Explosion Overpressure Research Articles

Turbulence influence factor estimation of gasoline-air explosion in multi-branch tubes

To estimate the turbulence influence of the branch tubes on the rising rate of gasoline-air mixture explosion overpressure, turbulence factor α was introduced to modify the formula of the peak rise rate of explosion overpressure. Then, the experimental data of peak explosion overpressure and overpressure rise rate under the different numbers of branches were obtained. Finally, the experimental data and laminar flame velocity were put into the overpressure rise rate correction formula, and the turbulence influence factors under different branches were calculated. The results show that increasing the number of branches will improve the turbulence degree of the explosion process. When the number of branching pipes is 1, the turbulence impact factor is about 2.0 times that in the case of no branch tube, while when the number of branch tubes is more than 1, the turbulence impact factor fluctuates about 3.5 times.

Explosion mitigation of methane–air mixture in combined application of HFC‐227ea/CO2 and ultrafine water mist in the pipeline

AbstractIn order to reduce the power of methane explosion in natural gas pipelines and effectively improve the explosion suppression efficiency of a single explosion suppressant, we carry out the explosion suppression of HFC‐227ea/carbon dioxide mixed gas as well as mixed gas/ultrafine water mist through a self‐built methane explosion suppression experimental platform. Based on the changes in parameters such as explosion overpressure, flame propagation velocity, and flame propagation structure, the coupling mechanism of methane explosion suppression between mixed gases and between mixed gases and ultrafine water mist is revealed, which provides scientific support for promoting the development of methane explosion suppression technology. The experimental results show that when the mixed gas HFC‐227ea/carbon dioxide and ultrafine water mist synergistically suppresses methane explosion, the addition of the mixed gas can effectively improve the suppression effect of ultrafine water mist on methane explosion.

Deep learning-driven super-resolution reconstruction of two-dimensional explosion pressure fields

Precise and rapid calculation of explosive loads on structures in specific explosion scenarios is crucial for blast-resistant design, emergency response and safety assessments of structures after disasters. However, available methods such as empirical models and numerical simulations are inadequate in meeting the fast computation demands for diverse explosion scenarios due to limitations in accuracy or computational cost. In order to obtain high-precision explosion pressure fields and overpressure time histories with low computational cost, this study presents a deep learning-based framework for reconstructing two-dimensional explosion pressure fields, which transforms low-resolution numerical simulation results into super-resolution outputs equivalent to high-resolution numerical simulation results. A super-resolution strategy, which concatenates high-resolution channels that record flow field information with the low-resolution channel, is proposed to improve the network performance. Based on the constructed dataset, a comparative study of three different networks is presented to assess their super-resolution applicability. Finally, the performance and generalization ability of the trained model is evaluated with super-resolution evaluation metrics, statistical evaluation metrics, and relative error distribution. The findings indicate that the super-resolution strategy can effectively improve the prediction accuracy of the network. The super-resolution model can not only provide high-credibility super-resolution pressure fields and pressure time histories, but also exhibits excellent generalization capabilities for explosive scenarios beyond the training dataset, therefore providing a new approach for realizing high-precision calculation of explosive flow fields and loads under diverse blast scenarios.

Large-scale transient simulation for consequence analysis of hydrogen-doped natural gas leakage and explosion accidents

Transporting blended hydrogen natural gas through existing natural gas pipeline networks is an important strategy for meeting the growing demand for hydrogen energy. However, gas leakage poses a serious safety concern. This study conducts a large-scale simulation of gas leakage and explosion accidents in a hydrogen-doped natural gas station and aims to evaluate the impact of pipeline pressure and leakage direction on the accident consequences. Simulation results indicated that the high pipeline pressure led to more accumulated flammable gas, which caused severer explosion disasters. Within the 100s simulation period, the cumulative volume of the flammable gas cloud reached 2329.80 m3 under 4 MPa pipeline pressure, and the peak explosion overpressure increased by 69.64% compared with the 1 MPa case. Leakage directions also significantly affect the evolution of accidents. Suppose the leakage direction is towards living areas, flammable gas is more likely to accumulate in confined spaces up to 2363.20 m3. The gas explosion will severely damage the building structure with a 17 kPa explosion overpressure and 7 kPa shock wave intensity. Interaction with wind and the disturbance of obstacles also contributed to the flammable gas cloud accumulation, which increased peak values of explosive overpressure.

