In the 9th International Symposium on Ultrasonic Doppler Methods for Fluid Mechanics and Fluid Engineering, Noriyuki Furuichi presented a study on the influence of obstacle plates on the uncertainty of flowrate measurements using the ultrasonic Doppler method. The research was conducted at the National Metrology Institute of Japan (NMIJ) using the national standard calibration facility of water flowrate.
The experiment aimed to generate a distorted flow by installing obstacle plates at the upstream of the test section. The flowrate measurement was based on multi-path measurement using three transducers. The study found that the maximum difference from the reference flowrate was over 2% when the measurement was performed at 8D downstream of the obstacle plate. However, at 25D downstream of the obstacle plate, the deviation was within the fundamental uncertainty level.
The UVP-Duo, a measurement equipment made by Met-Flow sa, was used to measure the velocity profile. The measurement paths were changed in sequence using the multiplexer installed in the measurement equipment. The measurement interval of the velocity profile at each path was approximately 350 msec, and the number of samples depended on the flowrate, ranging from 610 to 1070. The channel distance was 1.48 mm.
The research concluded that the uncertainty caused by the upstream condition is negligible for 25D downstream from the final disturbance. However, it is estimated to be 2.7% for 8D. The study also showed that the uncertainty of the influence of upstream pipe layout could be obtained through several parametric experiments.
In conclusion, the study provided a practical uncertainty analysis for the flow-metering method using the ultrasonic Doppler method. It discussed in detail the influence of the upstream condition and the number of measurement paths on the uncertainty of the flowrate measurement. The research also highlighted the importance of the UVP-Duo in accurately measuring the velocity profile in such experiments.
An Influence of obstacle plate for uncertainty of flowrate measurement using Ultrasonic Doppler Method