Ultrasonic flowmeter is a velocity flowmeter, and its measurement accuracy is greatly affected by the flowfield in the pipeline. In the actual use process, due to the installation conditions are not ideal, the formation ofvortex flow, pulsating flow, asymmetric flow and other non-ideal flow field in the pipe, which in turn affects the accuracy of ultrasonic flowmeter. This study is based on CFD numerical simulation technology, 90° elbow, reducer, upstream and downstream flange diameter difference of one level and other typical disturbanceelements on the impact of the flow field in the pipe, simulate the flow field of the gas in the closed pipe after the disturbance elements, and calculate the resulting error, found that the impact of each disturbance element on the ultrasonic flowmeter measurement error increases with the increase in operating flow. For 90° elbow, the upstream and downstream flange diameter differ by one level, we use these two installation conditions to carry out real flow test, through the test data and simulation results for comparison and analysis, the results are consistent. At the same time, the use of experimental data on the simulation model correction, can guide the construction and transformation of ultrasonic flowmeter metering process, improve the accuracy of the measurement results, and effectively maintain the fairness of the trade handover.

With the ultrasonic flowmeter (Ultrasonic Flowmeter) in the natural gas metering is widely used, ultrasonic flowmeter accuracy is increasingly concerned. however, by the limitations of the calibration operation conditions, there aredifferences between the calibration operation conditions and actual operation conditions , and operation conditions on theimpact of ultrasonic flowmeter metering lack of systematic research, Wuhan branch station established a mobile natural gas metering standard device can be carried out in different pressure conditions of the gas transmission station calibration services.In this paper, we study the calibration tests carried out by the mobile natural gas metering standard device at different pressures, and through analyzing and integrating data, we derive the metering deviation caused by ultrasonic flowmeter under different working conditions, establish the mathematical model of Reynolds number error correction toguide the use of ultrasonic flowmeter, and eliminate the deviation introduced by the different operation conditions of calibration and use, improve the accuracy of trade measurement, while the research results can be the technical support for the revision of relevant standards and norms.

Flow measurement plays an important role in industrial production, process control and energy utilization. The steam flow is affected by the state of steam properties and the design of the steam flowmeter during the measurement process, resulting in low measurement accuracy. Based on the combined measurement method of differential pressure flowmeter and vortex flowmeter, an integrated flow measurement device that integrates averaging-velocity tube and piezoelectric vortex flowmeter is proposed in this paper. It combines the structural features and advantages of the two flowmeters scientifically. In this paper, the differential pressure transmitter is used to detect the pressure difference on both sides of the cylinder. Due to fluid vibration and piezoelectric effect, the probe in the device generates regular vibration. And combined with Digital Signal Processing (DSP) technology and automatic frequency band adjustment method, the flexibility and stability of frequency signal processing are improved. The measurement performance of the device was evaluated in this paper. The experimental results show that the absolute value of the relative error of the device is within 1.00 % and 1.50 % under the conditions of single-phase water and single-phase gas, respectively. The device can achieve dual-signal measurement, and it has the advantages of wide applicability, good stability and strong anti-interference, which will provide a new design idea for the measurement of saturated wet steam.

Slug flow is a common flow pattern, which is often accompanied by undesired effects, like pressure loss or vibrations, leading to large errors in multiphase flow metering. Because these undesired effects strongly correlate with the frequency of slug occurrence, this parameter is of special interest. In this paper, different slug frequency calculation methods are applied to data from multiphase flow simulations and corresponding high-speed video observations for six test cases within the plug / slug flow regime. Commonly used methods, like power spectral density (PSD) or calculating the mean slug frequency by applying a fixed threshold, are compared with new evaluation methods. Since every approach has its pros and cons, it is recommended to apply different methods to each data set. The deviations in the resulting slug frequencies indicate how much one can trust the results. If large variations are observed, one should apply an advanced technique for the calculation of the liquid level / hold-up, which takes aeration into account.

The main sources of domestic pipeline natural gas are central Asia, the Tarim Basin, the Sichuan Basin, and the Zhonghai Oil and Gas Field, etc. Due to the large geographical differences in gas sources, the components of natural gas are quite different. Therefore, accurate analysis of natural gas composition and calculation of the corresponding compression factor is an important part of the natural gas custody transfer process. There is a certain proportion of neopentane in current domestic natural gas, but there are no calculation parameters of neopentane in various corresponding calculation standards, including GB/T 17747/ISO 12213 and AGA 8 standards for compression factor calculation and GB/T 30491.1/ISO 20765-1 and AGA10 standards for sound velocity calculation. However, in theory, the treatment method of neopentane will directly affect the compression factor of natural gas, and then affect the measurement results. Therefore, how to deal with neopentane in natural gas and ensure the accuracy of natural gas measurement results is a problem worthy of study.
Generally, there are three ways to deal with neopentane in natural gas: (1) adding neopentane content to isopentane with similar properties; (2) adding neopentane content to n-pentane; (3) to normalize the neopentane content. In order to confirm the influence of the three different processing methods on the measurement accuracy of the flowmeter, the theoretical calculation and actual test verification are used for comparative analysis. The conclusions are as follows: The three treatment methods of neopentane have a certain influence on the calculation results of natural gas compression factor, but the overall influence is small. For the common components of domestic pipeline natural gas, the standard meter method and critical flow Venturi nozzle method standard devices are used to verify the tested flowmeter respectively. The maximum deviations of natural gas compression factor and indication error are 0.00001 and 0.00003 %, 0.00001 and 0.00301 %, respectively, namely, the different treatment methods of neopentane have little impact on the measurement results. Therefore, as an inherent component of natural gas, neopentane can be treated in the above three ways in trade measurement.