Towards Modeling Lean Blow Out in Gas Turbine Flameholder Applications

2004 ◽  
Author(s):  
Won-Wook Kim ◽  
Jeffrey J. Lienau ◽  
Paul R. Van Slooten ◽  
Meredith B. Colket ◽  
Robert E. Malecki ◽  
...  
Keyword(s):  
Equivalence Ratio ◽  
Bluff Body ◽  
Recirculation Zone ◽  
Reacting Flows ◽  
Experimental Measurements ◽  
Turbulent Reacting Flows ◽  
Zone Length ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Lean Limit

The objective of this study was to assess the accuracy of the Large-Eddy Simulation (LES) methodology, with a simple combustion closure based on equilibrium chemistry, for simulating turbulent reacting flows behind a bluff body flameholder. Specifically, the variation in recirculation zone length with change in equivalence ratio was calculated and compared to experimental measurements. It was found that the present LES modeling approach can reproduce this variation accurately. However, it understated the recirculation zone length at the stoichiometric condition. The approach was assessed at the lean blow out (LBO) condition to evaluate its behavior at the lean limit and to analyze the physics of combustion instability.

Towards Modeling Lean Blow Out in Gas Turbine Flameholder Applications

2004 ◽  
Vol 128 (1) ◽  
pp. 40-48 ◽  
Author(s):  
Won-Wook Kim ◽  
Jeffrey J. Lienau ◽  
Paul R. Van Slooten ◽  
Meredith B. Colket ◽  
Robert E. Malecki ◽  
...  
Keyword(s):  
Equivalence Ratio ◽  
Bluff Body ◽  
Recirculation Zone ◽  
Reacting Flows ◽  
Experimental Measurements ◽  
Turbulent Reacting Flows ◽  
Zone Length ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Lean Limit

The objective of this study was to assess the accuracy of the large-eddy simulation (LES) methodology, with a simple combustion closure based on equilibrium chemistry, for simulating turbulent reacting flows behind a bluff body flameholder. Specifically, the variation in recirculation zone length with change in equivalence ratio was calculated and compared to experimental measurements. It was found that the present LES modeling approach can reproduce this variation accurately. However, it understated the recirculation zone length at the stoichiometric condition. The approach was assessed at the lean blow out condition to evaluate its behavior at the lean limit and to analyze the physics of combustion instability.

scholarly journals A scaling law for the recirculation zone length behind a bluff body in reacting flows

2019 ◽  
Vol 875 ◽  
pp. 699-724 ◽  
Author(s):  
James C. Massey ◽  
Ivan Langella ◽  
Nedunchezhian Swaminathan
Keyword(s):  
Heat Release ◽  
Turbulence Intensity ◽  
Bluff Body ◽  
Recirculation Zone ◽  
Scaling Law ◽  
Reacting Flows ◽  
The Body ◽  
Turbulent Shear ◽  
Zone Length ◽  
Isothermal Flows

The recirculation zone length behind a bluff body is influenced by the turbulence intensity at the base of the body in isothermal flows and also the heat release and its interaction with turbulence in reacting flows. This relationship is observed to be nonlinear and is controlled by the balance of forces acting on the recirculation zone, which arise from the pressure and turbulence fields. The pressure force is directly influenced by the volumetric expansion resulting from the heat release, whereas the change in the turbulent shear force depends on the nonlinear interaction between turbulence and combustion. This behaviour is elucidated through a control volume analysis. A scaling relation for the recirculation zone length is deduced to relate the turbulence intensity and the amount of heat release. This relation is verified using the large eddy simulation data from 20 computations of isothermal flows and premixed flames that are stabilised behind the bluff body. The application of this scaling to flames in an open environment and behind a backward facing step is also explored. The observations and results are explained on a physical basis.

Local Entropy Generation in Large Eddy Simulation of Turbulent Reacting Flows

2017 ◽  
Author(s):  
Mehdi Safari
Keyword(s):  
Large Eddy Simulation ◽  
Entropy Generation ◽  
Reacting Flows ◽  
Chemical Mechanism ◽  
Turbulent Reacting Flows ◽  
Local Entropy ◽  
Source Terms ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Local Entropy Generation

Analysis of local entropy generation is an effective means to investigate sources of efficiency loss in turbulent combustion from the standpoint of the second law of thermodynamics. A methodology, termed the entropy filtered density function (En-FDF), is developed for large eddy simulation (LES) of turbulent reacting flows to include the transport of entropy, which embodies the complete statistical information about entropy variations within the subgrid scale. The modeled En-FDF contains a stochastic differential equation (SDE) for entropy which is solved by a Lagrangian Monte Carlo method. In this study, a numerical study has been done on effectiveness of SDE to model entropy variation using a partially stirred reactor (PaSR). This provides a computationally affordable case to compare different effects of entropy generation source terms and fine tune mixing coefficients. In this equation, turbulent mixing is modeled with Interaction by Exchange with the Mean (IEM). Combustion source terms are provided by direct integration of a GRI3.0 mechanism for methane/air system. Evolution of entropy was calculated from stochastic model and then compared with the one obtained directly by integrating the chemical mechanism. It was shown that results of both calculations have very good agreement versus different mixture fractions.

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