Subgrid Scale Combustion Modeling Based on Stochastic Model Parameterization

Calhoon, William H.; Zambon, A.; Sekar, Balu; Kiel, Barry

doi:10.1115/1.4004254

Cited by 7 publications

(11 citation statements)

References 14 publications

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“…As mentioned earlier, this sub-model couples the LEM with a 1-D counter flow solver so that turbulent counter flow and stagnation point flow simulations may be carried out [12] [13]. One innovative feature of this formulation is that it allows for the direct prediction of the turbulent flame extinction limits resulting from imposed large scale strain rate [12]. For nonpremixed and partially premixed flames, the counter flow configuration is adopted [12].…”

Section: IIImentioning

confidence: 99%

“…One innovative feature of this formulation is that it allows for the direct prediction of the turbulent flame extinction limits resulting from imposed large scale strain rate [12]. For nonpremixed and partially premixed flames, the counter flow configuration is adopted [12]. In this configuration, a fuel jet exhausts toward an opposing oxidizer jet forming a central stagnation plane.…”

Section: IIImentioning

confidence: 99%

“…For the LEM-CF sub-model, the mean mixture fraction is a monotonic function of the axial coordinate x so that these properties are mapped from x space to <Z> space directly for each simulation. Mapping flame statistics to the mixture fraction variance coordinate is accomplished by running a series of LEM-CF simulations that vary the LEM integral scale L. As discussed earlier, the jet separation distance X L within the LEM-CF counter flow configuration is determined as described by Calhoon, et al [12]. When the length scale L is taken as X L = L, the model produces the maximum realizable values of V Z .…”

Section: Vmentioning

confidence: 99%

“…With these inputs, the jet velocities and the jet separation distance (X L ) are determined as discussed by Calhoon, et al [12]. The bulk strain rate a B is defined by, fuel oxi B L uu a X   (4) where u fuel and u oxi are the fuel and oxidizer jet exit velocities, respectively.…”

Section: IIImentioning

confidence: 99%

“…In this configuration, a fuel jet exhausts toward an opposing oxidizer jet forming a central stagnation plane. Boundary conditions for these jets are imposed such that the mean location of the stagnation plane is centered between the jet exits [12]. Flames initialized within this configuration establish themselves in the vicinity of the stagnation plane with a location dependent on the stoichiometry of the problem.…”

Section: IIImentioning

confidence: 99%

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Strain Effects in Partially Premixed Methane-air Jet Flames

Calhoon

Kemenov

2015

53rd AIAA Aerospace Sciences Meeting

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A large-eddy simulation (LES) subgrid combustion model has been developed based on an innovative application of the linear-eddy model to the counter flow configuration (LEM-CF). This subgrid model is developed by parameterizing flame statistics from the LEM-CF sub-model in terms of a reduced set of variables. A database of closure statistics for LES transport equations for these variables is then generated. The run-time application of the model within LES retrieves the closure statistics from the database resulting in a computationally efficient formulation. One key feature of this formulation is that it includes the LEM-CF prediction of turbulent flame extinction limits to develop a localized extinction criterion for the LES. This extinction criterion is a function of the LES resolved scale strain rate which may be directly computed from the LES resolved scale velocity field. The model's capabilities for capturing strain rate and local extinction effects were assessed through its application to the Sandia piloted partially premixed CH 4 /air-air jet flame series. A comparison of model predictions for scalar means and RMS fluctuations for Flame D and F of this series showed good overall agreement with the experimental data. This included good predictions of the temperature and product species in the neck region of Flame F which is dominated by local extinction effects. The model was also applied to determine the blow-out jet bulk velocity for this configuration which was found to be in reasonable agreement with what is available from the experiment. Through this blow-out assessment, three flame modes for this configuration are also identified beyond the Flame F condition. The flame dynamics of a highly oscillating flame mode just prior to blow-out were also investigated. I. IntroductionFluid dynamic strain effects in nonpremixed, partially premixed, and premixed flows play an important role in the evolutionary development and stabilization of flame structure in both commercial and military gas turbine systems. For commercial combustors, the operation at lean conditions for the sake of efficiency and pollutant suppression results in an enhanced susceptibility of the flame to strain rate effects that may lead to local extinction, instability and blow-off. For military systems, the high strain rate environment within high performance gas turbine augmentors results in difficultly in establishing flame stability over the entire flight envelop. For these extreme conditions, experimental correlations are inadequate at establishing the operational limits of these systems. As a result, many gas turbine manufacturers are turning to computational techniques such as large eddy simulation (LES) to assess sub-system performance and to aid in hardware design and modification. However, this approach is limited by the accuracy of sub-models for turbulence-chemistry interactions that are employed. These sub-models play a critical role in establishing the accuracy of the prediction of turbulent extinction limits that affect flame s...

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