Laser Insight Into the Turbulent Swirl Flow Behind the Axial Flow Fan

2014 ◽  
Author(s):  
Đorđe S. Čantrak ◽  
Novica Janković ◽  
Milan R. Lečić
Keyword(s):  
Vortex Core ◽  
High Speed ◽  
Isotropic Turbulence ◽  
Laser Doppler Anemometry ◽  
Measurement Techniques ◽  
Swirl Flow ◽  
Test Rig ◽  
Axial Fan ◽  
Mean Velocity ◽  
Swirl Flows

Complex experimental study of the turbulent swirl flow behind the axial fan is reported in this paper. Axial fan with nine blades, designed to generate Rankine vortex, was positioned in the circular pipe entrance transparent section with profiled free bell mouth inlet. Two test rigs were built in order to study the turbulent swirl flow generated on the axial fan pressure side in the case of axially unrestricted and restricted swirl flows. One-component laser Doppler anemometry (LDA) and stereo particle image velocimetry (SPIV) were used in the first test rig in the measuring section 3.35D, measured from the test rig inlet. One of the latest measurement techniques, high speed SPIV (HSS PIV), was used for the measurements in the second test rig in the section 2.1D downstream the fan’s trailing edge. Achieved Reynolds numbers in the first test rig are Re = 182600 and 277020, while in the second Re = 186463. Turbulent velocity field non-homogeneity and anisotropy is revealed using the LDA system. Calculated turbulent statistical properties, such as moments of the second and higher orders, reveal complex mechanisms in turbulent swirl flow. It is shown for the used axial fan construction that swirl number has almost constant value for two various duty points generated by changing rotation number. Study of the instant and mean velocity fields obtained using SPIV discovers vortex core dynamics. Obtained percentage of the unique positions of the total velocity minimum are 10% for the first regime, while 11.5% for the second regime in the first test rig. HSS PIV experimental results have also shown the three-dimensionality and non-homogeneity of generated turbulent swirl flow. Experimentally determined and calculated invariant maps revealed three-component isotropic turbulence in the vortex core region.

scholarly journals Investigation of the free turbulent swirl jet behind the axial fan

2017 ◽  
Vol 21 (suppl. 3) ◽  
pp. 771-782 ◽  
Author(s):  
Novica Jankovic
Keyword(s):  
Experimental Investigation ◽  
Fourth Order ◽  
Isotropic Turbulence ◽  
Laser Doppler Anemometry ◽  
Central Zone ◽  
Swirl Flow ◽  
Axial Fan ◽  
Gaussian Distributions ◽  
Injection Zone ◽  
Flow Anisotropy

Experimental investigation of the free turbulent swirl jet behind the axial fan, by use of the three-component laser Doppler anemometry is presented in this paper. Axial fan generates Rankine swirl. Measurements have been performed in five vertical measuring sections downstream for one rotation number 1500 rpm. Time averaged velocity components and their profile transformation downstream were investigated. Statistical moments of the second, third and fourth order have been calculated and presented. The highest turbulence levels are reached in the central zone, more precisely ? shear layer zone and in the injection zone. Skewness and flatness factors differ from normal Gaussian distributions. Turbulence swirl flow anisotropy is investigated by applying invariant maps. Most of the obtained results are positioned in the region of the three-component isotropic turbulence and axisymmetric expansion.

Flashback in a Swirl Burner With Cylindrical Premixing Zone

2001 ◽  
Author(s):  
Jassin Fritz ◽  
Martin Kröner ◽  
Thomas Sattelmayer
Keyword(s):  
Flame Propagation ◽  
Gas Turbines ◽  
High Speed ◽  
Vortex Breakdown ◽  
Swirling Flow ◽  
Laser Doppler Anemometry ◽  
Burning Velocity ◽  
Turbulent Flame ◽  
Measurement Techniques ◽  
Mean Flow

