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Abstract

In this study, the turbulent non-premixed methane-air flame is simulated to determine the effect of air velocity on the length of flame, temperature distribution and mole fraction of species. The computational fluid dynamics (CFD) technique is used to perform this simulation. To solve the turbulence flow, k-ε model is used. In contrast to the previous works, in this study, in each one of simulations the properties of materials are taken variable and then the results are compared. The results show that at a certain flow rate of fuel, by increasing the air velocity, similar to when the properties are constant, the width of the flame becomes thinner and the maximum temperature is higher; the penetration of oxygen into the fuel as well as fuel consumption is also increased. It is noteworthy that most of the pollutants produced are NOx, which are strongly temperature dependent. The amount of these pollutants rises when the temperature is increased. As a solution, decreasing the air velocity can decrease the amount of these pollutants. Finally, comparing the result of this study and the other work, which considers constant properties, shows that the variable properties assumption leads to obtaining more exact solution but the trends of both results are similar.

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Authors and Affiliations

Zafar Namazian
Heidar Hashemi
Farideh Namazian
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Abstract

Gas explosions are major disasters in coal mining, and they typically cause a large number of deaths, injuries and property losses. An appropriate understanding of the effects of combustible gases on the characteristics of methane explosions is essential to prevent and control methane explosions. FLACS software was used to simulate an explosion of a mixture of CH4 and combustible gases (C2H4, C2H6, H2, and CO) at various mixing concentrations and different temperatures (25, 60, 100, 140 and 180℃). After adding combustible gases to methane at a constant volume and atmospheric pressure, the adiabatic flame temperature linearly increases as the initial temperature increases. Under stoichiometric conditions (9.5% CH4-air mixture), the addition of C2H4 and C2H6 has a greater effect on the adiabatic flame temperature of methane than H2 and CO at different initial temperatures. Under the fuel-lean CH4-air mixture (7% CH4-air mixture) and fuel-rich mixture (11% CH4-air mixture), the addition of H2 and CO has a greater effect on the adiabatic flame temperature of methane. In contrast, the addition of combustible gases negatively affected the maximum explosion pressure of the CH4-air mixture, exhibiting a linearly decreasing trend with increasing initial temperature. As the volume fraction of the mixed gas increases, the adiabatic flame temperature and maximum explosion pressure of the stoichiometric conditions increase. In contrast, under the fuel-rich mixture, the combustible gas slightly lowered the adiabatic flame temperature and the maximum explosion pressure. When the initial temperature was 140℃, the fuel consumption time was approximately 8-10 ms earlier than that at the initial temperature of 25℃. When the volume fraction of the combustible gas was 2.0%, the consumption time of fuel reduced by approximately 10 ms compared with that observed when the volume fraction of flammable gas was 0.4%.
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Authors and Affiliations

Zhenmin Luo
1 2
ORCID: ORCID
Litao Liu
1 2
ORCID: ORCID
Shuaishuai Gao
1 2
ORCID: ORCID
Tao Wang
1 2 3
ORCID: ORCID
Bin Su
1 2
ORCID: ORCID
Lei Wang
1 2
ORCID: ORCID
Yong Yang
4 2
ORCID: ORCID
Xiufang Li
4
ORCID: ORCID

  1. Xi’an University of Science and Technology, School of Safety Science & Engineering, 58, Yanta Mid. Rd., Xi’an, 710054, Shaanxi, PR China
  2. Shaanxi Key Laboratory of Prevention and Control of Coal Fire, 58, Yanta Mid. Rd, Xi’an, 710054, Shaanxi, PR China
  3. Xi’an University of Science and Technology, Postdoctoral Program, 58, Yanta Mid. Rd., Xi’an 710054, Shaanxi, PR China
  4. Xi’an University of Science and Technology, School of Safety Science & Engineering, 58, Yanta Mid. Rd., Xi’an, 710054, Shaanxi, PR

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