LOW FREQUENCY SONIC CLEANING OF PROCESSES INVOLVING POWDERED MATERIALS

摘要

This paper describes a preliminary study of the use of low frequency high intensity sound as a means of dispersing particle deposits causing build-up and blockages in the power and powdered material industries. Low frequency high intensity sonic cleaning operates in a frequency range 25-350 Hz and at sound pressure levels around 130 dB in air and gaseous systems. The mechanisms in cleaning are not well understood and the present knowledge has a largely empirical basis. It is thought that the particle velocity of the sound affects the boundary layer around the dust particle but this does not explain how cleaning occurs in corners. It is not known if the sound excites the particles directly or the surfaces to which they are attached. The acoustic performance of existing sonic cleaning installations has been measured and modelled, including the effective range of the sound generated and the resonant response of the internal pressure fields. The acoustic sources used consisted of air pressure drivers combined with horn profiles, which can be tailored to provide the required frequency and acoustic power. The aims of the present work are to establish relationships between the characteristics of the generated sound fields and the resultant cleaning efficiency.