Secondary Flow Control on Axial Flow Compressor Cascade Using Vortex Generators

2014 ◽  
Author(s):  
Ahmed M. Diaa ◽  
Mohammed F. El-Dosoky ◽  
Omar E. Abdel-Hafez ◽  
Mahmoud A. Ahmed
Keyword(s):  
Numerical Simulation ◽  
Secondary Flow ◽  
Three Dimensional ◽  
Axial Flow ◽  
Vortex Generator ◽  
Vortex Generators ◽  
Geometrical Parameters ◽  
Compressor Cascade ◽  
Flow Compressor ◽  
Flow Vortex

Axial flow compressors have a limited operation range due to the difficulty controlling the secondary flow. Vortex generators are considered to control the secondary flow losses and consequently enhance the compressor’s performance. In the present work, a numerical simulation of three-dimensional unsteady compressible flow has been developed in order to gain insight into the nature of this flow. Based on the numerical simulation, the effects of vortex generators with variable geometrical parameters and their application inside the cascade are investigated. The predicted flow fields with and without the vortex generators are presented and discussed. For each configuration of vortex generator, the total pressure and loss coefficient are calculated. The predicted velocity and pressure distributions at different locations are compared with the predicted and measured values available in the literatures.

Benefits of Nonaxisymmetric Endwall Contouring in a Compressor Cascade With a Tip Clearance

2015 ◽  
Vol 137 (5) ◽  
Author(s):  
Mahesh K. Varpe ◽  
A. M. Pradeep
Keyword(s):  
Pressure Loss ◽  
Total Pressure ◽  
Three Dimensional ◽  
Axial Flow ◽  
Vortex Generator ◽  
Tip Clearance ◽  
Total Pressure Loss ◽  
Compressor Cascade ◽  
Pressure Loss Coefficient ◽  
Flow Compressor

This paper describes the design of a nonaxisymmetric hub contouring in a shroudless axial flow compressor cascade operating at near stall condition. Although an optimum tip clearance (TC) reduces the total pressure loss, further reduction in the loss was achieved using hub contouring. The design methodology presented here combines an evolutionary principle with a three-dimensional (3D) computational fluid dynamics (CFD) flow solver to generate different geometric profiles of the hub systematically. The resulting configurations were preprocessed by GAMBIT© and subsequently analyzed computationally using ANSYSFluent©. The total pressure loss coefficient was used as a single objective function to guide the search process for the optimum hub geometry. The resulting three dimensionally complex hub promises considerable benefits discussed in detail in this paper. A reduction of 15.2% and 16.23% in the total pressure loss and secondary kinetic energy (SKE), respectively, is achieved in the wake region. An improvement of 4.53% in the blade loading is observed. Other complimentary benefits are also listed in the paper. The majority of the benefits are obtained away from the hub region. The contoured hub not only alters the pitchwise static pressure gradient but also acts as a vortex generator in an effort to alleviate the total pressure loss. The results confirm that nonaxisymmetric contouring is an effective method for reducing the losses and thereby improving the performance of the cascade.

Numerical Analysis on Axial Compressor Stage Performance With Vortex Generators

2015 ◽  
Author(s):  
Ruchika Agarwal ◽  
Sridharan R. Narayanan ◽  
Shraman N. Goswami ◽  
Balamurugan Srinivasan
Keyword(s):  
Secondary Flow ◽  
Cross Flow ◽  
Axial Compressor ◽  
Axial Flow ◽  
Vortex Generator ◽  
Separated Flow ◽  
Sensitivity Study ◽  
Vortex Generators ◽  
Test Case ◽  
Compressor Stage

The performance of axial flow compressor stage can be improved by minimizing the effects of secondary flow and by avoiding flow separation. At higher blade loading, interaction of tip secondary flow and separated flow on blade surface is more near the tip of the rotor. This results in stall and hence decreases compressor performance. A previous study [1] was carried out to improve the performance of a rotating row of blades with the help of Vortex Generators (VGs) and considerable effects were observed. The current investigation is carried out to find out the effect of Vortex Generator (VG) on the performance of a compressor stage. NASA Rotor 37 with NASA Stator 37 (stage) is used as a test case for the current numerical investigation. VGs are placed at different chord wise as well as span wise locations. A mesh sensitivity study has been done so that simulation result is mesh independent. The results of numerical simulation with different geometrical forms and locations of VGs are presented in this paper. The investigation includes a description of the secondary flow effect and separation zone in compressor stage based on numerical as well as experimental results of NASA Rotor 37 with Stator 37 (without VG). It is also observed that the shape and location of the VG impacts the end wall cross flow and flow deflection [1], which result in enhanced stall range.

