Radial Swirlers and Mixing Tube Assembly Aerodynamics and Performance Parameters Evaluation: Part 1—Hot-Wire Measurements in the Swirler Exit Plane

2008 ◽  
Author(s):  
Edward Canepa ◽  
Pasquale Di Martino ◽  
Davide Lengani ◽  
Marina Ubaldi ◽  
Pietro Zunino
Keyword(s):  
Turbulence Intensity ◽  
Recent Attempt ◽  
Settling Chamber ◽  
Geometrical Parameters ◽  
Performance Parameters ◽  
Hot Wire ◽  
Flow Angle ◽  
Measuring Campaign ◽  
Tube Assembly ◽  
Range Of Variation

Swirling flows have been widely used to generate the suitable conditions for self substained flames inside modern aeroengine combustors, both for the recirculation generation capability and turbulence intensity. Nevertheless the recent attempt to employ lean premixed prevaporized burners, which can be affected by pressure and velocity fluctuations, requires a deep knowledge of the parameters influencing the swirlers aerodynamics. The purpose of this experimental work is to characterize the aerodynamics of the assembly composed by a centripetal swirler and a straight mixing tube as a function of basic geometrical design parameters. The typical geometrical configuration of the centripetal swirler – mixing tube assembly allows to identify a group of geometrical parameters which can influence the characteristics of the flow leaving both the swirler and the straight duct: the swirler geometrical angle, the vane pitch to chord ratio, and the swirler axial height to mixing tube diameter ratio. Their range of variation has been obtained through the analysis of existing prototypes. According to the range of variation analysis a minimum number of geometries (combinations of the fundamental geometrical parameters) has been defined and tested in order to obtain significant information on the relationships between geometrical parameters and aerodynamic performances. The complex aerodynamic phenomena, which take place both inside and downstream the swirler–mixing tube assembly, have been studied with different and complementary techniques in order to have a complete characterization of the effect of the geometrical parameters variation on many aspects of the flow. All the measuring campaign has been performed at fixed total pressure drop between the settling chamber and the mixing tube outlet section. Present work has been divided in two parts. In the first part, which is here presented, velocity components, turbulence intensity and the flow angle has been measured by means of a two-components crossed miniature hot-wire probe, which has been traversed circumferentially downstream of the swirler vanes. Results from the hot-wire anemometer measuring campaign allow basically to evaluate two main performance parameters which are the swirler velocity reduction coefficient and the mass averaged flow angle, that is actually the main indicator of the swirler capability to deflect the flow and consequently it influences largely the phenomena which can occur in the mixing tube or downstream of the discharge section.

Radial Swirlers and Mixing Tube Assembly Aerodynamics and Performance Parameters Evaluation: Part 2—LDV Measurements at the Mixing Tube Outlet

2008 ◽  
Author(s):  
Edward Canepa ◽  
Pasquale Di Martino ◽  
Davide Lengani ◽  
Marina Ubaldi ◽  
Pietro Zunino
Keyword(s):  
Separation Bubble ◽  
Laser Doppler ◽  
The Other ◽  
Laser Doppler Velocimeter ◽  
Geometrical Parameters ◽  
Outlet Section ◽  
Performance Parameters ◽  
Swirl Number ◽  
Study Results ◽  
Tube Assembly

Present work represents the second part of a two parts paper. The complex aerodynamic phenomena, which take place both inside and downstream the swirler–mixing tube assembly, have been studied with different and complementary techniques in order to have a complete characterization of the effect of the geometrical parameters variation on many aspects of the flow. The first part was focused on the aerodynamic analysis of the flow in the swirler exit plane, while this second part is focused on the experimental investigation on the flow inside and downstream the mixing tube. Measurements have been performed on three axial stations. One is placed inside the mixing tube, in order to characterize the flow arriving from the swirler. The other two are placed downstream the mixing tube discharge section in order to identify the main flow features, such as the presence of flow recirculation and consequently the radial extension of the separation bubble. A four beams two colours Laser Doppler Velocimeter (Dantec Fiber Flow), in backward scatter configuration mounted on a three-axis computer-controlled traversing mechanism, was employed for the present study. Results indicate a strong influence of the geometrical parameters on the flowfield in terms of velocity component distributions, turbulence intensity and separation bubble extension. Moreover results from the Laser Doppler Velocimeter measuring campaign allow basically to evaluate three main performance parameters which are the friction loss coefficient, the semi-theoretical swirl number evaluated from the assembly geometry and the measured swirl number, which is calculated in the mixing tube outlet section. The first one is indicative of the angular momentum dissipation, while the other two represent the main parameters which are involved in the vortex breakdown onset and evolution, that in one case is derived from measurements and in the other is partially theoretical.

