Confinement Effects on the Swirling Flow of a Counter-Rotating Swirl Cup

2005 ◽  
Author(s):  
Yongqiang Fu ◽  
Jun Cai ◽  
San-Mou Jeng ◽  
Hukam Mongia
Keyword(s):  
Test Section ◽  
Swirling Flow ◽  
Numerical Models ◽  
Effective Area ◽  
Aerodynamic Characteristics ◽  
Quality Data ◽  
Reynolds Stresses ◽  
Mean Velocity ◽  
Flow Measurements ◽  
Radial Profiles

Gas turbine combustor’s performance, emissions, operability, liner and dome temperature levels and gradients are affected by the degree of confinement expressed indirectly by the dome reference velocity. An experimental investigation was therefore undertaken to characterize the aerodynamic characteristics of non-reacting swirling flow generated by a counter-rotating swirl cup as affected by the test section dimensions. A two-component Laser Doppler Velocimetry (LDV) system was used to measure the mean velocity components and Reynolds stresses of the flowfield generated by the swirl cup installed in 8 square box test sections with width of 3.0, 4.0, 4.1, 4.3, 4.4, 4.5, 5.0, and 6.0 inch, in addition to unconfined flow. Measurements were carried out at fourteen axial distances ranging from 3 to 250 mm downstream of the flare exit, and the radial profiles are obtained through 2 mm intervals. Detailed experimental data are provided to improve mechanistic understanding of the swirl cup generated flowfield as impacted by the ratio of the test section cross-section to the mixer’s effective area. The benchmark quality data are planned for validating the state-of-the-art numerical models in addition more advanced LES approach.

Characteristics of the Swirling Flow Generated by an Axial Swirler

2005 ◽  
Author(s):  
Yongqiang Fu ◽  
San-Mou Jeng ◽  
Robert Tacina
Keyword(s):  
Laser Doppler Velocimetry ◽  
Swirling Flow ◽  
Numerical Models ◽  
Aerodynamic Characteristics ◽  
Flow Fields ◽  
Reynolds Stresses ◽  
Simulated Fuel ◽  
Fuel Nozzle ◽  
The Mean ◽  
Vane Angle

An experimental investigation was conducted to study the aerodynamic characteristics of the confined, non-reacting, swirling flow field. The flow was generated by a helicoidal axial-vaned swirler with a short internal convergent-divergent venturi, which was confined within 2-inch square test section. A series of helicoidal axial-vaned swirlers have been designed with tip vane angles of 40°, 45°, 50°, 55°, 60° and 65°. The swirler with the tip vane angle of 60° was combined with several simulated fuel nozzle insertions of varying lengths. A two-component Laser Doppler Velocimetry (LDV) system was employed to measure the three-component mean velocities and Reynolds stresses. Detailed data are provided to enhance understanding swirling flow with different swirl degrees and geometries and to support the development of more accurate physical/numerical models. The data indicated that the degree of swirl had a clear impact on the mean and turbulent flow fields. The swirling flow fields changed significantly with the addition of a variety of simulated fuel nozzle insertion lengths.

Stereo-PIV Measurements of Turbulent Swirling Flow Inside a Pipe

2020 ◽  
Author(s):  
Ayesha Almheiri ◽  
Lyes Khezzar ◽  
Mohamed Alshehhi ◽  
Saqib Salam ◽  
Afshin Goharzadeh
Keyword(s):  
Swirling Flow ◽  
Reverse Flow ◽  
Tangential Velocity ◽  
Circular Disk ◽  
Pipe Diameter ◽  
Working Fluid ◽  
Complex Flow ◽  
Mean Velocity ◽  
Radial Profiles ◽  
The Mean

Abstract Stereo-PIV is used to map turbulent strongly swirling flow inside a pipe connected to a closed recirculating system with a transparent test section of 0.6 m in length and a pipe diameter of 0.041 m. The Perspex pipe was immersed inside a water trough to reduce the effects of refraction. The working fluid was water and the Reynolds number based on the bulk average velocity inside the pipe and pipe diameter was equal to 14,450. The turbulent flow proceeds in the downstream direction and interacts with a circular disk. The measurements include instantaneous velocity vector fields and radial profiles of the mean axial, radial and tangential components of the velocity in the regions between the swirler exit and circular disk and around this later. The results for mean axial velocity show a symmetric behavior with a minimum reverse flow velocity along the centerline. As the flow developed along the pipe’s length, the intensity of the reversed flow was reduced and the intensity of the swirl decays. The mean tangential velocity exhibits a Rankine-vortex distribution and reached its maximum around half of the pipe’s radius. As the flow approaches the disk, the flow reaches stagnation and a complex flow pattern of vortices is formed. The PIV results are contrasted with LDV measurements of mean axial and tangential velocity. Good agreement is shown over the mean velocity profiles.