Influence of initial gas concentration on methane–air mixtures explosion characteristics and implications for safety management

Gas explosions, particularly those involving methane–air mixtures, present considerable hazards in confined spaces, such as coal mines. Comprehending the explosion characteristics and their correlations with initial gas concentrations is vital for devising effective safety measures. This study examines the influence of initial gas concentration on explosion temperature, overpressure, and flame evolution in methane–air premixed gas explosions, utilizing a custom-built 20-L spherical explosion experimental apparatus. The explosion temperatures display an oscillatory pattern, reaching maximum values at 6.5%, 9.5%, and 12% initial gas concentrations, with corresponding temperatures of 995 K, 932 K, and 1153 K. The maximum overpressure exhibits an initial rise and fall trend, modeled by an exponential function. Notably, in proximity to the 9.5% concentration, the pressure wave fosters the reverse propagation of the flame wave, leading to a secondary temperature increase. Flame sensors were employed to investigate the presence, absence, and duration of flames, demonstrating that elevated initial gas concentrations resulted in more prolonged flame durations and increased harm. At an initial gas concentration of 9.5%, a persistent flame is generated instantaneously during the explosion. Furthermore, the study analyzes the interplay between temperature and overpressure, underscoring the significance of mitigating high-temperature burns near tunnel walls and enclosed spaces. These findings advance the understanding of gas explosion dynamics and hold substantial implications for safety measures in coal mines.

Effect of initial pressure on the critical characteristics and overpressure of hydrogen-air premixed gas combustion and explosion

In order to ensure the safe utilization of hydrogen, the flame characteristics and explosion overpressure at lean-burn, stoichiometric and rich-burn conditions are investigated systematically by varying initial pressures. Experiments were conducted in a constant-volume combustion chamber using the Schlieren system to investigate the critical characteristics of hydrogen-air premixed flames at different equivalence ratios (from 0.2 to 6.5) and initial pressures (from 50 kPa to 150 kPa). The cellular instabilities of hydrogen-air premixed flames were interpreted and evaluated from the viewpoint of thermal-diffusive and hydrodynamic instabilities. The influence of initial pressure on the cellular instability and combustion and explosion characteristics were analyzed. The results show that the variation of thermal-diffusive instability dominantly governs the cellular instability at lean-burn conditions (φ = 0.3–1.0). In contrast, the cellular instability at rich-burn conditions (φ > 1.5) is governed by the variation of hydrodynamic instability. The increase of initial pressure promotes the cellular instabilities noticeably caused by the rise of the hydrodynamic instability. With the increase of P0, the Lewis number Le and thermal expansion ratio σ almost remain the same while flame thickness δ noticeably decreases. Increasing initial pressure at lean-burn and stoichiometric conditions (φ < 2.0) facilitates cellular instability, making the explosion more intense and resulting in higher explosion overpressure. In contrast, the variation of initial pressure suppresses the laminar combustion at rich-burn conditions (φ > 3.0).

Study on premixed hydrogen-ammonia-air flame evolution in a horizontal rectangular duct

The hydrogen-ammonia mixture exhibits significant potential as a carbon-free fuel for internal combustion engines. To gain a deeper understanding of the combustion characteristics of hydrogen-ammonia-air flames in internal combustion, the flame evolution and pressure dynamics are systematically investigated in a closed duct by varying ammonia mixing ratio and equivalence ratio. Concerning flame dynamics, the distorted tulip flame disappears and the inclined flame is formed as the ammonia mixing ratio increases. Additionally, the depression and protrusion structure distributed on flame front is diminished. For pressure dynamics, as the equivalence ratio increases, both the maximum explosion overpressure and maximum pressure rise rate initially increase and then decrease. As the ammonia mixing ratio increases, both of them continue to decrease, and the equivalence ratio corresponding to the peak value transfers from Ф = 1.2 to Ф = 1.0. In terms of detailed chemistry analysis, the H and OH radical dominate when the ammonia mixing ratio is lower than Ω = 40%. NH2 and OH radical dominate at ammonia mixing ratio higher than Ω = 80% on the lean and stoichiometric side, but NH2 and H radical dominate at ammonia mixing ratio higher than Ω = 40% on the rich side.

