论文部分内容阅读
1 引言 使用夹合式超声波流量计进行高精度的测量必须正确地掌握超声波的传播路线。该传播路线由斯涅尔定律确定,探头则必须精确地安装在相应位置上。但是,棱镜或流体的温度发生变化时,声速也发生变化,因而声波传播路线就与初始设定的路线有所不同。这种由于偏离初始设定的路线而产生的误差,过去是通过引入折射角修正而进行校正的。但是,近年来要求测量水以外的流体即测量声速未知的流体日益增多,在这种情况下要确定声波的传播路线和折射角修正就不那么容易。对此,虽已经报道过几种解决办法,但误差都比较大,而且需要多次计算。为克服这些问题,我们提出了一种使用宽波束探头的新式超声波流量计。使用本方法,超声波波束大体上可以看成是平行的,因而可以得到迄今还不曾有的若干优点。这种宽波束超声波流量计的优越性已在理论和实验上得以确认,以下作一说明。
1 Introduction Using a clamped ultrasonic flowmeter for high-precision measurements must accurately grasp the ultrasonic propagation path. The propagation path is determined by Snell’s law and the probe must be precisely mounted in place. However, when the temperature of the prism or fluid changes, the speed of sound changes, so that the sound wave propagation path is different from that of the initial setting. This error due to deviating from the initially set route was corrected in the past by introducing a correction of the refraction angle. However, in recent years, there has been an increasing demand for fluids other than measuring water, that is, fluids of unknown sound velocity, in which case it is not easy to determine the propagation path of sonic waves and the correction of the angle of refraction. In this regard, although several solutions have been reported, the errors are relatively large and require multiple calculations. To overcome these problems, we propose a new ultrasonic flowmeter using a wide beam probe. With this method, the ultrasound beams can generally be seen as parallel and thus several advantages that have not heretofore been obtained. The advantages of this wide-beam ultrasonic flowmeter have been confirmed theoretically and experimentally, and the following is a description.