Peak Overpressure Research Articles

Experimental and theoretical investigations into overpressure during confined space explosions of methane-hydrogen mixture

This study aimed to deeply explore combustion and explosion behaviors within confined spaces fueled by methane-hydrogen blends. By experimenting in a 55 m³ chamber, it examined how different hydrogen mixing ratios (5%, 10%, 15%, and 30%) affect flame spread and overpressure buildup at an equivalence ratio of 1.1. Results showed that two main flame patterns emerge during venting: mushroom clouds and jet flames. Higher hydrogen percentages cause mushroom clouds to form earlier and grow larger; notably, a 30% blend produces a cloud 12% quicker than a 10% blend, reaching a maximum radius of about 2.7 m. Three types of overpressure were identified: Popen (venting structure opening), Pext (external explosion), and Phel (Helmholtz oscillations). Both Pext and Phel rise with increasing hydrogen content. At each blend level, Pext peaks at 1.87–6.42 kPa, while Phel ranges from 5.86 to 20.65 kPa. Pext plays a crucial role in peak overpressure during venting, particularly relevant for ventilation design considerations. To predict Pext, the study tested three engineering models and found that Taylor's spherical piston theory provided the closest match to experimental data, with a maximum error under 30% compared to other models. In summary, this research offers essential theoretical knowledge and practical evidence for designing safer ventilation and explosion relief systems for facilities handling methane-hydrogen mixtures in the process industry.

A comparison of far-field explosive loads by a selection of current and emerging blast software

In blast resistant design, simulation data may be used to generate the explosive loads that would be witnessed by the detonation of a high explosive device. There are many software packages available to simulate explosions, and this study aims to provide a comparison of a selection of them, including some recently available, with the aim of forming an understanding of the potential accuracies and speed of these in far-field explosive prediction. Software selection criteria were formed by a literature survey to highlight the commonly commercially used programmes. Each software package was used to predict the far-field effects of overpressure and specific impulse from two explosive charges against a reflective target. The data generated by these simulations were then critically compared and reviewed, both with respect to each other and, for the 100 kg charge size, with respect to experimental data. It shows that for the simulated scenarios, after domain and cell size fidelity studies have been performed, the choice of software may lead to a variance in prediction in the peak overpressure of up to 50%, specific impulse of up to 15%, and simulation run times by a factor of 600.

Explosion characteristics of lithium-ion batteries vent gases containing dimethyl carbonate at elevated temperatures

Dimethyl carbonate (DMC) is a common component of lithium-ion batteries (LIBs) electrolyte, which is vented into the environment along with LIBs thermal runaway vent gases (BVG). This study used different ratios of DMC/BVG mixtures to simulate the combustible components vented from LIBs thermal runaway process. The explosion characteristic parameters of the DMC/BVG mixtures, such as the peak overpressure (Pex), the peak rate of pressure rise ((dp/dt)ex), lower flammability limits (LFL) and limiting oxygen concentrations (LOC), were investigated in an 8-L stainless steel cylindrical explosion vessel. The results indicated that as the percentage of DMC increased, maximum Pex, maximum (dp/dt)ex and LOC of the mixtures increased, while LFL showed a decrease trend. In addition, LFL decreased approximately linearly as increasing the initial temperature. The Britton correlation method can estimate LFL at varying initial temperatures. The research results are helpful to better understand the risk of the mixtures vent from LIBs and provide a reference for the explosion-proof design of LIBs’ transport containers and LIB energy storage stations.

Gas explosion characteristics and spray control mechanism in underground square.

The spray system mechanism during a gas explosion in an underground square pipeline is complex. In this paper, the underground square of Fuxin City is selected as the research object. FLACS numerical simulation software is used to analyze the spatial and temporal distribution characteristics of a gas explosion in an underground square pipeline with an unopened spray system using combustion and combustion rate models. Different spray pressures were compared and analyzed to determine the optimal spray control pressure, and the spray system mechanism was clarified. The results revealed that the gas explosion overpressure is divided into the overpressure gentle, overpressure rising, and overpressure decay stages, corresponding to a trend of rapid growth and slow decline. The influence of spray pressure on the gas explosion exhibits a promotion-inhibition-promotion trend, corresponding to 0-0.2 MPa, 0.2-0.6 MPa, and 0.6-1.6 Mpa, respectively. The peak overpressure and overpressure propagation rates are the lowest at 0.6 MPa, and the explosion suppression effect is the most pronounced. The spray system mechanism varies with the explosion overpressure stages. Generally, the time to peak value, that is, the peak time, the overall duration of the explosion, and the duration of the explosion stage decrease, whereas the peak explosion overpressure decreases.

