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!