Reacting Turbulent Flow and Thermal Field in a Channel With Inclined Bluff Body Flame Holders

2010 ◽  
Vol 132 (9) ◽  
Author(s):  
Cheng-Xian Lin ◽  
Richard Jack Holder
Keyword(s):  
Turbulent Flow ◽  
Bluff Body ◽  
Numerical Study ◽  
Angle Of Attack ◽  
Turbulent Intensity ◽  
Recirculation Flow ◽  
Flame Holder ◽  
Thermal Fields ◽  
Dissipation Model ◽  
Chemically Reacting

In this paper, a numerical study has been carried out to investigate the effects of inlet turbulent intensity and angle of attack on the chemically reacting turbulent flow and thermal fields in a channel with an inclined bluff body V-gutter flame holder. With a basic geometry used in a previous experimental study, the inlet turbulent intensity was varied from 2% to 100%, while the angle of attack of the V-gutter was varied from 0 deg to 30 deg. The turbulent flow was modeled with a realizable k-ε two-equation turbulence model. The chemical reaction was premixed propane-air combustion with an equivalence ratio of 0.6. The chemistry-turbulence interaction was simulated with an eddy-dissipation model. Numerical results indicated that increasing the inlet turbulent intensity and V-gutter angle of attack resulted in an increase not only in the size, but also in the magnitude of the downstream high turbulence areas with shedding vortexes. The recirculation flow behind the flame holder tended to maintain the rear wall at constant temperature, except at the edges of the wall. The friction factor of the flow channel was more sensitive to the change in inlet turbulence intensity at smaller angle of attack of the V-gutter.

Numerical Simulation of Reactive Turbulent Flows Over Bluff Body Flame Holders: A Parametric Study

2008 ◽  
Author(s):  
Richard Holder ◽  
Cheng-Xian Lin
Keyword(s):  
Turbulent Flows ◽  
Parametric Study ◽  
Bluff Body ◽  
Angle Of Attack ◽  
Turbulent Intensity ◽  
Model Calculations ◽  
Flame Holder ◽  
Dissipation Model ◽  
Numerical Parametric Study ◽  
Combustion Turbulence

In this paper, a numerical parametric study has been conducted to examine the effects of varying both inlet turbulent intensity and angle of attack for a bluff body flame holder (V-gutter) in a channel. The geometry used was based on previous experiments. The inlet turbulent intensity was varied from 2% to 100% while the angle of attack of the V-gutter was varied from −20° to 20°. The turbulent flow was modeled with a RANS-based realizable k-ε turbulence model. The combustion setup used was premixed propane-air combustion with an equivalence ratio of 0.6. The combustion-turbulence interaction is simulated with an eddy-dissipation model. Calculations were carried out using a finite volume based solver, and all equations were solved using the second order upwind method. Results indicate that increasing the inlet turbulent intensity and V-gutter angle of attack will result in an increase not only in the size but also in magnitude of the downstream high turbulence areas with vortexes.

scholarly journals A Numerical Study on Premixed Bluff Body Flame of Different Bluff Apex Angle

2013 ◽  
Vol 2013 ◽  
pp. 1-9
Author(s):  
Gelan Yang ◽  
Huixia Jin ◽  
Na Bai
Keyword(s):  
Bluff Body ◽  
Numerical Study ◽  
Apex Angle ◽  
Model Verification ◽  
Combustion Model ◽  
Flame Holder ◽  
Chamber Volume ◽  
Chemically Reacting ◽  
Release Ratio ◽  
Dependent Learning

In order to investigate effects of apex angle (α) on chemically reacting turbulent flow and thermal fields in a channel with a bluff body V-gutter flame holder, a numerical study has been carried out in this paper. With a basic geometry used in a previous experimental study, the apex angle was varied from 45° to 150°. Eddy dissipation concept (EDC) combustion model was used for air and propane premixed flame. LES-Smagorinsky model was selected for turbulence. The gird-dependent learning and numerical model verification were done. Both nonreactive and reactive conditions were analyzed and compared. The results show that asαincreases, recirculation zone becomes bigger, and Strouhal number increases a little in nonreactive cases while decreases a little in reactive cases, and the increase ofαmakes the flame shape wider, which will increase the chamber volume heat release ratio and enhance the flame stability.

