The recent concept of inherent safety uses the properties of a material or process to eliminate or reduce the risk thus removing or minimizing the hazard at the source as opposed to accept the hazard and looking to mitigate the effects. In this framework the control of particle size in dust explosion prevention and mitigation is recognized as a major inherent safety methodology. Indeed, the increase of particle size may allow significant reduction of particle reaction rate eventually reducing the risk. 
 
In this paper a novel model is developed to quantify the effect of particle size on dust reactivity in an explosion phenomenon. The model takes into account all of the steps involved in a dust explosion: internal and external heating, devolatilization reaction and volatiles combustion. Varying the dust size can establish different regimes depending on the values of the characteristic time of each step and of several dimensionless numbers (Damkohler number, Da; Biot number, Bi; thermal Thiele number, Th). Results from the model are reported in terms of the deflagration index (KSt) as a function of dust diameter in all regimes and at varying Da, Th and Bi. Comparison with experimental data from polyethylene explosion tests shows promising results. Finally, the results of the model are presented in the form of a dust explosion regime diagram, which is helpful to make a draft evaluation of the role of dust size on explosion behavior and severity.

Modelling the effect of particle size on dust explosion

Dynamic hazard evaluation of explosion severity for premixed hydrogen–air mixtures in a spherical pressure vessel

Experimental and numerical studies on the closed and vented explosion behaviors of premixed methane-hydrogen/air mixtures

Explosion pressure and flame characteristics of CO/CH4/air mixtures at elevated initial temperatures

Abstract Binary fuel blends of methane and hydrogen have a wide application in the internal combustion engines due to their promising combustion performance, although substantial studies have been carried to investigate the combustion characteristics, very limited study focused on its detonation limits for propagation in tubes or pipes. In this study, near detonation limits behavior, which includes velocity deficit and cellular structure, of binary fuel blends of methane and hydrogen mixtures with different compositions (i.e., CH4–2H2–3O2, CH4–H2–2.5O2 and CH4–4H2–4O2) are experimentally studied, experiments are carried out in a 36 mm inner diameter round tube and annular channels with three gaps (w = 2 mm, 4.5 mm and 7 mm). The results show the maximum detonation velocity deficit is 7% of CJ (Chapman–Jouguet) velocity for three mixtures in the 36 mm inner diameter round tube, and this velocity deficit is universal in the mixtures with different compositions. As detonations transmit into the annular channels, the velocity deficits in CH4–2H2–3O2 and CH4–4H2–4O2 mixtures are very close, i.e., within 10–20% VCJ in the different scale of channels. For CH4–H2–2.5O2 mixtures, velocity deficit varies from 15.0% to 34.1% VCJ as the annular channel gap reduces from 7 mm to 2 mm, which is due to it has a higher degree of instability and hence more robust than other mixtures, a critical value of stability parameter χ is determined as 15–20, below which the instability has no significant effect on the velocity deficit. The cellular pattern from the smoked foils indicates single-headed spinning detonation in CH4–H2–2.5O2 mixture appears at lower initial pressure than other two mixtures, and the detonation cell size for this mixture is larger at the same initial condition, which is verified by the evidence from ZND induction zone length analysis.

Detonation limits in binary fuel blends of methane/hydrogen mixturesDetonation velocity deficits of H2/O2/Ar mixture inround tube and annular channels

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

The effect of ignition location and vent burst pressure on the internal pressure-time history and external flame propagation was investigated for vented explosions of hydrogen–air mixtures in a small cylindrical vessel. A high-speed camera was used to record videos of the external flame while pressure transducers were used to record pressure-time histories. It was found that central ignition always leads to the maximum internal peak overpressure, and front ignition resulted in the lowest value of internal peak overpressure. The internal peak overpressures are increased corresponding to the increase in the vent burst pressure in the cases of central and rear ignition. Because of the effect of acoustic oscillations, the phenomenon of oscillations is observed in the internal pressure profile for the case of front ignition. The pressure oscillations for the cases of rear and central ignition are triggered by external explosions. The behavior of flames outside the chamber is significantly associated with the internal pressure of the chamber so that the velocity of the jet flame is closely related to the internal overpressure peak.

The effect of ignition location on explosion venting of hydrogen–air mixtures

Experimental study of overpressure and temperature field behaviors of a methane-air mixture with different ignition positions, solid structure obstacles and initial turbulence levels

Bin Li

Papers

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

The effect of ignition location on explosion venting of hydrogen–air mixtures

Experimental study of overpressure and temperature field behaviors of a methane-air mixture with different ignition positions, solid structure obstacles and initial turbulence levels

The effects of vent area and ignition position on pressure oscillations in a large L/D ratio duct

Effect of metal powders on explosion of fuel-air explosives with delayed secondary igniters