Prediction of CO and NOx Pollutants in a Stratified Bluff Body Burner

Abstract

The major exhaust gas pollutants from heavy duty gas turbine engines are CO and NOx. The difficulty of predicting the concentration of these combustion products originates from their wide range of chemical time scales. In this paper, a combustion model that includes the prediction of the carbon monoxide and nitric oxide emissions is tested. Large eddy simulations (LES) are performed using a compressible code (OpenFOAM). A modified flamelet generated manifolds (FGM) approach is applied with an artificially thickened flame approach (ATF) to resolve the flame on the numerical grid, with a flame sensor to ensure that the flame is only thickened in the flame region. For the prediction of the CO and NOx emissions, pollutant species transport equations and a second, CO based, progress variable are introduced for the flame burnout zone to account for slow chemistry effects. For the validation of the models, the Cambridge burner of Sweeney et al. (2012, “The Structure of Turbulent Stratified and Premixed Methane/Air Flames—I: Non-Swirling Flows,” Combust. Flame, 159, pp. 2896–2911; 2012, “The Structure of Turbulent Stratified and Premixed Methane/Air Flames—II: Swirling Flows,” Combust. Flame, 159, pp. 2912–2929.) is employed, as both carbon monoxide and nitric oxide [Apeloig et al. (2016, “PLIF Measurements of Nitric Oxide and Hydroxyl Radicals Distributions in Swirl Stratified Premixed Flames,” 18th International Symposium on the Application of Laser and Imaging Techniques to Fluid Mechanics, Lisbon, Portugal, July 4–7.)] data are available.

Assessment of Thickened Flame Model Coupled With Flamelet Generated Manifold on a Low-Swirl Partially Premixed Gaseous Lifted Flame

“…The difference between the two approaches stands in how the turbulence effects are taken into account (i.e., β -PDF vs. artificial thickening and wrinkling efficiency function). Although this approach is limited with respect to a standard TF approach with detailed chemistry, some works in the literature have shown its good capability in comparison with more detailed approaches for practical applications [41,42].…”

Reduced Methane Combustion Mechanism and Verification, Validation, and Accreditation (VV&A) in CFD for NO Emission Prediction

“…The results showed good agreement with the experimental data, but the temperature was higher than experiments, which resulted higher NO prediction value. Gruhlke et al [10] used Flamelet Generated Manifold (FGM) model to predict CO and NO x emissions. The results showed that major species can be predicted well by LES and FGM models, and the CO emissions showed good agreement with measurements.…”

A simple post-processing method to correct species predictions in artificially thickened turbulent flames

“…To account for the complex chemical pathways involved, LES has been combined with various chemistry modelling strategies. Despite of recent impressive demonstrations [2][3][4][5] , the prediction of pollutant formations, especially of CO, remains a major challenge for combustion LES.…”