scholarly journals Numerical study of bluff-body non-premixed flame structures using laminar flamelet model

2005 ◽  
Vol 219 (5) ◽  
pp. 361-370 ◽  
Author(s):  
M Hossain ◽  
W Malalasekera
Keyword(s):  
Flow Field ◽  
Bluff Body ◽  
Recirculation Zone ◽  
Numerical Study ◽  
Flame Structure ◽  
Local Extinction ◽  
Flamelet Model ◽  
Neck Zone ◽  
Laminar Flamelet ◽  
Laminar Flamelet Model

A laminar flamelet model is applied for bluff-body stabilized flames to study the flow field, mixing pattern, and the flame structure at two different velocities. The k - ɛ turbulence model is applied for accounting the turbulence fluctuations. It is found that the recirculation zone dominates the near field, while the far field structure is similar to the jet flow. The intermediate neck zone is the intense mixing region. The computation shows that the fuel jet velocity has significant effect on the structure of the flow field, which in turn has significant effect on the combustion characteristics. The laminar flamelet model is found to be adequate for simulating the temperature and the flame composition inside the recirculation zone. The flamelet model has, however, failed to account for the local extinction in the neck zone. Possible limitation of the laminar flamelet model to predict the local extinction is discussed.

scholarly journals Modelling of a bluff body stabilized CH4/H2 flame based on a laminar flamelet model with emphasis on NO prediction

2003 ◽  
Vol 217 (2) ◽  
pp. 201-210 ◽  
Author(s):  
M Hossain ◽  
W Malalasekera
Keyword(s):  
Steady State ◽  
Model Prediction ◽  
Bluff Body ◽  
Lewis Number ◽  
Flamelet Model ◽  
Differential Diffusion ◽  
The University ◽  
Laminar Flamelet ◽  
Laminar Flamelet Model

A laminar flamelet model prediction of a bluff body stabilized CH4/H2 flame is reported. The predicted results of temperature and major and minor species as well as NO are compared against the Raman/Rayleigh/LIF data available from the University of Sydney. The effect of differential diffusion is also studied. The calculation shows that temperature and concentration of major and minor species are better predicted by the unity Lewis number flamelet. It is also shown that the current steady state flamelet approach has difficulties in predicting experimental NO levels.

Numerical study of the flow over the modified simple frigate shape

2020 ◽  
pp. 095441002097775
Author(s):  
Tong Li ◽  
Yibin Wang ◽  
Ning Zhao
Keyword(s):  
Bluff Body ◽  
Recirculation Zone ◽  
Numerical Study ◽  
Reference Value ◽  
Flow Fields ◽  
Navier Stokes ◽  
Detached Eddy Simulation ◽  
Eddy Simulation ◽  
Delayed Detached Eddy Simulation ◽  
Simulation Results

The simple frigate shape (SFS) as defined by The Technical Co-operative Program (TTCP), is a simplified model of the frigate, which helps to investigate the basic flow fields of a frigate. In this paper, the flow fields of the different modified SFS models, consisting of a bluff body superstructure and the deck, were numerically studied. A parametric study was conducted by varying both the superstructure length L and width B to investigate the recirculation zone behind the hangar. The size and the position of the recirculation zones were compared between different models. The numerical simulation results show that the size and the location of the recirculation zone are significantly affected by the superstructure length and width. The results obtained by Reynolds-averaged Navier-Stokes method were also compared well with both the time averaged Improved Delayed Detached-Eddy Simulation results and the experimental data. In addition, by varying the model size and inflow velocity, various flow fields were numerically studied, which indicated that the changing of Reynolds number has tiny effect on the variation of the dimensionless size of the recirculation zone. The results in this study have certain reference value for the design of the frigate superstructure.

scholarly journals Modeling of Spray Combustion with a Steady Laminar Flamelet Model in an Aeroengine Combustion Chamber Based on OpenFOAM

2018 ◽  
Vol 2018 ◽  
pp. 1-13
Author(s):  
Yinli Xiao ◽  
Zupeng Wang ◽  
Zhengxin Lai ◽  
Wenyan Song
Keyword(s):  
Combustion Chamber ◽  
High Performance ◽  
Numerical Models ◽  
Spray Combustion ◽  
Combustion Chambers ◽  
Flamelet Model ◽  
Steady Laminar ◽  
Good Agreement ◽  
Laminar Flamelet ◽  
Laminar Flamelet Model