CFD Analysis to Investigate the Effect of Vortex Generators on a Transonic Axial Flow Compressor Stage

2015 ◽  
Author(s):  
Avinash Kumar Rajendran ◽  
M. T. Shobhavathy ◽  
R. Ajith Kumar
Keyword(s):  
Pressure Ratio ◽  
Cross Flow ◽  
Axial Flow ◽  
Vortex Generator ◽  
Leading Edge ◽  
Vortex Generators ◽  
Stall Margin ◽  
Compressor Rotor ◽  
Flow Compressor ◽  
End Wall

The performance of the compressor blade is considerably influenced by secondary flow effects, like the cross flow on the end wall as well as corner flow separation between the wall and the blade. Computational Fluid Dynamics (CFD) has been extensively used to analyze the flow through rotating machineries, in general and through axial compressors, in particular. The present work is focused on the studying the effects of Vortex Generator (VG) on test compressor at CSIR National Aerospace Laboratories, Bangalore, India using CFD. The compressor consists of NACA transonic rotor with 21 blades and subsonic stator with 18 vanes. The design pressure ratio is 1.35 at 12930 RPM with a mass flow rate of 22 kg/s. Three configurations of counter rotating VGs were selected for the analysis with 0.25δ, 0.5δ and δ height, where δ was equal to the physical thickness of boundary layer (8mm) at inlet to the compressor rotor [11]. The vortex generators were placed inside the casing at 18 percent of the chord ahead to the leading edge of the rotor. A total of 63 pairs of VGs were incorporated, with three pairs in one blade passage. Among the three configurations, the first configuration has greater impact on the end wall cross flow and flow deflection which resulted in enhanced numerical stall margin of 3.5% from baseline at design speed. The reasons for this numerical stall margin improvement are discussed in detail.

Off-Design Transition and Separation Behavior of a CDA Cascade

1996 ◽  
Vol 118 (2) ◽  
pp. 204-210 ◽  
Author(s):  
W. Steinert ◽  
H. Starken
Keyword(s):  
Three Dimensional ◽  
Axial Flow ◽  
Experimental Information ◽  
Complete Separation ◽  
Surface Boundary ◽  
Compressor Cascade ◽  
Adiabatic Wall ◽  
Design Data ◽  
Flow Compressor ◽  
Separation Behavior

The design of modern axial flow compressor blade sections as well as the code validation require experimental information about the transition and separation behavior of blade surface boundary layers. The experience has shown in the past that such information has to be obtained on the whole surface and not only by point measurements because both transition and separation may be of a three-dimensional nature even in a straight cascade. Therefore, a new visualization technique based on Liquid Crystals (LC), showing the adiabatic wall temperature, has been developed. With this method, transition, local separation, and complete separation can be detected. Design and off-design data of a subsonic (M1 = 0.62) Controlled Diffusion Airfoil (CDA) compressor cascade measured in a wind tunnel are presented. The LC results are supplemented by ink-injection tests and overall performance data.

Effects of Vortex Generator Application on the Performance of a Compressor Cascade

2012 ◽  
Vol 135 (2) ◽  
Author(s):  
Alexander Hergt ◽  
Robert Meyer ◽  
Karl Engel
Keyword(s):  
Secondary Flow ◽  
Cross Flow ◽  
Vortex Generator ◽  
Vortex Generators ◽  
Test Facility ◽  
Compressor Cascade ◽  
Corner Separation ◽  
Design Point ◽  
Flow Effects ◽  
End Wall

The performance of a compressor cascade is considerably influenced by secondary flow effects, like the cross flow on the end wall as well as the corner separation between the wall and the vane. An extensive experimental study of vortex generator application in a highly loaded compressor cascade was performed in order to control these effects and enhance the aerodynamic performance. The results of the study will be used in future projects as a basis for parameterization in the design and optimization process for compressors in order to develop novel nonaxisymmetric endwalls as well as for blade modifications. The study includes the investigation of two vortex generator types with different geometrical forms and their application on several positions in the compressor cascade. The investigation includes a detailed description of the secondary flow effects in the compressor cascade, which is based on numerical and experimental results. This gives the basis for a specific approach of influencing the cascade flow by means of vortex generators. Depending on the vortex generator type and position, there is an impact on the end wall cross flow, the development of the horse shoe vortex at the leading edge of the vane, and the extent of the corner separation achieved by improved mixing within the boundary layer. The experiments were carried out on a compressor cascade at a high-speed test facility at DLR in Berlin at minimum loss (design point) and off-design of the cascade at Reynolds numbers up to Re = 0.6 × 106 (based on 40-mm chord) and Mach numbers up to M = 0.7. At the cascade design point, the total pressure losses could be reduced by up to 9% with the vortex generator configuration, whereas the static pressure rise was nearly unaffected. Furthermore, the cascade deflection could be influenced considerably by vortex generators and also an enhancement of the cascade stall range could be achieved. All these results will be presented and discussed with respect to secondary flow mechanisms. Finally, the general application of vortex generators in axial compressors will be discussed.

