Coaxial Flow of Particle-Laden Streams in a Circular Duct

Abstract

Ducted coaxial flows of homogeneous gas streams exhibit interesting recirculation patterns when the inner-to-outer stream velocity ratio is either large enough or small enough. The existence of these recirculation patterns became evident during the development of ducted fan jet engines and other aerospace devices. Recent interest in the next generation of fluidized-bed-based catalytic chemical reactors may turn to processes that incorporate the ducted coaxial flow of particle-laden gas streams for very fast multistep reactions. Significant recirculation patterns in such a reactor system would be detrimental to the design objectives by causing catalyst and gas backmixing and excessive catalyst holdup. In this experimental program, a ducted coaxial flow of particle-laden streams was studied over a range of inner-to-outer stream velocity ratios from 0.7 to 3.0. A number of instrumental methods were used in the measurements. It is shown that recirculation patterns that contain solids occur in these flows and ...