Optimized single-step (OSS) chemistry for auto-ignition of heterogeneous mixtures

With the objective of recovering the values of ignition delays of reactive heterogeneous mixtures a singlestep chemistry model has been developed. The corresponding model extends a recent optimization procedure introduced to describe flame propagation in heterogeneous media featuring composition variations (equivalence ratio and temperature) in the fresh reactants or containing residual burned gases (RBG). It is based on the use of an optimized virtual species and a tabulation of the pre-exponential coefficient of an Arrhenius law. The main results of high activation energy asymptotics (AEA) are first recalled to put in evidence the key parameters and the dependence of the ignition delay on the corresponding quantities. The optimization procedure is then applied to these parameters, namely, the pre-exponential factor K and the activation energy E-a of the associated single-step Arrhenius law. An efficient tabulation method benefiting from both rapid access and low storage is proposed for the composition variable (the mixture fraction, in the present case). Finally, the restitution of both ignition and propagation features is ensured through the consideration of the cross-over temperature. The performance of the resulting model is then assessed through comparisons with data obtained from detailed chemistry computations used as reference in several conditions of increasing complexity. (C) 2021 The Combustion Institute. Published by Elsevier Inc. All rights reserved.

Automated summary

A single-step chemistry model has been developed to recover the ignition delays of reactive heterogeneous mixtures, with an optimization procedure applied to key parameters. High activation energy asymptotics have been recalled to highlight the dependence of ignition delay on corresponding quantities. An efficient tabulation method is proposed for composition variables, ensuring the restitution of ignition and propagation features through the consideration of cross-over temperature.