An Optimized Chemical Kinetic Mechanism for the Accurate Modelling of Low Temperature Combustion of Syngas and Methane

Abstract

Abstract In the present study, the chemical kinetic mechanism DLR SynNG for the combustion of syngas and natural gas is optimized with various experimental data points with a focus on low temperature chemistry. For the optimization approach, the framework of the linear transformation model (linTM) is applied. The linTM was designed to optimize chemical kinetic model parameters with target quantities from a broad range of experimental facilities, like shock tubes, flow reactors, jet stirred reactors or various burner configurations. In this work, the optimization capabilities were extended for data from rapid compression machines (RCM), which are commonly used to investigate the ignition behavior under low temperature combustion conditions. RCM are typically simulated with homogeneous reactors with constrained pressure or volume profiles derived from the experiments. With the implementation of the RCM into the linTM framework, a novel parameterization approach for the simulation with constrained volume profiles is proposed. This new approach results in significantly reduced computational costs of RCM simulations and increased numerical stability for solving the underlying ordinary differential equation systems. Since several thousand RCM simulations throughout the optimization process are needed, this is highly beneficial for the applied optimization of the chemical kinetic mechanism. In detail, the rate coefficients of sensitive reactions were optimized within their uncertainty boundaries. The optimized chemical kinetic model is capable of reproducing a broad range of experimental data for a large field of boundary conditions and fuel mixtures of hydrogen, carbon monoxide, methanol and methane. The experimental data include ignition delay times, laminar burning velocities as well as species profiles from flow reactors, jet stirred reactors and different laminar flame configurations.