The Effect of Velocity in High Swirling Flow in Unconfined Burner

2014 ◽  
Vol 69 (6) ◽  
Author(s):  
Norwazan A. R ◽  
Mohammad Nazri Mohd. Jaafar
Keyword(s):  
Flow Field ◽  
Turbulent Flows ◽  
Recirculation Zone ◽  
Swirling Flow ◽  
Numerical Study ◽  
Tangential Velocity ◽  
Reacting Flow ◽  
Ansys Fluent ◽  
Inlet Velocity ◽  
Burner Exit

This paper presents a numerical simulation of swirling turbulent flows in combustion chamber of unconfined burner. Isothermal flows with three different swirl numbers using axial swirler are used to demonstrate the effect of flow in axial velocity and tangential velocity on the center recirculation zone. The significance of center recirculation zone is to ensure a good mixing of air and fuel in order to get a better combustion. The inlet velocity, U0 is 30 m/s entering into the burner through the axial swirler that is represents a high Reynolds number. A numerical study of non-reacting flow in the burner region is performed using ANSYS Fluent. The Reynolds–Averaged Navier–Stokes (RANS) standard k-ε turbulence approach method was applied with the eddy dissipation model. The paper focuses the flow field behind the axial swirler downstream that determined by transverse flow field at different on radial distances. The results of axial and tangential velocity were normalized with the inlet velocity. The velocity profiles are different after undergoing the different swirler up to the burner exit. However, the results of velocity profile showed that the high SN gives a better swirling flow patterns. 

The Reynold’s Number Effect in High Swirling Flow in Unconfined Burner

2015 ◽  
Vol 72 (4) ◽  
Author(s):  
Norwazan A. R. ◽  
Mohammad Nazri Mohd. Jaafar
Keyword(s):  
Turbulent Flows ◽  
Gas Turbines ◽  
Swirling Flow ◽  
Numerical Study ◽  
Isothermal Condition ◽  
Navier Stokes ◽  
Reacting Flow ◽  
Ansys Fluent ◽  
Inlet Velocity ◽  
Burner Exit

The numerical simulations of swirling turbulent flows in isothermal condition in combustion chamber of burner were investigated. The aim is to characterize the main flow structures and turbulence in a combustor that is relevant to gas turbines. Isothermal flows with different inlet flow velocities were considered to demonstrate the effect of radial velocity. The inlet velocity, Uo is varied from 30 m/s to 60 m/s represent a high Reynolds number up to 3.00 X 105. The swirler was located at the upstream of combustor with the swirl number of 0.895. A numerical study of non-reacting flow in the burner region was performed using ANSYS Fluent. The Reynolds–Averaged Navier–Stokes (RANS) approach method was applied with the standard k-ɛ turbulence equations. The various velocity profiles were different after undergoing the different inlet velocity up to the burner exit. The results of velocity profile showed that the high U0 give better swirling flow patterns.

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.

Effect of Dome Geometry on Swirling Flow Field Characteristics of a Counter-Rotating Radial-Radial Swirler

2013 ◽  
Author(s):  
Yi-Huan Kao ◽  
Samir B. Tambe ◽  
San-Mou Jeng
Keyword(s):  
Flow Field ◽  
Flow Structure ◽  
Recirculation Zone ◽  
Swirling Flow ◽  
Aerodynamic Characteristics ◽  
Sudden Expansion ◽  
Reacting Flow ◽  
Clockwise Rotation ◽  
Expansion Angle ◽  
Flow Field Characteristics

An experimental study has been conducted to study the effect of the dome geometry on the aerodynamic characteristics of a non-reacting flow field. The flow was generated by a counter-rotating radial-radial swirler consisting of an inner, primary swirler generating counter-clockwise rotation and an outer, secondary swirler generating clockwise rotation. The dome geometry was modified by introducing dome expansion angles of 60° and 45° with respect to the swirler centerline, in addition to the baseline case of sudden expansion (90°). The flow downstream of the swirler is confined by a 50.8mm × 50.8mm × 304.8mm (2″ × 2″ × 12″) plexiglass chamber. A two-component laser doppler velocimetry (LDV) system was used to measure the velocities in the flow field. The dome geometry is seen to have a clear impact on mean swirling flow structure near the swirler exit rather than the downstream flow field. For the configurations with 60° and 45° expansion, no corner recirculation zone is observed and the swirling flow structure is asymmetric due to the non-axisymmetric dome geometry. The cross-section area of central recirculation zone is larger for dome geometry with 60° expansion angle, as compared to the 90° and 45° cases. The configurations with 60° and 45° expansion have higher magnitudes of negative velocity inside the core of central recirculation zone, as compared to the configuration with 90° expansion angle.

