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A Method for Testing Influence of Flow Field Disturbance on Ultrasonic Gas Meters
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摘要: 针对气体在管道内不同剖面上的流速分析，流速与截面位置相关, 超声波通过测得气体的平均流速计量累计体积，流场扰动直接影响管道中的气体流速分布，影响计量准确性。实际安装使用时，燃气表会受到两种类型的流场扰动，即速度分布畸变和漩涡。介绍这两种流场扰动的测试方法，重点论述扰动发生器的结构、安装以及误差算法。以1.5级G6膜式燃气表为例，用0.5级音速喷嘴法气体流量标准装置测试10 m3/h流量下的流场扰动影响，影响量<0.1%。基于膜式燃气表不受流场扰动影响，验证该方法的可行性与算法的准确性，为验证超声波燃气表适应流场扰动提供评价方法，有助于超声波燃气表在流道设计及优化时取得比较完整、准确的测试数据，提升产品质量。对G6超声波燃气表测试数据分析的结果表明，其易受流场扰动影响，在qmax流量入口侧扰动引起的误差变化为0.30%，大于出口侧的0.11%，且与流量相关；在0.2qmax处流量基本不受影响。在研发设计时需重点考虑流场优化，提升抗流场扰动影响能力。Abstract: According to the analysis of gas velocity in different sections of a pipeline, the velocity is related to the position of the section. Ultrasonic gas meters measure the cumulative volume by measuring the average velocity of the gas. Flow field disturbance affects the gas velocity distribution in the pipeline and the measurement accuracy. A gas meter is disturbed by two types of flow fields, namely velocity distribution distortion and vortex. This paper proposes a test method for two kinds of flow field disturbance, and focuses on the structure, installation and error algorithm of the disturbance generator. Taking the 1.5 grade G6 diaphragm gas meter as an example, a 0.5 stage sonic nozzle method gas flow standard device was used to test the influence of flow field disturbance under the flow rate of 10 m3 / h. The influence was less than 0.1%. Given the fact that diaphragm gas meters are not affected by flow field disturbance, the feasibility of the method and the accuracy of the algorithm were verified, providing an evaluation method for verifying the adaptability of ultrasonic gas meters to flow field disturbance. It can be used to obtain more complete and accurate test data of ultrasonic gas meters in design and optimization of flow channels, leading to better product quality. The test data of the G6 ultrasonic gas meter showed that it was easily affected by flow field disturbance. The change in the error caused by the disturbance on the inlet side at the flow rate of qmax was 0.30%, greater than the change of 0.11% on the outlet side, and the changes were related to the flow rate. This effect was insignificant at the flow rate of 0.2qmax. In the design of a product, the flow field should be optimized to reduce flow field disturbance.
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Key words:
- ultrasonic gas meter /
- gas meter /
- flow field disturbance /
- indication error /
- disturbance generator
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表 1 G6膜式燃气表测试未修正误差
Table 1. Uncorrected error of the G6 diaphragm gas meter
流量（m3/h） 扰动方式 压损（Pa） 误差（%） 偏移量（%） 10 无 230 0.30 入口 833 0.82 0.52 出口 822 0.26 0.02 
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表 2 G6超声波燃气表测试修正后误差
Table 2. Corrected error of the G6 ultrasonic gas meter
流量（m3/h） 扰动方式 压损（Pa） 误差（%） 偏移量（%） 10 无 132 0.74 入口 601 0.44 −0.30 出口 580 0.85 0.11 2 无 32 0.18 入口 70 0.13 −0.05 出口 68 0.10 −0.08
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