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Research Papers

Effects of Area Ratio and Mean Rise Angle on the Aerodynamics of Interturbine Ducts

[+] Author and Article Information
Yanfeng Zhang

National Research Council of Canada,
1200 Montreal Road,
Ottawa, ON K1A 0R6, Canada

Shuzhen Hu, Xue-Feng Zhang

National Research Council of Canada,
1200 Montreal Road,
Ottawa, ON K1A 0R6, Canada

Ali Mahallati

National Research Council of Canada,
1200 Montreal Road,
Ottawa, ON K1A 0R6, Canada
e-mail: alimahallati@yahoo.ca

Edward Vlasic

Pratt & Whitney Canada,
1000 Boulevard Marie-Victorin,
Longueuil, QC J4G 1A1, Canada

1Corresponding author.

Contributed by the International Gas Turbine Institute (IGTI) of ASME for publication in the JOURNAL OF TURBOMACHINERY. Manuscript received July 4, 2016; final manuscript received December 17, 2017; published online August 28, 2018. Editor: Kenneth Hall.

J. Turbomach 140(9), 091006 (Aug 28, 2018) (11 pages) Paper No: TURBO-16-1144; doi: 10.1115/1.4039936 History: Received July 04, 2016; Revised December 17, 2017

This work, a continuation of a series of investigations on the aerodynamics of aggressive interturbine ducts (ITD), is aimed at providing detailed understanding of the flow physics and loss mechanisms in four different ITD geometries. A systematic experimental and computational study was carried out by varying duct outlet-to-inlet area ratios (ARs) and mean rise angles while keeping the duct length-to-inlet height ratio, Reynolds number, and inlet swirl constant in all four geometries. The flow structures within the ITDs were found to be dominated by the boundary layer separation and counter-rotating vortices in both the casing and hub regions. The duct mean rise angle determined the severity of adverse pressure gradient in the casing's first bend, whereas the duct AR mainly governed the second bend's static pressure rise. The combination of upstream wake flow and the first bend's adverse pressure gradient caused the boundary layer to separate and intensify the strength of counter-rotating vortices. At high mean rise angle, the separation became stronger at the casing's first bend and moved farther upstream. At high ARs, a two-dimensional separation appeared on the casing and resulted in increased loss. Pressure loss penalties increased significantly with increasing duct mean rise angle and AR.

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Figures

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Fig. 1

Annular diffuser performance chart [1]

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Fig. 2

Cutaway of the ITD test rig with the measurement locations and coordinate system: (a) turbulence grid, (b) swirl vane ring, (c) linear travel system, (d) rotatable ITD casing, and (e) ITD hub

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Fig. 3

Sketch of four ITD geometries with their AR distributions: (a) ITD-A, (b) ITD-B, (c) ITD-C, and (d) ITD-D

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Fig. 4

Computational mesh

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Fig. 5

Static pressure distribution in ITD-A

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Fig. 6

Measured vorticity and pressure fields in ITD-A

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Fig. 7

Flow visualization for ITD-A: (a) hub and (b) casing

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Fig. 8

Measured vorticity and pressure fields and casing flow visualization in ITD-B: (a) contours of resultant vorticity and total pressure coefficients and (b) casing flow visualization

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Fig. 9

Predicted static pressure distribution in ITD-A and ITD-B

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Fig. 10

Static pressure distribution in ITD-A and ITD-C

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Fig. 11

Measured vorticity and pressure fields and casing flow visualization in ITD-C: (a) contours of resultant vorticity and total pressure coefficients and (b) casing flow visualization

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Fig. 12

Predicted total pressure coefficients with and without upstream wakes in ITD-C: (a) upstream wakes considered and (b) wakes mixed-out at ITD

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Fig. 13

Static pressure distribution in ITD-A and ITD-D

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Fig. 14

Measured vorticity and pressure fields and casing flow visualization in ITD-D: (a) contours of resultant vorticity and total pressure coefficients and (b) casing flow visualization

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Fig. 15

Pitchwise mass-averaged total pressure coefficient at the duct outlet: (a) ITD-A, (b) ITD-B, (c) ITD-C, and (d) ITD-D

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Fig. 16

Measured and mixed-out loss coefficients

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