Numerical Study of Non-Reacting and Reacting Flow Characteristics in a Lean Direct Injection Combustor

2011 ◽  
Author(s):  
Dipanjay Dewanji ◽  
Arvind G. Rao ◽  
Mathieu Pourquie ◽  
Jos P. van Buijtenen
Keyword(s):  
Flow Field ◽  
Swirling Flow ◽  
Numerical Study ◽  
Reverse Flow ◽  
Direct Injection ◽  
Flow Characteristics ◽  
Droplet Breakup ◽  
Reacting Flow ◽  
Lean Direct Injection ◽  
Wide Range

The Lean Direct Injection (LDI) combustion concept has been of active interest due to its potential for low emissions under a wide range of operational conditions. This might allow the LDI concept to become the next generation gas-turbine combustion scheme for aviation engines. Nevertheless, the underlying unsteady phenomena, which are responsible for low emissions, have not been widely investigated. This paper reports a numerical study on the characteristics of the non-reacting and reacting flow field in a single-element LDI combustor. The solution for the non-reacting flow captures the essential aerodynamic flow characteristics of the LDI combustor, such as the reverse flow regions and the complex swirling flow structures inside the swirlers and in the neighborhood of the combustion chamber inlet, with reasonable accuracy. A spray model is introduced to simulate the reacting flow field. The reaction of the spray greatly influences the gas-phase velocity distribution. The heat release effect due to combustion results in a significantly stronger and compact reverse flow zone as compared to that of the non-reacting case. The inflow spray is specified by the Kelvin-Helmholtz breakup model, which is implemented in the Reynolds-Averaged Navier Stokes (RANS) code. The results show a strong influence of the high swirling flow field on liquid droplet breakup and flow mixing process, which in turn could explain the low-emission behavior of the LDI combustion concept.

scholarly journals Non-premixed swirl-type tubular flames burning liquid fuels

2018 ◽  
Vol 846 ◽  
pp. 210-239
Author(s):  
Vinicius M. Sauer ◽  
Fernando F. Fachini ◽  
Derek Dunn-Rankin
Keyword(s):  
Flow Field ◽  
Swirling Flow ◽  
Flame Structure ◽  
Flow Analysis ◽  
Liquid Fuels ◽  
Reacting Flow ◽  
Surface Mass ◽  
Surface Mass Transfer ◽  
Incompressible Viscous Flow ◽  
Porous Walls

Tubular flames represent a canonical combustion configuration that can simplify reacting flow analysis and also be employed in practical power generation systems. In this paper, a theoretical model for non-premixed tubular flames, with delivery of liquid fuel through porous walls into a swirling flow field, is presented. Perturbation theory is used to analyse this new tubular flame configuration, which is the non-premixed equivalent to a premixed swirl-type tubular burner – following the original classification of premixed tubular systems into swirl and counterflow types. The incompressible viscous flow field is modelled with an axisymmetric similarity solution. Axial decay of the initial swirl velocity and surface mass transfer from the porous walls are considered through the superposition of laminar swirling flow on a Berman flow with uniform mass injection in a straight pipe. The flame structure is obtained assuming infinitely fast conversion of reactants into products and unity Lewis numbers, allowing the application of the Shvab–Zel’dovich coupling function approach.