Numerical study of turbulent flow over an S-shaped hydrofoil

2008 ◽  
Vol 222 (9) ◽  
pp. 1717-1734 ◽  
Author(s):  
T Micha Prem Kumar ◽  
Dhiman Chatterjee
Keyword(s):  
Shear Stress ◽  
Turbulent Flow ◽  
Flow Separation ◽  
Numerical Study ◽  
Angle Of Attack ◽  
Turbulence Models ◽  
Pressure Gradients ◽  
Convex Surfaces ◽  
Shear Stress Transport ◽  
Formidable Challenge

In this paper, a numerical study of turbulent flow over the S-shaped hydrofoil at 0° angle of attack has been reported. Here, the flow takes place over concave and convex surfaces and is accompanied by the favourable and adverse pressure gradients and flow separation. Modelling such a flow poses a formidable challenge. In the present work four turbulence models, namely, k–∊ realizable, k–ω shear stress transport

Numerical Simulation of Inter-Turbine Burner (ITB) Flows With the Inclusion of V-Gutter Flame Holders

2008 ◽  
Author(s):  
Cheng-Xian Lin ◽  
Balu Sekar ◽  
Joseph Zelina ◽  
Richard Jack Holder ◽  
Hugh Thornburg
Keyword(s):  
Numerical Simulation ◽  
Turbulent Flow ◽  
Air Force ◽  
High Efficiency ◽  
Angle Of Attack ◽  
Three Dimensional ◽  
Flow Feature ◽  
Dissipation Model ◽  
Exit Temperature ◽  
Air Force Research Laboratory

In this paper, a three-dimensional numerical simulation has been performed to study the complex reactive flows during the combustion in an inter-turbine burner (ITB) with the inclusion of V-gutter flame holders. The ITB configuration, which has straight radial vanes (SRV), was based on the innovative, high efficiency, high-g Ultra-Compact Combustor (UCC) concept developed at the Air Force Research Laboratory (AFRL). The V-gutter’s angle of attack was varied from −10 to 10 degrees at fixed JET-A fuel and air injections. The turbulent flow in the ITB was modeled with a RANS-based realizable k-ε turbulence model, while the spray combustion is modeled with an eddy-dissipation model on an unstructured grid. Numerical results indicate that the V-gutter not only generates vortices behind itself, but also alters the turbulent flow feature and mixing behavior between main air flow and the circumferential and SRV cavity flows within the ITB. The exit temperature profile of the ITB can be modified substantially by the inclusion of the V-gutters at different angle of attack. The additional pressure drop incurred by the addition of the V-gutter was found to be less that 1%. Details of the vane cavity dynamics and increased entrainment physics are also discussed in the paper.

scholarly journals Numerical Study of an Oscillating-Wing Wingmill for Ocean Current Energy Harvesting: Fluid-Solid-Body Interaction with Feedback Control

2020 ◽  
Vol 9 (1) ◽  
pp. 23
Author(s):  
David Balam-Tamayo ◽  
Carlos Málaga ◽  
Bernardo Figueroa-Espinoza
Keyword(s):  
Energy Harvesting ◽  
Numerical Study ◽  
Angle Of Attack ◽  
Ocean Current ◽  
Control Synthesis ◽  
Dimensionless Number ◽  
Control Law ◽  
Loop Control ◽  
Power Extraction ◽  
Current Energy

The performance and flow around an oscillating foil device for current energy extraction (a wingmill) was studied through numerical simulations. OpenFOAM was used in order to study the two-dimensional (2D) flow around a wingmill. A closed loop control law was coded in order to follow a reference angle of attack. The objective of this control law is to modify the angle of attack in order to enhance the lift force (and increase power extraction). Dimensional analysis suggests a compromise between the generator (or damper) stiffness and actuator/control gains, so a parametric study was carried out while using a new dimensionless number, called B, which represents this compromise. It was found that there is a maximum on the efficiency curve in terms of the aforementioned dimensionless parameter. The lessons that are learned from this fluid-structure and feedback coupling are discussed; this interaction, combined with the feedback dynamics, may trigger dynamic stall, thus decreasing the performance. Moreover, if the control strategy is not carefully selected, then the energy spent on the actuator may affect efficiency considerably. This type of simulation could allow for the system identification, control synthesis, and optimization of energy harvesting devices in future studies.