Investigation of the Effect of Inlet Turbulence on Transitional Wall-Bounded Flows

2017 ◽  
Author(s):  
Burak Ahmet Tuna ◽  
Xianguo Li ◽  
Serhiy Yarusevych
Keyword(s):  
Boundary Layer ◽  
Turbulence Intensity ◽  
Initial Conditions ◽  
Hydraulic Diameter ◽  
Transition To Turbulence ◽  
Duct Flow ◽  
Entrance Length ◽  
Hot Wire ◽  
Boundary Layer Development ◽  
Layer Development

The present work investigates experimentally the effects of grid-generated turbulence on the transition and the hydrodynamic entrance length in a developing duct flow. Particle Image Velocimetry (PIV) and hot-wire anemometry are used to characterize the flow in a rectangular duct with a length of 1m (∼40Dh) and an aspect ratio of 2 (20mm × 40mm). The inlet turbulence intensity is controlled using different grids, and experiments are performed for a Reynolds number based on hydraulic diameter ReDh = 17,750. Hot-wire and PIV results show that the inlet turbulence intensity has a substantial effect on the flow evolution in the duct, as it substantially changes the boundary layer characteristics in the hydrodynamic entrance region. Analysis shows that, as expected, transition to turbulence advances upstream as the inlet turbulence intensity increases, leading to the decrease in the entrance length. The primary effect is confined to boundary layer development, as the turbulence intensity decays rapidly in the core flow, becoming independent of the initial conditions after about 10 hydraulic diameter (Dh) downstream from the grid. Thus, the analysis is focused on characterizing the boundary layer development and quantifying the associated changes in the flow development along the duct.

scholarly journals Flow and Turbulence Survey for a Model of Gas Turbine Exhaust Diffuser

1995 ◽  
Author(s):  
Umberto Desideri ◽  
Giampaolo Manfrida
Keyword(s):  
Gas Turbines ◽  
Suction Side ◽  
Stationary Flow ◽  
Scale Model ◽  
Medium Size ◽  
Hot Wire ◽  
Flow Measurements ◽  
Flow Angle ◽  
Probe Calibration ◽  
Hot Film

This paper presents the results of an extensive set of measurements on a model of an exhaust diffuser for gas turbines. The diffuser is of the straight-wall annular-axial type, typically employed in small-to-medium size gas turbines. It features six high-solidity struts, which support, in the real machine, one of the shaft bearings and have piping for oil supply inside. The 35%-scale model has been tested on a special test stand developed at the University of Perugia, using the suction side of a centrifugal-flow industrial fan of suitable capacity. Inlet speed is around 80 m/s, allowing satisfactory accuracy for flow measurements and the similarity in terms of Reynolds number. The instrumentation, the movement of the measurement point and data acquisition system were designed for automatic running of the tests. Both pneumatic and hot-wire or hot-film probes can be used on the same facility. The same wind tunnel, previous a quick replacement of the model with a probe calibration test section, can be used for calibration of both pneumatic and hot-wire/hot-film probes. A three hole directional pneumatic probe was used for stationary flow measurements to determine the global performance parameters of the model and a split-film probe was used to determine the turbulence characteristics. For four test sections, contour plots are produced of average velocity components, flow angle and turbulence quantities as three components of the Reynolds stress tensor.

scholarly journals Analysis of the Flow Field in a Radial Compressor

1978 ◽  
Author(s):  
Christian Fradin
Keyword(s):  
Flow Field ◽  
Pressure Field ◽  
Outlet Section ◽  
Inlet Section ◽  
Hot Wire ◽  
Vaneless Diffuser ◽  
Flow Angle ◽  
Radial Compressor ◽  
Pressure Transducers ◽  
Compressor Inlet

Using pressure transducers and hot wire anemometers, the flow and pressure field in a subsonic centrifugal compressor is analyzed. Detailed pressure, velocity, and flow angle maps are given for the compressor inlet section, along the shroud, in the outlet section of the rotor, and also in the vaneless diffuser. These measurements show how flow heterogeneities are generated in the compressor and how they decay in the vaneless diffuser.

scholarly journals Investigation into the turbulence statistics of installed jets using hot-wire anemometry

