Cavitation could happen in a pump and certainly it could happen in a turbine. What the difference between them?
I am under the impression that there is no difference between them. Cavitation occurs when the pressure at a location falls below a critical pressure for cavity formation. Although there may be subtleties like, what is the critical pressure for your system as a function of say temperature or any other system parameter, the process should be the same. In a turbine there are rapidly varying pressures and if at a point the pressure falls below the critical pressure a cavity is formed. In a pump there are rapidly varying pressures and if at a point the pressure falls below the critical pressure a cavity is formed. A classic book on this can be found at amazon http://www.amazon.co.uk/Cavitation-Bubble-Dynamics-Engineering-Science/dp/0195094093/ref=sr_1_2?s=books&ie=UTF8&qid=1381755125&sr=1-2&keywords=Cavitation#_
Thank you! I also get a question. Can I get that the collapse will be weaker for the lower outlet pressure of the turbine? The fluid expands in turbine and the outlet pressure must be lower than the inlet pressure. Could this result in weaker collapse?
Hydraulic machines are very similar to the area worked in recent years (before retirement). Studying a lot, comes to many results, but little is published. But if there is any disclosure these are mainly specific conferences on the subject (disperse). If you have interested you have to look carefully at various conference proceedings.
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About your last question, attention! Cavitation in hydraulic machines is mainly due to the internal geometry of the runner, the guide vanes.
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Numeric models are important for locating points of cavitation probable; however self-vibrations, localized reversals of the flow and another problems ( steady and unsteady flow regime!) are often not detected by numerical simulations.
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In addition to these, there are inducing vibrations by rotation controllers.
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An angle or poorly chosen geometry in certain flows can cause vibrations in non-steady flow leading to the cavitation.
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Unfortunately it is not as simple as you think!
thank you very much! I have got what you mean. And could you please tell me some conferences? Thank you!!!
cavitation occurs when the fluid pressure will reach a value below the vapor pressure at the corresponding temperature. thus, there is not any difference between cavitation phenomenon in pump and turbine. The main reason is pressure drop caused by velocity or low ambient pressure, or geometry effect.
Hongyang Li.
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You can start looking at the last symposium of IAHR-Division 1 _ IAHR Hydraulics,
Committee on Hydraulic Machinery and Systems in Beijing!
http://m.iopscience.iop.org/1755-1315/15/3
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Important to read what is written at the beginning of the work of Solemslie and Dahlhaug in the Abstract, “A reference Pelton turbine design”. “Abstract. The designs of hydraulic turbines are usually close kept corporation secrets. Therefore, the possibility of innovation and co-operation between different academic institutions regarding a specific turbine geometry is difficult…..”
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But if you look carefully every detail, every figure you'll have a few more valuable information.
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They write little, but what is written is not wrong.
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The IAHR conferences are biannual, and has lots of information there for those with patience and care.
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You can also find some things like theses:Pressure pulsations and stress in a high head Francis model turbine (2013) or Trykkpulsasjoner i Francisturbiner - sammenligning av modell og prototype malinger (2013) (Pressure pulsations in Francis turbines - comparison of model and prototype measurements).
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It will not be a simple job!
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