A importância do estudo da cavitação em turbomáquinas hidráulicas: bombas centrífugas e turbinas hidráulicas.
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Data
2016Autor
SILVA, Elenice de Matos
AUZIER, Hellen Silva
Metadata
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Much of the electricity consumed in the country comes from hydroelectric plants, with a
significant and growing energy demand. To meet the energy demands hydroelectric plants are
working at the maximum limit, favoring the appearance of problems of various kinds, such as
cavitation. This process produces negative consequences in hydraulic equipment such as noise,
vibration of structures, reducing power and equipment efficiency, instability in the flow of the
fluid and the most aggravating: erosion, which is one of the most harmful diseases that occur
in the hydraulic equipment, due cause structural problems and economic losses due to leave
dead machines periodically for repair, maintenance and even partial or complete replacement
of the equipment .. in general, turbomachinery, because the free movement of bubbles
immersed in the fluid flowing the internal channels of the same, are vulnerable to cavitation
because it can occur in any area of the structure or the blades. The study aimed to identify
techniques for analysis and monitoring of cavitation in hydraulic machines as an example, we
can mention: the acoustic method involving sound measurement by means of sensors and
preamplifiers, which propagates in the fluid transmitting its energy acoustic structure, thereby
enabling the measurement of sound with those data it holds a supervisory equipment, the
analysis also can prevent the development or expansion of the phenomenon; Another method
is the vibration that occurs by monitoring the signals obtained by sensors energy associated
with the vibration process which transforms the sensors mechanical vibration energy into
electrical signals, with the data obtained it is possible to make comparisons with plants or earlier
and thus identify if there were any new dynamic effort. In addition, measures can be taken in
the system design phase. The pumps, the calculation of NPSH makes a prediction of the safety
margin against the effects of cavitation. Can prevent the occurrence of erosion, it is necessary
to keep the equipment in operating conditions around its design point. In the event of cavitation
erosion, the welding process can recover the damaged parts, filling the holes and reconstituting
the contours. It is important to make frequent maintenance at the right time, noting that a slightly
higher cost in the design phase will save a lot of hard work and maintenance cost.