scholarly journals Evolution and structure of sink-flow turbulent boundary layers

2001 ◽  
Vol 428 ◽  
pp. 1-27 ◽  
Author(s):  
M. B. JONES ◽  
IVAN MARUSIC ◽  
A. E. PERRY
Keyword(s):  
Boundary Layers ◽  
Velocity Profiles ◽  
Turbulent Boundary Layers ◽  
Reynolds Stresses ◽  
Mean Flow ◽  
Mean Velocity ◽  
Flow Measurements ◽  
Law Of The Wall ◽  
The Mean ◽  
Logarithmic Law

An experimental and theoretical investigation of turbulent boundary layers developing in a sink-flow pressure gradient was undertaken. Three flow cases were studied, corresponding to different acceleration strengths. Mean-flow measurements were taken for all three cases, while Reynolds stresses and spectra measurements were made for two of the flow cases. In this study attention was focused on the evolution of the layers to an equilibrium turbulent state. All the layers were found to attain a state very close to precise equilibrium. This gave equilibrium sink flow data at higher Reynolds numbers than in previous experiments. The mean velocity profiles were found to collapse onto the conventional logarithmic law of the wall. However, for profiles measured with the Pitot tube, a slight ‘kick-up’ from the logarithmic law was observed near the buffer region, whereas the mean velocity profiles measured with a normal hot wire did not exhibit this deviation from the logarithmic law. As the layers approached equilibrium, the mean velocity profiles were found to approach the pure wall profile and for the highest level of acceleration Π was very close to zero, where Π is the Coles wake factor. This supports the proposition of Coles (1957), that the equilibrium sink flow corresponds to pure wall flow. Particular interest was also given to the evolutionary stages of the boundary layers, in order to test and further develop the closure hypothesis of Perry, Marusic & Li (1994). Improved quantitative agreement with the experimental results was found after slight modification of their original closure equation.

scholarly journals Particle Diagnostics and Turbulence Measurements in a Confined Isothermal Liquid Spray

1992 ◽  
Author(s):  
A. Breña de la Rosa ◽  
S. V. Sankar ◽  
G. Wang ◽  
W. D. Bachalo
Keyword(s):  
Flow Field ◽  
Swirling Flow ◽  
Laser Sheet ◽  
Recirculation Region ◽  
Shear Stresses ◽  
Reynolds Stresses ◽  
Mean Velocity ◽  
Recirculation Flow ◽  
Liquid Spray ◽  
Secondary Air

This work reports an experimental study of the behaviour and structure of a liquid spray immersed in a strong swirling field. In order to simulate some of the aerodynamic conditions experienced by a spray in a model combustor, an experimental setup using an acrylic chamber, a vane type swirler, and separate air supplies for both the secondary air and the swirl air were integrated to perform the experiments in the wind tunnel. A vane type swirler exhibiting a high swirl number was used to produce a strong recirculation flow field downstream of a pressure swirl atomizer. Properties of the dispersed phase such as velocity, size distributions, and size-velocity correlations were measured at several locations within the swirling flow field. In addition, mean velocity and turbulence properties were obtained for the gas phase. Flow visualization was performed with a laser sheet to gain further understanding of the formation and influence of the recirculation region on the spray. A 2-component PDPA system with a frequency based Doppler Signal Analyzer was used throughout the measurements, and proved most valuable in the toroidal vortex region where low SNR conditions and non-uniform concentration of seed particles prevail. The results show that flow reversal of the drops is present at this swirl intensity within the recirculation region at distances up to X/D = 2.0. Small variations of drop size distribution within the recirculation region are observed, however large variations outside of it are also present. Plots of the normal Reynolds stresses and Reynolds shear stresses show double-peak radial distributions which indicate regions in the flow where high mean velocity gradients and large shear forces are present. The decay of turbulence velocities in the axial direction was observed to be very fast, an indication of high diffusion and dissipation rates of the kinetic energy of turbulence.

Performance and Near-Wake Measurements for a Vertical Axis Turbine at Moderate Reynolds Number

2013 ◽  
Author(s):  
Peter Bachant ◽  
Martin Wosnik
Keyword(s):  
Reynolds Number ◽  
Numerical Models ◽  
Vertical Axis ◽  
Speed Ratio ◽  
Reynolds Stresses ◽  
Near Wake ◽  
Mean Velocity ◽  
Data Set ◽  
Moderate Reynolds Number ◽  
Vertical Axis Turbine

Experiments were performed with a 1 m diameter, 1 m tall three-bladed vertical axis turbine in a towing tank. Rotor power and drag (or thrust) were measured at a tow speed of 1 m/s, corresponding to a turbine diameter Reynolds number ReD = 106 and an approximate blade chord Reynolds number Rec = λU∞c/ν ∼ 105. Mechanical exergy efficiency estimates were computed from power and drag measurements using an actuator disk approach. Characteristics of the turbine’s near-wake were measured at one turbine diameter downstream. Variation of all three mean and fluctuating velocity components in the vertical and cross-stream directions were measured at peak turbine power output via acoustic Doppler velocimeter. The effect of tip speed ratio on near-wake mean velocity was observed at the turbine center line. Transverse profiles of mean velocity, fluctuating velocity, and Reynolds stresses were also measured at the turbine’s quarter height for two tip speed ratios of interest. Results are compared and contrasted with previous lower Reynolds number studies, and will provide a detailed data set for validation of numerical models.