Flame flashback from the combustion chamber into the mixing zone is one of the inherent problems of lean premixed combustion and essentially determines the reliability of low NOx burners. Generally, flashback can be initiated by one of the following four phenomena: flashback due to the conditions in the boundary layer, flashback due to turbulent flame propagation in the core flow, flashback induced by combustion instabilities and flashback caused by combustion induced vortex breakdown. In this study, flashback in a swirling tubular flow was investigated. In order to draw maximum benefit from the tests with respect to the application in gas turbines, the radial distribution of the axial and circumferential momentum in the tube was selected such that the typical character of a flow in mixing zones of premix burners without centerbody was obtained. A single burner test rig has been designed to provoke flashback with the preheating temperature, the equivalence ratio and the mean flow rate being the influencing parameters. The flame position within the mixing section is detected by a special optical flame sensor array, which allows the control of the experiment and furthermore the triggering of the measurement techniques. The burning velocity of the fuel has been varied by using natural gas or hydrogen. The characteristics of the flashback, the unsteady swirling flow during the flame propagation, the flame dynamics and the reaction zones have been investigated by applying High Speed Video recordings, the Laser Doppler Anemometry and the Laser Induced Fluorescence. The presented results show that a combustion induced vortex breakdown is the dominating mechansim of the observed flashback. This mechanism is very sensitive to the momentum distribution in the vortex core. By adding axial momentum around the mixing tube axis, the circumferential velocity gradient is reduced and flashback can be prevented.

scholarly journals Novel methods for axial fan impeller geometry analysis and experimental investigations of the generated swirl turbulent flow

2010 ◽  
Vol 14 (suppl.) ◽  
pp. 125-139 ◽  
Author(s):  
Zoran Protic ◽  
Milos Nedeljkovic ◽  
Djordje Cantrak ◽  
Novica Jankovic
Keyword(s):  
Standardized Test ◽  
Laser Doppler Anemometry ◽  
Swirl Flow ◽  
Experimental Investigations ◽  
Operating Characteristics ◽  
Axial Fan ◽  
Axial Velocity Component ◽  
Impeller Blade ◽  
Hydraulic Machinery ◽  
Geometry Analysis

Geometry analysis of the axial fan impeller, experimentally obtained operating characteristics and experimental investigations of the turbulent swirl flow generated behind the impeller are presented in this paper. Formerly designed and manufactured, axial fan impeller blade geometry (originally designed by Prof. Dr-Ing. Z. Protic?) has been digitized using a threedimensional (3D) scanner. In parallel, the same impeller has been modeled by beta version software for modeling axial turbomachines, based on modified classical calculation. These results were compared. Then, the axial fan operating characteristics were measured on the standardized test rig in the Laboratory for Hydraulic Machinery and Energy Systems, Faculty of Mechanical Engineering, University of Belgrade. Optimum blade impeller position was determined on the basis of these results. Afterwards, the impeller with optimum angle, without outlet vanes, was positioned in a circular pipe. Rotational speed has been varied in the range from 500 till 2500rpm. Reynolds numbers generated in this way, calculated for axial velocity component, were in the range from 0,8?105 till 6?105. LDA (Laser Doppler Anemometry) measurements and stereo PIV (Particle Image Velocimetry) measurements of the 3D velocity field in the swirl turbulent fluid flow behind the axial fan have been performed for each regime. Obtained results point out extraordinary complexity of the structure of generated 3D turbulent velocity fields.