Numerical analysis of the diffusion and explosion characteristics of hydrogen-air clouds in a plateau hydrogen refuelling station

The investigation of hydrogen diffusion and explosion characteristics after accidental hydrogen leaks in hydrogen refuelling stations can provide the theoretical reference of the safe application of hydrogen refuelling stations. The numerical study analyses the effects of plateau environment on the dispersion and explosion characteristics of combustible clouds, visualises the diffusion and explosion process of hydrogen-air combustible clouds and quantifies the hydrogen concentration and explosion pressure at monitoring points. Results show that combustible clouds may appear upstream of the leak hole due to the presence of obstacles. The low atmospheric pressure conditions in the plateau areas result in high hydrogen concentration near the blast wall and large combustible cloud size. The hydrogen concentration near the blast wall and combustible cloud volume are also shown a positive correlation with air temperature, which will be detrimental to fire protection in hydrogen refuelling stations. After the explosion of the hydrogen clouds, the mortality zone (explosion overpressure ≥0.69 bar) is observed near the blast wall and at high leak volumes, the hazardous zone (0.07 bar ≤ explosion overpressure ≤0.69 bar) may spread over the blast wall into the crowded area. However, the blast wall blocks the development of the high-temperature zone, which has a positive effect on preventing the spread of the explosion flame. An examination of the pressure monitoring point data reveals that there appears to be an opposite effect of atmospheric pressure on the positive and reverse overpressure. The maximum peak blast overpressure in calculated domain indicates that both higher air temperatures and atmospheric pressures promote the growth of explosion overpressure.

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 explosion characteristics of hydrogen in a sudden expansion pipe

ABSTRACT As a promising green energy source, the risk of hydrogen explosion cannot be ignored. In the industrial environment, the connection between factories and different regions may form a mutated structural space. This structure may have a significant impact on the consequences of hydrogen accidents, which is worthy of study. In this research, the simulation method is used to analyze the explosion and combustion process of hydrogen flame propagation in a sudden expansion pipe, which focuses on the impact of the cross-section ratio. The results indicate that due to the influence of Rayleigh-Taylor instability, the flow field in the dead zone near the sudden expansion structure can be unstable and generate vortices, which will significantly change the development of gas combustion and explosion. Under the extrusion and entrainment of vortices, the flame front structure is changed from finger-like flame to mushroom-like flame. When the flame enters the downstream pipe section through the expansion port, the impact of vortices on the flame propagation velocity is changed from suppression to excitation, and the excitation effect is closely related to the cross-section ratio. At the cross-section ratio μ = 3, the maximum flame propagation velocity and maximum pressure growth rate of the downstream pipe are 198.7 m/s and 53.12 MPa/s, respectively, which are 68.8% and 151.4% times higher than those in the case of the cross-section ratio μ = 1.5. There is a remarkable impact of sudden expansion structure on flame propagation and explosion overpressure.

Study on Energy Output Characteristics of Aluminized Emulsion Explosive

In order to study the energy output characteristics of multi-component explosives mixed with aluminum powder and emulsified explosives, five groups of emulsified explosives containing aluminum with different proportions were used for underwater explosion experiments and overpressure tests in the air. The experimental data show that when the mass fraction of aluminum powder increases from 0% to 40%, the shock wave energy increases from 0.68 kJ·g-1 to 1.22 kJ·g-1, which increases by 79.41%. Bubble energy increased by 135.66% from 2.44 kJ·g-1 to 5.75 kJ·g-1; the total energy of underwater explosion increased by 123.40% from 3.12 kJ·g-1 to 6.97 kJ·g-1. The explosion overpressure in the air increased by 93.66% from 60.794 KPa to 117.734 KPa. Aluminum powder greatly increases the output level of emulsified explosives. Emulsified explosive containing aluminum has the characteristics of high working capacity and high explosive performance.

