piv measurements and computational study around a 5-inch ducted fan for vtol uav ali akturk, akamol...

PIV Measurements and Computational Study PIV Measurements and Computational Study

around a 5-Inch Ducted Fan for VTOL UAVaround a 5-Inch Ducted Fan for VTOL UAV

Ali Akturk , Akamol Shavalikul

&

Cengiz Camci

01.05.2009

VLRCOE (Vertical Research Lift Center of Excellence)Turbomachinery Aero-Heat Transfer Laboratory

Department of Aerospace EngineeringThe Pennsylvania State University

Presented at the 2009 47th AIAA Aerospace Sciences Meeting

Overview

Turbomachinery Aero-Heat Transfer Laboratory

• INTRODUCTION

• OBJECTIVES

• DUCTED FAN MODEL • EXPERIMENTAL SETUP • PARTICLE IMAGE VELOCIMETER (PIV)

• EXPERIMENTAL RESULTS AND DISCUSSION

• THE SPECIFIC ACTUATOR DISK BASED FAN MODEL

• SUMMARY AND CONCLUSIONS

Introduction


NAME OF THE VEHICLE Diameter (inch) Height (inch) Weight (lbs) E. Power (hp)

Hiller flying platform 96 84 180

AROD 52

Skorsky Cypher 74.4 24 240 50

Mass Helispy 11 27 6

Istar 9 12 4 1.2

Dragon-Stalker 200 17

BAE IAV2 22 60 25

Golden Eye- 50 27.5 22.04

Honeywell MAV 13 16 4.2

Univ. of Rome UAV 39.3 200.6 42

DUCTED FAN VTOL VEHICLES

Introduction


• There has been many studies to quantify the flow field properties around ducted fans.

• Martin and Tung tested a ducted fan in hover condition and in forward flight with different crosswind velocities. They have measured aerodynamic loads and performed hot-wire velocity surveys at inner and outer surface of the duct and across the downstream wake .

• Fleming, Jones and Lusardi conduct wind tunnel experiments and computational studies on 12” ducted fan. They have concentrated on ducted fan performance in forward flight.

Introduction


• Graf, Fleming and Wings improved ducted fan forward flight performance with new design leading edge geometry which has been determined to be the significant factor in offsetting the effects of the adverse aerodynamic characteristics.

• Lind, Nathman and Gilchrist carried out a computational study using panel method.

Introduction


•He and Xin developed the ducted fan models based on a nonuniform and unsteady ring vortex formulation for duct and lade element model for fan.

• Zhao and Bil proposed CFD simulation to design and analyze an aerodynamic model of a ducted fan UAV in preliminary design phase with different speeds and angles of attack.

Objectives


• The main aim is to analyze complicated flow field around the ducted fan in hover and horizontal flight conditions is investigated .

• A ducted fan that has a 5” diameter is used for analysis.

• Quantification of velocity field at the inlet and exit of the ducted fan by Planar PIV measurements.

• To generate an efficient definition of fan boundary condition using for actuator disk model.

Ducted Fan Model


Rotor hub diameter 52 mm

Rotor tip diameter 120

Duct inner diameter 126

Blade height h 34

Tip clearance t/h 8.7 %

Max. blade thickness @ tip 1.5

Tailcone diameter 52

Tailcone length 105

HUB MIDSPAN

TIP

Blade inlet angle 1 60 o 40 o 30 o

Blade exit angle 2 30 o 45 o 60 o

Blade chord mm 32 30 28

Design rpm N 13000

Tip Mach number 0.28

Reynolds number(mid-span)

7x104

rtip / RT

Wmc /

Experimental Setup


Cross Wind Blower

NOT TO SCALE

Particle Image Velocimeter (PIV)


PIV Camera

Laser Beam Source

PIV Camera

Calibration plate

Fan Blades

Basic steps of PIV experimental procedure :

• Flow is seeded.• The flow region of interest is illuminated.• Scattering light from the particles forming the speckle images is

recorded by cameras. • Recordings are analyzed by means of correlation software.

In our experiments:

• 80C60 HiSense PIV/PLIF camera

• Nikon Micro-Nikkor 60/2.8 objective

• Double cavity frequency doubled pulsating Nd:YAG laser

• Seeding particles has diameter of 0.25-60 m.



Fan Blades

CCD Camera Laser Head

Laser Sheet

Procedure used in our system :

• Aligning camera and laser sheet.

