Modeling ethanol spray jet flame in hot-diluted coflow with transported PDF

MILD Combustion, also known as flameless combustion, is attracting wide scientific interest due to its potential of high efficiency and low NOx emission. This paper focuses on the numerical modeling of one of the ethanol spray flame cases from the Delft Spray-in-Hot-Coflow (DSHC) burner, which has been used to study MILD oxidation of liquid fuels. The study has been carried out following the approach of dilute spray simulation. To properly account the turbulent two-phase flow system, a joint velocity-scalar PDF for continuous phase, and a joint PDF of droplet parameters for dispersed phase are employed respectively. Due to the high-dimensionality, the joint PDFs are solved by a Monte Carlo particle method, therefore it is refered to as 'Lagrangian-Lagrangian' approach. The evolution of gas phase composition is described by a Flamelet Generated Manifold (FGM) and the LMSE micro-mixing model. The droplet heating and evaporation processes are modeled with a parabolic temperature profile model. Validation of this modeling approach is carried out by comparison with experimental measurements. Results show that the spray behavior is successfully reproduced; the predicted droplet mean velocity components profiles for all droplet size classes are in very good agreement with the experimental data at various axial locations. Droplet Sauter Mean Diameter (SMD) have been accurately predicted. Gas phase velocity also matches well with experimental data. Gas phase temperature is in reasonable agreement with the experiment, however, it is under predicted at the near axis region. Improvement of the accuracy on temperature prediction can be made by using a non-adiabatic FGM table including an enthalpy variable.