[Q&A] May 22, 2017
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Question: What is cavitation? Answer: When the pressure at the impeller of a centrifugal pump is lower than the saturated vapor pressure of the liquid, the liquid begins to vaporize, resulting in the formation of numerous bubbles. When the bubbles enter the high-pressure area along with the fluid, they rapidly condense and burst under the influence of the high-pressure liquid. At this point, the fluid impacts the space previously occupied by the bubble at an extremely high flow velocity, creating a local hydraulic shock. The impact pressure of the liquid is high and occurs frequently, causing spots, cracks to form on the surface of the impeller, eventually resulting in a honeycomb-like or spongy appearance. At the same time, it causes the pump to produce accentuated vibrations, degrading its performance. Flow rate, head, and efficiency drop suddenly. This phenomenon of vaporization, condensation, and impact is called cavitation. http://bbs.hcbbs.com/static/image/hrline/4.gif Haichuan Network’s special May Day event, “Remembering the Glorious Moments,” warmly invites your participation. http://bbs.hcbbs.com/thread-1774529-1-1.html (Source: Haichuan Chemical Forum) Summary post for Haichuan Network’s special May Day event, “Remembering the Glorious Moments.” http://bbs.hcbbs.com/thread-1774532-1-1.html (Source: Haichuan Chemical Forum) First round of voting for the creative ideas contest (use your mouse to influence the results). http://bbs.hcbbs.com/thread-1776507-1-1.html
When the pressure at the inlet of the impeller is lower than the saturation pressure of the working medium, part of the liquid will evaporate (i.e., vaporize). After evaporation, when the bubbles enter areas with higher pressure, they condense suddenly due to the pressure, and the liquid surrounding them flows in to fill that space, resulting in a hydraulic shock. This phenomenon is known as cavitation.
When the pressure at the inlet of the impeller is lower than the saturation pressure of the working medium, part of the liquid will evaporate (that is, vaporize). When bubbles enter a region of higher pressure after evaporation, they suddenly condense under pressure. Consequently, the surrounding liquid flows toward this area, causing a hydraulic shock. This phenomenon is known as cavitation. This continuous localized impact load causes gradual fatigue damage to the material’s surface, leading to erosion of the metal surface and the formation of cavities in various sizes. The instability associated with cavitation results in vibration and noise in the pump; moreover, as bubbles block the channels within the impeller during cavitation, both flow rate and head are reduced, and efficiency declines. Therefore, it is necessary to prevent cavitation from occurring.
If the pressure Pk at some point within the pump drops to the vaporization pressure Pv at the temperature of the liquid at that point, that is, Pk
When the pressure at the impeller of a centrifugal pump is lower than the saturation vapor pressure of the liquid, the liquid begins to vaporize, producing a large number of bubbles. When the bubbles enter the high-pressure area along with the fluid, they rapidly condense and burst under the influence of the high-pressure liquid. At this point, the fluid impacts the space previously occupied by the bubble at an extremely high flow velocity, creating a local hydraulic shock.
When the installation height of a centrifugal pump is increased, the pressure inside the pump decreases; the lowest point of pressure within the pump is usually located near a point slightly downstream of the inlet to the impeller blades. When the pressure here drops to the saturated vapor pressure of the liquid being transported at its current temperature, boiling occurs; the steam bubbles formed then rapidly condense as the pressure increases sharply as the liquid flows from the inlet toward the periphery. This causes the liquid to rush toward the center of the bubble at high speed, generating impacts with very high frequencies and intense instantaneous pressures; this phenomenon is known as cavitation.
When the pressure at the impeller of a centrifugal pump is lower than the saturation vapor pressure of the liquid, the liquid begins to vaporize, producing a large number of bubbles. When the bubbles enter the high-pressure area along with the fluid, they rapidly condense and burst under the influence of the high-pressure liquid. At this point, the fluid impacts the space previously occupied by the bubble at an extremely high flow velocity, creating a local hydraulic shock.
When the pressure at the impeller of a centrifugal pump is lower than the saturation vapor pressure of the liquid, the liquid begins to vaporize, producing a large number of bubbles. When the bubbles enter the high-pressure area along with the fluid, they rapidly condense and burst under the influence of the high-pressure liquid. At this point, the fluid impacts the space previously occupied by the bubble at an extremely high flow velocity, creating a local hydraulic shock.
When the pressure at the impeller of a centrifugal pump is lower than the saturated vapor pressure of the liquid, the liquid begins to vaporize, forming numerous bubbles. As these bubbles move with the fluid into areas of higher pressure, they collapse rapidly due to the effect of the high-pressure liquid. At this point, the fluid rushes at extremely high speeds into the space previously occupied by the bubbles, creating a localized hydraulic shock.
When the pressure at the impeller of a centrifugal pump is lower than the saturation vapor pressure of the liquid, the liquid begins to vaporize, producing a large number of bubbles. When the bubbles enter the high-pressure area along with the fluid, they rapidly condense and burst under the influence of the high-pressure liquid. At this point, the fluid impacts the space previously occupied by the bubble at an extremely high flow velocity, creating a local hydraulic shock.
When the pressure at the impeller of a centrifugal pump is lower than the saturated vapor pressure of the liquid, the liquid begins to vaporize, forming numerous bubbles. As these bubbles move with the fluid into areas of higher pressure, they collapse rapidly due to the effect of the high-pressure liquid. At this point, the fluid rushes at extremely high speeds into the space previously occupied by the bubbles, creating a localized hydraulic shock.