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The high-velocity wind caused by a methane-air explosion is one of the important hazardous effects in explosion events of coal mines, and, however, until now it has not been received much attention from scientific works. The paper aims to discuss this issue.

In consideration of the difficulties in observing particle velocities of high-velocity flows, this work presented a study to reveal the regularity during a methane-air explosion happening in the tunnel of coal mine through the numerical analysis approach.

The strong wind caused by a methane-air explosion is a significant hazard and can cause damage in the accidents of methane-air explosion in underground coal mines, especially at structural opening, according to this work. Obtained results show that maximum particle velocity of the high-velocity wind occurs in the outside region of the premixed area, with a peak value of 400∼500 m/s, and the peak velocity of the high-velocity wind decreases exponentially with distance beyond the premixed area.

The objective of this work was to examine the effect of wind caused by a methane-air explosion in a tunnel. Other information, such as shock wave and flame and temperature distribution, has been reported in the previous literatures. However, in the accidents of methane-air explosion in underground coal mines, some phenomena (structural opening is destroyed badly) can not be understood by using shock wave and flame and temperature distribution caused by the explosion. The strong wind caused by a methane-air explosion is another significant hazard and can cause damage in the methane-air explosion accidents in underground coal mines, especially at structural opening, according to this work.

The reaction dynamics of combustible clouds at high temperatures and pressures are a common form of energy output in aerospace and explosion accidents. The cloud explosion process is often affected by the external initial conditions. This study aims to numerically study the effects of airflow velocity, initial temperature and fuel concentration on the explosion behavior of isopropyl nitrate/air mixture in a semiconstrained combustor.

The discrete-phase model was adopted to consider the interaction between the gas-phase and droplet particles. A wave model was applied to the droplet breakup. A finite rate/eddy dissipation model was used to simulate the explosion process of the fuel cloud.

The peak pressure and temperature growth rate both decrease with the increasing initial temperature (1,000–2,200 K) of the combustor at a lower airflow velocity. The peak pressure increases with the increase of airflow velocity (50–100 m/s), whereas the peak temperature is not sensitive to the initial high temperature. The peak pressure of the two-phase explosion decreases with concentration (200–1,500 g/m³), whereas the peak temperature first increases and then decreases as the concentration increases.

Chain explosion reactions often occur under high-temperature, high-pressure and turbulent conditions. This study aims to provide prevention and data support for a gas–liquid two-phase explosion.

Sustained turbulence is realized by continuously injecting air and liquid fuel into a semiconfined high-temperature and high-pressure combustor to obtain the reaction dynamic parameters of a two-phase explosion.

The purpose of this paper is to ascertain the harm to personnel and equipment caused by an external explosion during natural gas explosion venting. The external explosion characteristics induced by the indoor natural gas explosion are the focal points of the investigation.

Computational fluid dynamics technology was used to investigate the large-scale explosion venting process of natural gas in a 6 × 3 × 2.5 m room, and the characteristics of external explosion under different scaled vent size (K_v = A_v/V2/3, 0.05, 0.08, 0.13, 0.18) were numerically analyzed.

When K_v = 0.08, the length and duration of the explosion fireball are 13.39 and 450 ms, respectively, which significantly expands the degree and range of high-temperature hazards. The suitable flow-field structure causes the external explosion overpressure to be more than twice that indoors, i.e. the natural gas explosion venting overpressure may be considerably more hazardous in an outdoor environment than inside a room. A specific range for the K_v can promote the superposition of outdoor rupture waves and explosion shock waves, thereby creating a new overpressure hazard.

Little attention has been devoted to investigating systematically the external explosion hazards. Based on the numerical simulation and the analysis, the external explosion characteristics induced by the indoor large-scale gas explosion were obtained. The research results are theoretically significant for mitigating the effects of external gas explosions on personnel and equipment.

