含NaCl超细水雾抑制甲烷爆炸实验研究

为研究含NaCl添加剂超细水雾对甲烷爆炸的影响,在自制的半封闭透明管道内,进行含NaCl添加剂超细水雾抑制甲烷爆炸试验,通过检测和分析在不同NaCl浓度情况下超细水雾的粒径和甲烷爆炸的平均火焰传播速度、爆炸超压以及平均升压速率,探究NaCl浓度对超细水雾粒径及其对抑制甲烷爆炸有效性的影响。研究结果表明:NaCl浓度对超细水雾粒径影响较小;对于体积分数为9.5%的甲烷,相比于纯甲烷爆炸,其平均火焰传播速率、最大爆炸超压以及平均升压速率分别下降了53.7%,63.4%和60.7%,相比于超细纯水雾,其平均火焰传播速率、最大爆炸超压以及平均升压速率分别下降了38.6%,58%,56%;在通雾量相同的条件下,浓度为2.5%NaCl超细水雾对体积分数为9.5%的甲烷爆炸抑制性能最佳;含NaCl添加剂超细水雾的物理化学共同作用可以有效抑爆甲烷。     

The influence of the charge-to-mass ratio of the charged water mist on a methane explosion

To study the influence of the charge-to-mass ratio of a charged water mist on a methane explosion, the induction charging method was used to induce charge on a normal water mist; a mesh target method was employed to test the charge-to-mass ratio of its droplets. The propagation images, propagation average velocities, and overpressures of a methane explosion suppressed by charged water mist were analysed. The influence of the charge-to-mass ratio of the suppressant water mist on a methane explosion was studied. Results show that the explosion temperature, propagation average velocity, and peak overpressure deceased more obviously with charged water mist than ordinary water mist. With increasing charge-to-mass ratio, the suppression effect of the charged water mist underwent a significant increase. Under experimental conditions, compared with ordinary water mist, when the charge-to-mass ratio was 0.445 mC/kg and the mist flux was 4 L, the minimum flame propagation average velocity was 3.456 m/s, with a drop of 2.37 m/s (40.68%), and the peak overpressure of the methane explosion was 10.892 kPa, with a drop of 10.798 kPa (49.78%). The suppression effect is considered from the changes of the physico-chemical properties of the water mist as affected by the applied charge-to-mass ratio.     

Enhancement effects of methane/air explosion caused by water spraying in a sealed vessel

Experiments about the influence of ultrafine water mist on the methane/air explosion were carried out in a fully sealed visual vessel with methane concentrations of 8%, 9.5%, 11% and 12.5%. Water mists were generated by two nozzles and the droplets' Sauter Mean Diameters (SMD) were 28.2 μm and 43.3 μm respectively which were measured by Phase Doppler Particle Anemometer (PDPA). A high speed camera was used to record the flame propagation processes. The results show that the maximum explosion overpressure, pressure rising rate and flame propagation velocity of methane explosions in various concentrations increased significantly after spraying. Furthermore, the brightness of explosion flame got much higher after spraying. Besides, the mist with a larger diameter had a stronger turbulent effect and could lead to a more violent explosion reaction.     

Experimental study on the synergistic inhibition effect of nitrogen and ultrafine water mist on gas explosion in a vented duct

In this study, in order to research the synergistic inhibition effect of nitrogen and ultrafine water mist on gas explosion in a vented duct, a semi-confined transparent chamber was designed with the size of 120 × 120 × 840 mm, and the experiments were carried out with stoichiometric methane/air premixed mixture (fraction of methane: 9.5%), adding different fractions of nitrogen and ultrafine water mist. The experimental results showed the following: The combination of nitrogen and ultrafine water mist had a synergistic inhibiting effect on methane/air explosion, which was preferable to the single use of any kind. With the increase of spraying time of water mist and fraction of nitrogen, the initial shape of the explosion flame became snakelike, and at the same time the peak flame propagation speed and peak overpressure decreased significantly. When the nitrogen fraction was increased to 10% and the mist spraying time was increased to 2min, synergistic inhibiting effect on overpressure was high efficient. However, with the increase of spraying time of water mist and fraction of nitrogen going on, the amount of increase of explosion inhibition efficiency was gradually reduced.     

