Joint probability distribution of Arrhenius parameters in reaction model optimization and uncertainty minimization

Abstract

Abstract The method of uncertainty minimization by polynomial chaos expansions is extended to Arrhenius prefactor and activation energy co-optimization and uncertainty minimization. A covariance matrix is formulated to describe the joint probability distribution of the reaction rate parameters. The method is tested on a recently proposed foundational fuel chemistry model using 60 H2 and H2/CO flame speeds as the targets. The results show that co-optimizing A and Ea did not produce appreciable improvements in the ability of the reaction model to better predict the flame targets. It does yield reduction in the temperature-dependent uncertainty band of the rate coefficients of several key reactions. The importance of additional experimental and theoretical studies needed for the CO+OH→CO2+H, HO2+H→H2+O2 and HO2+H→2OH reactions is highlighted.