Research Papers

Design Optimization of Casing Grooves Using Zipper Layer Meshing

[+] Author and Article Information
Ning Qin

e-mail: n.qin@sheffield.ac.uk

Yibin Wang

Department of Mechanical Engineering,
University of Sheffield,
Mappin Street,
Sheffield S1 3JD,
South Yorkshire, UK

Shahrokh Shahpar

CFD Methods,
Design System Engineering,
Rolls Royce plc.,
Derby DE24 8BJ,
Derbyshire, UK

1Corresponding author.

Contributed by the International Gas Turbine Institute (IGTI) of ASME for publication in the JOURNAL OF TURBOMACHINERY. Manuscript received September 6, 2012; final manuscript received February 28, 2013; published online September 26, 2013. Assoc. Editor: Aspi Wadia.

J. Turbomach 136(3), 031002 (Sep 26, 2013) (12 pages) Paper No: TURBO-12-1185; doi: 10.1115/1.4024650 History: Received September 06, 2012; Revised February 28, 2013

A new algorithm, named the zipper layer method, has been developed to link multiblock meshes for groove-casing optimization applications. Numerical results for a turbomachinery rotor flow case are included to demonstrate the solution behavior across the zipper layer mesh. By using this new meshing methodology, the optimization of the casing groove geometries in relation to stall margin and efficiency of a transonic rotor is conducted. Six grooves are parameterized by their independent depths and a width to gap ratio. An advanced response surface method based on the Sobol design of experiment (DoE) and the Kriging response surface model (RSM) are used for the optimization. A leave-one-out cross-validation (LOOCV) method is used to calculate the quality of the response surface metric. The final optimized groove configuration is obtained through an optimization cycle using the Rolls-Royce SOPHY (SOFT-PADRAM-HYDRA) software (Shahpar, S., 2005, “SOPHY: An Integrated CFD Based Automatic Design Optimisation System,” Report No. ISABE-2005-1086), which not only improves the stall margin (SM) of the rotor but also maintains its peak efficiency.

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Fig. 1

Blade geometry details extracted from AGARD report [22]

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Fig. 2

Outline of NASA Rotor 37 mesh generated in PADRAM with 2.5 mm radius fillet at root of blade

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Fig. 4

Zipper layer mesh for NASA Rotor 37 with five grooves

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Fig. 5

A cut-through the zipper layer mesh in the middle of the blade

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Fig. 6

Original structured multiblock mesh

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Fig. 7

Mesh in Fig. 6 with zipper layer and new mesh generated in PADRAM on the casing side

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Fig. 8

Comparison of the total pressure ratio

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Fig. 9

Comparison of the total pressure ratios along the span

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Fig. 10

Numerical versus experimental data for validation of Rotor 37 flow

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Fig. 11

Comparison of convergence histories at peak efficiency condition (a) MB structured mesh (b) zipper layer mesh

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Fig. 12

Entropy and tip leakage vortex

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Fig. 13

Comparison of static pressure at 98% span

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Fig. 15

(a) Four groove (and two zero height groove) configuration from LPtau DoE; (b) five groove (and one zero height groove) configuration from LPtau DoE; (c) (d) six-groove configuration from LPtau DoE

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Fig. 16

Comparison of CFD data for groove casing treatment for Rotor 37 when compared to mesh without groove casing treatment

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Fig. 17

Optimized groove configuration based on optimum results from optimizer SOFT

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Fig. 18

Convergence histories of Rotor 37 for (a) flow residual (b) inlet mass flow rate

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Fig. 19

Pressure distribution on blade surface at 99% span at the stall point of the structured MB mesh with zipper layer with groove position indicated by black vertical lines

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Fig. 20

Relative Mach number contour near blade tip for the rotor (a) without casing treatment and (b) with casing treatment

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Fig. 21

The spill forward region is indicated by the red circle for the rotor by means of entropy contours (a) without casing treatment and (b) with casing treatment

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Fig. 22

Tip leakage vortex path indicated via the stream lines emanating from the blade tip leading edge shown with entropy contours slices at varying axial position along the blade: (a) without grooves (b) with grooves

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Fig. 23

Mass averaged Rotor 37 profiles at stall point of structured MB mesh with zipper layer, at station 4, for (a) total pressure ratio (b) adiabatic efficiency




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