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Francis turbine spiral casing
elmar
Member Posts: 4 ✭
Hey guys,
i'm trying here to model a spiral/scroll casing and i don't know how to model the intake and the connection between the start and the end of the spiral.
Getting the initial spiral is easy. I created two profiles and used the loft tool with a circle (also experimented with a helix) as path:
But I don't understand how to model the intake and the piece between the start and the end of the spiral correctly. I'm tinkering around with an additional loft to close the bottom and an additional extrude to model the intake.
Then I tried to use extrudes/lofts/sweeps to remove the pieces which intersect with the inner profile/volume of the case, but without any satisfying results.
From my perspective, the diameter reduction and the scroll it creates is the difficult part. How would you guys model the casing. Can you share some examples that I can take inspiration from?
Thank you!
Answers
couldn't help myself but create 3 different versions. neither of them i'm fully satisfied with, but I've had enough practice for today.
check out the branches and versions in this doc:
https://cad.onshape.com/documents/3a0d794343c1cb343ff14680/w/186f81e2b97c37a1da2da25b/e/ff1d8e83030ff925c5f24ad2
I'd try to make a solid and shell it, or make an outer solid and an inner one to boolean-subtract, if wall thickness was not constant. That would eliminate at least half of the issues that arise from self intersection and such.
Hey jelte_steur814 Thank you for your effort. It's really interesting to see your approach of connecting the intake with the inner spiral end by starting with faces and using the face-blend tool! I had the same thing in mind, but I was completely lost on how this could be achieved, so I went with the "subtracting bodies" method.
Hey martin_kopplow, to make sure I understand you correctly, can you share an example? It doesn't have to be a spiral casing. Just an example to see what you mean by "make a solid and shell it".
one sketch. 3 features. KISS method.
Oof. I didn't read enough. I see your your lofting to a smaller diameter. back to the drawing board.
Actually your example is precisely the KISS method. It's how I see a lot of blower housings designed in actual application. They're not particularly efficient but they definitely are cheap to produce for the vendors.
Course, if we can get a magic aerofoil featurescript I believe it's possible to abstract this turbine casing geometry into script form as well should someone be motivated enough to come along and do it. Maybe some day that person might be me. Until then, I'm content with my off-center circle housing.
Played around with this for a bit. took @jelte_steur814 's model as a starting point. I avoided the self intersecting stuff by breaking up the variable width scroll into two features. one half way around then finishing with the other half.. still not loving the transition but it's not terrible. so possibly building as a solid and using shell as @martin_kopplow suggested might make that part nicer
This one with a center alignment is the nicest for transitions. But I'm assuming you want the variable scroll to lie asymmetrical.