Suppression Effectiveness Of Water Mist Research Articles

The Suppression Effect of Water Mist Released at Different Stages on Lithium-Ion Battery Flame Temperature, Heat Release, and Heat Radiation

Thermal runaway (TR) is a serious thermal disaster that occurs in lithium-ion batteries (LIBs) under extreme conditions and has long been an obstacle to their further development. Water mist (WM) is considered to have excellent cooling capacity and is widely used in the field of fire protection. When used in TR suppression, WM also exhibits strong fire-extinguishing and anti-re-ignition abilities. Therefore, it has received widespread attention and research interest among scholars. However, most studies have focused on the cooling rate and suppression effect of TR propagation, and few have mentioned the effect of WM on flame heat transfer, which is a significant index in TR propagation suppression. This study has explored the suppression effect of WM released at different TR stages and has analyzed flame temperature, heat release, and heat radiation under WM conditions. Results show that the flame extinguishing duration for WM under different TR stages was different. WM could directly put out the flame within several seconds of being released when SV opened, 3 min after SV opening and when TR ended, and 3 min for WM when TR was triggered. Moreover, the heat radiation of the flame in relation to the battery QE could be calculated, and the case of WM released 3 min after SV opening exhibited the greatest proportion of heat radiation cooling η (with a value of 88.4%), which was same for the specific cooling capacity of WM Qm with a value of 1.7 × 10−3 kJ/kg. This is expected to provide a novel focus for TR suppression in LIBs.

Study on the suppression of thermal runaway of lithium-ion battery by water mist with different additives

ABSTRACT Water mist with additives is a promising emergency control technology for the lithium-ion battery’s thermal runaway. Developing efficient, green, and environmental-friendly additive is a key issue to the technology. Here, using 18,650 batteries as the experimental object, three different suppression mechanism additives, i.e. sodium dodecyl benzene sulfonate (SDBS), sodium chloride (NaCl), and soy protein, were studied and discussed after optimizing the condition of water mist generated with different Here, using 18,650 batteries as the experimental object, three different suppression mechanism additives, i.e. sodium dodecyl benzene sulfonate (SDBS), sodium chloride (NaCl), and soy protein, were studied and discussed after optimizing the condition of water mist generated with different compressed air. The battery thermal runaway process concluded four stages, and the initial stage of explosion, i.e. the safety valve broke through companying with some noise and gases spilling out, was a typical phenomenon that suggested the beginning of thermal runaway. The water mist generated with optimized air pressure of 0.2 to 0.25 MPa, the droplet SMD size was 71–89 μm, could effectively suppress the battery thermal runaway, decrease T2 quickly from about 700°C to no more than 413°C, and reduce the cooling time from above 1000 s to no more than 203 s. Although the mechanism of the three additives was different, all of them could evidently enhance the suppression effect of water mist on the lithium-ion battery’s thermal runaway. Especially, the addition of 1.5% soy protein to water mist could decrease greatly both the flame temperature and the battery’s surface temperature, and shorten 63% cooling time comparing to the pure water mist. The results showed that soy protein was an efficient and environmental-friendly additive for water mist to inhibit the thermal runaway of lithium-ion battery and had good potential practical application value. The in-depth research and analysis of SDBS and NaCl would provide basis data for the development of compound additive.

Numerical simulation study on suppression effect of water mist on PMMA combustion under external radiant heat flux

Numerical model was built with fire dynamic simulator and theocratical simulation was carried out to investigate the suppression effect of water mist on ignition and combustion process of typical solid material polymethyl methacrylate under external radiant heat flux. Characteristic parameters such as ignition time, surface temperature, heat release rate and temperature distribution of flame central plane during ignition and combustion process under different thermal radiant fluxes were obtained and compared with experimental results. The suppression effect of spray droplets on ignition and combustion process was analyzed and discussed. The results show the theoretical calculations of combustion characteristic parameters are in good agreement with experimental measurements. Water mist droplets can effectively delay the ignition time. Quantitative data proves that the water mist flow rate at 0.9 L/(min·m2) can delay the ignition time of samples by about 1,100 s while the radiant heat flux is 50 kW/m2. The simulation results can provide theoretical support and data reference for typical solid material fire prevention and fire extinguishment in practice.

