THE DEVELOPMENT OF A MATHEMATICAL TECHNIQUE FOR THE DESCRIPTION OF THE FLOW OF SOLID GASEOUS SUSPENSIONS

The work reported in this paper represents the results of large scale fundamental studies into the behavior of dilute - phase solid gaseous suspensions pneumatically conveyed through a 100mm diameter pipeline. All investigations were carried out at a Re of the order of 200 000. The effects on conveying characteristics of these suspensions of low - frequency pressure pulsations due to rotary feeders were studied in detail at various feeder rotational speeds and mass Flow ratios. The use of harmonic analysis techniques enabled the author to reach tentative conclusions in this sense. It appears that low - frequency pressure oscillations are partly responsible for the well - known phenomenon of drag reduction. However, the use pf the methodology reported in this work suggests that a variety of flow mechanisms are also feasible under conditions of very snail scale or no pulsations.

The above considerations suggest the existence of 'transitions' in the flow behaviour of such solid gaseous suspensions. Present work being undertaken at the University of the Witwatersrand, Johannesburg, South Africa, will attempt to seek further evidence for these preliminary conclusions.

Discussions held subsequent to the research findings reported in this paper, established significant inadequacies in the data acquisition system employed in the present work. The tine interval between observations achieved with the present system, 40ms, was considered to be inadequate for the meaningful 'characterisation' of the phenomena studied. A tine interval (between observations) of approximately lms was considered essential to enable generally valid conclusions to be drawn from the present studies. Notwithstanding this severe technical deficiency which places obvious limitations on the generality of the conclusions reached, discussions en the phenomena observed are presented in the light of the major objective of this work, namely the development and illustration of a methodology suitable for the study of the various parameters influencing a dilute-phase pneumatic conveying system.