Effect of the Precessing Vortex Core on Primary Atomization

2015 ◽  
Vol 229 (6) ◽  
Author(s):  
Enrico Bärow ◽  
Sebastian Gepperth ◽  
Rainer Koch ◽  
Hans-Jörg Bauer
Keyword(s):  
Liquid Film ◽  
Vortex Core ◽  
High Speed ◽  
Recirculation Zone ◽  
Film Flow ◽  
Combustion Chambers ◽  
Precessing Vortex Core ◽  
Swirl Flows ◽  
Liquid Film Flow ◽  
Pod Analysis

AbstractThe present work is focused on the airblast atomization in a gas turbine model combustor. Swirl flows in such combustion chambers form an inner recirculation zone that can develop a precessing vortex core. This instability affects the velocity field at the exit of the nozzle, where the fuel is atomized. The influence of the precessing vortex core on the airblast atomization is examined in this work. The flow field in the combustion chamber is examined under reacting and non-reacting conditions. The velocity amplitudes under reacting conditions are more than twice as high compared to non-reacting conditions. The influence of the precessing vortex core on the airblast atomization process is examined in detail at an atomization test rig with a perspex nozzle. High speed shadowgraphy and POD analysis have been performed of the liquid film on the prefilmer as well as on the ligaments formed at the atomizing edge. It was observed that although the PVC does affect the liquid film flow of the prefilming surface, it does not affect the breakup into ligaments, i. e. primary atomization.

On Effect of the Flare Angle on the Behaviour of the Flow Field of Twin-Radial Swirlers/High Shear Injector

2019 ◽  
Author(s):  
Sonu Kumar ◽  
Swetaprovo Chaudhuri ◽  
Saptarshi Basu
Keyword(s):  
Flow Field ◽  
Gas Turbine ◽  
High Speed ◽  
Recirculation Zone ◽  
Swirl Flow ◽  
High Shear ◽  
Gas Turbine Combustor ◽  
Flow Topology ◽  
Mean Velocity ◽  
And Performance

Abstract The swirl flow in gas turbine combustor plays a major role in flame stabilisation and performance of engine. Since the swirl flow is very complex and boundary sensitive phenomena, it is difficult to interpret it properly. High shear injector is being used now a days in modern gas turbine combustor to generate the swirl flow and achieve better fuel atomisation in the combustion chamber. High shear injector accommodates a series of swirlers (primary and secondary) with a diverging flare at the exit and fuel nozzle mounted at the centre of the swirler. In the present study it is tried to understand the influence of the flare angle on the non-reactive flow behaviour of the swirling spray flow-field generated through counter-rotating high shear injector. To perceive the influence of flare angle on the flow topology of the spray flow-field generated by a high shear injector, seven different flare half angles (β): 40°, 45°, 50°, 55°, 60°, 65° and 70° respectively were selected as a geometrical parameter to conduct the experiments. High-Speed Particle Image Velocimetry (HSPIV) technique was employed to perceive the topological structure of the spray flow field, mean and instantaneous behaviour of the velocity fields respectively. For all the cases mass flow of air and liquid (water) were kept constant. It was observed that with change in flare angle the size of the CTRZ, mean velocity and turbulent behaviour were also changing. Here the size of CTRZ is represented in terms of nondimensional radial width (W/Df) and height (H/Df) of the recirculation zone. The experiment was conducted without flare, initially and then subsequently with flares. It was found that both the radial width and the height of the recirculation zone were smallest for without flare case. With increase in flare angle the radial width and height of the CTRZ increases initially up to 60° flare angle and afterward decreased. The experiments made clear that flare angle has strong effect on the spray flow-field.

Description of the flow of mechanically agitated liquid in a system with cylindrical draft-tube and radial baffles

1987 ◽  
Vol 52 (6) ◽  
pp. 1416-1429 ◽  
Author(s):  
Ivan Fořt ◽  
Miloslav Hošťálek ◽  
Hans Dietrich Laufhütte ◽  
Alfons Bertram Mersmann
Keyword(s):  
Stream Function ◽  
High Speed ◽  
Draft Tube ◽  
Laser Doppler Anemometry ◽  
Vertex Angle ◽  
Flat Bottom ◽  
Mean Velocity ◽  
Radial Profiles ◽  
Flow Intensity ◽  
The Mean

