Experimental study of the effects of vent area and ignition position on internal and external pressure characteristics of venting explosion

Premixed hydrogen–air explosion experiments were carried out in a 1000 mm × 50 mm × 10 mm half-open narrow channel, concerning with the influences of equivalence ratio and ignition position on explosion behaviors. Experimental phenomena were different from explosion in large space. The results indicated that when ignited at the closed end of the channel, three overpressure peaks appeared, caused by the rupture of the film, Helmholtz Oscillation, and the flame-acoustic interaction, respectively. As the equivalence ratio of the hydrogen–air mixtures varied from 0.6 to 1.6, the peak overpressure first increased and then decreased. The maximum peak overpressure occurred at ϕ = 1.2. The hydrogen flame would develop into the plane tulip structure without the influence of the end wall. With the ignition position moved to the open end, overpressure wave and flame oscillated significantly. Compared with other ignition positions, the minimum value of P max was obtained at IP 950 . Based on the explosion behaviors in the narrow channel, it was concluded that the closer the ignition was to the open end, the easier the oscillation was to be formed, the smaller the explosion hazard was.

Section: Resultsmentioning

confidence: 99%

“…In order to balance the negative pressure, the gas would flow back. Meanwhile, the unburned gas in the channel continued to burn and provided energy for the Helmholtz oscillation . The interaction of flame and sound also controlled the periodic oscillation by affecting the RT instability.…”

Section: Resultsmentioning

confidence: 99%

Experimental Studies on the Explosion Behaviors of Premixed Hydrogen–Air Mixtures in a Narrow Channel

Zhang

Wen

et al. 2022

“…Third, after charging methane in V1 to V2 based on the gas state equation, methane at a concentration of 9.5 vol % was employed, corresponding to 1069 kPa in V2 in each test, and then the outlet valve on the wall of the chamber was opened; meanwhile, the menthane in V2 was completely charged into the V3 in the chamber. The V3 was pulled out from the chamber via the inlet, then all outlet and inlet valves were closed, the methane and air in the chamber were mixed by the explosion-proof fan to allow work for 3 min, and the chamber was allowed to remain static for 3 min before ignition to maintain the methane–air mixture at a low and consistent level in the chamber. , The turbulence level was measured by a hot wire anemometer with a measuring range of 0–20 m/s (405i, Testo SE & Co. KGaA, China), which is based on our previous study, and then the methane concentration was further determined by the equation CH 4 % = 1 – O 2 %/21%, where O 2 % was obtained by the oxygen sensors with the accuracy of 0.1 vol % (AO2PTB-18.10, City, UK) and 21% refers to the oxygen concentration in the air. Finally, a synchronous control unit was adopted to trigger the data acquisition system, ignition system, infrared camera, and high-speed camera.…”

Section: Methodsmentioning

confidence: 99%

Experimental Study of External Flame Evolution and Temperature Characteristics after a Methane Explosion in a Rectangular Chamber

Xing

et al. 2023

Self Cite

A series of methane-vented explosions were experimentally investigated in a 4.5 m3 rectangular chamber at P 0 = 100 kPa and T 0 = 298 K, and the effects of ignition positions and vent areas on the external flame and temperature characteristics were studied. The results indicate that the vent area and ignition position significantly affect external flame and temperature changes. The external flame is portioned into three stages: an external explosion, a violent flame jet with a blue flame, and a yellow flame venting. The temperature peak first rises and then reduces with increasing distance. Rear ignition produces the largest flame lengths and highest temperature, while front ignition leads to the shortest flame and smallest temperature peak. The maximum flame diameter occurs at central ignition. As vent areas increase, the coupling effect of the pressure wave and the internal flame front weakens and the diameter and peak of the high-temperature peak increase. These results can offer scientific guidance for designing disaster prevention measures and evaluating explosion accidents in buildings.

“…Hydrogen explosions can destroy buildings, damage generating equipment, and cause casualties. − Therefore, the study of hydrogen explosion hazards and their prevention is of great importance for the safe use of hydrogen. Inerting, suppression, and ventilation are common methods to reduce the risk of hydrogen explosions, with inert gases being most commonly used to suppress gas explosions due to their inertness, chemical stability, cleanliness, and effectiveness.…”

Section: Introductionmentioning

confidence: 99%

Effect of N₂ and CO₂ on the Explosion Properties of High Equivalence Ratios of Hydrogen

Luo,

Qi,

et al. 2023

The explosion characteristics of premixed gases under different equivalence ratios (1.0–3.0) and inert gas addition (5–20%) are experimentally investigated, and sensitivity analysis of the radical reactions is carried out using the USC Mech II model to analyze the molar fraction of radicals. The results show that at high equivalence ratios, inert gas has little effect on flame stability. The addition of an inert gas reduces the tensile rate in the early stage of flame growth. At high equivalence ratios, CO 2 inhibits explosive flame propagation twice as effectively as N 2 . Due to the large heat capacity and chemical kinetic effects, CO 2 has a stronger inhibitory effect on the explosion pressure than N 2 , and the inhibition efficiency on the explosion strength is nearly twice that high. To further analyze the effect of different inert gas addition ratios on chemical kinetics, sensitivity analysis, and molar fraction simulations were performed. The thermal and chemical kinetic effects of CO 2 cause later generation of H and OH radicals and the partial chain reaction involving CO 2 causes a lower peak of H radicals than the peak of H radicals generated under an N 2 atmosphere. However, CO 2 is a direct reactant and the third body to produce a small chemical kinetic effect.