Explosion Overpressure Research Articles

Study on gas explosion propagation law in excavation roadway with TBM

Gas explosion is one of the five major hazards in mines, with about 36% of such incidents occurring in the excavation working face. Therefore, to investigate the impact of gas explosion propagation laws within excavation roadways, we conducted a simulation analysis of parameters such as peak of explosion overpressure, peak rate of pressure rise, and flame propagation speed in the presence of a Tunnel Boring Machine (TBM). In the presence of the TBM, the explosion overpressure approximately doubles, and the flame propagation speed also greatly increases, exacerbating the explosion hazard. Thus, when investigating gas explosion laws within excavation roadways, the presence of a TBM emerges as a significant factor that cannot be overlooked. Furthermore, an analysis of the effects of methane concentration and gas accumulation length on explosion parameters was conducted. The results indicate that when the flame passes through the TBM baffle, the average flame propagation speed increases the most when the methane concentration is 9.5%, increasing by about 6 times. In addition, as the gas accumulation length increases, both explosion overpressure and flame propagation speed gradually increase. Additionally, TBM has a certain impact on flame propagation and methane dissipation.

Experimental study on inhibiting methane-coal dust explosion by APP-diatomite composite explosion suppressant in the pipe network

To prevent and control the methane/coal dust compound explosion disaster, the APP-diatomite composite powder inhibition of methane/coal dust compound explosion experiments were carried out in the self-constructed pipe network. The composite powder was characterized by scanning electron microscopy and X-ray photoelectron spectroscopy. The change rules of methane/coal dust composite explosion pressure and flame propagation velocity were analyzed using different compounding ratios of powders in several monitoring points. The results show that the composite powder exhibited irregular morphology and the APP powder is uniformly distributed on the diatomite porous mesh structure. When the APP loading on the surface of diatomite is 40 wt%, composite powder has the best effect on explosion suppression, with the peak maximum explosion overpressure and the peak maximum flame propagation velocity reduced by 71.5% and 92.2%, respectively. The explosion suppression mechanism is revealed through pyrolysis properties, explosion products, and chain reaction.

Research on the dynamics of flame propagation and overpressure evolution in full-scale residential gas deflagration

To determine the effect of ignition height on indoor flame spread behavior and overpressure development, a comprehensive full-scale deflagration testing facility was established. Extensive experimental research was conducted within this facility. The findings indicate that indoor flame reignition and the occurrence of secondary explosions are most pronounced with intermediate ignition. Furthermore, the explosion overpressure generated during the reverse turn of shock wave propagation is greater than that produced by the forward turn. In comparison to the peak overpressure Pext in the master bedroom for top, middle, and bottom ignition, the peak overpressure Pext in the second bedroom increased by approximately 14.48 %, 15.04 %, and 19.20 %, respectively. When comparing middle ignition to top ignition, the propagation speed of shock waves in the kitchen balcony, restroom, second bedroom, and master bedroom was enhanced by 34.21 %, 40.85 %, 40.70 %, and 34.65 %, respectively. Furthermore, when comparing middle ignition to bottom ignition, the propagation speed of shock waves in these areas experienced a significant increase of 126.32 %, 124.39 %, 123.26 %, and 113.86 %, respectively. These research findings provide a theoretical foundation and empirical data to support the investigation and analysis of the causes of indoor gas explosion incidents.

Study on the hydrogen-air premixed flame propagation characteristics in semi-open space with obstacle

In semi-open space, obstacles have the potential to accelerate flame propagation and increase hydrogen-air deflagration pressure. Therefore, this paper is dedicated to exploring the influence of obstacles on the premixed hydrogen deflagration, which is crucial for enhancing the safety of industrial production and energy utilization. By using Large Eddy Simulation (LES) model in OpenFOAM, this study investigates the deflagration characteristics of premixed hydrogen in the presence of three different shaped obstacles. The analysis results reveal that under obstacle conditions, the flame shape can be categorized into four phases: the hemispherical phase, finger-shaped phase, jet phase, and vortex phase. The velocity of the flame front is nearly same for elliptical and rectangular obstacle condition, but it is 36% higher compared to triangular obstacle condition. The impact of triangular and rectangular obstacles on explosion overpressure is less than that of triangular obstacles on explosion overpressure, but it is 16% higher than that of elliptical obstacle. Analyzing the vorticity generated by different obstacle reveals that the vorticity produced by rectangular obstacle is twice as much as that produced by elliptical obstacle, whereas the vorticity produced by triangular obstacle is 2.4 times greater than that produced by elliptical obstacle. The acceleration of hydrogen-air explosion process occurs due to the narrow space created by obstacle and pipeline walls, and the shape of obstacle significantly influences this acceleration.

