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Research Papers

Tip Clearance Investigation of a Ducted Fan Used in VTOL Unmanned Aerial Vehicles—Part I: Baseline Experiments and Computational Validation

[+] Author and Article Information
Ali Akturk

e-mail: akturkali@gmail.com

Cengiz Camci

Professor
e-mail: cxc11@psu.edu
Turbomachinery Aero-Heat Transfer Laboratory,
Department of Aerospace Engineering,
Pennsylvania State University,
University Park, PA 16802

1Currently working at Siemens Energy Inc.

2Corresponding author.

Contributed by the International Gas Turbine Institute (IGTI) of ASME for publication in the JOURNAL OF TURBOMACHINERY. Manuscript received November 5, 2012; final manuscript received December 8, 2012; published online September 26, 2013. Editor: David Wisler.

J. Turbomach 136(2), 021004 (Sep 26, 2013) (10 pages) Paper No: TURBO-12-1212; doi: 10.1115/1.4023468 History: Received November 05, 2012; Revised December 08, 2012

Ducted fans that are popular choices in vertical take-off and landing (VTOL) unmanned aerial vehicles (UAV) offer a higher static thrust/power ratio for a given diameter than open propellers. Although ducted fans provide high performance in many VTOL applications, there are still unresolved problems associated with these systems. Fan rotor tip leakage flow is a significant source of aerodynamic loss for ducted fan VTOL UAVs and adversely affects the general aerodynamic performance of these vehicles. The present study utilized experimental and computational techniques in a 559 mm diameter ducted fan test system that has been custom designed and manufactured. The experimental investigation consisted of total pressure measurements using Kiel total pressure probes and real time six-component force and torque measurements. The computational technique used in this study included a 3D Reynolds-averaged Navier–Stokes (RANS) based computational fluid dynamics model of the ducted fan test system. Reynolds-averaged Navier–Stokes simulations of the flow around the rotor blades and duct geometry in the rotating frame of reference provided a comprehensive description of the tip leakage and passage flow. The experimental and computational analysis performed for various tip clearances were utilized in understanding the effect of the tip leakage flow on the aerodynamic performance of ducted fans used in VTOL UAVs. The aerodynamic measurements and results of the RANS simulations showed good agreement, especially near the tip region.

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References

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Figures

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Fig. 1

Schematic and instrumentation of the 559 mm diameter ducted fan system

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Fig. 2

Blade profiles at various radial stations

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Fig. 3

Yaw angle in the absolute frame calculated from the initial computations

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Fig. 4

Grid independence study

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Fig. 5

Medium size computational mesh used in the computations

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Fig. 6

Thrust coefficient versus the fan rotational speed during hover (baseline rotor)

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Fig. 7

Thrust coefficient versus the power coefficient for the baseline rotor

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Fig. 8

Figure of merit (FM) versus the fan rotational speed for the baseline rotor

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Fig. 9

Total pressure measured downstream of the rotor at 2400 rpm for the baseline rotor

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Fig. 10

Total pressure coefficient comparison for experimental and computational analysis at 2400 rpm for the baseline rotor with (a) 1.71%, (b) 3.04%, and (c) 5.17% tip clearances

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Fig. 11

Comparison of the computed and measured thrust for 1.71% and 3.04% tip clearances for the baseline rotor

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Fig. 12

Streamlines around the baseline rotor blade with a 1.71% tip clearance and the rotor hub at 2400 rpm

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Fig. 13

Relative total pressure distribution at the rotor exit plane for the baseline blade with a 1.71% tip clearance

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Fig. 14

Streamlines around the baseline rotor blade with a 3.04% tip clearance and the rotor hub at 2400 rpm

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Fig. 15

Relative total pressure distribution at the rotor exit plane for the baseline blade with a 3.04% tip clearance

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Fig. 16

Axial velocity comparison at the rotor exit plane for the baseline blade with (a) 1.71%, and (b) 3.04% tip clearances

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Fig. 17

Relative total pressure comparison at the rotor exit plane for the baseline blades with 1.71%, 3.04%, and 5.17% tip clearances

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