Reduced chemical kinetic model for CH4-air non-premixed flames including excited and charged species

Electric fields can impact small laminar flames by changing their shape and overall behavior by acting on charged species produced in combustion. However, no reduced chemical kinetic model has been developed considering both major species and minor species related to flame characterization and flame behavior in the presence of an electric field. This study presents a reduced chemical kinetic model for methane-air combustion which includes minor excited species (CH* and OH*) and charged species (H3O+, HCO+, C2H3O+, CH5O+, O-2(-), OH-, e(-), CO3- , CHO2- , O-, CHO3-). The results employing the reduced chemistry model have been validated for a two-dimensional flame geometry by comparison with (i) detailed chemistry simulation results for species location and peak values, and (ii) experimental CH* chemiluminescence location, considering the self-repulsion of charges yet without externally applied electric field to the flame. This reduced chemical kinetic model, with 45 species and 216 reactions, shows a computational demand one-third that of employing its equivalent detailed chemistry (83 species and 394 reactions). The reduction is modest but significant considering that high fidelity is needed to capture the behavior of the chemi-ion and chemiluminescent species. Future works will involve the use of this model for simulations predicting flame behavior with applied electric field (i.e., field strength not equal 0 kV/cm). (c) 2023 The Combustion Institute. Published by Elsevier Inc. All rights reserved.

Automated summary

Electric fields can alter the shape and behavior of small laminar flames by affecting charged species produced during combustion. This study introduces a simplified chemical kinetic model for methane-air combustion that incorporates minor excited species (CH* and OH*) and charged species (H3O+, HCO+, C2H3O+, CH5O+, O-2(-), OH-, e(-), CO3- , CHO2- , O-, CHO3-). The model's results have been verified through comparisons with detailed chemistry simulations and experimental observations, showcasing its computational efficiency compared to the equivalent detailed chemistry model. This simplified model will be utilized for simulations involving applied electric fields in future research.