Dispersion and explosion characteristics of multi-phase fuel with different charge structure

The fuel dispersion and explosion laws are important for safety design of fuel charge, concentration prediction of accidental release vapor cloud and prevention of fire and explosion accidents. The charge structure is an important factor in determining the fuel dispersion and explosion performance. Experiments and numerical simulations are carried out for cylindrical, square and fan-shaped charge structures. The dispersion process, concentration distribution, explosion overpressure, component reaction and safety radius of 11 kg solid-liquid-gas propylene oxide (PO) are obtained. The results show that square and fan-shaped structure have local enhancement effect. Compared with cylindrical structure, the dispersion distance of square at 0° and fan-shape at 45° increase by 10.13 % and 14.39 % respectively. The peak overpressure increased by 8.85 % and 4.73 %. At 4 m, the remaining fuel of the three structures is 39.13 %, 22.34 % and 17.20 %, respectively. The equivalent safety radius is 14.20 m, 14.80 m and 14.27 m respectively.

Numerical investigation of premixed syngas/air flame evolution in a closed duct with tulip flame formation

In this study, the dynamic behavior of the premixed syngas/air flames in enclosed ducts with obstacles at the blockage ratio of 0.5, as well as without obstacles, was studied via large eddy simulation and the turbulent flame speed closure model. The hydrogen volume fraction (hydrogen content in fuel) was set to 50 %. Results indicate that the simulation reproduced the flame shapes, flame speed and explosion overpressure observed in the experiments. In cases without obstacles, a “tulip” flame with a tulip cusp can be seen, and secondary cusps emerge on tulip lips due to the high-pressure zone ahead of “tulip” flame lips, leading to in a distorted “tulip” flame. In cases with obstacles, the flame develops hemispherical and finger shapes upstream of the obstacles and evolves into a “tulip” flame downstream of the obstacles due to vortices and adverse pressure gradients. The alteration of the flow direction within the unburned and burned zones results in intricate flame shapes. Flame speed and overpressure show a close relationship and exhibit oscillations following the generation of the “tulip” flame. Typically, the velocity, pressure and flow fields adjacent to the flame front can affect dynamic behaviors of premixed syngas/air flames.

Vulnerability assessment of buildings adjacent to natural gas pipelines under explosion accident

ABSTRACT Natural gas pipeline leak may lead to explosion accidents, which may threaten the safety of the adjacent buildings. This paper conducts a vulnerability assessment of buildings adjacent to natural gas pipeline under explosion, which is implemented by Copula Bayesian network (CBN) model. The incident escalations and evolution nodes were identified based on the accident reports. The correlation between nodes is calculated using the Kendall correlation coefficient to develop a CBN model of natural gas pipeline accidents. The weaknesses in the buildings adjacent to pipelines are identified using spider diagrams. The vulnerability of building adjacent to pipelines is characterized by the damage degree. The model is verified by a case study. The results indicate that the occurrence probability of the explosion accident reaches 85%. The identified weaknesses are ignition sources and confined spaces. The occurrence probability of a delayed ignition within buildings is 0.23, and the explosion overpressure is estimated to be 84.25 kPa. The vulnerability degree of building 1 is higher than building 2. These findings can help to understand the system weaknesses and support the safety improvement of buildings in the case of natural gas pipeline explosion.

