Resumo

CRUZ-VANEGAS, Samuel. Local lumped parameters of a Cavitating Venturi tube. Ing. invest. y tecnol. [online]. 2019, vol.20, n.3, e033.  Epub 15-Out-2019. ISSN 2594-0732.  https://doi.org/10.22201/fi.25940732e.2019.20n3.033.

Dynamics of the cavitation phenomenon is mainly function of the cavitation numbers, Mach and Reynolds, as well as of the volumetric fraction of gas plus vapor dissolved into the liquid and the geometric factors of the cavitating device. Currently, some large and complex devices are used to monitor, in a non-invasive way, some of the previously mentioned variables. Nevertheless, they are ostentatious, expensive and in some cases dangerous, such as the electrical and x-ray tomography. One alternative is the monitoring of acoustic emissions generated by the cavitation phenomenon together with simplified theoretical models, such as the lumped parameter models, to determine in a simple and immediate way some of the mentioned variables. Due to the above, in this work, the cavitation into a Venturi tube as a second order system able to generate and damping acoustic frequencies is studied; using the Navier-Stokes equations for biphasic, homogenous, one-dimensional and barotropic flows. Consequently, the frequency coefficient determined is a function of the aforementioned variables. To corroborate the theoretical model, a hydrodynamic system with valves, a pump and a Venturi tube is implemented. The acoustic, as well as the temperature and flow dynamic are monitored using piezoelectric sensors, a thermometer, a high speed camera and a differential manometer. According to the results, the frequency parameter is a change indicator of the volumetric fraction of gas plus vapor dissolved into the liquid and the Venturi tube behavior as a meter or flow controller. Furthermore, the condition that allows cavitating flows to propagate pressure waves are the Mach and cavitation numbers. Even though the present theoretical model is consistent with the experimental observations, it must to be modified to include the generation of pressure waves.

Palavras-chave : Lumped parameters; hydrodynamic cavitation; biphasic flow; Venturi tube; gas volumetric fraction.

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