Methane-air Explosion Research Articles

Analysis of fuel storage tanks under internal deflagrations with different venting technologies: an experimental and numerical study

This study investigates small-scale fuel storage tanks subjected to internal methane-air explosions, focusing on three depressurization technologies using roof ventilation to mitigate overpressure and damage. Tests with low methane-air concentrations were conducted to generate a pseudo-static internal pressure. This approach minimized scale effects and aligned internal pressure frequency with real-scale tank behavior during deflagrations. The first prototype features a tank with a frangible roof activated by localized brittle failure of stitch welds around the roof-to-shell junction. This confirms that stitched weld patterns ensure controlled brittle failure with activation pressure estimated by a simplified equation. The second technology employs a sequential ventilation strategy, starting with a small hinged panel followed by stitch weld failure, managing low to medium-intensity explosions with the small vent alone, and allowing rapid operational recovery. In severe explosions, the hinged door facilitates earlier activation of the frangible roof, reducing the initial pressure rise rate and controlling the roof opening direction. Lastly, the study explores tanks with commercial explosion vent panels as an alternative to traditional frangible roofs, offering a practical solution for retrofitting existing tanks. Each technology enhances safety in fuel storage facilities by effectively managing internal pressures during explosive events.

Inhibitory effect and mechanism analysis of modified coal gangue powder on the methane–air explosion

Inhibitory effect and mechanism analysis of modified coal gangue powder on the methane–air explosion

Dynamics of fuel-lean and stoichiometric methane-air explosion venting: Experiments and simulations

The computational explosion venting analyzer (EVA), a zero-dimensional (0D) model based on the conservation of mass and energy, is being developed to model centrally- and rear-ignited explosions. For this purpose, a series of explosion venting experiments in a cylinder with vent areas of 132.7, 86.6, 67.9 cm2 (corresponding to the vent area ratios of K=0.47,0.31,0.24, respectively) is performed. Two equivalence ratios of ϕ=0.8 and 1 are considered to represent the fuel-lean and stoichiometric methane-air mixtures, respectively. The dynamics of explosions is studied through the observation of flame propagation and pressure measurements. In rear ignition experiments, laminar, so-called “finger flame” propagation is observed, while in the case of center ignition, a flame initially expands spherically and then is pulled by the vent, acquiring a half-elliptical and half-spherical shape. The peak pressures obtained from rear ignition exceed their counterparts in the center ignition experiments. The EVA is compared with the experimental matrix. No turbulence is implemented in stoichiometric simulations, and slight turbulence has been accounted for in the lean mixture simulations. It is found that the large vent, generally, imposes more disturbances on the flame shape and the fuel-lean mixtures are more prone to the diffusional-thermal instabilities. It is shown that such a simple numerical tool, as the EVA is, can estimate a complicated problem such as pressure evolution resulted from a vented gas explosion.

A novel gel dry water: Preparation and application in methane-air explosion

To weaken the adverse effects of methane-air explosions on industrial processes and the environment, the development of highly effective explosion inhibitors is imperative. In this study, a novel ammonium polyphosphate gel dry water (AGDW) powder was synthesized by incorporating superabsorbent polymer (SAP) and ammonium polyphosphate (APP) as additives. The addition of SAP significantly enhanced the physical properties such as stability and water retention of AGDW powder, while APP improved its suppression effects. The suppression effect of AGDW powder on methane-air explosions was investigated in a square explosion pipeline. Experimental results revealed that 4 g AGDW powder with 15 wt% APP completely hindered the propagation of the explosion flame, resulting in a 91.2% reduction in peak temperature and completed elimination of the pressure reflection wave. Increasing the spraying pressure from 0.2 MPa to 0.4 MPa, 2 g AGDW powder with 5 wt% APP was sufficient to suppress the explosion completely. The suppression mechanism of AGDW powder on methane-air explosions was comprehensively elucidated from the cooling effect, diluting effect, and interrupting the chain reaction. This work sheds light on the preparation and application of novel dry water powders and provides a feasible solution for ensuring process safety and controlling gas explosions.