Experimental and theoretical study on the suppression effect of water mist containing dimethyl methylphosphonate (DMMP) on hydrogen jet flame

This work investigates the suppression effect of water mist containing dimethyl methylphosphonate (DMMP) on H2 jet flame. The flame appearances are analyzed and the flame temperature is recorded by a high-speed infrared camera. Results show that the suppression effect of water mist containing DMMP is better than that of pure water mist. To better understand the suppression effect of water mist containing DMMP, the burning velocity, heat production and free radicals are analyzed. Results indicate that suppressant could scavenge lots of free radicals to reduce the burning velocity in a wide range of equivalence ratios. Moreover, the influence of DMMP on lean CH4 and H2 flames is compared. Different with that of lean CH4 flame, the combustion parameters of lean H2 flame decline with DMMP addition. There is no combustion enhancement effect of DMMP on lean H2 flame. Because of the higher combustion intensity of lean H2 flame, the hydrocarbon in DMMP has little impact on the combustion. Furthermore, the reaction path of DMMP decomposition is analyzed. Results demonstrate that the rates of most phosphorus reactions in H2 flame are larger than that in CH4 flame. This work could provide foundation for improving the safety of hydrogen energy application.

Thermal runaway suppression effect of water mist on 18650-cylinder lithium-ion batteries with different cathode materials

Currently, the potential thermal runaway (TR) hazard of lithium-ion batteries (LIBs) has attracted widespread attention. Fortunately, water mist (WM) has proven to be an effective way to suppress TR in LIBs. This article mainly studies the TR characteristics and the WM suppression effects of three types of 18,650 cylinders with lithium iron phosphate (LFP), lithium cobalt oxide (LCO) and ternary nickel manganese cobalt (NMC) as the cathode materials. Based on the self-built platform, the TR suppression effect of pure WM and what with 5% NaCl additive by mass on three types of 18,650 cylinders at different state of charge (SOC) was explored. The results reveals that the WM containing NaCl additive possesses better inhibition effect of TR than pure WM; the WM has the best suppression effect on the LFP. However, WM cannot efficiently curb the TR of LCO and NMC at 100% SOC. Advancing the spraying time to the initial burst can effectively control TR of LCO and NMC at 66% and 33% SOC. The mechanism of WM to suppress TR is mainly reflected in cooling, diluting oxygen, affecting flames, and reacting with flue gas. In order to effectively inhibit the TR of LIBs, not only should a suitable TR inhibitor be selected, but also the timing of spraying should be considered. Only when both are the best choices, it is possible to control the TR hazard in the bud.

Numerical simulation of gas explosion suppression by ultrasonic water mist based on the Cloud, Fog, and Edge Computing

With the introduction of the concepts of “Internet Plus”, “Industry 4.0” and “Made in China 2025”, the development of the Internet and industry has begun to influence each other, and the development of the Internet industry has more and more significant effects on industry progress. The coal mine gas explosion accident in China has seriously threatened the life safety of miners, not only restricting the development of mine production, but also bringing a heavy burden to coal enterprises. Therefore, monitoring the concentration of CH4 and finding suppression materials are of great significance for preventing disasters. This paper is based on the Cloud, Fog, and Edge Computing to monitor the CH4 concentration that can cause gas explosions and uses a self-designed experimental device to verify the suppression effect of water mist on gas explosion.

Extinguishment of counterflow diffusion flame stabilized in turbulent airflow by polydisperse water mist

In the present study, the effect of turbulence on extinguishment of counterflow diffusion flame by polydisperse water mist was investigated experimentally. A counterflow methane-air diffusion flame was stabilized in the forward stagnation region of a porous cylinder. Water mist was supplied by a pressure-type atomizer. Uniform turbulence was produced in the airflow by a grid. Mist characteristics were measured by a phase Doppler particle analyzer and turbulence properties by a hot wire anemometer. For laminar flames, the critical stretch rate at extinguishment decreases with the mass fraction of water mist and the extinguishment is not affected by the Sauter mean diameter D32 even when D32 is as large as 70 µm. Turbulence reduces significantly the critical bulk (mean flow) stretch rate at extinguishment. Effect of turbulence on extinguishment is relevant to the turbulence stretch rate, which is the inverse of the Kolmogorov time scale. Sum of the bulk stretch rate and the turbulence stretch rate is the total stretch rate that actually exerts on turbulent flame. If the relative turbulence intensity v’/V is as low as 0.06 and D32 is smaller than 30 µm, extinguishment of turbulent diffusion flame is expressed uniquely by the total stretch rate, which coincides with that of laminar flame. On the other hand, for large water mist, D32 > 30 µm or high turbulence intensity, v’/V = 0.10, non-uniformity of mist dispersion appears, of which scale is of the order of integral scale of turbulence. The locally extinguished flame by a spot of dense water mist is reignited by surrounding flame and the suppression effectiveness of water mist is deteriorated when the turbulence intensity is high or the mist diameter is large.

