A laser-based method for bubble parameter measurement in two-dimensional fluidised beds

A non-intrusive technique for the measurement of bubble velocities and sizes in a two-dimensional gas-fluidised bed is described. The method employs an array of three transmitted laser beams which generate a sequence of light pulses when bubbles pass through the array. This sequence is analysed by high-speed on-line logic to determine the bubble parameters. Size measurements made with the system have been compared with bubble size distributions obtained by photography and found to be essentially the same. Bubble velocities and the variation of velocity with size have also been found to substantially agree with established theory for bubble velocities in freely bubbling two-dimensional beds. A stochastic computational model of the bubble measurement process has been developed and the system design parameters have been investigated and compared with experiment. The technique has been shown to have great utility in the analysis of the bubbling structure of the two-dimensional beds containing a variety of particle types.