Cylindrical Steel Tanks Subjected to Long-Duration and High-Pressure Triangular Blast Load: Current Practice and a Numerical Case Study

This paper presents an investigation into the design of ammonia tanks for long-duration and high-pressure blast loads. The focus is on cylindrical steel tanks that apply as outer pressure-tight containers for double-walled tanks storing refrigerated liquefied gases. Based on limited empirical data, it is known in the tank industry that these tanks can withstand an explosion pressure up to a peak overpressure of approximately 10 kPa and 100 ms positive load duration. However, there is a growing need to design tanks for higher peak overpressures in order to establish a higher safety standard and accommodate unforeseen future requirements. This paper explores the concept of adapting established steel tank designs to handle high-pressure and long-duration overpressure due to blast events. Numerical analysis is conducted on a representative steel tank geometry subjected to a triangular blast load of 30 kPa with a 300 ms positive load duration. Various load application and calculation options are analyzed numerically. Considering the challenging nature of analyzing tank structures under blast load, the paper addresses controversial aspects discussed in the literature and presents a suitable analysis concept for a deflagration blast scenario for cylindrical tanks. The results provide insights into the expected structural behavior of the tank under high-pressure and long-duration overpressure. The main finding is that the calculation method developed in this study demonstrates the feasibility of utilizing steel tanks in scenarios involving long-duration and high-pressure blast loads. Furthermore, the paper provides recommendations to guide future studies in this area. The findings have implications for the design and construction of tanks in critical infrastructure and offer valuable insights for engineers and researchers in this field, improving safety standards and ensuring adaptability to future utilization concepts.

Experimental and numerical study on natural gas explosion evolution in open space under different initial conditions

The vapor cloud explosion in open space are greatly affected by the initial conditions of gas cloud and the surrounding environment, while in the gas compressor station, these factors are ubiquitous. While the researches of external influencing factors like the obstacle and initial turbulence effect on natural gas explosion in open space are rare. In this paper, a series of natural gas explosion experiments were conducted and a long-distance natural gas pipeline compressor station was taking as an example to simulate the natural gas leakage and explosion in the typical location. Results showed that the greater the initial turbulence, the greater the peak overpressure of gas explosion. When the initial wind speed is 5 m/s, the peak overpressure can promote 73.4 % higher than that without initial turbulence. However, the overpressure doesn't linearly increase with the increasing of initial wind speed. What's more, the flame speed showed the same law with the overpressure, and the effect of concentration on overpressure is lower than that of initial turbulence and obstacle density. The explosion damaging range in the condenser area is larger than that in the separator area, and the maximum overpressure can reach about 21 kPa and the temperature can reach above 2280K, which provides an important basis for the safety prevention and personnel protection in natural gas compressor station.

New approach for calculation of peak over pressure and impulse of aluminized explosive charges

ABSTRACT RDX/HMX-TNT-based aluminized explosive compositions have been investigated to find empirical relations based on heat of explosion (Q) and velocity of detonation (VOD) for calculation of peak over pressure (POP) and impulse (I). Four HMX-TNT-based aluminized compositions have been selected based on calculated values of Q and explosive power. Explosive charges of RDX/HMX-TNT-based aluminized compositions and TNT have been prepared by melt-cast technique for measurement of VOD and air blast. Cylindrical explosive charges with length to diameter ratio of ~ 1 and weight ~ 1.3 kg have been used for measurement of pressure-time profiles at standoff distance of 2–6 m. Similar measurements were also performed for the explosive charges of TNT of weight ~ 11 and 17 kg. Normalized values of Q and VOD 2 with corresponding values of TNT have been used to compute charge weight for calculation of scaled distance which is termed as normalized scaled distance. Form of empirical relations has been decided from variation of POP and I with normalized scaled distance. Values of constants used in these relations have been determined using regression analysis. Validation of empirical relations has been carried out by comparing calculated and experimental values of POP and I for explosive charges.

