Relevant parameters during anemometer calibration Dieter Westermann & Peter Busche Deutsche WindGuard

Transcription

1 Relevant parameters during anemometer calibration Dieter Westermann & Peter Busche Deutsche WindGuard

2 Relevant parameters during anemometer calibration Find out what kind of wind tunnel induced parameters will influence the wind tunnel calibration Evaluate these parameters Assess the influence and indicate limits

3 tested parameters / influence Measurement of reference wind speed Repeatability of measurement results Flow quality; wind tunnel design Flow homogeneity turbulence flow conditioners Test section boundaries Positioning of anemometer within test section Air density / temperature

4 WindGuard Wind Tunnel Research Documented Wind Tunnel Investigations since 2003 Year Title Topic Westermann D.; Internal investigation 2007 Geometrical interference 2006 N. Balaresque; Master thesis Blockage effects on Anemometer Calibration 2008 U. Tolle; Bachelor thesis Untersuchung zur Strömungsrichtungsbestimmung im Windkanal 2009 C.Herold; Bachelor thesis Messunsicherheiten bei der Kalibrierung von Schalensternanemometern im Windkanal R. Mueller; NMI Germany (PTB) -> Comparison between national flow standard and WindGuard wind tunnel speed 2010 J. Kopmann; Bachelor thesis Vermessung der Strömung in der halboffenen Messstrecke eines Windkanals mittels Pitot- Sonden 2010 J. Wilkening; Master thesis Ausarbeitung und Verifizierung eines Klassifikationsmodells für Ultraschallanemometer im Windkanal 2011 P. Löst; Bachelor thesis Untersuchungen der Anzeigegenauigkeit von Staudrucksonden 2011 H. Westermann; Bachelor thesis Entwicklung und Test eines Sensors zur Untersuchung der Sprungantwort eines Cup Anemometers P.Busche; D.Westermann; Internal MEASNET document 2012 Intercomparison Test of MEASNET Wind Tunnels 2012 F. Sczesny; Bachelor thesis Experimentelle Untersuchung des dynamischen Verhaltens von Schalensternanemometern 2013 R. Kuhlemann; Master thesis Untersuchung zum Einfluss turbulenter Strömungen im Windkanal auf das 2013 L.Büttelbrunn; Bachelor thesis Untersuchungen des Einflusses der Messstrecke eines Windkanals auf das 2013 Y. Zuelfikar; Master thesis Untersuchungen zur Beeinflussung der Strömungsqualität in Windkanälen durch Siebe Blockage Flow direction Uncertainty due anemometer mounting Reference speed accuracy Flow quality Classification of sonic Comparison between LDA and ISO 3966 Calibration factor Step response MEASNET uncertainty Step response; Classification Wind tunnel turbulence Influence due to test section boundaries Wind tunnel turbulence

5 Project reference speed measurement with German National Metrology Institute (PTB)

6 DWG Pitot - PTB LDA / m/s Project reference speed measurement with German National Metrology Institute (PTB) Deviation WindGuard - German NMI (PTB) 0,15 0,10 Uncertainty WindGuard Uncertainty NMI (PTB Germany) y = 0,00092x R² = 0, ,05 0,00-0,05-0,10-0,15 0,0 5,0 10,0 15,0 20,0 25,0 30,0 35,0 40,0 Flow Speed / m/s

7 Repeatability during anemometer calibration

8 Tests Performed in Wind Tunnel of Different Design 1. Eiffel Wind Tunnel - Speed up 25 m/s - Closed test section - Test section 0.6 x 0.8 m - Contraction ratio Temperature Turbulence 1.0% - 6% Diffuser Heat exchanger Test section Nozzle Spray nozzles 2. Closed Return Wind Tunnel - Speed up to 18 (30, 40) m/s - Semi open test section - Test section 1.0 x 1.0 m - Contraction ratio Turbulence 0.2% 1.0 % Test section 2. Diffuser Nozzle

9 Test Program Anemometers tested Anemometers tested Vector A 100 Thies FC Thies Classic Thies 2 D Sonic Big Cup Windspeed A100 Windsensor P2546 Propeller big Propeller small

10 Test Program Anemometers tested cw and ccw rotor of each cup anemometer was tested easy way to identify horizontal flow gradient: Ratio cw/ccw should be the same for all tested setups

11 Test Program Influence of tunnel boundaries open side wall Influence due to limited test section View into the nozzle movable anemometer movable plate

12 Test Program Influence of tunnel boundaries Influence of distance to bottom plate

13 Test Program Influence of tunnel boundaries Influence of distance to top plate

14 Test Program Influence of tunnel boundaries Influence in wind tunnel reference speed due to moving plate Pitot static tube

