Conditional Source-term Estimation (CSE) and Conditional Moment Closure (CMC) in relation to piloted jet flames: a study of similarities and differences

Abstract

Direct side-by-side comparison of the Sandia flames is used to examine Conditional Moment Closure (CMC) and Conditional Source-term Estimation (CSE). The purpose of this research is to compare the efficacy of various modeling approaches under similar situations and computational frameworks. We evaluate the accuracy of CMC and CSE predictions against extensive experimental data. In the instance of Sandia flame D, the turbulent flow and mixing fields predicted by CMC and CSE are identical close to the nozzle exit, in accordance with the actual observations, but they diverge farther downstream. Good agreement exists between the experimental results obtained downstream of the nozzle for lean mixtures and the conditional mass fractions calculated using CMC and CSE for the principal species. There are several axial sites for fuel-rich mixes where the conditional mass proportion of methane is underestimated while the conditional mass fraction of water is overestimated. The main features of the experimental profiles are recapitulated by the CMC and CSE conditional mass fractions of the minor species and conditional temperature. However, Sandia flame E is drastically different. It has been determined that RANS, along with boundary conditions established in CMC and certain assumptions made in the chemical tables in CSE, are to blame for the observed differences. Both CMC and CSE Favre-averaged profiles are similar. Time spent running each model in the computer is compared, with CSE coming out on top. Further, some of the benefits and drawbacks of each combustion model are discussed. Results are proven to be of equivalent quality between CMC and CSE when the same numerical techniques, mesh, and boundary conditions are used.