Tip Shrouding Experimentation
towards Silencing the Open Rotor
Engine
An Undergraduate Senior Project in Aerospace Engineering
Jose M. Rodriguez
Joshua M. Brander
Octavio A. Camarillo
Michael L. Chan
Suk Hyung Lee
David D. Scholtz
May 21st, 2011
Aerospace Engineering Department
California State Polytechnic University-Pomona
Introductions
Joshua Brander
Lucerne Valley, CA
Background & Interests:
Automotive Racing
Model Rocketry
Project Contributions:
Aerodynamics
CAD/Design
Computational Fluid Dynamics
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Introductions
Octavio Camarillo
Anaheim, CA
Background & Interests:
Aerodynamics
Structural Dynamics
Project Contributions:
Structural Analysis
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Introductions
Michael Chan
Garden Grove, CA
Background & Interests:
CNC Programming/Machining
Manufacturing & QA.
Unmanned Aerial Vehicles
Project Contributions:
Aerodynamic Design
Testing & Manufacturing
Configuration/Integration
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Introductions
Suk Hyung Lee
Seoul, Republic of Korea
Background & Interests:
Military Service- Infantry (Korea)
PCB Design & Electronics Mfg
Distinguished Honors Student
Sigma Gamma Tau
Tau Beta Pi
Alpha Gamma Sigma
Golden Key Int’l
Project Contributions:
Rapid Prototype Manufacturing
Finite Element Methods/Structural Analysis
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Introductions
David Scholtz
Ontario, CA
Background & Interests:
Logistics/Cargo Planning
Math & Physics Tutoring
Project Contributions:
CAD/Design
Graphics & Modeling
Acoustic Measurement
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Introductions
Jose M. Rodriguez
Apple Valley, CA
Background & Interests:
Military Service– U.S. Navy
Aircraft Maintenance
Flight Test/Operations
Air Breathing Engines
Turbomachinery
Project Contributions:
Project Manager
Integration & Testing
Acoustic Measurement
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History & Background

Engines Commonly known as :
◦ Open Rotor
◦ “Propfans”
◦ Unducted Fan Engines

Courtesy of NASA GRC
External set of Counter-Rotating blades
◦ Power Turbine-driven
◦ Mechanically (gearbox) driven
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History & Background
Two Main Programs:
◦ GE/NASA
◦ UDF GE-36
 1970’s-1989
 Turbine Driven
◦ Pratt & Whitney-Allison
◦ UHB 578-DX
 1986-1990
 Gearbox Driven
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History & Background

Interest sparked in 1970’s due to rising fuel
prices/Oil Embargos

Promising designs showed a 30%
improvement in Fuel Efficiency
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History & Background

Problems & Disadvantages:
◦ Limited Mounting Configurations
◦ High Vibrations imparted onto fuselage
◦ Reduced Cruising Speeds
◦ VERY LOUD!!!!!
 In-cabin noise said to be extreme despite aft
mounting on MD-80 series testbed aircraft
 A reduction of approx. 30dB was needed to
realize this concept
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Why Study?

Interest in Open Rotor Engines is making a
comeback due to increasing fuel/oil prices
and “Green” revolution
◦ GE/NASA Leap-X/CF34
◦ Rolls-Royce RB2011

Pertinent & Interesting
topic for senior project

Multi-faceted study
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Our Approach

Attempt to silence by:
◦ Understanding & Manipulating
 Blade Tip Vortices
 Blade Vortex Interaction (BVI) Noise
 Turbulence Ingestion & Broadband Noise
◦ Use of a shroud to reduce BVI & Broadband Noise
 Minimize drag
 Maximize blade exposure to free stream
 Reduce Turbulent Wakefield
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Our Approach

Mimic known good/previous work
GE/NASA
(Allison) Rolls-Royce
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Tip Shrouding

Typical Fan shrouds encapsulate entire rotor
◦ Drag becomes very unfavorable at high speeds

Tip Shroud:
◦ Leaves over 70% of blade open to free-stream
◦ Geometry creates much less drag than a
conventional shroud
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Tip Shrouding
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Limitations

Manufacturing/Materials/Cost
◦ Avoid Aerodynamic/Blade re-designs (Time)

Simple Mechanisms
◦ Variable Pitch & control too complex
◦ Basic power/drive method
Static Testing (ground conditions only)
 Computing Power

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Model Design

Desired to use GE UDF blade configuration
with a variant of NASA SR-7 Blade
◦ 12 Blade Front, 10 Blade Rear
◦ Could not acquire appropriate airfoil data, etc.

Found P&W patent (expired 1996):
◦ Provided airfoil coordinates and data for
aerodynamically-correct modeling.
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Design & CAD
David D. Scholtz
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Blade Modeling

Based off of UTC Patent # 4,730,985
◦ Provided:
 cross-sectional data
 coordinates & blade angles
◦ Excel was used to convert 2D
coordinates into 3D and rotate
cross-section by associated
blade angle

Used Solidworks® to model
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Considerations in Blade Design

(Fixed-Pitch) Blade angle changed to run
in static conditions

Decreased blade loading was desired
◦ Blade Angle (BA): Angle from Chord Line to
Plane of Rotation
◦ BA was decreased from 75.86o by 41.86o to
decrease b along blade
◦ Root BA = 34.00o; Tip BA = 12.18o
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Blade Angle Configuration
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Build Considerations of Blades

Increased thickness of to allow scaling and
manufacturability
◦ Each half of airfoil face
increased by .34 in, full scale to
provide a scaled down
thickness of .05 in. at the tip
for model strength.
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Rotor Modeling
Rotors were created on SolidWorks, via
Circular Patterning feature.
 Front (CW):

