐2‐ynyl phosphate under solvent‐free and catalyst‐free conditions at 80°C via thermal polymerization. Cure kinetic study of the thermally induced polymerization of PUTs was performed to correlate with isocyanate functionality. The activation energies (Ea) of the PUTs derived from nonisothermal multiheating rate DSC tests were fitted to Borchardt–Daniels model. The Ea's were found to be proportional to heating rates for all PUTs and confirmed optimum percentage conversion at lower heating rates. The experimental findings were found to corroborate well with Borchardt–Daniels model. The PUTs were characterized by FTIR, TGA, DSC, MCC, LOI, lab‐scale flame tests, and EDX analysis. All PUTs were self‐extinguishable, but TD‐PUT with aromatic functionality (TDI‐based) demonstrated superior extinguishing performance with lowest total heat release (6.11 kJ/g), peak heat release rate (42.04 W/g), heat release capacity (85.59 J/g K), and 31% LOI comparatively. Lab‐scale flame tests on PUTs confirmed their self‐extinguishing property with little or no smoke evolution. Such PUT resins can be blended with conventional polyurethane coatings for fire‐retardant applications.

Fire Suppression of Gasoline Pool Fires Using Metal Oxide

Fire suppressants have a great role in controlling fire accidents, with the use of proper fire suppressants, the loss can be greatly reduced. Metal oxides can be used as fire suppressants. A new type of dry powders with capsular structure is to be fabricated for fire suppression, in which the content of water approached 60%. The capsules with the size of 3~5 μm consist of liquid core and solid shell, where the core is water droplet and the shell is assembled silicon dioxide particles with surface hydrophobic modification. Two different scaled real fire tests showed that thus-prepared solid powders could extinguish 0.21 MW gasoline pool fire in 2.0 s with agent mass of 0.055 kg, and 1.0 MW gasoline pool fire in 5.0 s with agent mass of 0.49 kg. Such fire extinguishing performance greatly outperformed the conventional mono ammonium phosphate (ABC) powders, neat silica powders and water mist, with significantly reduced fire extinguishing time and mass of agent consumed. Mechanism of the core-shell particles in fire suppression was discussed based on established theories and experimental results.

Fire extinguishing performance and mechanism for several typical dry water extinguishing agents.

In this work, four new dry water fire extinguishing agents (FEAs) were prepared by hydrophobic SiO2 and aqueous solution under certain conditions. The dry water FEAs were developed and we conducted two types of fire extinguishing experiments (i.e., class A solid fire and class B liquid fire test). Thermocouples and a color video camera were used to measure burning temperature and record the fire extinguishing process. Results indicate that the new dry water FEAs have the ability to extinguish A, B and C fires, and have a better cooling effect than dry powder FEA. It is noted, compared with traditional FEAs, that dry water FEAs have the advantages of high efficiency and high speed, and have a potential application prospect.

Study on the Compatibility of Eco-Friendly Insulating Gas C5F10O/N2 and C5F10O/Air with Copper Materials in Gas-Insulated Switchgears

Sulfur hexafluoride (SF6) is widely used in the power industry because of its excellent insulation and arc extinguishing performance. However, the high greenhouse effect of this material is being restricted by many countries around the world, thereby discouraging its usage. As a potential alternative to SF6, the compatibility of C5F10O with conductive copper materials used in electrical equipment is of great significance in ensuring the safe and stable operation of environmentally friendly gas-insulated equipment. In this paper, the interaction among C5F10O/N2, C5F10O/air gas mixture, and copper was studied via experiments and simulations. When the C5F10O/N2 (or air) gas mixture comes in contact with copper at the gas–solid interface, a small portion of C5F10O is decomposed to form C3F6 (or C3F6 and C3F6O) at high temperatures. Meanwhile, at low temperatures (120 °C), the C5F10O/air gas mixture becomes more compatible with copper than with the C5F10O/N2 gas mixture. When the experiment temperatures range between 170 °C and 220 °C, the compatibility of the C5F10O/air gas mixture with copper is significantly inferior to its compatibility with copper. Under high temperatures, the C5F10O/air gas mixture shows severe corrosion on the copper surface due to the presence of O2, forms a thick cubic grain, and emits irritating gases. The simulations show that the carbonyl group in C5F10O is chemically active and can be easily adsorbed on the copper surface. An anti-corrosion treatment must be performed on copper materials in manufacturing equipment. The findings provide an important reference for the application of C5F10O gas mixture.