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.

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 on the Effect of Vortex Generator on Axial Compressor Performance

2014 ◽  
Author(s):  
Ruchika Agarwal ◽  
Anand Dhamarla ◽  
Sridharan R. Narayanan ◽  
Shraman N. Goswami ◽  
Balamurugan Srinivasan
Keyword(s):  
Cross Flow ◽  
Axial Compressor ◽  
Vortex Generator ◽  
Side Surface ◽  
Suction Side ◽  
Test Case ◽  
Stall Margin ◽  
Layer Flow ◽  
Flow Effects ◽  
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. The present work is focused on the studying the effects of Vortex Generator (VG) on NASA Rotor 37 test case using Computational Fluid Dynamics (CFD). VG helps in controlling the inception of the stall by generating vortices and energizes the low momentum boundary layer flow which enhances the rotor performance. Three design configuration namely, Counter-rotating, Co-rotating and Plow configuration VG are selected based on the improved aerodynamic performance discussed in reference [1]. These VG are located at 90% span and 42% chord on suction side surface of the blade. 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 5.4% from baseline. The reasons for this numerical stall margin improvement are discussed in detail.

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.

Effects of Vortex-Vortex Interaction in a Compressor Cascade With Vortex Generators

2015 ◽  
Author(s):  
Tan Zheng ◽  
Xiaoqing Qiang ◽  
Jinfang Teng
Keyword(s):  
High Speed ◽  
Vortex Generator ◽  
Aerodynamic Performance ◽  
Extensive Study ◽  
Vortex Generators ◽  
Separation Flow ◽  
Vortex Interaction ◽  
Compressor Cascade ◽  
Corner Separation ◽  
Flow Phenomena

This paper presents a numerical investigation to explore the effects of vortex generators on a high speed compressor cascade. Secondary flow effects like the corner separation vortex have an influence on the performance of a compressor cascade such as leading to increased losses. In order to control the corner separation vortex and reduce losses, an extensive study of vortex generators applied to a compressor cascade is conducted. A preliminary study by steady 3D RANS simulations is performed using the Spalart-Allmaras turbulence model. The aerodynamic performance as well as the behavior of the corner separation vortex is investigated in the compressor cascade without vortex generators. Then, a vortex generator is added to the cascade, which is numerically simulated. Various configurations are considered, which are decided by the height and installation angle of the vortex generator. Comparison of the performance attained by these configurations results in an optimum scheme that has minimum losses. Furthermore, unsteady 3D DES simulations are performed with the optimum configuration. This method that predicts the flow field more precisely could help verify the accuracy of the RANS results. Finally, by analyzing all the resulting aerodynamic performance and numerical flow phenomena, the mechanism of vortex-vortex interaction is presented and discussed, which could be a criterion to reduce the corner separation flow and enhance the performance of axial compressors.

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.

Effect of the end-wall vortex generator jets on the performance of a high subsonic compressor cascade

2018 ◽  
Vol 233 (3) ◽  
pp. 324-336
Author(s):  
Cong Chen ◽  
Huaping Liu ◽  
Fu Chen
Keyword(s):  
Pressure Loss ◽  
Total Pressure ◽  
Numerical Study ◽  
Vortex Generator ◽  
Total Pressure Loss ◽  
Experimental Result ◽  
Compressor Cascade ◽  
Design Point ◽  
Vortex Generator Jets ◽  
End Wall

This paper presents a numerical and experimental result of the end-wall vortex generator jets for controlling corner separation and enhancing the aerodynamic performance in a high subsonic (Ma = 0.7) compressor cascade. The experiments were carried out on a compressor cascade at design point ( i = 0°) and off-design points ( i = −2°, 2°, and 4°). At design point, the total pressure loss coefficient could be reduced up to 12.1%.With the increase in the incidence, the control effect is enhanced first and then reduced. The maximum total pressure loss reduction is up to 14.6% when the incidence is 2°. The numerical study is further conducted to analyze the flow pattern and the vortex structure. The jet vortex is formed downstream of the jet hole using the vortex generator jets, the cross flow on the end wall is also suppressed.

Experimental Investigation of Flow Control in Compressor Cascades

2006 ◽  
Author(s):  
A. Hergt ◽  
R. Meyer ◽  
K. Engel
Keyword(s):  
Boundary Layer ◽  
Flow Control ◽  
Total Pressure ◽  
Control Device ◽  
Vortex Generators ◽  
Test Facility ◽  
Compressor Cascade ◽  
Corner Separation ◽  
Pressure Losses ◽  
Flow Control Device