◦ 10 blades
◦ 6.50 in. diameter

Rear (CCW):
◦ 8 blades
◦ 5.71 in. diameter
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Nacelles for Test Rig

Front and rear nacelles designed to allow
smooth flow across rotors.
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Tip Shrouds
Two models designed to experiment with
 Model 1:

◦ Basic circular shape, internally flat
 Suspected would not be beneficial due to flow separation
along inner wall of an un-cambered surface
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Tip Shrouds

Model II:
◦ Created with airfoil cross-section to augment
flow across tip-shroud interface
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Computational Fluid Dynamics
Joshua M. Brander
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CFD of Counter-Rotating Rotors
•
CD-Adapco STAR-CCM+
•
Desired to Model Front CW and Aft CCW
Rotor Blades simultaneously
•
Counter-Rotating Assemblies have very
complex flows
•
Limited Computing Power Available
•
Modeled Front Assembly only
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Turbulence Modeling

Flow Visualization
◦ Trimmer Mesh Model w/ Prism Layer Mesher
◦ 0.02 sec Time Step with 30 Inner Iterations/Step
◦ K-Omega Turbulence Model

Pressure Distribution
◦ Polyhedral Mesh Model with Prism Layer Mesher
◦ Smaller Time Step Required Fine Mesh
 5 x 10-6 Time Step w/ 20 Inner Iterations per Step
◦ K-Omega Turbulence Model
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Front Rotor
Flow Velocity M = 0.2
(ground operation/take-off conditions)
1000 RPM
Clockwise (CW) Rotation
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Pressure Distribution
(Incoming Flow)
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Pressure Distribution
(Thrust Side)
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Streamline Pattern
@ 0.5 sec or 8 Rotations
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Tip Vortex Visualization
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Front Rotor w/ Flat Shroud
Flow Velocity M = 0.7
1000 RPM
Streamline @ 0.5 sec or 8 Rotations
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Visualization of Secondary Flows &
Separation
Flow Velocity M = 0.2
 1000 RPM
 Streamline @ 0.5 sec or 8 Rotations

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Unfavorable Flow Separation @ Tips
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Front Rotor w/ Augmented Shroud
Flow Velocity M = 0.2
(ground operation/take-off conditions)
1000 RPM
Clockwise (CW) Rotation
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Pressure Distribution
(Incoming Flow)
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Pressure Distribution
(Thrust Side)
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Streamline Pattern
@ 0.5 sec or 8 Rotations
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Flow Remains Attached
@ Tip-Shroud Interface
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Structural Analysis
Octavio A. Camarillo
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Front Rotor Blade Loading

Pressure distribution
modeled from CFD
results of full scale model

Load magnitudes are
percentages of full scale
loading

Divided into four areas of
different load intensity
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Material Strength
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Front Rotor Blade





Pre & Post processing using FEMAP
Analysis using
NEi NASTRAN
Static Analysis
Blade will fail at 73%
of CFD load
Max load of 9.5 psi
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Rear Rotor Blade





No CFD simulation Available
Used pressure magnitude of
the front blade’s downwash
Assumed Distribution to be
same as the front blade’s.
Blade will fail at 36% of CFD load
Max Press. of 7.5 psi
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Shroud
Shroud deformation
analysis
 Interest is in shroud
critical deformation
 Clearance must be kept
between blade tips and
shroud at all times
 Critical Load at 30 psi

◦ Deflection of 0.144 in
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Rapid Prototype/Building
Suk Hyung Lee
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Rapid Prototyping

OBJET® Rapid Prototype Machine
◦ Alaris 30 3-D Printer
16μ layering
 600 DPI when building along X & Y axis
 800 DPI when building up along Z axis*

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Materials
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Prototyping Software

Object Studio
◦ Source Files
 STL files
 SLC files
◦ Multiple objects on build
tray
◦ Positioning
◦ Configuring object &tray
parameters
◦ Sending the file to Alaris
3-D printer
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Front Rotor Assembly

Manufacturing Time • 226 g Model Material
◦ Warm-up
 20 min
◦ Production
 11 hr 40 min
◦ TOTAL:
 12 hours
• 565 g Support Material
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Rear Rotor Assembly

Manufacturing Time
◦ Warm-up
 20 min
◦ Production
 9 hr 20 min
◦ TOTAL:
 9 hr 40 min
• 138 g Model Material
• 319 g Support Material
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Manufacturing of Test Rig
Michael L. Chan
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NASA Test Rig Inspiration
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Test Rig Manufacturing
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Dual Pylon Test Stand
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Motor L – Bracket
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Pylons
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Final Assembly
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Testing Methods
Jose M. Rodriguez
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Compare Noise Fields

Acquire 360° noise characteristics &
observe any noticeable changes
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Static Testing
2- 3400kV 14.8 Vdc Electric Motors,
 2 Ch. DC Power Supplies
 2-Brushless Electronic
Speed Controls


Individually measure RPM
Noise Measurements
 Polar Plotsfor both open & shrouded rotors

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Work to Follow

Noise Tests & Measurement
◦
◦
◦
◦
Desired: multi-channel microphone arrays
Actual: Blue® Omni-Directional Microphone
Audacity 1.3 Beta Software
PolarPlot v.3.2.7

Study RPM capability & variation

Install Instrumentation on Test Rig
◦ RPM/Tachometers
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THANK YOU!!!
Comments
 Suggestions
 Questions (no hard ones)
 Advice

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