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Research Papers

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

[+] Author and Article Information
Alexander Hergt

e-mail: alexander.hergt@dlr.de

Robert Meyer

German Aerospace Center (DLR),
Institute of Propulsion Technology,
51147 Cologne, Germany

Karl Engel

MTU Aero Engines,
GmbH Dachauer Str. 665,
80995 Munich, Germany

1Corresponding author. Present address: German Aerospace Center (DLR), Institute of Propulsion Technology, 51147 Cologne, Germany.

Contributed by the International Gas Turbine Institute (IGTI) of ASME for publication in the JOURNAL OF TURBOMACHINERY. Manuscript received July 11, 2011; final manuscript received November 25, 2011; published online November 8, 2012. Editor: David Wisler.

J. Turbomach 135(2), 021026 (Nov 08, 2012) (10 pages) Paper No: TURBO-11-1126; doi: 10.1115/1.4006605 History: Received July 11, 2011; Revised November 25, 2011

## Abstract

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.

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## Figures

Fig. 1

Fig. 2

Fig. 3

Fig. 4

Oil-flow visualization on endwall and blade suction side at ADP, M1 = 0.66

Fig. 5

Numerical streak lines on endwall and blade suction side at ADP, M1 = 0.66

Fig. 6

Sketch of flow field topology on endwall and blade suction side with critical points and highlighted separation lines (SL) and attachment lines (AL) at ADP, M1 = 0.66

Fig. 7

Numerically simulated secondary flow vectors at 0.78% of chord at ADP, M1 = 0.66 (viewing direction: upstream)

Fig. 8

Sketch of the resulting main vortex structure in the cascade at ADP, M1 = 0.66 (rotational sense of the vortices is valid for right side wall blade combination with upstream viewing direction)

Fig. 9

Total pressure loss distribution of the baseline cascade at MP2, ADP, M1 = 0.66

Fig. 10

Definition of vortex generator type

Fig. 11

Definition of vortex generator geometry

Fig. 12

Definition of vortex generator configurations and placement in the cascade (rotational sense of the vortices is valid for right side wall blade combination with upstream viewing direction)

Fig. 13

Oil-flow visualization of configuration A on endwall and blade suction side at ADP, M1 = 0.66

Fig. 14

Oil-flow visualization of baseline cascade and configuration A on blade suction side at ADP, M1 = 0.66

Fig. 15

Total pressure loss distribution of baseline cascade and configuration A at MP2, ADP, M1 = 0.66

Fig. 16

Oil-flow visualization of baseline cascade and configuration B on blade suction side at ADP, M1 = 0.66

Fig. 17

Total pressure loss distribution of baseline cascade and configuration B at MP2, ADP, M1 = 0.66

Fig. 18

Oil-flow visualization of baseline cascade and configuration A/B on blade suction side at ADP, M1 = 0.66

Fig. 19

Total pressure loss distribution of baseline cascade and configuration A/B at MP2, ADP, M1 = 0.66

Fig. 20

Oil-flow visualization of configuration C version 3 on endwall and blade suction side at ADP, M1 = 0.66

Fig. 21

Oil-flow visualization of baseline cascade and configuration C version 3 on blade suction side at ADP, M1 = 0.66

Fig. 22

Total pressure loss distribution of baseline cascade and configuration C version 3 at MP2, ADP, M1 = 0.66

Fig. 23

Mass-flow averaged spanwise pressure loss distribution of baseline cascade and configuration A, B, A/B, and C at ADP, M1 = 0.66

Fig. 24

Total pressure loss coefficient ω0 of the baseline cascade (top) and difference of the total pressure loss coefficient Δω between configuration A, B, A/B, and C and baseline normalized by baseline ω0 (bottom)

Fig. 25

Difference of the diffusion factor ΔDF at midspan between configuration A, B, A/B, and C and baseline normalized by baseline DF0

Fig. 26

Difference of the cascade deflection Δɛ at midspan between configuration A, B, A/B, and C and baseline normalized by baseline ɛ0

Fig. 27

Difference of the static pressure rise coefficient ΔΩ at midspan between configuration A, B, A/B, and C and baseline normalized by baseline Ω0

Fig. 28

Isentropic efficiency η at different engine speed n normalized by peak efficiency at 100% engine speed [31]

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