15 Test Program Influence of tunnel boundaries Influence in wind tunnel reference speed due to moving plate measured with Prandlt tubes v z /v z0 / z z 0 -z Height (z) / cm

16 Test Program Influence of tunnel boundaries Influence of distance anemometer to top or bottom plate z = - 20cm 1.02 z = 10cm v z /v z_max / Big cup Classic 0.96 z = - 90cm Sonic Windsensor Vector z = 70cm FC Distance to bottom (ceiling) / cm

17 Test Program Influence of tunnel boundaries Influence due to side walls (right open; left closed)

18 Test Program Influence of tunnel boundaries Ratio v y /v 0 / Influence due to side walls (right open; left closed) Solid wall Test section limit Big cup ccw Big cup cw Small cup Sonic Distance to center line / cm

19 Test Program Influence of tunnel boundaries Minimum distances anemometer to top plate for tilt measurements

20 Test Program Influence of tunnel boundaries Minimum distances anemometer to top plate for tilt measurements Ratio v (z) /v (35 cm) / deg 0 deg - 30 deg Ceiling height above rotor (cm)

21 Test Program Procedure for Tilt measurements Comparison between step wise and continuous measurements cos continuous step Tilt ratio / tunnel speed 8 m/s; tilt angle Tilt angle / deg

22 Test Program Procedure for Tilt measurements II Tilt comparison between continuous and via calibration function (attained at fixed tilt angles) calibration function at -20 tilt angle 4 m/s 8 m/s 12 m/s 16 m/s 4m_s 8m_s 12m_s 16m_s Tilt ratio / Tilt angle / deg

23 Test Program Test Section Turbulence Flow conditioners in open circuit wind tunnel

24 Test Program Test Section Turbulence Flow conditioners in closed return circuit wind tunnel

25 Test Program Test Section Turbulence Pitot static tube array In Göttinger wind tunnel In Eiffel wind tunnel

26 Test Program Test Section Turbulence Turbulence intensity in open return wind tunnel turbulence intensity / cut off frequency : 10 Hz Sonic Thies 3D Pitot Static Tube Hot Wire Number of flow conditioners cut-off frequency 10 Hz

27 Test Program Test Section Turbulence Influence of calibration result upon varying degrees of wind tunnel turbulence (Thies FCA; 8;12;16 m/s) 1.02 Ratio k N /k ave (8;12;16 m/s) / closed return wind tunnel open return wind tunnel different turbulence levels achieved by varying number (N) of flow conditioners Turbulence intensity / -

28 Test Program Test Section Turbulence / Flow Quality Calibration results of Windsensor P2546A anemometer cw/ccw in open return (Eiffel) wind tunnel Ratio / m/s (CW) 8 m/s (CW) 12 m/s (CW) 16 m/s (CW) 4 m/s (CCW) 8 m/s (CCW) 12 m/s (CCW) 16 m/s (CCW) No. 8 honey-comb flow straightener Number of Flow Conditioners /-

29 Test Program Influence of Flow Turbulence Turbulence intensity measured with 3D sonic (8 m/s) in open return (Eiffel) wind tunnel Ti / Tu Vertikal Tu Longitudinal Tu Lateral No. 8 honey-comb flow straightener Number of Flow Condtioners /-

30 Test Program Influence of Flow Turbulence Reduction of flow angle deviation due to honey comb 6.0 Flow Angle / deg vertical lateral Number of Flow Conditioners / - No. 8 honey-comb flow straightener

31 Test Program Influence of Air Density / Temperatur Speed range: m/s Test section: 0.5 x 0.5 x 0.8 m Contraction ration 3.3:1 Static pressure bar(a) Temperature range C tunnel placed inside freezer box

32 Test Program Influence of Air Density f / f (1.2) / m/s 8 m/s 12 m/s 14 m/s Air density / kg/m³

33 Test Program Influence of Air Temperature Anemometer type A

34 Test Program Influence of Air Temperature Anemometer type B

35 Outcome Test section width 0.8 m better 1.0 m Test section size 0.4 m above anemometer Test section size minimum 0.5 m below anemometer The calibration results are unaffected by turbulence intensity in the range % Flow conditioners (incl. screens and honey comb) are absolutely necessary Closed return wind tunnel produces much better flow conditions Tilt measurement are possible using step wise, continuous or through calibration functions (attained fixed tilt angles!) Steep gradients in tilt response are possible a continuous sweep of the tilt angel is preferred. Remark: All the results presented are based on measurements in WindGuard Eiffel wind tunnel and Göttinger wind tunnel no 3 with semi open test section

36 The instrument should be read every morning at 9 o clock Dr. Robinson 1849

37 Thank you for your attention