Fluids

Fluids

How does Bladegen measure the blade angle (beta)? (reference axis?)

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    • JoaoAlex
      Subscriber

      Hello folks,

      I´ve been simulating turbomachinery flow (like radial turbines and pumps) using the ANSYS tools (Bladegen, DesignModeler, CFX, Turbogrid, ...)

      I still can not understand how Bladegen or DM measure the blade angle or so-called beta. To create a general impeller geometry in Bladegen it's necessary to input the meridional profile, blade angle distribution, and thickness distribution along the blade, so the program outputs the 3D geometry.

      How is the beta angle defined in this 2D coordinate system, named "blade-to-blade view"? (when it positive, negative?) I´ve read that the beta is defined in the M' vs theta, how does this 2D coordinate system relate to the real space (x, y, z) or its equivalent (r, theta, z) space? is there a conformational transformation preserving angles?

    • rfblumen
      Ansys Employee
      Hi Joaolex Starting with (x,y,z), we want to convert to cylindrical coordinates (r,theta,z) where r=sqrt(x^2+y^2) and theta=atan(y/x)

      We then define developed coordinates (m,s) where m=meridional coordinate and s=integrated arc length
      m=integral(sqrt(dz^2+dr^2)) and s=integral(r*dtheta)

      The blade angle beta is defined along the mean camber line with respect to the developed view in (m,s) coordinates where:
      beta=atan(ds/dm) where beta is with respect to the streamwise direction or beta=atan(dm/ds) where beta is defined with respect to the circumferential direction.

      When trying to display multiple blade passage together in the developed view using (m,s) coordinates, the neighboring blades will appear distorted for blades that are not purely axial (i.e. have a varying radius). To overcome this, the developed coordinates (m,s) are normalized by r: m'=m/r, s'=s/r which gives the normalized developed coordinates (m',theta)
    • JoaoAlex
      Subscriber
      Thanks a lot, !!!!
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