Experimental study on characteristics of flame propagation and pressure development evolution during methane-air explosion in different pipeline structures

A gas explosion experimental system based on a piece of 15 m-long and φ180 semi-closed wide open steel pipe was constructed. An explosion experimental study on straight pipelines and pipeline structures with different angles (45°, 90°, and 135°) was conducted. Research results demonstrated that before the turn, flame propagation speed and flame sustaining time in different pipeline structures were consistent. With the increase of the distance away from the ignition source, the flame propagation velocity increases and the flame sustaining time decreases; at the turning point, the flame velocity suddenly decreases and the flame duration increases obviously. Meanwhile, the peak value of overpressure on the lateral wall of the turning corner is greater than that on the inner wall. Among the three different angles, the peak value of overpressure on the lateral wall of 135° bend is the highest. Different pipeline structures have great influence on gas explosion overpressure and flame propagation speed. These research conclusions provide theoretical references for gas explosion resistance in coal mines.

Study on the propagation characteristics of methane-air explosion under the promotion of crushed gangue

Methane-air explosion is one of the major disasters in industrial process. The explosion strength could be influenced by the crushed coal gangue, which is widely distributed in coal mine gob and roadway. To understand the influence of the coal gangue on gas explosion, an experimental system with a 0.2 × 0.2 × 3.0 m3 pipeline was designed and explosion experiments of coal gangue with 5 blockage length-diameter ratios (ratio of axial blockage length to pipeline equivalent diameter) were carried out. The results show that coal gangue can cause significant disturbances to the flame front, resulting in a violent acceleration of the explosion flame. The overpressure ratio presents a negative exponential function distribution with the blockage length-diameter ratio. The influence range increases with the blockage length-diameter ratio under the condition of rich fuel, and reaches the maximum when equivalent ratio is 1.237. The explosion intensity is more sensitive to the blockage length-diameter ratio for the equivalent ratio equals 1.0 and 1.237. The formation of high-intensity explosion should be avoided by controlling the accumulation state of the overlying rock in coal mining.

Study on the effect of venting conditions on methane-air explosion characteristics in full-scale mine tunnel

The overpressure and heat products generated by methane explosions seriously threaten human life. Therefore, studying the influence mechanism of venting conditions on methane explosion characteristics in full-scale tunnels is of great significance for preventing and controlling methane explosions in mines. This study takes the Lynn Lake experimental mine (LLEM#501) as a background case, and studies the changes in methane explosion characteristics under different sealing ratios in full-scale tunnel using the GASFLOW-MPI code. The study shows that the greater the sealing ratio, the larger the maximum overpressure, maximum fluid velocity, and reflection wave overpressure in the methane explosion area. As the sealing ratio increases, the coupling effect of gas expansion and reflected shock wave overpressure causes a decrease in both the negative pressure value and the negative pressure area in the explosion zone. When the area is completely sealed, there is no formation of negative pressure. High-temperature heat products and flame backflow by cavity structures is the main factor that causes local temperature anomalies to increase and oscillations. Heat loss is a crucial factor influencing methane explosions, with approximately 22.75 % to 25.77 % of the explosion energy being dissipated in the form of heat during the explosion process. As the sealing ratio increases, the heat loss during the explosion process shows an exponential decrease trend. By analyzing the methane explosion energy equation, it has been determined that the decrease in heat loss during the methane explosion process is the primary cause for the increase in methane explosion overpressure and velocity.

Suppressive effects of alkali metal salt modified dry water material on methane-air explosion

As an abundant and efficient energy source, methane has a wide range of applications and development prospects, but it has a high explosion risk. In order to prevent the occurrence of methane explosion accidents, a new type of dry water material (DW) was used to suppress explosion, and alkali metal salts were added to improve the suppression effect. In this work, the optimal DW with complete monomer and uniform structure can be prepared by stirring nano-silica and deionized water at a mass ratio of 1:10 at a speed of 10000 rpm for 60S. The suppression effect of dry water was analyzed by performing methane-air explosion experiments with different powder concentrations in 20L explosion vessel. The results show that under the action of alkali metal modified DW, the Pmax and the deflagration index KG of methane-air explosion were significantly reduced. The improvement effect of potassium salt-dry water (PS-DW) ranked as KCl＞ K2CO3＞ K2C2O4·H2O＞CH3COOK, and the improvement effect of sodium salt-dry water (SS-DW) ranked as Na2CO3>NaCl > NaHCO3>NaH2PO4. Moreover, the explosion suppression mechanism of alkali metal salt modified DW was analyzed from four aspects: heat insulation, cooling, dilution and interruption of chain reaction. The study confirmed the important application potential of DW in preventing natural gas leakage explosion and coal mine gas explosion accidents. The optimal selection of modified additives in alkali metal salts holds significant importance for the widespread application of novel dry water composite materials.

