scholarly journals Analysis and flamelet modelling for spray combustion

2008 ◽  
Vol 612 ◽  
pp. 45-79 ◽  
Author(s):  
YUYA BABA ◽  
RYOICHI KUROSE
Keyword(s):  
Conservation Equation ◽  
Spray Combustion ◽  
Combustion Model ◽  
Flamelet Model ◽  
Jet Flame ◽  
Total Enthalpy ◽  
Progress Variable ◽  
Combustion Models ◽  
Spray Flame ◽  
Variable Approach

The validity of a steady-flamelet model and a flamelet/progress-variable approach for gaseous and spray combustion is investigated by a two-dimensional direct numerical simulation (DNS) of gaseous and spray jet flames, and the combustion characteristics are analysed. A modified flamelet/progress-variable approach, in which total enthalpy rather than product mass fraction is chosen as a progress variable, is also examined. DNS with an Arrhenius formation, in which the chemical reaction is directly solved in the physical flow field, is performed as a reference to validate the combustion models. The results show that the diffusion flame is dominant in the gaseous diffusion jet flame, whereas diffusion and premixed flames coexist in the spray jet flame. The characteristics of the spray flame change from premixed–diffusion coexistent to diffusion-dominant downstream. Comparisons among the results from DNS with various combustion models show the modified flamelet/progress-variable approach to be superior to the other combustion models, particularly for the spray flame. Where the behaviour of the gaseous total enthalpy is strongly affected by the energy transfer (i.e. heat transfer and mass transfer) from the dispersed droplet, and this effect can be accounted for only by solving the conservation equation of the total enthalpy. However, even the DNS with the modified flamelet/progress-variable approach tends to underestimate the gaseous temperature in the central region of the spray jet flame. To increase the prediction accuracy, a combustion model for the partially premixed flame for the spray flame is necessary.

scholarly journals Numerical Investigation of an OxyfuelNon-Premixed CombustionUsing a Hybrid Eulerian Stochastic Field/Flamelet Progress Variable Approach: Effects of H2/CO2Enrichment and Reynolds Number

Energies ◽  
2018 ◽  
Vol 11 (11) ◽  
pp. 3158 ◽  
Author(s):  
Rihab Mahmoud ◽  
Mehdi Jangi ◽  
Benoit Fiorina ◽  
Michael Pfitzner ◽  
Amsini Sadiki
Keyword(s):  
Probability Density Function ◽  
Probability Density ◽  
Density Function ◽  
Combustion Model ◽  
Stochastic Field ◽  
Suggested Approach ◽  
Jet Flame ◽  
Progress Variable ◽  
Variable Approach ◽  
Novel Approach

In the present paper, the behaviour of an oxy-fuel non-premixed jet flame is numerically investigated by using a novel approach which combines a transported joint scalar probability density function (T-PDF) following the Eulerian Stochastic Field methodology (ESF) and a Flamelet Progress Variable (FPV) turbulent combustion model under consideration of detailed chemical reaction mechanism. This hybrid ESF/FPV approach overcomes the limitations of the presumed- probability density function (P-PDF) based FPV modelling along with the solving of associated additional modelled transport equations while rendering the T-PDF computationally less demanding. In Reynolds Averaged Navier-Stokes (RANS) context, the suggested approach is first validated by assessing its general prediction capability in reproducing the flame and flow properties of a simple piloted jet flame configuration known as Sandia Flame D. Second, its feasibility in capturing CO2addition effect on the flame behaviour is demonstrated while studying a non-premixed oxy-flame configuration. This consists of an oxy-methane flame characterized by a high CO2 amount in the oxidizer and a significant content of H2 in the fuel stream, making it challenging for combustion modelling. Comparisons of numerical results with experimental data show that the complete model reproduces the major properties of the flame cases investigated and allows achieving the best agreement for the temperature and different species mass fractions once compared to the classical presumed PDF approach.

scholarly journals Application of flamelet/progress-variable approach to the large eddy simulation of a turbulent jet flame of pulverized coals

2020 ◽  
Vol 31 (10) ◽  
pp. 4253-4274
Author(s):  
Shota Akaotsu ◽  
Yohsuke Matsushita ◽  
Hideyuki Aoki ◽  
Weeratunge Malalasekera
Keyword(s):  
Large Eddy Simulation ◽  
Turbulent Jet ◽  
Jet Flame ◽  
Progress Variable ◽  
Eddy Simulation ◽  
Variable Approach ◽  
Large Eddy

DNS AND LES OF SOOT FORMATION IN OXY-FUEL SPRAY FLAME: APPLICATION OF A NON-ADIABATIC FLAMELET/PROGRESS-VARIABLE APPROACH

2018 ◽  
Author(s):  
Reo Kai ◽  
Akihiro Kishimoto ◽  
Kenichiro Takenaka ◽  
Masaya Muto ◽  
Ryoichi Kurose
Keyword(s):  
Soot Formation ◽  
Fuel Spray ◽  
Progress Variable ◽  
Spray Flame ◽  
Variable Approach

Numerical Simulation of a Reacting Jet in a Vitiated Cross Flow Using a Novel Progress Variable Approach

