明渠含沙水流流量测量精度分析——以超声时差法测流为例

Flow measurement accuracy of sediment-laden open channel flowstaking time-difference ultrasonic flowmeters as examples

水流中泥沙的存在对流量测量精度的影响一直是水力学的重要问题。本文以超声时差法测流方法为例,在室内明渠水槽中开展了不同含沙量(最大含沙量27 kg·m^(-3),宁夏引黄灌区天然沙,中值粒径0.015 mm)对流量测量精度的影响测试研究,以电磁流量计及巴歇尔槽测量值为基准,对比了超声时差法在不同含沙量下的流量测量偏差,分析了含沙量对其流量测量精度的影响。结果表明:在含沙条件下,超声时差法的流量测量值总体偏大,且偏差量随含沙量增大呈增大趋势。多声路箱式超声时差流量计受含沙量影响相对较小,在本文泥沙粒径、含沙量范围内平均意义上流量测量偏差在7%;单声路超声时差流量计受含沙量影响较大,在本文测验环境下其在含沙量较高时测量值偏大300%~500%,基本处于失效状态。

The influence of sediment on the flow measurement accuracy is an important problem in hydraulics.In this study,taking time-difference ultrasonic flowmeters as examples,the potential sediment influence on their measurement accuracy in sediment-laden open channel flows was investigated based on indoor experiments at different sediment concentrations(0~27 kg·m^(-3),natural sand from the Yellow River irrigation district in Ningxia with medium particle size of 0.015 mm was used).The flow measurement errors were quantified and compared against the benchmark devices of sediment insensitive pipe electromagnetic flowmeter and Parshall flume.The results indicate that ultrasonic flowmeters overestimate the flowrate and the deviation increases with sediment concentration.In the concentration range of our study,the multi-channel box-type ultrasonic flowmeters are insensitive to the sediment concentration and suffer a maximum deviation of 7%,while the single-channel measurements are very poor with a deviation up to 300%-500%under the influence of sediment.