Spatiotemporal Characterization of a Conical Swirler Flow Field Under Strong Forcing

2009 ◽  
Vol 131 (3) ◽  
Author(s):  
A. Lacarelle ◽  
T. Faustmann ◽  
D. Greenblatt ◽  
C. O. Paschereit ◽  
O. Lehmann ◽  
...  
Keyword(s):  
Flow Field ◽  
Swirling Flow ◽  
Flow Instability ◽  
Laser Doppler Anemometry ◽  
Helical Structure ◽  
Mean Velocity ◽  
Flow Measurements ◽  
Natural Flow ◽  
Flow Frequency

In this study, a spatiotemporal characterization of forced and unforced flows of a conical swirler is performed based on particle image velocimetry (PIV) and laser Doppler anemometry (LDA). The measurements are performed at a Reynolds number of 33,000 and a swirl number of 0.71. Axisymmetric forcing is applied to approximate the effects of thermoacoustic instabilities on the flow field at the burner inlet and outlet. The actuation frequencies are set at the natural flow frequency (Strouhal number Stf≈0.92) and two higher frequencies (Stf≈1.3 and 1.55) that are not harmonically related to the natural frequency. Phase-averaged measurement are used as a first step to visualize the coherent flow structures. Second, proper orthogonal decomposition (POD) is applied to the PIV data to characterize the effect of the actuation on the fluctuating flow. Measurements indicate a typical natural flow instability of helical nature in the unforced case. The associated induced pressure and flow oscillations travel upstream to the swirler inlet where generally fuel is injected. This observation is of critical importance with respect to the stability of the combustion. Harmonic actuation at different frequencies and amplitudes does not affect the mean velocity profile at the outlet, while the coherent velocity fluctuations are strongly influenced at both the inlet and outlet. On one hand, the dominant helical mode is replaced by an axisymmetric vortex ring if the flow is forced at the natural flow frequency. On the other hand, the natural flow frequency prevails at the outlet under forcing at higher frequencies and POD analysis indicates that the helical structure is still present. The presented results give new insight into the flow dynamics of a swirling flow burner under strong forcing.

Behaviour of the Leg of the Horseshoe Vortex Around the Idealized Blade With Zero Attack Angle by Triple Hot-Wire Measurements

1988 ◽  
Author(s):  
Shinji Honami ◽  
Takaaki Shizawa ◽  
Masayuki Takahama
Keyword(s):  
Free Stream ◽  
Horseshoe Vortex ◽  
Constant Thickness ◽  
Reynolds Stresses ◽  
Hot Wire ◽  
Mean Velocity ◽  
Cross Sectional ◽  
Flow Measurements ◽  
Wire Probe ◽  
Vortical Motion

The paper presents the flow measurements within the leg portion of the horseshoe vortex. An uncambered blade of constant thickness downstream with a half-circular nose of an idealized turbine blade was installed on a flat plate. The six components of the Reynolds stresses were measured in addition to the three mean velocity components at two cross-sectional planes by a triple wire probe. The predominant vortical motion of the secondary flow occurs at the corner of the blade and the endwall. The effect of the penetrative motion of the free-stream toward the corner region induced by the vortex on the Reynolds stress is found in u2 profiles near the blade, but not in v2 profiles. The diffusion of the Reynolds stresses is observed in the crossflow direction.

Particle Diagnostics and Turbulence Measurements in a Confined Isothermal Liquid Spray

1993 ◽  
Vol 115 (3) ◽  
pp. 499-506 ◽  
Author(s):  
A. Bren˜a de la Rosa ◽  
S. V. Sankar ◽  
G. Wang ◽  
W. D. Bachalo
Keyword(s):  
Flow Field ◽  
Size Distribution ◽  
Swirling Flow ◽  
Laser Sheet ◽  
Recirculation Region ◽  
Shear Stresses ◽  
Reynolds Stresses ◽  
Velocity Correlation ◽  
Mean Velocity ◽  
Liquid Spray

