(312f) A Novel Two-Phase Filtered Density Function Approach for Turbulent Spray Combustion

Turbulent spray combustion is an industrially relevant flow found in aircraft engines, stationary turbines, diesel and spark ignition engines, industrial furnaces, and chemical reactors. In these flows, a liquid reactant in the form of droplets is dispersed in a turbulent carrier-gas flow. Spray flames exhibit complex morpholgies and contain premixed, non-premixed, and partially-premixed propagation mechanisms. A predictive model for this challenging system will have direct impact in a wide range of industries. The objective of this work is to develop a state-of-the-art two-phase filtered-density function approach for turbulent spray combustion. The entire formulation is based on the large-eddy simulation methodology that captures large-scale mixing accurately. This formulation has multiple advantages. First, the chemical source term in the gas-phase appears requires no modeling. Second, detailed models for the turbulent spray dispersion process can be formulated. Third, nonequilibrium sub-filter models for the gas-phase turbulent flux can be specified. We demonstrate that without addressing these issues, a predictive model for turbulent spray combustion cannot be formulated. DNS computations are used to test the sub-filter closures developed. Further, a unique detailed computational method is formulated for understanding the flame propagation in a representative droplet group is presented.