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.

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.

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.

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.

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.

Flow Investigation Through a 30° Turn Diffusing Duct in Subsonic Flow Regime

2009 ◽  
Author(s):  
Prasanta K. Sinha ◽  
Biswajit Haldar ◽  
Amar N. Mullick ◽  
Bireswar Majumdar
Keyword(s):  
Axial Velocity ◽  
Pressure Loss ◽  
Total Pressure ◽  
High Speed ◽  
Static Pressure ◽  
Transverse Velocity ◽  
Total Pressure Loss ◽  
Pressure Recovery ◽  
Pressure Probe ◽  
Mean Velocity

Curved diffusers are an integral component of the gas turbine engines of high-speed aircraft. These facilitate effective operation of the combustor by reducing the total pressure loss. The performance characteristics of these diffusers depend on their geometry and the inlet conditions. In the present investigation the distribution of axial velocity, transverse velocity, mean velocity, static and total pressures are experimentally studied on a curved diffuser of 30° angle of turn with an area ratio of 1.27. The centreline length was chosen as three times of inlet diameter. The experimental results then were numerically validated with the help of Fluent, the commercial CFD software. The measurements of axial velocity, transverse velocity, mean velocity, static pressure and total pressure distribution were taken at Reynolds number 1.9 × 105 based on inlet diameter and mass average inlet velocity. The mean velocity and all the three components of mean velocity were measured with the help of a pre-calibrated five-hole pressure probe. The velocity distribution shows that the flow is symmetrical and uniform at the inlet and exit sections and high velocity cores are accumulated at the top concave surface due to the combined effect of velocity diffusion and centrifugal action. It also indicates the possible development of secondary motions between the concave and convex walls of the test diffuser. The mass average static pressure recovery and total pressure loss within the curved diffuser increases continuously from inlet to exit and they attained maximum values of 35% and 14% respectively. A comparison between the experimental and predicated results shows a good qualitative agreement between the two. Standard k-ε model in Fluent solver was chosen for validation. It has been observed that coefficient of pressure recovery Cpr for the computational investigation was obtained as 38% compared to the experimental investigation which was 35% and the coefficient of pressure loss is obtained as 13% in computation investigation compared to the 14% in experimental study, which indicates a very good qualitative matching.

Experimental investigation of the role of struts in high speed mixing

2013 ◽  
Vol 117 (1188) ◽  
pp. 193-211 ◽  
Author(s):  
S. L. N. Desikan ◽  
J. Kurian
Keyword(s):  
Pressure Loss ◽  
Total Pressure ◽  
High Speed ◽  
Static Pressure ◽  
Mie Scattering ◽  
Total Pressure Loss ◽  
Pressure Losses ◽  
Mixing Performance ◽  
Supersonic Mixing

AbstractThis paper presents the experimental results of the role of struts in supersonic mixing. Experiments were carried out with novel strut configurations to show their capabilities on mixing with reasonable total pressure losses. The performances were compared with the Baseline Strut configurations (BSPI and BSNI). The analysis presented includes the mixing quantifications using Mie scattering signature, flow field visualisation, measurement of wall static pressure and the total pressure loss calculations. The results clearly demonstrated that the proposed strut configurations achieved increased mixing (7-8%) compared to BSPI with increase in total pressure loss (2%). On the other hand, when compared with BSNI, the mixing performance was found to be decreased by 6% with reduced total pressure loss (12%).

Effect of Casing Geometry on Flow Characteristics in a Model Can-Combustor

2012 ◽  
Author(s):  
Abdur Rahim ◽  
Dhirgham Alkhafagiy ◽  
Prabal Talukdar
Keyword(s):  
Pressure Loss ◽  
Total Pressure ◽  
Static Pressure ◽  
Numerical Study ◽  
Flow Characteristics ◽  
Total Pressure Loss ◽  
Stable Operation ◽  
Flow Uniformity ◽  
Flow Through ◽  
Combustor Liner

In a gas turbine combustor, it is necessary to use a diffuser to decelerate the high velocity air stream delivered by the compressor and thus avoid high total pressure loss. The interaction between the diffuser and combustor external flows plays a key role in controlling the pressure loss, air flow distribution around the combustor liner. Flow through casing-liner annulus is crucial as it feeds air to the primary, secondary and dilution holes. It is important that the annulus flow has sufficient static pressure to achieve adequate penetration of the jets. Moreover, the correct proportion of air enters the combustor liner through the dome and the various ports to maintain stable operation and good quality outlet condition. Length of combustor can be reduced if a provision is made for sufficient diffusion in the dump region. In the present numerical study, three can-combustor models of different geometry with a constant dump-gap have been analyzed with emphasis on the flow through annulus. A comparison has been made amongst the three models in terms of flow uniformity, static pressure recovery and total pressure loss. It is observed that flow uniformity in the annulus region is improved if a small divergence in length and a curved shape step height casing is made.

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.

Geometric Modeling and Analysis for Gooseneck II: 2D Simplified Model for Quick Assessment

2017 ◽  
Author(s):  
Qiuye Tu ◽  
Rutan Deng ◽  
Dongdong Zhang ◽  
Xingjian Sun
Keyword(s):  
Pressure Loss ◽  
Total Pressure ◽  
Geometric Modeling ◽  
Static Pressure ◽  
Outer Wall ◽  
Total Pressure Loss ◽  
Point Location ◽  
Control Variables ◽  
Static Pressure Distribution ◽  
End Wall

In the previous studies, the proposed method for gooseneck geometric modeling employed two polynomials to construct the inner-wall and area distribution curves. The inflection point location served as the variable to control the inner-wall polynomial curve, and the peak point location and peak value to control the area distribution polynomial curve. In the effort to be quickly located, the control variables were provided with more geometric meaning. 3D numerical simulations indicated that there existed a total pressure recovery island for given solution area of the three control variables. Consequently, the relationships between the geometric parameters and the total pressure loss were set up. This paper focused on the 2D simplifications to quickly address the control variables for the total pressure island. The studies were conducted in three aspects. First, the simplified model took the constructional blocking effects of struts into account. The baseline of the 2D simplified modeling was set at 30% spanwise near the hub through comparisons of different settings. Therefore, 70% blocking area compensated to outer-wall and 30% to inner-wall along the normal direction of the baseline. The 2D simulation results indicated that the static pressure distribution was consistent with the 3D results, but waves exited at the end walls of both leading and trailing edges due to the geometric changes. Second, the simplification considered the blocking effects of the wake. The wake was converted to boundary layer thickness, and moreover, compensation to the end wall was similar with the constructional blocking of struts. The simulation results revealed that wake blocking had very small impacts to the simplification, although the peak values of static pressure slightly increased at the end wall. Third, smoothing treatments were done for both inner-wall and outer-wall after the above compensating transformations. The results showed that smoothing treatments were very necessary and improved the waves located at end wall on the static pressure distribution which was nearly the same with 3D results. After all the simplifying treatments above, the final 2D results had almost the same total pressure loss distributions with the 3D results, and could save at least 40% calculation time as a quick assessment used to search the reasonable geometric solution areas of inflection point location and peak point location for minimum total pressure loss of the gooseneck.

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