Effect of internal phase particle size on properties of site mixed emulsion explosive at plateau environment

To study the effect of internal particle size on the microstructure properties and thermal decomposition characteristics of site mixed emulsion explosive at different altitudes. Site mixed emulsion explosive was prepared with different shear rate. The particle size, viscosity, sensitized bubbles, detonation velocity and peak pressure of the emulsion explosive were tested after stored at different simulated altitudes. The thermal decomposition characteristics of emulsion matrix prepared at three different rotational speeds were measured by thermogravimetric analyzer and kinetic analysis was performed by non-isothermal model Kissinger–Akah–Sunose (KAS) method. The results show that with the increase in altitude, the internal phase size showed a trend of first increasing and then decreasing, and the number of sensitized bubbles within the emulsion explosive decreases. At an altitude of 0 m, the detonation velocity and peak overpressure of the emulsion explosive prepared by 1600 r min−1 increased 4.78% and 29.09%, respectively compared with 1200 r min−1, and at an altitude of 4500 m, the detonation velocity increased 11.87%, the peak overpressure increased 43.98%. The thermal decomposition activation energy of the emulsion matrix at 1600 r min−1 increased 13.14% compared to 1200 r min−1. It shows that in the production of site mixed emulsion explosive at high altitude, reducing the particle size of the internal phase of emulsion explosives in a certain range can effectively improve the performance of emulsion explosives.

A reinforced concrete shear wall building structure subjected to internal TNT explosions: Test results and numerical validation

When an explosion occurs within reinforced concrete shear wall (RCSW) structures, the overpressures and duration of blast loads will be amplified by the confining effects of enclosed walls, which can cause more severe damage to the structure than a free air explosion (FAE). However, research on RCSW structures subjected to internal explosions (IEs) are still limited and no benchmark tests exist. To provide a benchmark for studying the blast resistance of RCSW structures subjected to IEs, three Trinitrotoluene (TNT) IE field tests were conducted in this study on a 2-story, 3 × 3-bay, 1/3 scaled RCSW substructure, in which the overpressures, displacements, and crack patterns of RCSWs were recorded. The three tests were performed consecutively after each other on the same structure at TNT loads of 95.3 g (Test-1), 253 g (Test-2), and 400 g (Test-3). The test results showed that the floor slab directly above the explosion and one of the RCSW confining the explosion failed in flexure (i.e., the support rotation angle exceeds 2°) in Test-2 with the scaled distance of 1.53, whilst the other three neighboring RCSWs failed in flexure in Test-3 with the scaled distance of 1.31. In addition, a detailed finite element model was established using LS-DYNA and was validated against the test results. The numerical simulation results showed that the energy released from TNT in IE scenarios (14.5 GJ/m3) was 1.95 times that in FAE scenarios (7.43 GJ/m3). The total blast loads applied to the RCSWs increased with the decrease of the area of opening. The average impulse applied to the four RCSWs were similar in IE scenarios, and the average impulse could be represented by the impulse at the center of each of the RCSWs (excluding the RCSW with window opening, as the opening is at the center). The shock and gas overpressure impulses at the center of RCSWs accounted for approximately 19.4 % and 80.6 % of the total impulse, respectively. Furthermore, the peak overpressures at the wall centers and the total blast loads experienced by the RCSWs under IE scenarios were 1.79 times and 11.13 times higher than those under FAE scenarios, respectively. This was due to the confinement of enclosed walls under IE scenarios. Consequently, the displacements and damage levels of the RCSW substructure under IE scenarios were much larger than those under FAE scenarios.

