Development and Application of a Transported Probability Density Function Method on Unstructured Three-Dimensional Grids for the Prediction of Nitric Oxides

Abstract

The present work explores the capability of the transported probability density function (PDF) method to predict nitric oxide (NO) formation in turbulent combustion. To this end a hybrid finite-volumelLagrangian Monte Carlo method is implemented into the THETA code ofthe German Aerospace Center (DLR). In this hybrid approach the tr-ansported PDF method governs the evolution of the thermochemical variables, wher-eas the flow field evolution is computed with a Reynolds-averaged Navier-Stokes (RANS) method. The method is used to compute a turbulent hydrogen-air flame and a methaneair flame and computational results are compared to experimental data. In order to assess the advantages of the transported PDF method, the flame computations are repeated with the "laminar chemistry" approach as well as with an "assumed PDF" method, which are both computationally less expensive. The present study reveals that the tr-ansported PDF method provides the highest accwacy in predicting the overall flame structure and nitric oxide formation.

Transported PDF simulation of auto-ignition of a turbulent methane jet in a hot, vitiated coflow

“…In order to solve the system (13)-(15) a hybrid Finite-Volume/Lagrangian Monte-Carlo Method is implemented into the computational-fluid-dynamics (CFD) code THETA of DLR [62,85], which has been already used in earlier PDF simulations of reactive flows [30,31]. In this hybrid approach, turbulence time-and length-scales and Favre averaged flow velocities (which are required for the solution of Eqs.…”

“…As stated before, the length scale of turbulence is assumed to be 7 % of the hydraulic diameter and the turbulence intensity is taken to be 10 % [99]. [30,31], where the effect of particle number is studied, this number of particles is sufficient for this kind of simulation. To incorporate the effect of chemical kinetics GRI 3.0 reaction mechanism [87] is used in this work with 52 species and 323 reactions.…”