Application of optical tomography for measurements of aeration parameters in large water tanks

Abstract

The paper presents a design and application study of a prototype optical tomograph for the detection and definition of shapes of gas bubbles moving in a liquid. In the applied method of measurements, the column is exposed to a homogeneous light beam and next the ray is detected with the use of optical waveguided detectors. Spatial reconstruction of the bubble shapes is done on the basis of the signals coming from two perpendicular systems of detectors. The bubble shape is approximated by an ellipsoid with suitably determined semi-axes and with the use of genetic algorithms based on the neuron network. Influence of the structure and dynamics of the measuring path on errors in representation of gas-bubble shapes and velocities has been analysed. The paper also contains the results of the tomograph tests.

A look at three measurement techniques for bubble size determination

“…However, there 0894 is no calibration standard for them. The most used methods are: high-speed photography [22][23][24][25][26][27]; electrical impedance tomography [28], capillary suction probes [20], optical waveguided sensors [29,30]; endoscopic optical probes [31,32]; capacitance probes [23] and passive acoustic detection [14,15,33]. There are some disagreements among them, since some offer greater rapidity of detection but are constrained by the sensing element sensitivity or by data interpretation issues (passive acoustic, capacitance and electric impedance methods), while others depend on the purity of the liquid medium and lighting effects (photographic and optical methods).…”

Parameter Measurements of Moving Gas Bubbles Using Image Tomography Title

“…Nowadays, photographic methods ( Fig. 1) combined with image analysis, or methods using process tomography [8,13,14] are more commonly used for determination of gas bubble parameters. The paper presents a method using image tomography, which allows to deter-mine movement trajectories of the moving bubbles, as well as their local velocities and volumes.…”

Selection of Optical Tomography Parameters for Gas Bubble Shape Analysis

“…A light detector consists of a matrix with 64 phototransistors. The phototransistors are set up inside collimations tube (Rząsa and Pląskowski, 2003). In systems with a dispersed light beam, the light beams are usually distributed along the pipeline, so it is possible to measure the velocity of moving bubbles.…”

“…This problem is rather complex because in this case the delay matrix is present, but not the displacement number (Rząsa and Pląskowski, 2003). For example, for the sensor with five detectors the matrix takes the following form: The test stand shown in Figure 13 was build in order to verify the algorithm for determination of the velocity.…”