Using Ultrasonic Signal Reflection to Characterize the Density and Viscosity of Fluids and Slurries

Abstract

Ultrasonic signals can be used to interrogate many forms of two-phase systems, dense slurry-laden and three-phase suspensions. This paper describes using ultrasonic signal reflection at a fluid-sensor interface to characterize fluid and slurry density and viscosity. The sensor consists of a series of transducers mounted on a wedge with the base of the wedge in contact with the liquid. Ultrasonic beams, striking the wedge base at several angles, are reflected at the base-liquid interface to the receive transducers. The amount of reflection at this interface depends upon the density of the liquid, the speed of sound in the liquid, and the wedge parameters. The response of a shear wave transducer, in conjunction with a density measurement, is used to determine the viscosity. The sensor can be mounted in a pipeline configuration or submerged in a tank for process control of food products. Novel features include: the small size of the probe and the sensor robustness. Performance is not affected by fluid flow rate, entrained air, or vibration. Experimental measurements of the density and viscosity for fluids and slurries are presented.