Vane shape in a closed impeller 1

[NegNeg]

Hi everybody

I would be thankful if you let me know your viewpoint about the following

Today at a pump factory I saw a pump that had vanes with triangle cut. i.e., instead of having common straight/oblique cut it had a forward tringle shape. see the attached file where the red lines show the cut schematically.

do you know what is the reason for such a design? usually trimming is done such a way to increases the distance between the vane tip and the casing (the so-called gap B) via a backward triangle cut. However with such a cut, the distance between the center of the vane and the casing does not change.

Best

 

[JJPellin]

Angling the tips of the vanes in a triangular pattern will tend to break up vane-pass frequency pressure pulsations. This is especially important if the "B" gap is close to the minimum recommended. I assume you are referring to an impeller with vanes tips like this:

Johnny Pellin

 

[Artisi]

You can also cut the blade at 30 / 45 degree in lieu of the triangular, easier to calculate the RMS for the trim diameter.

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)