【摘要】 研究了由颗粒悬浊液中3个频率下声衰减系数测量颗粒粒度分布和浓度的方法。用FFT对测得的1,2和5 MHz 3个频率的声信号进行降噪后得到声幅度和声衰减系数,再根据描述不同频率下声衰减系数与颗粒粒径及浓度关系的ECAH模型,运用Philip-Twomey-NNLS算法和改进Chahine算法求解相关的第一类Fredholm方程,反演出颗粒的尺寸分布和浓度。用该方法对两种不同尺寸体积浓度为5％的玻璃微珠-水悬浊液颗粒进行测量,结果与显微镜法结果吻合。这表明:测量3个频率下的声衰减信号,结合Philip-Twomey-NNLS或改进的Chahine算法,可在较高浓度条件下较准确地测得颗粒粒度和浓度,从而简化了现有的高频率宽频带测量方法。更多还原

【Abstract】 A particle sizing method based on the principle of ultrasonic attenuation (UA) with three frequencies is presented. As a theoretical basis, the ECAH model is employed to analyze relationship between attenuations and particle size and concentration. Experiments are carried out to measure the particle size distribution (PSD) of aqueous glass beads suspensions with vol.5% concentration, in which ultrasonic signal has been generated and received by three transducers with fixed frequencies 1, 2 and 5MHz. Amplitude and attenuation can be obtained using FFT technique. The measured data are evaluated by both Philip-Twomey-NNLS algorithm and the modified Chahine algorithm to solve the first kind Fredholm integral equation and get the PSD and concentration. The ultrasonic measurement results show good consistence with those from microscopical measurement, which indicates the exact PSD and concentration can be obtained and equipment can be simplified by the promoted method.更多还原