Facility for calibrating anemometers as a function of air velocity vector and turbulence

Abstract

NIST calibrates anemometers as a function of airspeed vector and turbulence intensity (Tu). The vector capability (sometimes called '3D') is particularly important for calibrating multi-hole differential-pressure probes that are often used to quantify pollution emitted by smokestacks of coal-burning electric power plants. Starting with a conventional '1D' wind tunnel, we achieved vector and Tu capabilities by installing translation/rotation stages and removable turbulence generators (grids or flags). The calibration ranges are: yaw angle ±180 • ; pitch angle ±45 • ; airspeed 1 m s −1 to 30 m s −1 ; turbulence intensity 0.07 Tu 0.25; average data collection rate: 300 points/h at fixed Tu. The system's expanded uncertainties corresponding to 95% confidence level are: airspeed 0.0045 × |V| + (0.036/|V|) 2 where |V| is the magnitude of the airspeed in m s −1 ; pitch and yaw angles 0.3 • ; and turbulence intensity 0.03 Tu. The airspeed working standard is a laser Doppler anemometer that is traced to SI unit of velocity via a spinning disk. Calibrations are corrected for blockage by the instrument under test and its supports.

An automated system for flow characterization at exhaust ducts and smokestacks

“…Therefore, each probe was calibrated in the NIST Airspeed Calibration Facility. [10] For this application, the calibration coefficients are represented as functions of the differential pressure measured at the S-probe. Power law fits, listed in Table 2, were derived from the calibration data and are used to compute calibration coefficients for each probe.…”

A Calibration Facility for Hot-Wire Anemometers in Extremely Low Speed with Air Temperature and Humidity Variable and Controllable

“…In the past decades, various facilities including wind tunnels, nozzles, laminar pipe flow rigs, and probe-moving-type facilities for hot-wire calibration in extremely low speed regime have been built in the world. Wind tunnels, including nozzles (i.e., jet-type tunnels) and laminar pipe flow rig for hot-wire calibration, can be seen in the National Institute of Standards and Technology (NIST) in the USA [1,19,20], the Centre Technique des Industries Aérauliques et Thermiques (CETIAT) in France [2,21], the Physikalisch Technische Bundesanstalt (PTB) in Germany [2], the Instituto Nacional de Técnica Aeroespacial "Esteban Terradas" (INTA) in Spain [2], the Université Catholique de Louvain (UCL) in Belgium [2], the Nottingham Trent University in the United Kingdom (the air can be heated) [16], the Universidad Nacional de La Plata in Argentina [12], the University of Gävle in Sweden [17], the Iranian Research Organization for Science and Technology (IROST) in Iran (the air can be heated, velocity range is 5 m/s to 30 m/s) [10], the Institute of Atmospheric Physics, Chinese Academy of Sciences [22], the Institute of Metrology, Chinese Academy of Meteorological Sciences (CAMS) [23], the National Institute of Metrology, China(NIMC) [24,25], and the University of Gaziantep in Turkey (laminar pipe flow rig) [6]. The air velocity in these facilities ranges from 0.029 m/s to 75 m/s with a velocity control accuracy of 0.02 m/s (0.5% to 7.4%), a velocity uncertainty of 0.014 m/s to 0.06 m/s (1% to 10%), and a calibration fitting error of 0.018 m/s to 0.03377 m/s (4%) (see Table 1).…”