Study of the axial stability of a sphere with high temperature in acoustic levitation

Aiming at the axial stability of a high-temperature sphere levitated in a standing wave field, the physical model coupled with the sound field, heat field, flow field and gravity field is established. Based on the finite element method, the non-uniform temperature field and sound field in the space around the sphere are calculated. The axial levitation stability of a silicon nitride sphere with a diameter of 2 mm in the standing wave acoustic field are analyzed when the temperature increases from 300 K to 2000 K. The accuracy of the simulation model is verified by the experiments of acoustic levitation at normal atmospheric temperature. The results show that under the condition that the initial levitation spacing satisfies resonance and remains constant, the equilibrium position of the sphere decreases with increasing temperature of the sphere, and there exists a maximum temperature for stable levitation of the sphere. With increasing temperature, the axial stability of the levitated sphere can be maintained to a certain extent by adjusting the emitter-reflector distance and emitter excitation voltage through feedback.