Learning Forum

[enrmarvil]

Hi everyone, I´m designing a centrifugal compressor in Bladegen, and i want to modify the rake angle in trialing edge of the impeller, right now the rake angle equals 0, but want to modify and change it as I want.

For now I can modify beta angle of leading edge on shroud and hub and beta angle of trailing edge.

Let me show you an image:

As you can see, the rake angle equals 0, and want to change, not care how much but the issue is i don´t know how.

I have another question, is about adding spliters, when I add one spliter (One means, one group), the spliters height measure like the main blade, and what i want to do is give them less height, i want it to be about the middle of the machine.

I know one of the ways is making the compressor in Vista CCD from zero, ant then add spliter there, but I don´t gonna use Vista CCD because the 1D model comes of a own code, so if I want to add spliter, the unique way is in BladeGen.

Let me show you what happens when I add a Spliter:

 

I don´t touch anything in that dialogue, but in another time that I explore a little more, don´t find anything usefull,

And that´s the result, is like I´ve been added a lot of blades and not spliters.

Thank you very much for the help, and waiting for your answer soon,

Kike.

[rfblumen]

To modify the trailing edge beta value, do a Right Mouse Button (RMB) in the Angle View.  In the pop-up menu, select Beta Definition.  This will make the beta curve the active curve for modification.  With the Left Mouse Button (LMB), double-click on the last point.  A pop-up menu will be displayed that allows setting the angle value:

Alternatively, you can click on the point and drag it.

The steps you took to create the splitter blade were correct.  The last step to complete the operation is to specify the leading edge cut-off under the LE/TE Cut-Off tab in the Blade Property Dialog box.  The default value is set to 30% but you can modify that:

Regarding making the splitter height less than that of the full blade, this is not a common design approach in turbomachinery so this capability is not offered in BladeGen.  If you wish to have the splitter blade at a different height than the full blade, here is one approach:

1.)  After generating the blade design in BladeGen, export the Neutral Data File (NDF) from File->Export->Neutral Data File and import this file into BladeEditor (or, in BladeEditor, load the BladeGen .bgd file).

2.)  In BladeEditor, using the geometry tools available, generate the shortened height of the splitter blade.  Mesh the blade passage in Ansys Meshing.

[enrmarvil]

Thank you!! the problem with the spliters is solved, but when I talking for heigth I mean to the position of the spliter in the compressor, referring to the last parraf, I don´t know if I are cnfusing you talking about the balde heigth, despite the fact, the problem is solved so. Talking about the beta and rake angle I´m not referring to the beta angle, I want to modify rake angle, I mean, this angle:

As you can see, is not beta what I talking about, I referring to the rake angle, and the issue is that I don´t find the way to modify this, for example, measure the angle from vertical axis, how is looking in the image that I attach, in my own design, that valour equals zero, so, if, for example, want to give it, 60 degree from vertical, how can I modify that?.

Thank you,

Kike.

[rfblumen]

My apologies - I misunderstood.  Given a sample radial impeller with splitters and zero rake angle:

To impose a non-zero rake angle you would want to shift the entire theta curve up or down on each layer except for the hub.  By shifting the entire theta curve, the beta distribution on that layer is unchanged.  Rather, the blade section at that layer is shifted in the circumferential direction.  In the above example, shifting the shroud theta curve downwards by 10 degrees:

The rake angle can be specified as:

 Rake Angle=atan(r*dthet/B2)

where r=blade trailing edge radius (taken from the meridional view)

          dthet= theta shift in radians

          B2= passage width at the blade trailing edge (taken from the meridional view)

 

To determine the desired theta shift at the shroud based on a given rake angle:

dthet=(B2*tan(Rake Angle))/r