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Effects of isobutene (i-C 4 H 8) with the unique molecular structure on hydrogen explosions are investigated in a 14 L spherical chamber at 100 kPa and 298 K. The results reveal that for lean hydrogen-air mixtures, the maximum explosion overpressure, maximum pressure rise rate, and deflagration index show a trend from rise to decline. However, for stoichiometric and rich hydrogen-air mixtures, pressure parameters decrease monotonously with increasing i-C 4 H 8. The chemical suppression mechanism of i-C 4 H 8 on hydrogen explosions is revealed in detail by numerical simulation. The relevant analyses show that i-C 4 H 8 can not only change the chain reaction path and cut off the hydrogen-oxygen reaction, but also strengthen the consumption of oxygen and H radicals. This work will provide a novel theoretical foundation for hydrogen explosion prevention and control. [Display omitted] • Effects of i-C 4 H 8 on flame and pressure of hydrogen are observed. • Hydrogen explosions can be effectively suppressed by less than 6.0% i-C 4 H 8. • I-C 4 H 8 can change hydrogen-oxygen chain reaction pathways. • I-C 4 H 8 suppresses hydrogen explosions by enhancing oxygen consumption. [ABSTRACT FROM AUTHOR]

The effects of isobutene (i-C 4 H 8) and carbon dioxide (CO 2) on hydrogen explosions have been explored in a 14 L spherical chamber at 100 kPa and 298 K. The results show that compared with CO 2 , the cooperation of i-C 4 H 8 and CO 2 can more effectively suppress the explosion pressure, pressure rise rate, and deflagration index. The minimum suppression concentration of CO 2 with 1.5% i-C 4 H 8 is much lower than that of CO 2 alone. Numerical simulation reveals the mechanism of the suppression of i-C 4 H 8 and CO 2. I–C 4 H 8 changes the reaction paths, and the addition of CO 2 further lowers the adiabatic flame temperature and the active radical concentration. The excellent performance of the cooperation of i-C 4 H 8 and CO 2 in hydrogen explosions will provide a new idea for the prevention and control of hydrogen explosions. • The cooperation of i-C 4 H 8 and CO 2 is better than using CO 2 alone. • I–C 4 H 8 can effectively reduce the minimum suppression concentration of CO 2. • The suppression mechanism of i-C 4 H 8 and CO 2 in hydrogen explosions is revealed. [ABSTRACT FROM AUTHOR]

The flame behavior and pressure characteristics of vented propane-air explosions at elevated static activation pressures (P stat) were investigated in a duct with a length-to-diameter (L/D) ratio of 7. The impact of the discharge traction and the coupling effect of the internal flame front and pressure waves on the flame propagation behavior were captured. The effect of increasing P stat on the vented flame length and width under a fixed vent was weak. The influences of P stat on the pressure profiles and maximum reduced pressure (P red) were investigated. The increase of P stat mitigated the blocking effect of external explosion on P red and further promoted the discharge pressure drop rate to be controlled within the limit of the discharge capacity of the vent. The formation mechanisms of the two main external pressure peaks were analyzed. For the larger D v conditions, the sensitivity of high P stat to the increase of maximum external pressure was higher than that of low P stat. A modified model of P red was developed considering the effects of elevated P stat and vent coefficient K V , which is proved to have a good performance in vented explosion ducts with a large L/D ratio. [ABSTRACT FROM AUTHOR]

This work is to experimentally and theoretically explore the hydrogen cloud explosion subjected to external turbulence. In the experiments, the flame characteristics and explosion pressure are obtained using high-speed camera and pressure sensor. In the theoretical calculation, the peak explosion pressure is obtained using LM, LMIET and TM method. The results indicated that most flame characteristics in the experiments are located in the zone of wrinkled flamelets. The explosion-related parameters including flame propagation velocity, peak explosion pressure and peak rate of pressure rise continue to increase as the gear level increases from G0 to G3, increase firstly and then decrease as the equivalence ratio increases from Φ = 0.5 to Φ = 3.0. Due to ignoring flame acceleration propagation induced by flame instabilities, external turbulence and flame-induced turbulence, the peak explosion pressure obtained using experimental method is significantly larger than that obtained using LM method. Owing to considering the limit value of flame wrinkling level induced flame instabilities and flame-induced turbulence, the peak explosion pressure obtained using experimental method is significantly lower than that obtained using LMIET and TM method. • Effects of external turbulence on flame acceleration is analyzed. • Peak explosion pressure and peak rate of pressure rise are obtained. • Peak explosion pressure is calculated using LM, LMIET and TM method. [ABSTRACT FROM AUTHOR]