Experimental study on the coupling effect of heptafluoropropane and different arrangement of obstacles on methane-air explosion

The influence of heptafluoropropane（CF3CHFCF3） with different barrier arrangements on the prevention of methane-air explosions in semi-closed pipes is examined in this research. Using high-speed photography and pressure sensors, the propagation traits and pressure data of flames were captured on the self-built explosion test platform. The findings demonstrate that, in the absence of barriers, a 1% concentration of CF3CHFCF3 promotes the spread of methane explosions, with an 8.6% reduces in flame propagation time. However, as CF3CHFCF3 concentration rises, the strength of the inhibition of methane explosions weakens with increasing concentration, and at a concentration of CF3CHFCF3 greater than 5%, the explosions are completely inhibited. When barriers of different arrangements are introduced, the inhibition impact of CF3CHFCF3 on methane explosion is improved. In these barriers, the maximum boosting rate and peak explosion overpressure are decreased by 28.81% and 97.27%, respectively. The staggered arrangement of barriers provides a higher coupling effect when the concentration of CF3CHFCF3 is between 1% and 3%, while the symmetrical arrangement of barriers has the optimum coupling effect when the concentration is between 4% and 5%.

Experimental study on suppression of methane-air explosion with different surface dispersants combined with modified attapulgite powder

This paper investigated the Inhibitory effect of attapulgite powder, modified attapulgite powder, and modified attapulgite powder after compounding by adding different types and different quality of surface dispersants to the explosion of methane-air premixed gas. A self-made semi-closed transparent pipe is the leading experimental platform in the research process. The maximum explosion overpressure, average pressure increase rate, and explosion power index under different working conditions are calculated by analyzing the pipeline's flame shape, pressure, and flame spread speed. Comparing methane explosion and adding attapulgite powder and modified attapulgite powder as explosion suppression materials, experiments were carried out, and the experimental results were compared and analyzed, which proved the inhibitory effect of modified attapulgite powder on methane explosion. Adding different qualities of sodium polyacrylate, ammonium hexametaphosphate, and sodium dodecyl benzene sulfonate as surface dispersants to the modified attapulgite powder. The effect of adding different dispersants on the ability of modified attapulgite powder to suppress the explosion of methane premixed gas was explored. Compared with the experiments of methane explosion, attapulgite powder, and modified attapulgite powder to suppress explosion, it is proved that after adding the above three surface dispersants, the modified attapulgite powder has better inhibition on methane explosion. The effect and the influence law and the corresponding inhibition mechanism are analyzed. The experimental results show that the modified attapulgite powder added with 120 mg of sodium dodecyl benzene sulfonate has the best suppression effect on the explosion of 9.5% pure methane-air premixed gas.

Study on Overpressure Explosion of Oil and Gas Pipelines and Risk Prevention & Control Measures

In view of the flammable and explosive characteristics of oil and gas pipeline transportation medium, once it leaks, production safety accidents are easy to occur. This study uses explosions with severe consequences caused by natural gas pipeline leakage as an example. The risk factors and accident modes of oil and gas storage and transportation pipelines are analyzed; the explosion load is calculated by a scaling explosion prediction model with the TNO multi-energy method; the relationship between overpressure load and combustible gas cloud radius is studied. The methane-air explosion volume fraction of 9.5% is taken as another example, with which the overpressure attenuation law of explosion wave is obtained. Based on the above research, safety risk prevention and control measures are proposed. The research results can provide technical support for daily management and risk prevention and control of oil and gas storage and transportation pipelines.

