Multi-Environment Probability Density Function Method for Modeling Turbulent Combustion in Industrial Equipment

2009 ◽  
Author(s):  
M. Denison ◽  
S. Borodai ◽  
R. Fox ◽  
M. Bockelie
Keyword(s):  
Probability Density Function ◽  
Probability Density ◽  
Density Function ◽  
Turbulent Combustion ◽  
Chemical Engineering ◽  
Fluid Dynamic ◽  
Chemical Processes ◽  
Cfd Modeling ◽  
Computational Time ◽  
Detailed Chemistry

In this paper is described a computational fluid dynamic (CFD) modeling tool based on the Multi-Environment Probability Density Function (MEPDF) method developed specifically to account for finite rate chemistry effects in modeling practical combustion systems. MEPDF originated from multi-environment micro-mixing models used in the chemical engineering community to simulate chemical processes with little or no heat release. Previous uses of MEPDF for combustion applications typically used simple chemistry models. Our work has focused on extending the MEPDF method for combustion applications using detailed chemistry models. Provided below is an overview of the MEPDF formulation and example calculations. The model has been shown to use substantially less computational time compared to more traditional PDF methods using a Monte-Carlo approach.

scholarly journals Conceptual Limitations of the Probability Density Function Method for Modeling Turbulent Premixed Combustion and Closed-Form Description of Chemical Reactions’ Effects

Fluids ◽  
2021 ◽  
Vol 6 (4) ◽  
pp. 142
Author(s):  
Vladimir Zimont
Keyword(s):  
Probability Density Function ◽  
Closed Form ◽  
Probability Density ◽  
Density Function ◽  
Inverse Modeling ◽  
Turbulent Combustion ◽  
Laminar Flame ◽  
Chemical Effects ◽  
Instantaneous Combustion ◽  
Modeling Strategy

In this paper, we critically analyzed possibilities of probability density function (PDF) methods for the closed-form description of combustion chemical effects in turbulent premixed flames. We came to the conclusion that the concept of a closed-form description of chemical effects in the classical modeling strategy in the PDF method based on the use of reaction-independent mixing models is not applicable to turbulent flames. The reason for this is the strong dependence of mixing on the combustion reactions due to the thin-reaction-zone nature of turbulent combustion confirmed in recent optical studies and direct numerical simulations. In this case, the chemical effect is caused by coupled reaction–diffusion processes that take place in thin zones of instantaneous combustion. We considered possible alternative modeling strategies in the PDF method that would allow the chemical effects to be described in a closed form and came to the conclusion that this is possible only in a hypothetical case where instantaneous combustion occurs in reaction zones identical to the reaction zone of the undisturbed laminar flame. For turbulent combustion in the laminar flamelet regime, we use an inverse modeling strategy where the model PDF directly contains the characteristics of the laminar flame. For turbulent combustion in the distributed preheat zone regime, we offer an original joint direct/inverse modeling strategy. For turbulent combustion in the thickened flamelet regime, we combine the joint direct/inverse and inverse modeling strategies correspondingly for simulation of the thickened flamelet structure and for the determination of the global characteristics of the turbulent flame.

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