Whether a fire can be initiated in an explosion accident depends on the explosion and deflagration process. In the methane-air explosion in a tunnel, the flame accelerates from the ignition point. However, where it begins to decelerate is not clear. The purpose of this paper is to examine the explosion overpressure, flow and flame propagation beyond the premixed area of methane-air in a tunnel.

The numerical simulation was used to study the explosion processes of methane-air mixtures in a tunnel. Based on the numerical simulation and its analysis, the explosion overpressure, flow and flame propagation rules beyond the premixed area were demonstrated for a methane-air explosion.

The peak overpressure of methane-air mixture explosion was observed to reach its maximum beyond the original premixed area of methane-air. The hazardous effects beyond the premixed area may be stronger than those within the premixed area for a methane-air explosion in a tunnel. Under the conditions of this study, the ratio between the length of combustion area (40 m) and that of original premixed area (28 m) reaches 1.43.

Little attention has been devoted to investigating the explosion overpressure, flow and flam propagations beyond the original premixed area of methane-air in a tunnel. Based on the numerical simulation and the analysis, the propagation rule of overpressure wave and flow inside and outside the space occupied by methane/air mixture at the volume fraction of 9.5 percent in a tunnel were obtained in this work.

Gas explosion is one of the most major types of accident in mining projects, and the flame front with high temperature is major hazardous factor induced by this kind of accident. Support engineering provides an available way to solve problems related to ground movements, but very likely has a great influence on the gas explosion accident process, especially the flame propagation, and then aggravates mining risk. However, until now it has not been received much attention from scientific works. The paper aims to discuss these issues.

A commercial CFD software package AutoReaGas suitable for gas explosion is used to carry out the numerical investigation of gas explosion process in a straight coal tunnel with typical support engineering, especially the unsteady explosion field and the flame propagation process in it.

Support engineering composed by multiple bars take positive influence on flame acceleration: the flame speed is much faster than that under no support bars, and the smaller support spacing induces greater flame speed near the ignition. The support bars also exert negative influence on flame acceleration: the larger support spacing induces greater flame speed in most region of the tunnel. Furthermore, a traditional viewpoint that denser obstacles induce greater explosion effects is one-sided according to this study.

At present, no one concerns the aggravating influence of support engineering on accident risk in practical mining projects because of small geometric dimension. This work examines the effect of steel support system on evolution processes of gas explosion accidents, especially the flame propagation. The conclusions provide quantitative scientific basis for this kind of the accidents in risk evolution and accident investigation of mining engineering.

The purpose of this study satisfied the need for rapid, sensitive and highly portable identification of an explosion gas. In our study, a battery-operated, low-cost and portable gas detection system consisting of a cataluminescence-based sensor array was developed for the detection and identification of explosion gas. This device shows how the discriminatory capacity of sensor arrays utilizing pattern recognition operate in environments.

A total of 25 sensor units, including common metal oxides and decorated materials, have been carefully selected as sensing elements of 5 × 5 sensor array. Dynamic and static analysis methods were utilized to characterize the performance of the explosion gas detection system to five kinds of explosion gases. The device collects images of chemical sensors before and after exposing to the target gas and then processes those images to extract the unique characteristic for each gas. Hierarchical cluster analysis (HCA) and principal component analysis (PCA) were used to analyze the image patterns.

Our study demonstrated that the portable gas detection device shows promising perspective for the recognition and discrimination of explosion gas. It can be used for the olfactory system of robot made by integrating the electronic nose and computer together.

The device collects images of chemical sensors before and after exposing to the target gas and then processes those images to extract the unique characteristic for each gas. HCA and (PCA were used to analyze the image patterns. Our study demonstrated that the portable gas detection device shows promising perspective for the recognition and discrimination of explosion gas. It can be used for olfactory system of robot made by integrating the electronic nose and computer together.

This study investigated pre-evacuation times and evacuation behaviors of vulnerable people during the 2018 flooding in Shimobara, Okayama, Japan, and the flood-triggered factory explosion, a natural hazard-triggered technological accident known as a natural-hazard-triggered technological accidents (Natech). This study examined factors that affected evacuation decisions and pre-evacuation time, estimated the evacuation time in case of no explosion and identified community disaster prevention organization response efforts for vulnerable people.

