1、Designation: D 5096 02Standard Test Method forDetermining the Performance of a Cup Anemometer orPropeller Anemometer1This standard is issued under the fixed designation D 5096; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the ye
2、ar of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers the determination of the Start-ing Threshold, Distance Constant, Transfer Function, and
3、Off-Axis Response of a cup anemometer or propeller anemom-eter from direct measurement in a wind tunnel.1.2 This test method provides for a measurement of cupanemometer or propeller anemometer performance in theenvironment of wind tunnel flow. Transference of valuesdetermined by these methods to atm
4、ospheric flow must be donewith an understanding that there is a difference between thetwo flow systems.1.3 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and h
5、ealth practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D 1356 Terminology Relating to Sampling and Analysis ofAtmospheresD 3631 Test Methods for Measuring Surface AtmosphericPressure3. Terminology3.1 For definitions of terms
6、 used in this standard, refer toTerminology D 1356.3.2 Definitions of Terms Specific to This Standard:3.2.1 starting threshold (Uo, m/s)the lowest wind speed atwhich a rotating anemometer starts and continues to turn andproduce a measurable signal when mounted in its normalposition. The normal posit
7、ion for cup anemometers is with theaxis of rotation vertical, and the normal position for propelleranemometers is with the axis of rotation aligned with thedirection of flow. Note that if the anemometer axis is notaligned with the direction of flow, the calculated wind speedcomponent parallel to the
8、 anemometer axis is used to deter-mine starting threshold.3.2.2 distance constant (L, m)the distance the air flowspast a rotating anemometer during the time it takes the cupwheel or propeller to reach (1 1/e) or 63 % of the equilibriumspeed after a step change in wind speed (1).3The response ofa rot
9、ating anemometer to a step change in which wind speedincreases instantaneously from U =0toU=Ufis (2):Ut5 Uf1 2 e2t/ t! (1)where:Ut= is the instantaneous indicated wind speed at time t inm/s,Uf= is the final indicated wind speed, or wind tunnel speed,in m/s,t = is the elapsed time in seconds after th
10、e step changeoccurs, andt = is the time constant of the instrument.Distance Constant is: L 5 Uft (2)3.2.3 transfer function (f= a+bR, m/s)the linear rela-tionship between wind speed and the rate of rotation of theanemometer throughout the specified working range. fis thepredicted wind speed in m/s,
11、a is a constant, commonly calledzero offset, in m/s, b is a constant representing the windpassage in m/r for each revolution of the particular anemometercup wheel or propeller, and R is the rate of rotation in r/s. Itshould be noted that zero offset is not the same as startingthreshold. In some very
12、 sensitive anemometers the constant a,zero offset, may not be significantly greater than zero. Theconstants a and b must be determined by wind tunnel measure-ment for each type of anemometer (3).3.2.4 off-axis response (U/(Ufcos u)the ratio of theindicated wind speed (U) at various angles of attack
13、(u)totheindicated wind speed at zero angle of attack (Uf) multiplied bythe cosine of the angle of attack. This ratio compares the actualoff-axis response to a cosine response.1This test method is under the jurisdiction of ASTM Committee D22 onSampling and Analysis of Atmospheres and is the direct re
14、sponsibility of Subcom-mittee D22.11 on Meteorology.Current edition approved October 10, 2002. Published December 2002. Origi-nally published as D 5096 90. Last previous edition D 5096 96.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at service
15、astm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3The boldface numbers in parentheses refer to the list of references at the end ofthis standard.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Consh
16、ohocken, PA 19428-2959, United States.3.3 Symbols:a (m/s) = zero offset constantb (m/r) = wind passage (apparent pitch) constant orcalibration constantL (m) = distance constantr (none) = a shaft revolutionR (r/s) = rate of rotationt(s) = time constantt (s) = timeUo(m/s) = starting thresholdU (m/s) =
17、 indicated wind speed (used in off-axis test)Uf(m/s) = final indicated wind speed or wind tunnelspeedUmax(m/s) = anemometer application rangeUt(m/s) = instantaneous indicated wind speed at time tf(m/s) = predicted wind speedu (deg) = off-axis angle of attack4. Summary of Test Method4.1 This test met
18、hod requires a wind tunnel described inSection 6, Apparatus.4.2 Starting Threshold (Uo, m/s) is determined by measur-ing the lowest speed at which a rotating anemometer starts andcontinues to turn and produce a measurable signal whenmounted in its normal position.4.3 Distance Constant (L, m) may be