• The image pairs of PIV domains are recorded.

• The image maps are divided into 32 x 32 pixel interrogation areas and 25% overlapping is used which generated 1748 vectors.

• All the image pairs are adaptive correlated, moving average validated and then ensemble averaged to obtain true mean flow.

• Measurement domains size : [156 mm x 96 mm]



PIV Camera

Fan Blades

• The ensemble size is of critical importance in achieving statistically stable mean velocity distributions in SPIV data reduction process.



PIV Camera



PIV Camera

Fan Blades

Ensemble size of 400 is optimal in achieving a statistically stable average in the current set of experiments.

Experimental Results


Fan Blades

AXIAL VELOCITY CONTOURS

9000 Rpm & 15000 Rpm

@ Hover Condition



Fan Blades

9000 Rpm

9000 Rpm 15000 Rpm



Fan Blades

RADIAL VELOCITY CONTOURS

9000 Rpm & 15000 Rpm

@ Forward Flight

LEADINGSIDE

TRAILINGSIDE



9000 Rpm

9000 Rpm 15000 Rpm

LEADINGSIDE

TRAILINGSIDE

LEADINGSIDE

TRAILINGSIDE

6.05 m/s



Fan Blades

VELOCITY MAGNITUDE CONTOURS

&

STREAMLINES

9000 Rpm

@ Hover and Forward Flight



Fan Blades

9000 Rpm

LEADINGSIDE

TRAILINGSIDE

6.05 m/s

Hover Forward Flight



Fan Blades

9000 Rpm

Duct Boundary

Drop in axial velocity due to lip separation



Fan Blades

VELOCITY MAGNITUDE CONTOURS

&

STREAMLINES

15000 Rpm

@ Hover and Forward Flight



LEADINGSIDE

TRAILINGSIDE

6.05 m/s

Specific actuator disk based fan model


PIV Camera

Fan Blades

• Incompressible Navier Stokes equations are solved.

•Unstructured computational mesh.

• 700000 tetrahedral cells.

• Symmetry boundary condition is applied at the side surfaces.

• Pressure inlet and outlet boundary conditions are applied at top and bottom.

•Pressure jump boundary condition is applied at the fan surface.

Fan Surface

PRESSURE OUTLET(atmospheric static pressure specified)

PRESSURE INLET(atmospheric static pressure specified)


PIV Camera

)]2/()2/[(

)]2/()2/[(

0 andr U where)()(

221

1

11

22

2

22

2211

222

11212

Ucc

pec

pe

Ucchch

cccUhh oo



PIV Camera

)(2

1

22

1

rUwhere)(1

21

22212

2

21

1

22

2

12012

ccUCPPP

UCc

Pc

P

CCUPPo



Measured and computed axial velocity component @ the inlet of the ducted fan for 9000Rpm Hover condition


Summary


• Experimental and computational investigation around 5 inch diameter ducted fan for V/STOL UAV.

• Planar PIV system used to measure velocity field around the ducted fan.

• Axial and radial velocity components at the inlet/exit region of the ducted fan were measured in hover and horizontal flight at 6m/s.

• Computational study based on solving incompressible Navier-Stokes equations was carried out.

• The specific actuator disk based fan-model used for pressure jump across the fan rotor.

Conclusions


• The performance of the ducted fan was highly affected from the crosswind velocity.

• That separation bubble has proven to affect the exit flow of the fan rotor.

• Non-uniformities introduced to the inlet and exit flow by the effect of crosswind.

Conclusions


• Increase in rotational speed enhances the performance at 9000 Rpm and15000 Rpm in hover condition.

• Increase of rotational speed reduced effect of separation bubble.

• The specific actuator disk based fan model was able to predict inlet flow velocity distribution well at 9000 Rpm.

BACK –UP SLIDES

Computational Results


Phase Locked Approached of PIV Measurements(Image recorded with digital camera on full laser power)

r>0 r<0

PIV to Pitot Probe Comparison


“Vertical” test arrangement

Comparison between PIV and Pitot probe results

W/o cylinder w/ cylinder

PIV Validation with Pitot probe results

Ensemble effect (2)

W/o cylinder w/ cylinder

2,1000,

1

)(1

njj

N

jitotal

i

NError

Definition:

Figure 24: Comparison of velocity profiles

Out-of –plane component in-plane component axial (z-direction)

piv measurements and computational study around a 5-inch ducted fan for vtol uav ali akturk, akamol...

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