doctoralThesis
Estudo numérico e experimental do escoamento bifásico líquido-gás em um rotor centrífugo
Fecha
2019-12-11Registro en:
AZEVEDO, Henrique Stel de. Estudo numérico e experimental do escoamento bifásico líquido-gás em um rotor centrífugo. 2019. Tese (Doutorado em Engenharia Mecânica e de Materiais) - Universidade Tecnológica Federal do Paraná, Curitiba, 2019.
Autor
Azevedo, Henrique Stel de
Resumen
Centrifugal pumps are subject to sudden flow pattern variations and performance degradation when operating with two-phase gas-liquid flows. Studies about this subject are majorly experimental and focused on performance evaluation, with little information about the physical mechanisms behind the problem and rare numerical works found in literature. These needs motivated the development of a numerical and experimental study of the gas-liquid flow in a centrifugal rotor. The mathematical modeling is based on the Two-Fluid Model and a multiple-size group, polydispersed approach, including the effect of several interface interactions of gas-liquid flows, such as bubble breakup and coalescence. Simultaneously, an experimental approach to the problem is proposed by means of an experimental loop designed to measure the pressure rise through the studied rotor, as well as techniques for visualization and image processing of the flow patterns and intake gas volume fraction measurement. The study was performed for rotating speeds from 200 to 500 rpm and considers a wide range of liquid and gas flow rates. The experimental results obtained allowed the identification of different gas-liquid flow patterns in the rotor, helping to understand how they are associated with performance degradation and serving as a database to validate the numerical model. The numerical results agree well with the experimental ones. They were explored to understand the behavior of various flow parameters, as well as the role of different interface forces on the phenomenon. This analysis revealed that several interface models, which are often neglected in similar works from literature, are important for a good representation of the flow patterns and of the rotor performance under two-phase flow. Finally, a mechanistic development to predict the surging initiation point in rotors operating with two-phase flows was proposed. In general, it is expected that the results and discussions from this work could help for a better understanding of the phenomenon and as a database for future works.