| Abstract: | A novel vortex flowmeter by using pressure sensors and improved convection velocity estimation was proposed to extend the lower operation range of flowrate. The two sensors were mounted on the positions of 0.2D45° and 1.0D45° according to the signal strength and vortex wavelength criterion. The high-frequency pressure sensors were designed to acquire the undistorted signals of vortex-induced pressure fluctuation and further compute the vortex convection velocity. Aiming at the problem of multiple peaks in cross-correlation calculation, a modified transit time estimation technique combined with a moving-average-filter-based cross correlation function were introduced and verified by the tests. Then, the mean convection coefficient was obtained and the performance of the transit-time-based method was analyzed and compared with that of the frequency-based method. It indicated that the novel vortex flowmeter is robust at low Reynolds number range, which achieves a turndown ratio of 8:1 with an accuracy of ±2% in the Reynolds number range from 1.53×104 to 1.23×105. A remarkable improvement of turndown ratio is achieved compared to the original frequency-based method of 3:1. The proposed system of pressure sensors shows good prospect for the gas metering in small pipes due to the feature of non-invasion and sufficient high frequency response. |
