Is cavitation a common issue in Pelton turbines?

[OliskaP]

Hi,

I have a question; can cavitation occur in Pelton turbines? From my understanding we have atmospheric pressure inside the turbine at the runner wheel, so that means cavitation will not occur?

However I read somewhere that there was some problems with cavitation in a Pelton turbine, so that got me wondering. Is there something about cavitation I'm missing?

Best regards.

 

[Baluncore]

can cavitation occur in Pelton turbines?

There is no question that a cavity will form where the water separates from the bucket surface. I think your question is whether implosive collapse of that cavity could occur against a metal surface where it might induce corrosion / erosion.

I agree that cavitation corrosion is not expected with a Pelton bucket wheel, because cavities that may form do not close against the bucket surface. But when the speed of the water jet is high enough, you might expect some form of cavitation to occur when the high speed water jet impacts the edges of a passing bucket.

I think there are two situations where cavitation corrosion might occur on a Pelton wheel.
1. Cavitation on a traditional propeller will tend to be a continuous process that remains in a fixed place on the blade. A Pelton wheel may suffer very short moments of cavitation during jet transition between buckets.
2. A raised irregularity on the bucket surface could cause cavitation downstream. But the high pressure of the jet flowing against the curved bucket surface will tend to prevent cavity formation until the flow reaches separation at the bucket edges.

Is there something about cavitation I'm missing?

No. But you might chase up the reference you "read somewhere" and find out whether it was simple cavity formation or cavitation corrosion of the buckets.
Google ' +cavitation +pelton ' and see what you find.

 

[OliskaP]

Thank you for your answer.

No. But you might chase up the reference you "read somewhere" and find out whether it was simple cavity formation or cavitation corrosion of the buckets.
.

My reference was a PDF document a Norwegian power company published during the celebration of a 100 year old power station. They just said during the life time of the power plant they've had problems with cavitation of one of the pelton turbines, and did not talk about it any further.