| 1. |
- Han, Xinlu, et al.
(författare)
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Over-rich combustion of CH4, C2H6, and C3H8 +air premixed flames investigated by the heat flux method and kinetic modeling
- 2019
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Ingår i: Combustion and Flame. - : Elsevier BV. - 0010-2180. ; 210, s. 339-349
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Tidskriftsartikel (refereegranskat)abstract
- An uncommon non-monotonic behavior of the temperature dependence of adiabatic laminar burning velocity has been found in over-rich methane+air flames at equivalence ratio, ϕ = 1.4. To find out the universality and reasons of this turning point, methane, ethane and propane + air flames are studied both experimentally by the heat flux method and numerically using GRI-mech, USC-mech, UCSD-mech, FFCM mech, and Aramco mech over ϕ = 0.6–1.8, at unburned temperatures up to 368 K, and atmospheric pressure. Results show that the over-rich phenomena stem from a unique flame structure, where, after the flame front, H2O is reduced to H2 and C2Hx (x>1) is oxidized to CO, causing the temperature overtone (super adiabatic flame temperature), while some key reactions important for flame propagation changing their sensitivity signs. Inside the flame front, the importance of CH3 overwhelms other radicals like OH and H. By these distinguishing features, a method using temperature overtone to identify accurate turning points of over-rich regime is demonstrated.
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| 2. |
- Han, Xinlu, et al.
(författare)
-
Parametrization of the temperature dependence of laminar burning velocity for methane and ethane flames
- 2019
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Ingår i: Fuel. - : Elsevier BV. - 0016-2361. ; 239, s. 1028-1037
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Tidskriftsartikel (refereegranskat)abstract
- The power exponent α in the temperature dependence of laminar burning velocity [Formula presented]=[Formula presented]α is usually considered an empirical parameter extracted from measurements performed at different temperatures. In this paper an analytical derivation of α is proposed, calculating the power exponent from the overall activation energy as: αTu 0→Tu =[Formula presented]·X+x. This relation is verified against experimental burning velocity data measured with the heat flux method and chemical kinetic models for flames with equivalence ratios, Φ, from 0.6 to 1.6 at up to 368 K unburned gas temperature and 1atm. Both methane and ethane were used as fuel. Laminar burning velocity predictions at elevated temperatures are made using proposed relation and the resulting values are in good agreement with existing data for methane flames up to 500 K. This indicates that the proposed mathematical derivation of α is accurate. In addition to providing a reliable extrapolation of the burning velocity at varying temperatures, isolating the temperature dependence of the power exponent α enables more accurate quantification of other factors, e.g., Φ, the unburned gas temperature and pressure, that influence laminar burning velocity. Additionally, it provides a simple means to evaluate the overall activation energy, Ea.
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