Effect of Emulsion Fluidization State On the Fluctuations In Gas and Particle Velocities Inside the Plume of a Gas Jet Penetrating a Fluidized Bed

The enhanced mass, momentum and energy transfer between the emulsion phase and the gas jet that occurs when a jet impinges a fluidized bed is exploited favorably in many industrial applications, such as coal and biomass gasification. In order to characterize such flows, earlier works have focused on the measurement and analysis of the resulting plume size and shape as well as mean velocity and concentration profiles within the plume. Though the jet plume is a region of turbulent mixing, no experimental data concerning fluctuations in the velocities has been reported, primarily due to the limitations in the measurement techniques employed so far.

This talk presents variation in the fluctuations of both gas and particle phase velocities inside the jet plume region with change in the fluidized state of the emulsion. The measurements are achieved using a Laser Doppler Velocimetry technique. It is seen that below minimum fluidization there is a decrease in the fluctuating intensity in both phases upon increasing the fluidization rate, but increasing the fluidization rate beyond minimum fluidization significantly increases the fluctuations. These fluctuation measurements would help in the development of more fundamentally sound two-phase models which are based on the principles of turbulent flows to explain the complex transport that occurs in a bubbling bed.