Designing and characterizing a multi-stepped ultrasonic horn for enhanced sonochemical performance

The commonly used ultrasonic horn generates localized cavitation below its converging tip resulting in a dense bubble cloud near the tip and limiting diffusion of reactive components into the bubble cloud or reactive radicals out of the bubble cloud. To improve contact between reactive components, a novel ultrasonic horn design was developed based on the principles of the dynamic wave equation. The horn, driven at 20 kHz, has a multi-stepped design with a cone-shaped tip increasing the energy-emitting surface areas and creating multiple reactive zones. Through different physical and chemical experiments, performance of the horn was compared to a typical horn driven at 20 kHz. Hydrophone measurements showed high acoustic pressure areas around the horn neck and tip. Sonochemiluminescence experiments verified multiple cavitation zones consistent with hydrophone readings. Calorimetry and dosimetry results demonstrated a higher energy efficiency (31.3%) and a larger hydroxyl radical formation rate constant (0.36 μM min⁻¹) compared to typical horns. In addition, the new horn degraded naphthalene faster than the typical horn tested. The characterization results demonstrate that the multi-stepped horn configuration has the potential to improve the performance of ultrasound as an advanced oxidation technology by increasing the cavitation zone in the solution.     

分布反馈式光纤激光水听器拖曳线列阵实验研究

为了进一步增大光纤拖曳阵的探测距离,研制了缆径为16mm的32元分布反馈式光纤激光水听器拖曳线列阵.阵元在10~2 000Hz频率范围内的平均声压灵敏度为-142.7dB(re 1rad/μPa),波动幅度小于±2dB.基于声光调制器的时分、波分联合复用技术实现了32元光纤激光水听器的多路复用,各个阵元之间以及各个通道之间的串扰均小于-40dB,并完成了静态和动态拖曳湖上实验.实验结果表明,研制的32元分布反馈式光纤激光水听器拖曳线列阵无论是在静态,还是在6~16节的动态拖曳状态,都能对目标形成稳定的波束指向,与GPS轨迹记录完全一致,展现了分布反馈式光纤激光水听器拖曳线列阵在工程上的应用前景.     

基于流固耦合作用的分布反馈式光纤激光水听器

为了解决流固耦合模态使水听器工作频带变窄的问题,理论分析了流体对双膜片结构的分布反馈式光纤激光水听器固有频率的影响,基于有限元软件对水听器加固封装前后在空气中和流体中的模态和频响性能进行仿真分析,加工制作了水听器原型样品并开展了水声实验研究.实验结果表明,在2 500~8 000Hz的频率范围内,未经加固封装的水听器由于在该频段内存在多个流固耦合固有频率造成响应曲线起伏较大,而采取了加固措施封装后的水听器获得了-142.77±0.8dB的平均声压灵敏度,验证了流体对水听器频响性能的影响以及改善措施的有效性,实验结果与理论及仿真结果吻合较好.     

Combining COMSOL modeling with acoustic pressure maps to design sono-reactors

Scaled-up and economically viable sonochemical systems are critical for increased use of ultrasound in environmental and chemical processing applications. In this study, computational simulations and acoustic pressure maps were used to design a larger-scale sono-reactor containing a multi-stepped ultrasonic horn. Simulations in COMSOL Multiphysics showed ultrasonic waves emitted from the horn neck and tip, generating multiple regions of high acoustic pressure. The volume of these regions surrounding the horn neck were larger compared with those below the horn tip. The simulated acoustic field was verified by acoustic pressure contour maps generated from hydrophone measurements in a plexiglass box filled with water. These acoustic pressure contour maps revealed an asymmetric and discrete distribution of acoustic pressure due to acoustic cavitation, wave interaction, and water movement by ultrasonic irradiation. The acoustic pressure contour maps were consistent with simulation results in terms of the effective scale of cavitation zones (∼10 cm and <5 cm above and below horn tip, respectively). With the mapped acoustic field and identified cavitation location, a cylindrically-shaped sono-reactor with a conical bottom was designed to evaluate the treatment capacity (∼5 L) for the multi-stepped horn using COMSOL simulations. In this study, verification of simulation results with experiments demonstrates that coupling of COMSOL simulations with hydrophone measurements is a simple, effective and reliable scientific method to evaluate reactor designs of ultrasonic systems.     