19、determined at anumber of wind speeds but must include 5 m/s, and 10 m/s. Itis computed from the time required for the anemometer rotor toaccelerate (1 1/e) or 63 % of a step change in rotational speedafter release from a restrained, non-rotating condition. Thefinal response, Uf, is the wind tunnel s
20、peed as indicated by theanemometer. In order to avoid the unrealistic effects of therestrained condition, as shown in Fig. 1, the time measurementshould be made from 0.30 of Ufto 0.74 of Uf. This interval inseconds is equal to one time constant (t) and is converted to theDistance Constant by multipl
21、ying by the wind tunnel speed inmeters per second (m/s).4.4 Transfer Function (f= a+bR, m/s) is determined bymeasuring the rate of rotation of the anemometer at a numberof wind speeds throughout the specified working range. In therange of wind speeds where the anemometer response isnon-linear (near
22、threshold) a minimum of five data points arerecorded. A minimum of five additional data points arerecorded within the working range of the anemometer andwind tunnel but above the non-linear threshold region (see Fig.2). Measurements are recorded for each data point with thewind tunnel speed ascendin
23、g and descending. The values of aand b are determined by least-squares linear regression of theindividual data points.4.5 Off-Axis Response may be measured at a number ofwind speeds but must include 5 m/s, and 10 m/s.4.5.1 Cup AnemometersA measurement is made of theoutput signal when the anemometer
24、is inclined into the wind(representing a down-draft) and away from the wind (repre-senting an updraft), while the wind tunnel is running at a steadyspeed. The output signal is measured with the anemometer axisat 5 intervals from vertical to plus and minus 30 fromvertical. The measured signal is then
25、 converted to a ratio foreach interval by dividing by the normal signal measured withthe anemometer axis in the normal, or vertical, position.4.5.2 Vane Mounted Propeller AnemometersA measure-ment is made of the output signal when the anemometers axisof rotation is inclined downward into the wind (r
26、epresenting adown-draft) and inclined upward into the wind (representing anupdraft), while the wind tunnel is running at a steady speed.The output signal is measured at 5 intervals from a horizontalaxis of rotation to 630 from the horizontal. The measuredsignal is then converted to a ratio for each
27、interval by dividingby the normal signal with the anemometer in the normal, orhorizontal position. This test may be conducted either with thevane in place or with the vane removed and the axis of rotationfixed in the down-tunnel direction.4.5.3 Fixed Axis Propeller AnemometerAmeasurement ismade of t
28、he output signal when the anemometer is rotated inthe air stream throughout the complete 360 angle of attack.The signal is measured at a number of angles but must include10 intervals with additional measurements at 85, 95, 265, and275. The measured signal for each angle of attack is thenconverted to
29、 a ratio by dividing by the signal measured at 0angle of attack (axial flow). Additionally, the stall angle of thepropeller is measured by orienting the anemometer at 90 andFIG. 1 Typical Anemometer Response Curve FIG. 2 Typical Anemometer Calibration CurveD5096022slowly rotating into and away from
30、the air flow until thepropeller starts rotating continuously. Stall angle is the totalcontained angle within which the propeller does not continu-ously rotate. The procedure is repeated at 270.5. Significance and Use5.1 This test method will provide a standard for comparisonof rotating type anemomet
31、ers, specifically cup anemometersand propeller anemometers, of different types. Specificationsby regulatory agencies (4-7) and industrial societies havespecified performance values. This standard provides an un-ambiguous method for measuring Starting Threshold, DistanceConstant, Transfer Function, a
32、nd Off-Axis Response.6. Apparatus6.1 Measuring System:6.1.1 RotationThe relationship between the rate of rota-tion of the anemometer shaft and the transducer output must bedetermined. The resolution of the anemometer transducerlimits the measurement. The resolution of the measuring orrecording syste
33、m must represent the indicated wind speed witha resolution of 0.02 m/s.6.1.2 TimeThe resolution of time must be consistent withthe distance accuracy required. For this reason the timeresolution may be changed as the wind tunnel speed ischanged. If one wants a distance constant measurement to 0.1mete
34、r resolution one must have a time resolution of 0.05 s at 2m/s and 0.01 s at 10 m/s. If timing accuracy is based on 50 Hzor 60 Hz power frequency it will be at least an order ofmagnitude better than the resolution suggested above.6.1.3 Angle of AttackThe resolution of the angle of attack(u) must be
