Developing high temperature broadband fiber optic acoustic sensor with flat response

在火法冶金工业中，冶炼容器承受极端的热应力，以及化学和磨料反应。随着时间的推移，血管内壁遭受严重的退化。早期检测耐火衬里的退化是必不可少的，以避免突发的管道故障和防止意外停机。超声回波（AU-E）技术被广泛应用于冶炼容器耐火材料的降解和残余厚度的检测。该技术使用压电传感器（PZT）对容器外壳反射的信号进行手动冲击检测，以确定耐火衬里的剩余厚度。这些反射是由材料特性的局部变化引起的，如不同材料之间的避开或界面。对反射波进行时域和频域分析，以确定船舶的状况。然而，PZT检测系统具有单频能力的低灵敏度，因此需要手动冲击多个PZT以覆盖各种频率范围。这代表了公司特有的问题。该项目的主要目标是设计在宽频率范围内具有平坦响应的宽带声学传感器，其工作温度为bb0 - 300°C。随着平响应宽带声传感器的成功设计，我们将探索高温光纤涂层的选择，以获得高声响应。与Hatch公司合作，我们将开发一种超声波信号的发射器和接收器，能够产生和接收1 kHz - 250 kHz范围内的扫频脉冲（啁啾）（标准无损检测（NDT）声波发生器）。联合发射器和接收器单元将以最小的损失检测弱接收器信号。这一创新研究将在声学传感仪器和无损检测方面带来广阔的应用前景。

In the pyrometallurgical industry, smelting vessels are subjected to extreme heat stress, as well as chemical andabrasive reactions. The lining of the vessels suffer from severe degradation over time. Early detection ofdegradation in the refractory lining is essential to avoid sudden vessel failures and to prevent unscheduledshutdowns. The acoustic ultrasonic-echo (AU-E) technique is widely used to detect the refractory degradationand remaining thickness of smelting vessels. This technique uses a piezoelectric transducer (PZT) for manualimpact detection of the signal reflected from the shell of the vessels, in order to determine the remainingthickness of the refractory lining. These reflections are caused by local changes of material properties such asvoids or interfaces between different materials. The reflected waves are analyzed in both the time andfrequency domains to determine the condition of the vessels. However, the PZT detection system has lowsensitivity with single frequency ability, thus requiring manual impact with multiple PZTs to cover variousfrequency ranges. This represents the company-specific problem.The primary objective of this project is to design broadband acoustic sensors with a flat response over a broadfrequency range, that operate at temperatures >300°C. Following the successful design of the flat-responsebroadband acoustic sensor, we will explore the option of high-temperature fiber coating for high acousticresponse. In collaboration with Hatch Ltd., we will then develop a transmitter and receiver for ultrasonicsignals, capable of generating and receiving a frequency sweep pulse (chirp) in the 1 kHz - 250 kHz range (astandard non-destructive testing (NDT) acoustic generator). The joint transmitter and receiver unit will detectthe weak receiver signal at minimal loss. This innovative research will lead to promising applications inacoustic sensing instrumentation and NDT detection.