This work reports an experimental study of the behavior and structure of a liquid spray immersed in a strong swirling field. In order to simulate some of the aerodynamic conditions experienced by a spray in a model combustor, an experimental setup using an acrylic chamber, a vane type swirler, and separate air supplies for both the secondary air and the swirl air were integrated to perform the experiments in the wind tunnel. A vane-type swirler exhibiting a high swirl number was used to produce a strong recirculation flow field downstream of a pressure swirl atomizer. Properties of the dispersed phase such as velocity, size distribution, and size-velocity correlation were measured at several locations within the swirling flow field. In addition, mean velocity and turbulence properties were obtained for the gas phase. Flow visualization was performed with a laser sheet to gain further understanding of the formation and influence of the recirculation region on the spray. A two-component PDPA system with a frequency-based Doppler signal analyzer was used throughout the measurements, and proved most valuable in the toroidal vortex region where low SNR conditions and nonuniform concentration of seed particles prevail. The results show that flow reversal of the drops is present at this swirl intensity within the recirculation region at distances up to X/D = 2.0. Small variations of drop size distribution within the recirculation region are observed; however, large variations outside of it are also present. Plots of the normal Reynolds stresses and Reynolds shear stresses show double-peak radial distributions, which indicate regions in the flow where high mean velocity gradients and large shear forces are present. The decay of turbulence velocities in the axial direction was observed to be very fast, an indication of high diffusion and dissipation rates of the kinetic energy of turbulence.

Detailed Stress Tensor Measurements in a Centrifugal Compressor Vaneless Diffuser

1996 ◽  
Vol 118 (2) ◽  
pp. 394-399 ◽  
Author(s):  
A. Pinarbasi ◽  
M. W. Johnson
Keyword(s):  
Kinetic Energy ◽  
Stress Tensor ◽  
Reynolds Stress ◽  
Centrifugal Compressor ◽  
Energy Levels ◽  
Cfd Modeling ◽  
Reynolds Stresses ◽  
Vaneless Diffuser ◽  
Mean Velocity ◽  
Flow Measurements

Detailed flow measurements have been made in the vaneless diffuser of a large low-speed centrifugal compressor using hot-wire anemometry. The three time mean velocity components and full stress tensor distributions have been determined on eight measurement planes within the diffuser. High levels of Reynolds stress result in the rapid mixing out of the blade wake. Although high levels of turbulent kinetic energy are found in the passage wake, they are not associated with strong Reynolds stresses and hence the passage wake mixes out only slowly. Low-frequency meandering of the wake position is therefore likely to be responsible for the high kinetic energy levels. The anisotropic nature of the turbulence suggests that Reynolds stress turbulence models are required for CFD modeling of diffuser flows.

Experimental and Numerical Investigation of the Precessing Helical Vortex in a Conical Diffuser, With Rotor–Stator Interaction

2016 ◽  
Vol 138 (8) ◽  
Author(s):  
A. Javadi ◽  
A. Bosioc ◽  
H. Nilsson ◽  
S. Muntean ◽  
R. Susan-Resiga
Keyword(s):  
Numerical Simulations ◽  
Test Section ◽  
Swirling Flow ◽  
Draft Tube ◽  
Laser Doppler Anemometry ◽  
Francis Turbine ◽  
Detached Eddy Simulation ◽  
Mean Velocity ◽  
Swirl Generator ◽  
Conical Diffuser

The flow unsteadiness generated in a swirl apparatus is investigated experimentally and numerically. The swirl apparatus has two parts: a swirl generator and a test section. The swirl generator which includes two blade rows, one stationary and one rotating, is designed such that the emanating flow at free runner rotational speed resembles that of a Francis hydroturbine operated at partial discharge. The test section consists of a conical diffuser similar to the draft tube cone of a Francis turbine. Several swirling flow regimes are produced, and the laser Doppler anemometry (LDA) measurements are performed along three survey axes in the test section for different runner rotational speeds (400–920 rpm), with a constant flow rate, 30 l/s. The measured mean velocity components and its fluctuating parts are used to validate the results of unsteady numerical simulations, conducted using the foam-extend-3.0 CFD code. Furthermore, phase-averaged pressure measured at two positions in the draft tube is compared with those of numerical simulations. A dynamic mesh is used together with the sliding general grid interfaces (GGIs) to mimic the effect of the rotating runner. The delayed detached-eddy simulation method, conjugated with the Spalart–Allmaras turbulence model (DDES–SA), is applied to achieve a deep insight about the ability of this advanced modeling technique and the physics of the flow. The RNG k−ε model is also used to represent state-of-the-art of industrial turbulence modeling. Both models predict the mean velocity reasonably well while DDES–SA presents more realistic flow features at the highest and lowest rotational speeds. The highest level of turbulence occurs at the highest and lowest rotational speeds which DDES–SA is able to predict well in the conical diffuser. The special shape of the blade plays more prominent role at lower rotational speeds and creates coherent structures with opposite sign of vorticity. The vortex rope is captured by both turbulence models while DDES–SA presents more realistic one at higher rotational speeds.

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