2020 ◽  
Vol 61 (10) ◽  
Author(s):  
Anderson Proença ◽  
Jack Lawrence ◽  
Rod Self
Keyword(s):  
Shear Layer ◽  
Turbulence Intensity ◽  
Single Point ◽  
Radial Distance ◽  
Convection Velocity ◽  
Turbulence Characteristic ◽  
Hot Wire ◽  
Mean Flow ◽  
Turbulence Statistics ◽  
Jet Mixing

Abstract This work presents a detailed study of the turbulence flow statistics of a jet mounted with its axis parallel to a rigid flat plate. Hot-wire constant temperature anemometry has been used to measure the single-point and two-point statistics of the axial velocity component at several locations within the jet flow field. Results show that the jet mean flow near the plate surface is subjected to a local acceleration and redirection due to a Coandă-type effect. The propagation of these effects downstream of the plate trailing edge is strongly dependent on the plate position. Regarding the velocity fluctuations, the mean turbulence intensity levels are seen to decrease as the radial distance between the jet and surface decreases. Analysis of the single-point power spectral density data on the shear layer close to the plate shows that the reduction in magnitude of the low-frequency content of the energy spectrum is responsible for the decrease in turbulence intensity. Additionally, the characteristic time and length scales computed from two-point measurements reduce as the plate is mounted closer to the jet centre-line. The axial eddy convection velocity is seen to increase in the region of high turbulent kinetic energy in the shear layer adjacent to the surface. Empirical models for turbulence characteristic scales and eddy convection velocity are presented. These findings suggest that both the amplitude and distribution of the jet mixing noise sources are affected when closely installed next to a surface. This paper is a continuation of a recent investigation on the turbulence statistics of isolated jets presented in Proença (Exp Fluids 60(4):63, 2019). Graphic abstract

Effects of Cylinder Diameters, Reynolds Number and Distance Between Two-Tandem Cylinders on the Wake Profile and Turbulence Intensity

2011 ◽  
Author(s):  
Amin Rahimzadeh ◽  
Majid Malek Jafarian ◽  
Amir Khoshnevis
Keyword(s):  
Reynolds Number ◽  
Velocity Profile ◽  
Turbulence Intensity ◽  
Stream Velocity ◽  
Hot Wire ◽  
Velocity Defect ◽  
One Dimensional ◽  
Tandem Cylinders ◽  
Cylinder Diameter ◽  
Spacing Ratio

A series of experimental and numerical investigations on two tandem cylinders wake have been studied. The velocity profile and turbulence intensity have been acquired by a single one dimensional Hot Wire anemometer. The two cylinders were mounted in a tandem manner in the horizontal mid plane of the working section. The effect of the upstream cylinder diameter, Reynolds number and the distance between the cylinders on the wake profile and turbulence intensity on the downstream cylinder was investigated, while the Reynolds number ranged between 1.5× ⟦10⟧ ^4 ∼ 3× ⟦10⟧ ^4. The upstream cylinder diameter (d) was 10, 20 and 25 mm, while the downstream cylinder diameter (D) was 25 mm, corresponding to d/D ranging from 0.4 ∼1.0. The spacing ratio L/d (where L is the distance between the upstream cylinder center and the leading stagnation point of the downstream cylinder) was 2 and 5.5, covering different flow regimes. Observations indicate that two symmetric turbulence intensity peak will occur at mean velocity gradient area. Turbulence area will increase in width for both L/d = 2 and 5.5 as increasing distance from the cylinder (x/D) and decreasing free stream velocity. But totally the range of the turbulence area for L/d = 5.5 is greater than L/d = 2. The wake profiles show that the velocity defect increases as increasing upstream cylinder’s diameter for L/d = 5.5. While this order cannot be accessed for L/d = 2. It is observed that sudden and unusual velocity defect happened for L/d = 2 and d/D = 0.8 cases, which means that the most velocity defect is running on. Also, numerical solution results of velocity profile have been compared with the mentioned experimental results at station 4 and velocity of 10 m/s for both L/d = 2 and 5.5. Results shows a little difference because of using one-dimensional Hot-wire.

