Error analysis of gas and liquid flow rates metering method based on differential pressure in wet gas

摘要

Online measurement of gas and liquid flow rates in wet gas is of great significance in industry. When the differential pressure meter is used to measure the gas and liquid flow rates, an over-reading correlation is needed to correct the liquid-induced overestimation of the gas flow rate and an auxiliary correlation is needed to obtain the liquid fraction or flow rate. With the two correlations incorporated, the gas and liquid flow rates can be calculated. In the present study, error analysis of this metering method is conducted. The results demonstrate that metering methods based on differential pressure exhibit similar error pattern, i.e., the prediction error of gas phase is small while that of the liquid phase is large. This phenomenon can be interpreted by error propagation and the underlying physics is that the two-phase differential pressure is mainly dependent on the gas phase but insensitive to the liquid phase. It is found that both the mean value and the fluctuation of the differential pressure signals are able to reflect flow rate changes of wet gas flow. However, metering methods based on the differential pressure fluctuation present larger prediction errors than that based on the differential pressure mean value. The reason is that the differential pressure fluctuation has much poorer repeatability compared with the differential pressure mean value. (C) 2016 Elsevier Inc. All rights reserved.