TY - CONF

T1 - Uncertainty reduction in laminar flame speed extrapolation from expanding spherical flames

AU - Huo, Jialong

AU - Yang, Sheng

AU - Ren, Zhuyin

AU - Law, C. K.

N1 - Funding Information:
The research at Tsinghua University was funded by National Natural Science Foundation of China 91441202, while that at Princeton University by the US National Science Foundation.
Funding Information:
H2/air and C3H8/air mixtures are studied to investigate effects of the flame radius range on laminar flame speed extrapolation from expanding spherical flames. The experimental results demonstrate that Lb/Rf is the controlling parameter of the accuracy of different extrapolation formulas. An empirical criterion for extrapolation uncertainty based on Lb/Rf is proposed, which indicates that Lb,,LC/Rf,,mid <0.05 (0.03) is need so that the extrapolation uncertainty can be limited to 5% (2%) under experimental conditions of positive Markstein length. Acknowledgements The research at Tsinghua University was funded by National Natural Science Foundation of China 91441202, while that at Princeton University by the US National Science Foundation. References [1] G.E. Andrews, D. Bradley, Determination of burning velocities: A critical review, Combust. Flame, 18 (1972) 133-153. [2] F.N. Egolfopoulos, N. Hansen, Y. Ju, K. Kohse-Höinghaus, C.K. Law, F. Qi, Advances and challenges in laminar flame experiments and implications for combustion chemistry, Prog. Energ. Combust., 43 (2014) 36-67. [3] F. Wu, W. Liang, Z. Chen, Y. Ju, C.K. Law, Uncertainty in stretch extrapolation of laminar flame speed from expanding spherical flames, P. Combust. Inst., 35 (2015) 663-670. [4] Z. Chen, On the accuracy of laminar flame speeds measured from outwardly propagating spherical flames: Methane/air at normal temperature and pressure, Combust. Flame, 162 (2015) 2442-2453. [5] Z. Chen, On the extraction of laminar flame speed and Markstein length from outwardly propagating spherical flames, Combust. Flame, 158 (2011) 291-300. [6] A.P. Kelley, C.K. Law, Nonlinear effects in the extraction of laminar flame speeds from expanding spherical flames, Combust. Flame, 156 (2009) 1844-1851. [7] W. Liang, F. Wu, C.K. Law, Extrapolation of laminar flame speeds from stretched flames: Role of finite flame thickness. Proceedings of the Combustion Institute 1 (2017) 1137-1143. [8] J. Jayachandran, A. Lefebvre, R. Zhao, F. Halter, E. Varea, B. Renou, F.N. Egolfopoulos, A study of propagation of spherically expanding and counterflow laminar flames using direct measurements and numerical simulations, P. Combust. Inst., 35 (2015) 695-702. [9] F. Halter, T. Tahtouh, C. Mounaïm-Rousselle, Nonlinear effects of stretch on the flame front propagation, Combust. Flame, 157 (2010) 1825-1832. [10] M.P. Burke, M. Chaos, Y. Ju, F.L. Dryer, S.J. Klippenstein, Comprehensive H2/O2 Kinetic Model for High-Pressure Combustion, Int. J. Chem. Kinet. (2011).

PY - 2017

Y1 - 2017

N2 - The reduction of extrapolation uncertainty for laminar flame speed is studied using expanding spherical flame measurements under positive Markstein length (Lb>0) conditions. The performance of three extrapolation formulas including one linear and two non-linear formulas were examined under a wide range of experimental conditions of various flame radius ranges. It is found that the ratio of Lb and the flame radius Rf used for extrapolation is the controlling parameter of the extrapolation uncertainty. For conditions with Lewis number close to unity, the extrapolation uncertainty is small due to small value of (Lb/Rf)2. However, for mixtures with supra-unity Lewis number, the (Lb/Rf)2 terms in the expanded form of the extrapolation formulas are large at commonly used Rf, resulting in large uncertainties in the extrapolated laminar flame speeds. The extrapolation uncertainty can be effectively reduced using flame measurements with large flame radius range as demonstrated in a newly built constant-pressure, dual-chamber experimental rig of large dimension.

AB - The reduction of extrapolation uncertainty for laminar flame speed is studied using expanding spherical flame measurements under positive Markstein length (Lb>0) conditions. The performance of three extrapolation formulas including one linear and two non-linear formulas were examined under a wide range of experimental conditions of various flame radius ranges. It is found that the ratio of Lb and the flame radius Rf used for extrapolation is the controlling parameter of the extrapolation uncertainty. For conditions with Lewis number close to unity, the extrapolation uncertainty is small due to small value of (Lb/Rf)2. However, for mixtures with supra-unity Lewis number, the (Lb/Rf)2 terms in the expanded form of the extrapolation formulas are large at commonly used Rf, resulting in large uncertainties in the extrapolated laminar flame speeds. The extrapolation uncertainty can be effectively reduced using flame measurements with large flame radius range as demonstrated in a newly built constant-pressure, dual-chamber experimental rig of large dimension.

KW - Extrapolation uncertainty

KW - Laminar flame speed

KW - Markstein length

KW - Spherical flames

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M3 - Paper

AN - SCOPUS:85048948188

T2 - 10th U.S. National Combustion Meeting

Y2 - 23 April 2017 through 26 April 2017

ER -