Phase-frequency characteristic based measurement of sodium flow rate using PMSF with embedded bluff body

Abstract Permanent magnet sodium flowmeters (PMSFs) have been widely used to measure the sodium flow. However, due to the effects of irradiation, thermal cycling, time lapse, etc., the magnetic flux density of the PMSF will decrease, which affects the measurement accuracy of the flowmeter. Therefore, it must be calibrated regularly. Since the flowmeters are immersed in sodium, they have to perform in-situ calibration. In-situ calibration methods include the cross-correlation function analysis method, impulse response function method and adaptive modeling method. In order to further improve the measurement accuracy of the in-situ calibration at low flow rate, a phase-frequency characteristics method is proposed, and the slope fitting and time delay averaging implementation are present. The experimental results show that the measurement accuracy is 1.0 level when the flow velocity is above 0.3 m/s, and 2.0 level when the flow velocity is in the range of 0.2–0.3 m/s.