Effects of Abrupt Cross-Section Area Change on theMultiparameter Propagation Characteristics of Premixed Methane–Air Explosion in Pipes

This paper explores the effects of an abrupt cross-section area change of gas pipes on the propagation law of explosion. For this, an explosion pipe experimental system was established, and a numerical research was conducted. By experimental and numerical simulation, the evolution of the overpressure, temperature, vorticity, and kinetic energy of shock waves of gas explosion in abrupt pipelines was investigated. This allowed us to obtain expressions for the attenuation coefficient, increase coefficient, and reflection coefficient of gas explosion overpressure. The study indicates that an abrupt increase of the pipeline cross-section area leads to a decrease of shock wave overpressure and vice versa. For a given change of cross-section area, the attenuation coefficient gradually increases as the initial peak overpressure rises, whereas the increase coefficient and reflection coefficient both present a decreasing trend. An abrupt change in the pipe structure can inhibit the propagation of gas explosion flames. The explosive gas is affected by the turbulence effect after passing through the middle large-diameter pipe, and the vorticity curve exhibits a clear peak. In addition, the large eddy motion caused by strong confinement increases the kinetic energy of the gas in pipes. The above research outcomes contribute to further enriching the basic theory of gas explosion for the study of gas explosion propagation in mining laneway.

Effects of vent layout and vent area on dynamic characteristics of premixed methane-air explosion in a tube with two side-vented ducts

To further elucidate the influence mechanism of side vents on the dynamic characteristics of gas explosions in tubes is helpful to design more reasonable vent layouts. In this paper, 9.5% methane-air explosion experiments were conducted in a tube with two side-vented ducts, and the effects of vent layouts and vent areas on the dynamic characteristics of explosion overpressure and flame propagation speed were investigated. The results demonstrate that under the same condition with a single vent area of 100 mm × 100 mm, when only the end vent is open, the maximum explosion overpressure and the maximum flame propagation speed are the highest among the five vent layouts. When the side vents 1 and 2 and the end vent are open, the maximum explosion overpressure is the lowest, and an unusual discovery is that the flame front changes into a hemispherical shape, finger shape, quasi-plane shape, tulip shape and wrinkled structure. When only side vent 1 is open, a unique Helmholtz oscillation occurs, and a new discovery is that there is a consistent oscillation relationship among the overpressure, flame propagation speed and flame structure. Helmholtz oscillation occurs only when a single vent area is 100 mm × 100 mm–60 mm × 60 mm, and the oscillation degree decreases with decreasing vent area. During the vent failure stage, the maximum explosion overpressure is generated, the flame front begins to appear irregular shape, and the flame propagation speed shows a prominent characteristic peak. After the vent failure stage, the driving effect of the end vent on the flame is higher than that of the side vent on the flame. Furthermore, the correlation equations of the mathematical relationships among the maximum explosion overpressure Pred, the static activation pressure Pstat and the vent coefficient Kv under four vent layouts are established, respectively.

Effect of Vent Area on Dynamic Characteristics of Premixed Methane/Air Explosions in End-vented Channels with Different Length/Diameter Ratios

ABSTRACT Further elucidate the interaction mechanism of pressure-flame-wall in channels under the effects of length/diameter ratio (L/D) and vent area, which helps to propose more effective decompression means. Experiments of premixed methane-air explosions in end-vented channels with L/D of 10, 15 and 20 were conducted under initial conditions (301 ± 2 K and 1 atm). The results demonstrate that L/D and vent area are critical external factors causing tulip flames and distorted tulip flames. When the vent area is 60 mm × 60 mm~40 mm × 40 mm, the distorted tulip flame can be generated at L/D of 20. Notably, the critical intrinsic factor causing distorted tulip flame is the interaction of reflected pressure waves-flame. It is deduced that flames stagnate or decelerate during the initial stages of irregular flames because rarefaction waves attenuate the driving force of flames. The new overpressure peaks (Ptulip, Pdis-tulip, and Pirr-tulip) induced by tulip flames, distorted tulip flames and irregular tulip flames are identified. Moreover, the drop size and drop ratio of the maximum overpressure decrease with increasing L/D.

Investigation of the Suppression of Methane Explosions by N2/CO2 Mixtures in Different Proportions.

