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Research Papers: Flows in Complex Systems

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

[+] Author and Article Information
Mahesh K. Varpe

Department of Aerospace Engineering,
Indian Institute of Technology, Bombay,
Mumbai 400 076, India
e-mail: maheshvarpe@aero.iitb.ac.in

A. M. Pradeep

Department of Aerospace Engineering,
Indian Institute of Technology, Bombay,
Mumbai 400 076, India
e-mail: ampradeep@aero.iitb.ac.in

1Corresponding author.

Contributed by the Fluids Engineering Division of ASME for publication in the JOURNAL OF FLUIDS ENGINEERING. Manuscript received July 14, 2014; final manuscript received October 23, 2014; published online January 20, 2015. Assoc. Editor: Frank C. Visser.

J. Fluids Eng 137(5), 051101 (May 01, 2015) (15 pages) Paper No: FE-14-1378; doi: 10.1115/1.4028996 History: Received July 14, 2014; Revised October 23, 2014; Online January 20, 2015

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.

Copyright © 2015 by ASME
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References

Figures

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Fig. 1

Planar distribution of control points, marked as “+,” on the hub (endwall) with the wake location

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Fig. 2

Schematic representation of evolutionary algorithm

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Fig. 3

One point crossover between the parent chromosomes

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Fig. 4

Multiblock structured mesh with the O grid around the airfoil and triangular prism mesh in the tip region only

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Fig. 5

Comparison of the static pressure coefficient on the blade surface between experiment and CFD, at midspan and close to the tip

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Fig. 6

Total pressure coefficient along the span in the wake region, between experiment and CFD

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Fig. 7

Height contours of the optimum hub

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Fig. 8

Static pressure coefficient on the hub

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Fig. 10

Static pressure coefficient on the blade surface at midspan, close to hub, and tip

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Fig. 11

Contours of static pressure coefficient on blade surface for planar and optimized hub

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Fig. 12

SFL on blade surface

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Fig. 13

Contours of total pressure coefficient in the wake region for axisymmetric and profiled hub

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Fig. 14

Contours of vorticity along the reference flow angle in the wake region

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Fig. 15

Pitchwise mass averaged endwall loss, SKE, and flow deviation along the span, in the wake region

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Fig. 16

Contours of total pressure coefficient on the suction surface side of tip gap, with planar and optimized hub

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Fig. 17

Effect of hub contouring on the flow structure using streamlines

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Fig. 18

Coefficient of total pressure superimposed with secondary flow structure at different axial locations, near the tip in the flow passage

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Fig. 19

Coefficient of total pressure superimposed with secondary streamlines at different axial locations, near the hub in the flow passage

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Fig. 20

Mass averaged total pressure loss coefficient and yaw angle at different axial location

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Fig. 21

Static pressure coefficient in the wake region

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