Unified Engineering                                                                        Spring Term 2005

 

Problem P9. (Propulsion) L.O. G

 

Two rows of turbomachine blades are shown below.  At inlet to the first blade row, the flow is purely axial.  Assume that the axial component of velocity (w) then remains constant through the stage.

 

wr
 
Text Box: 55oText Box: 75oFile written by Adobe Photoshop¨ 5.0

 

 

a) Neatly draw and label the velocity triangles assuming the blade speed wr = 2w, where w =100 m/s is the axial velocity.

 

b) On which blade row(s) is there a torque applied?   Why?  In what direction does it act?

 

c) Write an expression for the power extracted by each blade row.  Is this a compressor or a turbine?  How do you know?

 

d) Draw the velocity triangles for a blade speed of 3w.  Assuming the flow is well behaved, does the power per unit mass flow increase or decrease and by how much (percent change)?  What aerodynamic problems might be encountered at this condition?