The Application of Low-Profile Vortex Generators in an Intermediate Turbine Diffuser

2011 ◽  
Vol 134 (1) ◽  
Author(s):  
C. Santner ◽  
E. Göttlich ◽  
A. Marn ◽  
J. Hubinka ◽  
B. Paradiso
Keyword(s):  
Flow Behavior ◽  
Adverse Pressure Gradient ◽  
Low Pressure ◽  
Vortex Generators ◽  
Passive Flow Control ◽  
Turbofan Engines ◽  
Flow Control Devices ◽  
Flow Disturbances ◽  
Low Profile ◽  
Oil Flow

The demand of further increased bypass ratios for turbofan engines will lead to low pressure turbines with larger diameter and lower rotational speed in conventional high-bypass aeroengine architectures. Due to that, it is necessary to guide the flow leaving the high pressure turbine to the low pressure turbine at a larger diameter without any severe loss generating separation or flow disturbances. To reduce costs and weight this turbine duct has to be as short as possible. This results in superaggressive (very high diffusion) S-shaped geometries where the boundary layers are not able to withstand the strong adverse pressure gradient, which results in flow separation. This paper describes the flow through a fully separated duct as a baseline configuration. In a next step the influence of passive flow control devices onto this separation has been investigated. Therefore, low-profile vortex generators were applied within the first bend of this S-shaped intermediate turbine diffuser in order to energize the boundary layer and further reduce or even suppress the occurring separation. This configuration was investigated downstream a transonic turbine stage. Measurements were performed by means of five-hole-probes, static wall pressure taps, and oil flow visualization at the duct endwalls. For a better understanding of the flow behavior the vortex generators were also investigated in a two-dimensional rectangular S-shaped duct using the same Mach number level. Results showed that the vortex generators reduce the separation in the 2D-duct but have no distinct influence on the separation within the turbine duct due to wakes as well as strong secondary flow effects.

The Application of Low-Profile Vortex Generators in an Intermediate Turbine Diffuser

2010 ◽  
Author(s):  
C. Santner ◽  
E. Go¨ttlich ◽  
A. Marn ◽  
J. Hubinka ◽  
B. Paradiso
Keyword(s):  
Flow Behavior ◽  
Adverse Pressure Gradient ◽  
Low Pressure ◽  
Vortex Generators ◽  
Passive Flow Control ◽  
Turbofan Engines ◽  
Flow Control Devices ◽  
Flow Disturbances ◽  
Low Profile ◽  
Oil Flow

The demand of further increased bypass ratios for turbofan engines will lead to low pressure turbines with larger diameter and lower rotational speed in conventional high-bypass aero engine architectures. Due to that, it is necessary to guide the flow leaving the high pressure turbine to the low pressure turbine at a larger diameter without any severe loss generating separation or flow disturbances. To reduce costs and weight this turbine duct has to be as short as possible. This results in super-aggressive (very high diffusion) s-shaped geometries where the boundary layers are not able to withstand the strong adverse pressure gradient which results in flow separation. This paper describes the flow through a fully separated duct as a baseline configuration. In a next step the influence of passive flow control devices onto this separation has been investigated. Therefore, low-profile vortex generators were applied within the first bend of this s-shaped intermediate turbine diffuser in order to energize the boundary layer and further reduce or even suppress the occurring separation. This configuration was investigated downstream a transonic turbine stage. Measurements were performed by means of five-hole-probes, static wall pressure taps and oil flow visualization at the duct endwalls. For a better understanding of the flow behavior the vortex generators were also investigated in a two-dimensional rectangular s-shaped duct using the same Mach number level. Results showed that the vortex generators reduce the separation in the 2D-duct but have no distinct influence on the separation within the turbine duct due to wakes as well as strong secondary flow effects. This work is part of the European project AIDA (Contract: AST3-CT-2003-502836).

Asymptotic Wake Behavior of Swept, Blunt Trailing-Edge Airfoils

1994 ◽  
Vol 116 (1) ◽  
pp. 171-174
Author(s):  
G. V. Selby ◽  
F. H. Miandoab
Keyword(s):  
Streamwise Velocity ◽  
Vortex Generators ◽  
Wake Flow ◽  
Sweep Angle ◽  
Passive Flow Control ◽  
Blunt Trailing Edge ◽  
Passive Flow ◽  
Asymptotic Values ◽  
Flow Control Devices ◽  
Control Devices

The effect of base sweep and the addition of passive flow-control devices at constant base sweep angle (30 deg) on the asymptotic behavior of turbulent wakes produced by flatplate airfoils was experimentally examined. It was determined that values of the nondimensional streamwise velocity defect and wake thickness parameters for the grooved model with 30 deg swept base at fourteen base thicknesses downstream of the base at mid-span were closer to asymptotic values from empirical plane wake predictions than values for the 0, 30, and 45 deg swept baseline models and the 30 deg swept model with Wishbone vortex generators. The grooves apparently inhibited the three-dimensionality of the resulting wake flow.

