Measurement of particle concentration in horizontal, multiphase pipe flow using acoustic methods: Limiting concentration and the effect of attenuation

摘要

An acoustic dual-frequency concentration inversion method, in which the backscattered acoustic signal received by transducers operating in the megahertz range is used to determine the concentration profile in suspensions of solid particles in a carrier fluid and which was originally developed for environmental applications, is applied to arbitrary suspensions of general engineering interest. Two spherical glass and two non-spherical plastic particle types with a range of size distributions and densities are used. Particle concentration profiles in horizontal turbulent pipe flow at Reynolds numbers of 25. 000 and 50. 000 - below and above the critical deposition velocity, respectively - and nominal concentrations of 0.5%, 1% and 3% by volume are presented for the four particle species, using measured backscattering and attenuation coefficients. In particular, the effects of particle size, density and flow rate on the transport and settling behaviour of suspensions are elucidated. The results demonstrate the potential of this method for measuring the degree of segregation in real suspensions and slurries across a range of challenging application areas, such as the nuclear and minerals processing industries. The limitations of the method are explored in detail through an analysis of the acoustic penetration depth and the application-specific maximum measurable concentration, both of which can be used to determine the most appropriate acoustic frequencies and measurement configuration in a particular case.