Study on the characteristics of gas explosion affected by induction charged water mist in confined space

To investigate the suppression effect of charged water mist on gas explosion, a small charged water mist generator and a gas explosion simulation device were designed based on the principle of electrostatic induction. Experiments for testing characteristics of the gas explosion in a confined space under different charged polarities, charged voltages and mist fluxes were carried out. Experimental results indicated that, compared with the normal water mist, the explosion peak overpressure and the flame propagation speed could be more effectively reduced by the charged water mist. And this suppression effect could be promoted by increasing the charged voltage. To visualize the effect of the charged water mist's polarity on gas explosion, comparative experiments were conducted. The results showed that the explosion peak overpressure, the overpressure rising rate, and the propagation speed of the flame were reduced by 64.7%, 33.0% and 19.4%, respectively, when a +8 kV charged voltage was applied. In situation where a -8 kV charged voltage was applied, 64.1%, 26.5% and 16.0% reductions were achieved for the explosion peak overpressure, the overpressure rising rate, and the flame propagation speed respectively. Comparison of this data leads to the conclusion that the gas explosion could be more efficiently suppressed by the positively charged water mist.     

CO2-超细水雾对瓦斯/煤尘爆炸抑制特性研究

为了解CO2-超细水雾对瓦斯/煤尘爆炸抑制特性,用自行搭建的实验系统,从超压、火焰传播速度和火焰结构3个方面研究了CO2-超细水雾形成的气液两相介质对9.5%瓦斯/煤尘复合体系爆炸的抑爆效果、影响因素与原因。研究结果表明:随着CO2体积分数和超细水雾质量浓度的增加,爆炸火焰最大传播速度、爆炸超压峰值均出现明显下降,火焰到达泄爆口时间显著延迟;尤其当CO2体积分数达到14%与超细水雾的共同抑爆效果凸显,瓦斯/煤尘复合体系爆炸超压的“震荡平台”消失,同时火焰结构呈现“整体孔隙化”。所得结论为煤矿井下高效防爆抑爆技术进行了完善和增强。     

Experimental study on the inhibition of methane/air explosion by modified attapulgite powder

In order to explore the influence of attapulgite powder on the methane explosion, a small-size semi-closed visual explosion experiment platform was built, and experiments were carried out. The effect of spraying powder on the whole process of methane explosion was studied when methane concentration was 7%, 8%, 9.5%, 11% and 12%, respectively. When the methane concentration was 11%, the maximum explosion overpressure dropped by modified spraying attapulgite powder was as high as 33.26%, and at the same time, the reduction rate of flame propagation velocity reached the maximum value of 36.65%. Furthermore, when the methane concentration was 9.5%, the experimental results when the powder spraying amount of modified attapulgite was 120 mg, 160 mg, 200 mg, 240 mg and 280 mg showed that when the powder spraying was 240 mg, the maximum explosive overpressure decreased by 33.14%, and the reduction rate of the peak flame propagation velocity reached the maximum value of 33.73%. Through the video images recorded by the high-speed camera, the flame structure, shape, color, etc. Were analyzed. The characterization analysis illustrated that the modified attapulgite powder has a small particle size, relatively large porosity and specific surface area. Also, it has a high weight loss rate. Combined with the results of characterization analysis, the explosion suppression mechanism of modified attapulgite powder was discussed. It was found that the modified attapulgite powder could effectively absorb the active free radicals generated in the explosion, and the modified new chemical components have a better thermal decomposition and endothermic effect and a better suppression of methane explosions.     

超细水雾抑制甲烷爆炸的实验研究(英文)

用自行设计的三面透明的细水雾抑制甲烷爆炸的实验装置,研究了不同体积超细水雾对不同浓度甲烷爆炸的抑制现象。运用GigaView高速摄影观察了超细水雾抑制甲烷爆炸的过程,并且对现象进行了分析。采用四个E12-1-K型快速响应热电偶获取超细水雾抑爆过程中四个不同位置的温度变化情况,并且讨论了甲烷浓度和超细水雾体积对爆炸延迟时间的影响。实验结果表明,超细水雾对甲烷爆炸的抑制效果是与水雾的体积和甲烷浓度紧密相关的。初步确定了超细水雾抑制甲烷爆炸的临界体积。     

Study of the influence of melamine polyphosphate and aluminum hydroxide on the flame propagation and explosion overpressure of aluminum magnesium alloy dust