Vortex Generators for Wind Turbine Blades: A Combined Wind Tunnel and Wind Turbine Parametric Study

2012 ◽  
Author(s):  
Hanns Mueller-Vahl ◽  
Georgios Pechlivanoglou ◽  
C. N. Nayeri ◽  
C. O. Paschereit
Keyword(s):  
Wind Turbine ◽  
Turbine Blades ◽  
Aerodynamic Performance ◽  
Force Balance ◽  
Vortex Generators ◽  
Wind Turbine Blades ◽  
Passive Flow Control ◽  
Flow Control Devices ◽  
Performance Curves ◽  
Stall Angle

Vortex generators (VGs) are passive flow control devices commonly employed to prevent flow separation on wind turbine blades. They mitigate the damaging fatigue loads resulting from stall while increasing lift and consequently lead to rotor torque increase. This work summarizes a research project aimed at optimizing the sectional as well as the full rotor-blade aerodynamics using VGs. The effects of chordwise position, spanwise spacing and VG size were studied with force balance measurements of a 2D wing section. Reducing the distance between adjacent VGs produced large increases in the static stall angle and maximum lift, but also resulted in a significant increase in drag as well as sharp lift excursions at angles exceeding the static stall angle. The optimal chordwise position of the vortex generators was found to be in the range of x/c = 15%–20%, where a comparatively low parasitic drag and a smooth post-stall lift curve were achieved. Particle Image Velocimetry measurements were conducted at various chordwise positions to provide insight into the interaction between adjacent streamwise vortices. The experimental aerodynamic performance curves of the optimal VG configuration were used to project their effect on wind turbine blade aerodynamics. Three different rotorblades were designed and several stall and pitch regulated wind turbine models were simulated by means of a Blade Element Momentum (BEM) code (QBlade) developed by Smart Blade GmbH. The performance of the rotorblades with and without VGs was simulated in order to assess their effect on the aerodynamic performance and loads. Finally, previously measured steady state performance curves under high-roughness conditions were used to simulate the detrimental effect of surface roughness on the performance of the aforementioned rotorblades. This allows for an estimate of the potential of the VGs to be employed as retrofit elements for performance recovery of blades with a contaminated surface.

Flow behavior of skewed vortex generators on a backward-facing ramp

2021 ◽  
pp. 095441002199618
Author(s):  
Atcha-uea Cheawchan ◽  
Yiming Wen ◽  
Zhen Wei Teo ◽  
Bing Feng Ng ◽  
Tze How New
Keyword(s):  
Vortex Core ◽  
Flow Behavior ◽  
Strong Dependence ◽  
Vertical Direction ◽  
Stereoscopic Particle Image Velocimetry ◽  
Vortex Generators ◽  
Streamwise Vortices ◽  
Oil Flow ◽  
The Right ◽  
The Impact

The impact of skewness angle on the effectiveness of vortex generators (VGs) and the behavior of streamwise vortices on flow separation behind a backward-facing ramp (BFR) with a sharp transition were experimentally investigated using surface oil flow visualizations, planar and stereoscopic particle image velocimetry measurements. Counter/corotating streamwise vortices were generated by a set of boundary layer-type rectangular VG located upstream of the BFR that comprised a flat- and 30-inclined sections with different skewness angles of 10°, 20°, and 30°. Local Reynolds number based on the VG location was Rex ≈ 3 × 106. Results show that the reattachment length was reduced by ∼45% when the VG was located five times its height ahead of the transition. Additionally, the behavior of the vortex core generated by the left vane displayed strong dependence on the skewness angle, whereby its vorticity magnitude and vortex instability increase with the skewness angle. Circulation magnitude and vortex radius of the left vortex core are also observed to be physically larger and less stable. In contrast, the vortex core produced by the right vane displays opposite behavior as the skewness angle increases. Lastly, the vortex core location is observed to fluctuate more in the vertical direction than horizontal direction.

