Extended LES-PaSR model for simulation of turbulent combustion

Abstract

In this work, a novel model for Large Eddy Simulations (LES) of high Reynolds moderate Damk ohler number turbulent §ames is proposed. The development is motivated by the need for more accurate and versatile LES combustion models for engineering applications such as jet engines. The model is based on the ¦nite rate chemistry approach in which the ¦ltered species equations of a reduced reaction mechanism are solved prior to closure modeling. The modeling of the ¦ltered reaction rate provides the challenge: as most of the chemical activity, and thus also most of the exothermicity occurs on the subgrid scales, this model needs to be based on the properties of ¦ne-scale turbulence and mixing and Arrhenius chemistry. The model developed here makes use of the similarities with the mathematical treatment of multiphase §ows together with the knowledge of ¦ne-scale turbulence and chemistry obtained by Direct Numerical Simulation (DNS) and experiments. In the model developed, equations are proposed for the ¦ne-structure composition and volume fraction that are solved together with the LES equations for the resolved scales. If subgrid convection can be neglected, the proposed model simpli¦es to the Partially Stirred Reactor (PaSR) model. To validate the proposed LES model, comparisons with experimental data and other LES results are made, using other turbulence chemistry interaction models, for a lean premixed blu¨-body stabilized §ame.

Large Eddy Simulation of Premixed Stratified Swirling Flame Using the Finite Rate Chemistry Approach

“…With the understanding of turbulence-combustion interaction, the different finite rate chemistry models are developed to model the low-pass filtered reaction rates. The PaSR model has been widely tested and proven to have a good performance in turbulent-combustion simulation [28,29]. The development of the PaSR model is based on the assumption that the combustion takes place in the fine structures where the turbulence kinetic energy dissipates.…”

Critical analysis of classical turbulent combustion experiments on the basis of RANS simulations

“…A simplified version of EPaSR model was also proposed [40]. In order to reduce costs it was proposed to abandon the description of convective and diffusion transport of the fine structures over space.…”

Large eddy simulation of flame structure and combustion mode in a hydrogen fueled supersonic combustor

“…PaSR sub-grid combustion model is adopted in this study to account for the sequentially and simultaneously processes of micromixing and chemical reactions. It is based on the conjecture that any turbulent flow can be divided into fine structures (*) and surroundings (0), interacting through the balance equations [18,21]. Most of dissipation and mixing as well as chemical reactions take place in the fine structures, where reactants are mixed at scales of molecular level.…”