Flame propagation, explosion hazard, and pollutant emission characterization of typical clean fuels leaks in plateau low-pressure region

To accelerate energy transformation and sustainable development, various countries are rushing to lay hydrogen doped natural gas pipelines. However, the installation of pipelines will pass through plateau low-pressure region, and the impact of low-pressure environments on the flame propagation, explosion hazards, and pollutant emission characteristics of hydrogen doped natural gas is not yet clear. To solve this problem, a combination of constant volume combustion experiment and numerical simulations is used. The characterization parameters of flame, explosion and pollutant concentration of natural gas/H2/air under low-pressure environment are obtained, and their chemical reaction kinetics are analyzed. When the pressure drops, the laminar burning velocity (LBV) of them increases, and the Lewis number (Le) gradually increases by more than 1. Thermal diffusion is stronger than mass diffusion, and the growth rate of flame thickness exceeds 26 %. The effect of hydrodynamic instability enhances, causing an increment in the average size of flame cells, the critical instability radius, and the Markstein length (Lu). At the equivalent ratio (φ) of 1, there is a change from negative to positive in the Lu, and flame stability continuously strengthens. The explosion overpressure is reduced by 78 % to 90 %, the explosion temperature by 16 % to 20 %. As the φ increases, the LBV exhibits an inverted U-shaped relationship, reaching its maximum value near “φ = 1″. The flame stability first weakens and then strengthens. The explosion hazard is strongest in the range of ”φ = 1–1.2″. With a decrease in pressure, the total reaction rate of fuel consumption is reduced by more than 50 %. The continuous reaction distance is extended by 12 %. Changes in pressure have a relatively weak impact on the content of CO and CO2. The increase in the φ results in an increase in CO content of over 7 %. The content of CO2 reaches its maximum value around “φ = 1″. It is an essential reference for the safe delivery of hydrogen energy and the reduction of environmental pollution.

Influence of the shape and number of obstacles on the excitation effect of dust-containing gas explosion

To investigate the excitation effects of different shapes and quantities of obstacles in dust-containing gas explosions, this study utilized an Euler-Lagrangian model. This model simulated explosions involving dust-laden gas, applying various governing equations to address the roles of coal dust at different combustion stages and its dynamic forces within the flow field. The research examined a 9.5 % gas concentration explosion with 5 g/m3 coal dust in a straight pipeline, assessing the impacts of spherical, regular tetrahedral, and cuboidal obstacles, as well as combinations of 1–3 cuboidal obstacles and three differently shaped obstacles on the explosion's flow field structure, overpressure, and flame propagation speed. Key findings include: dust-containing gas explosions result in more complex flow field structures, and the excitation effects of coal dust and obstacles on flame propagation speed exhibit mutual inhibition. Obstacles increase the maximum overpressure locally without affecting the overall trend of increasing overpressure with distance in closed conduits. Cuboidal obstacles show the most pronounced excitation effects, followed by regular tetrahedral and spherical obstacles, respectively. The number of obstacles also progressively enhances their excitation effects. When three obstacles of different shapes are present, cuboidal and regular tetrahedral obstacles primarily affect the flow field structure, with flame propagation speed and maximum explosion overpressure slightly lower compared to the presence of three cuboidal obstacles alone. These findings offer valuable insights into the destructive effects of gas explosions and the excitation effects of obstacles, providing theoretical support for disaster prevention and recommendations for underground equipment design and layout.

An review of research on liquid hydrogen leakage: regarding China’s hydrogen refueling stations

Hydrogen is regarded as the premier energy source for future sustainability and renewability. However, its distinct physicochemical properties render it prone to explosions in the event of a leak. Therefore, there is a need for more comprehensive research dealing with hydrogen leakage, explosion scenarios, and risk assessment. This paper provides an overview of the current hydrogen policies adopted in China. It reviews the processes of hydrogen refueling station construction and the thermophysical mechanisms of liquid hydrogen leakage. In this regard, the effects of various factors, including leakage rate, leakage time, leakage hole size, wind direction and speed, and building location, on the hydrogen leakage rate are analyzed and evaluated. Additionally, the impacts of different factors on hydrogen explosion overpressure are reported, including hydrogen concentration, wind speed, obstacles, and ignition position, in addition to the current applications of quantitative risk assessment methods in hydrogen refueling stations. Finally, the limitations of current research on liquid hydrogen leakage and explosion accidents are highlighted, along with the shortcomings of current risk assessment methods for liquid hydrogen refueling stations.

