Available online at www.sciencedirect.com Proceedings of the Combustion Institute 36 (2017) 645–653 www.elsevier.com/locate/proci Dynamic adaptive chemistry via species time-scale and Jacobian-aided rate analysis Wenwen Xie a,b , Zhen Lu a , Zhuyin Ren a,b,∗ , Lingyun Hou b a Center for Combustion Energy, Tsinghua University, Beijing, China b School of Aerospace Engineering, Tsinghua University, Beijing, China Received 2 December 2015; accepted 25 July 2016 Available online 6 October 2016 Abstract A new on-the-ly mechanism reduction method is presented for dynamic adaptive chemistry (DAC), in which chemical species are categorized into active, directly coupled, and inconsequential species through time-scale and Jacobian-aided rate analysis (TSRA) with given instantaneous local composition. Chemistry integration is simpliied by solving only parts of species with the inconsequential species being treated frozen. The method applies intuitive error control on species rates-of-change for the active species and requires no problem-dependent parameters such as starting species. In addition, it can guarantee element conservation and directly take transport lux into account for chemistry reduction. The new method has been validated in auto-ignition, unsteady perfectly stirred reactor (PSR) and 1-D lame propagation of methane/air mix- ture with the 53-species GRI-Mech 3.0 and n-heptane/air mixture with the 561-species LLNL mechanism. It shows that the proposed Jacobian analysis can successfully identify important low-concentration slowly- varying intermediate species as active species during the ignition process. Compared to directed relation graph (DRG) based DAC, TSRA yields more accurate predictions of ignition delay time and composition together with slight improvement in eficiency for methane/air auto-ignition. For the n-heptane/air mixture, TSRA accurately reproduces the challenging two-stage ignition and negative temperature coeficients over a wide range of pressures and initial temperatures. The importance of transport lux on dynamic reduction is inves- tigated in unsteady PSR, showing that TSRA dynamically adjusts the local mechanism size with the relative signiicance of chemical reaction and it offers greater reduction in regions where transport processes are sig- niicant. The 1-D lame propagation validates the generality of TSRA method for inhomogeneous reacting lows. Results also show that TSRA has effective and more universal error control. For TSRA, a single thresh- old ε = 1 × 10 −4 applies to all the tests considered. In contrast, the appropriate reduction threshold for DRG is problem-dependent. © 2016 by The Combustion Institute. Published by Elsevier Inc. Keywords: Dynamic adaptive chemistry; Mechanism reduction; Rate analysis; Transport lux ∗ Corresponding author. E-mail addresses: zhuyinren@tsinghua.edu.cn, zhuyinren@gmail.com (Z. Ren). 1. Introduction Detailed mechanisms of hydrocarbon fuels have been developed to enable accurate predic- tion of the physicochemical processes in practical http://dx.doi.org/10.1016/j.proci.2016.07.105 1540-7489 © 2016 by The Combustion Institute. Published by Elsevier Inc.