Analysis of the Consequences of Hydrogen-Blended Natural Gas Leakage Accidents

ABSTRACT The safe operation of natural gas stations as complex and dense equipment sites after the mixed transportation of hydrogen will face great challenges. Predicting accident consequences is of importance for emergency rescue. In this work, the evolution law in the accident scenarios of hydrogen-blended natural gas stations was investigated through a computational fluid dynamics (CFD) model. The results suggest that the mix of hydrogen and natural gas increases the explosion intensity of combustible gas clouds, which however also accelerates the diffusion rate of leaked gas into air. Therefore, the peak explosion overpressure fails to show a simple linear relationship with the hydrogen blending ratio in different hydrogen blending ratio scenarios. The worst accident consequences occur in Scenario 2 (hydrogen blending ratio = 20%), where the blast overpressure peak reaches 19.29 kPa. Wind can accelerate the material transmission speed of leaked gas in space. In scenarios with larger wind speeds, the hazard degree of accidents can be significantly reduced.

Suppression effects of energy-absorbing materials on natural gas explosion in utility tunnels

The energy-absorbing material of metal foam have enormous potential in mitigating the consequences of natural gas explosion disaster in urban utility tunnels. When double-layer metal foam with different pore structures of first larger pores and then smaller pores (LP-SP model), the suppression efficiency of explosion overpressure can reach more than 60% and is 2–3 times that of first smaller pores and then larger pores (SP-LP model), and the error between that and that of the same thickness all with smaller pore structure is only 0.86%. Similarly, the metal foams with the LP-SP model can block the explosion flame propagation chain entirely, while reversing the combination order weakens the suppression effect on the explosion flame. Two suppression mechanisms of double-layer metal foam, including the Sudden Shrinkage Effect (SSE) of the LP-SP model and the Amplification Effect (AE) of the SP-LP model. The metal foam barrier device based on SSE is designed for utility tunnels, which can take effect within 0.1 s under electromagnetic force and gravity. This study can provide scientific theoretical support for designing gas explosion suppression measures in utility tunnels.

Experimental and Numerical Study on Deflagration Characteristics of Large-Scale Propane-Air Mixture.

Seven deflagration tests of a propane-air mixture were carried out in a 22.5 m3 large-scale chamber. The effects of initial volume, gas concentration, and initial turbulence intensity on deflagration characteristics were analyzed. The main frequency of the explosion wave was quantitatively determined by the combination of the wavelet transform and energy spectrum analysis. The results show that the explosive overpressure is formed by the discharge of combustion products and secondary combustion, and the effects of turbulence and gas concentration on the explosive overpressure are higher than the initial volume. Under the condition of weak initial turbulence, the main frequency of gas explosion wave is between 32.13 and 48.33 Hz. Under strong initial turbulence conditions, the main frequency of the gas explosion wave increases with the increase of overpressure, and the empirical formula of the relationship between the main frequency and overpressure is summarized, which could provide theoretical support for the design of mechanical metamaterials for oil and gas explosion. Finally, the flame acceleration simulator numerical model was calibrated through tests, and the overpressure simulation values were in good agreement with the experimental data. The leakage, diffusion, and explosion of a liquefied hydrocarbon loading station in a petrochemical enterprise were simulated. The lethal distance and explosion overpressure at key buildings are predicted for different wind speed conditions. The simulation results can provide a technical basis for evaluating personnel injury and building damage.