The development of high-performance aeroengine combustion chambers strongly depends on the accuracy and reliability of efficient numerical models. In the present work, a reacting solver with a steady laminar flamelet model and spray model has been developed in OpenFOAM and the solver details are presented. The solver is firstly validated by Sandia/ETH-Zurich flames. Furthermore, it is used to simulate nonpremixed kerosene/air spray combustion in an aeroengine combustion chamber with the RANS method. A comparison with available experimental data shows good agreement and validates the capability of the new developed solver in OpenFOAM.

Simulations of Unsteady Oscillations in Turbulent Non-Premixed Swirling Flames

2009 ◽  
Author(s):  
Ranga Dinesh ◽  
Karl Jenkins ◽  
Michael Kirkpatrick
Keyword(s):  
Large Scale ◽  
Bluff Body ◽  
Recirculation Zone ◽  
Fuel Mixture ◽  
Quantitative Agreement ◽  
Flamelet Model ◽  
Eddy Viscosity Model ◽  
Instability Modes ◽  
Swirling Flames ◽  
Time Periodicity

Simulations of turbulent non-premixed swirling flames based on the Sydney swirl burner experiments under different flame characteristics are conducted using large eddy simulations (LES). The simulations attempt to capture the unsteady flame oscillations and explore the underlying instability modes responsible for a centre jet precession and the large scale recirculation zone oscillation. The selected flame series known as SMH flames have a fuel mixture of methane-hydrogen (50:50 by volume). The LES program solved the governing equations on a structured Cartesian grid using finite volume method and the subgrid turbulence and combustion models used the localized dynamic form of Smagorinsky eddy viscosity model and the steady laminar flamelet model respectively. The results show that the LES predicts two types of instability modes near fuel jet region and the bluff body stabilized recirculation zone region. The Mode I instability defined as cyclic precession of a centre jet is identified using time periodicity of the centre jet in flames SMH1 and SMH2. The Mode II instability defined as cyclic expansion and collapse of the recirculation zone is identified using time periodicity of the recirculation zone in flame SMH3. The calculated frequency spectrums found reasonably good agreement with the experimental precession frequencies. Overall, the LES yield a good qualitative and quantitative agreement with the experimental observations, although some discrepancies are apparent.

Significant of Isothermal Flow Studies for High Swirling Flow in Unconfined Burner

2015 ◽  
Vol 789-790 ◽  
pp. 477-483
Author(s):  
A.R. Norwazan ◽  
M.N. Mohd Jaafar
Keyword(s):  
Flow Field ◽  
Combustion Chamber ◽  
Turbulent Flows ◽  
Recirculation Zone ◽  
Swirling Flow ◽  
Numerical Study ◽  
Tangential Velocity ◽  
Radial Distance ◽  
Navier Stokes ◽  
Reacting Flow

This paper is presents numerical simulation of isothermal swirling turbulent flows in a combustion chamber of an unconfined burner. Isothermal flows of with three different swirl numbers, SN of axial swirler are considered to demonstrate the effect of flow axial velocity and tangential velocity to define the center recirculation zone. The swirler is used in the burner that significantly influences the flow pattern inside the combustion chamber. The inlet velocity, U0 is 30 m/s entering into the burner through the axial swirler that represents a high Reynolds number, Re to evaluate the differences of SN. The significance of center recirculation zone investigation affected by differences Re also has been carried out in order to define a good mixing of air and fuel. A numerical study of non-reacting flow into the burner region is performed using ANSYS Fluent. The Reynolds–Averaged Navier–Stokes (RANS) realizable k-ε turbulence approach method was applied with the eddy dissipation model. An attention is focused in the flow field behind the axial swirler downstream that determined by transverse flow field at different radial distance. The results of axial and tangential velocity were normalized with the U0. The velocity profiles’ behaviour are obviously changes after existing the swirler up to x/D = 0.3 plane. However, their flow patterns are similar for all SN after x/D = 0.3 plane towards the outlet of a burner.

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