Numerical Study on Explosion Risk and Building Structure Dynamics of Long-Distance Oil and Gas Tunnels

To comprehensively understand the explosion risk in underground energy transportation tunnels, this study employed computational fluid dynamics technology and finite element simulation to numerically analyze the potential impact of an accidental explosion for a specific oil and gas pipeline in China and the potential damage risk to nearby buildings. Furthermore, the study investigated the effects of tunnel inner diameter (d = 4.25 m, 6.5 m), tunnel length (L = 4 km, 8 km, 16 km), and soil depth (primarily Lsoil = 20 m, 30 m, 40 m) on explosion dynamics and on structural response characteristics. The findings indicated that as the tunnel length and inner diameter increased, the maximum explosion overpressure gradually rose and the peak arrival time was delayed, especially when d = 4.25 m; with the increase in L, the maximum explosion overpressure rapidly increased from 1.03 MPa to 2.12 MPa. However, when d = 6.5 m, the maximum explosion overpressure increased significantly by 72.8% from 1.25 MPa. Evidently, compared to the change in tunnel inner diameter, tunnel length has a more significant effect on the increase in explosion risk. According to the principle of maximum explosion risk, based on the peak explosion overpressure of 2.16 MPa under various conditions and the TNT equivalent calculation formula, the TNT explosion equivalent of a single section of the tunnel was determined to be 1.52 kg. This theoretical result is further supported by the AUTODYN 15.0 software simulation result of 2.39 MPa (error < 10%). As the soil depth increased, the distance between the building and the explosion source also increased. Consequently, the vibration peak acceleration and velocity gradually decreased, and the peak arrival time was delayed. In comparison to a soil depth of 10 m, the vibration acceleration at soil depths of 20 m and 30 m decreased by 81.3% and 91.7%, respectively. When the soil depth was 10 m, the building was at critical risk of vibration damage.

Quantitative risk assessments of hydrogen blending into transmission pipeline of natural gas

Recently, considerable attention has been paid to blending hydrogen with natural gas transmission pipelines. However, risk assessments using different hydrogen blend concentrations in natural gas pipelines have not been thoroughly investigated. Thus, the main objective of this study is to carry out a quantitative risk assessment of hydrogen blending into the transmission of natural gas. For this, six different concentrations of hydrogen blending, three pipes and four different release holes are used in this study. The effect distance decreased with increasing hydrogen concentration for the jet fire case. For case of vapor cloud explosions, the downwind distance of the maximum explosion overpressure increased with increasing hydrogen concentration. It was also found that as the hydrogen concentration increased, the individual risk was sensitive to adjacent to the pipelines, however, it was less for far-fields. This study is expected to contribute to the safety measures for business sites with hydrogen blending into natural gas pipelines.

Experimental Study on Explosion Characteristics and Consequences for Homogeneous and Inhomogeneous Methane-Air Mixtures within a Kitchen

ABSTRACT Owing to the effect of a non-uniform concentration distribution, natural gas leakage explosion accidents usually cause different degrees of damage inside residential kitchens. According to the similarity principle, a reduced-scale experiment setup of a kitchen was established. Uniform and non-uniform explosion experiments for methane-air mixtures with concentrations of 7.7%, 9.5%, and 11.2% were performed. The flame propagation behavior and pressure evolution characteristics were analyzed for homogeneous and inhomogeneous methane-air mixtures. In addition, two dimensionless coefficients, namely macroscopic and directional non-uniformity coefficients, were introduced to quantify the uneven distribution of gas concentration within the kitchen. Furthermore, the flame development process and pressure evolvement characteristics were compared between homogeneous and inhomogeneous methane-air mixtures in a fuel-lean, chemical equivalence concentration and fuel-rich state. The results show that the macroscopic non-uniformity coefficients are 0.0998, 0.0653, and 0.0571 on the fuel-lean, chemical equivalence concentration and fuel-rich conditions, respectively. It indicates that the greatest non-uniformity of methane concentration distribution within the kitchen is represented on the fuel-lean condition. The concentration gradient could obviously reduce the explosion overpressure in the fuel-lean condition, whereas it would not significantly decrease the explosion overpressure in the chemical equivalence concentration or fuel-rich condition. It means that the greater the non-uniformity coefficient is, the more significant the effect on the overpressure peak is.