Study on the Earth-Covered Magazine Models under the Internal Explosion

The use of earth-covered magazines (ECMs) is increasingly prevalent in protective engineering due to their concealment and cost-effectiveness. To explore the optimal thickness of earth covering for ECMs, scaled model tests were conducted under explosive charges equivalent to 30 kilograms of TNT. The resulting overpressure outside the model in the 180° direction was measured. Subsequently, computational analyses were conducted employing LS-DYNA software to examine these experimental findings. The findings indicate that increasing the thickness of the rear soil can mitigate peak overpressure, delay the air shock wave’s arrival time, and reduce the impulse of the positive phase. The numerical calculations closely align with experimental data, with peak overpressure deviation remaining under 10%. The shock wave initially impacts the top of the model before reaching the rear, with soil scattering more pronounced in the 90° direction compared to the 180° direction. Furthermore, an analysis of soil energy absorption rate variation was conducted based on energy conservation principles. These results provide valuable insights for optimizing the design and construction of ECMs.

Cumulative Blast Impulse Is Predictive for Changes in Chronic Neurobehavioral Symptoms Following Low Level Blast Exposure during Military Training.

Cumulative low-level blast exposure during military training may be a significant occupational hazard, increasing the risk of poor long-term outcomes in brain function. US Public Law 116-92 section717 mandates that US Department of Defense agencies document the blast exposure of each Service member to help inform later disability and health care decisions. However, which empirical measures of training blast exposure, such as the number of incidents, peak overpressure, or impulse, best inform changes in the neurobehavioral symptoms reflecting brain health have not been established. This study was approved by the US Army Special Operations Command, the University of North Carolina at Chapel Hill, and the VA Puget Sound Health Care System. Using methods easily deployable across different organizational structures, this study sought to identify and measure candidate risk factors related to career occupational blast exposure predictive of changes in neurobehavioral symptom burden. Blast dosimetry-symptom relationships were first evaluated in mice and then tested in a military training environment. In mice, the righting time neurobehavioral response was measured after exposure to a repetitive low-level blast paradigm modeled after Special Operations training. In the military training environment, 23 trainees enrolled in a 6-week explosive breaching training course, 13 instructors, and 10 Service member controls without blast exposure participated in the study (46 total). All participants provided weekly Neurobehavioral Symptom Inventory (NSI) surveys. Peak blast overpressure, impulse, total number of blasts, Time in Low-Level Blast Occupation, and Time in Service were analyzed by Bayesian analysis of regression modeling to determine their probability of influence on the post-training symptoms reported by participants. We tested the hypothesis that cumulative measures of low-level blast exposure were predictive of changes in neurobehavioral symptoms. In mice, repetitive blast resulted in reduced righting times correlated with cumulative blast impulse. In Service members, peak blast overpressure, impulse, total number of blasts, Time in Low-Level Blast Occupation, and Time in Service all showed strong evidence of influence on NSI scores after blast exposure. However, only models including baseline NSI scores and cumulative blast impulse provided significant predictive value following validation. These results indicate that measures of cumulative blast impulse may have utility in predicting changes in NSI scores. Such paired dosimetry-symptom measures are expected to be an important tool in safely guiding Service members' occupational exposure and optimizing force readiness and lethality.

The analysis on the overpressure propagation characteristics of gas cloud explosion

The overpressure propagation characteristics of gas cloud explosion are analyzed. The spatial propagation of pressure wave appears to be self-similar. Due to the acoustic property, the absolute values of overpressure peak and impulse peak all decrease in inverse proportion rule. The built-in obstacle could cause the remarkable increase of positive overpressure peak and the absolute value of negative overpressure peak is always lower than that of positive parameter. With pressure wave propagating, the time reaching the positive overpressure peak decreases gradually. The time τ and the distance δ to form a shock front decrease with the increase of pressure wave intensity. However, τ remains constant and δ turns to rise as the pressure intensity increases continually. The positive overpressure duration time remains constant during propagation. For unconfined gas cloud explosion, the integral of overpressure against time is equal to zero and Imax and Imin basically share the same absolute value.

