Study On The Measurement Of Disperse Phase Velocity Of Multiphase Flow

Multiphase flow, a hybrid fluid system containing substances with two or more phases, exists widely in industrial process and daily life. The measurement of flow parameters is of great significance for efficiency, safety and cost-saving in industrial production. However, due to the complexity of its flowing mechanics and diversified factors, the parameters measuring remains problematic. Basing on multiphase flow detecting theory, the study carried out a exploratory research on disperse phase velocity measurement in froth flotation process and a bubble ascending velocity measuring system was designed.First, this thesis introduces the development background of multiphase flow system and correlation parameters measuring techniques. Then, it gives a presentation on froth flotation process along with a special bubble ascending velocity and the height of liquid measuring technique which integrates small capacitance and cross-correlation measuring. In order to implement the proposed technique, The section of hardware design adopts Atmega64 MCU, consists of polar plate switching circuit, examination circuit of small capacitance, A/D sampling circuit, serial communication circuit and power circuit and system functions such as data acquisition and communication are achieved using ICCAVR for programming; the PC part is built in a Matlab environment, managing data processing, cross-correlation calculation, results display and storage.To verify the validity of the proposed system, several experiments were conducted under laboratory conditions. On one hand, a number of measurements for the height of liquid level has been done, and the tolerance is less than 20mm. On the other hand, through a comparative analysis of the system output with/without bubbles, we can see that there is a slight difference in the mean signal strength, as well as a acute change in noise signal, which indicates that the system is capable of detecting the subtle signal change caused by generation of bubbles. The result shows that a combination of small capacitance and cross-correlation measurement technique is an effective approach to deal with bubble ascending velocity measuring problem in froth flotation process and the proposed system is of certain applicative value for industrial production and optimization.