2017 ◽  
Author(s):  
Rohit Kulkarni ◽  
John P. Wood ◽  
Mario Zuber ◽  
Hasan U. Karim
Keyword(s):  
Flame Propagation ◽  
Gas Turbines ◽  
Accurate Determination ◽  
Cross Flow ◽  
Combustion Products ◽  
Combustion Model ◽  
Progress Variable ◽  
Variable Approach ◽  
Auto Ignition ◽  
Lifted Flames

Staged/sequential combustion is a state of the art method to provide operational flexibility and reduced emissions in gas turbines. To use Computational Fluid Dynamics (CFD) to study such systems a reliable and computationally inexpensive turbulent combustion model is necessary. A key requisite for such a model is the accurate determination of the flame location in order to predict emissions, flame dynamics, and temperature distribution. Previously a model was developed for reheat combustion, based on a progress-variable method using auto-ignition reactors. However, sequential combustion systems are now being implemented where both auto-ignition and flame propagation are important. Consequently, the reheat model has been extended to consider flame propagation in mixtures that do not auto-ignite. This has been achieved by incorporating a small proportion of combustion products in the reactant mixture considered by the reactor. This approach has broadened the model’s applicability to address the full space between auto-ignition and flame propagation regimes. The revised model has been validated by comparison with reacting jet in vitiated cross-flow experiments demonstrating a significantly better prediction of the position of both attached and lifted flames than the original model.

scholarly journals Large Eddy Simulation of Autoignition in a Turbulent Hydrogen Jet Flame Using a Progress Variable Approach

2012 ◽  
Vol 2012 ◽  
pp. 1-11 ◽  
Author(s):  
Rohit Kulkarni ◽  
Wolfgang Polifke
Keyword(s):  
Large Eddy Simulation ◽  
Mixture Fraction ◽  
Chemical Mechanism ◽  
Model Parameters ◽  
Jet Flame ◽  
Progress Variable ◽  
Eddy Simulation ◽  
Variable Approach ◽  
Tabulated Chemistry ◽  
Large Eddy

The potential of a progress variable formulation for predicting autoignition and subsequent kernel development in a nonpremixed jet flame is explored in the LES (Large Eddy Simulation) context. The chemistry is tabulated as a function of mixture fraction and a composite progress variable, which is defined as a combination of an intermediate and a product species. Transport equations are solved for mixture fraction and progress variable. The filtered mean source term for the progress variable is closed using a probability density function of presumed shape for the mixture fraction. Subgrid fluctuations of the progress variable conditioned on the mixture fraction are neglected. A diluted hydrogen jet issuing into a turbulent coflow of preheated air is chosen as a test case. The model predicts ignition lengths and subsequent kernel growth in good agreement with experiment without any adjustment of model parameters. The autoignition length predicted by the model depends noticeably on the chemical mechanism which the tabulated chemistry is based on. Compared to models using detailed chemistry, significant reduction in computational costs can be realized with the progress variable formulation.

scholarly journals A combustion model sensitivity study for CH4/H2 bluff-body stabilized flame

2007 ◽  
Vol 221 (11) ◽  
pp. 1377-1390 ◽  
Author(s):  
M Hossain ◽  
W Malalasekera
Keyword(s):  
Bluff Body ◽  
Mixture Fraction ◽  
Sensitivity Study ◽  
Combustion Model ◽  
Flamelet Model ◽  
Combustion Models ◽  
Mass Fractions ◽  
Experimental Values ◽  
Constituent Mass ◽  
Laminar Flamelet

The objective of the current work is to assess the performance of different combustion models in predicting turbulent non-premixed combustion in conjunction with the k-∊ turbulence model. The laminar flamelet, equilibrium chemistry, constrained equilibrium chemistry, and flame sheet models are applied to simulate combustion in a CH4/H2 bluff-body flame experimentally studied by the University of Sydney. The computational results are compared to experimental values of mixture fraction, temperature, and constituent mass fractions. The comparison shows that the laminar flamelet model performs better than other combustion models and mimics most of the significant features of the bluff-body flame.

A Comparative Study of Combustion Models for Spark Ignition Engines Based on Experimentation and CFD Simulation

2010 ◽  
Author(s):  
Raouf Mobasheri ◽  
M. Sadegh Shahrokhi-Dehkordi
Keyword(s):  
Comparative Study ◽  
Cfd Simulation ◽  
Combustion Process ◽  
Experimental Tests ◽  
Experimental Results ◽  
Nox Emission ◽  
Combustion Model ◽  
Spark Ignition Engines ◽  
Flamelet Model ◽  
Combustion Models

Computational fluid dynamics (CFD) is able to significantly reduce the number of experimental tests and measurements and lower the development time and costs. However some parameters which are needed for CFD calculation must be achieved experimentally. In this paper, a comparative study was carried out to clarify the effect of three different combustion models on the prediction capability of combustion process and NOx emission on a modified 4-cylinder MPFI SI engine. Validation of the combustion model has been performed through comparing simulation data with the experimental results and a satisfactory agreement between them has been achieved in terms of combustion parameters and NOx emission. The results show that, applying appropriate constants of each combustion model including Eddy break up model (Ebu), Probability density function (Pdf) and Coherent flamelet model (Cfm) causes the computational results to be in agreement with experimental results. Furthermore the results show that the nearest prediction in comparison with experimental results is by applying the Ebu model.

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