When aluminum magnesium alloy dust floats in the air, a certain ignition energy can easily cause an accidental explosion. To prevent and control the occurrence of accidental explosions and reduce the severity of accidents, it is necessary to carry out research on the explosion suppression of aluminum magnesium alloy dust. This paper uses a vertical glass tube experimental device and a 20 L spherical explosive experimental device to carry out experimental studies on the suppression of the flame propagation and explosion overpressure of aluminum magnesium alloy dust with melamine polyphosphate (MPP) and Al(OH)₃. With increasing MPP and Al(OH)₃ concentrations, the flame brightness darkened, the flame velocity and propagation distance gradually decreased, and P_max and (dp/dt)_max decreased significantly. When the amount of MPP added reached 60%, the flame propagation distance decreased to 188 mm, which is a decrease of 68%, and the explosion overpressure decreased to 0.014 MPa, effectively suppressing the explosion of aluminum magnesium alloy dust. The experimental results showed that MPP was more effective than Al(OH)₃ in inhibiting the flame propagation and explosion overpressure of the aluminum magnesium alloy dust. Finally, the inhibitory mechanisms of the MPP and Al(OH)₃ were further investigated. The MPP and Al(OH)₃ endothermic decomposition produced an inert gas, diluted the oxygen concentration and trapped active radicals to terminate the combustion chain reaction.     

Effects of premixed methane concentration on distribution of flame region and hazard effects in a tube and a tunnel gas explosion

Study of flame distribution laws and the hazard effects in a tunnel gas explosion accident is of great importance for safety issue. However, it has not yet been fully explored. The object of present work is mainly to study the effects of premixed gas concentration on the distribution law of the flame region and the hazard effects involving methane-air explosion in a tube and a tunnel based on experimental and numerical results. The experiments were conducted in a tube with one end closed and the other open. The tube was partially filled with premixed methane-air mixture with six different premixed methane concentrations. Major simulation works were performed in a full-scale tunnel with a length of 1000 m. The first 56 m of the tunnel were occupied by methane–air mixture. Results show that the flame region is always longer than the original gas region in any case. Concentration has significant effects on the flame region distribution and the explosion behaviors. In the tube, peak overpressures and maximum rates of overpressure rise (dp/dt)_max for mixtures with lower and higher concentrations are great lower than that for mixtures close to stoichiometric concentration. Due to the gas diffusion effect, not the stoichiometric mixture but the mixture with a slightly higher concentration of 11% gets the highest peak overpressure and the shock wave speed along the tube. In the full-scale tunnel, for fuel lean and stoichiometric mixture, the maximum peak combustion rates is achieved before arriving at the boundary of the original methane accumulation region, while for fuel rich mixture, the maximum value appears beyond the region. It is also found that the flame region for the case of stoichiometric mixture is the shortest as 72 m since the higher explosion intensity shortens the gas diffusion time. The case for concentration of 13% can reach up to a longest value of 128 m for longer diffusion time and the abundant fuel. The “serious injury and death” zone caused by shock wave may reach up to 3–8 times of the length of the original methane occupied region, which is the widest damage region.     

Experimental study on unconfined methane explosion: Explosion characteristics and overpressure prediction method

Explosion accidents have become the main threat for the high-efficiency use of cleaner gas energy sources, such as natural gas. During an explosion, obstacle causing flame acceleration is the main reason for the increase of the explosion overpressure, which still remains to be fully understood. In this research, field experiments were conducted in a 1 m³ cubic frame apparatus to investigate the effect of built-in obstacles on unconfined methane explosion. Cage-like obstacles were constructed using square steel rods with different cross section size. The results demonstrated that the flame could get accelerated due to the hydrodynamic instability and obstacle-induced turbulence, which enhanced the explosion overpressure. In the near field, the overpressure wave travelled slower and the maximum overpressure could almost keep constant. Reducing the cross section size, or increasing the obstacle height or the obstacle number per layer could determine the rise of the maximum overpressure, the maximum pressure rising rate and the overpressure impulse. For uniformly constructed obstacles, self-similar theory was chosen to measure the influence of the hydrodynamic instability, and a parameter β was adopted to measure the flame acceleration caused by obstacle-induced turbulence, the value of which was 2 in this research. Based on the acoustic theory, an overpressure prediction model was proposed and the predicted results agreed with the measured values better than previous models, such as TNT equivalency model and TNO multi-energy model.     