A model is described of two-dimensional vortex turbulent flow of homogeneous liquid in a cylindrical tank with flat bottom and radial baffles at its walls agitated with an inclined plane blade impeller rotating in a cylindrical draft-tube. The obtained field of the mean Stokes stream function expresses the streamline distribution in the system. As the boundary conditions of the used solution of stream equation serve partly the values of the mean Stokes stream function on the system boundaries (bottom, liquid level, walls of tank and draft-tube, tank axis), partly the radial profiles of axial and radial components of mean velocity on the level of draft-tube lower base obtained by the laser-doppler anemometry. It follows from the comparison with results of previously published studies that in systems with cylindrical draft-tube and axial high-speed impeller, the convective flow intensity of agitated liquid is higher and the streamline distribution in system is more uniform providing that the conical bottom with 120° vertex angle is used instead of the flat bottom.

scholarly journals Estimation of laser-Doppler anemometry measuring volume displacement in cylindrical pipe flow

2012 ◽  
Vol 16 (4) ◽  
pp. 1027-1042 ◽  
Author(s):  
Slavica Ristic ◽  
Jelena Ilic ◽  
Djordje Cantrak ◽  
Ognjen Ristic ◽  
Novica Jankovic
Keyword(s):  
Pipe Flow ◽  
Pipe Wall ◽  
Laser Doppler Anemometry ◽  
Laser Doppler ◽  
Test Rig ◽  
Axial Fan ◽  
Optical Aberrations ◽  
Cylindrical Pipe ◽  
Measuring Volume ◽  
Uncertainty Sources

Laser-Doppler anemometry application in measurements of the 3-D swirl turbulent flow velocity in the cylindrical pipe, behind the axial fan, have been analysed. This paper presents a brief overview of uncertainty sources in the laser-Doppler anemometry measurements. Special attention is paid to estimation of laser-Doppler anemometry measuring volume positioning in cylindrical pipe flow due to optical aberrations, caused by the pipe wall curvature. The hypothesis, that in the central part of the pipe (r/R < 0.6) exists a small, or negligible pipe wall influence on laser- -Doppler anemometry measuring position, is investigate. The required corrections, for measurements of axial, tangential, and radial velocity components such: shift of measuring volume and its orientation are analyzed and determined for used test rig and for some other pipe geometries.

Flashback in a Swirl Burner With Cylindrical Premixing Zone

2004 ◽  
Vol 126 (2) ◽  
pp. 276-283 ◽  
Author(s):  
J. Fritz ◽  
M. Kro¨ner ◽  
T. Sattelmayer
Keyword(s):  
Flame Propagation ◽  
Gas Turbines ◽  
High Speed ◽  
Vortex Breakdown ◽  
Swirling Flow ◽  
Laser Doppler Anemometry ◽  
Burning Velocity ◽  
Turbulent Flame ◽  
Measurement Techniques ◽  
Mean Flow

Flame flashback from the combustion chamber into the mixing zone is one of the inherent problems of lean premixed combustion and essentially determines the reliability of low NOx burners. Generally, flashback can be initiated by one of the following four phenomena: flashback due to the conditions in the boundary layer, flashback due to turbulent flame propagation in the core flow, flashback induced by combustion instabilities and flashback caused by combustion induced vortex breakdown. In this study, flashback in a swirling tubular flow was investigated. In order to draw maximum benefit from the tests with respect to the application in gas turbines, the radial distribution of the axial and circumferential momentum in the tube was selected such that the typical character of a flow in mixing zones of premix burners without centerbody was obtained. A single burner test rig has been designed to provoke flashback with the preheating temperature, the equivalence ratio and the mean flow rate being the influencing parameters. The flame position within the mixing section is detected by a special optical flame sensor array, which allows the control of the experiment and furthermore the triggering of the measurement techniques. The burning velocity of the fuel has been varied by using natural gas or hydrogen. The characteristics of the flashback, the unsteady swirling flow during the flame propagation, the flame dynamics and the reaction zones have been investigated by applying high-speed video recordings, the laser Doppler anemometry and the laser induced fluorescence. The presented results show that a combustion induced vortex breakdown is the dominating mechanism of the observed flashback. This mechanism is very sensitive to the momentum distribution in the vortex core. By adding axial momentum around the mixing tube axis, the circumferential velocity gradient is reduced and flashback can be prevented.

