Multi-mode coupled vibration performance analysis of a radial-longitudinal (R-L) ultrasonic transducer

Study on the vibration performance and sound field of a novel push-pull ultrasonic transducer with slotted tube

To address the challenges in ultrasonic processing for large capacity liquids, improving the electroacoustic conversion efficiency, expanding the radiation direction, and enhancing the uniformity of the sound field have become imperative and focal objectives in the design of high-power ultrasonic transducers. Hence, a novel push-pull slotted tube ultrasonic transducer (PSTUT) based on longitudinal-bending mode conversion has been proposed. The PSTUT is composed of four key parts: two sandwich transducers, two stepped horns, two end caps, and a slotted tube radiator. By applying push-pull longitudinal excitation, the caps produce longitudinal bending vibration, while the arc-shaped plates produce radial bending vibration, capable of achieving efficient, uniform, and omnidirectional ultrasound radiation. Based on the principle of electromechanical analogy and the theory of Timoshenko beams, the electromechanical equivalent circuits of the uniform beam in bending vibration and the PSTUT in coupled vibration are established. The frequency response of the PSTUT is validated by the finite element method simulations and experiments. The vibration analysis demonstrates that adjusting the size of the circular slotted tube radiator can control both the range and intensity of radial radiation. Simulated and experimental results show that the PSTUT exhibits satisfactory 3D-omnidirectional radiation capability and improved sound field uniformity in water. The proposed PSTUT offers a promising solution to overcome the bottleneck in ultrasonic liquid treatment technology.

Acoustic black hole ultrasonic radiator for high-efficiency radiation

The utilization of conventional longitudinal transducers in the field of ultrasonic liquid processing is constrained by limitations in radiation area and directional characteristics. These limitations can be addressed through the implementation of mode conversion techniques. However, an expanded radiation area may also result in reduced acoustic radiation intensity. To mitigate this issue, this study proposes an Acoustic Black Hole Ultrasonic Radiator (ABHUR) designed to enhance ultrasound intensity and thereby achieve high-efficiency radiation. The proposed ABHUR comprises a Bolted Langevin-type Transducer (BLT) and a Curved Acoustic Black Hole (CABH) ring. A theoretical model, based on the transfer matrix method, is developed to analyze the in-plane vibrational behavior of the CABH ring, and its validity is confirmed through Finite Element Method (FEM) simulations. The underwater vibrational and sound field distribution properties of the ABHUR are investigated using FEM and compared with two alternative radiators employing longitudinal-bending (L-B) and longitudinal-radial (L-R) modes. Owing to the unique properties of the Acoustic Black Hole structure (ABHs), which amplify bending wave amplitudes and concentrate energy, the ABHUR operating in L-B mode demonstrates superior ultrasound intensity. Furthermore, a prototype of the ABHUR is fabricated, and a series of three experiments are conducted to validate the operational feasibility of the proposed system.

Acoustic black hole immersed sonoreactor for high-efficiency cavitation treatment

Developing innovative sonoreactors to enhance acoustic processing efficiency holds immense importance in the field of sonochemistry. Traditional immersed sonoreactors (TISs) mainly produce cavitation at the probe tip, with a relatively weak cavitation around the probe, resulting in posing challenges for high-efficiency cavitation treatment. Here we propose an acoustic black hole immersed sonoreactor (ABHIS) in longitudinal-flexural coupled vibration, enabling high-efficiency cavitation treatment by unleashing the cavitation potential of the probe. The symmetrical structure of the probe is altered to introduce a coupling of flexural vibration mode, and an acoustic black hole (ABH) profile is integrated to further enhance both flexural wave number and amplitude. In this paper, we present a systematic theoretical design method for ABHIS and compare its performance with TIS using finite element method (FEM). An ABHIS prototype is fabricated and subjected to experimental tests and cavitation observation. The results demonstrate that our theoretical analysis model accurately predicts the frequency characteristics of ABHIS. The proposed ABHIS exhibits satisfactory dynamic characteristics, with significantly increased vibration displacement and acoustic radiation ability compared to TIS. Importantly, the ABH design significantly expands ultrasonic cavitation regions and enhances acoustic radiation intensity of ABHIS, resulting in a substantial improvement in acoustic processing efficiency.

