A Global Approach to Turbomachinery Flow Control: Passage Vortex Control

2013 ◽  
Vol 136 (4) ◽  
Author(s):  
Matthew J. Bloxham ◽  
Jeffrey P. Bons
Keyword(s):  
Flow Control ◽  
Pressure Loss ◽  
Total Pressure ◽  
Vortex Generator ◽  
Total Pressure Loss ◽  
Turbine Cascade ◽  
Combined System ◽  
Vortex Control ◽  
Passage Vortex ◽  
Zero Net Mass Flux

A flow control scheme was implemented in a low-pressure turbine cascade that simultaneously mitigated profile and endwall losses using midspan vortex generator jets (VGJs) and endwall suction. The combined system had an approximate zero-net mass flux. During the design, a theoretical model was used that effectively predicted the trajectory of the passage vortex using inviscid results obtained from two-dimensional computational fluid dynamics (CFD). The model was used in the design of two flow control approaches: the removal and redirection approaches. The emphasis of the removal approach was the direct application of flow control along the passage vortex (PV) trajectory. The redirection approach attempted to alter the trajectory of the PV with the judicious placement of suction holes. A potential flow model was created to aid in the design of the redirection approach. The model results were validated using flow visualization and particle image velocimetry (PIV) in a linear turbine cascade. Detailed total pressure loss wake surveys were measured while matching the suction and VGJ mass flow rates for the removal and redirection approaches at ReCx = 25,000 and blowing ratio, B, of 2. When compared with the no control results, the addition of VGJs and endwall suction reduced the wake losses by 69% (removal) and 68% (redirection). The majority of the total pressure loss reduction resulted from the spanwise VGJs, while the suction schemes provided modest additional reductions (<2%). At ReCx = 50,000, the endwall control effectiveness was assessed for a range of suction rates without midspan VGJs. Area-averaged total pressure loss reductions of up to 28% were measured in the wake at ReCx = 50,000, B = 0, with applied endwall suction (compared to no suction at ReCx = 50,000), at which point the loss core of the PV was almost completely eliminated.

Combined Blowing and Suction to Control Both Midspan and Endwall Losses in a Turbomachinery Passage

2010 ◽  
Author(s):  
Matthew J. Bloxham ◽  
Jeffrey P. Bons
Keyword(s):  
Flow Control ◽  
Pressure Loss ◽  
Total Pressure ◽  
System Analysis ◽  
Total Pressure Loss ◽  
Total Power ◽  
Turbine Cascade ◽  
Combined System ◽  
Passage Vortex ◽  
Control Scheme

A flow control scheme was implemented in a low pressure turbine cascade that simultaneously mitigated profile and endwall losses using midspan vortex generator jets (VGJs) and endwall suction. The combined system had an approximate zero-net mass flux. During the design, a theoretical model was used that effectively predicted the trajectory of the passage vortex using inviscid results obtained from two-dimensional CFD. The model was used in the design of two flow control approaches, the removal and redirection approaches. The emphasis of the removal approach was the direct application of flow control along the passage vortex (PV) trajectory. The redirection approach attempted to alter the trajectory of the PV with the judicious placement of suction holes. A potential flow model was created to aid in the design of the redirection approach. The model results were validated using flow visualization and particle image velocimetry (PIV) in a linear turbine cascade. Detailed total pressure loss wake surveys were measured while matching the suction and VGJ mass flow rates, for the removal and redirection approaches at ReCx = 25000 and blowing ratio, B, of 2. When compared with the no control results, the addition of VGJs and endwall suction reduced the wake losses by 69% (removal) and 68% (redirection). The majority of the total pressure loss reduction resulted from the spanwise VGJs while the suction schemes provided modest additional reductions (&lt;2%). At ReCx = 50000 the endwall control effectiveness was assessed for a range of suction rates without midspan VGJs. Area-averaged total pressure loss reductions of up to 28% were measured in the wake at ReCx = 50000, B = 0, with applied endwall suction (compared to no suction at ReCx = 50000), at which point, the loss core of the PV was almost completely eliminated. A system analysis showed that only 23% of the total power gained was needed to power the flow control scheme.

scholarly journals Experimental Studies of Active and Passive Flow Control Techniques Applied in a Twin Air-Intake

