Theoretical and Experimental Study on Multi-parameter Measurement by Ultrasonic Method in Particle Two-phase System

摘要

Measurement technology of muti-parameters in particle two-phase system, which has been paid more attention in recent years, is a great challenge for researchers. However, the parameters of particle twophase system are showing great importance for further study. Not only the density and concentration but also the particle size distributions of disperse phase in particle two-phase system have been studied in this paper. A novel approach of measuring the density and concentration of particle two-phase system has been developed in this paper, in which the multiple reflection technique is employed to obtain acoustic impedance of the particle two-phase system. Furthermore, the density can be determined by the acoustic impedance combined with the information of sound speed for ultrasonic waves, based on the acoustic theory. As a result, the concentration of particle two-phase system could be achieved by means of a strict derivation from the known densities of the discrete and continuous phase. Experiments have been designed to demonstrate the means with the sample of carborundom (SiC) suspension at the mass concentrations of 14%, 17%, 20%, 25% respectively, in which a group of superb ultrasonic signals (see figure 6, including more than 12 echoes in each one), have been obtained with a high frequency and wideband ultrasonic transducer (V324-SU, Olympus) at a center frequency of 25MHz. Meanwhile, another wideband ultrasonic transducer (V312-SU, Olympus) with a lower center frequency (5MHz) is utilized to generate and receive ultrasonic signal, then attenuation spectrum are obtained with the method of pulse echo mode measurement. To extract credible particle size distribution from measured ultrasonic attenuation spectrum, McClement's theoretical model, which is actually a simplified and explicit model for the long wave regime, has been adopted together with BLBL (Bouguer-Lambert-Beer-Law) scattering model. The optimum regularization algorithm is put to use in order to overcome the ill-posed problem and inverse particle size distribution accurately. Experiments were performed to validate the methods and algorithms put forward above for the sample of SiC powder and crystalline silicon cutting liquid, and the results show good agreement with the instrument (OMEC Co,Ltd) based on the principle of Coulter.