Enhancement of CFD-based external gas straightener optimization for pipe bending

Abstract In this study, an optimisation strategy for an external gas straightener is proposed to address the lack of measurement accuracy of ultrasonic flowmeters under complex flow field conditions in the natural gas market. In view of the space limitation of the built-in straightener, a computational fluid dynamics (CFD) approach, combined with theoretical analysis and experimental validation, was used to monitor the performance of the flowmeter in detail under minimum and maximum flow conditions. On this basis, an external gas straightening device applicable to the bends at the front end of the flowmeter was designed and optimised, and the key parameters of the device were finely tuned by comparing the evaluation indexes such as relative error E, relative standard error CV and uniformity index. The optimised parameters were determined to be: front and rear baffle diameters of 25 mm, a primary rectification bundle of 10 mm, and a secondary rectification bundle of 12 mm. The validation results show that the optimised solution reduces the measurement error to 0.027% while significantly improves the measurement repeatability in the low flow region to 0.05, all of which meet the international standard requirements. In addition, the study also confirmed the stability of the scheme on the flowmeter performance under different temperature and pressure environments, effectively improving the measurement accuracy of the flowmeter.