Zhang Qiang, Xu Ying, Zhang Tao
Wet Gas Flowrates Metering Based on Double Differential Pressures of Venturi Meter
In order to measure the wet gas not separating, a wet gas measuring method based on double differential pressures of an alone venturi meter is presented in this study. In traditional over-reading (viz. OR) correlations, only the liquid phase fraction is known, can the OR be solved. This deficiency is analyzed by error propagation method theoretically. The change characteristics and the inherent physics laws of the differential pressures of the contraction and expansion sections of a venturi tube which were affected by the relative amount of liquid phase and gas flow rates were investigated deeply. Using a new dimensionless metering parameter, viz. the differential pressures ratio of contraction and expansion sections of venturi tube, a novel form of the OR correlation was, therefore, developed to improve the metering accuracy effectively. The gas and liquid flowrates of wet gas were solved respectively by iterations. Taking a prototype with DN80 diameter of 0.38 beta ratio designed and made for example, with the experimental devices of the wet gas flow measurement, the experimental research and the performance verification of the prototype was carried out in the flow laboratory of TianJin University. The experimental results show that the relative error of gas flow rates is less than ± 2 %, and the full scale error of liquid flow rates is less than ±10 %, under the condition like the test pressure range from 0.1~0.16 MPa, Froude number range from 0.4 ~ 0.7, mass ratio of liquid and gas range from 0 ~ 1.
