A tangent linear approximation of the ignition delay time. I: Sensitivity to rate parameters

Abstract
A tangent linear approximation is developed to estimate the sensitivity of the ignition delay time with respect to individual rate parameters in a detailed chemical mechanism. Attention is focused on a gas mixture reacting under adiabatic, constant-volume conditions. The uncertainty in the rates of elementary reactions is described in terms of uncertainty factors, and are parameterized using independent canonical random variables. The approach is based on integrating the linearized system of equations governing the evolution of the partial derivatives of the state vector with respect to individual random variables, and a linearized approximation is developed to relate the ignition delay sensitivity to the scaled partial derivatives of temperature. The efficiency of the approach is demonstrated through applications to chemical mechanisms of different sizes. In particular, the computations indicate that for detailed reaction mechanisms the TLA leads to robust local sensitivity predictions at a computational cost that is order-of-magnitude smaller than that incurred by finite-difference approaches based on one-at-a-time rate perturbations.

Citation
Almohammadi, S., Hantouche, M., Le Maître, O. P., & Knio, O. M. (2021). A tangent linear approximation of the ignition delay time. I: Sensitivity to rate parameters. Combustion and Flame, 230, 111426. doi:10.1016/j.combustflame.2021.111426

Acknowledgements
The research reported in this publication was supported by King Abdullah University of Science and Technology (KAUST). The authors are grateful to three anonymous reviewers for comments and suggestions that resulted in significant improvements to this manuscript. The TLA codes are available from the authors upon request.

Publisher
Elsevier BV

Journal
Combustion and Flame

DOI
10.1016/j.combustflame.2021.111426
10.1016/j.combustflame.2021.111677

Additional Links
https://linkinghub.elsevier.com/retrieve/pii/S0010218021001656

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