Research On The Structure Of High-intensity Sound Source With Flow-sound-separation For Aerosol Agglomeration Applications

Acoustic agglomeration technology can arouse relative motion and rapid agglomeration for aerosol particles.Using an air-jet generator with simple structure,low power consumption and high sound power to carry out sound wave agglomeration,the spent air after work will have a negative impact on the effect of sound wave agglomeration.In order to reduce the negative impact caused by spent air,this paper designs and manufactures An air-sound separation type airflow sound source,which can separate the spent air from the sound and reduce the influence of airflow on the agglomeration effect.In this paper,based on the Hartmann whistle,an opening is set between the Hartmann whistle and the horn,so that the spent air after work can be discharged to the external environment through the side opening to achieve the effect of separation of gas and sound.Firstly,the flow-sound-separation type sound source is studied by numerical simulation method,and the flow field and pressure field are observed during operation.It is found that under the influence of the vortex at the lower end of the jet and the pressure change in the horn,a backflow phenomenon occurs inside the horn.The effects of the depth of the resonator,the distance between the nozzle and the resonator and the distance from the side opening on the gas-acoustic separation were studied.The distance between the nozzle and the resonator had the greatest impact,followed by the side opening,and the depth of the resonator was the smallest.When the depth of the resonant cavity is increased,the mass flow at the side opening decreases,the sound frequency of the sound source decreases,and the total sound power of the sound source increases.By changing the distance between the nozzle and the resonant cavity,the total acoustic power is maximized when the resonant cavity is located in the turbulent mixing region.With larger side openings,the total sound power remains the same,but the available sound power decreases.Secondly,according to the simulation results of three structural parameters,an air-acoustic separation type sound source with a frequency of 3 k Hz,a sound power of 156 W and the best exhaust effect was designed and manufactured.The air-sound separation effect is verified by experimentally testing the frequency,sound pressure level and wind speed of the sound source.The main frequency obtained from the experimental measurement is 2.9 k Hz,which is close to the 3.0 k Hz obtained by the simulation.The sound energy of the air-acoustic separation type sound source is mainly concentrated at the outlet of the horn,and the sound pressure level decreases with the increase of the opening distance,but increases with the increase of the intake pressure.The airflow at the horn exit is mainly concentrated in the central area of the horn,which is much larger than other areas.At the same time,the wind speed in the central area is not greater than 1.1 m/s,and the air-sound separation effect is good.Both the sound pressure level and the wind speed will attenuate with the increase of the propagation distance.In contrast,the attenuation of the sound pressure level will be smaller than that of the wind speed.Therefore,in a large space,the airflow will only have a greater impact at the initial stage of propagation.Finally,sonic agglomeration of ultrafine droplet particles is performed using an aeroacoustic separation type sound source.Within 7 s after the sonication,the light transmittance in the agglomeration chamber can reach 98%,and the droplet particles have basically agglomerated into large droplets,which drop to the bottom of the agglomeration chamber.The lower the air velocity,the less interference with the agglomeration.Under a certain intake pressure,the higher the intake pressure,the stronger the sound field intensity in the agglomeration chamber,the greater the vibration amplitude and movement speed of the particles,the higher the collision probability between particles,and the better the sound wave agglomeration effect.The higher the initial aerosol concentration,the more the number of droplet particles per unit volume,and the higher the early agglomeration rate.However,with the increase of agglomeration time,the rate of agglomeration in the later stage will tend to be the same,and an approximate agglomeration effect will be achieved.