| In recent years, more and more projects about natural gas used for heating and refrigeration are increasing greatly in cities of China since the "West-East Gas Transport Project" was carried out. Meanwhile, with the development of national economy, natural gas is widely used in metallurgy and chemical engineering. The improvement of gas flow measurement technology is being paid more and more attention to. Due to their plenty of advantages, such as wide range ration, low pressure loss, high precision and high adaptability of flow field, multipath ultrasonic gas flowmeters (USF) are playing a very important role in the field of gas flow determination. However, domestic researches on USF started late and fall behind so far in spite of their enormous demands. Therefore, the independent research and development of USF is of great strategic significance.Despite USF’ plenty of advantages, many restrictive factors causing errors exist, including complex flow field, serious signal attenuation and unstable detection which can be summarized into two aspects:the changes in velocity profiles due to installation effects and signal attenuation in transmission and processing. This paper focuses on the key technologies of USF flow field compensation. An algorithm based on regression analysis is proposed and finally verified for its high adaptability and high precision. The contents are as follows:1) Research on the theories of flow field compensation algorithm. In the second chapter, the definition of flow field compensation is illustrated and some typical algorithms are introduced. Finally an algorithm based on regression analysis is proposed.2) Research on flow field compensation algorithm based on numerical simulation. In the third chapter, influence on measurement due to the complex flow field environment is discussed by analyzing the simulation results of the three-dimensional double bend pipes. Finally, the flow field compensation algorithm based on regression analysis is proved to be effective in improving measurement accuracy.3) Research on the effect of installation effects on flow field compensation algorithm. In the fourth chapter, adaptability of flow field under different pipes is discussed. What’s more, the effect of coaxial error on flow field compensation algorithm is explored. Finally, as the key study object, installation effects of transducer which directly affects measurement accuracy of channels are discussed.4) Research on flow field compensation algorithm based on experimental verification. In our experiment, it is proved to be effective in improving measurement accuracy through the flow field compensation algorithm based on regression analysis. By comparing with the conventional algorithm, it indicates that the algorithm based on regression analysis has more advantages in improving measurement accuracy. |
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