Temperature dependence of the laminar burning velocity for n-heptane and iso-octane/air flames

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Temperature dependence of the laminar burning velocity for n-heptane and iso-octane/air flames. / Han, Xinlu; Wang, Zhihua; He, Yong; Wang, Shixing; Liu, Yingzu; Konnov, Alexander A.

In: Fuel, Vol. 276, 118007, 2020.

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Han, Xinlu ; Wang, Zhihua ; He, Yong ; Wang, Shixing ; Liu, Yingzu ; Konnov, Alexander A. / Temperature dependence of the laminar burning velocity for n-heptane and iso-octane/air flames. In: Fuel. 2020 ; Vol. 276.

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TY - JOUR

T1 - Temperature dependence of the laminar burning velocity for n-heptane and iso-octane/air flames

AU - Han, Xinlu

AU - Wang, Zhihua

AU - He, Yong

AU - Wang, Shixing

AU - Liu, Yingzu

AU - Konnov, Alexander A.

PY - 2020

Y1 - 2020

N2 - The heat flux method is advantageous for obtaining adiabatic stretch-less flame and measuring laminar burning velocity, SL, with low uncertainty. However, its implementation is sometimes hampered by the instability, manifested as cellularity of the flame stabilized over a flat perforated burner. This paper summarizes the approaches of flame cellularity abatement on the heat flux burner, which are implemented in the present study for measuring burning velocities of n-heptane and iso-octane/air flames. The combination of approaches helped to effectively overcome the cellularity at the fuel-rich side of the tested flames, and the SL was measured at unburnt temperatures Tu=298K-358K and equivalence ratios ϕ=0.7-1.6, at atmospheric pressure, with the SL uncertainty being evaluated. Numerical simulations were carried out using LLNL mechanism, Chaos mechanism and Luong171 mechanism, and the results agree well with the experimental data. From the obtained experimental and numerical SL data, the temperature coefficients α in [Formula presented] as well as the overall activation energy, Ea, were derived. It was noted that for n-heptane and iso-octane/air flames, the tendencies of the α and Ea against ϕ resemble those for methane, ethane, and propane/air flames. Distinct over-rich flame structures were observed and discussed for n-heptane and iso-octane/air flames around ϕ≥1.5. Moreover, extrapolation proced/ure of the SLmeasurements was validated using analytical presentation of the heat flux method sensitivity, s vs. [Formula presented], and other parameters involved in the data processing, which may help to improve the accuracy of future experiments.

AB - The heat flux method is advantageous for obtaining adiabatic stretch-less flame and measuring laminar burning velocity, SL, with low uncertainty. However, its implementation is sometimes hampered by the instability, manifested as cellularity of the flame stabilized over a flat perforated burner. This paper summarizes the approaches of flame cellularity abatement on the heat flux burner, which are implemented in the present study for measuring burning velocities of n-heptane and iso-octane/air flames. The combination of approaches helped to effectively overcome the cellularity at the fuel-rich side of the tested flames, and the SL was measured at unburnt temperatures Tu=298K-358K and equivalence ratios ϕ=0.7-1.6, at atmospheric pressure, with the SL uncertainty being evaluated. Numerical simulations were carried out using LLNL mechanism, Chaos mechanism and Luong171 mechanism, and the results agree well with the experimental data. From the obtained experimental and numerical SL data, the temperature coefficients α in [Formula presented] as well as the overall activation energy, Ea, were derived. It was noted that for n-heptane and iso-octane/air flames, the tendencies of the α and Ea against ϕ resemble those for methane, ethane, and propane/air flames. Distinct over-rich flame structures were observed and discussed for n-heptane and iso-octane/air flames around ϕ≥1.5. Moreover, extrapolation proced/ure of the SLmeasurements was validated using analytical presentation of the heat flux method sensitivity, s vs. [Formula presented], and other parameters involved in the data processing, which may help to improve the accuracy of future experiments.

KW - Heat flux method

KW - Iso-octane

KW - Laminar burning velocity

KW - n-heptane

KW - Over-rich flame

KW - Temperature dependence

U2 - 10.1016/j.fuel.2020.118007

DO - 10.1016/j.fuel.2020.118007

M3 - Article

AN - SCOPUS:85084510295

VL - 276

JO - Fuel

JF - Fuel

SN - 1873-7153

M1 - 118007

ER -