Conditional scalar dissipation rate modeling for turbulent spray flames using artificial neural networks

2020 ◽  
Author(s):  
S. Yao ◽  
B. Wang ◽  
A. Kronenburg ◽  
O.T. Stein
Keyword(s):  
Neural Networks ◽  
Artificial Neural Networks ◽  
Dissipation Rate ◽  
Scalar Dissipation ◽  
Scalar Dissipation Rate ◽  
Spray Flames ◽  
Artificial Neural ◽  
Turbulent Spray

Derivation and Evaluation of a Multi-regime Spray Flamelet Model

2015 ◽  
Vol 229 (4) ◽  
Author(s):  
Hernan Olguin ◽  
Eva Gutheil
Keyword(s):  
Dissipation Rate ◽  
Mixture Fraction ◽  
Lewis Number ◽  
Scalar Dissipation ◽  
Scalar Dissipation Rate ◽  
Flamelet Model ◽  
Spray Flames ◽  
Special Cases ◽  
Turbulent Spray ◽  
Combustion Regimes

AbstractThe formulation of a comprehensive flamelet model to consider detailed chemical reaction mechanisms in the simulation of turbulent spray flames is a very challenging task due to the inherent multi-regime structure of spray flames. Non-premixed, premixed, and evaporation-controlled combustion regimes may be found in a single spray flame. Recently, attempts have been made to extend classical single regime flamelet models to more complex situations, where at least two combustion regimes coexist. The objective of this work is to develop a framework in which two-regime flamelet models can be described and combined in order to advance the development of a comprehensive flamelet model for turbulent spray flames. For this purpose, a set of spray flamelet equations in terms of the mixture fraction and a reaction progress variable is derived, which includes the evaporation, characterizing the spray flames, and which describes all combustion regimes appearing in spray flames. The two-regime and single regime flamelet equations available in the literature are retrieved from these multi-dimensional spray flamelet equations as special cases. The derived set of spray flamelet equations is then used to evaluate structures of laminar ethanol/air spray flames in the counterflow configuration in order to determine the significance of different combustion regimes. The present study concerns spray flames with no pre-vaporized liquid in the oxidizing gas phase, and it is found that only non-premixed and evaporation-controlled combustion regimes exist, so that premixed effects may be neglected. Moreover, an exact transport equation for the scalar dissipation rate is derived, which explicitly takes spray evaporation and detailed transport into account. This equation is then used to evaluate assumptions commonly adopted in the literature. The results show that the spatial variation of the mean molecular weight of the mixture may be neglected in the formulation of the mixture fraction, but it may be significant for its scalar dissipation rate. The assumption of unity Lewis number may lead to non-physical values of the scalar dissipation rate of the mixture fraction, whereas the use of a mass-averaged diffusion coefficient of the mixture is a good approximation for the spray flames under investigation.

Numerical and Theoretical Analysis of Laminar Counterflowing Spray Flames for Use in Turbulent Combustion Modeling

2014 ◽  
Author(s):  
Hernan Olguin ◽  
Philip Hindenberg ◽  
Eva Gutheil
Keyword(s):  
Numerical Simulations ◽  
Dissipation Rate ◽  
Numerical Study ◽  
Mixture Fraction ◽  
Flame Structure ◽  
Main Reaction ◽  
Computational Time ◽  
Scalar Dissipation ◽  
Scalar Dissipation Rate ◽  
Spray Flames

The paper presents a combined theoretical and numerical study of laminar counterflow mono-disperse spray flames. The numerical model includes a similarity transformation of the two-dimensional governing gas phase equations into a one-dimensional formulation. The reduced computational time enables the use of detailed chemical reaction mechanisms to study the spray flame structure. In particular, the effect of spray evaporation on combustion is investigated by means of numerical simulations. For this purpose, the transport equation of the scalar dissipation rate of the mixture fraction is derived, where the spray evaporation source term is included. Numerical simulations of laminar liquid and gaseous ethanol and combustion products mono disperse spray flames under fuel-rich conditions are presented and discussed. The parametric dependence of the flame structures on strain rate is studied with emphasis on the spray evaporation. Droplet reversal and oscillation are found to dominate the flame structure, and they determine the location of the main reaction zone as well as the profile of the scalar dissipation rate. The study aims to develop a novel spray flamelet model for use in the numerical simulations of turbulent spray combustion with particular emphasis on flameless conditions.

FUTURE OF ARTIFICIAL NEURAL NETWORKS IN SPACE EXPLORATION AND SPACE ENGINEERING

2018 ◽  
pp. 6-11
Author(s):  
Kobiljon Kh. Zoidov ◽  
◽  
Svetlana V. Ponomareva ◽  
Daniel I. Serebryansky ◽  
◽  
...  
Keyword(s):  
Neural Networks ◽  
Artificial Neural Networks ◽  
Space Exploration ◽  
Artificial Neural
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