To characterize the inerting effect of N2/CO2 mixtures containing various proportions on methane-air explosions, a series of experiments were conducted in a 20 L spherical vessel under the normal temperature (25 °C) and normal pressure (101 kPa). Six concentrations (10, 12, 14, 16, 18, and 20%) of N2/CO2 mixtures were selected to analyze the suppression of methane explosion by N2/CO2 mixtures. The results indicated that the maximum explosion pressure (p max) of methane explosions was 0.501 MPa (17% N2 + 3% CO2), 0.487 MPa (14% N2 + 6% CO2), 0.477 MPa (10% N2 + 10% CO2), 0.461 MPa (6% N2 + 14% CO2), and 0.442 MPa (3% N2 + 17% CO2) in the presence of the same N2/CO2 concentration, and similar decreases in the rate of pressure rise, flame propagation velocity, and production of free radicals were observed. Therefore, with the increase of CO2 concentration in the gas mixture, the inerting effect of N2/CO2 was enhanced. Meanwhile, the whole process of the methane combustion reaction was affected by N2/CO2 inerting, which was mainly attributed to heat absorption and dilution of the N2/CO2 mixture. N2/CO2 with a greater inerting effect leads to lower production of free radicals under the same explosion energy and a lower combustion reaction rate at the same flame propagation velocity. The findings of the current research provide references for the design of safe and reliable industrial processes and the mitigation of methane explosions.

An overpressure-time history model of methane-air explosion in tunnel-shape space

This study investigated methane-air explosion in tunnel-shape space and developed an overpressure-time history model based on numerical results. The findings revealed that for the progressively vented gas explosion with movable steel obstacles in a 20 m long tunnel, the inner peak overpressure increased as the activation pressure of the tunnel top cover got higher but remained below 6 bar. However, as the activation pressure increased to 8 bar or higher, the peak inner overpressure remained unchanged. As the segment cover panel became wider, the peak pressure was almost unchanged, but the pressure duration and impulse declined significantly. The peak pressure and impulse increased as the tunnel length vary from 10 to 30 m. With fixed tunnel length, higher blast pressure but lower impulse was observed as the inner obstacles were closer or the activation pressure of obstacles was higher. It is also found that a local enlarged space in the tunnel enhanced the peak pressure significantly. An overpressure time history model for the tunnel with fixed top cover and enlarged end zone was established. The model considered activation pressure of vent cover, area and length of vent opening, methane concentration, number and blockage ratio of fixed obstacles was developed to calculate the overpressure and corresponding time at characteristic points of the pressure-history curve. The cubic Hermite interpolation algorithm and a specially tuned formula consisting of the power and exponential function were used to interpolate pressure values between characteristic points. The proposed model can predict both the peak pressure and the overpressure time history with acceptable accuracy.

Experimental study on CO2/CF3I suppression of methane-air explosion and flame propagation

To explore the inhibitory effects of CF3I and CO2 gas on the explosion pressure and flame propagation characteristics of 9.5% methane, a spherical 20 L experimental explosion device was used to study the effect of the gas explosion suppressants on the maximum explosion pressure, maximum explosion pressure rise rate and flame propagation speed of methane. The results indicated that with a gradual increase in the volume fraction of the gas explosion suppressant, the maximum explosion pressure of methane and maximum explosion pressure rise rate gradually decreased, and the time taken to reach the maximum explosion pressure and maximum explosion pressure rise rate was gradually delayed. At the same time, the flame propagation speed gradually decreased. Additionally, the time taken for the flame to reach the edge of the window and the time taken for a crack as well as a cellular structure to appear on the flame surface was gradually delayed. The fluid dynamics uncertainty was suppressed. The explosion pressure and flame propagation processes were markedly suppressed, but the flame buoyancy instability was gradually enhanced. By comparing the effects of the two gas explosion suppressants on the pressure and flame propagation characteristics, it was found that at the same volume fraction, trifluoroiodomethane was significantly better than carbon dioxide in suppressing the explosion of methane. By comparing the reduction rates of the characteristic methane explosion parameters at a volume fraction of 9.5%, it was observed that the inhibitory effect of 4% trifluoroiodomethane on the maximum explosion pressure was approximately 4.6 times that of the same amount of carbon dioxide, and the inhibitory effect of 4% trifluoroiodomethane on the maximum explosion pressure rise rate and flame propagation speed was approximately 2.7 times that of the same amount of carbon dioxide. The addition of 0.5%–1.5% trifluoromethane to 4% and 8% carbon dioxide can improve the explosion suppression efficiency of carbon dioxide. This enhancing phenomenon is a comprehensive manifestation of the oxygen-decreasing effect of carbon dioxide and the trifluoroiodomethane-related endothermic effect and reduction in key free radicals.

