Design of Fan for Turbofan engine

[Johnny99]

I currently doing by final project about designing fan for turbofan engine.After discussing with my lecturer,I decided to do it based on axial compressor preliminary design method in Gas Turbine Theory : G. F. C. Rogers, H. I. H. Saravanamuttoo, Henry Cohen book.Now after following the design method,I'm stucked at determining the pitch to chord ratio for five points from hub to tip.According to the book,it is determined from the graph Air deflection versus air outlet angle in Fig 5.14 pp139 but i got the air deflection beyond the the value of the air deflection in the graph.I tried searching for the bigger graph but no luck.

Your helps is very appreciated.

 

[Johnny99]

anyone? at least give some reference to design the fan ..I 'm really confused right now finding suitable design method for this..please help me...

 

[Pattonias]

As a turbine mechanic I can say that having a even number of blades would be greatly appreciated. This make repairs and balancing much easier. This probably doesn't help at all.

 

[minger]

That's kind of funny, because as a turbomachinery engineer, we prefer to have the number of blades odd and prime if possible.

 

[Johnny99]

Thanks for reply guys although it seems not related to my question.At first I followed McKenzie method to determine the pitch chord ratio but I got weird blade shape.It has very small chord at hub and very large at mean radius and become smaller at tip.I end up assuming pitch to chord ratio is equal to 1 from hub to tip.so now I got blade chord increase from hub to tip.As for what you guys discussed,from my reading,for rotor ,it is preferred to have odd and prime number of blade to avoid resonance while in stator it is preferred for it to be even.Now I got new problem on how to draw my blade and do cfd analysis for it using ansys cfx.I tried googling but there are not enough guide for it.I tried using ansys bladegen software but not quite understand how can I draw naca profile blade and vary the inlet and outlet angle for it from hub to tip.Any guide for this subject is really appreciated.

 

[Pattonias]

Thanks for reply guys although it seems not related to my question.At first I followed McKenzie method to determine the pitch chord ratio but I got weird blade shape.It has very small chord at hub and very large at mean radius and become smaller at tip.I end up assuming pitch to chord ratio is equal to 1 from hub to tip.so now I got blade chord increase from hub to tip.As for what you guys discussed,from my reading,for rotor ,it is preferred to have odd and prime number of blade to avoid resonance while in stator it is preferred for it to be even.Now I got new problem on how to draw my blade and do cfd analysis for it using ansys cfx.I tried googling but there are not enough guide for it.I tried using ansys bladegen software but not quite understand how can I draw naca profile blade and vary the inlet and outlet angle for it from hub to tip.Any guide for this subject is really appreciated.

Really, I didn't know that there is was a reason for the odd number of blades. I know that the GE engines that the Army uses have an even number of blades to ease repairs when a blade is chipped or worn. (You only have to file the blade on the opposite side to balance as opposed to balancing all the blades.) I imagine I'll learn more about this in my future studies. Good luck with your work. I hope it goes well.