Experimental evaluation of water mist with metal chloride additives for suppressing CH4/air cup-burner flames

In order to investigate the fire suppression effectiveness of water mist with metal chloride additives, ultrafine water mists of these salts with diameters about 10μm were introduced into CH4/air non-premixed flame in the cup burner. Results showed that these droplets hard to make itself to the flame front under the cup burner flow conditions functioned as a carrier of the vaporized solid particles or its decomposed materials. The metal chloride improved fire suppression efficacy of water mist which were affected by the type and concentration of metal chloride. On a mass basis, there is a fire suppression effectiveness relationship of MgCl2<CaCl2<NaCl<KCl<MnCl2<FeCl2. The flame suppression ability of water solution/metal chlorides improves as the concentration of metal chlorides increase. However, upper additive limits exist due to the associated limiting vapour pressure of the additive.

Comparison Tests Determine the Ratio between in the Constituent the Compound Additive and Experimental Study on Fire Extinguishing of Water Mist with this Multi-Component Additive

Abstract A new multi-component additive of water mist is produced through physics process, which can change the spray pattern of water by physical methods and the physical and chemical characteristics of water by chemical methods. Aiming at the main additive material (fluorine surfactant and urea), a laboratory-scale water mist system was built and a series of comparison tests were conducted in this system to determine the optimal ratio between in the constituent the compound additive. Then in order to study the effectiveness of the water mist adding this new multi-component additive in fire suppression, a series of tests were conducted for the typical fire (oil pool fires and wood crib fires). The comparison test results reveal that the optimal ratios of fluorine surfactant and urea are both 6%, and fluorine surfactant improves extinguishing performance by changing the physical properties of water mist and urea improves extinguishing performance by thermal decomposition. The experimental results also reveal that the fire suppression effectiveness of water mist is improved greatly by adding the multi-component additive. Finally, the suppression mechanism is discussed simply so as to find out the relationship between the multi-component additive and suppression effectiveness.

Experimental Study on Fire Extinguishing of Water Mist with a Newly Prepared Multi-component Additive

In order to enhance the fire suppression performance of water mist, a new multi-component additive of water mist is produced through physics process for the typical fire (oil pool fires and wood crib fires). To study the effectiveness of the water mist adding this new multi- component additive in fire suppression, a laboratory-scale suppression system was built and a series of tests were conducted in this system. The experimental result reveals that the fire suppression effectiveness of water mist is improved greatly by adding the multi-component additives, Along with increasing the amount of multi-component additives, the fire suppression time of oil pool fire drops rapidly, then increases slightly at some points; but the time of wood crib fire declines gently, then tends to become stable. Finally, the suppression mechanism is discussed so as to find out the deep relationship between the multi-component additive and suppression effectiveness.

Experimental Study of The Effect of Water Mist on CH4/Air Non-Premixed Flames

Abstract Water mist for fire suppression and control has received considerable attention as one of the potential methods for halon replacement. Spatially resolved information on volume mean diameter and coordinate component velocity of water mist has been obtained in two type fine mist, using LDA/APV System. A series of experimental study has been conducted to explore the CH4/air fire suppression effectiveness of water mist. The results show that Water mist consisting of 10-100 μm water droplets is an effective flame suppressant in a co-flow cup burner flame. The diameter and mass fraction of water mist significantly affects the temperature distribution of the methane CH4/air flame. The effect of oxygen dilution is more prominent in the upper part of the flame, whereas, endothermic heat exchange with the droplets plays a critical role in the lower half of the diffusion flame.

Experimental Study on Inhibiting the Gas and Coal Dust Explosion by Water Mist in Tube with Obstacle

The ordinary water mist has well affected on suppression and extinguishment flame, but the ability of physical extinguishment is influenced by the surrounding environment. The roadway in coal mine is very complex. So the related experiments need be considered. The light-sized experiment of the water mist is built for taking mine environment analog simulation with the pipeline. It is suppressed by medium pressure water mist the experiment of gas and coal dust explosion propagation in the alone laneway. Obstacle is laid on the different positions, whose blockage ratio is 30%. Then we compare the effects of suppression on gas flame with the different location. The experimental results indicate that the obstacle is placed in the front, middle and end of mist area. The propagation velocity of gas flame is different. The gas content and blockage ratio is set low in experiment. It can achieve better inhibition effect that the obstacle is placed in the middle or end of water mist area. Thus, if the obstacle can’t be avoided in water mist system, the designer must consider the position of obstacle. It can enhance the suppression effect of water mist.