On-Line Wear Monitoring of Polymer Matrix Composites

2005 ◽  
Vol 475-479 ◽  
pp. 1083-1086 ◽  
Author(s):  
Jan Quintelier ◽  
Patrick de Baets ◽  
Joris Degrieck ◽  
Alessandro Ledda ◽  
W. Philips ◽  
...  
Keyword(s):  
High Speed ◽  
Wear Track ◽  
Polymer Matrix Composites ◽  
Measurement Techniques ◽  
Test Rig ◽  
Composite Surface ◽  
Line Wear ◽  
Fourier Frequency ◽  
Pin On Disc ◽  
Online Measurements

The Laboratory Soete developed a new test setup, based on the well-known pin-on-disc test rig. Instead of the standard composite specimen and steel disc, a rotating composite disc and a steel pin is presently used to have a visible wear track. Other measurement techniques (Acoustic Emission, vibrations, temperature) can be used on the test rig. Continuous monitoring of the wear track combined with standard wear and friction measurements, give results of the current state of the wear track. Fourier frequency analysis (FFT) of these signals gives an indication of the change in condition and contact geometry of the resulting pin-disc combination. A high-speed camera will be used to acquire digital images of the worn composite surface. These online measurements yield to the gradual evolution in damage of the composite specimens.

scholarly journals Investigation of the turbulent swirl flow in pipe generated by axial fans using PIV and LDA methods

2015 ◽  
Vol 42 (3) ◽  
pp. 211-222 ◽  
Author(s):  
Djordje Cantrak ◽  
Novica Jankovic ◽  
Dejan Ilic
Keyword(s):  
Radial Velocity ◽  
Vortex Core ◽  
Axial Velocity ◽  
Swirl Flow ◽  
Core Region ◽  
Circumferential Velocity ◽  
Outer Diameter ◽  
Axial Fan ◽  
Axial Fans ◽  
Measuring Section

In this paper is presented experimental investigation of the turbulent swirl flow in pipe generated by axial fans. Two various models of industrial axial fans are used. One of these is axial fan W30, model AP 400, Minel, Serbia and has seven blades and outer diameter 0.397m. Second axial fan SP30 is model TGT/2-400-6, S&P, Spain, has six blades and outer diameter 0.386m. This results with greater clearance in the second case. Blades were adjusted for both fans at the angle of 30? at the outer diameter. Test rig length is 27.74-D, where D is average inner diameter app. 0.4 m. Measurements are performed in two measuring sections downstream the axial fans (z/D = 3.35 and z/D = 26.31) with one-component laser Doppler anemometry (LDA) system and stereo particle image velocimetry (SPIV). Obtained Reynolds numbers, calculated on the basis of the average axial velocity (Um) in the first measuring section are for fan SP30 Re = 226757, while for fan W30 Re = 254010. Integral flow parameters are determined such as average circulation and swirl number. Significant downstream axial velocity transformation occurs for both fans, while circumferential velocity is decreased, but non-dimensional velocity profile remains the same. Circumferential velocity distribution for both fans in the central zone corresponds to the solid body, while in r/R > 0.4, where D = 2R, distribution is more uniform. Radial velocity in the case of fan SP30 has almost zero values in the measuring section z/D = 3.35, while its values are significantly increased in the downstream section with the maximum in the vortex core region. On the contrary radial velocity decreases downstream for fan W30 and has also maximum value in the vortex core region for both measuring sections. Level of turbulence, skewness and flatness factors are calculated on the basis of the experimental data. The highest levels of turbulence for circumferential velocity are reached in the vortex core region for both fans. It is shown how statistical moments of the third and fourth order differ from the values for normal Gaussian distribution. In this paper are also analyzed velocity fields by use of SPIV.

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