Measuring particle concentration in multiphase pipe flow using acoustic backscatter: Generalization of the dual-frequency inversion method

Abstract

A technique that is an extension of an earlier approach for marine sediments is presented for determining the acoustic attenuation and backscattering coefficients of suspensions of particles of arbitrary materials of general engineering interest. It is necessary to know these coefficients (published values of which exist for quartz sand only) in order to implement an ultrasonic dual-frequency inversion method, in which the backscattered signals received by transducers operating at two frequencies in the megahertz range are used to determine the concentration profile in suspensions of solid particles in a carrier fluid. To demonstrate the application of this dual-frequency method to engineering flows, particle concentration profiles are calculated in turbulent, horizontal pipe flow. The observed trends in the measured attenuation and backscatter coefficients, which are compared to estimates based on the available quartz sand data, and the resulting concentration profiles, demonstrate that this method has potential for measuring the settling and segregation behavior of real suspensions and slurries in a range of applications, such as the nuclear and minerals processing industries, and is able to distinguish between homogeneous, heterogeneous, and bed-forming flow regimes.

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

“…In a related paper (Rice et al, 2014) a novel method for measuring K and for arbitrary materials was described, and measured values of K and for spherical glass and non-spherical plastic particle species are summarised in Table 2. A short description of the method follows.…”

“…A full description of the methods and apparatus used to determine those properties are given in the preceding paper (Rice et al, 2014) and were summarised in Section 2. The dual-frequency method described in Section 2 requires that the ratio 1/ 2, as it appears in Equation [11], be "sufficiently different from unity" .…”

“…In this section, one specific acoustic model based on backscattering and attenuation -that of Thorne and Hanes (2002) and Hurther et al (2011) -is outlined, since it is used as the basis of this study, and the reader is referred to a related paper (Rice et al, 2014) for a more thorough description. The received root-mean-square (RMS) voltage, V, excited in the ultrasonic transducers by backscattered energy is related to the mass concentration of suspended particles, M, and varies with distance from the transducer, r, as follows (Thorne and Hanes, 2002):…”

“…Here, as in a related paper (Rice et al, 2014), ks and kt are expressed as the combined backscattering and system coefficient, K, such that = .…”

“…marine/coastal sediment (Thorne and Meral, 2008). The model was therefore modified in a preceding paper (Rice et al, 2014) to be applicable to suspensions of particles with arbitrary properties of engineering interest. Values of the backscattering and attenuation coefficients for four particle types (two spherical glass, two non-spherical plastic), and a novel method for measuring them, were presented.…”