Developing high temperature broadband fiber optic acoustic sensor with flat response

在火法冶金工业中，熔炼容器经受极端的热应力以及化学和磨损反应。随着时间的推移，船只的衬里会严重退化。早期检测耐火衬里的劣化对于避免容器突然失效和防止意外停机至关重要。声学超声回波（AU-E）技术被广泛应用于检测冶炼容器的耐火材料劣化和残余厚度。该技术使用压电传感器（PZT）对从容器壳体反射的信号进行手动冲击检测，以确定耐火衬里的厚度。这些反射是由材料特性的局部变化引起的，例如不同材料之间的空隙或界面。在时域和频域中分析反射波以确定船只的状况。然而，PZT检测系统具有低灵敏度和单频率能力，因此需要手动冲击多个PZT以覆盖各种频率范围。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传感器，工作温度>300°C。在平坦响应宽带声传感器的成功设计之后，我们将探索高温光纤涂层的选择，以获得高的声学响应。与Hatch Ltd.合作，然后，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。这一创新性的研究将在声学传感仪器和无损检测中产生有前途的应用。

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.