Laminar flamelet model prediction of NO_x formation in a turbulent bluff-body combustor

Abstract

A bluff-body combustor, with recirculation zone and simple boundary conditions, is ideal as a compromise for an industrial combustor for validating combustion models. This combustor, however, has proved to be very challenging to the combustion modellers in a number of previous studies. In the present study, an improved prediction has been reported through better representation of turbulence effect by Reynolds stress transport model and extended upstream computational domain. Thermo-chemical properties of the flame have been represented by a laminar flamelet model. A comparison among reduced chemical kinetic mechanism of Peters and detailed mechanisms of GRI 2.11, GRI 3.0, and San Diego has been studied under the laminar flamelet modelling framework. Computed results have been compared against the well-known experimental data of Sydney University bluff-body CH 4 /H 2 flame. Results show that the laminar flamelet model yields very good agreement with measurements for temperature and major species with all the reaction mechanisms. The GRI 2.11 performs better than the other reaction mechanisms in predicting minor species such as OH and pollutant NO. The agreement achieved for NO is particularly encouraging considering the simplified modelling formulation utilized for the kinetically controlled NO formation.

Effects of hydrogen addition on the structure and pollutant emissions of a turbulent unconfined swirling flame

“…Fine-tuning of the standard k-ε model constants can also be found in [6][7][8] in conjunction with EDC combustion model, where acceptable accuracy is reported. When used with laminar flamelet model, both the fine-tuned k-ε model and the RSM yielded acceptable results as reported in [10] and [11] respectively. Yilmaz et al [9] compared the fine-tuned k-ε model with large eddy simulation (LES) with two subgrid models; the Smagorinsky-Lilly and RNG/k-ε models.…”

“…The steady laminar flamelet model is known to perform better in terms of prediction of minor species. Several researchers [9][10][11] have used such model to simulate similar flames of CH 4 /H 2 . Yilmaz et al [9] calculated the Probability Density Function (PDF) for temperature, mixture fraction and major and minor species mass fractions and compared the flamelet model with equilibrium model, showing that flamelet model yields better results within the reaction zone.…”

“…Frassoldati et al [8] developed and implemented a new mechanism with 48 species and 600 reactions involved. Ravikanti et al [11] used GRI2.11 and Mardani et al [7] compared this mechanism with a reduced DRM-22 mechanism and found that the results yielded by the two mechanisms differ as slightly as 1%.…”

“…Lack of such accurate estimation of radiative heat transfer may lead to considerable errors in prediction of flame structure or pollution modeling. Specially in terms of NO which is very sensitive to temperature non-inclusion of radiative heat loss will lead to over prediction of this species [11]. For prediction of radiation, P1 model is widely used in similar simulations with no significant error [6,[42][43][44] and by considering reasonable computational cost, this model is chosen for this study.…”

Combustion of Biogas Released from Palm Oil Mill Effluent and the Effects of Hydrogen Enrichment on the Characteristics of the Biogas Flame

“…Similar flame was simulated with the eddy dissipation concept (EDC) by Frassoldati et al [24] and Mardani and Tabejamaat [25] and an unacceptable accuracy was found for mass fraction of minor species like O and OH which conducts to wrong expectation for NO formation behavior. It was found that, for modelling the combustion of hydrogen-enriched methane, the steady laminar flamelet method has better performance in terms of minor species prediction [26]. Probability density function (PDF) was calculated for mass fraction of minor and major species, mixture fraction, and temperature by Suo [27].…”