| 内容提要: |
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 0.2D45o and
1.0D45o 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 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 |