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PIV Measurements and Computational Study around 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 Engineering

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slide1

PIV Measurements and Computational Study

around 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 Engineering

The Pennsylvania State University

Presented at the 2009 47th AIAA Aerospace Sciences Meeting

slide2

Overview

  • 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

Turbomachinery Aero-Heat Transfer Laboratory

slide3

Introduction

DUCTED FAN VTOL VEHICLES

Turbomachinery Aero-Heat Transfer Laboratory

slide4

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.

Turbomachinery Aero-Heat Transfer Laboratory

slide5

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.

Turbomachinery Aero-Heat Transfer Laboratory

slide6

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.

Turbomachinery Aero-Heat Transfer Laboratory

slide7

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.

Turbomachinery Aero-Heat Transfer Laboratory

slide8

Ducted Fan Model

Turbomachinery Aero-Heat Transfer Laboratory

slide9

Experimental Setup

Cross Wind Blower

NOT TO SCALE

Turbomachinery Aero-Heat Transfer Laboratory

slide10

PIV Camera

Fan Blades

Laser Beam Source

PIV Camera

Calibration plate

Particle Image Velocimeter (PIV)

  • 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.

Turbomachinery Aero-Heat Transfer Laboratory

slide11

Fan Blades

Particle Image Velocimeter (PIV)

  • 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.

Laser Sheet

CCD Camera

Laser Head

Turbomachinery Aero-Heat Transfer Laboratory

slide12

PIV Camera

Fan Blades

Particle Image Velocimeter (PIV)

  • 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]

Turbomachinery Aero-Heat Transfer Laboratory

slide13

PIV Camera

Particle Image Velocimeter (PIV)

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

Turbomachinery Aero-Heat Transfer Laboratory

slide14

PIV Camera

Fan Blades

Particle Image Velocimeter (PIV)

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

Turbomachinery Aero-Heat Transfer Laboratory

slide15

Fan Blades

Experimental Results

AXIAL VELOCITY CONTOURS

9000 Rpm & 15000 Rpm

@ Hover Condition

Turbomachinery Aero-Heat Transfer Laboratory

slide16

Fan Blades

Experimental Results

9000 Rpm

9000 Rpm

15000 Rpm

Turbomachinery Aero-Heat Transfer Laboratory

slide17

Fan Blades

Experimental Results

RADIAL VELOCITY CONTOURS

9000 Rpm & 15000 Rpm

@ Forward Flight

LEADING

SIDE

TRAILING

SIDE

Turbomachinery Aero-Heat Transfer Laboratory

slide18

Experimental Results

6.05m/s

9000 Rpm

LEADING

SIDE

LEADING

SIDE

TRAILING

SIDE

TRAILING

SIDE

9000 Rpm

15000 Rpm

Turbomachinery Aero-Heat Transfer Laboratory

slide19

Fan Blades

Experimental Results

VELOCITY MAGNITUDE CONTOURS

&

STREAMLINES

9000 Rpm

@ Hover and Forward Flight

Turbomachinery Aero-Heat Transfer Laboratory

slide20

Fan Blades

Experimental Results

6.05m/s

9000 Rpm

LEADING

SIDE

TRAILING

SIDE

Hover

Forward Flight

Turbomachinery Aero-Heat Transfer Laboratory

slide21

Fan Blades

Experimental Results

Duct Boundary

9000 Rpm

Drop in axial velocity due to lip separation

Turbomachinery Aero-Heat Transfer Laboratory

slide22

Fan Blades

Experimental Results

VELOCITY MAGNITUDE CONTOURS

&

STREAMLINES

15000 Rpm

@ Hover and Forward Flight

Turbomachinery Aero-Heat Transfer Laboratory

slide23

Experimental Results

6.05m/s

LEADING

SIDE

TRAILING

SIDE

Turbomachinery Aero-Heat Transfer Laboratory

slide24

PIV Camera

Fan Blades

Specific actuator disk based fan model

  • 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.

PRESSURE INLET

(atmospheric static pressure specified)

Fan Surface

PRESSURE OUTLET

(atmospheric static pressure specified)

Turbomachinery Aero-Heat Transfer Laboratory

slide25

PIV Camera

Specific actuator disk based fan model

Turbomachinery Aero-Heat Transfer Laboratory

slide26

PIV Camera

Specific actuator disk based fan model

Turbomachinery Aero-Heat Transfer Laboratory

slide27

Specific actuator disk based fan model

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

Turbomachinery Aero-Heat Transfer Laboratory

slide28

Summary

  • Experimental and computational investigation around 5 inch diameter ducted fan for V/STOL UAV.
  • Planar PIV system used to measure velocity field aroundthe 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.

Turbomachinery Aero-Heat Transfer Laboratory

slide29

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.

Turbomachinery Aero-Heat Transfer Laboratory

slide30

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.

Turbomachinery Aero-Heat Transfer Laboratory

slide33

Computational Results

r>0

r<0

Phase Locked Approached of PIV Measurements

(Image recorded with digital camera on full laser power)

Turbomachinery Aero-Heat Transfer Laboratory

slide34

PIV to Pitot Probe Comparison

“Vertical” test arrangement

Turbomachinery Aero-Heat Transfer Laboratory

ensemble effect 2
Ensemble effect (2)

Definition:

W/o cylinder w/ cylinder

figure 24 comparison of velocity profiles
Figure 24: Comparison of velocity profiles

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