Study Of The Metering Model And Metering Technology Of Wet Gas Based On Slotted Orifice

Metering Technology for Condensate Natural Gas belongs to the metering problem forhigh gas content gas-liquid two phase flow, and this problem has not been well solved yet.The lack of reasonable metering technology of Condensate Natural Gas has restricted thedevelopment of the natural gas industry, and this problem is urgent to be solved. This thesis isbased on the idea of using the slotted orifice to meter condensate natural gas, and study thecharacteristics of slotted orifice applied to Condensate Natural Gas metering according to thepreliminary study of the research group and a large number of experimental data. The study isaiming at improving measurement model to expand the measuring range of the flowmeter andto improve measurement accuracy, and lay the foundation for the improvement of condensatenatural gas metering algorithm based on the slotted orifice.This study can be divided into three parts. In the first part the de-noising problem ofpressure drop data has been studied to improve the signal. And the second part is the mainpart of the study, which explored pressure drop structure of slotted orifice for annular flowfrom the point of mechanism, and established a semi-empirical model. In the third part,characteristics of two-phase pressure drop multiplier for slotted orifice were studied.According to the non-stationary and fractal characteristics of the pressure drop data, andthe difficulty to obtain the priori knowledge of noise, a new de-noising method based on thethreshold of EMD was selected in this article to solve this problem. The fractal Gaussiannoise is adopted as the noise model in the test study, and the algorithm was optimized basedon the test results to make it better in handling fractional Gaussian noise.To further improve measurement accuracy of slotted orifice depends on the accuracy ofthe measurement model. But the lack of support from the theoretical model is a decisivefactor in restricting the accuracy of the measurement model. This thesis explored themovement mechanism of the annular flow through the slotted orifice, and divided pressuredrop into acceleration pressure drop, frictional pressure drop and the partial pressure drop.And a pressure drop semi-empirical model was obtained according to the theory andexperimental data, which turned out to be successful. The research of pressure drop multiplier has been an important direction for themeasurement technology of gas-liquid two-phase flow with differential pressure flowmeter,but the replicability issue of the correlations remains unresolved. This thesis summarized theexisting pressure drop multiplier correlations of standard throttling component and slottedorifice, and the characteristics of pressure drop multiplier for slotted orifice has been analyzedbased on the actual experimental data. A new correlation was obtained which is correlated byLM parameters, gas Froude number and the beta ratio, and the correlation achieved goodresults.