Effects of position layout and length gradient of two side ducts of on methane/air explosion in a tube

ABSTRACT In order to examine how two side ducts affect the dynamic behavior of a gas explosion in a tube, two side ducts were added to a tube containing a mixture of 9.5% methane and air. An experiment was conducted to release the explosion pressure and study how the position and length gradient of the side ducts influence the explosion’s overpressure and the speed at which the flame spreads. Based on the data, it was found that the most effective pressure release occurred at a length of 0.2 m for the front side duct and 0.1 m for the end side duct. Additionally, the greatest explosive overpressure recorded was 2.54 kPa. A double driving effect was created between the two side ducts when they were put in the front and middle and the middle and end locations. This increased the flame propagated speed. The greatest acceleration effect on the flame front occurred at 0.2 m of side duct length. When the two side ducts were placed at the front and end of the tube, the length gradient did not have any impact on flame propagation. Instead, it was predominantly the length of the front side duct that controlled flame propagation. The pressure relief effect was more pronounced when the two side ducts had a downward gradient; however, it was affected by the length of the end side duct. A relationship equation was established between the lengths of the two side ducts (d 1 and d 2), positioned at the front and end locations, and the maximum flame velocity (Vmax). The analysis results of the impact of different positioning layouts and length gradients of two side ducts on flame propagation and pressure release within the tube were instrumental in ensuring the safety of personnel, equipment, and environment during energy utilization processes.

Consequence analysis of vapour cloud explosion from the release of high-pressure hydrogen storage

Gaseous hydrogen is commonly stored under high pressures due to its low volumetric storage density. The safety concerns about its release and potential accidents, such as vapour cloud explosions, were of the highest importance in industries. This research work established a methodology for consequence analysis of compressed hydrogen releases, considering various stages of event escalation, including high-pressure gas release, gas jet dispersion, and overpressure evaluations. Specifically, compressed hydrogen release was defined as an under-expanded flow, characterised by a transition from sonic to supersonic velocities. The notional nozzle theory was employed to tackle the flow regime transition and provide revised nozzle size and gas velocity as inputs to the CFD model for gas jet dispersion. The model was validated against experimental results, exhibiting a good agreement with a deviation of less than 20%. The flammable gas mass in the cloud was determined using the dispersion model and then used for overpressure predictions. This approach proved to be more realistic than relying solely on the total hydrogen release amount. In a case study, release parameters such as release direction, wind speed and release hole size were investigated. It was observed that a downward release resulted in less gas dissipation, leading to larger overpressures compared to other release directions. Wind speed had a relatively lower impact compared to other parameters. The release hole size had the most significant influence on explosion overpressure, with the case of a larger release size (e.g., 50.8 mm) exhibiting a few hundred times higher of hazardous area compared to a small hole size (e.g., 3 mm).

Flameless venting characteristics and design model of micro-nano PMMA dust explosion

The effects of Fe–Ni foam thickness and dust size on flame propagation, reduced overpressure, and venting efficiency in 30 μm and 150 nm polymethyl methacrylate (PMMA) dust explosions were investigated. The flame quenching mechanism was revealed by coupling the heat transfer and flow of the dust flame within the Fe–Ni foam. It is found that micron dust is more prone to quenching than nano dust, and the differences in the quenching process of micro-nano dust are explained by combining the dust combustion kinetics and the theory of inter-particle heat transfer. The pressure venting mechanism of micro-nano dust was analysed under different thicknesses of Fe–Ni foam, and the thermal expansion effect of the flame passing through the Fe–Ni foam and its flow resistance significantly increased the reduced explosion overpressure. The flow continuity of the micro-nano dust was classified by means of the Knudsen number (Kn), which elucidates the effect of dust size differences on the pressure evolution. A prediction model for the maximum reduced explosion overpressure is proposed based on the explosion pressure venting of micro-nano dust. Changes in vented pressure have a direct impact on the efficiency of flameless venting. Nano-dust has an efficiency of more than 20 % lower than that of micron dust.

