Stephen Tallon

The effect of pipeline location on acoustic measurement of gas–solid pipeline flow

Abstract The flow velocity and solids concentration in a pneumatic conveying line can be measured in-line and non-invasively from measurements of the axial propagation of active acoustic signals. This paper investigates the performance of a prototype meter in regions of developing flow, in particular after a horizontal 90° pipe bend where strong particle roping behaviour has been observed. The effect of the location of the instrumentation on the accuracy and reproducibility of the measurement is discussed.

Slip velocity and axial dispersion measurements in a gas-solid pipeline using particle tracer analysis

Abstract Pulses of radioactive tracer particles were injected into a dilute phase pneumatic conveying system, and their passage along the pipeline was recorded at a number of points. The pipeline incorporated both horizontal and vertical orientations, and horizontal and vertical bends. Solids slip velocities were calculated from these measurements and showed that the effect of bends on the solids flow can extend for a long distance downstream of the bend exit. The dispersion of the injected pulses along the pipeline is discussed, and dispersion values calculated assuming a simple axial dispersed plug flow model. The results yielded dispersion coefficients higher than those characteristic of turbulent fluid mixing. They also indicated an area about 4 m (50 pipe diameters) downstream from the exit of two consecutive 90° horizontal bends where the solids experienced high localised dispersion. This has been attributed to the resuspension of material which continues to flow in strands or ropes for some distance after the bend exit.

Velocity measurements in dense down flow of bulk solids using a non-restrictive acoustic method

Abstract The velocity of a dense down flow of particles in a conduit can be measured in-line and non-invasively using acoustic waves to detect the passage of characteristic patterns in the local voidage. These patterns are, however, distorted as they flow through the conduit due to the relative motion between the particles, and shear zones at the wall. This work investigates the effect that the particle velocity and acoustic sampling parameters have on the correlation and velocity measurement of these patterns.

An acoustic method for in-line particle size measurement in flowing bulk solids

Abstract The propagation velocity of acoustic waves through a packed bed of particles depends on, among other things, the wave frequency and the size of the particles. In this paper, theory is developed to describe the propagation velocity based on consideration of viscous interactions between the gas and solid phases. Experimental measurements in the frequency range 50–10 000Hz, and for particles ranging in mean size from 65 to 6000μm, agree well with the theory, particularly at low frequencies. The propagation velocity also correlates strongly with measurements of the surface mean particle diameter, independently of changes in particle density, and a method is described using this relationship as the basis of an in-line particle size measurement instrument for flowing bulk solid systems. Measurements using different size fractions of sand suggest that changes in mean particle size of less than 1.5 per cent can be resolved using the simple prototype developed for this work.

Velocity profile measurements with labelled single particles

Abstract This paper describes experiments aimed at measuring and characterising the velocity profile of particles moving down vertical pipes using the technique of successive single particle injections. This was done to investigate the conditions under which an acoustic method of measuring velocities of particulate materials differed from the expected result. A good correlation was observed between the velocity differences and deviations from a plug flow regime near the wall of the pipe.