The experiments on an ultrasonic flowmeter with 100mm diameter were carried out, including reference experiments, upstream 90° single bend and double bends experiments with different upstream straight pipe lengths. The results were analyzed and discussed from the viewpoint of flow field distribution based on numerical simulation. The results show that when the upstream and downstream straight pipe length is certain, the meter factor increases at first and stays unchanged basically with the flow increased. The linearity is mainly affected by low flow. The 90° single bend and double bends in front of the flowmeter disturbs the flow field distribution after the bend. The flow field behind the double bends is more complex so the flow measurement performance of the flowmeter is more affected. In order to ensure the relative error of the average meter factor less than ± 0.5%, the minimum straight pipe length in front of the flowmeter is respectively 20D and 30D under the installation of 90° single bend and double bends.
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