A large part of the total pressure losses in a compressor stage is caused by secondary flow effects like the separation between the wall and the vane i.e., a corner separation. An experimental and numerical investigation in a highly loaded compressor cascade was performed to understand the fluid mechanic mechanism of this corner separation in order to control it by using vortex generators. The experiments were carried out with a compressor cascade at a high-speed test facility at DLR in Berlin. The cascade consisted of five vanes and their profiles represent the cut at 10% of span distance from the hub of the stator vanes of a single stage axial compressor. The experiments were accomplished at Reynolds numbers up to Re = 0.6 × 106 (based on 40 mm chord) and Mach numbers up to M = 0.7. To measure the total pressure losses of the cascade (caused by the corner separation) a wake rake was used. It consisted of 26 pitot probes to measure the total pressure distribution of the outflow and 4 Conrad probes to determine the outflow angles. To detect the separation area on the vane, a flow visualisation technique was used. In addition to the experiments, numerical computations were carried out with the URANS TRACE, which has been developed at DLR for the simulation of steady and unsteady turbomachinery flow. The computations were performed with identical geometrical conditions as in the experiments, including the measured inflow boundary layer conditions at the side walls. The experiments were performed with the aim of controlling the corner separation. In this case, vortex generators as a passive flow control device were used. The vortex generators were attached at the surface of the suction side of the vanes. The flow control device is producing a strong vortex, which enhances the mixing between the main flow and the retarded boundary layer at the side wall. Thus, the corner separation is reduced on the vanes. The experiments were carried out at the peak efficiency (design point) of the cascade in order to optimize the design of the vortex generators for an application in turbomachines.

End-Wall Film Cooling Through Fan-Shaped Holes With Different Area Ratios

2006 ◽  
Vol 129 (2) ◽  
pp. 212-220 ◽  
Author(s):  
Giovanna Barigozzi ◽  
Giuseppe Franchini ◽  
Antonio Perdichizzi
Keyword(s):  
Secondary Flow ◽  
Mass Flow ◽  
Film Cooling ◽  
Three Dimensional ◽  
Wide Band ◽  
Lateral Spreading ◽  
Area Ratio ◽  
Adiabatic Effectiveness ◽  
Flow Effects ◽  
End Wall

The present paper reports on the aerothermal performance of a nozzle vane cascade, with film-cooled end walls. The coolant is injected through four rows of cylindrical holes with conical expanded exits. Two end-wall geometries with different area ratios have been compared. Tests have been carried out at low speed (M=0.2), with coolant to mainstream mass flow ratio varied in the range 0.5–2.5%. Secondary flow assessment has been performed through three-dimensional (3D) aerodynamic measurements, by means of a miniaturized five-hole probe. Adiabatic effectiveness distributions have been determined by using the wide-band thermochromic liquid crystals technique. For both configurations and for all the blowing conditions, the coolant share among the four rows has been determined. The aerothermal performances of the cooled vane have been analyzed on the basis of secondary flow effects and laterally averaged effectiveness distributions; this analysis was carried out for different coolant mass flow ratios. It was found that the smaller area ratio provides better results in terms of 3D losses and secondary flow effects; the reason is that the higher momentum of the coolant flow is going to better reduce the secondary flow development. The increase of the fan-shaped hole area ratio gives rise to a better coolant lateral spreading, but appreciable improvements of the adiabatic effectiveness were detected only in some regions and for large injection rates.

Unsteady Pressure Investigations of Corner Separated Flow in a Linear Compressor Cascade

2015 ◽  
Author(s):  
Gherardo Zambonini ◽  
Xavier Ottavy
Keyword(s):  
Transfer Functions ◽  
Leading Edge ◽  
Positive Pressure ◽  
Compressor Cascade ◽  
Suction Surface ◽  
Linear Compressor ◽  
Corner Separation ◽  
Unsteady Pressure ◽  
Linear Compressor Cascade ◽  
End Wall

The aim of this work is to present detailed unsteady pressure measurements of three-dimensional flow field in a NACA 65 linear compressor cascade. Chord-based Reynolds number of 382000 and incidence angle of 4 degrees were chosen as target configuration of the rig, which clearly presents the corner separation phenomenon at the juncture of the blade suction side and the end-wall. Concerning the experiments, a characterization of the mean and fluctuating component of wall static pressure on the surface of a specially developed blade is achieved at first. This fluctuating component is investigated utilizing nineteen high sensitivity condenser microphones plugged into blade cavities which have been carefully calibrated. Transfer functions obtained by calibration are exploited to reconstruct the time-dependent pressure signal and finally statistics, conditional ensemble averages, coherence and spectra analyses of fluctuations are presented in order to investigate the unsteady characteristics of the corner separation. High values of root mean square are individuated near the leading edge and in the separation region on the suction surface of the blade. Skewness and kurtosis show an intermittent behavior of the separation onset, which moves upstream and downstream on the suction surface. This intermittency of the separation line is probably linked with the existence of a bimodal behavior of the size of the corner separation. The analyses of coherence and conditional ensemble average between the signals at the leading edge and at the onset of the separation suggest a critical influence of angle and velocity of the incoming end-wall boundary layer on the positive pressure signatures of the shear layer, which characterize the inception of the separation.

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