Higher-Order Correlation of Kinetic Parameters from Global Sensitivity Analysis with Consideration of Extinction Phenomena of Non-Premixed Flames

Abstract

The experimental uncertainty factors associated with the chemical kinetic parameters of elementary reactions have a considerable impact on the development of accurate detailed chemical models. Previous Global Sensitivity Analysis (GSA) investigations have shown that, under certain conditions, the variation of chemical parameters within their uncertainty bounds affects combustion properties via both single and joint (second-order) effects. Most of the existing literature focuses on ignition and laminar flame propagation phenomena, whereas, to best of our knowledge, GSA of the extinction limits of non-premixed counterflow flames has never been considered previously. In this work, we perform GSA of ethylene-air flames in near extinction conditions using the High Dimensional Model Representation (HDMR) methodology. By analyzing the results of the HDMR with the emphasis on the extinction strain rate and maximum concentration of acetylene, we first identify the major sources of uncertainty of the chemical model and then quantify the presence of higher-order interactions between parameters and target flame properties. I. Introduction The accurate modeling of finite-rate chemistry is widely recognized as a fundamental step in the process of achieving a complete predictive capability of combustion phenomena occurring in aerospace applications. The compilation and optimization of detailed chemical kinetic models is a complex process that requires several refinements and iterations. The objective of a typical optimization procedure is to find the combination of chemical kinetic parameters that reproduces a series of target combustion properties. The presence of the experimental uncertainties associated with the reaction rate constants defines the parameter space of the compiled chemical kinetic model. Because of the non-linear nature of most chemical phenomena, under certain conditions, the influence of chemical parameters on combustion properties of interest must take into account both single and joint (higher order) effects. Understanding how the uncertainty of parameters and their higher-order interactions affect target combustion properties is of paramount importance in chemical kinetic modeling. Even though recent investigations have studied uncertainty propagation and high-order interactions of chemical parameters using several canonical combustion cases, 1{3 the important phenomenon of non-premixed extinction has been overlooked. In this work we present a Global Sensitivity Analysis (GSA) of non-premixed flames in near-extinction conditions and our primary objective is to quantify the major sources of uncertainty in the evaluation of the extinction strain rate, aext, of non-premixed ethyleneair flames. In addition, given the current interest in the analysis of soot precursor formation in ethylene-air flames, we also include the maximum concentration of acetylene, known to play a key role in the synthesis of the first PAH through the so-called HACA mechanism, 4 as a further objective of the GSA.