2013 ◽  
Vol 2013 ◽  
pp. 1-8 ◽  
Author(s):  
Akshoy Ranjan Paul ◽  
Shrey Joshi ◽  
Aman Jindal ◽  
Shivam P. Maurya ◽  
Anuj Jain
Keyword(s):  
Flow Control ◽  
Pitch Angle ◽  
Pressure Loss ◽  
Total Pressure ◽  
Static Pressure ◽  
Vortex Generator ◽  
Performance Characteristics ◽  
Total Pressure Loss ◽  
Air Intake ◽  
Side Walls

The flow control in twin air-intakes is necessary to improve the performance characteristics, since the flow traveling through curved and diffused paths becomes complex, especially after merging. The paper presents a comparison between two well-known techniques of flow control: active and passive. It presents an effective design of a vortex generator jet (VGJ) and a vane-type passive vortex generator (VG) and uses them in twin air-intake duct in different combinations to establish their effectiveness in improving the performance characteristics. The VGJ is designed to insert flow from side wall at pitch angle of 90 degrees and 45 degrees. Corotating (parallel) and counterrotating (V-shape) are the configuration of vane type VG. It is observed that VGJ has the potential to change the flow pattern drastically as compared to vane-type VG. While the VGJ is directed perpendicular to the side walls of the air-intake at a pitch angle of 90 degree, static pressure recovery is increased by 7.8% and total pressure loss is reduced by 40.7%, which is the best among all other cases tested for VGJ. For bigger-sized VG attached to the side walls of the air-intake, static pressure recovery is increased by 5.3%, but total pressure loss is reduced by only 4.5% as compared to all other cases of VG.

Effect of the Double-Slot Injection on the Leakage Flow Control in a Honeycomb-Tip Turbine Cascade

2019 ◽  
Author(s):  
Yabo Wang ◽  
Yanping Song ◽  
Jianyang Yu ◽  
Fu Chen
Keyword(s):  
Flow Control ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Pressure Loss ◽  
Total Pressure ◽  
Total Pressure Loss ◽  
Leakage Flow ◽  
Turbine Cascade ◽  
Tip Leakage

Abstract The effect of five arrangements of the double-slot injections on the leakage flow control is studied in a honeycomb-tip turbine cascade numerically. The honeycomb tip is covered with 67 intact honeycomb cavities, since the uneven tip is wearable and the cavity vortex could realize the aerodynamic sealing for the leakage flow. Then in the present study, a pair of injection slots is arranged blow each cavity, aiming to enhance the leakage flow suppression by modifying the cavity vortex. According to the orientation of the two slots, five designs of the double-slot injections are proposed. In detail, the two slots are opposite to each other or keep tangential to the original cavity vortex roughly. The three dimensional calculations were completed by using Reynolds-averaged Navier-Stokes (RANS) method and the k-ω turbulence model in the commercial software ANSYS CFX. The estimation of these tip designs is mainly according to the tip leakage mass flow rate and the total pressure loss. Firstly, the injection structures induced by the slots can be divided into X- and T-types inside the cavity. The results show that the T-type structure is more effective in reducing the tip leakage mass flow rate, with the maximum reduction up to 48.2%. Then the effect on the flow field inside the gap and the secondary flow in the upper passage is analyzed. Compared with the flat tip, the span-wise position of the tip leakage vortex core drops within the cascade and the range of the affected loss region expands. At the cascade exit, the tip leakage vortex moves toward the passage vortex near the casing, while the latter’s core rises. The position changes of the secondary vortices eventually determine the total pressure loss contour downstream the cascade. Finally, the injection total pressure and the upper casing motion are investigated. Interestingly, the injection intensity (mass flow rate) increases with the injection total pressure but this value decreases as the casing speed increases. The tip leakage mass flow rate decreases linearly as increasing the injection total pressure or the casing speed. Yet the averaged total pressure loss downstream the cascade increases with the injection total pressure but appears a nonlinear distribution against the casing speed.