Developement of a Turning Mid Turbine Frame With Embedded Design: Part I — Design and Steady Measurements

2013 ◽  
Author(s):  
Rosario Spataro ◽  
Emil Göttlich ◽  
Davide Lengani ◽  
Christian Faustmann ◽  
Franz Heitmeir
Keyword(s):  
Flow Behavior ◽  
Low Pressure ◽  
Meridional Flow ◽  
Secondary Flows ◽  
Time Resolved ◽  
Embedded Design ◽  
Oil Flow ◽  
Field Uniformity ◽  
Flow Gradients ◽  
Lp Turbine

The paper presents a new setup for the two-stage two-spool facility located at the Institute for Thermal Turbomachinery and Machine Dynamics (ITTM) of Graz University of Technology. The rig was designed in order to simulate the flow behavior of a transonic turbine followed by a counter rotating low pressure stage like the spools of a modern high bypass aero engine. The meridional flow path of the machine is characterized by a diffusing S-shaped duct between the two rotors. The role of turning struts placed into the mid turbine frame is to lead the flow towards the LP rotor with appropriate swirl. Experimental and numerical investigations performed on the setup over the last years, which were used as baseline for this paper, showed that wide chord vanes induce large wakes and extended secondary flows at the LP rotor inlet flow. Moreover, unsteady interactions between the two turbines were observed downstream of the LP rotor. In order to increase the uniformity and to decrease the unsteady content of the flow at the inlet of the LP rotor, the mid turbine frame was redesigned with two zero-lifting splitters embedded into the strut passage. In this first part paper the design process of the splitters and its critical points are presented, while the time-averaged field is discussed by means of five-hole probe measurements and oil flow visualizations. The comparison between the baseline case and the embedded design configuration shows that the new design is able to reduce the flow gradients downstream of the turning struts, providing a more suitable inlet condition for the low pressure rotor. The improvement in the flow field uniformity is also observed downstream of the turbine and it is consequently reflected in an enhancement of the LP turbine performance. In the second part of this paper the influence of the embedded design on the time-resolved field is investigated.

Three-dimensional characterization of passive flow control devices over an aircraft carrier ski-jump ramp

2017 ◽  
Vol 232 (15) ◽  
pp. 2737-2744
Author(s):  
R Bardera ◽  
A Rodríguez-Sevillano ◽  
M León-Calero ◽  
J Nova-Trigueros
Keyword(s):  
Flow Control ◽  
Three Dimensional ◽  
Vortex Generator ◽  
Geometrical Parameters ◽  
Aircraft Carrier ◽  
Recirculation Bubble ◽  
Passive Flow Control ◽  
Passive Flow ◽  
Flow Control Devices ◽  
Flow Disturbances

The aircraft carrier is a key element in modern navies. On-board operations at sea take place under very severe conditions, which affect the aerodynamic flow on the flight deck. The ski-jump ramp is a curved runway that enables the aircraft to take-off using shorter runway distance. However, this geometry generates strong flow disturbances, mainly characterized by a recirculation bubble at the forward end of the ramp. This phenomenon reduces the aircraft performances and increases the pilot’s workload due to the unsteady forces which appear on the control surfaces. Passive flow control appears as a solution to this problem. Wind tunnel experimental research was developed in this study to mitigate the adverse aerodynamic effects of the ski-jump ramp presence. Different devices were tested using particle image velocimetry. Geometrical parameters of the devices were varied to study the effectiveness and select the best solution. Interesting results were found for the columnar vortex generator configurations. The optimum configuration could be applied shortly to the full-scale problem to reduce the adverse aerodynamic effects during take-off maneuvers.

Flow Control in an Aggressive Interturbine Transition Duct Using Low Profile Vortex Generators

2014 ◽  
Vol 136 (11) ◽  
Author(s):  
Yanfeng Zhang ◽  
Shuzhen Hu ◽  
Xue-Feng Zhang ◽  
Michael Benner ◽  
Ali Mahallati ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Flow Control ◽  
Separated Flow ◽  
Adverse Pressure Gradient ◽  
Boundary Layer Separation ◽  
Vortex Generators ◽  
Pressure Losses ◽  
Layer Separation ◽  
Low Profile ◽  
Flow Mechanisms

