| Gas flow measurement plays an important role both in industry and in daily life.Especially with the implementation of the "West-East Gas Pipeline" project,gas flow measurement technology has received more extensive attention,and the demand for gas flow meters is gradually increasing.With the advancement of science and technology and the development of ultrasonic technology,ultrasonic gas flow meters with the advantages of non-contact,wide measurement range,high repeatability,and strong flow field adaptability have been widely used in various fields.However,due to various unfavorable factors in the gas flow measurement,including the complicated flow field environment,the installation effect of the velocity field distribution,the sensor manufacturing process,and the instability of the propagation signal,the development of ultrasonic gas flow measurement technology lags behind that of liquid flow measurement.Much.After studying the various factors that cause the measurement error of the ultrasonic gas flowmeter,this paper selects the pipeline flow field and flow conditioner flow field optimization for analysis and research.This subject takes the ultrasonic time difference flow measurement system as the research object,expounds the basic measurement principle of the time difference ultrasonic flowmeter,and summarizes the calculation ideas and technical methods of the CFD numerical simulation used in this article and the CFD numerical simulation method for pipeline flow field analysis Process.Perform theoretical analysis on the flow state of fluid in circular pipes under ideal conditions in laminar and turbulent conditions,and then use computational fluid dynamics(CFD)methods to model and model the pipelines with elbows and valves as chokes.CFD fluid simulation,through the analysis of its velocity cloud diagram and velocity curve to determine the influence of different flow blocks on the downstream flow field of the pipeline.Through the analysis of the rectification effect of the Etoile flow conditioner and the Laws flow conditioner on the pipeline flow field,the problem of the low-speed area in the central area of the blade flow conditioner and the error near the pipe wall was improved,and an optimized design was proposed.After optimization,Hollow blade flow conditioner.After that,simulations of installing Etoile flow conditioners,Lawsflow conditioners and newly designed flow conditioners were carried out on the pipelines with valves,and the downstream flow velocity distribution was analyzed,and the effect of improving the flow field after the installation of flow conditioners was studied.A standard experimental platform for gas ultrasonic flowmeters was constructed and tested on a DN50 gas ultrasonic flowmeter prototype independently developed by the teaching and research department.The Etoile flow conditioner,the Laws flow conditioner and the newly designed flow conditioner were tested on the elbows and valves.After processing and analyzing the results,it can be found that the relative error and repeatability of the measured flowmeter are greatly improved when three types of flow conditioners are installed,verifying its effectiveness in improving the flow field in the pipeline. |
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