The Application of Flow Control to an Aft-Loaded Low Pressure Turbine Cascade With Unsteady Wakes

2008 ◽  
Author(s):  
Jeffrey P. Bons ◽  
Jon Pluim ◽  
Kyle Gompertz ◽  
Matthew Bloxham ◽  
John P. Clark
Keyword(s):  
Reynolds Number ◽  
Flow Control ◽  
Shear Layer ◽  
Pressure Loss ◽  
Total Pressure ◽  
Separation Zone ◽  
Total Pressure Loss ◽  
Separation Control ◽  
Low Pressure Turbine ◽  
Separated Shear Layer

The synchronous application of flow control in the presence of unsteady wakes was studied on a highly-loaded low pressure turbine blade. The L1A blade has a design Zweifel coefficient of 1.34 and a suction peak at 58% axial chord, making it an aft-loaded pressure distribution. Velocity and pressure data were acquired at Rec = 20,000 with 3% incoming freestream turbulence. Unsteady wakes from an upstream vane row are simulated with a moving row of bars at a flow coefficient of 0.76. At this Reynolds number, the blade exhibits a non-reattaching separation bubble beginning at 57% axial chord under steady flow conditions without upstream wakes. The separation zone is modified substantially by the presence of unsteady wakes, producing a smaller separation zone and reducing the area-averaged wake total pressure loss by more than 50%. The wake disturbance accelerates transition in the separated shear layer but stops short of reattaching the flow. Rather, a new time-averaged equilibrium location is established for the separated shear layer, further downstream than without wakes. The focus of this study was the application of pulsed flow control using two spanwise rows of discrete vortex generator jets (VGJs). The VGJs were located at 59% Cx, approximately the peak cp location, and at 72% Cx. The most effective separation control was achieved at the 59% Cx location. Wake total pressure loss decreased 60% from the wake only level and the cp distribution fully recovered its high Reynolds number (attached flow) performance. The VGJ disturbance dominates the dynamics of the separated shear layer, with the wake disturbance assuming a secondary role only. When the pulsed jet actuation (30% duty cycle) was initiated at the 72% Cx location, synchronization with the wake passing frequency (10.6Hz) was key to producing the most effective separation control. A 25% improvement in effectiveness was obtained by aligning the jet actuation between wake events. Evidence suggests that flow control using VGJs will be effective in the highly unsteady LPT environment of an operating gas turbine, provided the VGJ location and amplitude are adapted for the specific blade profile.

Secondary Flow Control Using Vortex Generator Jets

2004 ◽  
Vol 126 (4) ◽  
pp. 650-657 ◽  
Author(s):  
R. K. Sullerey ◽  
A. M. Pradeep
Keyword(s):  
Pressure Loss ◽  
Total Pressure ◽  
Static Pressure ◽  
Vortex Generator ◽  
Control Flow ◽  
Secondary Flows ◽  
Total Pressure Loss ◽  
Vortex Generators ◽  
Vortex Generator Jets ◽  
Inflow Conditions

In this paper, results are presented of an experimental investigation into the effectiveness of vortex generator jets in controlling secondary flows in two-dimensional S-duct diffusers. The experiments were performed in uniform and distorted inflow conditions and the performance evaluation of the diffuser was carried out in terms of static pressure recovery and quality of the exit flow. In the case with inflow distortion, tapered fin vortex generators were employed in addition to vortex generator jets to control flow separation that was detected on the wall with inflow distortion. Detailed measurements including total pressure, velocity distribution, surface static pressure, skin friction, and boundary layer measurements were taken at a Reynolds number of 7.8×105. These results are presented in terms of static pressure rise, distortion coefficient, and total pressure loss coefficient at the duct exit. For uniform inflow, the use of vortex generator jets resulted in more than a 30 percent decrease in total pressure loss and flow distortion coefficients. In combination with passive device (tapered fin vortex generators), the vortex generator jets reduce total pressure losses by about 25 percent for distorted inflow conditions. A potential application of this method may include control of secondary flows in turbo machinery.

Active Separation Control in Circular and Transitioning S-Duct Diffusers Using Vortex Generator Jets

2006 ◽  
Author(s):  
A. M. Pradeep ◽  
R. K. Sullerey
Keyword(s):  
Pressure Loss ◽  
Total Pressure ◽  
Static Pressure ◽  
Vortex Generator ◽  
Loss Coefficient ◽  
Total Pressure Loss ◽  
Separation Control ◽  
Pressure Loss Coefficient ◽  
Distortion Coefficient ◽  
Total Pressure Loss Coefficient

Performance enhancement of three-dimensional S-duct diffusers by separation control using vortex generator jets is the objective of the current experimental investigation. Two different diffuser geometries namely, a circular diffuser and a rectangular–to–circular transitioning diffuser were studied in uniform inflow conditions at a Reynolds number of 7.8 × 105 and the performance evaluation of the diffusers was carried out in terms of static pressure improvement and quality (flow uniformity) of the exit flow. Detailed measurements that included total pressure, velocity distribution, surface static pressure, skin friction and boundary layer measurements were taken and these results are presented here in terms of static pressure rise, distortion coefficient and total pressure loss coefficient at the duct exit. The mass flow rate of the air injected through the VGJ was about 0.06 percent of the main flow for separation control. The distortion coefficient reduced by over 25 percent and the total pressure loss coefficient reduced by about 30 percent in both the diffusers. The physical mechanism of the flow control devices used has been explored using smoke visualization images.

