中文摘要：

超声波流量计应用于小管径时，在基表内部加装反射装置，延长声程，提高测量精度。反射装置对超声波流量计基表内水流特性影响较大，为了优化表内水流特性，本文针对u型反射的特点提出两种改进措施：反射柱上部削平部分和在此基础上加装导流片。利用SST肛（1）模型，对3种基表内水流特性进行数值模拟，分析3种基表内流场分布、声道流速稳定性和压力损失。结果表明，反射柱上部削平部分没有改善流场分布，而在此基础上加装导流片流场明显得到改善，同时两者均增加了声道流速稳定性和减小了压力损失，但后者效果更为显著。

英文摘要：

The reflection device is fixed in ultrasonic flowmeter to extend sound path when the diameter of the measuring tube is small due to high measurement precision. Because of its great influence on the flow characteristics, two improvement approach, removing the part of the upper tip and adding deflector on the basis of above, have been proposed to optimize the structure of flowmeter and numerically simulated by SST K-co model to analyze the flow field distribution, velocity stability of sound path and pressure loss. The results show the latter one of two modifications can improve the distribution of flow field compared to the other. Meanwhile, both of two can increase the stability of velocity in sound path and reduce the loss of pressure but the latter effect is more significant.