滑移装置抑制甲烷爆炸影响分析

为减少瓦斯二次爆炸带来的危害,研发新型抑爆弹性滑移装置,并将滑移装置与固定装置对比,分析其对9.5％甲烷/空气预混气体爆炸抑制效果.结果表明:滑移装置抑爆效果优于固定装置;滑移装置能缩短火焰燃烧时间,固定装置超压峰值高于滑移装置;由于轻碳板反向速度提高,弹性系数为0.85 N/mm的滑移装置对火焰和超压抑制效果优于弹性...     

Influence of vacuum degree on the effect of gas explosion suppression by vacuum chamber

In order to study the influence of vacuum degree on gas explosion suppression by vacuum chamber, this study used the 0.2 mm thick polytetrafluoroethylene film as the diaphragm of vacuum chamber to carry out a series of experiments of gas explosion suppression by vacuum chamber with the vacuum degree from −0.01 MPa to −0.08 MPa. The experimental results show that: under the condition of any vacuum degree, vacuum chamber can effectively suppress the explosion flame and overpressure; as vacuum degree changes, the effect of gas explosion suppression using vacuum chamber is slightly different. Vacuum chamber has obvious influence on propagation characteristics of the explosion flame. After explosion flame passes by vacuum chamber, the flame signal weakens, the flame thickness becomes thicker, and the flame speed slows down. With the increase of the vacuum degree of vacuum chamber, the flame speed can be prevented from rising early by vacuum chamber. The higher the vacuum degree is, the more obviously the vacuum chamber attenuates the explosion overpressure, the smaller the average overpressure is, and the better effect of the gas explosion suppression is. Vacuum chamber can effectively weaken the explosion impulse under each vacuum degree. From the beginning of −0.01 MPa, the vacuum chamber can gradually weaken explosion impulse as the vacuum degree increases, and the effect of gas explosion suppression gradually becomes better. When the vacuum degree is greater than −0.04 MPa, the increase of vacuum degree can make the explosion overpressure decrease but have little influence on the explosion impulse. Therefore, the vacuum chamber has the preferable suppression effect with equal to or greater than −0.04 MPa vacuum degree.     

The explosion overpressure field and flame propagation of methane/air and methane/coal dust/air mixtures

The explosion of the methane/air mixture and the methane/coal dust/air mixture under 40 J center spark ignition condition was experimentally studied in a large-scale system of 10 m³ vessel. Five pressure sensors were arranged in space with different distances from the ignition point. A high-speed camera system was used to record the growth of the flame. The maximum overpressure of the methane/air mixture appeared at 0.75 m away from the ignition point; the thickness of the flame was about 10 mm and the propagation speed of the flame fluctuated around 2.5 m/s with the methane concentration of 9.5%. The maximum overpressure of the methane/coal dust/air mixture appeared at 0.5 m. The flame had a structure of three concentric zones from outside were the red zone, the yellow illuminating zone and the bright white illuminating zone respectively; the thickness and the propagation speed of the flame increased gradually, the thickness of red zone and yellow illuminating zone reached 3.5 cm and 1 cm, the speed reached 9.2 m/s at 28 ms.     

Investigation on the suppression effect of high momentum C6F12O (Novec-1230) flow on hydrogen jet flame

This work investigates the suppression effect of Novec-1230 on H₂ jet flame. The suppressants are motivated by N₂ flow to get higher momentum and approach the reaction kernel at flame base. The flame area with Novec-1230 is always smaller than that with water mist at the same condition. Novec-1230 exhibits better suppression effect on reaction kernel. The higher-momentum jet flame is more difficult to be suppressed. This is because that the higher-momentum flame makes the suppressant approach the reaction kernel more difficult. In addition, the high N₂ flow rate containing suppressant could destroy flame temperature structure and decrease it. Results inferred that the temperature of flame with Novec-1230 is higher than that with water mist. Moreover, the lower minimum extinguishing time indicates that the suppression efficiency of Novec-1230 is better than that of water mist. The jet flame is extinguished only when H₂ flow rate is low and N₂ flow rate is high. There are two reasons: one is that the higher-momentum jet flame prevents suppressants to enter flame core. The other one is that the burner nozzle is heated to as igniting source during suppression progress. Furthermore, the burning velocity, adiabatic flame temperature, heat production and free radicals are investigated theoretically at Φ = 1.6, 1.0, 0.8 and 0.6. Results indicate that the burning velocity with Novec-1230 is much lower than that with water mist. The adiabatic flame temperature, heat production and free radicals increase firstly and then decrease with Novec-1230 addition at lean flame.     

