Research Papers

The Influence of an Upstream Pylon on Open Rotor Aerodynamics at Angle of Attack

[+] Author and Article Information
Nishad G. Sohoni

Whittle Laboratory,
University of Cambridge,
Cambridge CB3 0DY, UK

Cesare A. Hall

Whittle Laboratory,
University of Cambridge,
Cambridge CB3 0DY, UK
e-mail: cah1003@cam.ac.uk

Anthony B. Parry

Rolls-Royce plc,
P.O. Box 31,
Derby DE24 8BJ, UK

1Corresponding author.

Manuscript received March 6, 2018; final manuscript received July 19, 2018; published online January 16, 2019. Assoc. Editor: Coutier-Delgosha Olivier.

J. Turbomach 141(2), 021006 (Jan 16, 2019) (9 pages) Paper No: TURBO-18-1052; doi: 10.1115/1.4041082 History: Received March 06, 2018; Revised July 19, 2018

The aerodynamic impact of installing a horizontal pylon in front of a contra-rotating open rotor engine, at take-off, was studied. The unsteady interactions of the pylon's wake and potential field with the rotor blades were predicted by full-annulus URANS CFD calculations at 0 deg and 12 deg angle of attack (AoA). Two pylon configurations were studied: one where the front rotor blades move down behind the pylon (DBP), and one where they move up behind the pylon (UBP). When operating at 12 deg AoA, the UBP orientation was shown to reduce the rear rotor tip vortex sizes and separated flow regions, whereas the front rotor wake and vortex sizes were increased. In contrast, the DBP orientation was found to reduce the incidence variations onto the front rotor, leading to smaller wakes and vortices. The engine flow was also time-averaged, and the variation in work done on average midspan streamlines was shown to depend strongly on variation in incidence, along with a smaller contribution related to change of radius.

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Fig. 1

Definition of AoA; and pylon orientation relative to front rotor rotation: DBP and UBP

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Fig. 2

Computational domains for simulation and postprocessing: (a) computational domain showing pylon, rotors, and block boundaries and (b) relative domains and radial clustering of absolute-frame mesh

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Fig. 3

Engine performance parameters

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Fig. 4

Variation of CT and CP around the annulus

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Fig. 5

Contours of time-averaged flow: (a) front rotor inlet αloc and (b) rear rotor inlet whirl, at 12 deg AoA

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Fig. 6

Contours of time-averaged entropy function at (a) front rotor exit, and (b) rear rotor exit, at 12 deg AoA

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Fig. 7

Contours of instantaneous entropy function at rotor exits, and virtual tufts on rotor suction surface, colored by Vx, at 12 deg AoA. Flow is into the page.

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Fig. 8

Front rotor tip vortex characterization: (a) radial and axial variation of front rotor tip vortex cores. Cuts for all cases were made at the same axial locations, at 12 deg AoA, but are staggered for clarity. Rear rotor stagger change axis is marked and (b) circumferential variation of (b1) radial location of vortex core, and (b2) vortex circulation, at x′ 0:14DF, for 12 deg AoA.

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Fig. 9

Annular variation of incidence, inlet Mach number, and ζ at midspan: (a) front rotor mid-span and (b) rear rotor mid-span

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Fig. 10

Work and incidence on time-averaged streamlines, at 12 deg AoA: (a) streamlines at front rotor mid-span and (b) streamlines at rear rotor mid-span

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Fig. 11

Effect of change of radius on front rotor work: (a) components of front rotor work and (b) annular variation of Δθ (solid lines) and Δr (dashed lines), front rotor mid-span

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Fig. 12

Effect of change of radius on rear rotor work: (a) components of rear rotor work and (b) annular variation of Δθ (solid lines) and Δr (dashed lines), rearrotor mid-span

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Fig. 13

Fast Fourier transform of static pressure at front rotor midspan for 0 deg and 12 deg AoA, r/RF = 0.75, x/c = 0.1

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Fig. 14

Fast Fourier transform of static pressure at rear rotor midspan for 0 deg and 12 deg AoA, r/RR = 0.75, x/c = 0.1



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