scholarly journals Influence of Multiple Factors on the Explosion Characteristics of Flammable Gases in Municipal Sewage Pipelines

2020 ◽  
Vol 2020 ◽  
pp. 1-17
Author(s):  
Pengfei Lv ◽  
Jiaxu Zhang ◽  
Lei Pang ◽  
Kai Yang ◽  
Siheng Sun
Keyword(s):  
Flame Propagation ◽  
Propagation Velocity ◽  
Horizontal Well ◽  
Substantial Effect ◽  
Municipal Sewage ◽  
Flame Propagation Velocity ◽  
Explosion Pressure ◽  
Significant Difference ◽  
Pressure Peak ◽  
Oil Gas

Using the hydrodynamic software Fluidyn, a numerical model comprising a top-sealed vertical inspection well and a horizontal well with openings at both ends was built based on symmetry, to study the explosion propagation of flammable gases in typical municipal sewage pipelines. The vertical well had a diameter of 0.7 m and different depths (2 m, 4 m, and 6 m), and the horizontal well had a diameter of 0.8 m and a length of 20 m at both sides. The effects of different ignition positions, well depths, and gas compositions and concentrations on the explosion characteristics and rules governing the propagation of flammable gases in a municipal sewage pipeline were investigated. The findings suggest that different ignition positions (at the top, middle, and bottom of the inspection well) did not lead to a significant difference between peak explosion pressure and temperatures but had a substantial influence on the propagation velocity of the explosion flame near the corner of the junction between the vertical inspection well and the horizontal well. Different inspection well depths had no significant impact on the peak explosion pressure or temperature but had a substantial effect on the propagation velocity of the explosion flame at the bottom of the well. Compared with a methane (CH4) explosion at a concentration of 6%, the peak explosion pressure, peak explosion temperature, and flame propagation velocity of a CH4 and oil-gas mixture at a concentration ratio of 6% : 1% were found to be significantly higher. With increasing oil-gas concentrations (2%, 4%, and 6%), the peak pressure, temperature, and flame propagation velocity continued to decrease. The findings of this study can help prevent explosion accidents in municipal sewage pipelines and provide a reference to support the establishment of related standards.

scholarly journals Effect of Pristine Palygorskite Powders on Explosion Characteristics of Methane-Air Premixed Gas

Energies ◽  
2018 ◽  
Vol 11 (10) ◽  
pp. 2496 ◽  
Author(s):  
Yimin Zhang ◽  
Yan Wang ◽  
Ligang Zheng ◽  
Tao Yang ◽  
Jianliang Gao ◽  
...  
Keyword(s):  
Flame Propagation ◽  
Low Cost ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Flame Propagation Velocity ◽  
Explosion Pressure ◽  
Pyrolysis Characteristics ◽  
Explosion Suppression ◽  
Adsorption Desorption ◽  
Methane Explosion

In this study, pristine palygorskite powders were used as the inhibition materials to suppress the explosion of methane-air premixed gas for the first time. The composition, porosity and pyrolysis characteristics of the powders were tested by X-ray diffraction (XRD), energy dispersive spectrometry (EDS), N2 adsorption-desorption and Thermogravimetry-differential scanning calorimetry (TG-DSC) techniques. The effects of pristine palygorskite powders concentration on the explosion pressure and the average velocity of flame propagation of the 9.5% methane-air premixed gas were tested by a 20 L spherical explosion system and a 5 L pipeline explosion system. The results indicated the pristine palygorskite powders possess a considerable suppression property on methane explosion. When the mass concentration of pristine palygorskite powders was 0.20 g·L−1, the max-pressure of methane explosion was decreased by 23.9%. The methane explosion flame propagation velocity was inhibited obviously. Owing to the excellent inhibitory performance and the advantage of low-cost and environmental harmlessness, pristine palygorskite powders are potential new materials for the application on gas explosion suppression.

scholarly journals Effects of Flame Propagation Velocity and Turbulence Intensity on End-Gas Auto-Ignition in a Spark Ignition Gasoline Engine

Energies ◽  
2020 ◽  
Vol 13 (19) ◽  
pp. 5039
Author(s):  
Lei Zhou ◽  
Xiaojun Zhang ◽  
Lijia Zhong ◽  
Jie Yu
Keyword(s):  
Flame Propagation ◽  
Turbulence Intensity ◽  
Propagation Velocity ◽  
Gasoline Engine ◽  
Pressure Oscillation ◽  
Spark Ignition ◽  
Flame Propagation Velocity ◽  
Eddy Simulation ◽  
Auto Ignition ◽  
Large Eddy

Knocking is a destructive and abnormal combustion phenomenon that hinders modern spark ignition (SI) engine technologies. However, the in-depth mechanism of a single-factor influence on knocking has not been well studied. Thus, the major aim of the present study is to study the effects of flame propagation velocity and turbulence intensity on end-gas auto-ignition through a large eddy simulation (LES) and a decoupling methodology in a downsized gasoline engine. The mechanisms of end-gas auto-ignition as well as strong pressure oscillation are qualitatively analyzed. It is observed that both flame propagation velocity and turbulence have a non-monotonic effect on knocking intensity. The competitive relationship between flame propagation velocity and ignition delay of the end gas is the primary reason responding to this phenomenon. A higher flame speed leads to an increase in the heat release rate in the cylinder, and consequently, quicker increases in the temperature and pressure of the unburned end-gas mixture are obtained, leading to end-gas auto-ignition. Further, the coupling of a pressure wave and an auto-ignition flame front results in super-knocking with a maximum peak of pressure of 31 MPa. Although the turbulence indirectly influences the end-gas auto-ignition by affecting the flame propagation velocity, it can accelerate the dissipation of radicals and heat in the end gas, which significantly influences knocking intensity. Moreover, it is found that the effect of turbulence is more pronounced than that of flame propagation velocity in inhibiting knocking. It can be concluded that the intensity of the pressure oscillation depends on the unburned mixture mass as well as the local thermodynamic state induced by flame propagation and turbulence, with mutual interactions. The present work is expected to provide valuable perspective for inhibiting super-knocking of an SI gasoline engine.

Methodologies for Flame Propagation Velocity Determination in Spark Ignited Engines

2017 ◽  
Author(s):  
Guilherme Bastos Machado ◽  
José Eduardo Mautone Barros ◽  
Sérgio Leal Braga ◽  
Carlos Valois Maciel Braga
Keyword(s):  
Flame Propagation ◽  
Propagation Velocity ◽  
Flame Propagation Velocity
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