35、within 0.5.An ordinary protractor of adequate sizewith 0.5 markings will permit measurements with sufficientresolution. A fixture should be constructed to permit alignmentof the anemometer to the off-axis angles while the wind tunnelis running at a steady speed.6.2 Recording Techniques:6.2.1 Digital
36、 recording systems and appropriate reductionprograms will be satisfactory if the sampling rate is at least 100samples/s. Exercise care to avoid electronic circuits with timeconstants which limit the proper recording of anemometerperformance. Oscilloscopes with memory and hard copy capa-bility may al
37、so be used. Another simple technique is to use afast-response strip chart recorder (flat to 10 Hz or better) withenough gain so that the signal produced by the anemometerwhen the wind tunnel is running at 2 m/s is sufficient to providefull scale pen deflection on the recorder. The recorder chartdriv
38、e must have a fast speed of 50 mm/s or more.6.3 Wind Tunnel (8):6.3.1 SizeThe wind tunnel must be large enough so thatthe projection of the cup wheel or propeller, sensor, andsupport apparatus, is less than 5 % of the cross sectional areaof the tunnel test section.6.3.2 Speed RangeThe wind tunnel mu
39、st have a speedcontrol which will allow the flow rate to be varied from 0 to aminimum of 50 % of the application range of the anemometerunder test. The speed control should maintain the flow ratewithin 60.2 m/s.6.3.3 CalibrationThe mean flow rate must be verified atthe mandatory speeds by use of tra
40、nsfer standards which havebeen calibrated at the National Institute of Standards andTechnology or by a fundamental physical method. Speedsbelow 2 m/s for the threshold determination must be verified bya sensitive anemometer or by some fundamental time anddistance technique, such as measuring the tra
41、nsition time ofsmoke puffs, soap bubbles, or heat puffs between two pointsseparated by known distance. A table of wind tunnel blowerrpm or some other index relating method of control to flow rateshould be established by this technique for speeds of 2 m/s andbelow.6.3.4 The wind tunnel must have a re
42、latively constantprofile (known to within 1 %) and a turbulence level of lessthan 1 % throughout the test section.6.3.5 Environment (9-11). Differences of greater than 3 % inthe density of the air within the test environment may result inpoor intercomparability of independent measurements of start-i
43、ng threshold (Uo) and distance constant (L) since these valuesare density dependent. The temperature and pressure of theenvironment within the wind tunnel test section, and theambient air pressure (Test Methods D 3631) shall be reportedfor each independent measurement.7. Sampling7.1 Starting Thresho
44、ldThe arithmetic mean on ten con-secutive tests is required for a valid starting threshold mea-surement.7.2 Distance ConstantThe arithmetic mean of ten tests isrequired for a valid measurement at each speed. The results ofthe measurements at two or more speeds are averaged to asingle value for dista
45、nce constant.7.3 Transfer FunctionTwo measurements of Ufand R arerecorded for each data point, one with the wind tunnel speedascending and one with the wind tunnel speed descending. Thevalues are then tabulated for each data point.7.4 Off-Axis ResponseThe results of the measurement attwo or more spe
46、eds are averaged to a single value for eachangle of attack. The averaged values are tabulated for eachangle of attack.8. Procedure8.1 Starting Threshold (Uo):8.1.1 Provide a mechanical method for holding the an-emometer in its normal position (see 3.1) and for releasing theanemometer from a restrain
47、ed, or non-rotating condition, whilethe wind tunnel is running at the test speed. Test the releasemechanism with the wind tunnel off to verify that the releasemethod does not move the anemometer rotor when activated.8.1.2 Set the wind tunnel to a speed that is lower than thestarting threshold. Slowl
48、y increase the wind tunnel speed untilthe cup wheel or propeller continues to rotate and produce ameasurable signal.8.1.3 Repeat the procedure of 8.1.2 ten times and record theresults.NOTE 1Vibration caused by the wind tunnel or by other sources cancause erroneous measurements of starting threshold.
49、 Care must beexercised to eliminate any vibration in the wind tunnel test section duringthreshold measurements.D50960238.2 Distance Constant (L):8.2.1 Set the wind tunnel speed to 5 m/s. Stop the rotation ofthe cup wheel or propeller and release by method of 8.1.1.Record ten samples.8.2.2 Repeat procedure of 8.2.1 at 10 m/s.8.2.3 From the record measure the time in seconds (t) fromthe point when the rotor speed reaches 0.30 of equilibriumspeed (Uf) to the point where the rotor speed reaches 0.74 ofequilibrium speed (see Fig. 1). The distan