Effect of Turbine Blade tip shape on the Total Pressure Loss of a Turbine Cascade

2009 ◽  
Vol 12 (2) ◽  
pp. 39-45 ◽  
Author(s):  
Ki-Seon Lee ◽  
Seoung-Duck Park ◽  
Young-Chul Noh ◽  
Hak-Bong Kim ◽  
Jae-Su Kwak ◽  
...  
Keyword(s):  
Turbine Blade ◽  
Pressure Loss ◽  
Total Pressure ◽  
Total Pressure Loss ◽  
Turbine Cascade ◽  
Blade Tip

Impact of a Combination of Micro-Vortex Generator and Boundary Layer Suction on Performance in a High-Load Compressor Cascade

2018 ◽  
Author(s):  
Shan Ma ◽  
Wuli Chu ◽  
Haoguang Zhang ◽  
Chuanle Liu
Keyword(s):  
Boundary Layer ◽  
Pressure Loss ◽  
Total Pressure ◽  
Vortex Generator ◽  
Aerodynamic Performance ◽  
Total Pressure Loss ◽  
Control Methods ◽  
Compressor Cascade ◽  
Boundary Layer Suction ◽  
Micro Vortex Generator

The performance of a compressor cascade is considerably influenced by flow control methods. In this paper, the synergistic effects of combination between micro-vortex generators (MVG) and boundary layer suction (BLS) are discussed in a high-load compressor cascade. Seven cases, which are grouped by a kind of micro-vortex generator and boundary layer suction with three locations, are investigated to control secondary flow effects and enhance the aerodynamic performance of the compressor cascade. The MVG is mounted on the end-wall in front of the passage. The rectangle suction slot with three radial positions is installed on the blade suction surface near the trailing edge. The numerical results show that: at the design condition, the total pressure loss is effectively decreased as well as the static pressure coefficient increase when the combined MVG and SBL method (COM) is used, which is superior to MVG in an aerodynamic performance. At the stall condition, the induced vortex coming from MVG could mix the low-energy fluid and mainstream, which result in the reduced separation, and the total pressure loss decreased by 11.54% when the suction flow ratio is 1.5%. The total pressure loss decreases by 14.59% when the COM control methods are applied.

Active Flow Control in Circular and Transitioning S-duct Diffusers

2006 ◽  
Vol 128 (6) ◽  
pp. 1192-1203 ◽  
Author(s):  
A. M. Pradeep ◽  
R. K. Sullerey
Keyword(s):  
Flow Control ◽  
Secondary Flow ◽  
Mass Flow Rate ◽  
Flow Rate ◽  
Pressure Loss ◽  
Total Pressure ◽  
Static Pressure ◽  
Vortex Generator ◽  
Main Flow ◽  
Separation Control

Performance enhancement of three-dimensional S-duct diffusers by secondary flow and separation control using vortex generator jets is the objective of the current experimental investigation. Two different diffuser geometries namely, a circular diffuser and a rectangular—to—circular transitioning diffuser were studied. The experiments were performed in uniform inflow conditions at a Reynolds number of 7.8×105 and the performance evaluation of the diffusers was carried out in terms of static pressure recovery and quality (flow uniformity) of the exit flow. Detailed measurements that included total pressure, velocity distribution, surface static pressure, skin friction, and boundary layer measurements were taken and these results are presented here in terms of static pressure rise, distortion coefficient, total pressure loss coefficient, and the transverse velocity vectors at the duct exit. The use of vortex generator jets resulted in around 26% in total pressure loss and about 22% decrease in flow distortion coefficients in the circular and transitioning diffusers. The mass flow rate of the air injected through the VGJ was about 0.1% of the mass flow rate of the main flow for secondary flow control and about 0.06% of the main flow for separation control. The physical mechanism of the flow control devices used has been explored. The structure of the vortices generated by the control methods are presented in the form of smoke visualization images. The method of flow control used here is perceived to have applications in turbomachinery like turbines and compressors.

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