Interviews with all 18 vulnerable people who experienced the event were conducted. Multiple regression analysis was used to examine the effect of six factors on evacuation time and reasons for delayed evacuation.

Factors affecting evacuation decisions included the sound of the explosion, followed by recommendations from relatives and the community disaster prevention organization. Explosion-related injuries delayed early evacuation, but experience of previous disasters and damage had a positive effect on early evacuation. The explosion sound accelerated evacuation of non-injured people; however, explosion-related injuries significantly delayed evacuation of injured individuals. The Shimobara community disaster prevention organization’s disaster response included a vulnerable people registry, visits to all local households and a multilayered approach that enabled monitoring of all households.

This is the first study to examine the evacuation behavior of vulnerable people and community responses during a Natech event.

The purpose of this paper is to study propagation characteristics of methane explosion in the pipe network and analyze the propagation laws of methane explosion wave along the elbow pipe and pipe network.

Numerical simulation using software package AutoReaGas, a finite-volume computational code for fluid dynamics suitable for gas explosion and blast problems, is adopted to simulate the propagation characteristics of methane explosion and the property of flow field in complex structures.

Due to reflection effects of corners of elbow pipe, the peak overpressures at corner locations in the elbow pipe go about two times higher than that in the straight pipe. In the parallel pipe network, the peak overpressure increases significantly at the intersection point, while the flame speed decreases at the junction. All these indicate that pipe corners and bifurcations could substantially enhance explosion partly which can bring more severe damage at the corner area. The explosion violence is strengthened after flames and blast waves are superimposed, such that equipments and people in these areas need special strengthening protection.

The numerical results presented in this paper may provide some useful guidance for the design of the underground laneway structures and to take protective measures at corners and bifurcations in coal mines.

Explosions are the main type of accident causing casualties in underground coal mines. Little attention has been devoted to investigating the flame propagations for methane‐air explosion in a tunnel with full scale. This paper seeks to address this topic.

Based on the numerical simulation and the analysis, the propagation rule of flame and temperature waves inside and outside the space occupied by methane/air mixture at the various concentrations in a tunnel were obtained in this work.

The original interface of methane‐air mixture and air moves forward in the explosion and the original mixture area extends. For the methane‐air mixture with rich fuel concentration, the flame speed increases with distance within a range beyond the original position of the interface between the mixture and air. The flame speed reaches maximum value outside the original area of methane‐air mixture with rich fuel concentration.

Based on the numerical simulation and the analysis, the propagation rule of flame and temperature wave inside and outside the space occupied by methane/air mixture at the various concentrations in a tunnel were obtained.

The purpose of this study is to clarify the mechanism of ambient and transient temperature effects on piezoelectric pressure sensors, and to propose corresponding compensation measures. The temperature of the explosion field has a significant influence on the piezoelectric sensor used to measure the shock wave pressure. For accurate shock wave pressure measurement, based on the actual piezoelectric pressure sensors used in the explosion field, the effects of ambient and transient temperatures on the sensor should be studied.

The compensation method of the ambient temperature is discussed according to the sensor size and material. The theoretical analysis method of the transient temperature is proposed. For the transient temperature conduction problem of the sensor, the finite element simulation method of structure-temperature coupling is used to solve the temperature distribution of the sensor and the change in the contact force on the quartz crystal surface under the step and triangle temperatures. The simulation results are highly consistent with the theory.

Based on the analysis results, a transient temperature control method is proposed, in which 0.5 mm thick lubricating silicone grease is applied to the sensor diaphragm, and 0.2 mm thick fiberglass cloth is wrapped around the sensor side. Simulation experiments are carried out to verify the feasibility of the control method, and the results show that the control method effectively suppresses the output of the thermal parasitic.

The above thermal protection methods can effectively improve the measurement accuracy of shock wave pressure and provide technical support for the evaluation of the power of explosion damage.