Venting Of Deflagrations In Buildings And Equipment : Universal Correlation

Abstract

The universal correlation for gaseous deflagration venting in coordinates "dimensionless reduced pressure -turbulent venting parameter" (Molkov, 1995) have been verified on the widened range of experimental data. These included a collection of 39 literature experimental data, processed with proposed earlier theory (Molkov et al., 1981(Molkov et al., -1995. Correlation covers the most wide range of explosion conditions at initial atmospheric pressure: enclosure volumes up to 8087 m3; vent ratios F/@I3 0,09-1,23; initially uncovered and covered vents with release overpressure 0-32 kPa and cover inertia 0-23 kgim2; maximum explosion overpressure down to 0,s kPa and up to 380 kPa; most dangerous near stoichiometric air mixtures of natural gas, methane and propane; various shapes of enclosures with ratio of sizes up to 4:l; point, plane and jet ignition; with and without complex obstacles and/or external explosions. It has been proved that the universal correlation is a reliable tool for fire and explosion safety engineering.It has been shown that best-fit method usually used by researchers for comparison of theoretical and experimental pressure-time profiles should exploit two adjustable parameters -turbulence factor x and discharge coefficient p for satisfactory results.KEYWORDS: venting of deflagration, reduced overpressure, turbulent venting parameter, correlation, theory and experiment, turbulence factor, discharge coefficient, best-fit method NOMENCLATURE A part of vent cross section area, occupied by burnt gas at a given moment As the total area of the sphere available for venting, m2

Practical extension of ideal gas model for propane explosion simulation

“…Mokhtar et al [7] investigated the most widespread vented models against experimental studies. They found, e.g., in case of propaneair mixtures, that the errors of reduced explosion overpressures estimated according to EN 14994 standard [8], NFPA 68 standard [9], Bradley and Mitcheson method [10] and Molkov method [11] approximate to measurement results by a wide margin between 0.0068 and 52.258 relative error. Lautkaski [12] studied vented explosion models and vented ones with duct.…”

“…The figure shows three examples for modeled pressure rise according to original ideal gas model by Eq. (10), and modified ideal gas model by Eqs (11) and ( 15), compared to measured data by authors. Figure 7 illustrates the middle of the investigated domain (4.8 vol%).…”

Performance evaluation of empirical models for vented lean hydrogen explosions

“…However, the detailed model is used for the present study. [13] is based on a novel concept of turbulent Bradley number, and it is based on previous versions of the same model and several numerical studies by the author and his group on vented deflagrations [14][15][16][17][18][19]. Bradley number can be defines as:…”

Vented gaseous deflagrations

“…They demonstrated that model compared favourably to its analogues in predicting explosion overpressures. In 2002, Hirano [7] presented the correlation for turbulence generated during vented deflagrations, published for the first time in [5]; in his invited paper, Williams [8] cited findings in scaling of explosions based on the model [9]. Russo and coworkers [10], in their study of pressure piling in connected vessels, demonstrated that only "the universal correlation by Molkov [11] for vent sizing at initially elevated pressures is quite able to reproduce almost all overpressures observed in the second vessel in 115 experiments".…”