Abstract
Identifying combustion regimes in terms of premixed and non-premixed characteristics is an important task for understanding combustion phenomena and the structure of flames. A quasi-DNS database of the compositionally inhomogeneous partially premixed Sydney/Sandia flame in configuration FJ-5GP-Lr75-57 is used to directly compare different types of flame regime markers from literature. In the simulation of the flame, detailed chemistry and diffusion models are utilized and no turbulence and combustion models are used as the flame front and flow are fully resolved near the nozzle. This allows evaluating the regime markers as a post-processing step without modeling assumptions and directly comparing regime markers based on gradient alignment, drift term analysis and gradient free regime identification. The goal is not to find the correct regime marker, which might be impossible due to the different set of assumptions of every marker and the generally vague definition of the partially premixed regime itself, but to compare their behavior when applied to a resolved turbulent flame with partially premixed characteristics.
Highlights
In many technically relevant combustion devices, flames develop in conditions where fuel and oxidizer are not perfectly mixed
In the last few years alone, a large number of works has used the concept of the Takeno flame index to study flames and improve their prediction: it was used to understand the structure of blue swirling flames (Chung et al 2019), identify flame regimes in thickened flame simulations of spray flames (Hu and Kurose 2019b; Dressler et al 2020) and study the influence of evaporation (Wei et al 2018) as well as devolatilization (Zhang et al 2017)
Three types of fundamentally different flame regime markers from the literature have been applied to a simulation database of the compositionally inhomogeneous, partially premixed turbulent Sydney/Sandia flame in configuration FJ-5GP-Lr75-57, where the flame is fully resolved
Summary
In many technically relevant combustion devices, flames develop in conditions where fuel and oxidizer are not perfectly mixed. The drift term approach by Wu and Ihme is not necessarily a marker for premixed and non-premixed regions Instead, it shows how close the trajectory of a quantity of interest, e.g. a species mass fraction, on the manifold of a combustion model is to the local flow field conditions. By introducing a drift term, which measures how well a given manifold-based combustion model can represent the flame based on the current flow field, they defined a new regime marker. This approach significantly increased the accuracy of the results compared to using only one mixture fraction for the cases with inhomogeneous inlets and showed that the combustion near the nozzle is predominantly premixed They assessed the influence of subgrid filter probability density functions (Perry and Mueller 2019) for this flame. In the “Appendix”, different regime markers from the literature are discussed in detail
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
