Flamelet Generated Manifold (FGM) has proven to be an efficient approach to model turbulent combustion across different regimes of combustion. The manifolds are generally created by solving adiabatic laminar premixed or opposed flow configurations. Gas turbine combustors often involves many strong non-adiabatic events like multiple temperature boundaries, quenching from cooling and effusion holes, conjugate heat transfer, soot radiation interaction, phase change from spray and the modulation of inlet conditions. The adiabatic assumption of the underlying flamelet generation in the FGM is, therefore, can lead to errors in prediction of flame speed, liner temperatures, and pollutant formation.

In this work, a novel approach to generate fully non-adiabatic manifold is proposed and validated. The FGM manifold is created using a series of  non-adiabatic flamelets, solved in one-dimensional physical space. In order to account for large range of heat loss and gain to the flamelets, an optimal and automated strategy is chosen the generate the non-adiabatic flamelets with a wide spectrum of heat gain and loss. The fully non-adiabatic flamelets are then convoluted to generate five-dimensional Non-adiabatic Flamelet Generated Manifold (NFGM)  PDF for average properties to couple to the CFD solution. The nonadiabatic flamelets and corresponding NFGM is implemented into ANSYS Fluent software. The approach is first validated for canonical cases like Sandia Flame D and Cabra Ch4-air flame. Then the NFGM model is used to model a temperature-sensitive swirl stabilized methane fueled turbulent flame, developed at DLR Stuttgart as the PRECCINSTA combustor. The experimental data for this combustor is available for multiple operating conditions. A stable operating point (φ=0.83, P=30 kW) is chosen. The proposed nonadiabatic NFGM is used with Stress blended eddy simulation (SBES). The current NFGM-SBES results are compared with experimental data as well as the previous published works. The impact of modeling heat release in flamelet is used to analyze the M-shape versus V-shape flame transition and the peaks of the carbon monoxide in shear layers. Differences in predictions of mean and variance of reaction progress and mixture fraction in the core versus the near-wall region are analyzed and quantified. The findings from the current work, in terms of accuracy, validity and best practices when modeling  NFGM-SBES are discussed and summarized. The improved results of NFGM compared to adiabatic FGM are encouraging and provides a potential high-fidelity tool for accurate, yet efficient modeling of turbulent combustion inside gas turbines


A Fully Non-Adiabatic Flamelet Generated Manifold Model for High Fidelity Modeling of Turbulent Combustion in Gas Turbine Like Conditions

Division / Sponsor:
International Gas Turbine Institute (IGTI)

Paper Proceedings: https://asmedigitalcollection.asme.org/GT/GT2020/volume/84058

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