# Pitch and frame change

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 June 8, 2010, 09:12 Pitch and frame change #1 New Member   Andy Good Join Date: Jul 2009 Posts: 11 Rep Power: 10 Sponsored Links Hi all, Just a quick question. I'm simulating a rotor and the CFX literature often refers to pitch change and frame change at the interface between rotor and stator. I roughly undestand the principle but I don't really see a difference in the two. Could someone explain them for me as I can't find a definition anywhere? Many thanks, Andy

 July 7, 2010, 08:52 #2 New Member   Join Date: May 2010 Posts: 24 Rep Power: 9 Also you have made this post nearly one month ago I will give you an answer: A Frame Change occurs when you change the speed of rotation (for example from 310 rad/s to 0 rad/s -> Rotor - Stator). A change of speed from 310 to 155 rad/s is another example. In CFX you can do such a frame change with a Stage or with a Frozen Rotor Interface. Pitch change is necessary if the number of blade is different. Example: 4 blades in rotor, 5 blades in diffusor. The pitch change describes the ratio between those different numbers (in this example 0.8).

 July 7, 2010, 08:55 #3 New Member   Andy Good Join Date: Jul 2009 Posts: 11 Rep Power: 10 Thanks for that. That makes much more sense now.. Just to clarify, is Frame Change for the two domains at a point in time (ie stator is stationary @ 0rad/s while the rotor is rotating at 310rad/s) or for when the relative rotational speed changes in time (ie, relative rotation between rotor and stator is 310rad/s and then changes to 0rad/s)? I think its the first option but I just want to be clear. Last edited by Andy QUB; July 7, 2010 at 09:11. Reason: Extra question to ask.

 July 8, 2010, 03:41 #4 New Member   Join Date: May 2010 Posts: 24 Rep Power: 9 Frame Change is for one point in time. Your first assumption is correct. Your second example (reduction of rotational speed from 310 rad/s to 0 rad/s) requires a transient simulation. Therefore you can nevertheless use a frozen rotor interface (as far as i know). In this way both of your assumptions should be correct (the first one is to 100% correct, for the second assumption I'm not 100% sure). Last edited by Max Efficiency; July 8, 2010 at 03:44. Reason: added last sentence

 July 8, 2010, 05:10 #5 New Member   Andy Good Join Date: Jul 2009 Posts: 11 Rep Power: 10 Great, thanks..

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