Study of Flame Stability in a Step Swirl Combustor

1996 ◽  
Vol 118 (2) ◽  
pp. 308-315 ◽  
Author(s):  
M. D. Durbin ◽  
M. D. Vangsness ◽  
D. R. Ballal ◽  
V. R. Katta
Keyword(s):  
Gas Turbine ◽  
Recirculation Zone ◽  
Swirling Flow ◽  
Tangential Velocity ◽  
Combustion Stability ◽  
Combustion Model ◽  
Fuel Injector ◽  
Gas Turbine Combustor ◽  
Swirl Combustor ◽  
Radial Profiles

A prime requirement in the design of a modern gas turbine combustor is good combustion stability, especially near lean blowout (LBO), to ensure an adequate stability margin. For an aeroengine, combustor blow-off limits are encountered during low engine speeds at high altitudes over a range of flight Mach numbers. For an industrial combustor, requirements of ultralow NOx emissions coupled with high combustion efficiency demand operation at or close to LBO. In this investigation, a step swirl combustor (SSC) was designed to reproduce the swirling flow pattern present in the vicinity of the fuel injector located in the primary zone of a gas turbine combustor. Different flame shapes, structure, and location were observed and detailed experimental measurements and numerical computations were performed. It was found that certain combinations of outer and inner swirling air flows produce multiple attached flames, aflame with a single attached structure just above the fuel injection tube, and finally for higher inner swirl velocity, the flame lifts from the fuel tube and is stabilized by the inner recirculation zone. The observed difference in LBO between co- and counterswirl configurations is primarily a function of how the flame stabilizes, i.e., attached versus lifted. A turbulent combustion model correctly predicts the attached flame location(s), development of inner recirculation zone, a dimple-shaped flame structure, the flame lift-off height, and radial profiles of mean temperature, axial velocity, and tangential velocity at different axial locations. Finally, the significance and applications of anchored and lifted flames to combustor stability and LBO in practical gas turbine combustors are discussed.

Numerical Simulation of Gas Flow in a Square Cyclone Separator With Double Inlets

2007 ◽  
Author(s):  
Bin Xiong ◽  
Xiaofeng Lu ◽  
R. S. Amano
Keyword(s):  
Pressure Drop ◽  
Flow Field ◽  
Gas Flow ◽  
Numerical Study ◽  
Reynolds Stress Model ◽  
Cyclone Separator ◽  
Stress Model ◽  
Inlet Velocity ◽  
Vortex Finder ◽  
Flow Changes

This paper presents a numerical study of gas flow in a square cyclone separator with a double inlet. The turbulence of gas flow is computed by the use of the Reynolds stress model. The distribution of the flow field and pressure drop under different constructional details, which include changes of the shape, size and arrangement of the vortex finder are obtained. The computed results in the distributions of pressure in different sections are verified by comparison with those measured. We found that the center of the flow field is nearly on the geometric center of the cyclone. The flow fields show a feature of Rankine eddy, i.e., a strongly swirling region in the central part and a pseudo-free eddy region of weak swirling intensity near the cyclone wall. Local vortex exists at the corners where the flow changes their direction sharply, but it is less chaotic than in the general square cyclone with a single inlet. The flow field away from the outlet of the vortex finder is different from the Rankine eddy. The pressure-drop increases rapidly with the increase of the inlet velocity, and the pressure-drop increases with the decrease of the diameter of vortex finder and the increase of length of the vortex finder. The calculat ed results of this paper provide some guidance for the optimization of the square cyclone separator structure.

Characterisation of the Instantaneous Velocity and Mixture Field Issuing From a Lean Premixed Module (LPM)

2003 ◽  
Author(s):  
J. F. Carrotte ◽  
C. Batchelor-Wylam
Keyword(s):  
Velocity Field ◽  
Flow Field ◽  
Swirling Flow ◽  
Spectral Characteristics ◽  
Gaseous Fuel ◽  
Constant Current ◽  
Reacting Flow ◽  
Lean Premixed ◽  
Velocity Spectra ◽  
The Individual

Measurements have been made on the non-reacting flow field issuing from a Lean Premixed module (LPM) that incorporates a radial swirler, mixing duct section and nozzle. The geometry contains many features that are thought typical of LPM systems in which gaseous fuel is introduced into a swirling flow at a discrete number of locations. Hot wire anemometry measurements have been used to define the velocity field issuing from the module whilst additional experiments have utilised heated air to simulate gaseous fuel. In this way temperature measurements, using Constant Current Anemometry, have been used to infer the fuel-air mixture field issuing from the module. The velocity data indicates a highly turbulent flow field and the basic spectral characteristics of this velocity field are defined. In addition, within certain regions a strong periodic flow component is observed and is indicative of the instabilities typically associated with swirling flows. The spectral characteristics of the mixture field are also presented and the method by which the mixture and velocity spectra should be compared is outlined. Using this method the measurements indicate the basic spectral characteristics are virtually identical and, furthermore, a periodic fluctuation in the mixture field is also observed. For these types of LPM systems fluctuations in the mixture and velocity fields are therefore strongly correlated. In addition it is shown that the flow fields are dominated by the relatively large time and length scales associated with the main velocity field rather than, say, the much smaller velocity and mixing scales associated with the individual fuel jets.