Numerical investigation of vortex generators to reduce cross-passage flow phenomena in compressor stator end-walls

2011 ◽  
Vol 225 (7) ◽  
pp. 877-885 ◽  
Author(s):  
J Ortmanns ◽  
C Pixberg ◽  
V Gümmer
Keyword(s):  
Secondary Flow ◽  
Vortex Flow ◽  
Vortex Generator ◽  
Initial Study ◽  
Vortex Generators ◽  
Geometrical Parameters ◽  
Single Vortex ◽  
Stator Vane ◽  
Flow Phenomena ◽  
Generator Design

The numerical results presented in this article demonstrate the ability of single-vortex generators to reduce the cross-passage secondary flow in a high-turning stator vane passage. The sensitivities of the induced vortex flow are determined in an initial study by varying the geometrical parameters. The visualization of the flow patterns and the determination of the stator vane performance show that the efficiency and the working range can be increased by applying single-vortex generators. The vortex generator design has to achieve a balance between the magnitude of vorticity induced to reduce the secondary flow phenomena and the additional losses associated with the produced vortex flow.

On-Line Compressor Cascade Washing for Gas Turbine Performance Investigation

2011 ◽  
Author(s):  
Uyioghosa Igie ◽  
Pericles Pilidis ◽  
Dimitrios Fouflias ◽  
Ken Ramsden ◽  
Paul Lambart
Keyword(s):  
Gas Turbine ◽  
Pressure Ratio ◽  
Three Dimensional ◽  
Axial Flow ◽  
Engine Performance ◽  
Compressor Cascade ◽  
Design Point ◽  
Washing Process ◽  
On Line ◽  
Flow Compressor

On-line compressor washing for industrial gas turbine application is a promising method of mitigating the effects of compressor fouling degradation; however there are still few studies from actual engine experience that are inconclusive. In some cases the authors attribute this uncertainty as a result of other existing forms of degradation. The experimental approach applied here is one of the first of its kind, employing on-line washing on a compressor cascade and then relating the characteristics to a three-dimensional axial flow compressor. The overall performance of a 226MW engine model for the different cases of a clean, fouled and washed engine is obtained based on the changing compressor behavior. Investigating the effects of fouling on the clean engine exposed to blade roughness of 102μm caused 8.7% reduction in power at design point. This is equivalent, typically to 12 months degradation in fouling conditions. Decreases in mass flow, compressor efficiency, pressure ratio and unattainable design point speed are also observed. An optimistic recovery of 50% of the lost power is obtained after washing which lasts up to 10mins. Similarly, a recovery of all the key parameters is achieved. The study provides an insight into compressor cascade blade washing, which facilitates a reliable estimation of compressor overall efficiency penalties based on well established assumptions. Adopting Howell’s theory as well as constant polytropic efficiency, a general understanding of turbomachinery would judge that 50% of lost power recovered is likely to be the high end of what is achievable for the existing high pressure wash. This investigation highlights the obvious benefits of power recovery with on-line washing and the potential to maintain optimum engine performance with frequent washes. Clearly, the greatest benefits accrue when the washing process is initiated immediately following overhaul.

Effects of Vortex Generator Application on the Performance of a Compressor Cascade

2010 ◽  
Author(s):  
Alexander Hergt ◽  
Robert Meyer ◽  
Karl Engel
Keyword(s):  
Secondary Flow ◽  
Cross Flow ◽  
Vortex Generator ◽  
Vortex Generators ◽  
Test Facility ◽  
Compressor Cascade ◽  
Corner Separation ◽  
Design Point ◽  
Flow Effects ◽  
End Wall

The performance of a compressor cascade is considerably influenced by secondary flow effects, like the cross flow on the end wall as well as the corner separation between the wall and the vane. An extensive experimental study of vortex generator application in a highly loaded compressor cascade was performed, in order to control these effects and enhance the aerodynamic performance. The results of the study will be used in future projects as a basis for parameterization in the design and optimization process for compressors in order to develop novel non-axisymmetric endwall as well as for blade modifications. The study includes the investigation of two vortex generator types, with different geometrical forms and their application on several positions in the compressor cascade. The investigation includes a detailed description of the secondary flow effects in the compressor cascade which is based on numerical and experimental results. This gives the basis for a specific approach of influencing the cascade flow by means of vortex generators. Depending on the vortex generator type and position, there is an impact on the end wall cross flow, the development of the horse shoe vortex at the leading edge of the vane and the extent of the corner separation achieved by improved mixing within the boundary layer. The experiments were carried out on a compressor cascade at a high-speed test facility at the DLR in Berlin at minimum loss (design point) and off-design of the cascade at Reynolds numbers up to Re = 0.6 × 106 (based on 40 mm chord) and Mach numbers up to M = 0.7. The cascade consisted of five vanes and their profiles represent the cut near hub of the stator vanes of the single stage axial compressor of the Technical University of Darmstadt. At the cascade design point the total pressure losses could be reduced by up to 9 percent with vortex generator configuration whereas the static pressure rise was nearly unaffected. Furthermore, the cascade deflection could be influenced considerably by vortex generators and also an enhancement of the cascade stall range could be achieved. All these results will be presented and discussed with respect to secondary flow mechanisms.

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