To address the limitations of traditional one-dimensional longitudinal vibration transducers in terms of single-directional acoustic radiation and limited radiation area, this study proposes a novel longitudinal-bending orthogonal coupled piezoelectric ultrasonic vibration system (The vibration schematic diagram of the vibration system is shown in Fig.(a)). By synergistically integrating the orthogonal longitudinal vibration of a sandwich-type piezoelectric transducer, displacement amplification via conical horns, and flexural vibration of metal disks, the system achieves two-dimensional four-directional large-area ultrasonic radiation.

A combination of theoretical modeling, finite element simulation, and experimental validation is adopted to investigate the dynamic characteristics the system. First, an electromechanical equivalent circuit model is established based on coupled vibration theory and electro-mechanical analogy principles, from which resonance frequency equation and anti-resonance frequency equation are both derived. Subsequently, finite element simulations are conducted using COMSOL multiphysics to analyze the impedance responses, vibration modes, and acoustic radiation characteristics in air. Finally, prototype fabrication and performance verification are performed through impedance-analyzer measurements, laser vibrometry, and ultrasonic de-misting experiments.

Compared with experimental results (22086 Hz and 22196 Hz), the theoretical predictions of anti-phase (22871 Hz) and in-phase (23016 Hz) resonance frequencies show relative errors below 3.7%. Finite element simulations combined with experimental validation confirm the excitation mechanism of 5th-order flexural vibration in the disks. Acoustic directivity patterns reveal a multi-beam radiation pattern with coexistence of main lobes and side lobes (The directional patterns under anti-phase and in-phase vibration modes is shown in Fig.(b)), while in-phase vibration mode demonstrates higher ultrasonic radiation intensity in the near-field region. Furthermore, under 200-W input power, the system reduces smoke concentration within 70 s, demonstrating its feasibility for gas treatment applications.

By leveraging the synergistic effect of orthogonal longitudinal coupling and flexural vibration, this design overcomes the limitations of traditional transducers and provides theoretical and technical support for high-power multi-directional acoustic radiation. The research outcomes provide the promising solutions for applications in ultrasonic smoke removal, ultrasonic dust removal, and other gas-phase processing fields.