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.

Experimental investigation of isothermal and reacting flow characteristics downstream of axisymmetric bluff body stabilizers under stratified or fully premixed inlet mixture conditions

2020 ◽  
Author(s):  
Γεώργιος Πατεράκης
Keyword(s):  
Experimental Investigation ◽  
Turbulent Flow ◽  
Bluff Body ◽  
Operating Conditions ◽  
Reacting Flow ◽  
Wide Range ◽  
Flow Features ◽  
Air Mixing ◽  
The Impact ◽  
Stratified Flames

The current work describes an experimental investigation of isothermal and turbulent reacting flow field characteristics downstream of axisymmetric bluff body stabilizers under a variety of inlet mixture conditions. Fully premixed and stratified flames established downstream of this double cavity premixer/burner configuration were measured and assessed under lean and ultra-lean operating conditions. The aim of this thesis was to further comprehend the impact of stratifying the inlet fuelair mixture on the reacting wake characteristics for a range of practical stabilizers under a variety of inlet fuel-air settings. In the first part of this thesis, the isothermal mean and turbulent flow features downstream of a variety of axisymmetric baffles was initially examined. The effect of different shapes, (cone or disk), blockage ratios, (0.23 and 0.48), and rim thicknesses of these baffles was assessed. The variations of the recirculation zones, back flow velocity magnitude, annular jet ejection angles, wake development, entrainment efficiency, as well as several turbulent flow features were obtained, evaluated and appraised. Next, a comparative examination of the counterpart turbulent cold fuel-air mixing performance and characteristics of stratified against fully-premixed operation was performed for a wide range of baffle geometries and inlet mixture conditions. Scalar mixing and entrainment properties were investigated at the exit plane, at the bluff body annular shear layer, at the reattachment region and along the developing wake were investigated. These isothermal studies provided the necessary background information for clarifying the combustion properties and interpreting the trends in the counterpart turbulent reacting fields. Subsequently, for selected bluff bodies, flame structures and behavior for operation with a variety of reacting conditions were demonstrated. The effect of inlet fuel-air mixture settings, fuel type and bluff body geometry on wake development, flame shape, anchoring and structure, temperatures and combustion efficiencies, over lean and close to blow-off conditions, was presented and analyzed. For the obtained measurements infrared radiation, particle image velocimetry, laser doppler velocimetry, chemiluminescence imaging set-ups, together with Fouriertransform infrared spectroscopy, thermocouples and global emission analyzer instrumentation was employed. This helped to delineate a number of factors that affectcold flow fuel-air mixing, flame anchoring topologies, wake structure development and overall burner performance. The presented data will also significantly assist the validation of computational methodologies for combusting flows and the development of turbulence-chemistry interaction models.

A Numerical Study of Heat Transfer and Flow Structure in Channels With Miniature V Rib-Dimple Hybrid Structure on One Wall

2018 ◽  
Author(s):  
Peng Zhang ◽  
Yu Rao ◽  
Yanlin Li
Keyword(s):  
Heat Transfer ◽  
Turbulent Flow ◽  
Numerical Simulations ◽  
Numerical Study ◽  
Reynolds Numbers ◽  
Hybrid Structure ◽  
Transfer Enhancement ◽  
Nusselt Numbers ◽  
Flow And Heat Transfer ◽  
Flow Mixing

This paper presents a numerical study on turbulent flow and heat transfer in the channels with a novel hybrid cooling structure with miniature V-shaped ribs and dimples on one wall. The heat transfer characteristics, pressure loss and turbulent flow structures in the channels with the rib-dimples with three different rib heights of 0.6 mm, 1.0 mm and 1.5 mm are obtained for the Reynolds numbers ranging from 18,700 to 60,000 by numerical simulations, which are also compared with counterpart of a pure dimpled and pure V ribbed channel. The results show that the overall Nusselt numbers of the V rib-dimple channel with the rib height of 1.5 mm is up to 70% higher than that of the channels with pure dimples. The numerical simulations show that the arrangement of the miniature V rib upstream each dimple induces complex secondary flow near the wall and generates downwashing vortices, which intensifies the flow mixing and turbulent kinetic energy in the dimple, resulting in significant improvement in heat transfer enhancement and uniformness.

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