Experimental study on the coupling effect of heptafluoropropane and obstacles with different slits on the methane-air explosion

The comprehensive effects of obstacles with different slit and heptafluoropropane on the methane-air explosion characteristics were studied by visual explosion experiment platform. The volume fraction of heptafluoropropane and the number of slits of obstacles were considered. The results show that in the absence of obstacles, 1% concentration of heptafluoropropane accelerates flame propagation. When the concentration of heptafluoropropane is 3%, the explosion overpressure increases by 24.2%, and when 5% heptafluoropropane is used, the overpressure decreases by 10.6%. With the addition of obstacles, the coupling effect of the inhibitor and the obstacle improves the inhibition effect of heptafluoropropane. For obstacles with 2, 3, and 4 slits, 1% concentration of heptafluoropropane failed to significantly accelerate the flame propagation process under obstacle conditions. When the concentration of heptafluoropropane is 3%, the explosion overpressure increases by 9.5%, 5.4%, and 7.5%, respectively. The overpressure decreased by 18.7%, 25.7%, and 20.6% when 5% heptafluoropropane is added. The coupling mechanism significantly enhances the suppression effect of heptafluoropropane on methane explosion under various obstacle conditions.

Shockwave and dynamic pressure propagation law of methane–air explosion in full-scale pipe network

ABSTRACT Methane explosions are the main cause of coal mine disasters. Considering the scale effect involved in the process of methane explosion, small-scale methane explosion experiments can only obtain a qualitative trend of explosion parameters. It is necessary to study methane explosions in a full-size complex pipe network. In this study, the No. 501 experiment at the Lynn Lake Experimental Mine in the United States was used as the background case. GASFLOW-MPI was used to study the oscillation, attenuation, and dynamic pressure evolution laws of the explosion shockwaves in a full-size complex pipe network with consideration of the heat loss. The results showed that the numerical simulation results considering heat loss were more accurate than the adiabatic simulation results, and the average error of the peak pressure was only 4.25%. The pressure – time history curve of methane explosion shockwaves in a complex pipe network differed from that in a single pipe. The pressure peak was a bimodal curve near the explosion source, the dynamic pressure changes significantly, and both forward and reverse wind reaching 200 m/s occurred. The pressure curve far from the explosion source was a unimodal peak curve, and only the forward wind occurred. This reasonably explains the bidirectional deformation of rock bolted plates found in the US UBB accident. The results are expected to provide theoretical support for emergency mine rescue operations and mitigating the effects of methane explosions.

Explosion suppression range and the minimum amount for complete suppression on methane-air explosion by heptafluoropropane

A visual explosion test system consisting of a 20 L explosion vessel and a horizontal pipeline of 6.5 m in length was adopted. The effects of heptafluoropropane (CF3CHFCF3) on methane-air explosion pressure, explosion flame structure and propagation velocity under different spraying ranges and amounts were systematically studied, and the suppression mechanism of CF3CHFCF3 on the methane-air explosion was analyzed. The experimental results show that the spraying range and amount of CF3CHFCF3 have a significant impact on the methane-air explosion. The presence of CF3CHFCF3 can promote the propagation of methane flame and increase the flame brightness under certain conditions. The reasonable setting of the spraying range and amount of CF3CHFCF3 can significantly weaken the explosion pressure of various parts in the pipeline. In the case of the same spraying amount of CF3CHFCF3, a larger CF3CHFCF3 spraying range not necessarily achieves the better the explosion suppression effect. Experimental analysis shows that in this experimental system, the explosion suppression effect of different spraying ranges from strongest to weakest at 1.72, 2.32 and 1.12 m, the minimum spraying amounts that can prevent 9.5 % methane-air premixed gas in the explosion suppression zone explosion flame propagation are 300, 300 and 360 mL, respectively.