Multi-regime turbulent spray combustion modeling by similarity mapping

In turbulent spray combustion modeling, the primary challenge comes from the involvement of multiple physical parameters in the flamelet framework. Benefiting from the recently developed similarity mapping for the spray flamelet-progress variable model (SMFPV), the tabulation parameters can be much reduced. In general, spray combustion is characterized by multiple combustion regimes under different working conditions, for instance, the non-premixed flame at the oxidizer side and the premixed flame after complete evaporation of initially small droplets. In the present study, a unified multi-SMFPV model is proposed to account for such a multi-regime issue, by adjusting the spatial range of the evaporation source and adopting the scalar dissipation rate of mixture fraction as an additional entry parameter. Validated against three typical laminar spray counterflow flame cases, multi-SMFPV performs better than other models and aligns closely with the direct integration of the finite-rate chemistry (DIC) results. With regard to the turbulent combustion case, multi-SMFPV is also implemented to simulate the Sydney turbulent spray flame and shows reasonable accuracy.

Novelty and significance

A new version of the similarity mapping spray flamelet progress variable model, named multi-SMFPV, has been proposed to correctly capture multiple combustion regimes encountered in spray combustion. The modeling principles include adjusting the spatial range of the evaporation source and adopting the scalar dissipation rate of mixture fraction as an additional entry parameter to distinguish different combustion regimes. Predicted results of three typical laminar spray counterflow flame cases show significant improvements compared to the former version. Results of the Sydney turbulent spray flame simulation show that multi-SMFPV is also feasible in turbulent situations.