低加速度灵敏度水听器

本文介绍了一种用于拖曳线列阵声呐的压电陶瓷型水听器，我们在提高水听器工作稳定性与可靠性，并确保水听器有较高接收灵敏度的前提下，进行了水听器的结构方案优化设计，以降低水听器的加速度灵敏度，研制的水听器接收灵敏度为－１９３ｄＢ，在２０－１０００Ｈｚ频段内灵敏度起伏为１．２ｄＢ，加速度灵敏为－７０ｄＢ。     

MEMS压电水听器和矢量水听器研究进展*

基于微电子机械系统制造技术的MEMS压电水听器和矢量水听器具有小型化、低功耗、低成本、易成阵、无源、噪音低等优点。对基于ZnO薄膜的MEMS水听器和矢量水听器进行了研究,测试结果表明,硅微压电水听器的灵敏度为-192 d B(ref.1 V/μPa),基本达到实用化的要求。MEMS压电矢量水听器等效声压灵敏度为-229.5 d B(ref.1 V/μPa),比同类型压阻式MEMS矢量水听器的灵敏度高17 d B,但还未达到实用化要求。为了进一步提高MEMS矢量水听器的灵敏度,设计了具有U形槽的压电复合悬臂梁结构和电极串联结构,采用具有更高压电系数的掺钒ZnO薄膜作为压电层,并对MEMS制备工艺进行了改进,有望显著提高MEMS矢量水听器的灵敏度。     

单模光纤水听器声压灵敏度的研究

光纤水听器是-种新型的声信号探测器。声压灵敏度是它的重要技术指标。70年代末,Peter和Price等人提出了声光转换的理论模型,Price导出了单模光纤水听器的声压灵敏度公式。本文,根据弹性振动理论和光弹理论,对Price公式加以推广,导出了宽频带中适用的新的声压灵敏度公式,并指出Price公式只是新得出的公式在低频声信号下的表达式。     

灵敏度可调式压电薄膜水听器

本文介绍一种灵敏度可调式压电薄膜水听器，采用PVDF薄膜作为换能材料，聚碳酸脂作为背衬，薄膜粘贴在背衬的内壁，软性的背衬在声压的作用下形变。从而带动薄膜形变，产生电信号输出。水听器内装有前置放大器，调节放大器的负载电阻可调节水听器的灵敏度，灵敏度变化范围为出，水听器内装有前置放大器，100Hz-16kHz。     

Sagnac效应在光纤水听器中的应用

本文介绍了由Sagnac效应组成的光纤水听器原理，着重推导了声压作用下的光纤水听器的相位变化关系．并在此基础上对比了Sagnac光纤水听器与Mach-Zehnder光纤水听器，结果表明Sagnac光纤水听器在低频段的灵敏度及其实现的简易性上具有很大优势．     

基于球形压电陶瓷的耐压水听器

利用球形压电陶瓷自身所具有的耐压能力,采用径向极化空气背衬压电球壳换能器作为声学接收敏感元件,设计并制作了一种球形耐压水听器。首先对其低频开路接收灵敏度和谐振频率等声学特性进行了分析和有限元仿真,然后对其强度和稳定性等耐压性能进行了分析和有限元仿真,最后对其声学性能和耐压能力进行了测试。测试表明,该球形耐压水听器的直径为36 mm,工作频段为50 Hz～10 kHz,低频接收灵敏度为-198.4 dB (0 dB=1 V/μPa),等效自噪声谱级为46.5 dB@1 kHz,其耐压深度可达3000 m。该耐压水听器为大深度水听器设计提供了参考,在深水声学领域具有重要的应用价值。