Relative influence of soot oxidation kinetics and subfilter soot-turbulence interactions on soot evolution in turbulent nonpremixed flames

Large eddy simulation of soot evolution in turbulent nonpremixed bluff body flames

“…The total duration of simulation is 150 ms, which is equivalent to approximately 5 flow-through times through along the sooting region of the flame (x/D ≈ 140), which is sufficient for statistical convergence. The f v profiles show that BMMSM predicts the same or lower soot volume fraction compared to HMOM, which is favorable because this modeling framework with HMOM has been shown to overpredict the volume fraction in such configurations [22,43]. For both the mean soot volume fraction and the mean soot number density, the BMMSM results with fewer sections are comparable to HMOM, which is consistent with prior work in laminar flames [20].…”

“…Finally, and similar to HMOM [10,18], an additional transport equation for the square of the total number density is solved to compute the subfilter intermittency, which mathematically represents the weights between sooting and non-sooting modes. This model was extensively validated in turbulent sooting flames using HMOM [5,8,19] and recently using BMMSM [16].…”

“…To close turbulence-chemistry subfilter interactions, convolution is performed for each manifold solution in the database with a presumed beta subfilter Probability Density Function (PDF) for the mixture fraction. The resulting thermochemical database is then stored in a lookup table, in terms of the filtered mixture fraction Z, subfilter mixture fraction variance Z v , filtered progress variable C, and filtered heat loss parameter H. To close turbulence-soot subfilter interactions, a presumed soot subfilter PDF model that captures finite-rate oxidation of soot is employed, following the work of Maldonado Colmán et al [22], which was validated for turbulent nonpremixed jet flames [22,43] and bluff body flames [44]. This model is based on the presumed bimodal PDF of Mueller and Pitsch [27], which considered sooting and non-sooting modes.…”