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Research Papers: Gas Turbines: Aircraft Engine

Effect of Aft Rotor on the Inter-Rotor Flow of an Open Rotor Propulsion System

[+] Author and Article Information
Paul E. Slaboch

Mem. ASME
Mechanical Engineering Department,
Saint Martin's University,
Cebula Hall 103D,
5000 Abbey Way SE,
Lacey, WA 98503
e-mail: pslaboch@stmartin.edu

David B. Stephens

Mem. ASME
NASA Glenn Research Center,
MS 54/3,
21000 Brookpark Road,
Cleveland, OH 44135
e-mail: david.stephens@nasa.gov

Dale E. Van Zante

Mem. ASME
NASA Glenn Research Center,
MS 54/3,
21000 Brookpark Road,
Cleveland, OH 44135
e-mail: dale.e.vanzante@nasa.gov

Mark P. Wernet

NASA Glenn Research Center,
MS 77/2,
21000 Brookpark Road,
Cleveland, OH 44135
e-mail: mark.p.wernet@nasa.gov

1Corresponding author.

Contributed by the Aircraft Engine Committee of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received June 29, 2016; final manuscript received July 6, 2016; published online October 18, 2016. Editor: David Wisler.This work is in part a work of the U.S. Government. ASME disclaims all interest in the U.S. Government's contributions.

J. Eng. Gas Turbines Power 139(4), 041202 (Oct 18, 2016) (10 pages) Paper No: GTP-16-1292; doi: 10.1115/1.4034356 History: Received June 29, 2016; Revised July 06, 2016

The effects of the aft rotor on the inter-rotor flow field of an open rotor propulsion rig (ORPR) were examined. A particle image velocimetry (PIV) dataset that was acquired phase locked to the front rotor position has been phase averaged based on the relative phase angle between the forward and aft rotors. The aft rotor phase was determined by feature tracking in raw PIV images through an image-processing algorithm. The effects of the aft rotor potential field on the inter-rotor flow were analyzed and shown to be in reasonably good agreement with computational fluid dynamics (CFD) simulations. The aft rotor position was shown to have a significant upstream effect, with implications for front rotor interaction noise. It was found that the aft rotor had no substantial effect on the position of the forward rotor tip vortex but did have a small effect on the circulation strength of the vortex when the rotors were highly loaded.

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References

Figures

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Fig. 1

Photo of the ORPR in the 9 × 15 LSWT at NASA GRC

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Fig. 2

Schematic of extent of PIV data acquisition on ORPR. Positive z-direction is upstream. The 30 planes of PIV data are stacked in the x-direction. Flow is from left to right.

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Fig. 3

Representative raw PIV image showing masked laser sheet and indirect illumination of the aft rotor. Vertical line indicates locus of possible locations of minimum for one blade passage. Horizontal arrow indicates location of local minimum identified by the image-processing algorithm. The light sheet is the brighter portion on the left, illuminated from above. Flow is from left to right.

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Fig. 4

Representative histogram showing number of vector maps per bin used to ensemble average the data based on aft rotor phase angle. Example shown is from test case 1, plane 9 from the hub.

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Fig. 5

Contours and isosurfaces of velocity magnitude for nonphase-averaged dataset, test case 1. Isosurfaces are at UM/V1,tip = 0.35 and 0.56. Plane is located at z/R1 = −0.4 behind forward rotor.

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Fig. 6

Contours and isosurfaces of velocity magnitude for the aft rotor phase-averaged test case 1 at five different aft rotor phase angles. Isosurfaces are at UM/V1,tip = 0.35 and 0.56.

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Fig. 7

Effect of aft rotor phase on inter-rotor velocity magnitude, from test case 1. Flow is from left to right of image. The forward rotor is moving top to bottom, and the aft rotor is moving bottom to top. Left image is of opposite phase from right image. Dashed line at Y/R1 = −0.183 shows data extraction line for Figs. 810.

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Fig. 8

Streamwise velocity variation with aft rotor position. Values extracted from a line at Y/R1 = −0.183 from Fig. 7, at all ten aft rotor phases.

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Fig. 9

Radial velocity variation with aft rotor position. Values extracted from a line at Y/R1 = −0.183 from Fig. 7, at all ten aft rotor phases.

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Fig. 10

Tangential velocity variation with aft rotor position. Values extracted from a line at Y/R1 = −0.183 from Fig. 7, at all ten aft rotor phases.

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Fig. 11

Decay of aft rotor potential field as quantified by fluctuations in Uw. Aft rotor leading edge is at z/R1 = −0.57.

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Fig. 12

Inter-rotor velocity magnitude, from test case 5. Flow is from left to right of image. The forward rotor is moving top to bottom, and the aft rotor is moving bottom to top. Dashed line at Y/R1 = −0.01 shows data for line plots given in Figs. 1315.

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Fig. 13

Streamwise velocity variation with aft rotor position. Values extracted from a line at Y/R1 = −0.01 from Fig. 12, at all ten aft rotor phases.

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Fig. 14

Radial velocity variation with aft rotor position. Values extracted from a line at Y/R1 = −0.01 from Fig. 12, at all ten aft rotor phases.

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Fig. 15

Tangential velocity variation with aft rotor position. Values extracted from a line at Y/R1 = −0.01 from Fig. 12, at all ten aft rotor phases.

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Fig. 16

Contours of axial velocity at a plane 2.25 in. upstream of the aft rotor pitch change axis. Figure taken from Ref. [12]. Dashed line of constant radius shows location of data plotted in Fig. 17.

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Fig. 17

Axial velocity in a plane 5.70 cm upstream of the aft rotor pitch change axis (z/R1 = −0.4). (a) Comparison of measured to predicted axial velocity along same constant radius line. Image from Ref. [12]. (b) Dashed lines are axial velocity along constant radius at three different aft rotor phase angles. Black line is mean wake across all the phase angles. (a) CFD-computed instantaneous wakes and (b) PIV measured phase-averaged wakes.

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Fig. 18

Example of vortex location determination method

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Fig. 19

Contours of axial vorticity at a plane z/R1 = 0.44, or 5.6 cm (2.25 in.) upstream of the aft rotor pitch change axis. Dashed line shows bounding box for circulation calculation.

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Fig. 20

Size and position of the forward rotor tip vortex for (a) high RPM case and (b) low RPM case versus relative aft rotor phase angle. Solid lines represent forward rotor at absolute phase of 0 deg, and dashed lines represent forward rotor absolute phase of approximately 15 deg. (a) High RPM, test cases 1 and 2 and (b) low RPM, test cases 3 and 4.

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