Expert: Paul Soderman - 5/31/2011

Question
What is the most efficient blade design for a Vane Axial fan?

Answer
The short answer is one with the highest lift to drag ratio.  The long answer requires a fan design analysis based on the aerodynamic environment and desired performance.  The airfoil leading edge and trailing edges should align with the local flow, and the camber and thickness distribution should achieve the desired lift and drag.  Cascade effects must be taken into account. Twist and taper must be included. In other words, one cannot say what the most efficient design is in general because each flow environment and design goal require a system analysis that will lead to a different blade design. In fact, different assumptions and design strategies can lead to different designs. I can recommend Maria Pascu:  Axial Fan Design, VDM Verlag for design strategies, but it is a somewhat advanced book. Pacu describes the Cordier diagram, which is often used to define the maximum achievable performance of a specified class of flow machines.  Designing a fan blade to place high on the diagram is the challenge.  Cordier shows experimental data from a fan designed according to her preferred strategy that does very well.
Paul

p.s.  I should have said Pascu shows experimental data...