New air speed calibration system at NMIJ for air speeds up to 90 m/s

Iwai, Aya; Funaki, Tatsuya; Kurihara, Noboru; Terao, Yoshiya; Choi, Yong Moon

doi:10.1016/j.flowmeasinst.2019.02.004

Cited by 3 publications

(6 citation statements)

References 9 publications

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“…A comparison experiment with a national standard of flow velocity was conducted to evaluate the measurement accuracy of RTA. The reference velocity 15 was derived from a flow rate reference 16 based on reference nozzles. As depicted in Fig.…”

Section: Resultsmentioning

confidence: 99%

“…The reference velocity at the sensor position fixed to the traverse apparatus is calculated from the volumetric flow rate at the wind tunnel outlet, cross-sectional area (outlet diameter: 60 mm), and boundary layer thickness. The derivation of the reference flow velocity is explained in detail by Iwai 15 . When calculating the flow velocity using RTA, both T r and T 0 are required, and the T 0 of the fluid on the streamline is measured using a platinum thermometer on the upstream side of the wind tunnel.…”

Section: Resultsmentioning

confidence: 99%

“…The expanded uncertainty of the flow rate is approximately 0.28% (coverage factor: 2) 28 . The expanded uncertainty of the reference velocity based on the flow rate reference is estimated to be approximately 0.63% (coverage factor: 2) 15 . The traverse apparatus (Siguma Koki) shown in Fig.…”

Section: Methodsmentioning

confidence: 99%

“…The two probe temperature sensors were selected to be as small as possible, and the same value of recovery temperature coefficient r of 0.83 was used for both sensors. The accuracy of RTA using these thermometers was evaluated using the reference velocity (range: approximately 40–90 m/s) with an expanded uncertainty of 0.63% (coverage factor: 2) 15 owned by the National Metrology Institute of Japan. In addition, RTA was applied to the measurement of flow velocity in a small sonic nozzle with a throat diameter of 13.4 mm; the accuracy of the measurement in sonic flow was evaluated by comparing it with the results of the 3D numerical simulations.…”

Section: Introductionmentioning

confidence: 99%

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Verification of flow velocity measurements using micrometer-order thermometers

Takegawa

Ishibashi

Iwai

et al. 2021

Sci Rep

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In flow velocity measurements, resolution, miniaturization, and accuracy of measuring devices are important issues because the measuring devices significantly affect the flow in the micro-space, sonic flow, and turbulent flow. We studied recovery temperature anemometry (RTA) using micrometer-order thermometers and evaluated its validity in two velocity ranges (40–90 and 315–420 m/s) by conducting two experiments and a numerical simulation. The results confirmed that the difference between the reference velocity and RTA was within 5% in the velocity range 60–90 m/s for both the thermocouple and platinum thermometer given the same recovery temperature coefficient of 0.83. It is a valuable finding that velocity measurement by RTA is independent of the type of thermometer used. This suggests that the accuracy of about 5% can be guaranteed even without calibration by giving the recovery temperature coefficient according to the thermometer geometry, which is an excellent advantage not found in other anemometers. Furthermore, the supersonic flow measured using RTA agrees well with the simulation results and theoretical trends. Our findings ensure that the micrometer-order point measurement of flow velocity, which is difficult with existing anemometers, using RTA is possible over a wide range of flow velocities.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Verification of flow velocity measurements using micrometer-order thermometers

Takegawa

Ishibashi

Iwai

et al. 2021

Sci Rep

Self Cite

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“…The National Metrology Institute of Japan (NMIJ) maintains high air speed standard and its calibration facility is capable of a relative expanded uncertainty (k = 2) of 0.63 % in the air speed range 40 m/s to 90 m/s [1]. The model equation for measurement uncertainty in the high air speed calibration wind tunnel, which is the working standard, employs a method that cancels out the density term of the fluid.…”

Section: Introductionmentioning

confidence: 99%

Uncertainty Evaluation of Fluid Density at High Air Speed Standard in NMIJ

Iwai¹,

Funaki²

2023

Proceedings of the 19th International Flow Measurement Conference 2022 on Flow Measurement - FLOMEKO 2022

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The National Metrology Institute of Japan (NMIJ) maintains high air speed standard and its calibration facility is capable of a relative expanded uncertainty (k = 2) of 0.63 % in the air speed range 40 m/s to 90 m/s. The model equation for measurement uncertainty in the high air speed calibration wind tunnel, which is the working standard, employs a method that cancels out the density term of the fluid. This is due to the fact that the density on the wind tunnel and DUT side is considered to be the same, i.e., the air speed values on the wind tunnel and DUT side are based on the same Bernoulli's principle. Therefore, the calibration environment of this standard is registered in the KCDB (CIPM MRA database) as ambient, which is independent of temperature and pressure changes throughout the year. However, there is a need to develop a calibration method for anemometers which are not based on Bernoulli's principle, as calibration targets. In this presentation, the reproducibility of air speed values in the wind tunnel is experimentally discussed, especially in the calibration environment, as the density of air changes throughout the year. In addition, the relative uncertainty of the density due to the difference of air density derivation formulas will be compared. Finally, the measurement uncertainty with the corrective coefficient of the anemometer under calibration due to the density change of air will be discussed.

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