PIV Measurements and Computational Study around a 5-Inch Ducted Fan for VTOL UAV Ali Akturk, Akamol Shavalikul & Cengiz Camci VLRCOE (Vertical Research Lift Center of Excellence) Turbomachinery Aero-Heat Transfer Laboratory Department of Aerospace Engineering The Pennsylvania State University Presented at the th 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 Turbomachinery Aero-Heat Transfer Laboratory NAME OF THE VEHICLEDiameter (inch)Height (inch)Weight (lbs)E. Power (hp) Hiller flying platform AROD52 Skorsky Cypher Mass Helispy11276 Istar Dragon-Stalker20017 BAE IAV Golden Eye Honeywell MAV Univ. of Rome UAV DUCTED FAN VTOL VEHICLES

Introduction Turbomachinery Aero-Heat Transfer Laboratory 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 Turbomachinery Aero-Heat Transfer Laboratory 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 Turbomachinery Aero-Heat Transfer Laboratory 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 Turbomachinery Aero-Heat Transfer Laboratory 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 Turbomachinery Aero-Heat Transfer Laboratory Rotor hub diameter52 mm Rotor tip diameter120 Duct inner diameter126 Blade height h34 Tip clearance t/h8.7 % Max. blade tip1.5 Tailcone diameter52 Tailcone length105 HUBMID SPAN TIP Blade inlet angle  1 60 o 40 o 30 o Blade exit angle  2 30 o 45 o 60 o Blade chord mm Design rpm N13000 Tip Mach number0.28 Reynolds number (mid-span) 7x10 4

Experimental Setup Turbomachinery Aero-Heat Transfer Laboratory Cross Wind Blower NOT TO SCALE

Particle Image Velocimeter (PIV) Turbomachinery Aero-Heat Transfer Laboratory 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  m. Particle Image Velocimeter (PIV) Turbomachinery Aero-Heat Transfer Laboratory 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] Particle Image Velocimeter (PIV) Turbomachinery Aero-Heat Transfer Laboratory PIV Camera Fan Blades

The ensemble size is of critical importance in achieving statistically stable mean velocity distributions in SPIV data reduction process. Particle Image Velocimeter (PIV) Turbomachinery Aero-Heat Transfer Laboratory PIV Camera

Particle Image Velocimeter (PIV) Turbomachinery Aero-Heat Transfer Laboratory PIV Camera Fan Blades Ensemble size of 400 is optimal in achieving a statistically stable average in the current set of experiments.

Experimental Results Turbomachinery Aero-Heat Transfer Laboratory Fan Blades AXIAL VELOCITY CONTOURS 9000 Rpm & Hover Condition

Experimental Results Turbomachinery Aero-Heat Transfer Laboratory Fan Blades 9000 Rpm Rpm

Experimental Results Turbomachinery Aero-Heat Transfer Laboratory Fan Blades RADIAL VELOCITY CONTOURS 9000 Rpm & Forward Flight LEADING SIDE TRAILING SIDE

Experimental Results Turbomachinery Aero-Heat Transfer Laboratory 9000 Rpm Rpm LEADING SIDE TRAILING SIDE LEADING SIDE TRAILING SIDE 6.05 m/s

Experimental Results Turbomachinery Aero-Heat Transfer Laboratory Fan Blades VELOCITY MAGNITUDE CONTOURS & STREAMLINES 9000 Hover and Forward Flight

Experimental Results Turbomachinery Aero-Heat Transfer Laboratory Fan Blades 9000 Rpm LEADING SIDE TRAILING SIDE 6.05 m/s Hover Forward Flight

Experimental Results Turbomachinery Aero-Heat Transfer Laboratory Fan Blades 9000 Rpm Duct Boundary Drop in axial velocity due to lip separation

Experimental Results Turbomachinery Aero-Heat Transfer Laboratory Fan Blades VELOCITY MAGNITUDE CONTOURS & STREAMLINES Hover and Forward Flight

Experimental Results Turbomachinery Aero-Heat Transfer Laboratory LEADING SIDE TRAILING SIDE 6.05 m/s

Specific actuator disk based fan model Turbomachinery Aero-Heat Transfer Laboratory PIV Camera Fan Blades Incompressible Navier Stokes equations are solved. Unstructured computational mesh 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)

Turbomachinery Aero-Heat Transfer Laboratory PIV Camera Specific actuator disk based fan model

Turbomachinery Aero-Heat Transfer Laboratory PIV Camera Specific actuator disk based fan model

Turbomachinery Aero-Heat Transfer Laboratory Measured and computed axial velocity the inlet of the ducted fan for 9000Rpm Hover condition Specific actuator disk based fan model

Summary Turbomachinery Aero-Heat Transfer Laboratory 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 Turbomachinery Aero-Heat Transfer Laboratory 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 Turbomachinery Aero-Heat Transfer Laboratory 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 Turbomachinery Aero-Heat Transfer Laboratory Phase Locked Approached of PIV Measurements (Image recorded with digital camera on full laser power) r>0r<0

PIV to Pitot Probe Comparison Turbomachinery Aero-Heat Transfer Laboratory “Vertical” test arrangement

Comparison between PIV and Pitot probe results W/o cylinderw/ cylinder PIV Validation with Pitot probe results

Ensemble effect (2) W/o cylinderw/ cylinder Definition:

Figure 24: Comparison of velocity profiles Out-of –plane componentin-plane component axial(z-direction)