A New Air Velocity Standard by Using LDV and a Wind Tunnel at CMS |
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| Cheng-Tsair Yang, Jeng-Yuan Chen, Jiunn-Haur Shaw |
- Abstract:
- Though air speed measurements are daily routine in many industries, calibration is still a problem due to the lack of standard. Though the Center for Measurement Standards (CMS) has established a calibration facility since 1997, the block effects resulted from small wind tunnel section constrained the devices to be calibrated. In this paper, a facility comprises a redesigned wind tunnel and a LDV with expanded lens was tested of its performance to estimate its uncertainty of measurement. Firstly, the expanded LDV probe was readjusted of its beam crossings and calibrated of its fringe spacing. This improved the uniformity of fringe pattern in the measuring volume to obtain accurate fringe spacing that serves as velocity coeficient and to reduce the uncertainty of LDV measurement to be less than 0.1%. The tunnel was tested under air speed from 0.5 m/s to 25 m/s. Turbulence intensity, long-term flow stability, and unifomity of velocity profiles are all considered as significant sources of measurement uncertainty. The uncertainty analysis indicated that the relative expanded uncertainty for regular calibration could be less than 0.5 %.
- Keywords:
- Air speed, LDV, Wind tunnel, Anemometry
- Download:
- IMEKO-TC9-2004-013.pdf
- DOI:
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