Methane/coal dust/air explosions and their suppression by solid particle suppressing agents in a large-scale experimental tube

Methane/coal dust/air explosions under strong ignition conditions have been studied in a 199 mm inner diameter and 30.8 m long horizontal tube. A fuel gas/air manifold assembly was used to introduce methane and air into the experimental tube, and an array of 44 equally spaced dust dispersion units was used to disperse coal dust particles into the tube. The methane/coal dust/air mixture was ignited by a 7 m long epoxypropane mist cloud explosion. A deflagration-to-detonation transition (DDT) was observed, and a self-sustained detonation wave characterized by the existence of a transverse wave was propagated in the methane/coal dust/air mixtures.The suppressing effects on methane/coal dust/air mixture explosions of three solid particle suppressing agents have been studied. Coal dust and the suppressing agent were injected into the experimental tube by the dust dispersion units. The length of the suppression was 14 m. The suppression agents examined in this study comprised ABC powder, SiO₂ powder, and rock dust powder (CaCO₃). Methane/coal dust/air explosions can be efficiently suppressed by the suppression agents characterized by the rapid decrease in overpressure and propagating velocity of the explosion waves.     

Effects of hydrogen addition on propagation characteristics of premixed methane/air flames

An experimental study has been conducted to investigate the effects of hydrogen addition on the fundamental propagation characteristics of methane/air premixed flames at different equivalence ratios in a venting duct. The hydrogen fraction in the methane–hydrogen mixture was varied from 0 to 1 at equivalence ratios of 0.8, 1.0 and 1.2. The results indicate that the tendency towards flame instability increased with the fraction of hydrogen, and the premixed hydrogen/methane flame underwent a complex shape change with the increasing hydrogen fraction. The tulip flame only formed when the fraction of hydrogen ranged from 0 to 50% at an equivalence ratio of 0.8. It was also found that the flame front speed and the overpressure increased significantly with the hydrogen fraction. For all equivalence ratios, the stoichiometric flame (Φ = 1.0) has the shortest time of flame propagation and the maximum overpressure.     

Suppression of methane explosions in a field-scale pipe

Suppression of passive and active explosions has been investigated in a field-scale pipe in this paper. Water recognized effective in explosion suppression has been chosen as the extinguishing agent, and the water mist formed by home developed passive and active explosion suppressors has been proved successfully to meet the practical requirements. The experimental results showed that the suppression effects depend on the density and length of water mist suspended inside the pipe, and both passive and active explosion suppressors can fully quench the explosion of methane–air mixture with the filling of enough water. The larger the mist density and length is, the better the suppression effect becomes. For passive explosion suppression, two suppressors with different arrangements have been discussed. Moreover, a critical curve was plotted based on the experimental results of active explosion suppressions, which can be applied to evaluate the suppression effects practically.     

细水雾技术在抑制瓦斯爆炸中的应用

介绍了细水雾抑制瓦斯爆炸的机理以及部分应用细水雾对瓦斯爆炸效果影响的实验,提出了采用细水雾方法抑制瓦斯爆炸有可能为瓦斯防治领域开辟新的途径.     

Preparation and performance of novel APP/NaY–Fe suppressant for coal dust explosion

Coal dust explosion occurs easily in the coal chemical industry. To ensure safety in industrial production, NaY zeolite was used as carrier modified with Fe ions and combined with ammonium polyphosphate (APP) to prepare a novel composite suppressant for coal dust explosion. The explosion suppression performance of novel APP/NaY–Fe suppressant was investigated by flame propagation inhibition experiments. The results show that Fe ion modification can effectively improve the explosion suppression performance. By increasing content, the explosion suppression performance of the explosion suppressant increases. The maximum explosion pressure P_max of coal dust drops to 0.13 MPa when 50 wt% explosion suppressants were added, and the coal dust explosion cannot continue to expand. Complete suppression of explosion could be achieved by adding 66 wt% explosion suppressants. Combined with XRD, SEM and TG results, the explosion suppression mechanism was proposed. The novel explosion suppressant has high thermal stability, good dispersity and its explosion suppression components distribute uniformly. It shows good explosion suppression performance by the synergistic effect among explosion-suppression components.