Experimental study of self-recirculating casing treatment in a subsonic axial flow compressor

2016 ◽  
Vol 230 (8) ◽  
pp. 805-818 ◽  
Author(s):  
Wei Wang ◽  
Wuli Chu ◽  
Haoguang Zhang ◽  
Yanhui Wu
Keyword(s):  
Axial Flow ◽  
Operating Conditions ◽  
Geometrical Parameters ◽  
Flow Angle ◽  
Casing Treatment ◽  
Axial Flow Compressor ◽  
Blade Tip ◽  
Overall Performance ◽  
Flow Compressor ◽  
Casing Treatments

Parametric studies of recirculating casing treatment were experimentally performed in a subsonic axial flow compressor. The recirculating casing treatment was parameterized with injector throat height, injection position, and circumferential coverage percentage. Eighteen recirculating casing treatments were tested to study the effects on compressor stability and on the compressor overall performance at three blade speeds. The profiles of recirculating casing treatment were optimized to minimize the losses generated by air recirculation. In the experiment, the stalling mass flow rate, total pressure ratio, and adiabatic efficiency of the compressor were measured to study the steady-state effects on the compressor performance of recirculating casing treatments, and static pressure disturbances on the casing wall were monitored to study the influence on stall dynamics. Results indicate that both the compressor stability and overall performance can be improved through recirculating casing treatment with appropriate geometrical parameters for all the test speeds. The influence on stall margin of one geometric parameter often depends on the choice of others, i.e. the interaction effects exist. In general, the recirculating casing treatment with a moderate injector throat and a large circumferential coverage is the optimal choice to enhance compressor stability. The injector of recirculating casing treatment should be placed upstream of the blade tip leading edge and the injector throat height should be lower than four times the rotor tip gap for the benefits of compressor efficiency. At 71% speed, the blade tip loading is decreased through recirculating casing treatment at the operating condition of near peak efficiency and increased near stall. Moreover, the outlet absolute flow angle is reduced in the tip region and enhanced at lower blade spans for both operating conditions. The stall inceptions are not changed with the implementation of recirculating casing treatment for all the test speeds, but the stall patterns are altered at 33% and 53% speeds, i.e. the stall with two cells is detected in the recirculating casing treatment compared with the solid casing with only one stall cell.

A Spectral Study of a Moderately Loaded LPT Airfoil: Part 2—Effects of Turbulence Intensity and Reynolds Number on Frequencies Affecting By-Pass Transition

2012 ◽  
Author(s):  
J. R. S. Graveline ◽  
S. A. Sjolander
Keyword(s):  
Reynolds Number ◽  
Turbulence Intensity ◽  
Spectral Study ◽  
Reynolds Numbers ◽  
Hot Wire ◽  
Spectral Measures ◽  
Single Wire ◽  
Low Pressure Turbine ◽  
Wire Probe ◽  
Tollmien Schlichting

A single wire, hot-wire, probe is used to examine the airflow in, and in close vicinity to, the shearlayer of a Low-Pressure Turbine (LPT) airfoil. The experiment was performed with varying turbulence intensities (Tu) and Reynolds numbers (ReBx); in this work, Re is based on the cascade inflow velocity and axial chord length. In part 1 of the present study [1], the methodology used to identify the key frequencies in the free shearlayer using a combination of statistical and spectral measures of the airflow was first discussed. Here, the focus is on the effects of ReBx and Tu on the spectral results. The frequencies and location in the shearlayer of the Tollmien-Schlichting (TS) waves and Kelvin-Helmholtz (KH) instabilities are shown to be affected by both Tu and ReBx. Additionally, the KH instabilities are shown to undergo pairing.

Experimental Studies on Wake-Induced Transition of Turbulent Boundary Layers

2012 ◽  
Author(s):  
Keiji Takeuchi ◽  
Susumu Fujimoto ◽  
Eitaro Koyabu ◽  
Tetsuhiro Tsukiji
Keyword(s):  
Boundary Layer ◽  
Flat Plate ◽  
Boundary Layers ◽  
Turbulence Intensity ◽  
Intensity Distribution ◽  
Experimental Studies ◽  
Turbulent Boundary Layers ◽  
Bypass Transition ◽  
Pressure Gradients ◽  
Hot Wire

Wake-induced bypass transition of boundary layers on a flat plate subjected to favorable and adverse pressure gradients was investigated. Detailed boundary layer measurements were conducted using two hot-wire probes. A spoked-wheel-type wake generator was used to create periodic wakes in front of the flat plate. The main focus of this study was to reveal the effect of the Strouhal number, which changed by using different numbers of wake-generating bars, on the turbulence intensity distribution and the transition onset position of the boundary layer on the flat plate using two hot-wire probes.

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