Effects of equivalent ratio and initial temperature on the explosion characteristics of ethanol, acetone, and ethyl acetate

In this paper, the effects of equivalence ratio (0.8–2.0) and temperature (30°C–120°C) on ethanol, acetone, and, ethyl acetate vapors explosion characteristics through experimental and numerical studies were investigated. The explosion overpressure and flame propagation velocity were recorded through the pressure transducer and high-speed camera. The results showed that the flame propagation velocity, peak explosion overpressure, and peak growth rate of explosion overpressure increased first and then decreased with the increase of equivalence ratio. The cracks on the flame surface enhanced with the increase of the equivalence ratio. As the initial temperature increased, peak explosion overpressure, the flame propagation velocity, and peak growth rate of explosion overpressure gradually increased. The sensitivity analysis of laminar burning velocity indicated that with the change of equivalence ratio and initial temperature, the shared elementary reactions that increased the reactivity were H + O2 <=> O + OH, HCO + M <=> H + CO + M, and CO + OH <=> CO2 + H, and the shared elementary reaction that reduced the reactivity was H + OH + M <=> H2O + M. The main factor affecting laminar burning velocity was the mole fraction of H and OH radicals.

Numerical simulation study on explosion characteristics of large vault tanks with different height-to-diameter ratios

ABSTRACT This study employs Large Eddy Simulation (LES) to investigate the effects of the Height-to-Diameter (H/D) ratio on the explosion characteristics of gasoline-air mixtures in storage tanks, and the flow field, flame propagation velocity, and explosion overpressure were analyzed. The research shows that the dynamic change of the vortex in the tank is the key to the explosion oscillation, its generation accelerates the flame propagation, and its weakening inhibits the explosion. As the H/D ratio increases, the peak speed of flame propagation decreases, and when the H/D ratio increases from 0.5 to 0.9, the peak speed decreases by 200%. The study also reveals that with the decrease of H/D, both peak explosion overpressure and flame velocity increase. The maximum overpressure appears near the tank top, and when H/D is 0.5, the maximum overpressure of the tank top is 3.75 MPa. The simulation result shows that internal explosion pressures exceed the tanks’ design limits across all H/D ratios, which indicates that it is necessary to take reasonable pressure relief measures to prevent and control the explosion disaster of the vaulted tanks. The research results provide important theoretical and practical guidance for the safe design of storage tanks and the prevention of explosion accidents.

Methodology for optimally designing hydrogen refueling station barriers using RSM and ANN: Considering explosion and jet fire

Hydrogen is gaining attention as a sustainable energy source with the potential to replace fossil fuels. Due to its high diffusivity and wide flammability range, hydrogen can easily ignite with minimal electrical energy, leading to explosion and fires with minimal friction. Effective blast walls can restrict the dispersion of hydrogen, reducing the explosion overpressure due to delayed ignition. In addition, firewalls can improve safety by minimizing the impact behind the walls, thereby reducing the radiant heat caused by jet fires. This study proposes to optimize the distance between leak sources and barriers, as well as the height and width of barriers, to address explosion overpressure and radiation heat at hydrogen refueling stations (HRS). The optimization was carried out using Response Surface Methodology (RSM) and Artificial Neural Networks (ANN) and validated by simulations. This study confirms the feasibility of the barrier design at HRS and contributes to the improvement of safety.

Experimental investigation on the development characteristics of high-pressure hydrogen jet flame under different ignition conditions

With the rapid development and application of hydrogen in the chemical and energy industry, the safety of hydrogen industrial facilities has been widely concerned. In this study, the safety of hydrogen accidently released from a high-pressure tube storage system (tube diameter:10 mm, storage tank volume:4 L) was explored experimentally. The combustion behavior of the transient hydrogen jet and explosion overpressure under self-ignition and electric spark induction were investigated. Besides, the explosion overpressure and jet flame evolution laws of the hydrogen cloud induced by the release of unsteady turbulent hydrogen jets into the open environment were analyzed. The results revealed that the peak value of hydrogen self-ignition explosion overpressure was higher than that of electric spark ignition overpressure. Compared with spark ignition, hydrogen self-ignition flame structures can be maintained for longer time. However, spark ignition at low release pressures was more likely to cause hydrogen ignition and explosion compared to self-ignition. Finally, the combustion behavior and potential hazards of the ignited free transient hydrogen jet under different ignition modes were analyzed. This study can provide a reference for the prevention and control of hydrogen explosion accidents in practice.