Jet Penetration and Bubble Dynamics

Gas jets in fluidized beds were reviewed by Massimilla (1985). A more recent review is by Roach (1993) who also developed models to differentiate three jet flow regimes jetting, bubbling and the transition. However, most of the data were from jets smaller than 25 mm. The discussion here will emphasize primarily large jets, up to 0.4 m in diameter, and operation at high temperatures and high pressures. The gas jets can also carry solids and are referred to as gas-solid two-phase jets in this discussion. 

Momentum Dissipation of a Gas-Solid Two-Phase Jet. Gas velocity profiles in a gas-solid two-phase jet inside a fluidized bed were determined at five different horizontal planes perpendicular to jet direction using a pitot tube (Yang and Keaims, 1980). The velocity profiles were integrated graphically, and gas entrainment into a jet was found to occur primarily at the base of the jet. 

The measured impact pressures and static pressures were converted to gas velocities using the following equation  

A reasonably consistent universal velocity profile is obtained by plotting (UJr - Ujb)/(Ujm - U.b) vs. r/r1/2 in Figs. 16-18, comparable with the Tollmien solution for a circular homogeneous jet in an infinite medium (Abramovich, 1963 Rajaratnam, 1976). 

The limiting form of Eq. (24) at atmospheric pressure (101 kPa), where the correction factor Rcf = 1. approaches the correlation originally proposed for atmospheric condition, as shown in Eq. (25)  

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