Conditional Moment Closure for Turbulent Premixed Flames

Abstract

The conditional moment closure (CMC) method has been successfully applied to various non-premixed combustion systems in the past, but its application to premixed flames is not fully tested and validated. The main difficulty is associated with the modeling of conditional scalar dissipation rate of the conditioning scalar, the progress variable. A simple algebraic model for the conditional dissipation rate is validated using DNS results of a V-flame. This model along with the standard k–ϵ turbulence modeling is used in computations of stoichiometric pilot stabilized Bunsen flames using the RANS-CMC method. A first-order closure is used for the conditional mean reaction rate. The computed non reacting and reacting scalars are in reasonable agreement with the experimental measurements and are consistent with earlier computations using flamelets and transported PDF methods. Sensitivity to chemical kinetic mechanism is also assessed. The results suggest that the CMC may be applied across the regimes of premixed combustion.

Keywords:

• Conditional moment closure (CMC)
• Conditional scalar dissipation rate
• Numerical modeling
• Turbulent premixed flames

ACKNOWLEDGMENTS

The support from EPSRC and Siemens through an ICASE award is acknowledged. The support of Cambridge European Trust is acknowledged.