How can you model in BladeGen 10.0 an impeller where the hub does not extend beyond the blade trailing edge?
We have a mixed pump with an impeller that has a cutoff trailing edge at the physical end of the hub, and the return channel has a rounded leading edge at the beginning of the hub surface. What happens if your real geometry does not extend beyond the trailing edge or leading edge?



It is quite common in reality that the impeller may have a cutoff trailing edge at the physical end of the hub, and that the return channel may have a rounded leading edge at the beginning of the hub surface. The meridional hub and shroud curves need to extend beyond the leading and trailing edges otherwise Bladegen will not work and you should extend them for the blade design. Also, this arrangement is required in TurboGrid. Generally, it is OK to approximate a small radial distance that gives an extension to the hub for the CFD modelling, without any significant loss in accuracy. These approximations tend to give a consistent trend, for example, a consistent over-prediction of efficiency by 1-2% over a complete performance curve.

In BladeGen, there is also an option Trim Meridional Profile, that allows a totally separate set of curves to be used and can be selected to be used for output. This can be used to define a set of meridional curves that are separate from the blade design meridional profile, purely for export purposes if the hub/shroud shape in any way compromises the calculation of the blade design, as described above. The idea is that the Meridional Trim Profile option allows you to define (and export) more intricate meridional sections that would be invalid for Bladegen to generate a blade design due to the mathematical calculations required for the blade angles etc. This is detailed a little more in the Bladegen Help, if you add the following to an Index search - Meridional Profile or Meridional Trim Profile.





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