Simulation and Experimental Study on Measurement of Droplet Size Distribution Based on a Novel Ultrasonic Attenuation Scheme

Ultrasonic attenuation methods have achieved remarkable success and promising performance in the field of two phase flow measurement. Nevertheless, most of the investigation is conducted for gas or solid particles within liquid phase. In this paper, a novel ultrasonic attenuation scheme is presented for the particle distribution measurement when water droplet as dispersed phase and air as continuous phase. In particular, a modified attenuation model is employed for different combinations of ultrasonic frequencies and droplet sizes while an improved genetic algorithm (IGA) is applied to provide higher accuracy. Several particle distributions were simulated to present the adaptability and robustness of the IGA with modified attenuation model. Furthermore, an ultrasonic system with image processing as verification was implemented to evaluate the feasibility of proposed scheme to measure droplets of size range 1 mu m similar to 1000 mu m. Received ultrasonic signal with frequency 40 kHz, 67 kHz, 125 kHz and 200 kHz was processed by Fast Fourier Transform (FFT) to deliver the maximum amplitude values, which were further averaged to calculate the attenuation coefficient. Finally, relative errors of the Sauter radius within simulation and experiment do not exceed 10% and 20% respectively, which further demonstrates the effectiveness and accuracy of the scheme for droplet size distribution measurement. Moreover, this scheme could be attractive in several applications, such as spray drying, gaseous absorption, development of cosmetics, spray drugs and the flow measurement modeling of wet gas two-phase flow based on ultrasonic attenuation.