Spatial distribution and machine learning-based prediction model of natural gas explosion loads in a utility tunnel

A reasonable natural gas explosion load model is essential to evaluate the damage to the utility tunnel. This study systematically investigates critical parameters that affect gas explosion loads in the utility tunnel by the finite volume method, including ignition point location, methane volume, methane concentration, internal obstacles, and utility tunnel structure. An explosion load model in a typical utility tunnel is established using the artificial neural network (ANN), with peak overpressure, impulse, and arrival time as output parameters. The spatiotemporal distribution equation of gas explosion loads in a utility tunnel is given, and the importance analysis of parameters is also carried out. The results indicate that when the methane volume is larger than 300 m3, the detonation phenomenon generally occurs in the utility tunnel, and the effect of the obstacle on the explosion loads also increases. The ANN-based model can accurately describe the explosion overpressure and duration at each section in the utility tunnel. The methane volume and cross-sectional size of the utility tunnel have the most significant impact on the natural gas explosion. The important coefficient of the cross-sectional size of the utility tunnel for peak overpressures reaches 30.94 %, and the important coefficients of the methane volume for explosion impulses and arrival time are 47.31 % and 39.64 %. ANN-predicted model is efficient and quick to estimate the gas explosion loads for structural dynamics analysis.

Characteristics of dust explosion venting pressure and flame under high activation pressure

A 20 L spherical explosive device with a venting diameter of 110 mm was used to study the vented pressure and flame propagation characteristics of corn dust explosion with an activation pressure of 0.78–2.1 bar and a dust concentration of 400∼900 g/m3. And the formation and prevention of secondary vented flame are analyzed and discussed. The results show that the maximum reduced explosion overpressure increases with the activation pressure, and the vented flame length and propagation speed increase first and then decrease with time. The pressure and flame venting process models are established, and the region where the secondary flame occurs is predicted. Whether there is pressure accompanying or not in the venting process, the flame venting process is divided into two stages: overpressure venting and normal pressure venting. In the overpressure venting stage, the flame shape gradually changes from under-expanded jet flame to turbulent jet flame. In the normal pressure venting stage, the flame form is a turbulent combustion flame, and a secondary flame occurs under certain conditions. The bleed flames within the test range are divided into three regions and four types according to the shape of the flame and whether there is a secondary flame. The analysis found that when the activation pressure is 0.78 bar and the dust concentration is less than 500 g/m3, there will be no secondary flame. Therefore, to prevent secondary flames, it is necessary to reduce the activation pressure and dust concentration. When the dust concentration is greater than 600 g/m3, the critical dust concentration of the secondary flame gradually increases with the increase of the activation pressure. Therefore, when the dust concentration is not controllable, a higher activation pressure can be selected based on comprehensive consideration of the activation pressure and destruction pressure of the device to prevent the occurrence of the secondary flame.

An analysis of li-ion induced potential incidents in battery electrical energy storage system by use of computational fluid dynamics modeling and simulations: The Beijing April 2021 case study

To further grasp the failure process and explosion hazard of battery thermal runaway gas, numerical modeling and investigation were carried out based on a severe battery fire and explosion accident in a lithium-ion battery energy storage system (LIBESS) in China. The composition and transport law of gas caused by large-scale LIB failure were theoretically analyzed, and the explosion risk of thermal runaway gas mixture in complex space after accidental ignition were systematically discussed by the computational fluid dynamics (CFD) technology. After the investigation, the underground cable trench is the key channel that causes the thermal runaway gas of lithium iron phosphate batteries to be transported to the building 20 m away and induces the explosion. After about 8500 s of battery burning, the average concentration of the thermal runaway mixed gas diffused from the cable trench is 16.4%. The arrangement of obstacles in the accident building is the main factor determining the explosion overpressure of thermal runaway gas, and the overpressure generated at the end of the obstacle path exceeds 70 kPa. Multiple windows in the battery room play an effective explosion-venting effect, but increase the damage range of outdoor high-temperature flame. In addition, the System-Theoretical Accident Model and Processes (STAMP) was used to analyze the causes of the accident, and the safety constraints that should be imposed by the three control levels of the government, functional departments and energy storage power stations were introduced to prevent battery failure and fire accidents in the BESS. The research method and analysis results will provide important ideas and reference for the investigation of fire and explosion accidents in BESS.