Effect of hydrogen ratio on leakage and explosion characteristics of hydrogen-blended natural gas in utility tunnels

Based on computational fluid dynamics technology, the effect of hydrogen blending ratio (HBR) on the concentration distribution of leaked gas diffusion in utility tunnels was investigated, and based on this, the explosion characteristics of hydrogen-blended natural gas (HBNG) were studied in an inhomogeneous concentration field. The results showed that the concentration field of HBNG gradually stabilized in the downstream of the leak site, and the peak concentration increased linearly with HBR. When HBR≤5%, a high concentration region above the upper explosive limit is formed inside the gas cloud. This characteristic of the distribution induces secondary combustion in utility tunnels. The maximum flame velocity and steady acceleration distance increase with the increase of HBR. The flame shape is significantly affected by the concentration field distribution. The explosion overpressure induced by the real concentration field created multiple peak structures that exacerbated the explosion disaster complexity. The first overpressure peak at the ends was formed by the superposition of the precursor shock wave and its reflected wave, and those at other locations are caused by the shock waves. However, all maximum overpressure peaks are formed by the superposition of multiple reflections of the explosion wave. The maximum peak overpressure at both ends of the tunnel is higher than that in the middle. The explosion overpressure induced by the inhomogeneous gas cloud is lower than that caused by homogeneous gas cloud under the same volume. The research results can provide an effective reference for the anti-explosion design and risk assessment of utility tunnel.

Seismoacoustic measurements of the OSIRIS-REx re-entry with an off-grid Raspberry PiShake

Hypersonic re-entries of spacecraft are valuable analogues for the identification and tracking of natural meteoroids re-entering the Earth's atmosphere. We report on the detection of seismic and acoustic signals from the OSIRIS-REx landing sequence, acquired near the point of peak capsule heating and recorded using a fully off-grid Raspberry PiShake sensor. This simple setup is able to record all the salient features of both the seismic and acoustic wavefields; including the primary shockwave, later reverberations, and possible locally induced surface waves. Peak overpressures of 0.7~Pa and ground velocities of 2x10$^{-6}$~m/s yield lower bound on the air-to-ground coupling factor between 3 and 44~Hz of 1.4x10$^{-6}$m/s/Pa, comparable to results from other re-entries

Effect of polyurethane foam and carbon dioxide on the suppression of hydrogen/air explosion

This study examines the influence of polyurethane porous materials and carbon dioxide on hydrogen/air explosions within an enclosed vessel. Through analysis of peak overpressure, maximum rate of pressure rise, and shock wave propagation velocity, the suppression effects on explosions in hydrogen-air mixtures with different equivalence ratios at room temperature and atmospheric pressure are investigated. Findings indicate that porous materials with a PPI (pores per inch) of 60 significantly mitigate hydrogen/air explosions across all equivalence ratios. Conversely, a PPI below 60 exacerbates the explosions. Simultaneous presentation of PPI60 porous material and a CO2 addition level of x = 2 (carbon dioxide to oxygen ratio) reduces hydrogen explosion pressure to only 13.7 kPa at "Φ = " 1.2, representing an attenuation rate of 84% and falling well below the human safety threshold of 28 kPa. Independent effects of carbon dioxide and porous materials on hydrogen explosions across various equivalence ratios are also explored. The experimental design encompasses a broad range of equivalence ratios, covering hydrogen's explosive limits. These results contribute to the design of flame arrestors and enhance understanding of explosion suppression in hydrogen systems.

A study of the effect of hydrogen on methane deflagration characteristics in a square confined space

Macroscopic and microscopic explosion kinetic properties of H2/CH4/air mixtures are investigated. The explosion characteristics of CH4/air mixtures with different hydrogen blending ratios(0–25%) are investigated experimentally. It is found that the increase of hydrogen blending ratios has almost no effect on the peak overpressure of the methane gas explosion, but the rate of maximum pressure rise, the explosion index and the flame propagation velocity increase significantly. The effect of hydrogen blending ratios on the chemical kinetics of CH4-air mixtures is analyzed based on the CHEMKIN software. The concentration of key radicals, which play a major role in the reaction, does not change much as the hydrogen blending ratio increases. A prediction model of explosion overpressure in a square confined space is established using the segmentation method, and it is verified that the relative errors between the model calculation results and experimental results are less than 10%.