This paper presents an experimental investigation of the flow mechanisms in an aggressive interturbine transition duct with and without low-profile vortex generators flow control. The interturbine duct had an area ratio of 1.53 and a mean rise angle of 35 deg. Measurements were made inside the annulus at a Reynolds number of 150,000. At the duct inlet, the background turbulence intensity was raised to 2.3% and a uniform swirl angle of 20 deg was established with a 48-airfoil vane ring. Results for the baseline case (no vortex generators) showed the flow structures within the duct were dominated by counter-rotating vortices and boundary layer separation in both the casing and hub regions. The combination of the adverse pressure gradient at the casing's first bend and upstream low momentum wakes caused the boundary layer to separate on the casing. The separated flow on the casing appears to reattach at the second bend. Counter-rotating and corotating vortex generators were installed on the casing. While both vortex generators significantly decreased the casing boundary layer separation with consequential reduction of overall pressure losses, the corotating configuration was found to be more effective.

Development of a Turning Mid Turbine Frame With Embedded Design—Part I: Design and Steady Measurements

2014 ◽  
Vol 136 (7) ◽  
Author(s):  
Rosario Spataro ◽  
Emil Göttlich ◽  
Davide Lengani ◽  
Christian Faustmann ◽  
Franz Heitmeir
Keyword(s):  
Flow Behavior ◽  
Low Pressure ◽  
Meridional Flow ◽  
Secondary Flows ◽  
Time Resolved ◽  
Embedded Design ◽  
Oil Flow ◽  
Field Uniformity ◽  
Flow Gradients ◽  
Lp Turbine

The paper presents a new setup for the two-stage two-spool facility located at the Institute for Thermal Turbomachinery and Machine Dynamics (ITTM) of Graz University of Technology. The rig was designed in order to simulate the flow behavior of a transonic turbine followed by a counter-rotating low pressure (LP) stage like the spools of a modern high bypass aeroengine. The meridional flow path of the machine is characterized by a diffusing S-shaped duct between the two rotors. The role of turning struts placed into the mid turbine frame is to lead the flow towards the LP rotor with appropriate swirl. Experimental and numerical investigations performed on the setup over the last years, which were used as baseline for this paper, showed that wide chord vanes induce large wakes and extended secondary flows at the LP rotor inlet flow. Moreover, unsteady interactions between the two turbines were observed downstream of the LP rotor. In order to increase the uniformity and to decrease the unsteady content of the flow at the inlet of the LP rotor, the mid turbine frame was redesigned with two zero-lifting splitters embedded into the strut passage. In this first part of the paper the design process of the splitters and its critical points are presented, while the time-averaged field is discussed by means of five-hole probe measurements and oil flow visualizations. The comparison between the baseline case and the embedded design configuration shows that the new design is able to reduce the flow gradients downstream of the turning struts, providing a more suitable inlet condition for the low pressure rotor. The improvement in the flow field uniformity is also observed downstream of the turbine and it is, consequently, reflected in an enhancement of the LP turbine performance. In the second part of this paper the influence of the embedded design on the time-resolved field is investigated.

Steady longitudinal vortices in supersonic turbulent separated flows

2011 ◽  
Vol 672 ◽  
pp. 451-476 ◽  
Author(s):  
ERICH SCHÜLEIN ◽  
VICTOR M. TROFIMOV
Keyword(s):  
High Speed ◽  
Large Scale ◽  
Roughness Element ◽  
Vortex Generator ◽  
Vortex Pair ◽  
Leading Edge ◽  
Separated Flows ◽  
Vortex Generators ◽  
Longitudinal Vortices ◽  
Oil Flow

Large-scale longitudinal vortices in high-speed turbulent separated flows caused by relatively small irregularities at the model leading edges or at the model surfaces are investigated in this paper. Oil-flow visualization and infrared thermography techniques were applied in the wind tunnel tests at Mach numbers 3 and 5 to investigate the nominally 2-D ramp flow at deflection angles of 20°, 25° and 30°. The surface contour anomalies have been artificially simulated by very thin strips (vortex generators) of different shapes and thicknesses attached to the model surface. It is shown that the introduced streamwise vortical disturbances survive over very large downstream distances of the order of 104 vortex-generator heights in turbulent supersonic flows without pressure gradients. It is demonstrated that each vortex pair induced in the reattachment region of the ramp is definitely a child of a vortex pair, which was generated originally, for instance, by the small roughness element near the leading edge. The dependence of the spacing and intensity of the observed longitudinal vortices on the introduced disturbances (thickness and spanwise size of vortex generators) and on the flow parameters (Reynolds numbers, boundary-layer thickness, compression corner angles, etc.) has been shown experimentally.

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