Influence of the Primary Jets and Fuel Injection on the Aerodynamics of a Prototype Annular Gas Turbine Combustor Sector

2010 ◽  
Author(s):  
Bassam Mohammad ◽  
San-Mou Jeng ◽  
M. Gurhan Andac
Keyword(s):  
Flow Field ◽  
Fuel Injection ◽  
Swirling Flow ◽  
Reacting Flow ◽  
Strong Impact ◽  
Convective Cooling ◽  
Fuel Flow ◽  
Flow Field Characteristics ◽  
Order Of Magnitude ◽  
Primary Jets

Transverse dilution jets are widely used in combustion systems. The current research provides a detailed study of the primary jets of a realistic annular combustion chamber sector. The combustor sector comprises an aerodynamic diffuser, inlet cowl, combustion dome, primary dilution jets, secondary dilution jets and cooling strips to provide convective cooling to the liner. The chamber contracts toward the end to fit the turbine nozzle ring. 2D PIV is employed at an atmospheric pressure drop of 4% (isothermal) to delineate the flow field characteristics. The laser is introduced to the sector through the exit flange. The interaction between the primary jets and the swirling flow as well as the sensitivity of the primary jets to perturbations is discussed. The perturbation study includes: effect of partially blocking the jets, one at a time, the effect of blocking the convective cooling holes, placed underneath the primary jets and shooting perpendicular to it. In addition, the effect of reducing the size of the primary jets as well as off-centering the primary jets is explained. Moreover, PIV is employed to study the flow field with and without fuel injection at four different fuel flow rates. The results show that the flow field is very sensitive to perturbations. The cooling air interacts with the primary jet and influences the flow field although the momentum ratio has a 100:1 order of magnitude. The results also show that the big primary jets dictate the flow field in the primary zone as well as the secondary zone. However, relatively smaller jets mainly influence the primary combustion zone because most of the jet is recirculated back to the CRZ. Also, the jet penetration is reduced with 25% and 11.5% corresponding to a 77% and 62% reduction of the jet’s area respectively. The study indicates the presence of a critical jet diameter beyond which the dilution jets have minimum impact on the secondary region. The jet off-centering shows significant effect on the flow field though it is in the order of 0.4 mm. The fuel injection is also shown to influence the flow field as well as the primary jets angle. High fuel flow rate is shown to have very strong impact on the flow field and thus results in a strong distortion of both the primary and secondary zones. The results provide useful methods to be used in the flow field structure control. Most of the effects shown are attributed to the difference in jet opposition. Hence, the results are applicable to reacting flow.

Numerical Study of Performances of Vertical Axis Tidal Turbines

2012 ◽  
Vol 455-456 ◽  
pp. 296-301
Author(s):  
Yan Liu ◽  
Peng Fei Zhao ◽  
Xiao Hui Su ◽  
Guang Zhao
Keyword(s):  
Flow Field ◽  
Turbulent Flows ◽  
Stokes Equations ◽  
Numerical Study ◽  
Vertical Axis ◽  
Negative Influence ◽  
Navier Stokes ◽  
Speed Ratio ◽  
Tidal Turbines ◽  
Central Shaft

Numerical simulations of flows over two-dimensional vertical axis tidal turbines are carried out. Unsteady Reynolds averaged Navier-Stokes Equations are applied to model turbulent flows. Influence of the central shaft and number of blades on flow field and thus performances of turbines are investigated. Performances in terms of torque and power coefficients are obtained for different types of turbines. Results demonstrates that the central shaft has a negative influence on flow field and power coefficients. Solidity and tip speed ratio are two important factors to affect turbine’s performances. This paper provides useful information for future studies.

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