Study on cumulative effects of biological craniocerebral trauma under repeated blast

Repeated blast impacts on personnel in explosive environments can exacerbate craniocerebral trauma. Most existing studies focus on the injury effects of a single blast, lacking in-depth analysis on the injury effects and cumulative effects of repeated blasts. Therefore, rats were used as the experimental samples to suffer from explosion blasts with different peak air overpressures (167 kPa∼482 kPa) and varying number of repeated blasts. The cumulative effect of craniocerebral trauma was most pronounced for moderate repeated blast, showing approximately 95% increase of trauma severity with penta blast, and an approximately 85% increase of trauma severity with penta minor blast. The cumulative effect of craniocerebral trauma from severe, repeated blast has a smaller rate of change compared to the other two conditions. The severity of trauma from penta blast increased by approximately 69% compared to a single blast. Comprehensive physiological, pathological and biochemical analysis show that the degree of neurological trauma caused by repeated blasts is higher than that of single blasts, and the pathological trauma to brain tissue is more extensive and severe. The trauma degree remains unchanged after double blast, increases by one grade after triple or quadruple blast, and increases by two grades after penta blast.

Research on the Shock Wave Overpressure Peak Measurement Method Based on Equilateral Ternary Array.

The measurement process of ground shock wave overpressure is influenced by complex field conditions, leading to notable errors in peak measurements. This study introduces a novel pressure measurement model that utilizes the Rankine-Hugoniot relation and an equilateral ternary array. The research delves into examining the influence of three key parameters (array size, shock wave incidence angle, and velocity) on the precision of pressure measurement through detailed simulations. The accuracy is compared with that of a dual-sensor array under the same conditions. Static explosion tests were conducted using bare charges of 0.3 kg and 3 kg TNT to verify the numerical simulation results. The findings indicate that the equilateral ternary array shock wave pressure measurement method demonstrates a strong anti-interference capability. It effectively reduces the peak overpressure error measured directly by the shock wave pressure sensor from 17.73% to 1.25% in the test environment. Furthermore, this method allows for velocity-based measurement of shock wave overpressure peaks in all propagation direction, with a maximum measurement error of 3.59% for shock wave overpressure peaks ≤ 9.08 MPa.

The distribution law of shock wave pressure in typical trenches

Trenches, as important practical military facilities, have important theoretical and military value in evaluating the damage power of ammunition, operational application, and effective safety protection of personnel on the battlefield through the spatiotemporal evolution of explosive shock waves within them. At present, there is a lack of in-depth research on the distribution and impact of overpressure inside the trench. The paper constructed a typical finite element simulation model of a trench, numerically calculated the shock wave overpressure inside the trench and on the wall, analyzed the spatiotemporal distribution of shock wave pressure in various parts of the trench, conducted on-site explosion tests, and installed shock wave pressure sensor measurement points in the trench. The pressure time history curve was obtained, and verified and compared with the simulation calculation results. Research data shows that the peak overpressure of the shock wave in the trench increases sequentially from the front wall to the back wall. The peak overpressure of the shock wave at the front wall attenuates by 10 % to 20 % compared to the inside of the trench, and increases by 40 % to 60 % at the back wall; The peak overpressure in the trench exhibits a “V-shaped” distribution at different depths, decreasing first and then increasing as the depth increases. The maximum overpressure peak increases by 40 % to 50 % compared to the minimum; Based on simulation and measured data in the trench, as well as the distribution law of shock wave pressure, safety protection suggestions for on-site combat personnel in the trench are provided.

Mitigating Blast Hazards: Experimental Evaluation of Anti-Shatter Films and Catcher-Cable Systems on Conventional Windows

In light of terrorist attacks and accidents, the need for structural protection against explosive events has increased significantly in recent decades. Conventional unprotected windows pose a particularly high risk of injury to building occupants due to glass fragments and window frames being propelled into the interior and exterior of a building. This article addresses new experimental research on the protection of conventional single casement windows with insulating glass units (double-paned) and window frames made of un-plasticized polyvinyl chloride (uPVC) against blast loads. Entire window systems were tested in ten shock-tube tests using different retrofit-configurations. The retrofitted protective measures include anti-shatter films and catcher-cable systems. Furthermore, the influence of steel profiles inserted in the window frames is investigated. The applied blast loads met the requirements for ER1-certification according to EN 13541:2012 (tested at a reflected peak overpressure of 66.7 kPa and a reflected maximum impulse of 417.7 kPa∙ms). In the test series, various measurement methods were used to capture the velocity of the window fragments, the dynamic cable forces, and the hazard. The data provide valuable information for the design and implementation of catcher-cable systems for existing buildings, which can improve the occupant safety in the event of an explosion.