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Development of a probe traversing system
for an open test section wind tunnel
Gépészet 2012 Conference
24th of May, 2012
Section Energy 2.
Árpád Varga
Mechanical Engineering Modelling MSc,
Contractual student of Theodor von Kármán Wind Tunnel Laboratory
Content
1) Introduction
• Wind Tunnel tests, the LHWT at DFM
• Role of „positioning” on the field of aerodynamical
measurements (examples connected to the topic of renewable
energy production)
2) Presenting the LWTTS
• Operation requirements
• Structural design
• Aerodynamic design
• Electric systems and control
3) Future plans for development
Wind Tunnel tests ↔ CFD simulations
Large Horizontal Wind Tunnel (LHWT) at Theodor von Kármán
Wind Tunnel Laboratory (TKWTL) of Department of Fluid
Mechanics (DFM)
•Recirculating, Göttingen-type tunnel, open test section
Role of positioning in aerodynamical measurements
•Varying the location and/or the orientation relative to the wind
direction of the downscaled model inside the measurement section
Wind loads acting on roof mounted solar arrays – different wind
directions (supermarket)
Solar collector damaged by wind
Role of positioning in aerodynamical measurements
•Moving probes (pressure, velocity, temperature, concentration
etc. sensors) into predetermined spatial points in order to map the
distribution of selected physical quantities along curves or on
surfaces.
Boundary layer for building aerodynamics investigations
Role of positioning in aerodynamical measurements
•Moving probes (pressure, velocity, temperature, concentration
etc. sensors) into predetermined spatial points in order to map the
distribution of selected physical quantities along curves or on
surfaces.
Wind turbine wake measurements in wind tunnel – wind farms
J. Bartl: Wake
measurements
behind
an array of
two model wind
turbines Master of
Science Thesis, KTH
School of Industrial
Engineering and
Management,
Stockholm
Role of positioning in aerodynamical measurements
•Providing rigid, easily variable fixing stand for complementary
instruments (laser light sources, optics, high speed camera etc.)
applied during test.
PIV measurement on a road vehicle model - fixing the mirror optics
Presenting LWTTS
Large Wind Tunnel Traversing System (LWTTS) – a new PC
controlled, universal positioning system for probe and
instrument positioning, designed according to special
requirements (past experiences), structurally integrated to the
test section of the LHWT
1) Flow disturbance and any access limitation to the test section
should not be allowed while the LWTTS is in its neutral “parking”
position.
2) Limited amount of space for movement above the test section
due to the structure of five component aerodynamic balance.
3) The range of available positions by the probe mounted on the
LWTTS must cover the largest possible volumetric domain of
the utilized measurement section. (The LHWT test section
volume is 4m long and has a diameter of 2.6m.)
4) Sufficient structural stiffness in order to avoid the wind induced
vibrations up to 40 m/s airspeed.
5) The LWTTS must be able to move and hold on position an
arbitrary device (probe, laser optics, camera) with maximal
overall dimensions in 100x100x100 mm and 2 kg in weight.
6) The precision of the positioning must be below 0.5 mm in
horizontal direction and must not exceed 0.2 mm in vertical
direction.
Operation requirements
Operation requirements-lim. space above the test sect.
Longitudinal Cross section of the LHWT
Structural design
•Cartesian manipulator with H-portal arrangement (milling machines)
•Conceptual design: T. Kerekes (BSc Thesis);
•Detailed CAD design: M. Balczó
Structural design – X axis
Standard BOSCH
profiles with high
bending stiffness
Guiding shafts with
circular cross-section
Linear bearings
Structural design – X axis drive
Pulley
Synchronizing shaft
Tensioned toothed belt
Guiding disks
Scheme of the X-axis
drive
Structural design – Y axis
Test assembly of
the X and Y
LWTTS axes at
TKWTL
Y axis mounting plate
Additional guiding shaft
for Y axis
Y axis – standard
linear drive unit
with auxiliary linear
guidance
Structural design – telescopic Z axis (Z1,Z2)
Original conception: T. Kerekes, 2005
Two ball screw linear motion units
(Z1, Z2), which are fixed rigidly to
each other
Probe holding arm
Z1
Z2
Structural design – telescopic Z axis fixed on Y mounting plate
Y axis mounting
plate
Robust intermediate
component
Z axis
Aerodynamic design
As parts of the LWTTS are exposed to the flow, the aerodynamic
design was needed to:
1) decrease wind forces acting on the structure
2) avoid separating vortices which may cause vibrations to the
system
3) to minimize disturbance of the flow (static pressure)
Simplified 2D simulations of X axis carrige nose cover (30 m/s). Left: X axis
aluminium profiles without streamlined cover; Right: with asymmetric nose
cover mounted on the forward beam.
Static pressure disturbance prediction (by A. Gulyás):
X axis carrige cross-section reach the air-
jet in the mid-plane of the test section
Aerodynamic design – the Y axis nose cover
Aerodynamic design – the Z axis streamlined shell and the
probe holding arm
•Symmetric composite airfoil cover profile for the Z1 axis
•Streamlined probe holding arm cross-section
Aerodynamic design – the Z axis streamlined shell
•Power supply
•Stepper drivers
•Stepper motors
•Encoders – Closed
loop position control!
•PC interface
•Control softvare
developed in
LabVIEW
•Limit switches
•Energy chains
Electic systems and control
Electic systems and control – Energy chains
Future plans for development
1)Sensor cable set-up
• Secondary energy chain system for sensor
wiring
2)Precision measurements
• (Deflection of the X axis ?)
3)Software development –
• coincidence detection,
• measurement grid generator,
• automatic measurements,
•Z axis movement strategies (over-defined axis!)
Videos
http://www.youtube.com/watch?v=Z_Mws7IvNvg&list=U
U87Iu_JR-jPr-64BB5aKvUA&index=3&feature=plcp
http://www.youtube.com/watch?v=Fc96Uu57NwQ&list=
UU87Iu_JR-jPr-64BB5aKvUA&index=1&feature=plcp
•Ground testing
•First movements in the test section of the LHWT
Thank you for your attention!
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