Vibrations in engineering and technology

Vitenko Dmytro – PhD student at the Department of Food Technology Equipment, Ternopil Ivan Puluj National Technical University (56 Ruska St., Ternopil, 46001, Ukraine).

Hydrodynamic static-type devices are widely used in various industries, including chemical, food, pharmaceutical, and water treatment technologies. Their efficiency is based on effects related to the life cycle of vapor-gas bubbles formed under specific hydrodynamic conditions within the system. At the same time, a significant issue with such devices is the destruction of working surfaces due to cavitation erosion, which is accompanied by material loss, reduced strength, and structural changes in the material. The impact of the cavitation regime, which arises under a certain ratio of pressure and velocity, can lead to the formation of microcracks that develop into more severe damage over time. 

This article has investigated certain aspects influencing cavitation wear on the walls of models with conical and screw-shaped obstacles. It has been established that the wear intensity depends on flow parameters such as inlet pressure and liquid velocity. Based on numerical modeling results, the region of vapor-gas phase formation has been identified and confirmed through experimental studies on pressure variations along the apparatus and visual observations. Additionally, the highest acceleration values on the apparatus walls have been recorded within the outlet diffuser section, where vapor-gas bubbles collapse and directly impact the walls. A comparison of the two hydrodynamic device models has shown that the use of a conical obstacle promotes a more uniform distribution of the vapor-gas phase along the diffuser, potentially reducing the intensity of local wear. It has been determined that when the inlet pressure increases from 0.4 MPa to 0.6 MPa, the hydrodynamic regime stabilizes, and the vapor-gas phase shifts toward the flow centre, which reduces its negative impact on the walls. However, the increase in mass loss of the sample due to intensified cavitation suggests a greater impact on the technological medium. The obtained results will contribute to the development of effective methods for reducing wear and enhancing the durability and efficiency of the equipment. 

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