Investigation of a cascaded piezoelectric transducer with cone horn for multi-mode power ultrasound application

To meet the ultrasonic application requirement of high power intensity and large mechanical displacement, a new theoretical method is used to study the multi-mode characteristic of the cascaded piezoelectric transducer with cone horn in this paper. Based on equivalent circuit and Kirchhoff’s law to obtain the frequency equation and vibration velocity expression of the transducer, then the resonance frequency and effective electromechanical coupling coefficient can be calculated, the velocity amplification ratio can be obtained in the meantime. This method is distinguish from traditional theoretical analysis, which avoids complex transformation of the multi-excitation sources in cascaded structure, and can calculate more performance parameters. The relationships between these performance parameters and the excitation position of the piezoelectric stack, the length and output end radius of the cone horn are analyzed and compared with the numerical simulation, and the optimized parameters of the transducer size are given. A transducer is manufactured for experimental test, the results show that the experimental value is in good agreement with theoretical calculation and finite element simulation. This work is expected to be used in the optimal analysis of the multi-mode transducer in high power ultrasonic field.

Multi-mode coupled vibration analysis and radiation sound field investigation of a novel multidirectional piezoelectric ultrasonic transducer

Nowadays, expanding the operating range and realizing multifrequency operation have emerged as focal and imperative objectives in the design of ultrasonic transducers. Due to the limitations of structure and radial sizes, conventional Langevin transducers encounter challenges in meeting the increasingly stringent requirements across diverse ultrasonic applications. Hence, this paper proposes a multidirectional piezoelectric ultrasonic transducer (MPUT) consisting of a large-dimension sandwich piezoelectric transducer (LSPT) and a metal tube in mutli-mode coupled vibration, capable of achieving wide-ranging and multifrequency acoustic radiation. Based on the analytical method, a two-dimensional electromechanical equivalent circuit model (2D-EECM) of the MPUT is established, and its frequency calculation results are validated through the finite element method (FEM) and impedance analysis experiment. The vibration testing results indicate that adjusting the radial size can control the coupled vibration intensity of the MPUT and achieve dual-frequency and multidirectional uniform radiation. The radiation sound field testing results confirm the MPUT's satisfactory three-dimensional radiation capability in water and significant improvement in acoustics operating range.

Theoretical modeling and experimental verification of an improved radial composite transducer consisting of a metal ring and a radially polarized piezoelectric stack

In the ring radial transducer, the wall thickness of the radially polarized piezoelectric ceramic is limited by the polarization technology and operating voltage, resulting in the limited power capacity and vibration ability of the transducer. Hence, an improved novel radial composite transducer (nRCT) is proposed in this paper, which consists of a radially polarized piezoelectric stack and a metal ring. Piezoelectric stack is used to enhance vibration and effectively solve the problem of difficult excitation caused by large wall thickness. A new electromechanical equivalent circuit model (EECM) of the nRCT in radial vibration is established, and the relationship between frequency characteristics of the nRCT and geometric size is analyzed. The finite element method (FEM) is used to carry out numerical modeling of the nRCT and the traditional radial composite transducer (tRCT), and preliminarily verify the calculation results of EECM. Compared with the tRCT, under the same electrical excitation, the equivalent electrical impedance of the nRCT designed in this paper decreases to 26%, and the radial vibration displacement increases to 142%. Finally, the nRCT and the tRCT are fabricated, and the experimental results have well verified the results of the theoretical analysis. The proposed radial piezoelectric stack model provides a new idea for the optimal design of radial vibration piezoelectric devices, which is expected to be further applied to the design of hydrophones, piezoelectric transformers, and medical ultrasound devices.