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The temperature and pressure effects on wind speed meter calibration
1 introduces the temperature and pressure influence on wind speed meter calibration
wind speed meter calibration is usually at a constant in the wind tunnel, the mainstream of the air temperature and atmospheric pressure. This calibration is the basis of the wind tower wind speed measurement, so it can be used in the assessment of the potential wind farm sites. Due to environmental parameters affect the performance of the anemometer, so you must choose the anemometer is suitable for a particular site. In addition, the accurate field fan performance assessment and control for the measurement of environmental impact is also very important.
anemometer have different level of accuracy. In the latest IEC 61400 - 12 - 1 standard [ 1] , describes the need to be the time when anemometer classification of the different impact parameters. Different levels corresponding to the influence parameters of different operating range. Including air temperature and air density.
in IEC 61400 - 12 - 1 [ 1] , assuming that the air temperature change only affects the bearing friction. Higher air temperature can reduce friction, thus improve the speed, and vice versa.
[in the IEC standard 1] No further advice on how to evaluate air density change. Air density is a function of air temperature and air pressure. In order to study the effect of air density change, can change the air temperature or air pressure. If used in the calibration process temperature changes to adjust the air density, it is difficult to distinguish between changes of air temperature and density. If two parameters, namely, air temperature and air pressure can be changed independently, can obtain the most accurate results.
in the standard wind tunnel, usually cannot be accurately set air temperature and pressure. Therefore, the impact of these conditions can't reliable estimate. Design a Gö here; Ttinger layout is used to study the wind tunnel, able to independently change wind channel environment pressure and temperature.
this document describes the wind tunnel service company in air density variable wind tunnel, the cup anemometer, propeller anemometer and calibration method for measuring ultrasonic anemometer. Calibration results is anemometer at different temperature and/or instructed by the wind speed under different pressure. Calibration results can be used to estimate in the very low or high temperature and/or high altitude ( Low temperature and low density) The uncertainty of the wind sensor. These results for according to IEC [ 1] The classification of the anemometer is also indispensable.
, in the second chapter introduces the previous to temperature changes on the cup type anemometer bearing friction effect of investigation. In the third chapter, a technical description of variable air volume density of the wind tunnel is presented, and then given for variable air temperature and air pressure anemometer calibration procedures. In the fourth chapter introduces the uncertainty is calculated. Finally, shows the aimed at two different, commonly used and has a frequency signal output, and have similar shape cup anemometer results and final conclusions.
2 before the temperature in the study of the influence of the anemometer output of
previous studies ( ( 2] ,[ 3] ) Through the flywheel experiment in climate chamber temperature influence on wind cup anemometer wind speed measurements.
in figure 1 and figure 2 is a climate chamber with the flywheel experimental study on the bearing friction experiment device. The program assumes the air resistance of the rotating disc is known. Even so, also need to use by W. G。 ( 4] In 1934 established a resistance coefficient, because the coefficient of no new reliable numerical. In the undergraduate thesis [ 3] According to different specifications, within the scope of the disk, and different surface roughness value tested the flywheel. Results show a high deviation.
figure 1:2004 by RIS RISP2546 cup type wind speed meter of characterization and classification experiment [ 2] For flywheel test in the climate chamber experiment device. Figure 2:
flywheel wind tunnel service climate chamber test experiment device.
in 2003, a classification of anemometer used a similar program to calculate the influence of different pressure and temperature [ 5] 。 Using foil heater to increase the temperature of the bearing shaft alone, see figure 3. In order to lower the temperature of the bearing axis, constructs the cooling device, as shown in figure 4.
figure 3: through the foil heater to generate high temperature experiment device. The necessary adiabatic not shown here.
figure 4: through the cooling unit to produce low temperature experiment device. The necessary adiabatic not shown here.