A dynamic approach to identify hazardous areas for H2S-containing natural gas release and explosion accidents on offshore platforms

Many efforts have been made to predict and mitigate the toxic impact and explosion impact. However, they are inadequate for the chain accident of toxic gas-containing flammable gas release and explosion since these two hazardous impacts can happen continuously. Accordingly, an integrated approach concerning chain accident consequence assessment is proposed, in which the human behavior is taken into account. The risk-based concept and grid-based concept are introduced in this approach to integrate the adverse impacts. The approach is applied to a hypothetical chain accident involving H2S-containing natural gas release and explosion on an offshore platform. The emergency evacuation is considered by establishing an emergency evacuation time model. A cumulative H2S inhalation dose along each evacuation trajectory is derived to evaluate the toxic impact by considering the temporal-spatial variation of both H2S profile and sufferers’ positions. The maximum explosion overpressures in the real-time position of the sufferers are extracted to predict the explosion impact. The proposed approach is systematic and efficient for practical engineering applications. It can help to develop safety measures and improve the contingency plan.

Prediction of Spatial Peak Overpressure Profile of Air Blast Shocks Using Multiple Linear Regression and Artificial Neural Network

The shock peak overpressure yielded by energetic materials in the near-earth explosion causes damage to people and property. In the literature, several works have reported the effectiveness in obtaining the peak overpressure in the near field by numerical simulation, real tests, and empirical calculations. However, several issues are associated with the above methods, such as the time-consuming of a complex simulation, the difficulties in placing sensors in an obstacle block site, and the limited scope of applications for empirical equations. At present, there is no single model that can rapidly predict the spatial distribution of shock peak overpressure with ground reflection. In this regard, this paper aims to solve the problem of shock propagation in a large-scale space and obtain a model that can predict a wide range of spatial distribution of peak overpressure in the near-earth air blast simply and quickly. This work uses AUTODYN-2D to obtain the peak overpressure of the cylindrical charge explosion in the air near earth. The peak overpressure from the numerical models agrees with the empirical equations and the real blast results. On this basis, the multiple linear regression (MLR) and the optimal error back-propagation artificial neural network (ANN) models are tried and constructed with three geometric parameters as the input under a typical environment. The input parameters are the straight line scaled distance (SLSD), the vertical scaled distance (VSD), and the scaled height of burst (SHOB), respectively. The prediction results of the MLR and ANN models are verified and compared on the test set. Results show that the ANN model with the geometric parameters as the input is better than the MLR model in predicting the air blast peak overpressure. The former takes no more than 0.2s to compute 1441 sets of inputs, which provides a quick reference for predicting spatial peak overpressure in a large-scale shock wave of the air blast.

Difference Analysis of Different Explosion Load Simulation Methods Based on LS-DYNA

LS-DYNA provides a variety of different explosion load simulation methods, which are widely used in the field of explosion shock. Compared with the direct application of explosion load on the structural surface, the simulation method of establishing the air domain is more complex, but it can reproduce the evolution process of the explosion flow field and consider the interaction between the shock wave and the structure. The simulation results are more consistent with the actual situation. In this paper, the four commonly used explosion load simulation methods in LS-DYNA software are compared and analyzed, and the sensitivity analysis of grid size is carried out. The differences in the results of the four explosion load simulation methods under typical explosion conditions are compared and analyzed from the aspects of explosion shock wave waveform, arrival time, overpressure peak and specific impulse. The analysis results show that the proportional detonation distance of 0.8 m/kg1/3 is the boundary point of grid sensitivity ; under the same grid size, different explosion load simulation methods have little effect on shock wave arrival time, but have obvious influence on overpressure peak value and specific impulse. It is critical to reasonably select the termination time of the low-dimensional model when using the mapping method ; method 1 and method 2 are preferred for simulation without considering the computational cost or small model size. When the model is large, method 3 and method 4 should be preferred to improve the computational efficiency.